...... - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

SECTION 1 -GENERAL

1-1 INTRODUCTION block diagram, to determine what specific functions, The information contained in this handbook is if impaired, would result in the symptoms noted. based on data obtained from Navy publications such 3. Finally the specific components, which if as the Electronics Information Bulletin (EIB), Naval failed could result in the impairment of the function Ship Systems Technical News (Formerly BUSHIPS noted, should be listed. Journal), and other approved publications. The Many technicians need no instruction to perform Communications Handbook is the first of a series of these steps, but an outline of the preliminary trouble­ equipment-oriented handbooks which comprise the shooting steps will be useful to the less experienced Electronics Installation and Maintenance Book (EIMB) technician. series. More specific troubleshooting procedures are then used to identify the failed component. These, a. PURPOSE too, might be performed by the experienced technician The purpose of this handbook is to provide without specific instructions, but the troubleshooting Naval personnel with information which will aid in procedures given will be useful to less experienced the installation, maintenance, and repair of all types technicians. The use of these techniques will save of radio, radio communications, and associated time and money, improved equipment conditions, and equipments. The material in this handbook is in improbe technical competance. support of information contained in equipment tech­ nical manuals; it provides subordinate policies, and d. SAFETY installation and maintenance standards for radio, Hazards encountered in servicing electronic radio communications, and associated equipments. equipment and the precautions to be taken against them are covered thoroughly in electronic technicians b. SCOPE training courses and the General Handbook (NA VSHIPS The Communications Handbook is arranged in 09 67-000- 0100) of the EIMB series. These sources five sections: Section 1 - General; Section 2 - should be referred to in case of any doubt about safety Circuit Applications; Section 3 - Field Change Iden­ precautions to be observed in troubleshooting. tification Guide (FCIG); Section 4 - Service Notes; Observance of safety precautions will help keep and Section 5 - Reference Data. equipment operating, help your career in the Navy, The material in Section 1 pertains to general and possibly determine whether you survive. Follow information which is not peculiar to one type of them! communication equipment. The information includes general data on all forms of units used for radio e. RECOMMENDED ADDITIONAL READING communications, such as amplifiers, antennas, In or.der to keep this volume within reasonable receivers, transmitters, power supplies, remote size, it is not possible to include a wealth of detail that control units, and so on. A description of the basic can be valuable to the technician or operator. There­ principles of operation is given to assist in the appli­ fore it is recommended that the general subject matter cation of troubleshooting procedures. In addition, a covered herein be supplemented with additional publi­ preliminary outline is given for use in checking the cations. Suggested supplementary references include: more easily overlooked causes of trouble, and to Single Sideband Communications NAVSHIPS determine the general area in which the malfunction 09 67-307-7010 is located. Emissions and Bandwidth Handbook NAVSHIPS Section 2 provides information which describes 0967-308-0010 electronic circuits employed in all types of communi­ Principles of Telegraphy (Teletypewriter) cations equipment, and will support information con­ NAVSHIPS 0967-225-0010 tained in equipment technical manuals. Principles of Modems NAVSillPS 0967-291-6010 Section 3 provides a current list of field changes Fundamentals of Single Sideband NA VSHIPS together with information enabling technical personnel 0967-222-2010 to determine by inspection the applicable field changes that have been accomplished. 1-2 TYPES OF EMISSIONS Section 4 contains service notes of specific Intelligent operation and servicing of communi­ equipment. cation equipment depends to a large extent on under­ Section 5. This section is under preparation. standing the types of radio emissions used. AM and When completed, it will contain data applicable to FM emissions are tabulated in Table 1-1; the communications equipment. commonly-used AM and FM emissions are described in the following subsections. c. TROUBLESHOOTING The electronics technician is urged to analyze a. AMPLITUDE MODULATION each failure to determine its possible causes before A continuous, unmodulated, fixed-frequency attempting to repair a malfunctioning equipment. This radio signal (A0 emission) carries no modulation step, which shol)ld precede removal of the equipment which conveys information. A signal must be modu­ from its cabinet, includes the following: lated by another frequency or waveform in order to 1. Equipment operation should be tested in all convey information. modes and with the use of all functions to permit the malfunction to be described completely. 2. The performance data obtained should be I analyzed, with the use of the equipment schematic or .-'

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

TABLE 1-1. TYPES OF RADIO EMISSIONS

AM FM MODULATION

A0 F0 No modulation intended to carry intelligence.

Al Fl On-off or mark-space keying without the use of a modulating tone.

A2 F2 On-off or mark-space keying of a modulating audio frequency, or of the modulated emission.

A3 F3 Voice-frequency modulating, including simplex AFTS RATT.

A3A Single-sideband, reduced carrier (SSB).

A3B Two independent sidebands (ISB).

A3H Single-sideband, full carrier (compatible SSB).

A3J Single-sideband, suppressed carrier (SSSC).

A4 F4 Facsimile, with modulation of main carrier directly or by a frequency-modulated subcarrier.

A4A Facsimile using single-sideband, reduced carrier.

A5 F5 Television.

A5C Television, vestigial sideband.

F6 Four-frequency diplex telegraphy (RFCS RATT).

A7 Multi-channel voice-frequency telegraphy (AFTS MUX).

A7A Multi-channel voice-frequency telegraphy (AFTS MUX) using single-sideband, reduced carrier.

A7B Multi-channel voice-frequency telegraphy (AFTS MUX) using two independent sidebands.

A7J Multi-channel voice-frequency telegraphy (AFTS MUX) using single-sideband, suppressed carrier.

A9 F9 Cases not covered by above (e. g., a combination of telephony and telegraphy).

A9B Combinations using two independent sidebands.

In CW communication (AI emission) a carrier emissions. That is why some transmitters must be is present only during key-down intervals, as shown in a "voice" or "A3" mode when they are to be am­ in Figure 1-1. Turning the carrier on and off in plitude-modulated by an AN/SGC-lA, AN/UCC-1 or accordance with telegraphic characters is a form of other AFTS tele-type terminal unit. Military A3 amplitude modulation. Manually-keyed CW emission emissions are normally limited to 6A3 (6 kHz band­ is designated 0. lAl, which means that its bandwidth width) to conserve spectrum, but high-quality AM (resulting from modulation) does not exceed 0. 1 kHz. broadcast emissions may use l6A3 for higher fidelity. Such an emission requires a higher degree of operator A4 emissions (nominally 5. 450A 4) are those skill to recover the message content, but uses less which transmit picture elements by a slow-scan pro­ spectrum space, employs simpler equipment, and is cess. It is commonly called facsimile. By using a capable of reliable reception over greater distances slow scan rate, its bandwidth can be confined to 5. 450 (or under more adverse conditions) than other types kHz, a range which can be handled by the same trans­ of emission. mitters and receivers used for A3. A2 emissions (MCW or keyed audio-modulated A5 emissions are those which transmit picture CW) are those signals which are modulated with a elements by a fast scan process as in television. The single audio tone. Such emissions are seldom used fast scan process calls for bandwidths as great as for communication purposes in this modern age, but 6000 kHz (6000A5), which require transmitters and are often encountered in radio aids to navigation. receivers having such a passband capability. A 3 emissions are those which use more than A 7 emissions are those which are amplitude­ one modulating audio tone to carry one channel of modulated by multiple channels of audio frequency intelligence. Voice or "phone" transmissions use tones, and are commonly called "multiplex. " For this type of emission. A3 is also used to designate teletype, A7 consists of multiple audio frequency sub­ single-channel audio frequency tone shift (AFTS) tele­ carriers or sidepands which are shifted in frequency type and some types of multiple-t one remote control in accordance with the keying intelligence.

ORIGINAL 1-2 . .

- , ,- ,-

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

/"', /"', n r n n u v u v v v v v v v v v v

A� EMISSION DAH Dl DAH A EMISSION a. c. 2 STEADY CAR RIER AII.PLITUDE

NO INFOR MATION b. A I EMISSION- CODED IN TERVALS MODULATED

Figure 1-l. RF Waveforms

By international agreement, the various ty pes you to understand "sideband" relationships and modu­ of emission are assigned the designations given in lation techniques, and consequently the test and ad­ Table 1-l. A designation may be preceded by a num­ justment procedures required. merical value which indicates its necessary band ­ To understand amplitude modulation, you must width in kilohertz. first know what a CW signal is like. It should be Optimum communication effectiveness is apparent that an unmodulated carrier and a CW signal achieved when received passband matches the band­ with the key held down are the same thing, namely, width of the emitted signal. For example, 6A 3 voice AO emissions. On a paroramic receiver or spectrum emission is best received on a receiver having a analyzer they look the same, and any test you can 6 kHz passband 9plus a small fudge-factor for fre­ make of them will give the same result. Further­ quency error). A greater receiver passband admits more, if they are stable they take up no room in the more noise, but no more signal because the signal spectrum. If you tune in such a signal on a receiver occuplies only 6 kHz in the first place. Therefore a with the BFO on, you can hear it over several dial greater receiver passband can only degrade the divisions and the receiver input or output meter will receiver signal-to-noise ratio. Too little receiver give a reading over several dial divisions. But nei­ passband will also degrade the received signal ther of these effects proves that the signal is broad - because of sideband clipping in the receiver. Many it only indicates that your receiver doesn't have infi ­ modern receivers have provisions for selecting a nite selectivity. By definition, 4040.000 kHz and bandwidth which will approximately match that of 4040.010 kHz are not the same frequency, so they the signal which it is to receive. must be different. Actually, they differ by 10 Hz, Some receivers, particularly UHF, employ a and a receiver or other device that could separate passband greater than that required by modulation signals 1OHz apart could separate these two. sidebands because of difficulty in holding transmitters All this leads us to the first step in visualizing and receivers on an exact frequency, even with crystal modulated signals. Any single RF source can be re­ control. Such receivers represent a compromise in presented by an infinitely-thin vertical line on a plot which signal-to-noise ratio is traded off against fre­ of amplitude versus frequency. Figure 1-2 is such a quency tolerance. The modern trend is toward tight­ representation, except that we had to settle for a ened frequency tolerances which, among other things, finite-thickness line. The frequency can be read from permits a reduction of receiver passband and conse­ the "Frequency" scale, and the amplitude from the quent improvement in receiver sensitivity. "Amplitude" scale. The taller the line, the greater (!) Understanding Amplitude Modulation the amplitude. Don't worry about the units - the Having a clear concept of a modulated sig­ frequency scale could be megahertz or even hertz. nal is the first step in understanding what single side­ Your paroramic receiver would show such a picture band is all about. The usual description of amplitude­ if it had infinite selectively. If you had a receiver or modulated telephony with its "modulation envelopes" frequency-selective voltmeter with such selectivity, and "percentages of modulation" doesn't prepare you its input or output meter would indicate the amplitude for full understanding. The conventional explanation at one setting of the tuning knob as you tuned across of AM makes it practically impossible to form a men­ the frequency range shown, and nothing at any other tal picture of "suppressed carrier, " or "single side­ setting. band, " or even plain CW. It is hoped that this expla­ nation will present a picture that will make it easy for

ORIGINAL 1-3 I'

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Amplitude Amplitude

- 1000 f +I 000 Frequency Frequency

Figure 1-2. A Representation of a Single Radio Frequency Figure l-4. A Representation of Two Weak Radio Signals (2) Effect of Two Signals Suppose now that we wish to transmit intelli­ "Ah, yes," you say, "But what about the 2000 gence consisting of a simple I 000Hz tone. One way to do Hz beat between the two outside frequencies? They're it would be to set up another transmitter on a frequency separated by 2000 Hz, and you will get a beat between exactly 1000Hz removed from the first frequency. It them. " could be higher or lower in frequency -it wouldn't mat­ Right you are. Except for one special case ter so long as the separation was exactly I 000Hz. The where the proper phase relationships exist, this 2000 passband of a practical receiver -one that doesn't have Hz beat 'NOUld show up. But the spurious effect is minimized when the center signal is made large in infinite selectivity -would admit both signals simultan­ proportion to the other signals. Thus, if we didn't eously when tuned to or near the correct frequency, and wish to introduce some extraneous or false intelligence the audio output of the receiver would be the I 000 Hz at the receiver, we would have to hold the phase re­ beat between the two signals. This is hardly a difficult lationships exactly right, or keep the amplitude of the !thing to understand; you don't have to operate long in a center signal large with respect to the others. congested part of the spectrum before you encounter Obviously, using three transmitters to transmit "heterodyne QRM" which is exactly the same thing. this 1000Hz intelligence is doing things the hard way, Such a signal can be represented as the drawing in and fortunately it isn't necessary. All we have to do Figure 1-3. at the transmitter, which we will assume is generat­ ing a single signal as shown in Figure 1- 2, is to beat (or "mix" or "modulate") this signal with a 1000 Hz signal. As in any beating or mixing or modulating or heterodyning process, the output consists of the origi­ nal two signals, the sum frequencies, and the differ­ ence frequencies. Because the original 1000Hz audio tone isn't R-F, it won't be radiated, but the others Amplitude will be. The resultant signal is exactly the same as the one we got in Figure 1- 4 using three separate transmitters. Being the same signal, jt gives the same result in a receiver. And, fortunately, the phase relationships are right to eliminate the spuri­ ous 2 000 Hz beat mentioned earlier, When you mix signals like this in an AM transmitter, you call it -1000 +1000 "modulating. " But when you do the same thing in a Frequency receiver, you call it "demodulating" or "heterodyning" or "detecting" or ''beating" or "mixing. n Let's use the work "modulate" from now on, remembering that Figure 1- 3. Two Radio Signals the two signals modulate each other, and that we run into trouble if the "carrier" being modulated isn't In Figure 1-3, the alternative signal which large compared to the modulating signal. would also ve a I 000Hz beat is shown as a dashed gi At the start, we said that you had to understand line. If we used three transmitters separated as the nature of a CW signal to follow this discussion. shown in Figure 1-4, we would still be transmitting Let's see why this is so. Suppose, for some reason, 1000 Hz intelligence. All signals removed 1000 Hz that the sole purpose of radio communication was to from the center frequency give I 000 Hz beats in the transmit a 1000Hz tone. Obviously we could do it in receiver, producing audio output of 1000Hz, the the manners just described, either by setting up three intelligence we are transmitting. transmitters properly phased, or by modulating the

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

output from a single transmitter with 1000 Hz of audio. plete AM signal consists of a steady carrier and Sooner or later someone would come up with the idea the two sidebands. The individual side frequencies that it isn't necessary to transmit the three signals of in the sidebands are determined by the complex com­ Figure 1-4. Instead, you could transmit a single ponents that exist in the audio modulating signal at signal as in Figure 1-2 and incorporate a to-be­ the instant under consideration. In an AM transmitter modulated signal in the receiver. In order to receive the aduio frequencies modulate ("beat against" or "are only 1000. Hz intelligence, this to-be-modulated signal mixed with") the carrier in the modulated stage and would be set 1000 Hz higher or lower than the trans­ thereby generate corresponding side frequencies. You mitted signaL Every time the transmitter was turned would be just as correct, if not more so, to call the on, we would get the 1000 Hz tone. That is exactly modulator an "audio power amplifier" and the modu­ what we do in CW communication circuits. In every lated amplifier a "mixer" (as you would in a receiver). respect we would have the same communicating abil­ (4) Carriers and Sidebands ity that we had when the signal of Figure 1-4 was Now let's tie in these concepts to the side­ applied to a receiver which had no to-be-modulated band problem. The signal that all the other signals signaL modulate is called the "carrier." This signal merely Note that if the to-be-modulated signal does furnishes a reference frequency and doesn't otherwise not maintain an exact 1000 Hz displacement in fre­ "carry" anything. Because the "carrier" conveys no quency, a different audio beat will be produced. Or intelligence, it doesn't have to be transmitted and if it is not present at all, we get no tone. For CW might very well be supplied at the receiver. The operation, the receiving operator selects the tone, signal generated locally in a SW receiver is called and the transmitting operator superimposes further the "beat frequency oscillator" even though it does intelligence in the form of a code made up of short exactly the same thing as a transmitted carrier and and long signals and spaces. If we are to aviod beats could be called a "local carrier." between two or more different signals present in the The intelligence i.s contained in the smaller receiver passband, the local signal must have a much signals and is recovered by beating or heterodyning greater amplitude than the incoming signals, just as them against the carrier (either transmitted or gen­ in the three-signal case described earlier. erated locally in the receiver). These smaller signals (3) Complex Modulation are called "side frequencies, " and a band of them It should be obvious that we don't have to would be called a "sideband." confine ourselves to 1000Hz tones. The modulating In a communication system based on the modu­ signal might well be a complex signal made up of lation of a large signal by a smaller one, the ampli­ different frequencies. For example, if our purpose tude of the aduio output from the receiver is propor­ were to transmit simultaneously a 2500 Hz tone and tional to the amplitude of the side frequencies. The a 1000 Hz tone of greater amplitude, we could set up frequency or audio pitch of the output is determined five transmitters as shown in Figure 1-5, with care­ by the beat between the side frequencies and the ful control of the relative phases so as not to have carrier. some 1500-Hz, 2000-Hz, 3500-Hz, and 5000-Hz In the modulated stage, the carrier amplitude signals in the receiver output. Or we could modulate must always be at least twice the sum of the instan­ the carrier with the 1000-Hz and 2500-Hz signals and taneous (opposite) amplitudes of all the modulating get exactly the same effect at the receiver. In each frequencies, or overmodulation will occur. This case, we must make sure that the amplitude of the means that, for a transmitter having 1000-watl car­ carrier being modulated is large compared to the rier power for example, not more than 500 watts of total power of all the modulating frequencies. Other­ downward modulating audio can be applied, and that wise, the unwanted beats, plus other distortion pro­ the transmitter must be capable of I 500 watts of up­ ducts, will appear. ward peak power. Therefore, a 1500-watt peak capa­ bility is needed to achieve 100o/o modulation, of which only 500 watts peak is usable intelligence.

· Speech waveforms are characterized by occa­ sional peaks which rise to an amplitude many times the average level. Statistically speaking, speech waveform peaks exceed 13 dB above the average level lo/o of the time. However, effective speech power can Amplitude be approximated by sine wave modulation at 30o/o, which is why a 30o/o modulated signal is used for re­ ceiver test purposes. Each sideband contains half the total modulating power which, for a 1000-watt carrier modulated 30o/o, is only 75 watts of usable intelligence per sideband. The carrier continues at -2500 -1000 +1000 +2500 its full power even when no information is being trans­ mitted, such as during pauses between words and Fcequency sentences. (ElB 623, 734) (5) Single Sideband Transmission and Reception Inasmuch as the carrier conveys no intel­ Figure 1-5. A Representation of Five Radio Signals ligence, it is possible to dispense with it at the trans­ mitter and introduce it at the receiver instead. This Speech and music are more complex than just will save transmitter power and reduce heterodyne two tones, but the principle is identicaL The com- QRM. If both sidebands are received at the detector

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in which a carrier is reintroduced, the inserted Forget about carriers transporting audio and all the carrier must have exactly the correct phase relation­ other misconceptions. Visualize the audio signal ships with the sidebands if distortion is to be avoided. modulating the carrier to generate sidebands, and However, if only one sideband (or two independent, (at the receiver) the sidebands modulating the carrier unrelated sidebands) is present at the detector, there to produce the audio signal, and it should all begin to is no need for an exact phase relationship and there make sense. For mental exercise, visualize what can be some frequency error without destroying in­ happens when you remove the carrier during trans­ telligibility. Two identical sidebands are not mission and reinsert it at the receiver, or lop off needed to convey intelligence, and the extra sideband one of the sidebands at the transmitter or the receiver. can be removed either at the transmitter or at the It will all add up easily when you know what "really" receiver - one is single-sideband transmission and happens. the other is single- sideband reception. When the carrier is eliminated at the trans­ b. FREQUENCY MODULATION mitter and reinserted at the receiver, its frequency Frequency modulation (FM) refers to a method must be set carefully. For example, if there is of modulating an electromagnetic wave by varying its 100 Hz of cumulative frequency error in the several frequency in accordance with the intelligence to be receiver oscillators, there would be an error of 100 transmitted. It is a form of angle modulation in Hz in the received audio signals. This is of no im­ which the angular velocity of the wave is made to portance in radiotelegraphy, but receiver tuning for vary according to variations in the modulating signal. a single-sideband suppressed-carrier (SSSC ) voice The FM signal analogous to on-off keyed CW is or teletype signal is quite critical. There are elec­ called radio frequency carrier shift (RFCS) or fre­ tronic means for simplifying the tuning, provided a quency shift keying (FSK). Figure 1-6 shows an RF weak carrier is transmitted to give a clue to the exact waveform which changes abruptly in frequency while setting of the carrier at the receiver. Because the remaining constant in amplitude. This frequency­ receiver must be carefully synchronized in frequency modulation technique is known as Fl emission (see with the transmitter it is to receive, precision fre­ Table 1-1) in which the frequency is changed between quency control of both is needed. two discrete values by opening and closing a keying If insufficient carrier is supplied at the trans­ circuit. mitter during the modulation process, extra signals An RF emission that is frequency modulated by will be generated and radiated in the form of over­ a single audio tone will produce F 2 emission (see modulation and splatter. However, once the modu­ Table 1-1). The modulating components and the lation (heterodyning) process has been completed, frequency-modulated RF output are show n in Figure the carrier has served its purpose and can be attenu­ 1-7. Increasing the frequency of the audio modulating ated, as in A3A emission, or eliminated entirely, as signal will increase the number of times per second in A3J emission. If insufficient carrier is supplied that the modulated radio frequency pa sses through at the receiver, extra signals will also be generated the center frequency. The effect of increasing the and heard. amplitude of the modulating signal is to increase the Single-sideband techniques permit substantial frequency deviation without affecting the number of savings in transmitter costs, size, and power con­ frequency excursions per second. sumption for a given information-carrying power. Frequency modulation by a complex modulating Thiuk of that 15 00-watt (peak) transmitting capability wave as in voice or single-channel ( 2 alternate tones) we needed to transmit only 75 watts (average) per RATT produces F 3 emission. This type and other sideband when we used 6A 3. By eliminating or great­ even more complex waveforms are listed in Table l-1. ly attenuating the carrier, and emitting sideband en­ Any complex modulating wave can be analyzed into a ergy only when a modulating signal is present, we series of sine waves of varying amplitude and can deliver the same communication effectiveness frequencies. with a much smaller transmitter. 3A3A and 3A3J In FM, the instantaneous frequency of the radio emissions occupy half the spectrum space of conven­ frequency wave is varied in accordance with the modu­ tional 6A 3 emission, relieving crowding and inter­ lating signal, while the amplitude of the emission is ference in the radio spectrum. Not only that, but kept constant. The number of times per second that receiver passband need be only half as wide, produc ­ the instantaneous frequency is varied from the aver­ ing a corresponding improvement in signal-noise age (carrier frequency) is controlled by the frequency ratio... Alternatively, two independent sidebands of the modulating signal, and the amount by which the (6A3If) can be emitted in the same 6 kHz spectrum frequency departs from the average is controlled by space but with a greater message content compared the amplitude of the modulating signal. The amount to conventional 6A 3 in which both sidebands carry of variation is called the frequency deviation of the the sam� message. FM wave. We can now discover why we are likely to be The frequency spectrum of FM is considerably misled by the "modulation envelope" illustrations different from that of AM. In the latter, the practi­ often used to depict AM. These drawings or scope cal spectrum is equal to the highest modulating fre­ patterns actually show the combined effect of several quency for single-sideband and twice that value for separate frequencies (three in our example of Figure double-sideband. In frequency modulation, this is 1-3) which, because of selectivity problems, are not not the case. For each modulating frequency there easily separated into individual components. An un­ are an infinite number of sidebands. For instance, derstanding of the whole picture develops when we with a 500 Hz sinusoid modulating a carrier, the examine the signal with a spectrum analyzer or fre­ modulated wave contains the carrier, a pair of first­ quency selective voltmeter of sufficient selectivity. order sidebands 500 Hz either side of the carrier, Think of modulation, beats, heterodyning, mix­ a pair of second-order sidebands located 2 X 500 Hz ing, and AM detection as exactly the same thing. or 1000 Hz either side of the carrier, a pair of

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COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

FREQUENCY SHIFTPOINTS

+MAX

� 0 ::::> ,_ ....J 0 c.. :K ...:

-MAX

.. fl ......

Figure 1-6. Fl Waveform (Frequency-Shift Keyed)

third-order sidebands at !1500Hz, etc. Their When a frequency modulated signal is passed relative amplitudes are a function of the modulation through a frequency doubler or other frequency multi­ indix. Because .the modulation index varies with the plying amplifier, the effect is to increase the modu­ amplitude of modulating wave, the amplitudes of lation index by a factor equal to the frequency multi ­ the various sidebands will vary. plication involved. No distortion is introduced by Inasmuch as the amplitude of the FM envelope the mere fact of multiplication, however. If, by is unchanged by modulation, the total power in the heterodyne action as in a receiver, the FM wave is carrier and the sidebands is equal to the power of translated to a new portion of the spectrum, the the unmodulated carrier. The term "occupied band­ modulation index and the bandwidth are unchanged. width" refers to the width of the spectrum within FM systems are of two types, wideband and which 99"/o of the total power falls. For certain values narrowband, and the selection of one over the other of modulation index, the carrier amplitude becomes depends upon the use to which it is to be put. With zero and the entire FM wave consists of sidebands a large deviation (wideband FM), circuit and antenna of various orders. A useful rule is that an FM wave noises which are weaker than the desired signal are contains sidebands of importance on either side of nore completely suppressed than in the narrowband the carrier wave over a frequency band approximat­ ;ystems. However, the frequency spectrum over ing the sum of the frequency deviation plus the modu­ vhich the noise is accepted by the receiver is also lating frequency. The "necessary bandwidth" in ;reater. For multichannel systems such as micro ­ which most of the energy of the wave is contained is Nave, TACSAT, and tropospheric scatter, the de­ then twice this value. The various frequencies with­ viation may be made great enough to accomodate the in this band will be spaced at intervals that are equal maximum bandwidth desired. to the modulating frequency. and so will be closer to­ The greater bandwidth requirements of FM as gether at low modulating frequencies than at high. compared to AM makes it impractical to assign Adding frequencies to the modulating wave does not wideband FM channels below the VHF region of the necessarily increase the modulation index; rather it electromagnetic spectrum; that is, below about 70 increases the number of spectrum lines in the FM MHz. However, there are many narrowband FM sidebands. services such as RFCS, and even narrowband FM The bandwidth assigned for FM must be great voice, at lower frequencies. The only bar to the enough to allow a reasonably high modulation index use of FM at any frequency is bandwidth that can be at the highest modulation frequency. When the modu­ accomodated, as by an antenna for example, or by lating signal is composed of more than one sinusoid, neighboring services which must share the spectrum. as in voice or RATT, the determination of the spec­ Many public and government sen·ices that pre­ trum becomes very difficult because the modulation viously operated wideband FM in the frequency range of the carrier by one sinusoid is not independent of of 25-70 MHz are now being required to change over the modulation of the carrier by other frequencies. to narrowband FM. This includes the military. The Sidebands are generated at frequencies correspond­ older SCR-608, AN/SRC-10, 11, 12, etc., equipments, ing to the sum and difference of each modulating many of which are still in use, are wideband FM and frequency, plus its harmonics and the intermodulation therefore they have difficulty in netting with the newer products with all other modulating frequencies and narrowband equipments such as the AN/VRC-46. their harmonics. While a wideband receiver can process a narrowband

ORIGINAL 1-7 / ......

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

fmin f max f max (fo-foud) Uo + foud) J J � �

-MAX t t A. FREQUENCY- MODULATION BY f aud I fo fo fo fo fo ·� r r i t AMPLITUDE �� � � """

B. MODULATING FREQUENCY f aud

C. FREQUENCY- MODULATION BY 2 f a.ud

AMPLITUDE

D. MODULATING FREQUENCY 2 f aud

Figure 1-7. F2 Waveform (Frequency-Modulated by a Single Audio Frequency)

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COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

signal with results no worse than reduction of effec­ distortion, and by the time the signal is 20 Hz off fre­ tiveness, the converse is not true. A wideband quency, bias distortion would render the circuit unus­ signal into a narrowband receiver will be received as able even with near-perfect signal strength. severe distortion. During the aforementioned fleet operation, it was found that, when average bias distortion reached 1-3 THE IMPORTANCE OF FREQUENCY a level of about 25"/o, the peaks of distortion were in ACCURACY excess of 40o/o, resulting in printing errors on the New advancements in communication systems circuit. Additionally, it was found that bias distortion in recent years have provided the fleet with more and on what could be considered good teletype circuits better capabilities. With these new systems, however, was averaging between 10"/o and 15"/o. This would in­ frequency accuracy problems have arisen which often dicate that the margin for additional distortion is only have resulted in poor circuit performance. Frequency about 1 Oo/o. Based on a 1 Oo/o allowable margin of dis­ errors approaching 0. 02o/o (200 Hz per MHz), which tortion, it would appear that there remains a cushion is the legal limit imposed by the ITU Atlantic City of ±8Hz of frequency error. This cushion must be Convention, cannot be tolerated by synchronous shared between four pieces of equipment; the trans­ communication systems such as SSB, ISB, FSK, and mitter, the receiver, and the transmit and receive MUX. Synchronous communication circuits require multiplex terminal units. By the time the multiplex that each transmitter and each receiver in a circuit terminal units take their allocated share of this toler­ be synchronized in frequency to a high degree of ance, only 4 Hz remain to be shared between the trans­ accuracy. For single sideband voice circuits, fre­ mitter and the receiver. quency accuracies as high as one part in ten million In view of this, some question may arise con­ (1 Hz per ten MHz) are required. Frequency toler­ cerning the manner used to terminate multi -channel ances for multi-channel teletype call for an accuracy teletype circuits. For fleet multi-channel broadcasts, on the order of 0. 1 Hz per 10 MHz. shore facilities are likely to be on the correct fre­ quency within a close tolerance; however, tests show a. EFFECT OF FREQUENCY ERRORS ON that this is not always the case. Shipboard receivers VOICE CIRCUITS used for multi-channel broadcast commonly use sta­ What happens to voice circuit performance in bilized internal reference oscillators to control their the presence of frequency errors? As an example, frequency. If their reference oscillators have been let us consider the measured effects during a recent recently tested, and readjusted where necessary, it fleet operation. The stations of one single-sideband is unlikely that they would have drifted off frequency net were operating with a frequency spread of +200 by any large amount. Therefore, with reasonable Hz. As a result of synchronism errors, voices care, synchronism between transmitting and receiv­ sounded like people either talking from the bottom ing terminals should be possible within the tolerable of a barrel or chirping like birds. frequency error. This 3A3J circuit and 6A3 voice circuit were In order to compensate for frequency errors of given a voice intelligibility test commonly used in shipboard transmitters, an alternative method can be telephone ·circuit analysis. This test measured the used in which the ship transmits a pilot frequency and number of words, which, after being transmitted over the receivers use automatic frequency control to lock a circuit, were confused with words that sound almost onto the transmitted signal. This method works fine the same except for one critical phonetic sound. An except thc.t the circuit becomes more susceptible to articulation index was then derived from this error outage in the presence of poor propagation. This is rate. As compared to an articulation index in excess because the transmitter must use a part of its avail­ of 9 Oo/o for a good telephone circuit, the SSB circuit able power for radiating a carrier which, as previous­ had an index of 35o/o and the 6A3 voice circuit had an ly pointed out, does not contribute to intelligence con­ index of 46o/o. tained in the modulation (except as a frequency refer-­ If the articulation index had dropped below 25o/o ence). Additionally, the capabilities of the receiving due to cumulative personnel, propagation, and fre­ terminal to use frequency diversity to compensate quency error factors, the error rate for sectences for selective fading is degraded, because of the sus­ would have arisen very sharply. In other words, the ceptibility of the receivers that use automatic fre­ SSB circuit had only a 1 Oo/o margin before it became quency control to this same selective fading. critical, as compared to a 21o/o margin for the 6A3 voice circuit. c. EFFECT OF FREQUENCY ERRORS ON These two circuits differed mainly in that a NON-SYNCHRONOUS CIRCUITS frequency error on the SSB circuit translated into a Frequency tolerances of types of communication voice frequency error whereas the 6A3 circuit was not circuits other than synchronous are not as critical, ______u _ •. _affected in the same manner. T):lis means that. if the �se a carrier is tratl.Smitted along with the side­ stations on the SSB net are not synchronized within bands. The emitted carrier bears the correct phase, ±5 Hz of the correct frequency the circuit will be de­ amplitude, and frequency relationship to the sidebands graded, leaving but a small margin for further degra­ (unless disturbed by propagation conditions) so there dation that may be contributed by personnel, propa­ is no requirement for exact synchronization of fre­ gation conditions, and/ or equipment. quency at the receiver. However, the frequency errors observed on circuits during the above­ b. EFFECT OF FREQUENCY ERRORS ON FSK mentioned fleet operation were great. On a 6A3 TELETYPE CIRCUITS amplitude-modulated voice circuit, at least one On multi-channel A 7J teletype, each of the first station had an error of 2 kHz. Of all the stations 5 Hz of frequency error can be translated into 1o/o bias on the circuit, only 70"/o were observed to be within distortion; each of the next 5 Hz would contribute 2o/o 500 Hz of the assigned frequency. This means that

ORIGINAL 1-9 ...... - ... - ... - ... -

COMMUNICATIONS NAVSEA 0967-L P-000- 0010 GENERAL if an R-390/URR receiver were used on this circuit, to ::-1 Hz. If the internal reference oscillators of all the receiver passband would have to be set at I6 kHz, synchronous-communication equipments are checked instead of the proper setting of 8 kHz, if copy of all weekly against the AN/URQ-9 or AN/URQ-10, this stations on the net was to be expected. The increased accuracy can be reached. A better alternative would receiver passband would double the amount of receiver be to use the external frequency standard in place of noise, which would reduce the receiver sensitivity the internal reference oscillator where transmitter (signal-noise ratio) by half, thereby degrading the design permits. receiver signal. The actual degradation might be If the ship uses continuous-tune transmitters even worse because the receiver would then be set a calibrated frequency counter may be used to assdre to receive signals from adjacent channels which might an accuracy between I 0 and I 00 Hz. Higher degrees be in use by other stations. The effect here is that, of accuracy may be achieved by substituting the output unless the receiving station either increases the width of the frequency standard for the internal reference of his receiver passband or retunes his receiver for oscillator of the counter. A frequency counter used those transmissions that were in excess of 500 Hz in this manner should also be employed to check the off frequency, the transmissions would be missed or output frequency of stabilized transmitters to make garbled. sure that alignment errors in the frequency-generating subassembly are not causing an off-frequency con­ d. DETERMINATION OF CORRECT dition. FREQUENCY Synchronous-communication receivers of the Because it is obvious that frequency errors can AN/WRR-2 variety should have their reference oscil­ degrade communication circuits, what can be done ? lators checked weekly. The R-I051/URR receivers The old procedure of zero-beating to the net control that are used on fleet multichannel broadcasts should station is no longer applicable with synchronous­ use the external frequency standard continuously, or communication transmitters. For one thing, not all else be checked every other day against the standard. transmitters are capable of continuous tuning to permit Net control stations should check the transmitted fre­ setting them to the net control station. For another, quencies of all ships in the net, using an R-I05I/URR the net control station can only designate the correct receiver. frequency; he cannot determine it for all bands. The correct frequency throughout the entire f. FREQUENCY SYNTHESIZERS AND military establishment is determined by the U. S. STABILIZED OSCILLATORS Naval Observatory. This correct frequency is given Frequency control for synchronous communi­ to each ship in the form of a frequency standard cations in which the carrier is suppressed is much (AN/URQ-9 or AN/URQ-10) that is periodically cor­ more critical than for those modes of emission in rected by calibration laboratories. Ships do not have which a reference carrier is transmitted. Formerly, the capability, by li stening to WWV, of determining the only a crystal-controlled oscillator could satisfy the correct frequency to the tolerance required. The fre­ frequency accuracy and stability requirements, and quency standard is the only method at present to deter­ extensive sets of crystals were needed to achieve mine the correct alignment of internal reference frequency agility. Today, frequency synthesizers or oscillators of each piece of equipment aboard ship. stabilized oscillators are used to provide the neces­ There is hardly a piece of electronic equipment sary accuracy and stability, and at the same time aboard ship that does not depend upon an accurate provide the wide range of frequency selection of a determination of frequency. The technical manual for variable-frequency oscillator. Generally, due to an equipment may proclaim some fantastic stability, crowded frequency assignments and variations in pro­ but this does not guarantee the frequency accuracy of pagation conditions it is desirable to be able to select the equipment. The frequency stability only states how any frequency in the entire 2-30 MHz frequency range quickly the oscillator will drift off frequency. It is the in increments of 0. I kHz. Without a synthesizer, this nature of all oscillator's, even the most precise, to tuning range would require a set of 280, 000 crystals drift off frequency. As an example, AN /WRT-2 equip­ for the transmitter and an equal number for the receiver. It would be difficult even to find room ments were inspected aboard 40% of the ships partici­ pating in the subj ect fleet operation . Of those inspected, aboard ship for such a set of crystals, and chances 87. 5o/o were incapable of operating within the frequency are that the crystal you needed would be lost anyway. tolerance proclaimed for the transmitter because their The name "frequency synthesizer " sounds com­ internal reference oscillators were off frequency. plica ted, but the general idea is easy to understand. Some of these errors would have resulted in trans­ A frequency syn thesizer is a device which uses a mitted frequency errors of several hundred hertz. single reference oscillator to generate other frequen­ cies. It does this by applying the reference frequency e. EFFECTS OF ALIGNMENT AND ADJUST ­ to dividers and multipliers to develop the required fre­ MENT ERRORS quency steps or increments, and then combining the Errors in the internal oscillators of equipments divider and multiplier outputs in mixer stages to syn­ would not account for frequency errors in the kilohertz thesize the desired output frequency. The frequency range. Errors that large could only be caused by im­ synthesizer employs the beat frequency concept dis­ · proper assigned frequency dial settings, misalignment cussed under Subsection I-2 Types of Emission to of transmitter frequency generation circuits, or by the generate new frequencies. Furthermore, because net mistuning of transmitters when used in their continuous­ operation requires precise synchronization of trans­ tuning mode of operation. As an example, one measure­ mission and reception frequency, it is often a design ment revealed a 7-kHz error between the transmitter practice to use one frequency synthesizer for both frequency output and the transmitter dial indication. transmitter and receiver. There is no reason why each transmitter having A frequency multiplier uses a harmonic gener­ a stabilized internal reference oscillator cannot be set ator which is any nonlinear circuit or device that dis-

ORIGINAL 1-10 ...... - ·,- .. - ..-

COMMUNICATIONS GENERAL NAVSEA 0967-LP-000- 001 0

torts or "squares off" a sine wave input. Harmonics Cause are exact multiples of the basic or fundamental fr e­ Improper alignment of selective filter­ quency. Thus, a nonlinear amplifier rich in second amplifiers. harmonic distortion produces an output which contains Improper count-down in divi der circuits . substantial energy at precisely twice the input or 3. Trouble Point fundamental frequency. Type of harmonic generators Difficulty in achieving pha se lock. include nonlinear amplifiers, diodes, saturable re­ Cause actors, flip-flops, and almost any circuit in which the Insufficient harmonic amplitude into output is not a replica of the input. Filters must be comparator. employed following a harmonic generator in order to 4. Trouble Point select the desired harmonic and to reject the undesired Spurious emission at 1 kHz, 10 kHz, etc . frequencies. Careful alignment of these filter-ampli­ increments from desired frequency. fier circuits is needed to make sure that the proper Cause harmonic is selected and that all others are adequately Improper alignment of selective filter­ suppressed. amplifiers. There are classes of circuits that behave as frequency dividers. Each stage of a binary counter is g. AN/URQ-9 AND AN/URQ- 10 FREQUENCY a "divide by two" circuit; a "nixie" tube provides STANDARDS "divide by ten" capability; and other circuits such as The Frequency Sta ndard AN/URQ-9, and its single-shot multivibrators provide any desired count­ transistorized counterpart-the AN/URQ- 10, are down capability. reference standards intended to pro vide accurate fre­ By mixing combinations of various frequency quency references against which the frequency of multipliers and dividers, practically any output fre­ various frequency generating elements may be com­ quency can be generated from one master crystal pared, or for which the reference signals may be sub­ oscillator. The discussion of Principles of Single­ stituted. Included in the category of frequency gener ­ Sideband Reception under Subsection 1-8, Receivers ating elements are; local oscillators of transmitters contains text and illustrations of a frequency synthe­ and receivers, input drive signals for frequency sizer system capable of tuning to any of a wi de range counters or synthesized signal generators, and refer­ of frequencies in 1-kHz increments. By dividing the ence inputs to e"lectronic clocks and related equipment . 1 kHz increments in a 10:1 divider and adding appro­ It has been determined by personal interview pnate filters and mixers, frequency increments of and written survey with fleet personnel that the use 0. 1 kHz are possible. of the frequency standard is not well understood. It Another form of frequency generator having has also been asc ertained that a high per centage of high stability and accuracy is one which resembles a units now installed in ships ' communications spaces free-running variable frequency oscillator but which are not being properly maintained. in fact is stabilized by being phaselocked with a high­ As indicated by the name reference frequency stability frequency standard. This type of oscillator standard, the AN/URQ-9 and AN/URQ- 10 do not is usually called a stabilized local oscillator (STALO) measure frequency. They are highly stable and or stabilized master oscillator (SMO). In operation, accurate references against which other signal a sample of the oscillator output is compared with sources may be compared. The actual comparison marker frequencies developed from the output of a may ue performed by a technician using a frequency frequency standard. The comparison is made in a deviation meter and possibly an amplifier for one or comparator or phase detector circuit which is a fre­ both of the signals being compared. The comparison quency deviation detector similar to an FM discrimi­ may also be performed automatica lly by a compari­ nator. The comparator develops, when phase lock is son circuit built into the equipment being serviced. achieved, a DC error signal proportional to the ampli­ This does not mean that the necessary adj ustment is tude and direction of frequency error of the STALO accomplished automatically. It merely means that (SMO). This DC error signal is then applied to a the technician will not need to carry test equipment feedback network to correct the STA LO (SMO) error. to the user (primary) equipment site to determine A panel meter enables th e operator to read the value that an "off -frequency" condition exists . Further of the error signal, and more important, to asc ertain discussion of automatic, semi -automatic and manual that the STALO (SMO) is phase-locked with the refer­ frequency measurement techniques is beyond the ence oscillator. This type of frequency control can scope of this article. The point to be remembered produce the desired output frequency directly without is that the frequency standard is a reference, not a generating a multitude of harmonic and mixer products meter or test instrument. whtch would have to be suppr essed. This reduces the Since many equipments contain their own "fr e­ ' need for extensive and complicated filters . quency standards, "you may ask why we have the ! Trouble points to look for in frequency synthesi­ I zers and stabilized oscillators include: AN/ URQ-9 and AN/URQ- 10. The answer is simple. 1. Trouble Point In order to calibrate the less accurate standards I ·I Small frequency errors (less than 1 kHz (approximately 1 1Oth as accurate ) built into many I Cause equipment s, the AN/URQ-9 and AN/URQ- 10 fre­ I Aging of reference crystal. quency standards are calibrated in Navy calibration Failure of temperature control in control laboratories, then delivered "hot" to ships and shore in crystal overn. installations where they must each be connected to a Failure of corrective feedback circuit. reliable power source to ensure that they retain the 2 2. Trouble Point stability which has required months or more to Large frequency errors (increments of establish. Note that the "hot " condition is maintained 1kHz, 10 kHz, etc. ) by standby battery operation. Thi s is limited to 2

1-11 ORIGINAL ......

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL hours for the AN/ URQ-9, and 8 hours for the AN/ changes, effects of moisture, voltage variation,; and URQ-10. Where the standard is used to drive preci­ other changes in environment. It is within this frame­ sion timing devices, counters, synthesizers and such, work that we speak of stability in terms of 1 part in 9 8 it is obvious that an accurate and stable "house stan­ 10 per day, or 1 part in 10 per 60 days. We mean dard" or ship's standard is required. The ship's tnat if the unit is kept operating so that the crysta l standard is the AN/URQ-9 or 10. is not disturbed, the output frequency will not vary In order for the standard to continue to ;;erve from the assigned value by more than one ten-millionth its intended function, it will be necessary to return of one percent of the assigned value within any 24 hour it periodically to a laboratory for calibration. This period, and not more than one millionth of one percent should be done at least every 6 months. As is the of the assigned value within any 60 day period. For case with all crystal oscillators, those employed in a frequency of 5 MHz, this translates to a maximum the frequency standards are subject to drift. Therefore, deviation of 0. 005 Hz within a 24 hour period and 0. 05 the accuracy of the unit will eventually degrade so that Hz in 60 days. recalibration is necessary. It is necessary to maintain the battery pack in Drift is due to aging of the crystal which is the both the AN/ URQ-9 and 10 to ensure that input power heart of the oscillator. As a rule, the older the is maintained and that the output signal levels are crystal-the more stable it will be. This rule holds matched to the user equipment input tolerances. To true only if the crystal is undisturbed. It can be dis­ facilitate these tasks, Table 1-2 presents a brief sum­ turbed by shock, vibration, inclination, temperature mary of characteristics for both frequency standards.

TABLE 1-2. CHARACTERISTICS OF FREQUENCY STANDARDS AND ASSOCIATED DISTRIBUTION AMPLIFIER

Characteristics AN}URQ -9 AN/ URQ-10 AM-2123/ U Height (inches) 11 7-13/16 5-7/32 Width (inches) 21 (incl. case) 5-1/2 19 Depth (inches) 13 15-5/ 16 8- 1/2 Volume (cubic feet) 1. 78 0.38 0. 33 (max. ) Weight (pounds) 70. 8 22 16 Normal Mounting 19-inch rack 3 abreast in 19-inch rack 19-inch rack Input Voltage 115V(±10o/o at 60 Hz 115Vrms at 50 to 400 Hz 115Vrms at 50 to 400 Hz (±3Hz) Input pow er 56 Watts nominal;240 15 Watts nominal 26 Watts nominal max Operating Temperature Range o· to so•c oo to 50"C o· to so·c Output Frequencies 0. I, 1. 0 and 5. 0 MHz 0. I, 1. 0 and 5. 0 MHz 0. 1, l. Oand 5. 0 MHz Output levels:

50-ohm load I volt (min ) 1 volt (min) 4 to 5 volts rms based on input of 0. 5 to 5. 0 volts rms !-megohm load 2 volts (min} 2 volts (min} Continuous operation time on battery (after loss of primary pow er} 2 hours 8 hours batteries not supplied with unit

Output spurious levels (50-ohm load} 0. 1 mV (max} 0. 1 mV (max} at least 80 dB down Output harmonic levels (50-ohm load} 10. 0 mV (max} 10. 0 mV (max} at least 60 dB down 9 Frequency Stability (max drift} 1 part in 1 o9 per day 1 part in 1 o per day N/A and not more than and not more than 8 1 part in 1 oB in 1 part in 10 in 60 days 60 days

ORIGINAL 1-12 ...... - ... - ... -

COivi iviUNICA TIONS NAVSEA 0967-LP-000-0010 GENERAL

When user equipments are located remotely installed ships frequency standard system in pre­ from the frequency standard, it will be necessary to ference to the equipment's internal standard for employ Radio Frequency Amplifier AM-2123(V)/U to maximum circuit reliability. sustain signal strength of the reference signal enroute The basic frequency standard system, as shown to the user equipment. The amplifier will boost the in Figure 1-8, utilizes RF Amplifier AM-2123/ U for output of the frequency standard from 1 volt to a isolation and distribution of 0. 1, 1, and 5 MHz fre­ maximum of 5 volts. In a low-loss, coax, 50-ohm quencies generated by the AN/URQ-9, 10. This RF distribution system, this will adequately serve dis­ amplifier must be used when more than one trans­ tances of more than 1, 000 feet. Input tolerances mitter or receiver is to be connected to the frequency for some user equipments may dictate the need for standard. The AM-2123/ U accepts the three input attenuators to prevent overdriving the reference frequencies from the frequency standard and provides input circuits. Consult the technical manuals for 12 isolated outputs in any combination of the three user equipments prior to use. input frequencies. For additional information on AN/URQ-9, When installing the AM-2123/U, an appropriate AN/URQ-10, and AM-2123(V)/U, refer to the tech­ amplifier plug-in module must be installed for each nical manuals indicated below . If further information individual equipment for which it is to be used; i. e. is then required, consult your· nearest calibration 5 MHz modules for the AN/WRC-1, AN/URC -35, facility or NAVSEC 6181D. (EIB 712) AN/ URT-23, AN/ URT-24, and R-1051/URR; 1 MHz module for the AN/WRR-2. If additional modules Equipment are required to change the frequency complement of Model Publication Number the amplifier, they may be ordered on an exchange basis from ESO. The FSN for the amplifier modules AN/URQ-9 NAVSHIPS 0967-007-801 1 are as follows: (Change 2) (formerly NA VSHIPS AM-2123/ U (0. 1 MHz IN5820-940-3259 93805(A)) dated 3 April 1967 amplifier) AN /URQ-10 NAVSHIPS 0967-053-7010 AM-2123/U (1 MHz IN5 82 0 -940-3260 (Change 1) dated 21 Oct 1966 amplifier) AN/URQ-10A NAVSHIPS 0967- 170-3010 dated *A M-2123/ U (5 MHz IN5820-940-3262 15 Sept 1966 amplifier) AM-2123(V)/U NAVSHIPS 0967-136-1010 *The AN/WRC-1 equipment requires two inputs, AM-2123A(V)/U NAVSHIPS 0967-225-9010 dated one for the transmitter . 23 Jan 1967 Most communication equipments are designed to accept a reference input at a maximum level of h. FREQUENCY STANDARD SYSTEMS 3 volts rms. The output of the AM-2123/ U may be Frequency Standards AN/ URQ-9, 10 provided as high as 5 volts rms; however, the level of the signal to ships are intended for installed system use and not at the user end of the reference feeder cable may be as a "test equipment. " The AN/ URQ-9 and 10 considerably lower than the 5-volt level at the source provide a much higher order of frequency accuracy end. Attenuation over the cable run depends on the than that provided by frequency standards included length of the run and the frequency. The voltage within most new equipments. The frequency stan­ should be measured at the time of installation. If it dards do not measure frequency, they provide highly is greater than 3 volts, an attenuator should be stable and accurate reference signals against which inserted at the user end connector. A suitable atten­ other signal sources such as the Translator-Synthesizer uator for this purpose is NARDA Model 755 -3 (FSN unit of Radio Receiver R-1051/URR may be compared. 9N-5905-862-3291), which provides 3dB attenuation. When an AN/URQ-9 or 10 is provided to a ship, it NAVSEC drawing RE-F26879 15 provides ship should be permanently installed as a central system. Frequency Standard System installation information. (See Figure 1-8) The appropriate communication equipment technical Equipments such as the AN/WRC -1, AN/ URC-35, manual should be consulted regarding use of the AN/WRR-2, AN/URT-23, AN/URT -24, and R-1051/ external standard as a comparison reference in the URR are examples of communication equipments calibration of the equipment's internal frequency having the capability of using either an internal or standard. external frequency standard. The internal frequency standard unit of these equipments is intended for NOTE use in installations not having an AN /URQ-9 or 10 When calibrating an equipment's internal installed or for backup use in the event of any failure frequency standard, it is ess ential that the of the installed external frequency standard system. standard be energized for a continuous Where there is no installed central reference system, period (not less than two weeks preferred). the equipment's internal frequency standard must be calibrated periodically against an external frequency It is essential that the communication equipments source, such as a po rtable AN/URQ-10, to maintain be run continuously (operate or in "standby" condition) their rated accuracy. Frequency standard "age" with since the on-off cycling of the equipments ' prime time, causing drift and a reduction in frequency power will cause a degradation of the equipments' accuracy. internal frequency standard unit. (EIB720) It is essential that equipments such as the R-1051/URR, AN/WRR-2, and AN/URT -23, when 1-4 UHF COMMUNICATION SYSTEMS used with multiplex equipment AN/UCC -1, use an It has been demonstrated repeatedly that UHF can provide satisfactory communication over line-of­ sight distances. However, all parts of the system

ORIGINAL 1-13 ,,

(") 0 C> ;;: ::0 ...... ;;: Ci) c ...... z 2:(") ):::o :» r- ...,

0z (/J

'·

OTHER SPACES (AS REQD) :z )::oo <: Vl I'T1 )::oo RG-215/U 0 \0 O'l I ""'-! ,, - I *" AUX RADIO RM r- � USER EQUIPS (12 MAX) I C> } C> C> I C> C> __, RG-58/U 0 --- � USER EQU IPS ml1 (12 MAX)

'. RG-215/U ,,

XMTR RM 2 RADIO CENTRAL

Cl l:'l z l:'l !Jl Figure 1-8. Frequency Standard Distribution Diagram, Typical Shipboard Installation :» t'"

..

'. . . .. '...... ,- . .,. ,- ,- . I COMMUNICATIONS GENERAL NAVSEA 0967-LP-000-0010

must operate normally in order to avoid communica­ the RF amplifier cannot be made to track properly ·! tion failures. Thus it is desirable to have at hand with the RF os cillator. I some means of checking the parts of the system and the ov er-all performance. Off-frequency IF alignment comes about be­ A simple check with a nearby ship and a report cause most signal generators (AN/ UR M-25, AN/ of "I hear you loud and clear" indicates little more URM-26, LR) cannot be set accurately enough to a than that the equipment is turned on, patched to the given frequency solely by reference to the signal right outlets, and on the same channel. It does not generator dial. For proper alignment procedure, indicate whether a slightly greater range is obtainable. refer to Super-Heterodyne Receiver Alignment in However, this indication can be obtained from the Subsection 1-8. equipment with some additional work. Adequate range is obtainable only by reducing b. TRANSMISSION LINE TESTS the losses (expressed in decibels) over the complete With a suitable fitting for a megohmmeter (Radio circuit to a satisfactory low level. Assuming some Frequency Jack UG-21 I U and Radio Frequency Adapter signal-to-noise ratio at the headphones is necessary UG-29 I U, the antenna cables can be checked. A for satisfactory reception, it is possible to figure the resistance reading well below one megohm suggests transmitter power necessary if the receiver sensitiv­ a short circuit developing in the cable; a reading ity, cable loss, receiving antenna gain, attenuation of several hundred megohms suggests that the inner in space, transmitting antenna gain, and transmitter conductor may be open. A more complete check of cable loss are known. It follows that for a known open circuits is given by shorting the insulated half distance between stations, it should be possible to of the antenna dipole to ground, but the protective use the input meter of a Receiving Set, Radio AN/ paint makes this method unsatisfactory as a routine URR-35 or Radio Receiving Set AN/URR-13 to de­ measure. Removing the antenna connector and termine whether there are any unacceptable losses shorting the inner conductor of the cable to the copper in the system. This over-all check is desci-ibed in braid gives a useful check, but in one case this did greater detail following some methods of checking not disclose an open circuit within the antenna itself. parts of the system. It is desirable to ascertain the cable Joss The methods described are not intended to between the receiver and the antenna. This can be replace the maintenance checks prescribed for equip­ determined by disconnecting the cables from two ments in applicable POMSEE publi cations, but are to antennas and joining the cables with a Radio Frequency be used with the maintenance checks to provi de an Adapter UG-29/U connector in order to form a loop. over-all systems check. Connect the signal generator to the receiver and adjust the attenuator to give a convenient reading, a. RECEIVER SENSITIVITY such as 0. 25 rna, on the receiver 's input meter. The receiver sensitivity should be measured. Then connect the receiver and signal generator to It should be possible to obtain a 10-dB signal-to ­ the two ends .of the loop of cable and readjust for the noise ratio with less than 10 microvolts input from a same input meter reading. The difference between signal generator, such as RF Signal Generator Set the two readings of the attenuator gives the total ANIURM-26. This subject is described in the cable loss, roughly half of which is in each cable. instruction book and maintenance standards book for This may be checked further by measuring other the particular receiver under test. connectors on the mast to determine the exact Joss The sensitivity of the receivers may be mea­ in each cable. The Joss in an average length of Radio sured also through associated cables and connectors Frequency Cable RG-218IU may be as low as 6 dB, (including the transmitter antenna relay if the same but losses as great as 18 dB have been found in long antenna is used for transmitting and receiving) in runs of smaller cable such as Radio Frequency Cable order to aid in locating trouble in associated local RG-10/U. Input and output readings on any multi­ cables and connectors. couplers may be obtained at this time. Ships have reported unsatisfactory UHF com­ The previous check gives a positive measure munications with respect to distance, even though of cable loss but requires making connections on the the sensitivity of the UHF receiver is 1 or 2 micro­ mast. A routine over-all check can be made from volts for 10 dB S+N IN ratio. Normal UHF communi­ the receiver location with much less work. This is cations can be expected out to 40 or 50 miles with done by connecting the signal generator to one antenna aircraft at an altitude of 10, 000 feet (line of sight) cable and picking up the signal in a receiver connected or 13 miles surface to surface. Ranges in excess to another antenna. With close spacing of antennas of these, however, are common. If these minimum (about 6 feet) and moderate runs of Radio Frequency conditions cannot be met, the complete UHF instal­ Cable RG-218IU, the round trip loss will be about lation should be checked. 30 dB. With an antenna spacing of about 60 feet, the A frequent cause of unsatisfactory UHF per­ loss will be around 50 dB (20 dB more for a 10-to-1 formance is misalignment of the receiver IF ampli­ increase in antenna spacing ). Either figure will be fiers. In some cases investigated, the receiver greater with longer cable runs or smaller cable. was found to habe been aligned as much as 100 kHz This type of· check can be made regularly in a few ·off frequency. Misalignment of receiver IF should minutes, giving an early indication of cable or be suspected when better communications can be antenna trouble. It is superior to using a "megger" established on manual mode than on crystal mode of because it shows trouble that does not give normal operation. However, a UHF receiver should not be megohmmeter readings . The two sets of measure­ used in the manual mode because of the tendency of ments listed in Table 1-3 illustrate the point. the receiver to drift off frequency. The problem is It is clear from these figures that antenna No. 3 further aggravated because, with the IF off frequency, developed an increased loss of about 16 dB, although it continued to check satisfactory (300 megohms) on a

ORIGINAL l-15 ......

COMMUNICATIONS NAVSEA 0967-LP- 000-0010 GENERAL

"megger. " This procedure is very helpful when the when the magnitude of the round trip loss has been figures have been recorded from time to time and determined to be satisfactory. ------TA BLE 1-3. ROUND-TRIP ANTENNA MEASUREMENTS TAKEN AT FIFTH NAVAL DISTRICT HEADQUARTERS

21 Januar:z: 23 February Attenuator Loss Attenuator Loss Change (dB) (dB) (dB) (dB) (dB)

Sig Gen direct -56. 0 -68. 2

Antenna #1 to #2 -9. 3 46. 7 -15. 9 46. 6 -0. I (about 40 feet)

Antenna #1 to #3 -9. 2 46. 8 -5. 7 62. 5 +I5. 7 (about 40 feet)

Antenna #2 to #3 -27.6 28. 4 -17. 7 44. 8 +16. 4 (about 4 feet)

c. TRANSMITTER TUNING AND POWER CHECK receiver connected to a separate antenna, preferably Most transmitter tuning should be done with one on a different yardarm. Inasmuch as the signal RF Wattmeter ME-11 /U substituted for the antenna. varies as 1 /d (inverse distance) within the horizon 2 This not only eliminates interference with other ships, (changing to I I d beyond), there is a direct relation­ • but enables proper tuning to assure loading for max­ ship between the receiver input meter and the i imum power output under conditions of radio silence. distance range on the surface that can be expected The antenna circuit may be returned for maximum of the equipment. For ships with high antenna, the deflection on the transmitter tuning meter after the following should be experienced: antenna has again been connected to the transmitter, since some standing wave conditions on the trans­ Input Distance mission line may make such retuning necessary. Meter Between dB Below When in port, the wattmeter may be moved to the (rna) Antennas 0. I volt antenna end of the transmitter cable to check cable loss if the performance of the system warrants it. 0. 87 6 feet 9. 0 A wattmeter or signal strength monitor may 0. 82 60 feet also be connected to an adjacent antenna to ascertain o. 74 600 feet 29. 0 that the transmitting antenna is radiating power o. 60 I mile 49. 0 effectively. If a wattmeter is connected to the cable o. 36 10 miles 69. 0 leading to an adjacent antenna, the reading is likely o. 05 20 miles 95. 0 to be less than one watt. This is not adequate for a satisfactory system check using an ME-11 /U type Each installation will have to be checked when wattmeter, but it does give some confidence in the in good condition for the standards to be expected performance of the R-F cables and antennas. A during routine testing or operating conditions. It is more sensitive wattmeter such as the CAQI-430 obvious that, except for meter readings above about series can be used provided not more than 0, 1 watt 0. 85 rna which are less accurate, observation of the (+1 0 dBm) is applied to the wattmeter. This may RECEIVER input meter tells much more about the require an attenuator of adequate insertion loss and operation of uhf equipment than does the fact that power capability. The CAQI-430 series wattmeter "strength five" signals were received at all the can make precision measurements of transmission distance listed in chart. The system described in losses in the antenna system in the same manner as the previous paragraph is applicable to equipment described for using a signal generator with a on the same ship, nested ships, or widely spaced receiver. ships. Therefore, it provides a useful tool to con­ The quickest and easiest check is to use an firm satisfactory operation of uhf equipment and to AN/URM-50 signal strength monitor. Signal strengths assist in locating faulty equipment or installations. and modulation quality checks are simple to make, and It provides a means of checking each channel of each comparison of measured signal strengths against transmitter against each receiver, to provide as­ those made with antennas known to be good can dis­ surance that there are no inoperative channels. It close poor antenna performance. However, if a does not, however, directly check the antenna radia­ receiver is available near the transmitter, the tion at all oearings, though thi s may be done also by receiving antenna checking procedure described swinging ship and observing the input meter variations. previously can be used to measure the round trip In a normally sensitive receiver, the input loss in two antennas and their cables. meter changes close to 0. I rna between 0. 1 and 0. 5 on the scale, for each 6-dB change in receiver input. d. SYSTEM TESTING For those ships having Monitor, Radio Fre­ For routine checking of the uhf system, it is quency AN/URM-50, rough operational standards may more convenient to test both the transmitting and be determined when setting up the frequency plan. receiving portions of the system at the same time. Each transmitter frequency should be monitored and This may be done by using uhf transmitter on its a graph or chart made to indicate relative power normal antenna, observing the input meter of a uhf output at each frequency. This does not check the

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receiving portion of the system, however, and in Because of the more exacting tolerance, it is many instances the antenna on the radio frequency recommended that a periodic check of all UHF fre­ monitor is not well located; if it is available, it should quencies be made, The interval should be contin­ be used whenever possible. gent on the amount of surface-to-air communications In addition, there is the multicoupler problem the particular ship conducts. (EIB 688) that may be minimized by an extension of the tests and principles applied herein. Many cases of extreme 1-5 TELETYPE EQUIPMENT losses have been noted by means of wattmeter tests, but tuning for maximum output is often a problem, a. THE RATT PROBLEM especially when several frequencies close together In recent years, the U. S. Navy has vastly are set up on the same multicoupler combination. improved its radio teletype capabilities by the intro­ As in any system, it must be noted that often duction of several new items of equipment providing unrelated parts of the system can influence the opera­ either single or multi-channel radio teletype (RATT) tional capabilities of the plant. Therefore, quick and transmission modes. An added dividend acquired meaningful tests must be available to the technician, along with this new equipment has been an increased and preferably the operator, so any question as to flexibility in the specific combinations of ancillary system reliability may be readily resolved. equipment that can be used. This situation, however, has caused certain problems in the specification of e. FREQUENCY COMPATIBILITY BETWEEN frequencies for radio teletype transmissions. In UHF EQUIPMENTS addition, there has also been some confusion over the Difficulty has been reported in establishing proper emission designators to be used. This article communications between UHF equipments having should clarify some of these problem areas. 1750 channels and those having 3500 channels. The Navy presently uses two types of RATT Service and operating personnel should be alerted to emissions, (see Table 1-4). Both variations require the closer frequency tolerances required for communi­ the use of two discrete radio frequencies to produce cating between these equipments. one channel of radio teletype: one frequency for the At present, 3500-channel equipments are almost MARK signal and the other for the SPACE signal. At totally limited to airborne applications. Because air­ any given instant of time, one and only one of these to-ground communication is the most utilized trans­ frequencies is being emitted by a transmitter. mission path for UHF, shipboard technicians and The two types of emissions are: operating personnel must assure that their equipment l. F1 emission-shifting an umodulated radio is maintained on frequency. frequency carrier back and forth between the two The problem of poor or no communication is discrete frequencies of a teletype channel, one fre­ normally diagnosed as incompatibility. In most quency being the MARK signal and the other the cases, however, the problem is that the frequency SPACE signal. This is commonly referred to as FSK accuracy of the 175 0-channel equipment has not (frequency shift keying) RATT and is single channel been maintained. Frequency accuracy incompatibil­ teletype unless time division is employed on the two ity may be the result of a crystal-controlled oscillator discrete frequencies to achieve multichannel opera­ being tuned for peak output instead of being tuned to tion. For reasons of clarity, it is more descriptive the correct frequency with an accurate counter. In if this emission is referred to as RFCS RATT (Radio the case of multiple crystal oscillators in a frequency Frequency Carrier Shift Radioteletype) instead of FSK synthesizer scheme, this possibility is even more RATT. apt to be the reason because frequency errors are 2. A7 type emissions (A7, A7B, and A7J)­ cumulative. Frequency inaccuracies should always keeping the radio frequency carrier constant and be suspected when poor or no communication is shifting back and forth between two discrete audio established between 1750 and 3500 channel equipments. frequency tones to produce the MAR K/SPACE signals The 3500-channel UHF equipments operate with of a teletype channel. Each channel of radio teletype a receiver bandwidth of 50 kHz at the 6 dB points; the information in an emission requires its own pair of 175 0-channel equipments have a receiver bandwidth tones. If frequency diversity operation is desired, of 80 kHz. A transmitter frequency that may be well the teletype channel information is duplicated on a within the 80 kHz of the 1750-channel equipment may second pair of tones. By international definition, be barely within the 50 kHz bandwidth of the 3500- this would be A 7 type emission only if two or more channel equipment. Furthermore, the receiver IF pair of teletype tones (multichannel) are being strip may have been aligned with an inaccurate ·signal transmitted. As there is no internationally agreed generator so tha t th e bandpass is not centered at the emission designator to be used when only one pair of correct frequency. Therefore, communication may teletype tones is being transmitted, the Navy uses A 7 not be established, particularly if the transmitting to denote single as well as multichannel RA TT of this sta lion frequency error is in one direction and the type. A 7 type emissions have been referred to by a receiving station error is in the other. A subsequent variety of terms, including Tone Modulated RA TT, section, SUPERHETERODYNE RECEIVER ALIGN­ FSK RATT, VFTG, SSB RATT, DSB RATT, and MENT ADJUSTMENTS, describes a method of attaining ISB RATT. It is more descriptive if A7 type emis­ proper receiver alignment. Pertinent information sions are referred to as AFTS RATT (Audio Fre­ also appears in AN/GRC-27, 27A Technicians Hand­ quency Tone Shift Radioteletype) instead of the various book NAVSHIPS 0967-031-8040. In any case, the foregoing terms. frequencies of the transmitter and receiver oscilla­ Another mode of transmitting radioteletype tors should be set accurately during alignment and signals is the "on-off keying" mode, mentioned here checked periodically thereafter, using a frequency only for completeness. In on-off radioteletype keying, counter.

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COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

the MARK is denoted by transmitting a signal on one emission bandwidth must be confined within the author­ discrete frequency and the SPACE is denoted by the ized bandwidth of the assigned frequency and should absence of the signal. The emission designator is be centered as nearly as possible. A1, A2, or F2, depending upon the particular mode Based on the expanded list of emission designa­ variation being used. This radioteletype mode is tors, the following are samples of OPORD or OPLAN rarely used by the Navy /Marine Corps. use of a hypothetical frequency assigned by CNO to The following types of emission designators are a command. representative of those in use by the U. S. Navy and CNO assignment: U. S. Marine Corps. In the standard four part emis­ 3010. 5 (3009) kHz, 1.24F 1, 3A 3J, 3A7J sion designator, the first number indicates the Possible OPORD authorizations: "necessary bandwidth" required by the emission. a. 3010. 5 (3009) Hz, 3A 3J-Telephony (SSE) The "necessary bandwidth" calculations for the older b. 3010. 5 Hz 1. 24F1-100 wpm RFCS RATT type emission designators (. 6F 1, 1. 08F 1, 1. 7F 1, c. 3010, 5 (3009. 9) Hz, 0. 3A 7J-100 wpm 2. 04A2, 2. 85F1, 4F4) are based on formulas found SSE AFTS RATT (if transmitters have in the Radio Regulations, Atlantic City, 1947. The 0. 1 Hz incremental tuning capability) "necessary bandwidths" resulting from calculations d. 3010. 6 (3010) Hz, 0. 3A 7J-100 wpm SSE using applicable formulas in the current authority, AFTS RA TT interim assignment (if Appendix 5, Radio Regulations, Geneva, 1959 (upon transmitters have only 1 Hz incremental which most of the designators listed in Table 1-4 are tuning capability) based) differ slightly from the 1947 values. Further­ el. 3011 (3009) Hz, 1A7J-100 wpm SSE more, the 1959 bandwidth formulas are themselves AFTS RATT (interim assignment due now under study by the International Radio Consultative 1-kHz tuning) Committee (CCIR) of the ITU, and will probably be e2. 3011 Hz 1A7B-100 wpm ISB AFTS RATT revised at a future international conference. There­ (interim assignment due 1-kHz tuning) fore, in the interest of continuity and clarity, the e3. 3011 Hz 1. 24Fl-100 wpm RFCS RATT following steps have been taken: (if required to net with SSE and ISB 1. The older designators involving primarily RA TT equipment). older equipment have been retained. The bandwidth These assignments illustrate five possible stated in each case is slightly greater than that de­ channel or net uses of an available frequency. All of rived from the more recent formulas. them cannot be used simultaneously in the same area. 2. New designator "necessary bandwidths " When all HF equipment is capable of 0. 1-kHz incre­ have been calculated from the most nearly applicable mental tuning, the illustrated "interim" assignments, formula in Appendix 5, Radio Regulations, Geneva, in which the emission is not centered on the "assigned" 1959. frequency should be deleted. The listing in Table 1-4 is not all inclusive. As a matter related to spectrum conservation, For example, the emission designators for various it would be interesting to ascertain the operational types of tone generated CW (AN/URC-32, AN/TRC-75, flexibility that might be realized with the 0. 3A 7J AN/PRC-47) have been omitted. In addition, for the emission. Providing adequate measures are taken sake of brevity, all possible variations of multiplexed in respect to equipment separation, power output, emissions have not been li sted. Although the offset of transmitter frequency accuracy, and receiver band­ the CW tone from the suppressed carrier (dial) fre­ width, and if used only where operational needs dic­ quency may vary, the old 0. 1A1 designator coupled tate, it would appear that three 100-wpm RATT nets with an assigned frequency is sufficient to permit could be accommodated in an authorized 3-kHz band­ netting. Care must be taken when incrementally tuned width (e. g. , 3009, 6(3009), 3010. 6( 3010), 3011.. 6 SSE receiving equipment is used on a CW net in (3011)). common with transmitting equipment which employs a The assignments listed as e1, e2, and e3 could keyed carrier frequency for CW operation. have been on 3010 kHz, but in order to be as consistent Notice that some necessary bandwidths have been as possible with the instructions in paragraphs 1 06d specified to more significant numbers than others. and 606d, JANAP 195, the 3001-kHz assignment is This was done merely to provide a numerical differ­ preferred. In cases involving single sideband (SSE) ence between 60-wpm and 1 00-wpm teletype designa­ emissions, the suppressed carrier frequency is listed tors which, otherwise, would be identical if "rounding in parentheses, following the assigned frequency. off" rules were followed. For example, 1A 7J could This technique merely provides a reference point in be used to indicate either 1 00-wpm or 60-wpm single that the suppressed carrier frequency is usually the channel SSE AFTS RATT, depending on local operating frequency appearing on the transmitter dials. (EIB 711) procedures or practices. Any emission may be used on an assigned fre­ b. TUNING IN A SINGLE CHANNEL RFCS quency, providing the bandwidth does not exc eed that RATT SIGNA L authorized and the modulation type, transmission type, Many good RATT signals are so degraded at the and supplementary characteristics are the same. One receiver that they become either unreadable or take exception to this rule is the current CNO authorization too many hits to be of much use. This is often the for USN activities and forces to utilize emissions not result of improper tuning of the receiver. The intent exceeding 1. 24A 7J on all frequencies assigned with of this article, therefore, is to provide some under­ 1. 24F1 emission. standing of the required tuning procedures for proper It is also important that the radiated emission reception of RATT signals. should be centered on the assigned frequency. In the Single channel teletype transmissions in the MF event equipment limitations preclude centering, the and HF bands use a radio frequency carrier shift (RFCS) of 850 Hz, or :t 425 Hz with respect to the

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TA BLE 1-4. EXAMPLES OF RATT EMISSIONS

Designator Type of Emission Sample Equipment Remarks

0. 1A1 CW Manual Morse TBK Telegraphy 0. 28A 7J 60 wpm Single Chan SSB AN/SGC-1 w/AN/WRT-2 (HF) Note 1 AFTS RATT 0. 3A7J 100 wpm Single Chan SSB AN/SGC-1 w/AN/WRT-2 (HF) Note 1 0. 6F1 60 wpm Single Chan RFCS TA D-7, AN/WRT-1 (LF /MF) Note 2 RATT 0. 98A 7J 60 wpm Single Chan SSB AN/URC -32, AN/FRT-39, AN/TRC - Note 3 AFTS RATT 75 (HF) 0. 98A 7B 60 wpm Single Chan AN/WRT-2 (HF) Note 4 ISB AFTS RA TT 1A 7J 1 00 wpm Single Chan SSB AN/URC-32, AN/FRT-39, Note 3 AFTS RATT AN/TRC -75 1A7B 100 wpm Single Chan ISB AN/WRT-2 (HF) Note 4 AFTS RATT 1. 08F 1 60 wpm Single Chan AN/SRT-15, TBK (HF) RFCS RATT 1. 24F 1 100 wpm Single Chan AN/SRT-15, TBK (HF) RFCS RATT 1. 5A7 60 wpm Single Chan AN/SGC-1 w/TED (UHF) DSB AFTS RA TT 1. 6A 7 100 wpm Single Chan AN/SGC -1 w/TED (UHF ) DSB AFTS RA TT 1. 7A 7J 1 00 wpm 8 Chan SSB AN/UCC-1 w/FRT-72 (LF) Note 5 AFTS RATT* 1. 7F 1 60 wpm 4 Chan Time AN/UGC-1 w/AN/SRT- 15 (HF) Div RFCS RATT 2. 04A2 1020 Hz AFT Beacon AN/WRT-1 TED (MF /UHF) Homer Beacon 2. 85F1 1 00 wpm 4 Chan Time AN/UGC-1 w/AN/SR T-15 (HF) Div RFCS RA TT 3A 3J Telephony (SSB) AN/URC-32, AN/WRT-2 (HF) 3A7J 100 wpm 16 Chan SSB AN/UCC-1 w/AN/WRT-2 (HF) Note 6 AFTS RATT'' 4F4 Facsimile (HF) 6A3 Telephony (DSB AM) AN/SRT-15 (HF) 10A3 Telephony (DSB AM (MF) Broadcast quality) 16F3 Telephony (FM Narrow (VHF) AN/VRC-46 Band) 30F3 Telephony (FM) AN/PRC-25, AN/VRC-12 (VHF) 36F3 Telephony (FM) AN/PRC-10 (VHF) 80F9 Multiplexed telephony (FM) AN/TCC-1 () w/AN/VRC-12 (VHF ) 120F9 Multiplex telephony (FM) AN/TCC-3 w/AN/GRC-10 (VHF)

*Based on measured data in the absence of precise mathematical formulas. Note 1. The AN/SGC-1 produces 700-Hz and 500-Hz mark/space tones. Therfore, these emissions would be centered 600 Hz from the suppressed carrier in the chosen sideband with a plus-minus 100-Hz shift. Note 2. This designator is retained to normally indicate a plus-minus radio frequency carrier shift of 85 Hz (total 170-Hz shift) for mark/ space signals. Note 3. The AN/URC-32 and AN/TRC-75 type equipment produce 2425-Hz and 1575-Hz mark/space tones. Therefore, the emission is centered 2 kHz above or below the suppressed carrier (dial) frequency, with a plus-minus 425-Hz shift for mark/space signals. Suppressed carrier (dial) frequency should be 2 kHz above or below the assigned frequency. Wherever appearing, the AN/FRT-39 type equipment is assumed to include ancillary equipment such as the TH-39/UGT. Note 4. The AN/WRT-2 type equipment produces 425-Hz tones in the USB and LSB to indicate a mark or a space signal. Therefore, the emission is centered on the suppressed carrier (dial) frequency with a plus-minus 425-Hz shift for mark/ space signals. Note that suppressed carrier frequency is the assigned frequency. Note 5. This designator covers the use of the eight pairs of tones centered on 1615-Hz and below. Note 6. If all channels are not keyed, the necessary bandwidth for this mode will actually be dependent upon how many and which specific channels are used. In the interests of simplicity, it is recommended that only the 3A7J designator be used to indicate HF -SSB AFTS multichannel emission.

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assigned frequency. If the assigned frequency were that now cannot be offset by 2550 Hz in a stabilized 8694 kHz, this would be the center frequency to be mode can be operated with a stabilized 2. 0 kHz radiated from the transmitter. Two signals would offset. TTY terminal units so converted will copy be transmitted alternately, and neither of the signals 2425 Hz as a mark and 1575 Hz as a space, which would be 8694 kHz. The teletype mark signal would are the values currently used by the AN/URC-32, be transmitted 425 Hz above the center frequency of the AN/ARC -94, and some others. 8694, and the space signal would be transmitted 425 In order to produce reliable copy of RFCS Hz below the center frequency. This means that the RATT signals, a receiver should be operated in a transmitter would develop a mark signal of 8694. 425 tuning mode that provides best stability and accuracy. kHz and a space frequency of 8693. 575 kHz. Only By using TTY terminal units centered on 2. 0 kHz, these two frequencies need be received, and the the associated receiver can be operated at stabilized receiver should be set to receive them in the center increments of frequency. For use with unmodified of its reception "window" or passband. older TTY terminal units, some receivers such as Receivers used for reception of RFCS RA TT those of the AN/WRC-1, AN/URC-32, and AN/URC - signals vary in their details, but in general the 35 employ BFO (carrier) injection only at the dial receiver should be tuned in the following manner: frequency and therefore the tuning cannot be offset 1. First set the receiver passband to a fairly by the required 2550 Hz while the receiver is in a narrow value, on the order of 1 kHz. Tune the stabilized mode. For operation of the R-1051/URR receiver to the frequency of the desired RA -r:T signal receiver (Part of the AN/WRC-1) with 2550 Hz by observing the receiver INPUT or CARRIER terminal units, the following procedure will be LEVEL meter. Ignore the received pitch at this helpful: point, or better yet, turn the BFO off until the signal 1. The receiver "window" or reception pass­ is tuned so as to center in the receiver passband. band is offset 1. 5 kHz from the BFO (and the dial Then lock the main tuning dial if possible. reading) by selecting the SSB mode. For single­ 2. Turn on the receiver BFO and set its channel RFCS, the mark/ space relationships are frequency 2. 0 kHz BELOW the center of the receiver correct when upper sideband is selected. passband (2550 Hz for receivers used with older, 2. Switch the main tuning to VERNIER and unmodified TTY Terminal Units). This value is set it for 3 kHz BELOW the assigned frequency. The used because single-channel TTY converters use a R-1 05 1 /URR receiver frequency control is indepen­ passband centered at 2000 Hz in present units, or dent of the transmitter, which is set 2. 0 kHz below 255 0 Hz for older units. Some receivers have an the assigned frequency channel for RFCS operation. "FSK" mode in which the BFO is automatically set 3. Tune the incremental tuning to approximately to the proper value by the mode switch. Other 450 Hz and adjust as previously described for a receivers are merely aligned so that the "zero appearance on the TTY converter scope. beat" position of the BFO falls in the center of its This method of receiver tuning is preferable travel; for these receivers, the proper BFO setting to the use of the CW mode because of the higher for RFCS operating must be found using step 3. stability of VERNIER tuningan d the better selectiv­ Once the proper point on the BFO control is found, ity of the SSB mode. Using the receiver in this it is a good idea to mark it as the "FSK" setting. manner also provides better CW reception than that 3. Place the receiver BANDPASS control in of the CW mode for the same reasons. The R-1 05 1 I the 2 kHz position (note that RFCS RATT emission URR bandwidth is 7 kHz in the CW and the AM modes, is 1. 24F1). With sufficient receiver output to drive and 3. 2 kHz in the SSB mode. The narrower selectiv­ the TTY converter, slowly and carefully tune the ity in the SSB mode provides approximately a 2-to­ BFO (called "FREQUENCY VERNIER " in some one Improvement in signal-to-noise ratio. receivers) until the two horizontal lines on the TTY Because the AN /URC -32 uses only one converter oscilloscope are equal distances above and stabilized oscillator for both transmitting and below the center reference line on the CRT graticule. receiving, it cannot be used in the transceive mode When this condition exists, the receiver is properly with a 255 0 Hz TTY converter. (EIB 644. NCB 112) tuned, with the received signal in the center of the receiver passband as well as in the center of the c. AFCS RA TT NETS TTY converter passband. The common failing is to AFCS terminal units of the AN/S GC -1 series leave the receiver BFO at its center or zer.o beat and the newer CV-2460/SGC are reliable and position and tune the main dial so that the RATT "nettable" items of the ship's TTY system. They signal is 2. 0 kHz off frequency with respect to the are versatile equipments ideal for ORESTES nets center of the receiver passband. The fallacy of within a task group or task unit. For this reason, this procedure should be obvious if you think about it. shipboard operators and technicians should under­ 4. If the TTY printer now "prints inverted, " stand their use and features in order to get the most the order of sidebands has been inverted in the from them. There is no better way to learn the receiver. This happens in some receivers on some capability of an equipment than by actual operation. of their bands. When this is the case, there are This can be done easily by operators who want to two alternatives available: either repeat steps 2 and become proficient, using an authorized UHF drill 3, resetting the BFO ABOVE the center frequency frequency. rather than below, or else operate the TTY converter The AN/SGC-1 and the CV-2460/SGC series NORMAL/INVERT switch to the INVERT position. AFTS terminal units are DC -to-audio converters in (EIB 713) the transmit mode. They receive DC from a teletype A field change has been developed for convert­ loop and convert it into audio frequencies for modula­ ing TTY terminal units to a center frequency of tion of a radio transmitter (note: the transmitter 2000 Hz instead of 2550 Hz so that those receivers must be in the VOICE mode, not MCW mode). For

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COMMUNICATIONS NAVSEA 0967-LP�000-0010 GENERAL

narrow audio frequency shift the high audio tone is bands is 170 Hz. Either terminal unit can be used to 700 Hz and the low tone is 500 Hz. For wide shift copy narrow-shift RFCS of the type used on low fre­ (CV-2460/SGC only) the high tone is 2425 Hz and the quencies when the associated receiver is set up low tone is 1575 Hz. Normally the high tone indicates properly. Just tune up the receiver to the desired a mark and the low tone indicates a space, but thi s signal as previously described in Tuning in A Single relationship can be reversed at will. Channel RFCS RATT Signal, except that the receiver In the receive mode the equipments are audio­ BFO is offset by -600 Hz rather than 2000 Hz (or to-DC converters. Audio from a receiver is fed into 2550 Hz). The audio output from the receiver will be the terminal unit. The signal could have been trans­ near enough to 700 Hz for mark and 500 Hz for space mitted either as AFTS or RFCS, as long as the re­ that the terminal unit can copy it. The CV -2460/SGC ceiver converts it to the proper tones. provides the additional capability of being able to copy Each terminal unit has a mode selector switch wide shift RFCS single-channel circuits. which can place it in constant XMIT or constant RCVE, Either AFTS terminal unit can also serve as a or an AUTO position which permits it to switch to part of single-channel UHF-to-HF relay circuits. It receive whenever a signal arrives from the receiver converts the AFTS signals received on UHFinto a or go to transmit, keying and modulating the trans­ keyed DC loop current, and the loop current in turn mitter, whenever the local TTY keyboard is operated. operates the wide-shift RFCS circuits of the HF This is ideal for net operation. The CV-2460/SGC transmitter. Care must be exercised if the terminal has full duplex capability, permitting simultaneous unit and the HF transmitter have separate loop power use of transmit and receive functions. supplies. The two power supplies must not be patched The AFTS terminal units interface with other together. If such a risk exists, one solution is to equipments via three basic inputs/outputs other wire the terminal unit to a mi scellaneous jack on the than the AC power connection: TTY patch panel rather than to a looping jack. It 1. A DC circuit which is looped through the can then be patched into either loop as required. TTY patch panel. When the receiver input levels and the modula­ 2. An audio input into which a receiver feeds tion output levels are properly set, and the mark and tones. space frequencies are correct, the AN/SGC-1 and 3. A keying and modulation output by which CV -2460/SGC series terminal units will provide the terminal unit controls a transmitter. reliable and versatile communications. (EIB 737, 741) The equipment is very simple to use, and will function effectively provided that compatibility is d. ORESTES NET maintained with the other parts of the system. The Many of the difficulties encountered on TF lTG first point of concern is adjustment of the receiver OR ESTES nets can be attributed to off-frequency that is used to receive the radio signals. If the out­ situations between ships on the net. From measure­ put of the receiver is noisy when no actual signal is ments taken on an AN/U RA-17 converter, it was being received, the noise will trigger the terminal determined that a frequency error in excess of unit into a RCVE condition and it will not go auto­ 300 Hz introduces distortion to a received signal. matically into the XMIT condition when the local A frequency error at 500 Hz makes most received teletype keyboard is operated. The noise output of signals unreadable because of excess distortion. the receiver must be kept low or squelched off Since these frequency errors can be shared by trans­ during the time no signal is being received. Ideally, mitter and receivers, a limit of 150 Hz of tuning the no-signal noise level should be about -30 dB when error is established for either transmitter or re­ the receiver output is set to supply audio tones at ceiver. 0 dB. Noise from the receiver must not be allowed ORESTES nets with ASW aircraft or with to trigger the terminal unit into a RCVE contition Marine Corps units have additional requirements for when no tones are being received. The second point transmitter accuracy because of compatibility consid­ is based on the transmitter modulation level that has erations. The mark-space frequency accuracy for been set on the ship. If all radiophone remotes are working with ASW aircraft is :±-20 Hz at the assigned set to furnish -10 dB modulation level into the trans­ frequency. For operation with Marine Corps units, mitter speech amplifiers, and the audio output of the this accuracy requirement is increased to :!:"15 Hz. AFTS terminal unit is set to furnish 0 dB, over­ It is imperative that absolute frequency control modulation will occur which will cause distortion and be practiced by operator /maintenance personnel. interference. If the output of the terminal unit is set Many of the equipments in the Fleet today, although for less than the standard RPU modulation output, design for systhesized operation, have been long undermodulation will occur which will decrease the neglected. Since equipments can be operated in the reliable communication range between ships. If the continuous mode, it is common practice to operate transmitter has a clipper-filter in its speech ampli­ in this manner. We pay for this malpractice by fier, this circuit should be turned off for tone opera­ accepting poor copy and inordinate delays in passing tion; AGC (or AVC) circuits should be left on. The traffic on nets using this method of communications. audio input and output levels from the TTY terminal A large percentage of ships have AN/U RQ-9 I 10 unit should be set to furnish the same levels into the frequency standards aboard but improperly utilized. audio distribution system that the remote phone units The following equipments are designed for almost furnish. Refer to Transmit-Receive Panels and Re­ absolute highly specialized, highly accurate, fre­ mote Control Units under Subsection 1-9. quency control, and indeed are capable of highly Don't overlook the "spread" between mark and accurate control if operated and maintained properly. space frequencies; 700 Hz and 500 Hz for narrow AN/WRT-2 AN/WRR-2 shift AFTS gives a spread of 200 Hz. The normal AN/URC-32, 35 AN/URT-23 spread for single channel RFCS in the low frequency R-1051/URR AN/WRC-1

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Unless these equipments are operated in their stable should not be used for normal operation of the (synthesized} modes, their dial accuracy may be so DEMUX equipment. There may be a sufficient time far in error (up to 7 Hz ) that netting of crypto-covered delay, between the signals from these two transmitters . ' i teletype nets is often impossible. (EIB 714} in reaching the ship that added distortion may be added to the circuit within the combine units of the AN/UCC-1. e. MULTI-CHANNEL TERMINAL EQUIPMENT Only the lower frequency audio tones are trans­ Multiplexing is the term used to define the art mitted on the low frequency portion of multi-channel of combining more than one channel into one composite broadcasts, because of limitations of antenna band­ channel or trunk so that more than one message at a width and the bandwidth of the transmitter itself. time can be sent on one transmitter. Multiplexing These tones are from 425 Hz to 1615 Hz. There is no is usually shortened to the term "MUX" by radiomen. tone diversity (frequency diversity within the tone The multi-channel broadcast is a good example of package) available. This is not a great hindrance, "MUXING" and "DEMUXING. " The ship utilizes however, in that selective fading is not normally en­ equipment at the receiver end of the broadcast to countered on low frequency transmission paths. "DEMUX" the signal into the individual channels. Ship/ shore termination equipment utilizes the Multi-channel broadcasts and ship/shore ter­ same equipment as the multi-channel broadcast, ex­ minations utilize frequency-multiplexing, whereby cept that the shipboard equipment has a send capability each channel of the composite tone package of the as well as a receive capability. The same operation broadcast or termination is assigned an audio fr e­ exists on a multi-channel (VFTG) ship-shore termina­ quency. The lowest audio frequency used is 425 Hz tion as with multi-channel broadcast. There is one and the highest frequency used is 2975 Hz . The slight difference, and this is an asset in circuit audio tones for the channels are 170 Hz apart and reliability. The shipboard operator controls the hence, there are tones at 425, 595, 765, 935, 1105 , frequency of the shore transmitters by requesting 1275, and so forth. There are 16 tones between the two frequencies at which the shore transmitters 425 and 2975 Hz that are used. This gives a capabil­ shall be operated. The operator can choose two ity of 16 separate channels of intelligence under frequencies that are very close together and, hence, conditions. will assure the same propagation path from the shore In order to give ships more reliability in transmitter to the ship. This condition gives very receiving a multi-channel broadcast, the shore good frequency diversity and the ship should exper­ station "twins" two channels and keys them with the ience extremely good reception. same channel intelligence. Channels are keyed with Reception on the ship of any tone diversity tone the same intelligence to overcome "selective fading" package can be good without utilizing the tone diversity. and to give the receiving station two chances of get­ If one of the audio tone channels is bad in the AN I ting the signals at one time. The twinning process UCC -1 equipment, the output signal of the two audio uses frequencies separated by 1360 Hz to overcome channels involved may be so highly distorted that it the possibility of selective fading causing hits on the cannot be copied. In this case, when one intelligence circuits. Intelligence from one channel is used to channel is unreadable or highly garbled, and the key 425 Hz and 1785 Hz channels or tones simul­ other channels of the ship/shore termination or the taneously. The ship receives both of these tones multi-channel broadcast are good, some remedial and converts them to DC to operate a teletype ma­ action can be taken. A technician on the ship can chine from the best of the two signals. The unit "untwin" the channels concerned and the operator that combines the two signals is called a combiner can try the individual channels and sometimes copy unit, not similar to the comparator unit in an AN/ the signal "fiver" on one channel. URA-8. The theory is that if one tone (425 Hz for MUX and DEMUX theories are not difficult instance) fades out for an instant, the other tone and, if the shipboard operator becomes familiar (1785 Hz) might be loud and clear. Other tones are with the concept of sending more than one intelligence twined for other teletype channels, such as 595 Hz at a time, he can isolate troubles and get good recep­ and 1955, 765 Hz and 2125 Hz, and so forth. This tion in most cases. (EIB 716} limits the 16 tones in most MUX/DEMUX equipments to eight channels of intelligence, but gives better f. SHIP/SHORE MULTIPLEX TERMINATIONS reliability by overcoming some of the effects of Ship/shore multiplex terminations were mea ­ selective fading. Utilizing two frequencies in this sured aboard the USS ELDORADO. The parameters manner is referred to as frequency diversity. examined and recorded were: frequency of the Another form of frequency diversity is avail­ carrier, tone frequencies, relative carrier output able to the ships in both ship/ shore terminations and (when present), and bias distortion. broadcast reception. On the broadcast, there are Continuous samples were taken during the many frequencies (transmitters) on the air with the course of the exercise. Almost without exception, same composite package of tones for the ships to it was found that the shore stations were on the receive. The ship can tune receivers to two of these correct frequency and well within tolerance. Numer­ frequencies and feed both sets of audio tones in the ous readings were measured on 45 different A2/A3 DEMUX equipment (AN/UC C-1). This gives the frequencies. Of these, only four frequencies can equipment two separate audio inputs (from two be transmitted from shipboard transmitters in a different transmitters on two different frequencies) fully synthesized mode. In order to transmit in a to help maintain a good solid signal into the AN/UCC-1. synthesized mode, the carrier frequency must be Frequencies should be selected which are as close in an even increment of 1 kHz. Of those measured, together as possible, such as an 8 Hz and a 12-Hz none were within tolerance. The average error fr equency or a 12-Hz and a 17-Hz frequency. Fre­ was 152 Hz. This indicates that the equipments quencies that are wide spread (such as 4Hz and 17 Hz ) either cannot be operated properly, or that operations are choosing the wrong mode of operation.

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

The solution is obvious. Maintenance personnel must restore the equipment to designed operating standards, and operators must choose the correct mode. Present instructions (COMFIRST-FLTNOTE 2400 of 31 October) dictate that all A2 and A3 trans­ missions will be made in a synthesized mode. Figure 1-9 indicates that only 30"/o of the trans­ 49% missions showed proper selection of carrier. Some WITHIN 5 Hz OF of these were too far out of tolerance to permit SELECTED CARRIER synthesized reception of signals. The remaining 7f1'/o indicate either personnel error or equipment (GOOD COPY) malfunction. Figure 1-10 indicates equipment accuracy. Transmitter and receiver frequencies which differ by more than five hertz result in degraded copy. Beyond ten hertz differences, the termination is useless. Note that 40"/o of the transmission were beyond limits and required AFC controlled receivers· which require that a pilot carrier be transmitted in addition to the tones. This results in improper mode 40% of transmission, and also utilizes power which could GREATER THAN 10 Hz otherwise be conveying intelligence. FROM SELECTED CARRIER (USELESS)

54o/o IMPROPER SELECTION Figure 1-10. Frequency Accuracy of Transmitters (VFTG Terminations) OF CARRIER FREQUENCY Because of limitations on crypto equipments, traffic handling capability, teletype machines, and personnel, a ship normally utilizes only four intelligence channels (eight tones). The remaining tones for the unused channels of the AN /UCC-1 serve no useful purpose. The blocking mode of operation (sometimes called "idling") can often be employed in multi­ 30%CARRIER channel operation over VFTG circuits to overcome PROPERLY OFFSET slow fading, weak signals, or noise which may not permit operations in the twining mode. Blocking is accomplished by inserting dummy plugs into the tone equipment jacks or grounding the output of each separate transmit channel as required. By holding transmission an given channels, the transmitted power used in these channels is concentrated in the channels still in use. The number of channels blocked depends upon the conditions of the frequency Figure 1-9. Selection of Proper Carrier Frequency or frequencies in use at the time.

Vari able Frequency Tone Group (VFTG) CAUTION g. TONES AND VFTG CIRCUITS When blocking or idling is employed, be The tones generated by an AN/UCC-1 VFTG sure to readjust the input levels to the send terminal, or the AN/FGC-60 equivalent shore transmitter to maintain peak output pow er. send terminal, cover the audio frequency range of The transmitter output is directly related 382. 5 Hz to 3017. 5 Hz . Normally, two tones are to the audio input power. utilized for each intelligence channel to give close frequency diversity, thereby decreasing the effects During periods of marginal communications, of selective fading. The AN/UCC-1 then, normally tones should be blocked to obtain the following has an 8-channel intelligence capability with 16 tones. advantages: The pairs of audio tones used on a given intelligence 1. Slightly more power "per tone channel" channel are separated by 1360 Hz. can be transmitted without over loading the transmitter.

ORIGINAL 1-23 . . I' .. - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

This is only a very slight increase in power and The package of tones that originates in the care must be given to ensure that the transmitter MUX unit ashore has 425 hertz as the lowest fre­ is not overdriven to the point that distortion takes quency tone, and tones are present every 170 hertz place, Readjust levels at the AN/UCC -1 and check up the audio frequency spectrum, with a tone of transmitter to ensure it is not being over modulated. 297.'i .Hz as the highest frequency audio tone. There 2. With fewer tones being transmitted the are 16 tones for the 8 or 16 channels of intelligence chances of shipboard generated radio frequency that are normally transmitted on MUX circuits. interference are decreased. Also, the chances of These tones are transmitted as audio modulation to intermodulation distortion are decreased tremen­ a single sideband suppressed carrier transmitter and dously as far as the number of byproducts math­ are radiated as the upper sideband of the transmitter. ematically available are concerned. Assume that the assigned frequency for radiation of 3. Decreased bandwidth also lessens the MUX is 4905 kHz; the frequency is cleared for a chances of interference on other ships using adpcent three kHz bandwidth so the tone must straddle the channel operation. By blocking the higher audio center frequency or assigned frequency (4905 kHz) frequencies from the tone package, a "guard ba nd " in this case). The to nes occupy roughly 3000 Hz is placed between this tone package and the next (3kHz ) of the spectrum. In order to straddle the higher channel frequency. This causes less inter­ assigned frequency with these tones, the suppressed ference throughout the fleet. carrier on the transmitter must be placed l.5 kHz If the front end (on the receiving end of the below the assigned frequency. In the assumed case, circuit) is driven into the non-linear area of con­ the frequency assigned is 4905 kHz and the suppressed duction, the fewer tones in the tone package will carrier is placed 1. 5 kHz below that, or at 4903.5 kHz. result in fewer by -products being generated within When this suppressed carrier is modulated by the the receiver. 425 hertz (low est frequency of the MUX tone), the Tone blocking should be practiced until it two frequencies are added, and that 425 hertz tone becomes normal operation. It makes good common is radiated at a radio frequency of 4903. 925 kHz sense to only transmit the tones that are used to (4903. 5 plus 0. 425). The highest frequency aucio convey intelligence and to block the unused tones. tone is 2975 Hz or 2. 975 kHz and, when it is modu­ It must be remembered that channels 1, 2, 3, lated in the transmitter, its output frequency becomes and 4 are not the only channels that can be used for 4903. 5 plus 2. 975 or an RF frequency of 4906. 475 terminations. In some cases, it may be advantegeous kHz. The audio tones for the other channels are in to utilize channels 5, 6, 7 and B. Any combination between these two RF frequencies. of channels may be used. Untwineing can also With suppressed carrier single sideband type increase the number of channels available for ships of transmission, the receiver picks up the individual that only have a fo ur-channel capability. Initiative channel frequencies in one package, but has no and a desire to communicate should be the guiding carrier frequency in the package to use as a refer­ doctrine in the use of VFTG MUX equipment. ence. The "carrier" frequency is actually generated (E1B 718) and injected into the package of tones within the receiver on board ship. Tuning the receiver pro­ h. TUNING MUX (MULTI -CHANNEL) duces this inj ected carrier into the tone package CIRCUITS and then the tone are detected (demodulated) and Multi-channel circuits permit more than one appear as audio. This is fed to the AN/UCC-1 channel of intelligence to be transmitted and re­ equipment for conversion into teletype signals. ceived over one frequency. Only one transmitter With the receiver on the correct frequency, and one receiver are necessary at each end. In listen to the audio and make sure that the frequency ship/shore terminations, one additional transmitter is clear, with little or no noise for interference. and receiver are used to give better reliab ility, Try several antennas and patch cords to obtain the although one receiver will operate the circuit. In strongest and clearest reception possible. If the broadcasts, the shore station runs many frequencies receiver has an antenna tuning device, be sure and in order to provide reception to ships all over the peak thi s for maximum received signal. If the area of responsibility for that particular shore signal is extremely strong, decrease the amount of station. radio frequency gain so that the AGC action of the The single channel radio teletype signal has a receiver will not distort the audio output to the re­ shift of 850 hertz and can be readily tuned in on ceiver. Adjust the audio level out of the receiver practically any receiver with just a little care. If to the correct level for the input of the device used the audio from the receiver enters the teletype con­ to convert the audio tones to teletype signals . verter at slightly different frequencies than those Normally, this will be an AN/UCC-1 equipment. for which the converter is designed, the circuit will Adjust the level out of the receiver after the patches probably operate QRK 5 anyway. In multi -channel have been made to feed the signals into the AN/UCC-1. (MUX ) operation, the shift on each channel is only Keep a second receiver tuned in to another 85 hertz-one tenth the shift that single channel frequency on either broadcast or ship termination radio teletype circuits use. These circuits are type circuits to give an instant back-up if one fre­ much more critical and difficult to tune. The result quency fails or a transmitter goes off the air at the of a frequency error on multiplex is ten ti mes more shore station. Keep an audio monitor on the two critical than would be indicated by the difference in frequencies to make sure that they are both of the amount of shift. As an example, a frequency traffic quality at all times. If one frequency goes error of 500 hertz on FSK will introduce approxi­ bad, QSY the receiver to a new frequency before mately 5% distortion to the copied signal; a frequency the other frequency also goes bad. If tw o signals error of only 5 hertz in MUX operation will introduce are found of the same quality, the AN/UCC-1 this same 5% distortion.

ORIGINAL 1-24 I' ...... -. ...- ... - ... -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

equipment can be set up for receiving and comparing were perpetually asked by the carriers to perform both of these frequencies in frequency diversity. In relay duties. So many of the new arrivals lacked order to use this mode of operation, the AN/UCC-1 the ability to conduct a successful relay that the must be set up in accordance with the technical Fleet Commander called for command attention and manual and, additionally, both frequencies must insisted on performance. Henceforth each destroyer either be broadcast from the same transmitting must not only demonstrate a relay capability commen­ location or locations that are the same distance from surate with its existing transmitter installation but the ship. a proficiency in relay as well. Carriers have been Not all receivers on board ship will operate asked to rotate the relay assignment among the efficiently on MUX signals, as the receivers tend to destroyers attached and to report inabilities on the drift in frequency. They will drift only a few cycles, part of any of them. The carriers are beginning to but that may be enough to highly distort a circuit. realize that a 2100 ton class destroyer is incapable The receivers commonly used now for MUX signals of providing the same degree of relay services as are the R-1051/URR, AN/WRR-2, and the AN/SRR-19. the DLG class because of the obvious disparity of The AN/WRR-2 receiver cannot be used on frequen­ equipment. However, this does not exonerate the cies where the carrier must be injected at half kHz 2100 ton class destroyer from demonstrating a pro­ points, unless Field Change I has been applied. The ficiency in each of the modes if her communications other receivers on board ship, such as the R-390/ installation includes the proper types, not numbers, URR, are not suitable for MUX operation unless in of equipment. an emergency. Relay capability in each of the following modes The signal pulses on diversity channels (twinned should be established: pairs) must arrive simultaneously at the terminal Single channel VOX relay Consists of convert­ equipment in order that the channels (4 on Quad Diver­ ing UHF AM voice or tone-mode teletype signal to sity) may be used in diversity operation. Errors in HF using the C-4621 /SR retransmission unit. arrival time ( 1 to 5 milliseconds delay distortion) Double channel simultaneous VOX relay were introduced by .t he shore transmitting stations Consists of converting two UHF AM or tone-mode during operation BASE LINE II. Because of this (AFSK) teletype signals to an HF SSE voice or tone­ delay, compensation at the receive MUX terminal mode teletype signal using the C-4621 /SR unit. should be made while receiving the desired station. Single channel VOX relay on single sideband The procedures in the AN /UCC-1 Technical Manual Consists of converting an UHF AM voice or tone­ require that the transmit station send reversal type mode teletype signal to an HF SSB voice or tone­ signals during alignment of the equipment with the mode teletype signal using the C-4621/SR unit. test set provided. This procedure is not always Independent sideband two channel VOX relay possible, especially on broadcast circuits; however, Consists of converting two UHF signals, one voice the adjustment can be made while traffic is being and the other tone-mode teletype to one HF upper passed by measuring delay between channels with sideband voice and lower sideband tone-mode tele­ a dual trace oscilloscope. type using the C-4621 /SR unit. The signal pulses arriving at the KW -37 Composite (2 or 3 channel) MUX relay Con­ broadcast channel must arrive simultaneously with sists of converting a UHF composite MUX signal to each of the pulses on the associated KG-14 channels an HF composite MUX signal on a sideband using for proper operation. The KG-14 has a variable the C -4621 /SR. delay switch which can be used to compensate for Single channel frequency shift teletype relay known delay differentials. The alternate procedure Consists of converting an UHF tone-mode teletype is to compensate for all delays at the MUX receiving signal to a HF frequency shift signal using the terminal. It is not feasible for a shore broadcast AN/SGC-1A. station to transmit reversal type signals to permit Diversity frequency shift teletype relay adjusting channel delay with the test set provided Consists of converting a single UHF tone-mode with the AN /UCC -1 equipments. The adjustment teletype signal to one HF frequency teletype and or measurement of delay distortion must therefore one MF frequency shift teletype signals using the be made while traffic is being passed by measuring AN/SGC-1A. delay between channels with a dual trace oscilloscope. A MUX relay in frequency shift mode is diffi­ The difference is delay distortion between cult to manage because of the slow response of the twinned broadcast channels and associated KW-37 mechanical relay in the AN/SGC-1A. An electronic and KG-14 broadcast channels should be fairly relay replacement to remedy this deficiency is bei ng constant throughout each broadcast area. These considered at this ti me. delays will very likely be different between one The most common error is the mistaken beli ef broadcast area and another until broadcast stations that the VOX (C-4621 /SR) can drive a frequency develop procedures and equipment capability to shift keyer. The VOX unit can handle only audio standardize on synchronization, (EIB 719) signals and drive a modulator. However, the AN/ SGC-lA teletype tone modulator can convert the i. UHF /HF RELAY tone-mode teletype audio signal into the mark and The communications duties of destroyers space bits to key the DC loop of a frequency shift include providing the carriers with UHF /HF relay, keyer. Upon learning that the AN/SGC -1A is not only during HERO and RADHAZ conditions but necessary to convert a tone-mode teletype to fr e­ for sustained periods of time. In the past, only the quency shift, many ships find that they are unable to destroyers homeported in WESTPAC together with isolate the AN/SGC-1A in the teletype DC loop board. a few ships deployed to WESTPAC had worked out Both the frequency shift keyer in the transmitter and the details of VOX relay, and these "old reliables" the tone modulator have their own DC loops, and

ORIGINAL 1-25 ...... - ... - ...- ...-

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

two power supplies won't work. There are several 2. Adjust transmitter mode level on trans­ solutions to this problem but the one in COMFIRST ­ mitter control C-4621/SR to zero dB on level meter. FLT TACNOT E 1-63 which suggests isolating the 3. On transmitter, lock on carrier test key AN/SGC-lA in the miscellaneous jack is probably and adjust audio output of previously de signa ted the simplest. Those ships that still have the TT-23 sideband . panel with its very versatile feature of the toggle 4. The AN/WRT-2 should now indicate approx­ switches don't have thi s problem. imately 120 watts on the output meter. Failure to modify the C-4621/SR as authorized Periodic checks and adjustments of the UHF by Field Change 1 to permit duplex operation limits receiver audio output are necessary to compensate the capacity of some ships. for the effects on signal strength and distortion when Upon receiving a request from a carrier to changing bearing and distance to the ship of signal relay a two or three channel MUX signal, several origin. (EIB 741) destroyers have originated messages to the TYCOM requesting that MUX equipment be installed at the 1-6 TRA NSMITTING EQUIPMENT earliest possible time so that this service might be Transmitting equipment includes RF sources rendered. MUX relay requires no MUX equipment. and modulators, in addition to transmitters. The Successful UHF /HF relays of multiplex signals simplest practicable transmitter for CW trans- should use the following procedures: mission consists of a pow er supply, an oscillator, Upon receipt of a condition one voice message an RF amplifier, as shown in the block diagram of on the COMM COOR D net: Figure 1-11. A more typical transmitter, with 1. Inactivate clipper-filter circuits of the UHF heavy lines showing the functions required for CW transmitter. operation, is shown in the block diagram of Figure 1-12. 2. Tune a UHF receiver to frequency designated. A CW transmitter can be transformed to a 3. Tune AN/WRT-2 or similar transmitter as radiotelephone, or phone, transmitter by the addition follows: of a modulator, shown in dotted lines in Figure 1-12. Although the modulator, frequency source, and power NOTE supply are usually parts of the transmitter, typical AN/URC-32 is not considered acceptable malfunctions involve only one of these at a time. for relay Troubleshooting them is simplified because the mal­ functioning section of the equipment can be troubleshot Step a. Tune transmitter as usual to fre­ as a separate equipment, aside from power require­ quency designated in condition message. ments . Preliminary troubleshooting procedures are Step b. Set EMISSION selector to USB. given first and then procedures for transmitters, RF Step c. Set CARRIER REINSERT to -10 dB sources, and modulators, which are followed by or as indicated in condition message. procedures for single-sideband transmitters. Power Step d. Set SIDEBAND SELECTOR to supply troubleshooting procedures are given in sideband indicated in message. Subsection 1 -7. 4. Patch UHF receiver to transmitter VOX control C-4621/SR. a. MALFUNCTION INDICATION 5. Patch AN/WRT-2 or other transmitter to Navy transmitting equipment is provided with transmitter VOX control C-4621 /SR. meters to enable each equipment to serve as its ow n 6. Transmit condition one voice message test equipment. By using th em, the technican can Upon receipt of condition three voice message: determine what area of the circuitry can be respon­ 1. When tones are heard in UHF receiver, sible for a given malfunction. These indications are adjust its audio output to ±2. 5 dB. THIS LEVEL used extensively in the troubleshooting procedures MUST BE MAINTAINED. following and enable much equipment performance to

: ; I POWER TO OSCILLATO R ANPLIFI ER AN TENNA

POWER

SUPPLY

Figure 1-11. Simple Tra nsmitter, Block Diagram

ORIGINAL 1-z6 ...... -,-. ...- ... - ... -

COMMUNiCATIONS NAVSEA 0967-LP-000-00i O GEi�ERAL

FREQUENCY SOURCE

BUFFER BUFFER OSCILLATOR MULTIPLIE R � IPA � r-. AMPLIFIER f----. AMPLIFIER � t r----, POWER AUDIO 1 I POWER TO __..... MODULATOR SUPPLY �INPUT t------AMPLIFIER ANTENNA 1 1 L ____ _.J

Figure 1-12. CW and Phone Transmitter Block Diagram. (Components Needed for CW Operation in Solid Lines).

be evaluated without removing a chassis from the Step Indication Action cabinet. no operation, operation at reduced power, inabi ­ b. PRELIMINARY TROUBLESHOOTING lity to tune or load at a PROCEDURE required frequency, Perform the appropriate steps in the following inability to modulate procedure if the approximate location of the ma l­ properly, etc . function is unknown. Use of this procedure will c. Malfunction found Inspect bandswitches for result in the correction of the malfunction or identi­ only on one band correct action in opera ­ fication of which procedures to use in further trouble­ or channel. tion and proper adjust­ shooting. ment and clean contacts; clean, adJust, and Step Indication Action replace as needed to a. Transmitter gives Verify that power obtain correct operation. no indication of switch is in correct The visual inspection being energized. position. with equipment deener­ Check line cord and gized should be followed plug for condition by a measurement of all and correct inser­ voltage values affected tion. Check the fuses by switching with equip­ and replace blow n­ ment energized. Inspect out ones. and test components and connections switched in b. Transmitter is Verify that all dial when malfunctioning band energized but and switch settings or channel is selected. correct operation are correct. If this is not effective, is not obtained. If panel meters do set the equipment to the not indicate the pre­ malfunctioning band and sence of the correct continue with Step d. power supply voltages, use the pow er supply d . Malfuncti on found Inspect all function­ troubleshooting pro­ only on one func ­ selection switches for cedures of Subsec­ tion (or several correct operation, proper adjustment, and tion 1-7. related functions). At this time, deter­ clean contacts; clean mine in what way and adjust, and replace as on what functions (CW, needed to obtain correct SSB, PHONE, etc. ) operation. If this is not operation is impaired. effective, inspect the Determine if it affects condition of and test the only certain bands or operation of all circuitry channels. Further switched into the circuit define malfunction as in the malfunctioning

ORIGINAL 1-27 ...... ,. ,- ,- ,.

COMMUNICATIONS GENERAL NAVSEA 0967-LP-000-0010

Step Indi cation Action NOTE In tes ting tubes, return each good tube positions . This will to its ORIGINAL socket after testing. include, for example, Replace defective tubes but keep in STA NDBY, TUNE, service tubes that test slightly low. PHONE, LSB, etc . If Test- substitute a new and tested-good this is not effective, tube for one of questionable condition, set the equipment for but return it to stock and the old tube the ma lfunctioning to the socket if the substitution does not operation and perform improve the performa nce of the equi pment. the following procedures where appropriate. CA UTION Observe all safety precautions, being e. Transmitter can­ If no IPA drive is sure to deenergize the equipment before not be tuned to a measured or if the fre­ removing a chassis and to discharge all desired frequency. quency sour ce cannot filter capacitors before working on a be tuned, follow the chassis. In making resistance measure­ troubleshooting pro­ ments, discharge all capacitors that cedures of Subsection could affect measurements or damage 1-6, RF, Oscillator or the ohmmeter. Frequency Source Mal­ functions. If the IPA Step Indication Action cannot be tuned, fol- low the instructions a. PA PLATE CUR­ Verify that all dial for Subsection 1-6, RENT is not nor­ and switch settings Transmitters. If the mal. are consistent with PA cannot be tuned or known preliminary loa ded properly, fo l- of calibrated settings. low the instructions Verify that the IPA for Subsection 1-6. grid drive can be ad­ Tra nsmi tte rs. justed pr operly and f. The ANTENNA If the MODU LATOR then make the follow­ CURRENT meter CURRENT meter readc ing adjustments . IPA indicates the pr e­ ing is normal and tank, PA EXCIA TION sence of a carrier fluctuates with varia­ or GRID DRIVE, PA but does not indi ­ tions in input, perform TUNING, AND LOAD­ cate any pow er due Step b of Subsec tion ING. to modulation. 1-6, Modulators. If b. PA PLATE CUR­ Test- substitute new PA the MODULATOR RENT is not nor­ tube( s) and try retu n­ CURRENT indi cation mal, but PA GRID ing. is abnormal; if modula ­ DRIVE is normal. tion contains hum, dis­ Test substitute dummy tortion, or noise; or if antenna at transmitter undermodula tion occurs, output or new tra ns­ follow the appropriate mission line and new steps of Subsection 1-6, antenna. Inspect and, Modulators. where necessary, clean and adjust tank It is assumed that thi s or a similar proc edure and coupling circuitry, will be used to determine the approxi mate location switches, and antenna of the malfunction and the appropriate steps to deter ­ relay. Test-substitute mine the approximate location of the malfunction and new coaxial links if the appropriate steps to be used of the sy stematic malfunction continues. troubleshooting procedures following. c. IPA GRID DRIVE Test-substitute new and PLATE are PA tube( s) and test c. TRANSMITTERS normal but PA transmitter operation. Perform the appropriate steps in the following GRID DRI VE or Return original tube( s) procedure if the malfunction is thought to be in the GRID CURRE T to equipm ent if sub­ transmitter IPA, PA , or following (coupling and are abnor mal. stitution does not im­ antenna ) circuitry. Test transmitter opera tion fo l­ prove operation. lowing any change (repair, replacement, or adjust­ Inspect and, if neces­ ment) to ascertain if normal operation has been sary, clean and adjust restored. contacts of all associ­ ated switch es. Test condition of all com­ I ponents in network between IPA and PA .I stages.

l-28 ORIGINAL COMMUNICATIONS NAVSEA 0967-LP-000-00iO GENERAL

Step Indication Action Step Indication Action

d. IPA GRID DRIVE Test-substitute new IPA the technical manual to normal but IPA tube(s); return original identify possible defec­ PLATE CUR­ tube(s) to equipment if tive components; re­ RENT abnormal. substitution does not im­ place any defective prove operation. De­ components. termine the condition d. Same as Step a, If the previous steps of all switches and except switching, have been ineffective, other components as­ crystal, and oscil­ set band switch or sociated with IPA lator tubes pre­ channel selector to a stage, especially in sumed good. resonant network, malfunctioning position coupling it to PA input. and follow trouble­ shooting steps appro­ (1) RF Oscillator or Frequency Source priate for the type of Malfunctions malfunction encountered . Use the appropriate steps in the following procedures to correct any malfunctions in the RF (3) RF Output is Abs ent from Frequency oscillator, whether crystal-controlled or LC -controlled. Source Due to the wide variety of configurations and Use the appropriate steps among the fol­ circuits used in RF oscillators, the following trouble­ lowing if no RF from the frequency source is found shooting steps have been broken down to cover specific at the IPA stage. conditions rather than type of equipment. The mal­ functions covered are no RF output, low RF output, Step Indication Action and off-frequency RF output. Frequency synthesizers are so complex and of such differing configurations that a. No RF present Use an oscilloscope that this chapter does not attempt to give a trouble­ at IPA stage. or wave-meter to verify that the desired shooting procedure for them. The general steps that RF is not present at apply to them, as well as to all other electronic equip� the input to the IPA or ment, are given in this section; the ET is referred to at the output of the fre­ the appropriate technical manual for detailed trouble­ quency source. Check shooting procedures. continuity of cables, (2) RF Output is Unsatisfactory on Only connectors, and switches ; One Band or Channel Use the following steps if a malfunction of any if it is present at the kind is experienced on one band, or one or a few chan­ frequency source output nels, in the operation of a band-switching or channel­ but not at the IPA. switching frequency source. b. No RF present Test all tubes of fre­ Step Indication Action at output of fre­ quency source on a quency source. tr ansconductance tube a. Impaired operation Inspect action of band- checker. Discard on one (or a few ) or channel-switches those tubes which show bands or channels, visually (equipment a transcanductance aracterized by no, ch deenergized) and value less than half of low, or off-frequency electrically (equip- the normal value or have output. ment energized). internal short circuits. Verify that switching Return each acceptable action is correct. tube to its original Clean and adjust socket and replace contacts. discarded tubes with b. Same as Step a, Test-substitute new tested-good ones. except switching oscillator tube. Also, c. No RF output Test-substitute a new action acceptable. if frequency is crystal­ from frequency crystal of a nearby controlled, test-sub- source; tubes frequency for each stitute new crystal of good. crystal in the frequency similar frequency. source. c. Same as Step a, Verify (by VTVM or d. No RF output Use a VTVM or an except switching, oscilloscope) that from frequency oscilloscope to trace crystal, and oscil­ oscillator stage has no source; tubes the RF signal from lator tubes pre­ output on malfunction­ and crystals good. the oscillator to the sumed good. ing band or channels. point where it cannot Make oscillator socket be found. Start with voltage and resistance the oscillator plate and measurements; compare trace the signal to each values found with following plate. When normal ones given in the signal is lost at a

ORIGINAL 1-29 . .

.. - .. - .. - .. -

COiviiviUNICA TIONS NAVSEA 0967-LP-000-001 0 GENERAL

Step Indication Action Step Indication Action

plate, determine if it limits - under no is present at the grid circumstances below of that stage; if not, it 10. Test suspected is lost in the resonant components by replac­ and coupling circuitry ing them in the circuit. preceding. If the RF signal is found at the ( 5) Output of Frequency Source is Off grid, it is lost at the Frequency tube; substitute a new Note that the following steps are identifi ed tube and make tube­ as being appropriate for large and small fr equency socket voltage and errors, respectively. Large errors are considered resistance measure­ to be those producing output at the second harmonic ments to components and above. Use the appropriate steps for the mag­ found. nitude of the frequency error; note that small errors may remain after the large ones have been corrected. (4) Output of Frequency Source is too Low in Amplitude Step Indication Action Use the appropriate steps among those following if the RF output of the frequency source is a. Frequency source Use a frequency meter too low in amplitude to drive the IPA properly. output apparently series or equivalent in error. to determine the out­ Step Indication Action put frequencies. De­ termine from this data a. RF output of fre- Test all tubes of fre- the magnitude and quency source too quency source and any extent of the errors, low in amplitude. associated in the power their amount, and what supply on a trans - band or channels they conductance tube influence. checker. Discard b. Frequency source Retune the frequency those tubes which output is a harmo- source, starting each show a transconduc- nic of the indicated adjustment from its lance value less than frequency. low-frequency extreme half of the normal (capacitor fully en­ value or have internal meshed ) and peaking short circuits. Re- or dipping it at the turn acceptable tubes first indication of to their original reasonance. sockets and replace discarded tubes. c. Frequency source Determine for a test b. RF output of fre- Use the techniques of output is a harmo- setting what should be quency source too Step d RF Output is nic of the indicated the frequency of the low in amplitude, Absent from Fre- frequency. signal at each stage but tubes good. quency Source, to of the frequency source. identify any amplifier Measure the frequency stage failing to pro- at each stage with a duce the required gain frequency meter and or any other stage compare the measured causing undesired and computed values attenuation. Some for each stage to loss should be expected determine where the in passive circuitry undesired harmonic (RF transformers originates. Determine and networks), but the condition and Q amplifiers and mul- of the resonating and tipliers should show filtering components some gain. Cathode involved. Make tube followers should show socket voltage and a slight voltage loss. resistance measure­ ments at that stage to c. Abnormal atten- Disconnect the sus- locate any components uation found in an pected components resulting in incorrect RF transformer or from the circuit and operating conditions. resonant circuit. test. Verify that the d. Undesired fre- If the basic frequency Q in inductors or quency multiplica- is crystal-controlled, assembled networks tion occurs in test-substitute known is within reasonable

ORIGINAL 1-30 ...... - .. - ..- .. -

COMMUNlCA TlONS NAVSEA 0967-LP-000-0010 GE:NERAL

Step Indication Action Step Indication Action

frequency source; good crystals of the any type of ambient temperature all components same or nearby fre­ frequency source. and cabinet or console apparently in good quencies. If this is placement permit cor­ condition. not effective or ap­ rect cooling. Correct plicable, try the fol­ any conditions respon­ lowing changes, in sible for poor cooling. order: g. Frequency error If output is crystal­ 1. Test condition of is relatively small; controlled, test­ frequency-controlling equipment cooling substitute a known or filtering components. is satisfactory. good crystal for the original one. If this 2. Place a tube is not effective (or shield around the in LC -controlled oscillator tube if it equipment), make os­ does not already have cillator socket voltage one. and resistance measure­ 3. Place experi­ ments to locate any mental shielding components that may be around oscillator stage causing incorrect tube circuitry. Check lead operating conditions. dress, particularly if Replace any such it appears to have components. been altered. h. Frequency error Make calibration adjust­ 4. Determine the remaining is small ments on oscillator condition of all fila ­ enough to be due trimmer capacitor, us­ ment and screen by­ to cumulative re­ ing an accurately cali­ pass capacitors at sults of component brated LR-series fre­ frequency source aging. quency meter as a stages. Add them, standard. LC-con­ where not already trolled channels are included in the cir­ calibrated by alignment cuitry, between these of one of the resonant points and ground; components. Each disk ceramic ca­ continuously variable pacitors of 0. 005 pF band is calibrated by and a high enough a trimmer capacitor at voltage rating for the the high frequency end specific application and a padder capacitor are satisfactory. or variable inductance e. Frequency error . Check oven thermo- at the low frequency is relatively small stat and heater oper­ end . The appropriate and originates at ation. Monitor heater technical manual for oven-enclosed current and oven tem­ the equipment gives crystal. perature, if necessary detailed alignment and to verify that cur rent calibration adjustments is at a maximum value in each case. until output tempera­ ture is reached, follow ­ (6) Frequency Errors Originating in Fre­ ing which it is inter ­ quency Synthesizer mitten\ and cyclic Many newer transmitting equipments around an equilibrium provide frequency selection by switch control of a value. Make adjust­ frequency synthesizer. This provides for mixing ments for correct the desired outputs of harmonic generators and equilibrium tempera­ frequency dividers, which are driven by a stabilized ture, if necessary and master oscillator. Since this equipment is complex possible, or replace and takes many forms, it is suggested that the ET any defective compon­ called on to service it perform only Steps a and b. ents - thermostat, Step c and d should not be performed by shipboard heater, or entire personnel except in case of emergency. Steps c and assembly, if ne cess­ d normally should be performed by tender personnel ary. or a shore facility. f. Frequency error Verify that the trans­ is relatively small mitter blower (if and originates at provided) is operat­ ing and that the

ORIGINAL 1-31 .. - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action a. Output of frequency Test all tubes on a obtained by addition synthesizer known transconductance tube of 1.0 MHz to the ap­ to be off frequency. tester. Tubes having propriate even multiple. a transconductance at Conclusion: Any stage least half of the normal generating or handling value and no internal the 1-MHz signal could shorts should be re­ cause this error. turned to their original d. Frequency syn­ sockets. Replace all Set frequency synthe­ thesizer known other tubes with new sizer for a known erron­ off frequency; ones. eous output. Determine possible sources what frequencies b. Frequency syn­ Make tube socket of error indenti­ should be present in thesizer known voltage and resis­ fied. each of the potentially to be off fre­ tance measurements defective stages. Use quency; tubes to locate defective the frequency meter known good. components that alter or frequency selective operating conditions; voltmeter to measure replace such defec­ the frequency present tive components. in each of these stages c. Frequency syn­ Use an accurately until the malfunctioning thesizer known to calibrated frequency stage is found. Make be off frequency; meter to compare the tube socket voltage and tubes and operat­ synthesizer output resistance measure­ ing conditions with the frequencies ments at this stage and known acceptable. indicated by its control replace any defective settings. Tabulate components found in the amount of the error this manner. If the for each frequency at defective stage func­ which error is found. tions as a frequency Then use the equip­ divider or multiplier, ment schematic or make the time-constant block diagram to or resonance adjust­ locate the stages which ments given in the could cause the errors equipment's technical noted. This is an manual for this stage, analytical process, two whether component examples of which replacements are ma de follow. or not. Example 1: Condi­ tion: Signals with (7) Frequency Control Circuit Malfunctions 900 kHz in their fre­ Frequency control circuits are included in quency designation some RF sources to lock the basic frequency setting ( 1. 900 to 1. 999 MHz, so that one of its derivatives coincides with a deriva ­ 2. 900 to 2. 999 MHz, ' tive of a reference frequency. This circuitry may be etc. ) are all supplied located in a hermetically sealed and temperature­ 100 kHz low. Stipula­ controlled enclusure. Because of the complexity of tion: The 900-kHz the circuitry, the technician is advised to perform component is supplied the following steps first in case of malfunctions by a single frequency performing the procedures given in the technica'l divider. Conclusion: manual for the equipment only in case of emergency Malfunctioning of this or if he has experience with this equipment. divider could result in the error noted. Step Indication Action Example 2: Con­ dition: Frequencies a. Frequency control Test all tubes of fre­ containing odd mul­ circuit malfunc­ quency control circuit tiples of 1 MHz are tioning. on transconductance supplied I MHz low in tube tester, returning to their original sockets the output, duplicating the lower even­ those tubes showing a transconductance at multiple range ( I.9 least 50 per cent normal MHz being supplied as and having no internal 0. 9 MHz, for example). shorts Stipulation: Odd mul­ tiples of I MHz are

ORIGINAL 1-32 ..

COMMUNICATIONS NAVSEA 0967-LP-000-00i O GENERAL

Step Indication Action in the output. The narrow -band filter removes the lower sideband, passing only the sum frequencies. b. Frequency control Make tube socket volt­ The oscillator and intermediate frequencies are circuit malfunc­ age and resistance specified in equipment design to facilitate sideband 'tioning; tubes in measur ements to locate selection in the first filter and pa ss any of the desired good condition. any defective com­ RF output frequencies through the second filter. The ponents; replace any amplifiers used in this circuitry must be linear found. Note that pro­ amplifiers- class A, class B, or a combination - as cedures in the appro­ opposed to the class C stage commonly used as the priate technical man­ power amplifier for A3 transmission. ual must be followed All techniques for generating a SSB signal are in establishing condi­ similar in that the audio component is heterodyned tions for the measure­ with an RF signal at a relatively low power and ments. frequency level. Therefore, mixing (heterodyning) rather than multiplication techniques must be used to obtain the final radio frequency. d. SINGLE -SIDEBAND TRANSMITTERS (2) Single-Sideband Adjustments. Only one side band and no carrier (normally) Single-sideband techniques depend on the is used for single-sideband (SSB) transmission. accuracy and stability of oscillator and filter adjust­ Specialized modulating and transmitting equipments ments. These and modulator balance adjustments are needed for this type of transmission. Some should be made, if necessary, after replacement of transmitters have been modified for SSB transmission, an oscillator or modulator tube. but all new SSB transmitting equipment is in the form The adjustments found in SSB transmitters, of transmitters, rather than adapters. along with the purpose of each and the method of de­ termining correct adjustment, are listed in Table 1-5. ( 1) Theory of Single-Sideband Transmission. Not all of these adjustments are found on every SSB Several methods of obtaining SSB modula­ transmitter, but many of them, plus the conventional tion have been devised, the most common one (Figure transmitter drive, tuning, and loading adjustments, 1-13) using balanced modulators (Figure 1-14). Such are part of every SSB transmitter. The letter circuitry and the heterodyning procedures used designating each adjustment is given in Figure 1-13 to differentiate SSB transmitters from conventional A3 show where the adjustment is located and also in transmitters. The first balanced modulator show n referring to them in the troubleshooting procedure. in the example mixes audio (voice) with a 1.5 MHz RF The unlettered adjustment of carrier reinsertion signal to obtain only the sum and difference frequencies amplitude is found only in Independent Sideband (ISB ).

TABLE 1-5. TYPICAL SSB ADJUSTMENTS

Adjustment* Adjustment of Effec.t of Adjustment Correct Adjustment Indication

A Audio input Permit desired RF output AC voltage at input level

B First Injection Permit retention of desired sideband Calibrated receive r or' frequency frequency and determine output frequency meter at buffer amplifier output

c First Injection Permit optimum powe r-handling and RF voltage at balanced modulator signal amplitude output input

D First modulator Minimize carrier in output Calibrated receive r or field strength balance meter

E Sideband rejection Pass desired sideband and reject Calibrated receiver or field filter bandpass c... �er strength meter

F IF buffer ampli­ Permit optimum power-handling and AC voltage at buffer amplifier fier output level output (control sideband power in output ISB operation

G Carrier reinser­ Control pilot carrier amplitude Calibrated receiver or field tion amplitude strength meter

H Second Injection Determine output frequency-may Calibrated receiver or field frequency be calibration for band tuning or strength meter adjustment for channel selection

Bandpass filter Rejection of undesired frequencies Sweep generator and receiver, or receiver

J RF output Permit optimum power-handling R F voltage at buffer amplifier amplitude and output output

*Adjustment Designations are keyed to Figure 1-13.

ORIGINAL 1-33 I,

0 AUDIO I ST. 2 NO. n :::0 SIDEBAND BUFFER BANDPASS 0 ...... AMPLIF ICATION BALANCED 1.498 TO BALANCED �: Ci> FILTER AMPLIFIER FILTER $ ...... AUDIO STACES 0 TO MODULATOR 1.5MHz 1.5 TO 1.5 TO MODULATOR 5.5 TO c: z INPUT 2kHz AND 1.502MH .502MHz .502MHz z � )::> r.· r (0 TO 1.5 TO :J>· ,_; 2kHz) 502MHz %cv %CD E .. z ~ ~ ~ u: ~ I;

I.S MHz 4 TO G MHz

z BUFFER BUFFER )::> < Vl AMPLIFIER AMPLIFIER ITl B� FFER )::> 0 AMPLIFIER 1.0 - ()) I ...... , I, w .. I I ""0 ~ I 0 0 0 I POWER 0 4 TO GMHz LS MHz � 0 (VARIABLE ) __, SUPPLY 0

I ST. RF 2 NO. INJECT ION INJECTION LINEAR

NOTE : SEE TA BLE I · 5 FOR FUNCTIONS FREQUENCY FREQUENCY AMPLIFIER T6 OF ALIGNMENT- ADJUSTMENTS I, OSCI LLATOR OSCI LLATOR AN TENNA INDICATED BY CIRCLED LETTERS. ;Vcv ;t!® Q)

0 t'l z t'l ::u 1-13. ;I> Figure Single-Sideband Transmitter Block Diagram. l'

.. I' ...... ,- ,- ,- ,-

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

RF AF OUTPUT INPUT RF c :J INPUT

8+

SCREEN BIAS

Figure 1-14. Balanced Modulator Circuitry

The procedures and indications for the adJUSt­ appropriate steps and test transmitter operation, ments of any specific SSB transmitter are given in either overall or at the point under study, following the technical manual. any change made in it. Adjustments required are No adjustments should be made until the equip­ identified by the letter under which listed in the table ment has been installed and energized for a sufficient of SSB adjustments, Subsection 1-6, Single-Sideband period (up to 6 hours for cold equipments ) to reach Adjustments. its normal operating temperature. Frequency sta­ bility is improved by keeping the equipment heater Step Indication Action power on at all times. This will also lengthen tube life and minimize equipment failure. a. SSB transmitter Inspect fuses and re­ (3) Single-Sideband Troubles hooting completely inopera­ place any that are Procedure tive; no panel lights blown. Inspect power Troubleshooting of SSB transmitters, as of or indications connections and ve rify other equipments, should be preceded by determining that power is applied the nature and extent of the malfunction. Trouble­ to the transmitter. If shooting methods are similar to those for conventional malfunction is not iden­ A3 equipment (signal tracing, voltage measurements, tified by this, follow etc.), but require more accurate adjustments and appropriate procedures therefore more accurately calibrated test equipment. of Subsection 1-7, The indications given in each step following Power Supplies. identify the circumstances under which it is to be b. SSB transmitter Verify that all control used. The first two are for inoperative transmitters, inopertaive; power settings are compatible the third is a quick, 2-signal test for directing further present but no with the preliminary troubleshooting, and the rest are for locating the output or calibrated settings. stage and component in which any type of malfunction originates. All step after step c require the use of an Inspect panel meters audio generator. These steps can be used without to determine if proper change in cases of no RF output, with a signal tracer voltages are present; (such as Test Set AN/USM-3) or a suitable coupled if not, follow the appro­ receiver in cases of distortion, and with a VTVM or priate steps of Subsec­ oscilloscope of suitable characteristics in cases of tion 1-7 , Power Supplies. low output amplitude. Intermittent conditions are troubleshot by gently tapping transmitter components while monitoring the modulated output. Use the

ORIGINAL 1-35 . . . . . ,- , ,- ,-

COM MUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action

being correctly ad­ NOTE justed. If bandpass The following steps require either an filter is a tunable IF audio tone or an inserted carrier; a amplifier, make sure correctly functioning SSB transmitter it is adjusted to track otherwise has no significant RF output proper output of sec­ unless such inputs are provided. Use ond mixer. carrier insertion or FSK mark or space e. signal present Determine if the R F test signal if transmitter is so equipped. IF at sideband filter signal is pr esent at Otherwise, insert an audio oscillator output but no F the output of the sec­ signal, 400- 1000 Hz at -10 dB (0 . 6V) R signal at band­ ond modulator. If so, into the microphone input . Use a re­ pass filter input. trace the signal through ceiver or frequency selective voltmeter the RF circuitry be­ tunable to each intermediate frequency tween the second modu­ and injection frequency to sample the lator and the band-pass signal at desired points in the tran s mitter . filter to locate the com­ ponent responsible for c. Transmitter has no Set up the audio gener­ the signal loss. Tube RF output . ator in place of the testing, voltage and microphone input, resistance measure­ energize the equipment, and tests and use the receiver, ments, of component condition a wave meter, or a fre­ can be used to locate quency meter to test defective components. for the presence of the correct signal at the R signal not pre­ Test for the presence following points: F sent at second of the second injection RF signal not at Start at Step d. balanced modula­ frequency and the IF output of band­ tor output . inputs to the modulator, pass filter using receiver, wave­ meter, or oscilloscope . R F signal not at Start at Step e. input of bandpass No second balanced Troubles hoot the second filter modulator output, balanced modulator but both inputs stage by testing the tubes IF signal not at Start at Step f. present. and measuring socket output of sideband voltage and resistance. filter Replace any defective IF signal not at in­ Start at Step g. components found and put of sideband perform Adjustment G filter for second modulator balance . If the R F signal is ob­ tained at each of these Second injection Troubleshoot the second points but not at the signal injection frequency os­ transmitter output, cillator circuitry, using follow the appropriate the techniques of Sub­ steps given in Subsec­ section l-6, RF Oscil­ tion l-6, Transmitters . lator Or Frequency Make alignment adjust­ Source Malfunctions. ment if required . Othe r­ Perform Adjustment wise, start with the step H. given for the lowest test IF input to second Trace for this signal point at which the sig­ balanced modulator in the circuitry between nal cannot be found-at is absent. the sideband filter and Step e, for exam pie, if the second balanced the R F signal is not modulator. When the present at the bandpass signal is found, deter­ filter input, but the IF mine the cause for its signal is present at the loss by testing tubes, sideband filter output. making tube socket d. RF signal present Adjust band-pass filter voltage and resistance at input but not out­ (Adjustment I), follow­ measurements, and put of band-pass ing directions given in testing component/con­ filter. technical manual. Re­ dition. Replace any com­ place filter if it is ap­ ponents found to be parently incapable of

ORIGINAL 1-36 ..

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action

defective. Perform necessary, to deter­ Adjustment F, if mine where audio sig­ needed, and verify nal is lost. If no modu­ that the RF signal is lation circuitry output present at the second is found, use the Modu­ balanced modulator lator Trouble-Shooting output and at the trans­ procedure, Subsection mitter output . l- 6, to correct the mal­ function. Make Adjust­ f. IF signal present Verify that input fre­ ment A if necessary . at sideband filter quencies are correct input but not at (perform Adjustment No first inJection Follow appropriate output. B if necessary) and frequency input to steps of Subsection make Adjustment E of first balanced modu­ l-6, RF Oscillator or sideband filter, follo�­ lator found previously. Frequency Source . ing directions given in Malfunctions, if signal­ transmitter technical trac ing shows that the manual. Replace side­ oscillator is not opera­ band filter if it is ap­ ting correctly. Make parently incapable of Adjustment B of oscil­ being adjusted lator frequency and correctly. Adjustment C of in­ jection signal ampli­ g. IF input to side­ Determine if the IF tude if required. band filter is signal is present at absent. the first balanced h. Carrier present Make Adjustment D modulator output; if in R F output. (modulator balance). so, trace the signal If the carrier is still from that point toward present, check and, if the sideband filter in­ necessary, readjust put. When the point of using Adjustment B � signal loss is located, (first inje tion frequen­ use tube testing, volt­ cy) and E (sideband age and resistance rejection filter band­ measurements, and pass). component condition­ testing techniques to e. MODULATORS identify the cause of the The simplest transmission conveying informa­ malfunction. Replace tion is a CW transmission - an Al emission. The any defective compon­ same equipment can be used for phone transmission ents found and verify if circuitry for amplitude-modulation of the Al emis­ that the filter input is sion is added. This signal resulting is an A3 emis sion. now present. (l) Methods of Amplitude Modulation High level modulation, commonly used in No IF signal at Measure the amplitude conventional amplitude modulation, applies the modu­ balanced modu­ of AF and first injec­ lating wave to the transmitter power amplifier (PA ). lator output. tion frequency inputs to Because 100% modulation requires that the modulating first balanced modula­ wave power be 50o/o the power of the carrier, a large tor. If both are pre sent modulator is required to plate-modul ate a high- level at the correct level, stage. For control grid, suppressor grid, or screen troubleshoot the balan­ grid modulation, a smaller modulator can be used, ced modulator by means but PA efficiency suffers. In order to achieve lOOo/o of tube testing, tube modulation, a tetrode or pentode PA stage requ ires socket measurements, that modulation be applied to both the screen grid and and tests of component the plate; a tr ansistor PA stage requires that modu­ condition. Replace de­ lation be applied to both the PA stage and the driver rective components, (IPA) stage . Figure 1-15 shows the typical stages of make modulator bal­ a high-level modulator. ance, Adjustment D, Low level modulation is accomplished in a low and verify that the power stage other than the PA, usually in or near the correct output is now frequency generation circuits. Obviously, less modu­ present. lator power is required. Low level modulation is typi­ No AF input to Check all audio cables, cally used for FM and SSB. Note that post-modulation frequency multiplication will multiply the frequencies first balanced connectors, terminals of the modulation products as well as the carrier fre­ modulator found and switches for con­ quency. This is acceptable (and commonly used) in previously. tinuity; use signal­ FM, provided that, after frequency multiplication, tracing techniques, if

ORIGINAL 1-37 ...... - ... - ... - ... -

COMMUNICATIONS NAVSEA 0967-LP-000- 0010 GENERAL

� OUTPUT

RF INPUT RF POWER AF FROM AMPLIFIER TRANSMITTER SWITCHBOARD

AUTOMATIC LEVEL CONTROL

CLIPPER­ AF SPEECH FILTER PREAMPLIFIER OUTPUT AMPLIFIER OR AMPLIFIER COMPR ESSOR

CLIPPING BIAS LEVEL (LINEARITY) (MAX MOD %) 0 0

Figure 1-15. Typical Modulator Block Diagram

the necessary bandwidth limits are not exceeded. In necessary to replace the attenuator with a resonant AM transmitters, post- modulation frequency multipli­ circuit in order to develop sufficient deflection voltage. cation cannot be used; only unmodulated frequencies For trapezoidal patterns, the scope horizontal are multiplied. Therefore SSB, ISB, and other forms deflection amplifiers are driven by the audio signal of amplitude modulation performed in low level stages as shown. For envelope patterns a sawtooth (inter­ are translated to the desired output frequency by het­ nal) scope sweep is used, synchronized with the modu­ erodyning rather than by frequency multiplication. lating audio. For two-sideband tests, either use two In addition, all post-modulation amplifiers for AM audio generators on different frequencies in an SSB must be linear (i. e. , Class B, AB, or A amplifiers) setup, or use one audio generator into separate ISB in­ in order to aviod amplitude distortion. puts . (2) Monitoring Amplitude Modulation This or any suitable method of checking modu­ For test and adjustment of AM transmitters, lation should be used if reports of signal distortion with or without carrier, the arrangement of Figure or "splattering" (emission beyond the normal band­ 1-16 can be used. An audio input of 300- 3000 Hz, width limits ) are received. variable from 100 mV to l volt, is inserted into the Figure 1-17 (A and B) shows trapezoidal and transmitter microphone jack. When the audio genera­ envelope patterns which are useful for checking per­ tor is set for 1 volt, at least 20 dB attenuation is formance and making adjustments of amplitude­ needed. The A-F input attenuator should preferably modulated transmitters. be a calibrated type (a spare AN/SGC-lA REC LEVEL Modulation Pattern a - No carrier and no modu­ control will serve ). The R- F output voltage developed lation. If the transmitter is supposed to be emitting across a 50-ohm dummy load is applied directly to a carrier, an RF output malfunction is indicated. The the scope vertical deflection plates. Vertical deflec­ pattern is normal for SSB when no modulating signal tion size is controlled by a capacitive attenuator. For is present. low power transmitters (less than 20 watts) it may be

ORIGINAL l-38 ...... ,- ,- ,- ,-

COM MUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

·'i

TRANSMITTER

AF MIKE INPUT RF OUTPUT AT TENUATOR - ? -CONNECTOR AUDIO

OSCILLATOR

DUMMY LOAD OR

TERMINATING @ WATTMETER OSCILLOSCOPE 22 pF VERTICAL PLATES - o-f7. 5 F DIRECT 0 � p HORIZONTAL INPUT T 2.2 pF 0

Figure l-16. Oscilloscope Connections for Monitoring Modulation

Modulation Pattern b - Carrier with no modu­ Modulation Pattern g - Excessive modulation lation. If the transmitter is supposed to be modulated, in the downward direction with carrier present. This an AF malfunction is indicated. indicates that excessive modulating audio is being ap­ Modulation Pattern c - 50"7o modulation with full plied, or that insufficient carrier is inserted. The carrier. The same envelope (but not trapezoid) will trapezoid pattern will be the same for excessive single be produced for SSB with 50% (-3 dB) carrier inser­ sideband and two sideband modulation. tion, or for two sidebands when one sideband is twice Modulation Pattern h - Modulation in excess of the amplitude of the other. upward modulation capabilities with carrier present. Modulation Pattern d - IOO"!o modulation with full Note flat-topping of the pe aks. Upward modulation carrier. The trapezoid pattern will be the same for peaks can be much greater than twice the carrier am­ single sideband or two sidebands at lOO"!o modulation, plitude without constituting overmodulation unless with or without carrier. flat-topping occurs. The trapezoid pattern also in­ Modulation Pattern e - lOO"!o single sideband dicates excessive single sideband or two sideband up­ single tone modulation with no carrier. Note that the ward modulation, which may be caused by overdrive envelope pattern is the same as that of an unmodulated of any stage to which the AF or RF signal is applied. carrier. A two sideband (or miltiple sideband) envelope pattern Modulation Pattern f - Two equal sidebands with would show similar flat-topping as a consequence of

·. no carrier. Note that the cross-over at the null points overdriving or under loading a linear RF amplifier . form a definite "X ". The presence of carrier would Modulation Pattern i - AF phase shift in the be indicated by pe aks differing in height, alternately. speech amplifier section. Phase shift is not readily The amount of carrier would be indicated by the apparent in an envelope pattern (except by comparison amount of difference in height until, at full carrier, on a dual-trace scope), so none is shown. Modulation the pattern shown at d is produced. approximately 50%.

ORIGINAL 1-39 ......

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

TRAPEZOID ENVELOPE

A. NO CARRIER, NO MODULATION.

B. CARRIER, NO MODULATION.

C. FULL CARRIER , 50 % MODULATION.

D. FULL CARRIER , 100% MODULATION.

E. 100 % MODULATION, SINGLE SIDEBAND, NO CARRIER.

F. 100 % MODULATION, TWO SIDEBANDS , NO CARRIER.

Figure 1-17A. Modulation Patterns Obtained on an Oscilloscope

ORIGINAL 1-40 ......

COMMUNICATIONS 0967-LP-000-0010 GENERAL NAVSEA

TRAPEZOID ENVELOPE

G. DOWNWARD OVER MODULATION , WITH CARRIER .

H. UPWARD OVER MODULATION , FULL CARRIER.

I. PHASE SHIFT IN AUDIO SECTION.

J. NON-LINEARITY, TWO SIDEBANDS, NO CARRIER.

K. CARRIER LEAKAGE, SINGLE SIDEBAND.

L. PA RASITIC OSCILLATION.

Figure 1-17B. Modulation Patterns Obtained on an Oscilloscope

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Modulation Pattern j - Non-linearity for two Automatic level control (ALC), Adjustment D, sidebands and no carrier. Note that the envelope sometimes called automatic gain control (AGC) or does not show a sharp "X" at the crossover points automatic volume control (AVC), operates to keep (compare with f). The trapezoid pattern would be the average modulation nearly constant even with audio same for any form of AM, with or without carrier. inputs which vary widely in amplitude or numbers of For low level modulation, the non-linearity could be tones. It allows the speech amplifier to operate near in any stage which amplifies the AF signal or modu­ full gain for weak signals, but reduces the gain when lated RF signal. Improper bias or improper loading stronger signals are present. It therefore tends to of some stage is indicated. The pattern is normal prevent overmodulation, except that it functions as an for screen grid or suppressor grid modulation. averaging device rather than a peak limiter like the Modulation Pattern k - Single sideband with clipper-filter. Its action provides the proper input the carrier not completely eliminated. Indicates that level to the clipper stage for efficient clipping. If a the SSB modulator is not balanced, or that R F is low-level stage is modulated, the ALC circuit takes leaking around the balanced modulator. Insufficient its input from the RF power am plifier rather than the rejection of the unwanted sideband is similar except A F power amplifier. that the ripple frequency would be twice as great. When modulator adJUStments are properly made, Hum modulation of SSB (or of carrier and no sidebanp ) all audio inputs from a mumble to a shout will produce is also similar except that the ripple would be at the ample modulation without overmodulation. (EIB 612) hum frequency. (4) Modulator Troubleshooting Modulation Pattern l-Parasitic oscillation on Any type of modulator is essentially an modulation peaks. The peaks appear to be "snow­ audio amplifier which is coupled to a transmitter; capped" with a fine-grain pattern. Indicates inade­ modulator troubleshooting methods therefore resemble quate neutralization or shielding. those for conventional audio amplifiers. Use the ap­ (3) Modulator Adjustments propriate steps to identify and correct any modulator Modulator circuits should be set according malfunctions . to the standard audio distribution levels of the ship or station concerned (see Audio Level Control at RPU's f. LINEAR RF AMPLIFIERS in Subsection 1-9). Thereafter it is seldom necessary The introduction of single sideband to the fleet to make further operational adjustments unless the has brought about a new generation of transmitter equip­ audio levels are changed, or the power input or load­ ments. Examples include AN/WRT-2, AN/WRC-1, ing of the modulated stage is changed. The four prin­ AN/URC- 23, AN/URC- 32 and AN/URC- 35. Because cipal adjustments are shown in Figure l-15. Not all modulation of these transmitters is performed in low­ transmitters have all four. level stages, power amplification must use linear am­ The test arrangement of Figure l-16 will be of plifiers instead of class "C" amplifiers common to great benefit in making the proper adjustments. Be­ older equipments. It is the linear amplifier that places cause the controls are interrelated, the technical a special requirement on the "care and feeding" of manual for the particular transmitter should be used SSB transmitters. for guidance. In general, the adjustments function Linear power amplifiers are limited by their as follows : peak power handling capability. Unfortunately, the Speech gain, Adjustment A is set for sufficient panel meters read AV ERAGE power rather than PEAK gain to permit the weakest voice or tone signal, ar­ power. The average undistorted power of a linear am­ riving over the longest line, to amply modulate the plifier is affected by the type of signal that it is ampli­ transmitter. fying and by the loading of the amplifier. In technical To prevent strong audio peaks from overmodu­ terms, it is limited by the peak-to-average power ratio lating the transmitter, clipping level, Adjustment B, of the modulation envelope, and by load mismatch, (sometimes called maximum modulation percent) is which, for the PA, is represented in part by the volt­ set to clip any peak audio that might exceed the high­ age standing wave ratio (VSWR ) of the antenna feedline. est allowable level. When speech gain is set so that SSB transmitters therefore employ antenna tuners with moderate clipping of speech is present, the ratio of a VSWR indicator to make sure the antenna fe edline average-to- peak modulation is increased. Because presents a nonreactive load to the PA . This simplifies the clipping action introduces distortion, an audio matching the PA plate tank to the antenna. Old Navy filter is also provided. Usually the clipper- filter can transmitters used class "C" amplifiers which were be switched in or out at will . Some modulators use a limited in power output by how well an operator could logarithm ic speech compressor rather than a clipper­ "tweak" them up before the PA plate blushed red. If filter because fewer distortion products are generated. you try "tweaking" an SSB transmitter to get maximum The speech gain control and the clipper-filter operate indicated power output, you get some disconcerting and together to provide a high average power in the side­ sneaky results . bands, without generating extra bandwidth through The following should be considered to be the overmodulation or distortion. Clipping is beneficial MAXIMUM power capabilities of the AN/\'.'RT-2 trans­ on voice, undesirable on tone modulation. mitter: Many transmitters have a bias or linearity ad­ Peak Envelope Power 1000 Watts justment, Adjustment C. For high level modulation, CW (AI) 500 Watts it is in the "modulator" or AF power amplifier. When FSK (Fl) 400 Watts modulation takes place in a low-level stage, the bias SSB Voice (A3J) 500 Watts adjustment is in the R F power amplifier. It is adjusted AM Phone (A 3) 300 Watts to place the amplifier in the most linear portion of its 8-Channel Multiplex (A7 J) 175 Watts transfer curve. Compare oscilloscope modulation 16- Channel Multiplex (A 7 J) 130 Watts patterns f and j of Figure l-17.

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The maximum power outputs for AN/URC-32 were used in the AM (A3 ) mode than it was when they transmitters is somewhere around one-half of those were used in the SSB (A3J) mode. 30% of the stations listed for the AN/WRT-2. The tuning procedures in on one A3 net were overmodulated to the point where the technical manual should be followed and the above voice quality was seriously degraded. Nearly all the specified limits used as a check. However, because transmitters on this net were identified as SSB type of the antenna loading effects and aging of transmitter by the absence of one sideband on the spectrum ana­ PA tubes, power output using correct tuning procedures lyzer display. may be substantially less than that given. An attempt What effect does overmodulation have on the per­ to drive the linear amplifiers to a higher power out­ formance of voice circuits ? You can bet that, when put is likely to result in overmodulation. The effect you hear a transmitted voice that sounds as if the op­ would appear as shown in modulation pattern h of erator were speaking with a mouthful of mush, it is Figure l-17. because of overmodulation and not because the opera­ Peak envelope power (PEP) indicates a maximum tor has a mouthful of mush. Over modulation can be capability of the transmitter that should not be exceed­ due to many causes; the main one for SSB transmitters ed during any portion of the modulation envelope if is an attempt to increase the indicated RF output, distortion is to be avoided. In order to keep the trans­ thereby driving a linear amplifier beyond its limits mitter within its PEAK ratings, it is essential that the of linearity. Most transmitters can compensate for AVERAGE power as indicated on the RF output meter differences in audio inputs to the transmitter caused be adjusted for the type of emission that is being by differences in radio handsets or speech levels used transmitted. by operators (see Modulator Adjustments ). It is up to For example, on SSB with two equal tones in the the transmitter operator, however, to see that the upper sideband and with suppressed carrier, the DR r­ tuning, loading, speech gain, and drive (or excitation) VER or EXCITER should be adjusted for an R F output adjustments are set to keep the linear amplifiers op­ meter reading of 500 watts average power to obtain erating in a linear manner. the rated PEP. With four equal tones under the same The most reliable way to make the initial adjust­ conditions, the RF output meter should indicate 250 ments for amplifier linearity is to use an oscilloscope watts average power for a PEP of 1000 watts. In ISB in a test setup such as that shown in Figure l-16. A operation, with two tones in the upper sideband and spectrum analyzer is also useful for checking distor­ two tones in the lower sideband (four tones in all), the tion products. Once the operator is familiar with the RF output meter should also read 250 watts for rated meter readings at the point where distortion begins, PEP. Thus, the combined modulation in both side­ the meters can be used for monitoring - with only an bands determines the ratio of PEP to average power. occasional verification by the oscilloscope method. If Whenever carrier is inserted, it usurps a por­ desired, it is a simple matter to arrange the spectrum tion of available power and thereby reduces the power analyzer or test setup as a permanent "on the line" that can be devoted to the sidebands. monitor . (EIB 623, 734) Let's observe what happens when we overdrive (1) Peak Envelope Power (overmodulate) a transmitter modulated with a multi­ When an SSB transmitter is modulated with plex teletype signal. When an SSB transmitter is tone multiplex equipment such as the AN/ UCC-1, care modulated to the peak of its power capability, the sig­ must be exercised to ensure that the transmitter peak nal is at least 35 dB above the noise level that the envelope power (PEP) rating is not exceeded. Exceed­ transmitter is also generating. Any further increase ing PEP ratings in multitone operation will cause inter­ in indicated power output will result in overmodulation modulation distortion of the tones and result in deterio­ distortion of the signal and a rapid increase of noise ration of the radiated signal . power. In other words, the indicated increase of PEP is defined as the rms power developed at average po wer is signal degradation rather than im­ the crest of the modulation envelope when the trans­ provement. mitter is modulated with multiple audio frequencies. With severe overmodulation, the indicated in­ If an SSB transmitter is modulated with two audio crease of average output means that the transmitter tones of equal amplitude, and an oscilloscope is con­ is no longer putting out a narrow signal of 3 kHz with nected as shown in Figure 1-16, a two-tone test pat­ some small additional noise within 10 kHz of the as­ tern may be observed. The PEP of a transmitter may signed frequency. Instead, the transmitter is emitting be computed by measuring the rms voltage (0. 707 of significant noise hundreds of kilohertz either side of pe ak), squaring this value, and dividing it by the load the assigned frequency. The transmitter is also emit­ resistance (normally 50 ohms). With two- tone modu­ ting very large signals at its harmonics and at the fre­ lation, such as that shown at modulation pattern f of quency of its "unwanted" sideband . If several trans­ Figure 1-17, the average power output will be equal to mitters are keyed simultaneously, intermodulation one- half of the PEP. products show up as large signals throughout the spec­ With multitone operation, the average power trum . Interference levels become so great that only output will be much less than the PEP. A transmitter strong signals can be copied. Further details appear must divide its power capabilities among the tones in EMI Reduction EIMB (NAVSHIPS 0967-000-01 50) modulating it. To calculate the average power of the Section 7. transmitter or the average power per tone for n num­ The same considerations apply to voice circuits ber of tones input, the following formulas may be as to multiplex teletype circuits because the transmit­ used: ter sees the same peak-to-average power ratios. Dur­ PEP PEP ing a fleet operation previously mentioned, it was the Avg Pwr Pwr per Tone • --- n 2 rule and not the exception that voice transmissions n were distorted to various degrees by overmodulation. This was more so the case when SSB transmitters

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Refer to Figure l-18. Assume that a transmit­ been found that this theor etical average limit can be ter is modulated with two tones of equal amplitude, exceeded by approximately twice this value without f1 and f2 , and its output is terminated into a resistive introducing appreciable distortion. load of 50 ohms. The voltage in each output frequency Overdriving a linear amplifier generates inter­ is measured and found to be ll2 volts rms. Squaring modulation distortion products which result from har­ the voltage in each output frequency and dividing that monics of the desired frequencies mixing with funda­ by 50 reveals the power in each output frequency to mentals and other harmonics. The power usurped by be 250 watts. The sum of these two is 500 watts, these undesirable products is taken from that avail­ which is the average power output of the transmitter. able to desired intelligence frequencies and decreases When the two output frequencies fall in phase with the effective radiated intelligence . each other as shown in vector diagram b, the crest Tone channels applied to the transmitter should of the modulation envelope is reached and the voltages contain intelligence; idle tone channels must be turned add up to 224 vo lts. Square 224 and divide by 50 to off. This practice will ensure that the transmitter obtain the PEP of l kW. From this illustration, we power will be distributed to each intelligence-bearing see that the average power for two-tone modulation frequency. Transmitter power output should never is one-half the PEP. exceed the level required to maintain communications. A transmitter modulated with 16 tones would Excessive power levels will damage components of have a theoretical average power output of only 64 the transmitter and antenna tuner. (EIB 727) watts with a PEP of 1 kW. In practice however, it has

LLJ 0 :J 1- IN- PHASE ....1 INSTANT a.. � �

2 3 4 5 6 7 FREQUENCY

A. POWER SPECTRUM B. POWER VECTOR

Figure 1-18. Calculating Average Power and Peak Envelope Power for Two-Tone Modulation

1-7 POWER SUPPLIES heater power for vacuum tubes and in some cases relay-operating power. Power supplies which are part of Transmitting 2. Regulated power supplies, consisting of Equipment, Subsection 1-6, or Receivers, 1-8, can be an unregulated supply and associated circuitry to placed in a category with one of the types described regulate the B-plus output. in this section. Since troubleshooting procedures 3. Motor-generator sets to supply the above are the same for part of the self- contained equipment voltages. Tr ouble shooting malfunctioning power as for the unit-type power supplies, regardless of supplies should be preceded by a preliminary check­ voltage and current requirements, the description is out procedure covering the simple, easily overlooked not repeated in Subsections 1-6 and 1-8. causes of trouble. This preliminary troubleshooting Power supplies commonly used in electronic procedure is followed by the procedures for the basic equipment are of the following types: unregulated power supply and the regulating circuitry. 1. Unregulate·d supplies, usually providing Motor-generator sets, on the other hand, require filtered but unregulated low B-plus (under 300VDC) continual routine maintenance of a mechanical rather or high B-plus (over 300VDC), in addition to AC than electrical nature, but little troubleshooting. Both maintenance and troubleshooting procedures for motor

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generators are given in Paragraph 6-2 of General b. POWER SUPPLY TROUBLESHOOTING Maintainance, NAVSIDPS 0967-000-0160. PROCEDURE Perform the appropriate steps listed in Table a. PRELIMINARY POWER SUPPLY TROUBLE­ 1- 7 to troubleshooting unregulated supplies or the un­ SHOOTING PROCEDURE regulated portion of regulated supplies. The quick checkout procedure given in Table 1-6 can be performed without removing the equipment from its cabinet or console. Some steps result in correction of the malfunction, while others deter­ mine on what following step to proceed.

TABLE 1-6. POWER SUPPLY QUICK CHECKOUT TROUBLESHOOTING PROCEDURE

Step Condition Check If Action

a. No power and no panel Line cord Not plugged in Plug in lights

Fuse Defective Replace

Good Start with Step b.

Blown Check dial settings and replace fuse

Blows again Start with step a in Table l-7.

b. Input power present, Switch and dial Incorrect Set correctly but some voltage in­ settings dications at supplied equipment not normal

Cables Unplugged Plug in

Plugged in Start with Step bin Table l-7.

c. REGULATED POWER SUPPLY TROUBLE­ set up the conditions specified for making these ad­ SHOOTING PROCEDURE justments. l. If any symptoms of the regulated power sup­ 6. Make tube socket voltage and resistance ply resemble those for the unregulated type of supply, measurements in the regulator circuitry, following troubleshoot them by using the appropriate steps given the directions given in the technical manual for set­ for the unregulated supplies. If necessary, disconnect ting up the required load conditions . Replace any the regulating circuitry for troubleshooting and repair defective components that could cause incorrect in these steps. values. 2. Verify that the unregulated output are of the 7. If acceptable regulation with load connected correct voltage. The a-c voltages (5. OVAC and cannot be obtained due to excessive current drain, de­ 6. 3VAC) are usually unregulated and can be measured termine where in the load circuitry the excessive at the unit's output. The unregulated d. c. can be drain is occurring. This can be done by removing measured at the input to the series-pass tubes or at tubes in the supplied equipment one by one, noting the regulator output, with the shunt-regulator tubes how much the current requirement is reduced for removed. each tube withdrawn. When the withdraw! of a parti­ 3. Determine the effectiveness of regulation cular tube reduces the current by an amount greater circuitry by adqing a resistive load that is ten times than the tube requirements (plate and screw), both the resistance of the real load. Use resistors of the tube and its associated circuitry should be inves­ pc,wer capabilities no less than that calculated from tigated. Typical reasons for excessive current are the resistance and the voltage . Connect this load in defective screen bypass capacitors, leaky decoupling parallel with the normal B-plus load and insert a capacitors, and defective (shorted or gassy) tubes. switch in the normal load. Meter the output voltage Correct the conditions causing the excessive load. while switching the normal load on and off. The regu­ lating circuitry is defective if the voltage drop un­ der full load exceeds the power supply specifications. If this is the case, perform step d. 4. If the regulation is defective, use Tube Tester TV-3A/U or equivalent to determine the con­ dition of all tubes in the regulating circuitry. Be sure to determine the condition of any voltage regu­ lating tubes included. Return each acceptable tube to its original socket and replace defective tubes. 5. Make any adjustments given in the techni­ cal manual for regulation of the output voltage. Fol­ low the directions given in the technical manual to

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TABLE 1-7. UNREGULATED POWER SUPPLY TROUBLESHOOTING PROCEDURES

Stop Condition Check If Action

a. Fuse blows repeatedly Remove load, re­ Operation is Troubleshoot supplied equipment place fuse, and normal (load) for: energize again l. Tube shorts 2. Wiring shorts 3. Overheated components Fuse blows again Check power supply: l. Tubes 2. Electrolytic capacitors for leakage 3. Other capacitors for leakage 4. Compare power transformer winding resistances with normal values and replace transformer if defective

b. Not all output voltages Use voltmeter to Open circuit is Make necessary repair or replace­ present at supplied determine where found ment equipment voltages are lost between transform- er and supplied equipment

One (or more ) Use ohmmeter to verify that trans­ transformer former winding is shorted or open; outputs are replace transformer missing

c. Some or all output Transformer pri- Incorrect con- Change to correct connections voltages are not mary tap connec- nection for in- correct tions for various put voltage line voltages being used

Transformer Any winding is Replace transformer winding volt- open or has ages and re- shorted turns sistances (indicated by changed resis- tance )

d. Incorrect DC output Tube condition Tube (s i defec- Replace Tube (s) (following perfor- ti ve or has low mance of Steps b emission and c. )

Electrolytic Defective Replace capacitors capacitors

e. Output voltage level Intermittent Tapping com- Inspect component or connection varies conditions by ponent or ter- tapped and replace or repair if metering output minal affects defective voltage

1-8 RECEIVERS a. RECEIVER COMPONENTS The simplest possible receiver consists of a This section gives generalized alignment instruc­ resonant circuit to select the desired frequency, a tions and troubleshooting procedures for superhetero­ detector which rectifies the RF signal to produce the dyne receivers. Single-side-band techniques and re­ AF signal across its load resistor, and on electricity­ ceivers are included. since SSB is now widely used in to- sound transducer, all shown in Figure l-19. A naval communications, but TRF, regenerative, and "crystal set" is such a receiver and the now outmoded superegenerative receivers are not included. TRF (tunedradio-frequency ) receiver a vacuum-tube A description of the configuration of stages elaboration of it . These receivers can receive A2 needed and tabulation of alignment points for super­ and A3 signals but cannot receive CW signals without heterodyne receivers is followed by preliminary and modification. systematic troubleshooting procedures. These are The superheterodyne receiver is used in all divided into "front end" (R F and I F) AGC and detector, types of radio communication because of its selectiv­ AF and SSB receiver troubleshooting. ity and adaptability to all types of reception. The

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\7 ELECT RICITY- RESONANT DETECTOR TO- SOUND CIRCUIT TRANSDUCE R ll ....I n

Figure l-19. Simple Receiver, Block Diagram

simplest superheterodyne is shown in block- diagram used for FM detection. Principles of detector opera­ form in Figure 1-20, but more typical ones include tion will be found in the various electronics technicians more stages (dotted lines in the figure) for greater rating manuals and in the ARRL Radio Amateur's sensitivity and selectivity. Handbook . The heterodyning action of the superheterodyne Automatic gain control (AGC) circuitry or, as receiver results from "mixing" the incoming RF sig­ it is sometimes called, automatic volume cont rol nal with another higher or lower RF signal, generated (AVC) is included in receivers to make operation by the receiver's local oscillator, Figure 1- 21. The easier by reducing amplification of strong RF peaks. local oscillator and RF tuning capacitors are ganged It operates by supplying a biasing voltage to at least together and adjusted to produce the same intermediate two early RF or IF stages, the bias increasing when frequency for any RF input frequency selected. strong signals are received. The bias ing voltage is Some superheterodyne receivers are called obtained from the AGC rectifier. which is often located "dual-conversion" receivers because they generate in the same tube envelope as the detector diode. AGC a second internal frequency to mix with the first IF action is disabled when a receiver panel switch is in signal . This forms a second intermediate frequt:ncy the AGC OFF OR MANUAL GAIN CONTROL, rather which is detected in the conventional manner. than in the AGC ON position. Fixed intermediate frequencies are used because Single-sideband circuitry has some necessary they have the following advantages : and some desirable differences from conventional l. Increased selectivity. superheterodyne circuitry; the AGC rectifier samples 2. Increased and more linear sensitivity. the signal before BFO injection or detection and uses 3. Easy filtering and feedback techniques for long time constants to maintain AGC action while no signal selection or rejection over the range of the signal is present between periods of modulation (be­ IF bandwidth. tween words, for instance ). Conventional superhetero­ 4. Bandwidth adjustment by front-panel controls dyne communications receivers can be used for SSB is possible without adding greatly to circuit complexity. reception if they have narrow-band filters, slow tuning 5. CW, FSK, and SSB reception is simpler be­ rates, and stable oscillators. An SSE signal is re­ cause BFO injection is at a fixed frequency. ceived on such equiprnents by tuning on the sideband The B FO provides a frequency which, on mixing for maximum input indication and then setting the BFO with an signal, heterodynes it into the audio range . by ear for intelligible reception. Because the final audio frequency is critical for SSB, Single-sideband reception is possible also with FSK and M UX reception, and because it is affected by conventional receivers using single-sideband convert­ each frequency conversion step, extreme stability is ers, as well as with specialized SSB receivers. SSE required of each heterodyning oscillator (local oscil­ converters accept the receiver IF signal, select the lator and BFO). desired sideband by further conversion and filtering, Several types of detectors are used in super­ detect by mixing the sideband with an injected carrier, heterodyne receivers; the most common is a diode and supply the demodulated signal at usual audio power detector with an RF decoupling network fo llowing, levels. Tuning is done first at the receiver and then which is suitable for reception of all AM signals. at the converter, across the receiver bandpass. The product detector or balanced modulator (a form Specialized single-sideband receivers now of mixer) is often used in detection of SSB signals, corning into use have local oscillators of sufficient although the diode detector will work in this applica­ accuracy and stability to permit reception by just tion. Ratio detectors and phase discriminators are setting the receiver to the desired frequency; tuning

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COMMUNICATIONS NAVSEA 0967-LP- 000-001 0 GENERAL

AF OUTPUT

- - , t · - r--- , I I I I I --f RF I I 2ND. AF 1 BFO AMPLIFIER I I I I AMPLI FIER I I I I I'- L.-.--' - ,__.J / I " I ·- --., CONVERTER I (MIXER IF I SEPARATE I ST. IF 2 ND. IF . I ST AF l DETECTOR LOCAL AMPLIFIER AMPLIFIER I AMPLIFIER OSCILLATOR I i USED) I L- -JI I f t I �----J I I I ' I -- r-...L -, TO I r -, I RF AMP t I I \ I I I I LOCAL : \._ L-.-,I AVC !.J POWER I OSCILLATOR I SUPPLY I ' DETECTOR I - I I I : I I I L. - - I L __ _ .J - ..J QUE L ______� ., ON � OFF.....L.I

Figure l-20. Simple Superheterodyne Receiver Block Diagram. (Stages Added for Typical Communications Receiver Shown in Dotted Lines).

by visual or aural indications is not required. The be carried out under these circumstances but should stability required is obtained in some complex equip­ never be attempted unless it is certain that alignment ment by deriving component frequencies from crystals is required. The need for some alignment adjustments and circuitry enclosed in ovens which are accurately is indicated by loss of selectivity and sensitivity, par­ maintained at specified temperatures. In other equip­ ticularly if the various bands are affected to different ments of comparable accuracy and stability, the local extents. Also, alignment may be required following oscillator frequencies are obtained from continously - replacement of the local oscillator tube and if the variable oscillators controlled by crystal-referenced dial indications do not conform to the actual frequency circuitry, and operating to correct for any frequency being tuned. error or drift. Do not attempt alignment to correct a malfunc­ tion which has appeared suddenly, although in the b. RECEIVER ALIGNMENT ADJUSTMENT S course of troubleshooting one adjustment at a time Superheterodyne receivers can drift out of align­ may be altered slightly and then returned to its origi­ ment after long use and consequent component aging. nal setting. Some or all of the alignment steps following should

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�r-- \1/ IF TRANSFORMER MIXER fg, fj. i ) f.I (fg +fj) (fg -f TO FOLLOWING / . AND IF STAGES (fg-fj) PASSES I D GONLY / (fg-fj ) PANEL � / TUNING / DIAL / fg

VARIABLE ELEMENTS (USUALLY C1 AND C2l ARE LOCAL LINKED IIECHANICAV_ Y Ill SUCH A II A II ERII THAT OSCILLATOR IS THE SAllE FOR ANY SEL ECTEO. I (fg-fj) fi I / THE IF TRANSFCRIIERS FOLLOWING PAS S ONLY FREQUENCIES VERY NEAR {fg -fi ) . I I / C32 I / I / / 1 / v

Figure 1- 21. Heterodyne Action in Superheterodyne Heceiver

It often happens that the stability and frequency 2. Use a crystal-controlled alignm ent accuracy built into a receiver by using crystal­ generator. controlled oscillators is degraded through faulty 3. Use a frequency counter (instead of the receiver alignment. This fault occurs because the signal generator dial ) to put the signal generator AN/URM-25, AN/URM-26, LP, and similar signal on frequency and keep it there. generators do not have the requisite accuracy and Figure 1-22 illustrates an arrangement for stability. For example, the AN I URR- 35 receiver using a frequency counter in conjunction with a sig­ requires IF alignment using a signal generator set nal generator. The frequency counter requires a to 18, 602 kHz. It is all but impossible to read the fairly large input signal, so the signal generator is signal generator dial that accurately - and even if it set for maximum output (or 0. 1 volt DIR ECT jack were easy to do, there is no assurance that the sig­ used) and the external variable attenuator set to con­ nal generator frequency is actually what the dial trol the signal level delivered to the receiver. reads. Typical indication of off- frequency IF align­ In order to provide adequate IF bandwidth, ment is a receiver that exhibits good sensitivity to a some receivers use overcoupled IF transformers signal generator or in continuous manual tuning, but which produce a double-humped response curve. performs badly or not at all in crystal-controlled Tuning such an IF transformer for peak response operation. may produce misalignment unless certain measures When the usual shipboard signal generators are taken. These measures usually consist of "swamp­ lack sufficient accuracy and stability for accurate ing" the resonant circuit with a temporarily­ receiver alignment, three alternatives are available: installed load . If the receiver TM calls for align­ 1. Use a frequency meter as a signal generator, ment using a circuit-loading signal generator probe or use the frequency meter to keep the signal genera­ or a temporary shunt resistor, make sure it is used tor on frequency. during alignment. (EIB 698, 735, 736)

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COMMUNI CATIONS NAVSEA 0967-LP-000-001 0 r. ENERA I,

T-CONNECTOR VA RIABLE

-- AT TENUATOR 1-­ "'--...... :' ··.----JJ (HP-355 0)

r

0 �·'�")� T 0 RECE IVER RF OUTPUT t X200K .. o@ �-CKT t ' t - RF OUT X MULT <9©©CQ)*£ @ @

FREQUENCY

COUNTER

Figure 1-22. Signal Generator with 10 Hertz Accuracy

c. RECEIVER MALFUNCTION INDICATION The receiver need not be removed from its cabinet Receivers do not need the many indicators or console to perform these steps. (meters and lamps ) found on transmitters, but they are provided with some indicators that are useful in Step Indication Action troubleshooting. Not all of these are commonly re­ a. Malfunction of any Perform the steps garded as troubleshooting aids. kind affects only one given in Subsection Analysis of the indications enables the experi­ band or some of the 1-7, Single- Band or enced technician to identify the general area where bands or channels Single-Channel the malfunction exists. Removal of the receiver and Malfunctions use of test equipment may be required then only to identify and replace the defective component. b. Receiver com­ Perform the steps The less experienced technician can locate the pletely inoperative given in Subsection origin of the malfunction by noting the receiver 's l-7. Receiver In­ malfunction indications and using either cause-and­ operative effect logic or the systematic trouble shooting pro­ cedures following. The Preliminary Troubleshooting c. Input meter indica­ Perform the appro­ Procedure is first used to determine which of the tions low and out­ priate steps given following procedures to use. put absent, weak, in Subsection 1-7, or distorted Front-End and IF d. PRELIMINARY RECEIVER TROUBLE­ Malfunctions SHOOTING PROCEDURE These steps should be performed if the ap­ proximate location of the malfunction is not known.

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COMMUNICATIONS NAVSEA 0967-LP-000- 0010 GENERAL

Step Indication Action Step Indication Action

d. Input meter indica­ Perform the appro­ power is found at the tions are normal priate steps given primary. If not, but output is im­ in Subsection l-8, check for presence of paired AGC and Detector input power at each Malfunctions, which power switch, inter­ may direct that the lock, fuse, and con­ steps of Subsection nector. Correct any 1-8, Audio Malfunc­ open-circuited con­ tions, be performed nections

e. Poor selectivity Perform adjustments c. Tubes and panel Test all tubes on a and/ or sensitivity needed outlined in lamps light but transconductance Subsection l-8, Super­ receiver output tube tester, first heterodyne Receiver is absent testing receiver op­ Alignment Adjust­ eration after replac­ ments and given in ing any obviously bad detail in instruction (gassy or burned out) book tubes. Return to origi­ nal sockets any tubes f. A3 reception nor­ Test all components having at least half mal but no Al associated with BFO their specified trans­ reception by means of testing conductance and no tubes continuity, and internal shorts resonating induc­ tances, as well as d. All tubes test good Use a VTVM to test making tube socket but receiver output for the presence of voltage and resis­ is absent B-plus voltage at tance measurements several plates through­ out the circuit, includ­ ing those at the audio e. RECEIVER INOPERATIVE output local oscillator, Perform the following steps in the order given and an RF amplifier. if the receiver is inoperative, omitting any inappro­ If B-plus is missing priate ones. Test the receiver after each change at any point, search made. for and replace the defective component. WARNING If B-plus is absent Observe all safety precautions in per­ entirely, follow the forming the following troubleshooting procedures in Sub­ procedures. section l-7, Power Supplies

Step Indication Action e. Audio output absent With the receiver or at low level withdrawn, set the a. Receiver completely Check fuse(s) and re­ R F and AUDIO GAIN dead - POWER ON place if blown. Folc controls at their half­ lamp and tubes unlit low procedures in way settings and ener­ Subsection l-7, gize the receiver. Power Supplies, if Touch the tip of an the fuse blows re­ insulated-handle peatedly. screwdriver monen­ Inspect line cord and tarily to each second­ plug to make sure ary terminal of the they are in good con­ last IF transformer. dition and the plug is If a loud buzz or hum inserted correctly. is produced at the Measure line voltage speaker or headset, at receptacle and the following circuitry test - operate recei­ is operating; follow ver at a known good the procedures given receptacle in Subsection l-8, Front- End and IF b. Power input to re­ Use a VTVM or mul­ Malfunctions. If no ceiver present but timeter to test for in­ audio indication is receiver dead - put power at trans­ obtained, apply the POWER ON lamp former primary. Re­ tip of the screwdriver and tubes unlit fer to Subsection l-7, to the center terminal Power Supplies, if

ORIGINAL 1-51 ·, · ,

- - - - , , , ,

COMMUNICATIONS NAVSEA 0967-LP- 000- 0 010 GENERAL

Step Ind ication Action Observe all safety precautions in performing the following troubleshooting procedures. All final align­ of the AUDIO GAIN or VOLUME control. Fol­ ments should be done with the equipment enclosed as nearly as possible in its operating condition. Audible low the procedure given in Subsection l-8, AGC or metered audio output indications can be used in making adjustments; signals should be sampled at and Detector Malfunc­ stages (H F, IF and detector input) only in signal­ tions, if a loud hum or tuned tracing to locate the malfunction. buzz results. If it does not, follow the steps given in Sul>section l-8, Step Indication Action Audio Malfunctions. a. No indicated input Test all tubes in R F, IF, to receiver and AGC stages and re­ f. SINGLE- BAND OR SINGLE-CHANNEL place defective ones as MALFUNCTIONS in paragraph l-8, Re­ The steps of this procedure should be performed ceiver Inoperative, if a malfunction of any kind affects one or possibly two Step c. bands or channels. Test the receiver after each change b. No IF output, as Replace the oscillator made . tested in Subsection tube (s ) with a new one 1-8, Receiver In­ and test the receiver. Step Indication Action operative, Step e, Try another tube (s ) if but tubes known to this has no affect. Make a. No input indicated Determine the condition be good alignment adjustments and no audible out­ of the bandswitch or for all bands if the re­ put when malfunc­ channel switch. Adjust placement re stores op­ tioning band selec­ and clean contacts, or eration, otherwise make ted replace switch if neceo­ no adjustments and re­ sary. turn the original tube (s ) b. No input indicated Replace local oscillator to the socket but contacts and tube and test operation c. No output, but Set the signal ge nerator switched compon­ on malfunctioning band. IF tubes are known to to the frequency of all ents in good con­ Try another new tube if be good last dition this has no affect. Make IF transformer. modulated output, and adjustments for all 0. 5-volt amplitude. bands if this replace­ Insert the signal across ment restores opera­ the secondary terminals tion, otherwise make of the last IF transfor­ no adJustments and re­ mer. If no receiver turn the original tube output is found at any to the socket. In this setting of the AUDIO case, set the receiver GAIN cont rol and with to the malfunctioning AGC OFF, follow the band and continue steps of Subsection 1-8, troubleshooting with the AGC and Detector Mal­ procedures of Subsec­ functions . If output is tion 1-8, Front- End and satisfactory, insert the IF Malfunctions signal bet ween ground and the plate of the pre­ g. FRONT END .1\ND IF MALFUNCTIONS ceding stage (last IF The fol lowing items of test equipment, or amplifier or second their equiv·alents. should be used in troubles hooting mixer) by means of a reveiver HF and IF circuitry: series capacitor . If no 1. H F Signal Generator Set AN/ URM- 25 or signal is present, re­ AN/URM- 26 (selection dete rmined by frequency re­ place the IF transfor­ quired mer. If signal is pre­ 2. Multimeter J\ N/USIVI -34 sent go to Setp e for 3. Test-Tool Set l'> N/USM-3, 3A single conversion re­ 4. Dummy anteuna, Navy Type 66017. (This can ceivers and to Step d be constructed also by using the schematic diagram of for dual-conversion Figure 1-23 following, and enclosing the components receivers in a small chassis or box for shielding . In emergen­ d. Malfunction in IF Set the signal generator cies, a 200 pF capac itor can be used in series with circuitry (FOR to the first intermediate the antenna lead. DUAL CONVER­ modulated output, and Perform Step a and the appropriate steps follow­ SION RECEIVERS 0. 5-volt output ampli­ ing the order given, and test the receiver after each ON L Y) tude . Use same re­ change until the malfunction is located or corre cted. ceiver control settings

ORIGINAL 1-52 ...... - .. ·,- ..- ..-

COMMUNICATIONS NAVSEA 0967-LP-000- 001 0 GENERAL

SHIELDED CAN ------, r I

I 20..u.H I TO RECEIVER I I 0 200 pF ANTENNA TERM. ANTENNA I I LEAOS I I 400 pF 400 n I TO RECEIVER I • 0 • 0 L ------_... CROUND TERM.

Figure 1-23. Receiver Dummy Antenna, Schematic Diagram

Step Indication Action Step Indication Action

as in Step c previous. oscillator frequency to Insert the signal at the measure the amplitude second mixer signal and frequency of the grid; if an audio output second injection signal does not result, the where applied to a grid malfunction is in the of the second mixer. second mixer or second e. Malfunction in IF Insert a 0. 02-volt modu­ oscillator circuitry. Use circuitry (FOR lated signal of the fre­ a VTVM to make voltage SINGLE-CONVER­ quency last used (Step and resistance measure­ SION RECEIVERS) c for single-conversion ments at these two soc­ and Step d for dual con­ kets; compare the meas­ version receivers) at the urements with the nor­ signal grid of each IF mal values given in the amplifier and the first technical manual and mixer, progressing replace any defective from last IF amplifier components found to be to first mixer . Decrease causing incorrect values . the amplitude by a fac­ The oscillator is not tor of 20 for each stage operating if its normal progressed. When a negative bias is not pre­ grid is reached from sent; in this case, test­ which the signal does substitute a new crystal not get through, insert (of the same frequency) the signal at the next or, if frequency is LC­ HIGHER amplitude step controlled, check the L at the plate just passed, and C components. Then using a capacitor in se­ test- substitute a new ries to the plate termi­ oscillator tuhe, trying nal. If the receiver out­ a second new tube if the put is missing, test the first replacement does condition of the IF trans­ not restore operation. former following and the If the oscillator func­ components in the grid tions properly but no circuit of the following receiver output is ob­ stage . Replace any found tained with signal in­ defective. If the receiver jection at the mixer output is regained with grid, use an oscillo­ signal injection at an IF scope with sweep set to amplifier plate, make a submultiple of the

ORIGINAL 1-53 I'

.. - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

Step Indication Action Step Indication Action

voltage and resistance h. No receiver out­ If receiver output is not measurements at the put, but first mix­ obtained at the end of amplifier socket, com­ er and all following Step e or g use voltage pare them with normal circuitry known to and resistance measure­ values, and replace any be operative ments at the first local components causing ab­ oscillator socket to id­ normal values. If the entify components re­ grid voltage is more sponsible for any incor­ positive then normal, rect values found. Ab­ check leakage in the sence of negative grid IF transformer, driv­ bias indicates that this ing it by removing the stage is not oscillating; tube and measuring the in this case, test the DC voltage developed condition of and correct from transformer sec­ any defects in the L and ondary to ground. Go C components and to Step g if the IF sig­ switches associated nal gets through to the with this stage. Clean receiver output, from the tuning capacitor the mixer plate, but not plates and inspect for from its grid. Go to damage or physical Step h if it is heard misalignment. Use an when inserted at the oscilloscope, if de sired, grid, but not at the to determine approxi­ antenna. mate oscillator frequen­ cy and amplitude at its f. Receiver output Check FILTER IN/OUT present when sig­ or ON/OFF switch for plate and at the mixer grid coupled to it, using nal injected at correct operation. By­ frequency-determining out put of filter, pass the filter with a but absent when test load and signal in­ methods described in Test Methods and Prac ­ signal injected jected at earlier stage tices. ElMB NAVSHIPS at filter input if an IF transformer is not part of the filter. 0967-000-0130. When the oscillator is func­ Replace filter if this tioning correctly, set restores operation or the injected frequency to test filter if it in­ for the maximum out- cludes the IF trans­ put indication (using as former. little RF GAIN as pos­ g. No receiver out­ If the first IF signal sible) to determine if put, but first IF does not get through the the receiver is in align­ transformer and mixer tube, Step e, ment; if it is not, align all following cir­ make voltage and re­ each band. Then test cuitry is known sistance measurements receiver operation with operative, as at mixer socket to id­ the same signal applied tested in Step e. entify components to the antenna terminals causing incorrect val­ at the 5-JJ.V level. ues. Replace defective i. No receiver out­ Retain the signal gen­ components and verify put, but conver­ erator and receiver that the receiver oper­ sion and IF cir­ control settings used at ates with the signal in­ cuitry are known the end of Step h and in­ serted at the mixer operative sert the signal at the grid with both receiver plate of the last (if more and signal generator than one ) RF amplifier. control settings un­ Increase the RF ampli­ changed from step e. tude to about 100 v. If satisfactory oper­ J.1. Absence of receiver ation results, make output indicates that the tests with injection of malfunction is in the R F signal, according R F tuned circuit or the to instructions in Step bandswitch; test the h following. components involved and switch adjustment and condition. Replace

ORIGINAL 1-54 . . ,- ... - ,- ,-

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action h. AGC AND DETECTOR MALFUNCTIONS Automatic Gain Control (AGC) and detector mal­ components or adjust, functions are identified by the following steps, some clean, or replace the of which require an RF signal at the receiver antenna switch to correct the terminal. This signal is provided by a signal generator malfunction. set for a modulated 5-fi.V or 10-fl.V output at the same j. No receiver out­ Reduce the signal gen­ frequency to which the receiver dial is tuned. Per­ put, but last erator amplitude by a form the applicable steps following in the order given tuned RF circuits factor of 20 and advance and test the receiver after each change to determine and following c ir­ the signal injection to if acceptable operation has been restored. cuitry known good the grid of the last R F amplifier tube . If the Step Indication Action signal is not present at the receiver output, a. No or low receiver Test AGC diode, detec­ make voltage and re­ output; AF signal tor diode, and tubes in sistance measurements present at detector all associated stages. at the tube socket. Re­ output Replace all tubes having place any components internal shorts or a causing incorrect val­ transconductance of ues, and if audio sig­ less than half the nor­ nal is still absent, try mal value tube substitution b. No or low receiver Use VTVM to make k. No receiver out­ Retain same settings output when AGC voltage and resistance put, but last RF and transfer signal in­ On; tubes known measurements at soc­ amplifier and all jection to the plate of good kets of AGC and detec­ following circuitry the preceding RF am­ tor stages. Compare known good plifier and follow the values with normal instructions of Step i values to locate and for tuned curcuit trou­ replace components bleshooting if no sig­ causing incorrect val­ nal is found. Then use ues. Note po ssible the procedures of Step causes of high (positive) j with the signal injected AGC voltage in Step c. at the grid of this tube. c. No or low receiver Measure DC voltages Repeat these procedures output when AGC at AGC- controlled R F with any additional RF either ON or OFF amplifier grids and IF amplifier stages, being transformer secondaries certain to reduce sig­ if AGC-line voltage is nal amplitude by a fac­ high-near zero or posi­ tor of 20 for each addi­ tive (see Step e of Sub­ tional stage of amplifi­ section 1-8, Front- cation End and IF Malfunctions). 1. No receiver out­ If satisfactory receiver The positive voltage put, but all am­ output results when the must originate at the plifier stages signal is injected at the most positive point known operating grid of the first RF am ­ along the AGC line. plifier but not when Test quality of suspected applied to the antenna components and replace terminals, check all defective ones - usually associated connections an IF transformer or and switch contacts for tube good continuity, and d. No detector output, Make voltage and resis­ especially the latter for as detemined in tance measurements at cleanliness and adjust­ Step e of Subsec­ detector socket, locate ment . Check condition tion 1-8, Receiver components having in­ of all associated com­ Inoperative correct values, and ponents and replace replace them those found defective. If receiver operation is i. AUDIO MALFUNCTIONS not restored by these Perform the following procedures to locate and operations, try trouble­ correct audio malfunctions, using, where required, shooting by inserting a modulated 5-fi.V or 10-fi.V signal applied to the an­ the signal at various tenna terminals, at the same frequency to which the points in the antenna receiver dial is tuned. An audio generator connected tuned circuit. to the audio gain control can be used instead if it has been established that receiver operation is satisfactory up to that point.

ORIGINAL 1-55 ......

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

Step Indication Action Step Indication Action

a. No receiver out­ Test all tubes in the d. No receiver out­ Use signal tracer or put when signal audio stages and re­ put but all cir­ headset to sample the injection at detec­ place all those having cuitry through AF signal at the output tor output as test­ internal shorts or a output transfor­ transformer secondary ed in Step e Sub­ transconductance less mer primary is terminals. If absent, section 1-8, than half of the normal functioning check again with the Receiver In opera­ value load replaced by an tive equivalent resistive b. No receiver out­ Use the signal tracer load. Replace the put; AF output to probe for the audio transformer if the from detector signal at each of the signal is still absent known present following points and at and no short or open and tubes known an amplitude greater circuits are found. If good than that used at the the signal is absent across the dummy (re­ GAIN control by the sistive ) load, trouble­ factor in parentheses: shoot the normal load (1) AUDIO GAIN con­ by means of component trol, center tap substitution and inspec­ tion of the output jacks (2) Grid of first audio for correct contact amplifier (20) operation (3) Grid of second e. High hum level Test the condition (ca­ audio amplifier (20) present in re­ pacity, voltage with­ (4) Grid of third and ceiver output stood, and leakage of following audio ampli­ all B-plus filtering fiers (400, etc. ) capacitors in the re­ If the signal is absent ceiver. If this is not at a grid, test for its effective, test all tubes presence at the preced­ and replace those with ing plate . If it is not internal shorts found there , make volt­ f. High hum level Short or ground for re­ age and resistance pre sent in re­ ceiver antenna input measurements at the ceiver output; for all following tests . socket of that stage , tubes and test Vary the AUDIO GAIN locate components good control between its causing incorrect val­ two extreme positions. ues, and replace them. If the hum changes in If the signal is found level in response to at the plate tested this it originates in previously, determine the R F, IF, or detec­ the condition of the tor circuitry. Locate components coupling the stage originating the two stages. Re­ the hum by use of a move the tube follow­ 0. 1-llF capacitor to ing and measure the short the signal to DC voltage (for indi­ ground at each RF and cation of leakage ) on IF amplifier grid in the grid side and the sucession, starting at signal amplitude (for the last AF amplifier. indication of coupling) At the point where the on both sides of the hum disappears, the capacitor. capacitor must be c. No receiver out­ Test for pr esence of shunting it to ground put but AF and all B-Plus voltage at both within the stage fol­ preceding circuitry plate and B�plus termi­ lowing its source. functioning nals of the output trans­ Check all components former; replace the in this stage and re­ transformer if B-plus place that introducing is applied to the trans­ the hum-usually a tube former but is absent filament-to-cathode from the plate terminal short, which may ap­ pear only when the tube is hot. Tube substitu­ tion will be necessary

ORIGINAL 1-56 ..· . . .. - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

Step Indiction Action Step Indication Action

to identify this cause. is not effective, return Lead dress may be the original tube to the critical and can be ex­ socket and tap each perimented with if it associated component has been previously under the chassis to altered find the one that is sensitive to vibration. g. High hum level If the hum level was Typical causes are originating in AF unchanged by variation mic rophonic tubes, circuitry present in AUDIO GAIN setting, poor electrical con­ in receiver output the hum originated in nections, and occa­ the circuitry following sionally defective the volume control - components the AF circuitry. Use the methods of Step f j. SYNCHRONOUS COMMUNICATION to locate stage in which RECEIVERS the hum originates Communication requiring close synchronization h. Intermittent noise Lift one side of the en­ of transmitter and receiver frequencies (such as SSE, present in re­ ergized receiver (with ISB, FSK, and MUX) can be accomplished using any ceiver output the antenna shorted) a of the following three means of reception: quarter of an inch 1. A conventional communications receiver above the work bench having adequate BFO power, AGC adapted to sup­ surface and let drop. pr essed-carrier reception, narrow-band selec­ If no change in inter­ tivity, slow tuning rate, and stabilized oscillators. mittent noise results 2. A conventional receiver used in conjunction and if noise is con­ with a terminal unit which accepts the receiver IF stant in occurrence, and supplies sideband selection and filtering, injected follow the procedures carrier, and AFC where required. of Step f and g to lo­ 3. A specialized synchronous communication cate the stage and receiver having frequency- setting precision and component causing stability which permits reception at the synchronous the noise frequency without requiring special tuning indications or having any subsequent frequency drift. i. Intermittent noise If dropping the side of Malfunctions in conventional receivers can be present in re­ the receiver slightly identified and corrected by use of procedures given ceiver output in in step h. previous previously. Many of these procedures are useful in response to mech­ altered the noise mo­ SSE troubleshooting also; those following can be used anical vibration mentarily, locate its without change : origin by varying the l. Receiver Inoperative. AUDIO GAIN setting Single-Band or Single-Channel Malfunctions. as in step f previous. 2. 3. AGC and Detector Malfunctions . If increasing the set­ 4. Audio Malfunctions . ting increases the vol­ The previous steps should permit troubleshoot­ ume of noise, use a ing all of the specialized SSE receiver except for small (one-fourth di­ frequency synthesis, comparison and control; hetero­ ameter) alignment dyning; and detection circuitry. Analysis of any tool to gently tap each frequency generation and control malfunctions or use tube in sucession, be­ of the SSE troubleshooting procedures, will determine ginning with the first what further procedures should be used. Some of the R F amplifier and end­ RF Oscillator or Frequency Source Malfunction pro­ ing at the last IF am ­ plifier. In evaluating cedures in the Transmitter section of this chapter will be useful in troubleshooting the SSE receiver intermittent noise, frequency generation circuitry. These procedures bear in mind that the are listed following and are referred to in Subsection tube characteristics 1-8, Single-Sideband Receiver Troubleshooting. for front-end applica­ 1. R F Output is Unsatisfactory on Only One tions result in micro­ Band or Channel . phonic effects, which are amplified by the 2. RF Output is Absent From Frequency Source. stages following. Tap 3. Output of Frequency Source is Too Low in each tube at least once Amplitude . from directions 90 4. Output of Frequency Source is Off degrees opposed. Frequency. Test-substitute a new 5. Frequency Errors Originating in Frequency tube for one producing a high level of inter­ Synthesizer. mittent noise. If this 6. Frequency Control Circuit Malfunctions.

ORIGINAL 1-57 ,-

COMMUNICATIONS NAVSEA 0967-LP-000- 0010 GENERAL

(1) Principles of Single-Sideband Reception modulator itself is the same in both applications. The characteristics of the single-sideband Several such balanced modulators can be used in emission are given in Subsection 1-2, Types of specialized SSE receivers for obtaining successive Emission. In A3 communication, audio intelligence sum and difference frequencies, as shown in Figure is detected as simultaneous beat frequencies between 1-24. The final frequency injected restores the car­ the carrier and the many radio frequencies forming rier; no additional demodulation stage is needed. the sidebands, but in SSE transmission there is no (2) Alignment Adjustments on Single-Sideband carrier and hence no beat notes. The simplest means Receivers of obtaining SSE reception is by using a conventional Single-sideband receivers have RF and IF align­ receiver, which supplies a beat oscillator frequency ment adjustments that are similar to those of the con­ as a " substitute carrier" to beat with the sideband ventional superheterodyne receiver, in addition to frequencies. This "substitute carrier" is inserted as those required for SSE receivers only. These addi­ an intermediate frequency, and diode detection is used. tional adjustments are injection oscillator amplitude, Unfortunately, there is no such thing as an " exact" fre­ modulator balance, sideband selection filters, and quency setting on most such receivers, and the best the source frequency. Oscillator frequency adjust­ oscillator frequency requires periodic resetting to ment to retain dial calibration may be required as a retain intelligibility. result of normal component aging and following re­ These inadequacies of the conventional com­ placement or replacement of an associated component, munications receiver are retained when a single­ to minimize any input frequencies appearing in the sideband converter is used in conjunction with it. output. Tuning precision and frequency stability are limited The functional block diagram of one type of SSE by dial readability and local oscillator stability, al­ receiver front end is shown in Figure 1-25. Note that though sideband tuning and filtering are improved the desired frequency is selected by setting the proper with use of the converter. reference frequencies and then tuning the associated Recent receivers designed specifically for SSE oscillators to each component of the reference fre­ reception incorporate elaborate means for frequency quency by means of tuning indicators. The RF cir­ selection, control, and compensation. Some of the cuits, first (HF) oscillator, and harmonic selector more common are: filter are ganged together in such equipments, re­ 1. Use of a crystal oscillator and selection quiring precise alignment for good tracking. Some of frequency-dividing and frequency-multiplying equipments make use of a variable IF frequency, with circuits to produce reference signals at the desired the added requirement that the variable IF transfor­ frequencies. mers be aligned to track with the ganged components 2. Enclosing temperature- sensitive, noted previously. frequency-determining circuits in an extremely (3) Single-Sideband Receiver Troubleshooting stable crystal oven. The following procedures are to be used in 3. Use of frequency comparison circuitry to troubleshooting specialized SSE receivers. They compensate for error or drift of the individual in­ refer, where appropriate, to steps used in trouble­ jection frequencies. shooting conventional receivers. Many of these equipments obtain heterodyning Test equipment of precision and stability com­ frequencies from phase-lock oscillators, the fre­ parable to these receivers should be used in making quencies being compared with and maintained at the alignment and calibration adjustments. Frequencies selected reference frequencies. can be measured by means of an electronic counter Local oscillator stability is increased by using EPUT counter ) calibrated as a secondary standard. step- type LC selection of harmonics of stable fre­ Use the appropriate following steps in case of quencies, which are obtained by division of a crystal­ malfunction, testing the operation of the receiver or controlled frequency. This fundarr.ental frequency the defective stage after making any change or can easily be calibrated by comparison at a test point adjustment. with a Ships Standard Frequency or WWV trans­ mission. The accuracy resulting is far greater than Step Indication Action could be obtained by continuously variable or step­ type LC control of the oscillator. In some equip­ a. Receiver inopera­ Follow appropriate ments, the desired frequencies are set by switching, tive steps of Subsection the local oscillator tuned to the identical frequency, 1-8, Receiver Inop­ and error- and drift-compensating circuitry used in erative, except in the generation of a heterodyning frequency to keep Step e substitute the the total of the beat frequencies stable. The step­ steps following for type control permits the receiver to be set to a those of the Subsection scheduled frequency, rather than tuned to a received 1-8, Front- End and signal. IF Malfunctions, ref­ Single-sideband R F signals can be obtained in erence. Step c, tube one method, by phasing processes resulting in the testing, may be defer­ suppression of the carrier and one sideband. Bal­ red if receiver has anced modulators can be used in a more common many tubes, and none method since they obtain the difference and sum fre­ are obviously defective . quencies but exclude the input frequencies from the b. Ope ration on one Follow appropriate output. The desired sideband can be retained by band or channel(s) steps of Subsection 1-8, filtering after the balanced modulator in a trans­ absent or im­ Single-Band or Single­ mitter; this sideband is selected by filters before paired. Channel Malfunctions. demodulation in a receiver, but the balanced

ORIGINAL 1-58 .. () 0 0 :;:o ,, ...... � GJ � ...... c:: 2: ::z ...... );::> () r :P -·- >-l

TO TO 1.5 TO TO TO TO 02: \�7 7 I ST. MIXER rn 2 NO. MIXER RF BANDPASS 1.5 I ST. IF 1.5 0 SIDEBAND 7. 002MHz 7.002MHz (BALANCED 1.5002MH� 1.5002MHz 1.5002MHz (BALANCED 0.002MHz AM PLIFIER FILTER AMP LIFIER FILTER MODULATOR ) MODULATOR ) I

OTO ,, 1.5 5.5 MHz MHz 2kHz ::z );::> < Vl IT! );::> 0 1.0 - BUFFER- BUFFER- If 0'1 I '-.1 \]' I � AM PLIFIER AMP L IFIER AM PLI FIERS r \J I 0 0 0 j I AF 0 0 ,, OUTPUT J __, 0 5.5MHz 1.5 MHz

I ST. 2 NO. INJECT ION INJECTION F REO UENCY FREQ UENCY OSC ILLATOR OSC I LLATOR cr1lf<> OR .. t <>---+<>il� Cl ttl ,, z �·� ttl I�!� I ::0 ::t> Figure 1-24. Single-Sideband Receiver, Block Diagram r n 0 s: $ c::: (14 . 205 IF 220 kHz 80 kHz �n RF MHz) MIXER 17lnMHz 17 0 MHz MIXER 220kHz 220 kHz MIXER 80kHz ;, AMPLIFIERS 2 IF IF I, AMPL IFIERS NO. I N0.2 N0.3 l FILTERS FILTER AMPLIFIERS 0::l z (f) ( .A'.....__--J A fl. 80 kHz (15.925 MHz) 1500 kHz SIDEBAND I 140kHz I VARIABLE AMPLIFIER AMPLIF ER HIGH TUNING I Fl NAL AF OUTPUT I FREQUENCY & 1500 kHz l 140kHz � INDICATOR MIXER I OSCILLATOR FILTER FILTER (TUNER DIAL) I / / / :z I )::> / (15.925 MHz) 1500 kHz 140kHz < J------' (./) 1 ,...... / ITT r �r )::> '· LIFIE 6 ARIABLE kHz AMP R ( kH75z) V 0 I MIXER MIXER ...., ... MIXER 825 - 1825 kHz 825kHz ....,. INTERPOLATION \0 - NO. 5 0'\ N0.4 ( 7 5-.. N0.6 ...... I I FILTER OSCILLATOR 6 � ...._�,...---' kHz) I 0 I r­ CARRIER -o I / I (15.1 MHz) TUNING (815 kHz) RE -IN­ 0 KILOHERTZ SERTION 0 I �.- �------� 0 SIGNAL I 0 I OVEN 1 kHz 0 1 TUNABLE 720kHz TUNABLE TEMPERATURE SP I 1 ECTRUM 0 : 'i FILTER t,�::��� GENERATOR 2� FILTER � / / 8 j '· I / / I X lOOkH 20 kHz I / z � 1 1 / 1 � I I FREQUENC F y FRE UENC Y I MHz � ��� I � �����:; Q Y I SPECTRUM C Y T MH 20kHz I 80 kHz I lOOkHz DIV DE R _. MULT IPLIER - GENERATOR I , FREQUENCY .. X 1 ! 10 1--il----t--..� I I X IO 1/ STANDARD X 1/5 X 4 I I I L------� MEGATUNINGHERT Z REFERENCE FREQUENCY SOURCt

Figure 1-25. SSB Receiver Front End Using Frequency Synthesizer as Frequency Heference .. . .

NAVSEA 0967-LP-000-00 10 COMMUNICATIONS GENERAL

Step Indication Action Step Indication Action

c. Receiver output is Follow the appropri­ Use an oscilloscope absent or impaired; ate POMSEE step to with horizontal sweep input meter gives determine the condi­ triggered by an ac­ normal indications, tion of the receiver curately calibrated but output meter in­ AF circuitry. If no oscillator to determine dication is low or such step is found, (by use of Lissajous absent inject a 0. 5-volt AF patterns ) the injection signal at the center frequency. Trace it tap of the AUDIO from the oscillator GAIN control; receiver to the grids of the AF circuitry is opera­ associated modulators tive if normal receiver or mixer used. If the output is obtained. injection signal is ab­ Proceed to Step d if sent, use the appro­ A F operation is satis­ priate troubleshooting factory. Use steps procedures of Subsec­ given in Subsection tion 1-6, RF Oscil­ 1-8, Audio Malfunc ­ lator or Frequency tions, to identify and Source Malfunctions. correct the cause of If it is not at the cor­ any audio malfunction rect frequency, make found. the required adjust­ ment. d. Receiver output is Set an RF signal gen­ absent or impaired, erator for a 0. 5-volt e. Receiver out­ Set the signal genera­ but AF circuitry is unmodulated carrier put is absent tor to the next-to-last known to be function­ output at a frequency or impaired, intermediate frequency ing correctly. differing from the re­ but AF and used, output unmodu­ ceiver 's last inter­ last IF circuit­ lated and attenuated mediate frequency by ry are known to by a 1/20 factor for an audio beat. Apply be functioning each amplification this signal to the grid correctly. stage. Inject this of the first IF ampli­ frequency in turn at fier pre ceding signal each grid having such demodulation . (If nec­ an input. Proceed to essary, swing the Step f if normal indi­ generated signal ac ­ cations are found ross the known inter­ when receiver is mediate frequency operated. If the nor­ until tuning setting is mal signal is absent found. ) If normal out­ or impaired at any put is present, test grid tested, follow preceding IF stages the procedures of of this frequency by Step d to test for the applying the signal presence of the re­ (reduced in level by quired heterodyning a factor of 15 or 20 injection frequency for each stage ) to and to test the cir­ each preceding grid cuitry involved. in turn. Proceed to f. Receiver output Set signal generator Step e if indications is absent or im­ to any further inter­ of normal reception paired, but re­ mediate frequency are found. Use tech­ ceiver is opera­ used, unmodulated niques of tube testing tive from the output, and a level or tube substitution, next-to-last IF determined by the signal tracing, tube stage onward . number of amplifi­ socket measurements, cation stages follow­ and measurement com­ ing the injection parisons to locate the point. point where the signal is lost or impaired. Use the test proce­ Use Step c of Subsec­ dures and corrective tion 1-8, AGC and measures given in Detector Malfunctions. preceding Steps rl if AGC- controlled and e to correct any grid voltage is too malfunctioning. high.

ORIGINAL 1-61 - - - - , , , ,

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERA L

Step Indication Action Correct Indica- Correct Indica- Operation at Step lion at Remote tion at Con- g. Receiver output Use Lissajous-pattern Remote Unit Unit trolled Unit is absent or im­ presentation to deter­ paired, but is mine the first injec­ a. Depress POWER indi- POWER indica- known to be opera­ tion frequency. Adjust ST ART cator ener- tor energized tive from first IF the signal generator switch for gized (B-plus applied stage onward. for a frequency having 3 seconds to transmitter) an audio difference from the frequency b. Depress CARRIER ON CARRIER ON to which the receiver handset indicator ener- indicator ener- is tuned (unmodulated push-to- gized and gized and car- and at a 100- to 1000- talk switch associated rier transmitted IJ.V level) and inject (for phone loudspeaker in normal it at the grid of each operation) amplifier operation RF amplifier in turn, muted progressing from the c. Operator Receiver out- Transmitter first balanced modu­ telegraph put muted keyed and car- lator or first mixer key (for CW during key- rier transmitted to the receiver an­ operation) down intervals in normal tenna input. Use operation general malfunction- · isolating procedures d. Talk into Loudspeaker Modulation given previously to handset amplifier during normal identify malfunctions transmitter muted as tn operation in the area where the with push- Step b. injected signal is to-talk lost. Do not over­ switch still look the condition of depressed switch contacts or e. Release CARRIER ON CARRIER ON RF inductors. push-to- indicator de- indicator de- talk energized and energized and 1-9 REMOTE CONTROL UNITS switch associated tran smission amplifier stopped during Remote control units are used to control trans ­ demuted normal opera- mitters and receivers from remote phone or telegraph tion stations. The transmitter and receiver are tuned at f. Depress POWER POWER indica- the equipment location and only POWER (transmitter STOP indicator tor deenergized B-plus power ), CARRIER ON (transmitter busy ), and switch deenergized (B-plus removed receiver muting switching are controlled from the from trans- remote units. mitter) The troubleshooting procedures following are intended for use with the most commonly nsed Con­ trols, Radio Set C- 1 138/UR and C- 1207/UR, and b. INDICATOR AND CONTROL TROUBLE­ consequently refer to voltages and terminals found SHOOTING in these equipments. This has been done to enable Use the appropriate steps among the following them to be as useful as possible; the procedures can for malfunction in the indicator and transmitter con­ be applied to other similar equipments if the correct trol circuits until proper operation is restored or the voltages and terminal designations are used. malfunction identified.

a. PR ELIMINARY MALFUNCTION VERIFI­ Step Indication Action CATION a. POWER indicator Replace bulb if burnt Since this equipment is used by many persons, and I or transmitter out . De termine con- the electronics technician maintaining it may wish to cannot be energized dition of ST ART switch. verify the symptoms of units reported malfunctioning. Measure J15/230V AC The following quick-check procedure can be used for input to remote unit at this purpose. It requires the presence of a man at terminals 2 and 4 of the remote unit and another at the controlled equip­ TB 101 or E102. Make ment, with telephonic communication between them sure that POWER in­ or use of a prearranged sequence and timing of test dicator series resistor steps. The transmitter need not be on the air but is not jumpered for should be energized to an extent enabling it to indicate 230-volt operation. when it is keyed or modulation is applied. b. No 115/230 VAC Test for presence of power input power at transmitter. present Test for power at switchboard (if any ) Test wiring and con­ nections for continuity.

ORIGINAL 1-62 . - ·--· .. -·-·------'---

('l 0 ;;:;: EI02 ;;:;: r--- c:: z..... I ('l { ...IIP START :l> TRANSMITTER 2 SIOI .. START-STOP ..th, :j 3 lJ-1 STOP 0 CONTROL z RIO! Ul 4 J 1 {0)1 101 POWER 5 CW KEYING Jl04 CIRCUITS { 6 d KEY J\03 RI02 c ' - >I ;;nPHONES XMTR 12 VDC 7 - � T n.? l :z RELAY SUPPLY { 8+ ):::o 3 < MODULATION TO 9 Vl 6000 ]"101 TRANSMITTER I'T1 10 �� ):::o { 5 J 2 PTT KEY ING II n 0 ; K\02 ... 1 "' , "x�.rrR BUSY" 12 J IOI 0"1 ""-.! - - I RI05 HANDSET I � I "" E OR r- '""' � ESTSET " CH I 1102 tP AUDIO TO 20 0 17 0 CARRIER SPKR-AMP 19 0 { � J\02 I AUDIO FROM 14 "'- A 0 r'03 · MICROPHONE 0 RECEIVER 13 n 8 7 I 2 3 22 21 JEARPHONE 0 { LEVEL

I . r 9 10 II . 2 L_ :�: ' o-- � A __3, -,, '· B' A 8 c D E L--

Figure I -26. Wiring Diagram of Typical RPU, C-1138/UR .

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COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action ----- c. POWER indicator Check transm itter pow­ with equipment ener­ energized only er relay for coil con­ gized, POWER ON, while START but­ tinuity and contact handset removed from ton depressed condition holder, and push-to­ talk switch operated. d. POWER indicator Determine condition Each of these voltages and/ or transmitter of STOP switch. Check should be between 4 not deener gized continuity of STOP and BVDC and their when STOP button switch wiring to trans­ sum equal to the input depressed mitter. Determine con­ voltage. dition of power relay coil shunting resistor. c. 12VDC measured Replace the transformer Check adjustment and across audio trans­ if use of an ohmmeter condition of power re­ former primary verifies that the trans­ lay; clean and adjust during operation in former winding is open if necessary Step b.

e. CARRIER ON Replace bulb if burned d. 12VDC measured Test all connections and indicator can­ out. Measure voltage across microphone switch contacts in oper­ not be energized at terminals 7 and 8 during operation ating position for con­ of TB 101 or E102 in Step b. ti nuity to microphone. (should be 12VDC) Clean and adJUSt if re­ quired. Replace mi cro­ f. 12VDC not pre­ Check for presence of phone if its DC resis­ sent at remote 12VDC at transmitter. tance (as measured by an control unit Check for presence of ohm-meter) exceeds 60 12VDC at switchboard. ohms or is less than 20 Check wiring and con­ ohms. nections for continuity

g. CARRIER ON in­ Check contacts and ac­ d. HA NDSET RECEIVER (EARPHONE) dicator not ener­ tion of handset push-to­ TROUBLESHOOTING gized by 12VDC talk switch. Check Use the appropriate steps among the following present at remote remote unit relay coil for malfunctions of the handset receiver circuits, control unit continuity, action, and until proper operation is re stored or the malfunction contact condition identified.

h. CARRIER ON in­ Check adjustment of Step Indication Action dicator and I or handset push-to-talk transmitter. RF and holder switches. a. Handset receiver Verify that the ear­ output not deen­ Clean and adjust arma­ inoperative phone level attenuator ergized when ture gap and contacts is at its maximum handset push­ of CA RRIER ON muting clockwise rotation and to-talk switch relay. the radio receiver is released operating. Measure the AC (audio fre­ c. HANDSET TRANSMITTER (MICROPHONE) quency) voltage at TROUBLESHOOTING terminals 13 and 14 Use the appropriate steps among the following of TB102 or 103. for malfunctions in the handset transmitter circuits, Measurements of up until proper operation is re stored or the malfunction to 15V RMS are normal, identified. depending on the radio receiver audio gain Step Indication Action setting.

a. No handset trans­ Check terminals 2 and b. No A F input to With radio receiver mitter output at 4 of TB101 or E102 for remote unit still operating, dis­ terminals 9 and 10 presence of 12VDC. If connect the input leads of TB101 or E102 not present, check to terminals 13 and 14 (should be approxi­ source of 12VDC (in of TB102 or 103and mately 4V RMS transmitter) and con­ again measure the sig­ when push-to-talk tinuity of connecting nal across these leads. button depressed wiring and terminals If there is still no in­ and microphone put, check the radio spoken into) receiver for output at the desired level, A F b. No handset trans­ Measure DC voltage connections and switch­ mitter output, but across audio transfor­ ing, and continuity of microphone supply mer primary and the audio distribution voltage present across microphone wiring to the remote unit

ORIGINAL l-64 . • .. - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

Step Indication Action Step Indication Action

c. Handset receiver Determine condition b. AF signal found Inspect the connections inoperative, but of earphone level con­ at output of re­ and wiring between the A F input is present trol and replace if mote unit but not amplifier and the re­ at remote unit defective . CAR RIER at input to asso­ mote control unit for ON muting relay should ciated loudspeake::­ continuity and absence not be energized; if it amplifier of short circuits. is, inspect handset c. A F output can be Measure the signal at holder switch for con­ measured at ter­ the amplifier end of tact condition and ad­ minals 19 and 20 of the amplifier end of the justment, cleaning and TBI02 or EI03 only inte rconnecting wi1·ing adjusting if necessary. when leads to asso­ to the remote unit and Verify that radio re­ ciated amplifier are receiving a signal. If ceiver output is pre­ disconnected the signal is absent, sent at terminals A check the line for an and B of handset hol­ open circuit. If the der switch. signal is present at d. A F signal is pre­ If the handset holder the amplifier end, sent at terminals switch has been in­ troubleshoot the am­ A and B of hand­ spected for correct plifier input circuitry set holder switch switching action, check d. A F voltage across Inspect the CARRIER in either position, the handset receiver terminals 13 and 14 ON muting relay to but no receiver and wiring for open is not the same as make sure thai it is audio output heard circuits; replace the that across ter­ not energized. Adjust receiver if defective minals 19 and 20, the handset holder e. Radio receiver out­ Check the handset TBI02 or El03, switch contacts if the put measured at receiver and wiring when handset is relay is energized. terminals A and B for a short circuit in holder Adjust the relay con­ of handset holder and replace the re­ tacts if the relay is switch only wh«n ceiver if it is found unenergized; normally hand set is in hol­ defective closed contacts C and der or handset re­ D should be making ceiver disconnected. good contact. After corrective action, e. TROUBLESHOOTING THE OUTPUT TO verify that the signal LOUDSPEAKER AMPLIFIER . input to terminals 13 Use the appropriate steps among the following and 14 appears at if the remote control unit output to an external am­ terminals 19 and 20 pl ifier appeat·s to be malfunctioning. e. Associated loud­ Adjust contacts C and speaker amplifier of CARRIER ON re- Step Indication Action 0 not muted when 1 ay so that they are a. Apparently no AF Leave handset in push-to-talk closed when the relay output from the ex­ holder after verifying, switc h is is unenergized and ternal loudspeaker as in Subsection 1-9, depressed open when the push-to­ amplifier driven Handset Receiver talk switch is depress­ by the remote con­ (Earphone ) Trouble­ ed. If the relay cannot trol unit shooting, that the pro­ be energized, check per earphone input is its coil for continuity, present. Measure the the D and E contacts AC voltage between ter­ of the handset holder minals 13 and 14 and switch for good con- terminals 19 and 20, d ilion and cor reel TB102 or EI03. If the adjustment, and the voltages measured are handset push-to-talk approximately the switch for good con­ same, measure the dition and correct ad­ voltage across ter­ ,iustment . Clean, ad­ minals of the loud­ just. or replace as speaker amplifier. If necessary. Verify that essentially the same the relay is energized value is measured when the handset is there, the remote unit held and the push-to­ is not causing the mal­ talk switch depressed function; continue troubleshooting the amplifier

ORIGINAL l-65 / ,- ,- ,- ,-

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action control capability. The three arrangements are: Type 1: Radiophone control units (RPU's) with f. Associated loud­ Attempt to secure transmit-receive handset. This type of RPU usually speaker amplifier desired muting action has an associated speaker-amplifier. Output level not muted when by adjustment of the control is provided for receive only. No gain control push-to-talk switch speaker muting con­ or amplification is provided for transmit. Figure 1-26 depressed, but trol. If this is not is a complete wiring diagram of a typical Type 1 RPU. switch and relay effective , measure Type 2: Master communications console . RPU action is the resistance of with transmit-receive handset having access to 16 satisfactory these dual potentio­ different circuits. A variable gain amplifier delivers meters; replace them the modulation signal to the transmitter. if this value is not Type 3: l\TTDS console. Receiver earphone and correct boom microphone . Modulation circuit provided with a

f. AUDIO DISTRIBUTION LEVEL OF TRA NS­ constant gain amplifier of about 10 dB gain. Trans­ MIT-RECEIVE PANELS AND REMOTE mitter keying accomplished by a foot switch. _1\ ccess CONTROL UNITS to 10 different circuits provided by a local console The standard audio level for distribution aboard switch. One of the common problems associated with ships is 0. 775 volts in 600 ohms. This is a meter read­ these remote circuits is that of unequal audio output ing of -7.8 dB of audio in the systems which use the level. Variation in RPU modulation output level can older 6 mW reference level, and a dBm reading in the 0 vary the transmitter output for each of the different the newer VU system which uses 1 mW as a reference level. All devices which receive inputs via the audio users controlling the same circuit. When the various distribution panel are designed to operate at this level , user stations controlling a given circuit are comprised of various remote arrangement types noted above, the and therefore all receivers supplying audio should be adjusted accordingly. Many terminal units can tol erate problems can be seriously compounded unless some a slightl y higher input, but at a risk ranging from dis­ effort is made to assure that the same audio level is tortion to physical cl amage. For example, a receiver provided by all user stations . Each transmitter supplies 12 VDC to all user delivering +20 dB above the prescribed output is pro­ ducing al most 8 volts of audio. It is obvious what can stations which control it . This supply operates the keying and muting relays in the remote control unit, happen when 8 volts is applied to a device intended to provides bias for carbon and transistor microphones, operate at about 0. 775 volts. and illuminates the "Transmitter busy" lamp (misnamed Some of the expected consequences of excessively­ "Carrier on" lamp) at all user stations for that trans­ high audio are listed below. How many do you recog­ mitter. a ship has a combination of the various types mze as malfunctions in your installation? If of remotes, it will be necessary to adjust the type 2 1. Signal distortion in Remote Phone Units and and type 3 remotes to give the same audio output levels TTY Terminal Units . as type There are a number of ways this could be 2. Uncontrollable feedback howl when usina a 1. done . Whatever system is used, it may happen that standard Navy handset at a Remote Phone Unit. b the audio output of a remote will vary because of 3. False triggering of TTY Terminal Units on variations in the 12 VDC voltage supplied by the dif­ noise. terent transmitters and also with the type and condition 4. Crosstalk between audio distribution circuits. of the microphone connected to the remote . When 5. Burning out of receiver output transformers, measuring and adjusting outputs of the remote units, or of terminal unit input transformers . TTY mark ­ they should be individually connected to the same space filters arP. frequent victims of excessive audio. transmitter. The microphone used with the remote Shipboard audio distribution is on twisted-pair should be the same that is normally used with that wires, usually terminated at each end in 600-ohm particular remote, and it should be tested to ensure transformer windings, of which the center tap is that is is operating correctly. the remote does not grounded at the receiver end onl\'. Both audio leads If have a controllable output, an attenuating pad made are 11hot, '' so care must be exer ised to avoid around­ � from resistors in a ' 'T '' arrangement can be used. ing either of them (at phone jacks or terminal boards Many ships have made a test jig for testing radio for example). A ground on one audio leg shorts one­ remote handsets. In its simplest form, the jig contains half the receiver output transformer, with a pos sibility an outlet jack and provides the proper relay /mike /lamp of transformer burnout. When non- standard equip­ voltage, proper termination, and an output meter to ments are routed through the audio distribution panel measure the microphone output level. The "output" (TCS, aircraft gear, and vehicular or portable equip­ function of a PSM-4 meter can be used. The addition ments for example) they must be modified to unground­ of an audio oscillator would permit a simultaneous ed or center-tap grounded audio in order to make them check of the earphone of handsets. More eleborate compatible with the standard Navy audio distribution test jigs could contain a cradle for the microphone that system. provides a fixed audible input at a fixed distance for precise measurements of microphone response. g. AUDIO LEVEL CONTROL AT RPU'S '. Audio input circuitry in a transmitter is designed Much of the Deet tactical communication is ac­ to regulate variable inputs in the range of about 20 dB complished over voice circuits. The nature of these (refer to Modulator Adjustments in Subsection 1-8 ). circuits requires that several users, usually physi­ Inputs can easily fall outside this range because of cally separated, have access to the same circuit. This excessive variations of audio output levels from radio access is provided at each user station by one of three remote units, improper setup of transmitter equipment, remote control circuit arrangements having transmitter

ORIGINAL 1-66 . .

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

or malfunctioning or misadjustment of equipment . grounded. Normal installation practice is for only The transmitter technical manual should be consulted the center tap of the receiver output transformer for guidance in setting modulation levels. to be grounded. Remote control units and speaker amplifiers are designed with center tap input trans­ For those transmitters which use a local micro­ formers, but center tap should not be used. With phone for setting modulation levels, there is an addi­ balanced audio lines, any current induced into one tional precaution: after all remotes are connected to line is also indu�ed into the other and these currents the transmitter, there may be a drop in the 12 VDC will cancel themselves as they proceed from opposite voltage when one unit is keyed. If a large number of ends of a transformer to center ground . This arrange­ remotes are used, the transmitter modulat ion should ment will provide isolation of approximately 60 dB if again be checked after all remotes are connected to there are no inadvertent grounds on the audio lines� the transm itters and the operator at the primary con­ If one side of the audio line is grounded, the line will trol station is sending traffic. If the transmitter is still be partially functional because of its balanced modulating correctly, then no attempt should be made nature, but it will be subject to severe crosstalk. to readjust the transmitter audio input controls. If Audio lines should be checked for inadvertent grounds. the transmitter is not modulating correctly, the tech­ This can be done by taking resistance measurements nical manual procedures for modulation adjustments to ground at the audio distribution board. A receiver should be tried again. If this still does not improve should show equal resistance to ground, and a remote operation, then audio level controls should be adjusted position should show no ground at all . Pieces of sol­ and a technician notified that there are indications of der, wire, and miscellaneous hardware falling into improper transmitter or remote station operation . the audio distribution panel or RPU are known to It is possible for the remote control unit to cause many shipboard problems. Another common modulate improperly even if the proper transmitter cause is improper wiring of the radio remote units adjustment procedures are followed. One fault could and speaker amplifiers. be poor regulation of the relay /bias voltage . This A maintenance program which includes audio will happen especially when the 12 VDC rectifier is distribution lines and receiver output level adjust­ of the selenium type . Another fault could be the ment should eliminate crosstalk, fe edback, and poor adjustment of the transmitter audio input ampl ifier modulation· problems. ( EIB 740) to accept signals from -10 dBm to +15dBm when the ac tual values of signals range from -25 dBm to -5dBm . 1- 10 TERMINA L EQUIPMENT Losses in audio line lengths used in shipboard Terminal equ ipment is needed to enable special installations normally do not significantly affect the types of signals to modulate radio transmission and modulation voltage amplitude unless there are faulty ' at the receiving end, to enable receiver outputs to terminal connections or damaged lines. All remotes operate monitoring and recording devices. Its most should provide the same audio level unless the micro­ common use is to modulate radio transmissions by phone or RPU impedances are significantly different. the start- stop, pulse-type code used by teletypewriters A substantial change in a remote handset microphone and, at the receiving end, to transform the signal impedance because of compacted carbon granules is received back into the start-stop code. not uncommon. If it is established that one RPU of Basic troubleshooting proc edures are given several on a circuit produces a low audio modulation in this section for the keyers (transmitting ) and the level where all user stations are of type I, the hand­ converted and converter-comparators (receiving) set mike is fi rst su spect, a bad line second, and used for teletype FSK (frequency-shift keying on Fl finally the control unit itself. emissions ) and facsimile (on F4 emissions ) communi­ The practice of connecting many receiving cation. Lo cal distribution systems and power supplies monitor outlets to a single circuit can seriously de­ are described briefly, but electronic cryptographic grade the primary station's receiving capability. equipment is not covered. Measurements made during BASE LINE II indicated Because of the unrelated natures of terminal that when four RPU's with handsets and amplifiers equipment, this section is divided by equipments. In were connected into a single circuit the received troubleshooting terminal equipment, use the steps signal was significan tly attenuated be low that when a given for the partic ular symptoms noted under the single RPU with handset terminate the circuit. equipment being serviced. Test the equipment either Pre-exercise examination and operational ob­ partially or in its entirety after any repa ir or ad JUSt­ servation of audio circuits indicated that lack of a ment is made. preventive maintenance program contributed signi­ ficantly to improper and unequal audio levels. '.Vhere a. TELETYPE AND FACSIMILE KEYERS line losses were significant, they were due to bad Keyers are used to transform the on-off (neutral ) terminal connections or part ially open leads. Where or plus-minus (polar) teletype signal into (fre­ obJectionable degr adation of receiving capability oc­ Fl quency-shift keyed RF signals, the frequency shifts curred, the number of users terminating the circuit occurring in response to changes in level of the tele� was usually excessive . Other causes of degr adation type signal . The keyers in use can accept an RF of receiving capability was that the AGC circuits of signal from an external source, usually a transmitter, the receiver were not used, and that RF and AF gain or can generate their own crystal -controlled RF. The control s were both set for maximum, thereby deliver­ keyer output can be used to drive any R F stage of the ing excessive and unregulated audio levels into the transmitter requiring a 20-volt AC signal. distribution system. Many keyers can modulate in response to voltage Crosstalk between audio lines aboard ship can vartatwns. between the extremes of teletype signal cause problems. To prevent crosstalk, the audio " levels, as well as at the extreme levels only. These lines aboard ship are of the balanced" type . This keyers can be used, in conjunction with a keying means that neither wire of the audio pair is directly

ORIGINAL 1-67 ,- ,- ,- ,-

COMMUNICA TIONS NAVSEA 0967-LP-000-0010 GENERAL

adapter, for F4 transmission of facsimile signals . Step Indication Action The keying adapter transforms the modulated order to locate defective 1800-Hz facsimile transmitter output into a direct components; replace current of varying voltage. This voltage is applied them to the keyer input for further handling in the same manner as Fl signals. If satisfactory F4 trans­ d. Output has only Determine if both MARK mission is not obtained during initial operation, the one condition, and SPACE levels are technician should first verify that the equipment used either SPACE present in the input sig­ is compatible and that the correct switch and dial or MARK nal, using a cal ibrated settings have been made. DC oscilloscope. (Sweep Use the appropriate steps from among those speed used is not criti­ following to identify and correct any malfunctions cal, since only the pre­ found in keyer equipments. It is assumed that all sentation of two parallel indicators (panel lamps and meters) are functioning lines is essential. ) Veri­ correctly. fy that keyer is set for the type of signal (neu­ Step Indication Action tral or polar ) suppl ied

a. Equipment not Inspect and if necessary, Input has only Troubles r,.:>Ot the signal energized when repair power cord and one signal source, local loop power POWER ON plug. Inspect fuses and level supply, and local loop indicator lamps replace any blown. Veri­ continuity do not light fy that power is present Both MARK and Test or test-substitute in line. If equipment is SPACE levels the following tubes: still inoperative, follow present in signal pulse limiters, ampli­ the procedures in Sub­ but only one fre­ fiers, reactance tubes, section 1-7 Power quency present in and output tubes. Use Supplies output the oscilloscope to trace b. POWER indica­ Inspect the plate fuse the input signal to where tor lamp lights and replace it if blown. keying or the R F is lost but PLATE indi­ Following the trouble­ e. Frequency shift Verify that MULTIPLIER cator does not, shooting procedures in is too wide or or XMTR MULT FACTOR nor does PLATE Subsection 1-7, Power narrow switch indicates the fre­ CURRENT meter Supplies quency multiplication de fleet occurring in the trans ­ c. Equipment has no Verify that control set­ mitter. or low R F output tings are correct Verify that the FREQ SHIFT or DEVIATION 1. If mal function Test complete operation setting is correct. exi�ts only when of keyer. Use a frequency meter R F input used Inspect the input selector or frequency shift moni­ switch for condition, tor (such as the OCT-2, action, and adjustment; -3) to measure the radio inspect all connections . frequencies at the MARK Test for presence of and SPACE conditions . RF input Deviation obtained Calibrate the DEVIATION 2. If needed RF Troubleshoot RF source does not conform control, using procedures input is supplied and connectors to dial scale indi­ given in the Corrective 3. No or low RF Test or test-substitute cation Maintenance section of output the RF output tube. the equipment technical Test or test- substitute manual the oscillator tube. f. R F output drifts Verify that equipment Test all tubes in the from original POWER is kept ON at equipment and replace setting all times so equipment those having internal can be energized im­ short circuits or low mediately by operating transconductance. PLATE switch to ON. Use an oscilloscope of Verify that the oven is suitable frequency char­ at the correct tempera­ acteristics to trace the ture (60° or 70° C. for R F signal from the os­ some equipments, cor­ cillator (or RF input) to rect value given in the the output stage. technical manual) and Use tube socket voltage that OVEN indicator and resistance measure­ lamp cycles on and off ments at the stage where properly the signal is lost in

ORIGINAL 1-68 . . .

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NAVSEA 0967-LP-000-0010 COMMUNICATIONS GENERAL

Step Indication Action Step Indication Action Thermometer in­ Adjust oven thermostat cable and connectors, dicates incorrect contacts according to from power line to the oven temperature directions in the techni­ comparator if the com­ cal manual. Replace parator or all three any oven-heating re­ units are inoperative sistors found defective or from the comparator chassis to the affected Thermometer in­ Inspect condition of converter. Check the dicates oven tem­ thermostat contacts; use input voltage compen­ perature variation burnisher to smooth sation connection (un­ contact surfaces if der chassis and adjacent necessary to the power transfor­ g. R F output fre­ Verify that the 200-kHz mer). Verify that pri­ quency incorrect signal is correct; if not, mary power is present adjust the 200-kHz oscil­ at the transformer lator If primary Check continuity of pri­ 1. If external R F Troubleshoot the exter­ power is not mary power leads from source used nal R F Source present at transformer through transformer switch to power input. 2. If keyer crys­ Measure crystal oscil­ tals are used lator output frequencies. If primary power Check the cable filter (Each should be 200 kHz is present at for continuity. Make below the desired RF transformer voltage measurements output frequency. ) If but equipment and compare with last these steps are not is inoperative POMSEE measurements effective, follow the made. Follow trouble­ appropriate steps in shooting procedures in Subsection 1-6, RF Subsection 1-8, Power Oscillator or Frequency Supplies Source Malfunctions b. Inoperative con­ Test or test-substitute verter or com­ the power rectifier. b. TELETYPE CONVERTERS parator; tubes Measure B-plus voltage A teletype signal at the output of a communica­ light up but power at both sides of choke tions receiver is composed of coded pulses of two indicator does not and check B-plus cir­ audio frequencies. In order to control the teletype cuit continuity. Use ap­ receiver, the pulses must operate a device which propriate steps in Sub­ keys the cur rent in a local teletype loop, either section 1-7, Power mechanically or electronically. Such a device is Supplies called a converter. In many cases, either space-diversity or c. Comparator output Check all switch and frequency-diversity reception is used at least part absent or impaired dial settings. Monitor of the time to insure reliable communication. Such when SELECTOR output when SELECTOR a setup requires two receivers and therefore two at COMBINED switched to CHANNEL A converters, with a comparator to select the best sig­ setting and CHANNEL B nal from the two available at each instant. Because Either (or both) Retune receiver to the of their close association, the comparator and the CHANNEL or channel received unsat­ two converters are usually supplied together as a A CHANNEL B in­ isfactorily, us ing input frequency- shift converter-comparator group. puts to compara­ meter indications for Each of the following steps gives instructions tor unsatisfactory tuning and converter for identifying the cause of a specified type of mal­ monitor oscilloscope function in converters and comparators. Use the indication for BFO steps appropriate to the equipment affected and the setting. symptoms noted. Steps a and b are for power supply malfunctions, step c is for determining the location Either or both Check receiver output and extent of malfunctions, and the remaining steps channel receivers with handset and with are for troubleshooting specific symptoms. It is cannot be tuned for VTMV for amplitude. assumed that all indicators are functioning correctly acceptable signal Compare with previous (panel lamps not burned out, for instance). POMSEE readings. If receiver is malfunction­ Step Indication Action ing, use steps in Sub­ section 1-7, Receivers a. A converter or Verify that the POWER the comparator switch in ON. Check the cannot be ener­ fuses (with chassis gized and neither withdrawn) of the mal­ power indicator functioning unit. Inspect nor tubes light up c-ondition of power

ORIGINAL 1-69 ·,

......

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action

Either converter Use a headset and VTVM continuity through con­ has an unaccept­ to sample the converter nectors to front and able output, as input; signal trace any rear-panel TTY outputs indicated by the radio lines and switches g. Comparator does Verify that both conver­ monitor oscillo­ involved if the receiver not permit as­ ter signals are present scope indication output is not pre sent at sociated teletype­ at the comparator SEL­ or the output the converter. If it is writers to print ECTOR switch. If either present, use the appro­ clear copy, al­ signal is not present, priate converter trouble­ though either use an oscilloscope to shooting Steps d through converter out- trace it from its DIV­ f. put will do so ERSITY input at the Both inputs to Verify that cables and rear apron to the SE­ comparator connectors involved are LECTOR switch The acceptable in good condition; then malfunction may be found but compara­ follow instructions of to be due to poor con­ tor output is Steps g through j for nections at the cable­ absent or troubleshooting the filter assembly, contacts impaired comparator at the SELECTOR switch, or connections at any d. Converter out­ Test all tubes or trans­ of the intervening put absent or istors in the converter connectors. impaired, as discriminator subunit. When both CHANNE L A indicated by Tubes having acceptable and Channel B signals monitor oscillo­ transconductance values are obtained at the scope and no internal short SELECTOR switch, circuits should be re­ monitor the compara- turned to their original tor output while turning sockets. Transistors the SELECTOR to the may be tested by most CHANNE L A, COMBINED, transistor testers with­ and CHANNE L B posi­ out being removed. Re­ tions successively place defective tubes or transistors . Use an Comparator out­ Inspect SELE CTOR oscilloscope and a sig­ put is obtained switch for dirty contacts, nal generator to trace at either CHAN­ poor adjustment , and the signal from the cable NEL but not at poor switching action. filter assembly input COMBINE D Clean, adjust, or re­ through the discriminator place as required subunit. Switches and h. Both channel sig­ Test all tubes or trans­ sealed filter units are nals present at istors of selector sub­ possible causes of selector subunit, unit and return accept­ malfunctions but comparator able ones to their e. Audio input is Test tubes of oscillator­ does not have original sockets . Use absent at PHONES keyer subunit. Return satisfactory out­ the oscilloscope to trace jack of converter good tubes to their origi­ put the signal and determine nal sockets. Use tube its level, starting at socket voltage and re­ SELECTOR switch sistance measurements Signal not pre­ Make voltage and resis­ and, if necessary, sig­ sent at keyer tance measurements, nal tracing with an os­ stage input at bases of selector di­ cilloscope to localize odes, axis-restorer defective components diodes, and axis-restor­ f. Teletypewriter Test or test-substitute er amplifier. Trace volt­ (with own loop keyer, trigger, and age changes through supply) fails to electronic-relay tubes these stages with SPACE­ print clear copy of oscillator-keyer to- MARK and MARK-to when plugged subunit. If this does SPACE level changes. into TTY jack not correct malfunction, (Reception of slow tape­ of converter. measure tube socket fed dots, R, and Y will (Note: diversity voltage and res istances fac ilitate evaluation of output may be to locate defective com­ the performance of unimpaired ponents and replace any these stages.} meanwhile) found. If necessary, Replace any defective trace (using oscilloscope ) components which cause the TTY signal through incorrect values or the subunit and check conditions.

ORIGINAL 1-70 . .

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action c. FACSIMILE TRANSCEIVER TROUBLE­ SHOOTING. Use an oscilloscope for Facsimile equipment in use by the Navy consists further signal tracing mostly of Facsimile Transceive r TT-41B/TXC- 1B, as far as the grids of associated Rectifier Power Unit PP-860/TXC- 1 and the electronic relay terminal equipment, and some related models of each. tubes or transistors. This transceiver with its power supply is capable of Make voltage and re­ nonsimultaneous transmission and reception of graphic sistance measurements material . In reception, the copy is reproduced either at the sockets in this directly (by a stylus on Teledeltos or reproducing circuitry if desired paper) or photographically (positive or negative ). i. Teletype signal Check all circuitry and No additional equipment is needed for short- haul present at grids connections between the wire transmission of the amplitude-modulated 1800-Hz of comparator electronic relay tube facsimile output signal . Conventional AM communica­ electronic relay plates and the TTYP tion equipment can be used for its transmission by A4 tubes but not at output filter in the cable­ emissions, but this method is subject to deterioration comparator filter assembly. Com­ of reproduction with signal fading. Conventional tele­ TTYP output pare the filter 's meas­ type transmission terminal equipment, with the addi­ ured and specified ohmic tion of Keyer Adapter KY -44( )/FX and Frequency Shift resistance; test- sub­ Converter CV- 172/U, permits frequency-shift trans­ stitute a new filter for mission (F4) of facsimile signals. Subcarrier the original if it is sus­ frequency-shift (SCFS, A4 emission) transmission pected to be defective. requires the use of Modulator, Radio MD-168/UX Note that plate voltage before the phone modulator of an A3 transmitter. The for the relay tubes is receiving equipment is the same as for F4 transmission, supplied by the exter- except that the BFO is not used and hence imposes no nal teletype loop. stability problem . Unit operation cannot No troubleshooting data on the terminal equipment be tested in use unless associated with the facsimile transceiver is given, be­ the positive side of the cause of the variety and few applications of such equip­ loop supply is applied ment. The following troubleshooting procedure is for to terminal A of the Facsimile Transceiver TT-41B/TXB- 1B; the steps TTYP OUTPUT con­ given are for identifying specific malfunctions, the nector. The negative corrective measures are obvious in most cases. More side of the supply will detailed maintenance information is available in techni­ then be to the converter­ cal manual for Facsimile Transceiver TT-41B/TXC- comparator ground 1B. Additional maintenance information can be found through the teletype in the Maintenance Standards Books, or Maintenance equipment plugged into Requirements Cards. the local loop Step Indication Action j. Keyed audio sig­ Test the oscillator­ nal not present at amplifier, phase­ a. Equipment Check switch settings. PHONES and splitter, and tone­ entirely Verify that power plug TONE OUTPUT modulator tubes; return inoperative and cord are in good jacks acceptable tubes to their condition. Inspect main original sockets. Re­ power fuses (5amp.) place defective tube s. b. Motor fails Inspect motor fuse. Test Use an oscilloscope to turn, but in­ motor output amplifier with sweep set to a dicator lamps tubes V5 and V6. Inspect submultiple of the AF light when e­ and test motor for bind­ for troubleshooting quipment is ing bearings, loose audio section malfunc­ switched on bearings, or rotor tions . Apply the probe striking field lamina­ to successive grids in tions. Inspect mechan­ an order progression ism for binding. Test following the first os­ motor windings for open cillator-amplifier circuits. Measure B­ plate. Check and cor­ plus voltage. Verify that rect the reason for any phase magnet and switch unexpected signal loss. (used in starting motor) Test connector con­ are operating correctly tinuity and winding continuity of the TONE c. Motor fails to Verify that regulated OUT PUT transformer sync and copy B-plus has the correct in the cable filter is skewed value. assembly. Test-operate the equip­ ment with the receiver

ORIGINAL J-71 ... - ... - ... -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action set to WWV trans­ input to where it is missions if WWV has lost, using a VTVM for been selected as the indication if only the standard. Otherwise, presence or amplitude set to the transmission of the signal is to be selected as the frequency determined. Possible standard. Follow the causes are .low input instructions given for and poor condition determining and adjust­ i. Recorded mate­ Measure fork oscillator ing motor speed in the rial is uniformly frequency. Perform technical manual for skewed Step c Facsimile Transceiver TT- 41B/TXC- 1B j. Recorded mate­ Remove receiver an­ rial has line tenna and shunt terminal d. Exciter lamp Check lamp continuity content (may be with 300-ohm resistor. not lit, low or (if out entirely). Inspect wavy) Local system pickup is flickering the lamp socket for responsible if lines are defects. still present. Verify that Check interchassis shielded cable is used Jones-plug connections. for all connecting links Determine if power unit and that all are in good if operating correctly. condition. Shunt grids Test tubes V17, V20, or terminals with a and T 15 in particular 0. 01-J.LFca pacitor in e. No signal out­ Check condition of excit­ systematic progression put, but indi­ er lamp and phototube until line signal dis­ cator lamps by testing or substitution. appears from head-set and motor Test RECORD switch for or oscilloscope used for operate continuity and sample the monitoring. Determine normally signal at that point . If condition of components the previous steps are in area those identified ineffective, test all as possible causes of transceiver tubes, re­ the malfunction; use tube turning the satisfactory socket voltage and re­ ones to their original sistance measurements sockets if necessary .

f. Low signal Perform all preceding k. Random dark Check regulated power output in steps. Test for imped­ and 1 ight streak s supply output. Check TRANSMIT ance mismatch by re­ in recorded copy condition of recording position moving load and measur­ lamp if photorecording. ing signal on AC scale Determine condition of VTVM . Signal should of lead screws be reduced to about half l. Hecorded copy Adjust contrast . when load of proper im­ characterized Verify that both trans­ pedance is connected by tone rever­ mitted and recorded g . Low contrast Check exciter lamp and sal and fuzzi­ copies are wrapped in transmission socket for condition. ness tightly around drums. and reproduc­ Clean optical system . Check optical systems tion material Test-substitute a new of transmitting and phototube to determine recording equipments condition of old one for cleanliness and focus; clean and focus h. Low-level Verify that input signal if necessary RECORD is at a satisfactory !eve l. indication Perform preceding Step m. Defective con­ Verify that contrast is e. Compare material trast in record­ set correctly. recorded by the direct ed copy Verify that neither "stylus " method with paper nor developer is that photorecorded. If from expired, outdated both are defective, the stock. malfunction lies in cir­ Verify that the developer cuitry used for both is not too cold functions. In this case, n. Recorded copy Repeat preceding Step m. trace the signal (a fixed­ too light In addition, verify that level, fixed-frequency the recording lamp and FM input ) from the

ORIGINAL 1-72 ...... - .. - .. - .. -

COM MUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Step Indication Action Step Indication Action

socket are in good con­ a LOC. CUR. loop selec­ dition if photorecording tor switch. Measure the is used. voltage across the meter calibration resistor. Now d. TELETYPE PANE L. measure the voltage Teletype equipment is usually connected to a across the meter transfer and metering panel, rather than directly to Full voltage Meter is open; replace its associated terminal equipment. This permits measured it the greatest possible versatility in equipment usage across meter� and also facilitates substitution in the event of equip­ none across ment failure. calibration Teletype Panel TT-23/SG is commonly used in resistor. small and shipboard installations to provide for patching up to 12 teletype and test equipments to as Full voltage Check meter to find if it many as 6 terminal equipments. It al so permits con­ measured is short-circuited; if so trol and metering of the current in each of the six ac ross cali­ replace it loops. This equipment is relatively troublefree, but bration resistor, an outline of troubleshooting procedures is given none across following in the event difficulty is encountered. Al­ meter though intended for Teletype Panel TT-23/SG, it is e. One loop inop­ Perform preceding Step applicable to others as well. erative when b for malfunctioning switched to loop. Step Indication Action LOC . CUR. Determine condition of a. No LOC . CUR. ­ Use voltmeter to de­ supply (checked current-limiting resistor powered loops termine if loop power with all plugs (R 104) for malfunctioning operate or have is present at the panel removed from loop. current indica­ at all . loop) Determine condition of tion. meter shunt resistor (R 102) for malfunctioning No loop power Check output of and con­ loop present at panel. nections to the associated power supply; follow the f. One loop fails Remove all plugs from procedures given in Sub­ to operate or give loop jacks. If loop is section 1- 7, Power indication of cur­ still inoperative, check Supplies, if power is rent now. continuity through ter·­ absent. minal and teletype equip­ ment wired into loop Loop power Test continuity of panel present power wiring from pow­ Loop is operative Plug one equipment at a er input to terminals of with all plugs time into looping jacks of LOC . CUR. /EXT .CUR. removed. of malfunctioning loop switches until operation fails and no cur rent is indicated. b. Loop power Open panel and inspect Identify plug which stops present but all connections and the when inserted. all loops are condition and operation inoperative of the loop selector Open-circuited Verify that equipment or and indicate switch. Repair any de­ equipment or plug is defective by sub­ an incorrect fective or questionable plug indentified. stituting it for a similar, current or connections found and operative equipment. no current clean, adjust, or replace Open-circuited Inspect condition of plug, the switch if necessary condition iden­ leads, and connections; c. Loop power Measure the resistance tified and ve ri­ repair or replace any present, but of the meter calibration fied. found defective. Test meter indica­ resistor and replace it teletype equipment for tion incorrect if incorrect (900 ohms open circuit and correct or absent for :t1 '7o for Teletype Pane 1 it if found. all loops, TT- 23/SG) Suspected equip­ Inspect malfunctioning whether or ment and plug jack for poor connections, not operative; operate when dirty or pitted contact Step b has inserted in an­ surfaces, and incorrect been performed other loop mechanical action d. Loop power pre­ Adjust LINE CURRENT sent and loops control for correct volt­ operating, but age (0. 6VDC for 60-ma no current indi­ loops ) across the 10-ohm cated for any loop meter shunt resistor of

ORIGINAL 1-73 .. - .. - .. -

COMMUNICATIONS 0967-LP-000-001 0 GENERA L NAVSEA

Step Indication Action Figure 1-27 shows an antenna system with the One loop fails to Inspect condit ion and parts drawn stretched out in a line. Figure 1-28 operate or give operation of SET jack . shows a standing wave of current of an antenna system. indication of cur­ Clean contact surface, The shape of the loops is supposed to be sinusoidal, rent flow when a resolder poor connec­ but these curves will suffice for discussion purposes. plug (dummy or tion, and adjust spring Length in the horizontal direction means "distance connected to members as required along a wire. " Height in the vertal direction means equipment ) is in­ for correct operation. "quantity of current in the wire . " The curves show serted in loop Leads from loop should the amount of current at any point in the wire . The SET jack be disconnected from current in a standing wave is not the same all along wired-in teletype equip­ the wire, but varies as shown in Figure 1-28. There ment (3-series and 4- are several ways to draw a standing wave , but the series terminals ) and one shown is one of the best because it shows all cur­ shorted when plug is rent as positive, or above the zero line, which is the inserted in SET pck. only way a thermocouple- ammeter can indicate it. Inserted pl ug should In practice, the standing wave is not as smooth as then make connection shown, but is partly irregular due to changes in surge with the teletype equip­ impedance along the length of the antenna system . ment wired to the 3- series and 4- series pair of terminals

1-11 ANTENNAS AND ANTENNA SYSTEMS For radio communication, the antenna is the key element in the system. A transmitter may have high power output, but it is the antenna that must radiate the power. A receiver may have high sensi­ tivity, but it must sense the minute currents in the antenna. If the antenna is lossy, communications cannot help but suffer. For example, an antenna that is short with respect to wavelength may exhibit a radiation resistance (t he virtual resistance into which an antenna is presumed to deliver its radiated Figure 1-27. An Antenna System energy) as low as 15 ohms. If the loss resistance is also 15 ohms, then half the power in the antenna system is dissipated in lossy elements. The deceptively simple appearance of antennas tuners, couplers, and antenna patch systems may lead to neglect of maintenance. True, there are no tubes or transistors or power suppl ies in an antenna But try to think of the antenna, its tuner, and its ground return path as a high-Q circuit in which R F currents circulate. Shipboard antennas operate in a hostile environ­ ment replete with salt water and stack gasses con­ Figure 1-28. A Standing Wave of Current taining acids, sulfur, and soot. If nothing else, antennas need environmental protection. Consider a standing wave fo r a frequency of two megacycles. Its half-wavelength is computed by a. WHAT DOES ANT ENNA CUHRENT MEAN< clividing the frequency in megacycles into 492 feet. "Meter inoperative, evidently burnt out. 0-5 fhe answer in this example is 246 feet which means ampere range seems too low. We find it difficult to that there will be 246 feet between thE nulls or zero­ keep antenna current this low on most fre quencies points of the standing wave (see Figure 1-29). This USS . " This report is made frequently. distance between nulls is called a half- wavelength. Here is another typical report. " ...by changing the Notice that all points separated by a half- wavelength length of the antenna, the current was raised from have the same amount of current in them . 1 ampere to 2 ampers, thereby increasing our field strength .... " This statement is incorrect. The operator merely moved the standing wave relative to the ammeter to bring a high-current part of the stand­ ing wave onto the ammeter. The field strength did not necessarily change, and the operator had to record new adjustment settings for his loading circuit due to the altered imput impedance of the antenna. It is be­ 1-----z.%------1 lieved that the following short discussion will prove helpful to the understanding of the distribution of current in an antenna system.

Figure 1-29. A Half- Wave at Two Megahertz

ORIGINAL 1-74 . I • . . . ,- ,- ,-

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

Meter reads ZERO (Halt-wave­ length antenna )

Meter reads LOW (Antenna very short compared to wavelength In UBe) -f§)

Meter reads ZlllRO (Antenna equal to wavelength or any whole num­ ber ot halt-wavelengths)

Meter reads VERY HIGH, and may btirB out. (Antenna length Ia an odd number ot quarter-wue­ lengtha) � ,______,

Meter reads several amperes (An­ tenna length 1s not any of the above cases)

Figure 1-30. Ammeter Readings for Various Combinations of Antennas and Frequencies

Figure 1-30 shows how much current the am­ built for the purpose, with whicL an oscilloscope or meter will indicate for various combinations of an­ headphone indication is used .) tenna length and standing wave. The antenna' s length 2. If the ammeter indicates a readable current , is fixed aboard ship, but the standing wave ' s length then it can be used as a carrier indicator because the varies with the frequency as described above . Each current reading will drop if the carrie r fails. However, example has a note beside it giving an estimate of the this function is not important as the final plate am� current. The antennas are drawn spread out like the meter and other meters will indicate the same thing. one in Figure 1-27. Actually each antenna can be of Another excellent carrier indicator consists of a any length, and each standing wave can be of any ft"e­ neon bulb loosely coupled to the antenna. This also quency, provided the standing wave and antenna fit makes a satisfactory modulation checker. each other as shown in Figure 1-30. 3. If the ammeter current is readable and if The conditions shown in Figure 1-30 will occur the antenna (or dummy antenna) input resistance is when the ammeter is connected between the antenna known, then the power output of the antenna may be and the loading reactors of the transmitter- wh ich is computed. In general, the technician does not know usually the connection used. In a very few cases, the the antenna resistance. transmitter utilizes a different connection, with the 4. If the ammeter current is readable it can be ammeter in the loading circuit, and then the readings used as a guide for further tuning of any stage in the depend on the tuning as well as the antenna lengths . transmitter. However, the transmitter is usually The most useful services that the ammeter can equipped with ot her meters for tuning the transmitter perform are: correctly. 1. On frequencies for which the antenna current 5. The antenna ammeter is useful for the indi­ happens to be large enough at the location of the am­ cation of accidential changes in the transmitter output meter to indicate some current, one can be sure that or in the antenna impedance (due to grounds, etc. ) modulation is occurring by watching the am meter move provided that the correct reading for the fr equency in during speech or mew transmissions . The meter use. is recorded and checked frequently. This action usually moves slowly and reads only 22. 5 percent is also equally well accomplished by observing the extra current during 100 percent modulation. (A final plate ammeter. superior modulation indicator would be a monitor

ORIGINAL 1-75 .. - .. - ..- .. -

COM:VlUNICA TIONS NAVSEA 0967-LP-000-0010 GENERAL

6. The antenna ammeter is often useful when 4. \'i/hile the junction box is open and the static reducing the output power, since reducing the antenna drain resistor is out of the circuit, the coaxial line current to half its normal value will reduce the radi­ from the antenna patch panel should be checked for ated power to one quarter its normal value. grounds and continuity from the radio central end of It should now be evident that the antenna cur­ the cable. A reading in the high megohm range will rent meter is useful, but not a necessity, and that show if the antenna and the center conductor of the in a given ins tallation it can indicate any current from coaxial cable are free from ground , but does not zero to off- scale, the value depending on the frequency prove that junction boxes, connectors, and cables as well as on the amount of power fed to the antenna. have continuity through them. Next ground the antenna What to do when the frequency in use is such near its base and check with an ohmmeter for continu­ that the antenna ammeter indicate s zero: NOTHING I I ity to ground from the center conductor of that parti­ Proper use of the final plate ammeter will indicate cular antenna outlet on the receiver antenna patch thai power is being fed to the antenna . panel in radio central, or wherever the antenna ap­ What to do when the antenna ammeter is being pears inside the ship. The reading should not be driven off scale: Try to take action, because the more than 1 or 2 ohms Then remove the short, and meter may burn out and prevent transmissions until again megger for short to ground. If a high reading a repair is effected. You may reduce the transmit• is not obtained it is possible that the coaxial cable ter po wer by decreasing the power fe d to the will have to be replaced. transmitter. 5. Filter board receiver antenna patch panels should be tested in accordance with the instruction b RECEIVING ANTENNA S ABOARD SHIP book for proper operation of the filters. On a more The best receiver on board cannot contribute frequent basis the isolation resistors for the antenna to effective communication if its antenna is ineffec­ outputs should be checked with an ohmmeter. It is tive . Antennas operate better at some fr·equencies common for these resistors to be completely burned and in some directions than other s, depending upon its out because of induced RF currents from nearby trans­ its length and its position relative to adjacent metal mitting antennas. Remember that R-390 receivers bulkheads, masts, rigging, and weapons. An antenna place a short across their antenna input when the may operate fine while the ship is on one course, but receive r is placed either in standby or calibrated its effectiveness may drop to practically nothing when mode; this short will affect all other receivers on the ship changes course. A proficient operator will an SRA- 12 type receiver antenna patch panel . check constantly to see if he is getting the best recep­ 6. Disconnect the antenna plug from the receiver tion by changing antennas when the CARRIER J.EV EL and check the coaxial line from the receiver antenna or the INPUT meter has decreased from its normal patch panel to determine that the coaxial cable has position. high resistance between inner and outer conductors. One thing that can be done to properly maintain Check for continuity by shorting one end of the coax the antenna system is to keep the antennas and ac ­ and checking with an ohmmeter for a very low resis­ cessories clean and the connections tight. Shipboard tance less than 1 ohm. Inspect the antenna jack on the antennas, due to ordnance and other considerations , r· eceiver for tightness and then reconnect the antenna are not the best antennas for reception, but we can into the receiver. do our utmost to keep what we have in good operable Granted that this is a lot of work , but it will condition. Following are a fe w sugge stions for HM eliminate hours of fighting to receive some frequencies and ET rates to keep the antenna system in tip-top that should be loud and clear. Normally junction boxes, condition: coaxial cables, and hardware need inspection only once 1. Consider the antenna system as consisting every six months. Insulators should be cleaned once of everything from the outboard or top insulator to a week or even more often. the antenna input of the receiver. This includes all The same procedure appl ies to transmitting insuiators, junction boxe s, static drain resistors. antennas when checking the insulators and hardware . coaxial cables, all connections, patch cords to in­ On high frequency type antennas, insulator cleaning dividual receivers, and the antenna jack on the re­ and maintenance is quite simple . A complete check ceiver. From the radio wave point of view, all this on UHF antennas requires that watertight connections is only one-half the antenna; the other half is the high on the mast be opened, a procedure more likely ground plane and ground return path. to be harmful than beneficial. Such checks should be 2. Insulator cleaning and maintenance is a made only during major overhaul, and thereafter must. The time betweE'n cleaning the lower insula­ r·elying on VSWR readings taken on three frequencies tors is dependent upon the type of ship, the tempo in the range of the equipment tied to a particular an­ of operations, and the area of operation. tenna The three frequencies should be as close as 3. Junction boxes may hold a resistor used to possible to the top frequency, the middle frequency, drain static electricity from the antenna. The boxes and the lowest frequency. If degradation of VSWR should be opened and inspected at least every six indicates antenna trouble, then it may be necessary months. The resistor should be measured and in­ to open the antenna connections for troubleshooting spected to ascertain if it is the proper size and in purposes. good condition. Connections within the box should be When transmitting antennas are being meggered, critically inspected to make sure they are in good remember that dry salt is an insulator, and the salt shape and well protected. The gasket on the box deposit will not become conductive until it becomes should be inspected and replaced if necessary , then damp. For this reason the antenna should be meg­ the box well sealed and all bolts or screws installed gered early in the morning while the morning de:w is and tightened down to prevent water or salt spray still present . from E'ntering the junction box.

ORIGINAL 1 -76 ...... - .. - ..-

COMMUNI CATIONS NAVSEA 0967-LP-000-0010 GENERAL

During operations at sea, the salt deposit on into the socket in the adaptor base is especially sus­ insulators continues to build up, and it is not always ceptible to the action of water and stack gasses if it po ssible to close down transmitters long enough to is not protected. It is not uncommon to find instal­ effectively clean insulators. Advantage can be taken lations where the large gland that tightens the con­ of the principle that the salt deposit becomes more nection can be turned down half an inch or more with conductive as its thickness increases. The second the fingers. princ iple is that sea water is a relatively poor con­ In the past year MOTU- 13 has found approxi­ ductor, especially when it is in a thin film. Based mately 20 whip antennas that could be lifted from on these principles, an alternative procedure of sockets by one man without loosening the gland nuts. shutting down transmitters and using a fire hose as Another six were found that measured 50 to 2000 ohms a salt water was hdown can be effectively used to re­ with an AN/ PSM -4 between the lead-in from the tuner duce the salt depos its on antennas and insulators. and the first section of the whip. In one case, a DC The preceding preventive maintenance proc ed­ re sistance of 300 ohms was located between the top ures are included in the shipboard Planned Mainten­ of the insulator assembly and the adaptor base con­ ance System (PMS). Continued performance of PMS taining the socket for the whip. These sections are will measurably reduce the problems stated in this held together by four large bolts, which should be of article. (EIB 723, 738) corrosion-resistant steel (C RES) to minimize elec­ troys is. Still another case showed 1500 ohms from the input lead- in to the first section of the whip. c. WHIP ANTENNA MAINTENANCE Due to inaccessibility, it is generally impos­ sible to check any but the first section of a whip Whip antennas, particularly the NT -66053, antenna without removing the whip. Vigorously NT -66046 and NT -66047, are the most overlooked shaking the whip will reveal any loose sections. If items of shipboard communication system ma inten­ loose sections are located, it is considered sufficient ance. With the exception of cleaning insulators and justification to remove and disassemble the whip for correcting obvious faults (i . e. , antenna breaking cleaning. If there are complaints of erratic tuning, off), antenna maintenance is often completely ignored. high tuner I coupler failure (many AN/SRA- 22 failures Because of the frequency of problems relating to are related ), or varying VSWR . the whip should be faulty antennas, it is a practice of MOTU units to disas sembled and cleaned even though no faults are check whip antennas when answering calls for assist­ apparent. This approach has proved quite successful. ance on antenna tuners, couplers, RFI, or antenna The replacement and/ or repair of ground straps at loading problems. Many tuner and RFI problems this time has also proved very beneficial . have been corrected by cleaning or repairing the In addition to the maintenance requirements antenna. provided in Shipboard Antenna Details, The General Maintenance EIMB (NA VSHIPS it is recommended that all whip antennas be removed, 0967- 000- 0160), Shipboard Antenna Details (NAY­ disassembled, and properly cleaned at least every SHIPS 09 67-117-3020) and PMS cards specify quart­ erly and monthly chec ks on all antenna systems . It six months , with replacement and/or repair of ground straps. Proper antenna maintenance with particular is quite obvious that scheduled maintenance is not attention to the requirements for antenna tuner/ coupler the practice on the majority of ships that have re­ grounding, as provided in the following equipment quested MOTU assistance. The princ ipal problems technical manuals, will minimize failures, CASREPTS, encountered with whip antennas are: and reports of erratic tuning: 1. Dirty insulators 2. Moisture and corrosion problems AN/SRA-22 NAVSHIPS 0967- 136- 6010 3. Defective or missing grounds on an tenna tuners and safety cages. AN/URS-38 NAVSHIPS 0967-204- 00 10 4. Bad RF connections between the tuner and the antenna, and between antenna sect ions . CU-937/UR NAVSHIPS 0967- 971-0010

Checking the antenna with a megger will show (EIB 785) up dirty insulators and moisture problems, but will give no indication of bad RF connections . It appears 1-12 NAVIGATIONA L AIDS that as soon ·as a gap forms between any mechanical connection, oxidation and sulfation of the metal sur­ a. RADI O-DIRECTION-FINDER EQUIPMENT face takes pl ace. This forms a semi.conductor bar­ Radio-direction-finder equipm ent indicates the rier which, when antenna R F currents now through direction of a received wave. Special construction of it , is capable of causing broadband EMI. In many its antennas permits accurate determinations of the cases the junction is so bad that it may be measured true bearing of the received wave . This bearing is with an AN/PSM -4 as a DC resistance. This effect the direction of the transmitting station. is further aggravated by the action of salt water and A radio -direction-finder system consists of a stack gasses on aluminum antenna parts to form other directional -receiving antenna, a sensitive radio corrosion products (alum inum chloride and aluminum receiver, and an indicating device. Often the oxide ). The bottom (lower) section of the whip fitting direction-finder indicator is a cathode-ray tube

1-77 / ORIGINAL .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

encircled by a plate etched with 0 to 360 degrees of compass markings. Direction indicated is the result of rotation of the loop antenna or loop-antenna gonio­ meter. A characteristic directional response will appear on the fa ce of the cathode-ray tube when the antenna or its goniometer is in position to indicate station direction. The receiver only serves to detect and to amplify the antenna response. /�IIIll I I 11 A -�cT1 •• b. THEORY OF RADIO-DIRECTION-FINDER 11: OF ANTENNAS INCIDENT VIAVE A fundamental law of electromagnetism is that when a conductor is cut by magnetic lines of force, a voltage is induced that is proportional to the rate that Figure 1-31. Currents Induced in a Loop Antenna the conductor is cut. This law also applies to the electric and magnetic field components of radio waves. density lines indicate the direction of the lines of flux. Electric and magnetic field components of a radio Figure 1-32 shows the relationship of the wave are inseparably related. Only the magnetic incident wave and the induced loop voltage. Note component need be considered to establish combined that the induced loop voltage differs in phase from electrical and magnetic characteristics. This rule the incident wave by 90". is true for the interaction between an incident wave Size or location may prevent the rotation of a and a receiving antenna. In this case, the magnetic loop antenna. A goniometer combined with a pair of component indicates the total interaction present stationary loops at right angles produces the equiva­ between the wave and antenna. lent of a rota ling loop. A normal or vertically polarized wave will induce voltage only in a vertical section of a con­ (2) Troubleshooting ductor. A vertically polarized radio wave has a Locating faults in a radio-direction-finding horizontal magnetic field. A vertical wire or set should be systematic. First determine the faulty "monopole ", the simplest form of a vertically polar­ unit. If it is the receiver, determine whether the ized antenna, may be a part of the radio-direction­ trouble is common to all frequency bands. If it is finder system. Its operation provides basic informa ­ one band only, the trouble probably is in the radio tion for an understanding of direction-finder loop frequency or oscillator unit. (Intermediate frequency, antennas. When a verti cally polarized radio wave audio frequency, and indicator circuits are in use on pa sses over a monopole antenna, the antenna will be all bands. ) The main tuning capacitor and its vacuum cut by the horizontal lines of flux in the wave. The tube and associated circuit components, the power height of the antenna and the intensity of the alternat­ supply, and control circuits may all be eliminated ing flux determine the induced voltage. The induced since they are common to all bands. Trouble may voltage is in pha se with the alternating flux waves . be an element selected by the switching operation or If the flux-wave intensity is constant, a change in the actual switching device. Therefore, the coil its azimuth direction will make no change in the assemblies and waveband switch should receive atten­ values of the induced wave. tion. Resistance tests of the radio-frequency amplifier and oscillator circuits will determine which one is at fault. If, in the defective circuit, the indicated re­ ( 1) The Response of a Loop Antenna sistance value changes with a slight movement of the When the horizontal lines of flux of an band switch, a faulty contact may be indicated. If incident wave cut the two vertical members of a loop the abnormal resistance value remains constant, the antenna, instantaneous voltages are produced at the fault probably is in the coil assembly or wiring. two vertical members. These voltages go in the Examine the switch contacts and the wiring of the same direction in Figure 1-31, the vertical members stage involved. If they appear to be in good operating of the loop antenna are represented by lines A and B. condition, investigate the coil assembly. The arrows adjacent to A and B indicate the vertical direction of the simultaneously induced voltages. (3) A Rough Guide to Circuit Location of While they follow their vertical path, opposing currents Faults circulate horizontally around the loop. These currents The amount and nature of background noise completely neutralize one another when voltages in­ in the loudspeaker is a rough guide to the location of duced at the vertical members are equal. the fault. Absence of any sound probably would be due The magnetic field of an incident wave has lines to pow er failure or to trouble in the output stage or of flux of various densities. They arrive at the two output circuits. Normal microphonic sounds, without vertical members of the loop antenna in a sinusoidal hiss, probably indicate a normal audio amplifier pattern. Figure l-32A illustrates this pattern. The system, but a faulty radio-frequency system. Weak lengths of the flux-density lines represent the relative signals accompanied by background noise may indicate amounts of density. The arrow heads on the flux- some fault in the antenna system or transmission lines.

ORIGINAL 1-78 ...... · , . . . ·,-. ,- ,- ,-

COMMUNICATIONS GENERAL NAVSEA 0967-LP- 000- 001 0

DIRECTION OF 'lli1VE ARR IVAL

( Al

I I . l

PHASE ' o' so' 180 270' 360' t TOP VIEW OF LOOP AT VARIOUS PHASES OF THE INCIOE NT WAVE

--PHASE 1 ( B l u..l ::>-' :;:: Q... 0 0 -' ....= <-> ::> = � j

o' 90' 160 ° 270' 360' ONE CYCLE OF THE INf·UCED LOOP VOLTAGE

Figure 1-32. Indiction of Alternating Voltage in a Loop Antenna Showing 90-Degree Phase Diffe rence with the In­ cident Wave

The indicator is an excellent guide in trouble Bearing error can be caused by refraction of the location. If automatic bearings remain fixed at o• received wave. Terrain and atmosphere between the and 180• or 90• and 270•, regardless of the direction transmitter and receiver cause the wave to change of arrival, trouble in one of the directional channels direction. Bearing errors are caused also by sky­ and its associated cables and goniometer is indicated. wave reflection and by radiation from other antennas. Where a cathode-ray screen indicator is used, mag­ Two signals near the sa me frequency and input level netized -iron parts in the automatic bearing indica tor will cause the indicator to shift between them. It will show up as offsetting points of the usually sym­ probably will be impossible to get an accurate reading metric propeller pattern. on either of them.

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COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

Shipboard transmitter radiation may cause the mission line and the other to its connector shell. indicator to hunt. Deenergizing the transmitter will Measure the insulation. (It should be at least 100 eliminate interference temporarily. Then it will be megohms. ) necessary to move the d-f antenna or the transmitter 2. Perform an insulation test on any re­ antenna to a location where transmitter radiation does maining antenna cabling by measuring between the not cause unstable indications. cable conductor and ground. When a reading of 100 megohms or greater is not present, check for strands c. GENERAL MA INTENANCE OF RADIO­ of shielding between the conductor and connector shell DIRECTION -FINDER EQUIPMENTS and damaged cable insulation. Pilot and Dial Lamp Failure When a shorted or open circuit in the goniometer When all pilot and dial lamps are out, the pro­ is suspected, make an ohmmeter check of its circuitry. bable source of trouble is the AC power supply or the Refer to its circuit diagram to do this. With the mul­ filament circuit. timeter, determine that the stators and rotors are not If the AC supply is at fault, the probable cause shorted together or shorted to ground. A stator is the power switch, a fuse, power input or output continuity check will require disconnecting the loop cables (possibly at the plug), or the filament-supply and stator at one end of the stator. The ohmmeter circuit. leads will then be connected to the two disconnected No Signal, Weak Signal, or Incorrect Bearing wires. Resistance should be negligible, possibly Indication four or five ohms (the total resistance of the stator These trouble indications can usua lly be traced winding and loop). to one of the following: All Low DC Voltage Power supply failure. When all DC voltages are low, a weak rectifier Faulty antenna connection. tube, an open filter capacitor, or a low resistance to Weak or burned out vacuum tube. ground in the B+ circuit is the probable cause. All DC voltages are low . Shorted Trimmer or Tuning Capacitor Incorrect cable .coMection. Occasionally a drop of solder will fall on a trim­ Shorted trimmer or tuning capacitor. mer capacitor and cause a short between plates. Power Supply Failure Solder is pried loose gently with a small screwdriver When the trouble is in the power supply, the or other small implement. probable cause is a burned out or weak rectifier tube, faulty contact to rectifier tube pin or pins, break in CAUTION continuity of power-unit cable, or shorted filter or Take care not to scar or bend the plates bypass capacitor. in the process. Bent capacitor plates Faulty Antenna Connection cause shOrt circuiting. Straighten a bent Poor contact between input receptacles and plate with a thin, flat implement. Press mating plugs or adapters may break the continuity of against the bent plate only. Do not wedge the antenna circuit. Other things that may create anything between two plates. bad antenna connections are grounded or open junction­ box circuits, grounded or open goniometer circuits, When the plate is straightened, rotate the and grounded or open interconnecting cables. capacitor control. During a complete rotation, equal Continuity checks will indicate open or high­ spacing between plates should exist. resistant antenna circuits. With Multimeter AN/ Noisy or Intermittent Reception PSM-4 or equivalent, continuity may be measured Noisy or intermittent reception may be caused in the following manner: by the following: 1. Disconnect the transmission line at the Noise pickup in the antenna system. antenna. Corutect a clip lead between the discon­ Faulty cable connections. nected conductor and ship's ground. Defective control. 2. Disconnect the transmission line at the Defective switch. receiver and connect one lead of the multimeter to Poor contact between a vacuum tube and its center conductor. Connect the other lead to its socket. ship's ground. Defective vacuum tube. 3. With the multimeter on the R X 1 scale, Frayed or broken wiring. measure the continuity. It should be zero ohms. Poor contact between pilot or dial lamp and 4: With the multimeter on the R X 1 scale, socket. perform continuity checks on any remaining antenna Defective bypass coupling capacitor. circuitry. This will include RF switches and RF Loosely mounted shielding can. cabling through junction boxes. The readings should Tracing a Noise Source always be zero ohms. If any reading shows an open Gently shake unit components while the unit is circuit or is above zero, make a visual inspection of energized. Moving the loose ground lead, poor tube the faulty component for corroded or damaged switch and socket connection, or loose shielding can will contacts, insecure or damaged corutectors, etc. change the noise level . The following insulation test should be performed When you find one loose connection, look for on the antenna transmission line: others. Check all chassis connections for tightness. 1. Disconnect the clip lead at the antenna Press all vacuum tubes tightly in their sockets. end of the transmission line. Using Test Set AN/ Change control settings. If this increases oper­ PSM-2 or equivalent insulation test meter, connect ating noise levels, look for dirty electrical contacts in one of its leads to the center conductor of the trans-

ORIGINAL !-80 . . .

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COMMUNICATIONS NAVSEA 0967-LP-000-00l n GENERAL

the control circuits. Clean the dirty switch, relay, tension, or tightening the slip-ring retainer will or ot�er control contact with cleaning solvent Type remove the sawtooth pattern (Figure 1-33). 140F. d. SCHEDULED INSPECTIONS OF RADIO­ Tighten all cable connections. If this does not DIRECTION-FINDER EQUIPMENTS eliminate noise, look for changes in noise level when Inspections that follow pertain to all naviga­ cables are shaken. Replace broken cables and clean tional aid direction finders. They are not iron­ all dirty cable connectors with dry cleaning solvent bound rules; POMSEE and Test Methods and Practics Type 140F. are the guides for scheduled measurements. These If a noisy antenna circuit is suspected, short are general procedures for scheduled inspections circuit or disconnect the antenna at its input to the that can be performed to any DF equipment. More receiver. If the noise stops, the antenna circuit is details and more tests are necessary for specific the source. Antenna circuit tests are given under equipments. the preceding topic "No Signal, Weak Signal, or Monthly Inspections Incorrect Bearing Indication". Specific monthly inspections which can be An oscillosope will speed discovery of a noisy performed on all radio-direction-finder equipments coupling or bypass capacitor. With the antenna dis­ are as follows: connected, troubleshoot the receiver from the output 1. Antennas. The antennas should be inspected toward the input. Observe the waveform at each while in yards (or equivalent conditions of safety) for stage output. (Use a schematic and layout drawing. ) the following: Trace to the stage with a "clean" signal: where the Insulators : Inspect insulators for cracks, noise distortion does not appear on the trace. The breaks, and tightness. bad capacitor is in the stage previously checked or Elements: Check elements for alinement, between the two stages. Replace the coupling capaci­ vibration, and cracks in JOints . tors. If the noise is still there, replace the bypass Pedestals: Check pedestals for vibration, capacitors of the last noisy stage. loose mounting bolts, and poor electrical and Fading mechanical connections. Check the condition of the Fading is not always caused by circuit failure. pedestal cables. It sometimes results from a magnetic storm. When Frame: Inspect its alinement and check for a storm is not the cause, look for the following: vibration. Defective coupling or bypass capacitors. Paint: Inspect for rust spots, cracks, or Vacuum tubes with intermittent heater peeling. operation. 2. General. Inspect all rubber used for shock Low sensitivity. mounting, replacing where necessary because of Procedure for determining defective coupling cracking or loss of resilience. or bypass capacitors was given under the preceding 3. Receiver. Measure the receiver sensitivity topic "Noisy or Intermittent Reception". in accordance with current instructions. (Refer to Testing does not always detect a vacuum tube "Receiver Sensitivity Tests for Navigational Equip­ filament that opens intermittently. Interchanging ments" of this subsection) tubes may be necessary. The "Receiver Sensitivity Tests For Other Than WARNING Loran Navigational Equipments" section describes Receiver alinement should not be attempted sensitivity measurements. except by experienced maintenance per­ Indicator Pattern Satisfactory on Direction sonnel with a suitable calibrated signal Position, but no Pattern on Sense Position generator and vacuum-tube volmeter. (or Vice Versa). An open deflection or sense coil will cause this. 4. Direction-Finder Calibration. Check the The open coil can be determined by a continuity test. radio-direction-finder calibration curves on at least A faulty brush will cause it also. 5 points and at least 3 frequencies. Tune in trans­ Receiver Tunes Signal Satisfactory and Circle mitting stations on bearings which can be determined on Bearing Indicator is Satisfactory, but No accurately by visual or navigational means. Vary Bearings can be Obtained. check points and frequencies as may be practical in The probable cause of this source of trouble is subsequent monthly checks. either an open input cable or no receiver-indicator 5. Insulation Test. With an insulation test channel output. To repair the latter, check the volt­ set, test the insulation to ground from all antennas age output of the receiver indicator channel, and be and the insulation to ground from the control and sure that it is the same as specified in the instruction power-supply circuits. Observe that the megger manual for the particular equipment. If there is no reading is 100 megohms or more. MaJOr repairs, voltage at the output, check circuits against the appli­ electrical alinements, and most replacements of cable schematic diagrams. circuit components should not be attempted at sea, With an ohmmeter, test the continuity of the but rather at a yard equipped with laboratory equip­ input cables. Replace or repair the cables if ment. A tube substitution method of replacing a necessary. suspected faulty tube with a new one known to be in Sawtooth Pattern on Cathode-Ray Tube Circular good operating condition will often locate and correct Pattern the trouble. In the event that this method does not The probable cause of this sawtooth pattern is work, trouble must be located methodically through poor contact between slip rings and brushes. Clean­ elimination processes and analyses of circuit voltages ing and polishing of the slip rings, adjusting brush and resistances.

ORIGINAL 1-81 - - - ,- , , ,

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

35 35 00 01 00 01

08 28 08

27 09 09

26 10 10

19 18 17 19 18 17

Figure 1-33. Typical Indicator Patterns Due to Poor Brush and Slip-Ring Contact.

6. Slip Rings and Brushes. Check slip rings much of the tuning at sea and speed all tuning. for concentricity and looseness. Check brush pres­ Frequency-dial settings based on interpolations are sure. Check brush pigtails for fatigue, flexibility, permitted in pretuning where exact frequencies are corrosion, and contact. See Figure 1-34. not required. Oscillator frequencies, which are not Quarterly Inspections crystal controlled, are set by means of frequency 1. Antenna. Clean antenna entrance, strain, meters. and pedestal insulators, and tighten connections. Audio Frequency Inspect, clean, and tighten, as necessary, all acces­ For testing operations which require the repeat­ sible ground connections. Antenna insulators should ed measurement of audio-frequency pow er, commer­ be cleaned more often then quarterly when dirt de­ cial power meters are available. These instruments posits accumulate rapidly. are generally composed of a ratio transformer, a 2. Receiver. (a) Make sensitivity measure­ constant-resistance multiplier, and a voltmeter. The ments of the receiver in accordance with current ratio transformer is compensated by various resist­ POMSEE or Test Methods and Practices, and record ances which allow the effective load imposed on the results in log, prior to and after any corrective output stage to be varied over a number of steps. action, (b) Check the frequency calibration of the re­ The constant-resistance multiplier acts as a range ceiver. The calibration should be checked in the multiplier for the voltmeter while presenting a manner prescribed by the particular instruction constant resistance to the secondary of the trans­ manual or POMSEE that is assigned to the equipment, former. Indications are calibrated in watts with this and (c) Check the operation of the receiver r-f gain, type of instrument. audio gain, and sense-gain controls. The controls When phase angles are introduced by reactive do not require any adjustment or trimming . Controll­ components, power measurement by the previous ing toggle switches, potentiometers, and vacuum method is no longer applicable and wattmeters, which tubes are the usual causes of lack of or absence of are proportional to the power factor as well as the gain. Frequent troublemakers are those toggle apparent power, must be used. Even wattmeters are switches which are operated so seldom that the small not practical at high frequencies. Stray capacitances amount of oxide that forms on their contacts renders and inductances, skin effects, and other complica­ them inoperative. Periodic operation for ten to twenty tions increase as frequency rises. minutes will usually permit these switches to remain Power Meters in good condition. Potentiometers, however, usually When close accuracy is not essential compact become faulty from excessive use. When this occurs, test equipments called RF power meters are used to the faulty potentiometer must be replaced. furnish direct readings of RF power. A power meter (1) Transmitter Power Measurements is small and portable, even when designed to measure Because of radiation, transmitter tuning outputs as great as 500 watts. Power meters are presents problems, some of which may be eliminated suitable for direct measurements from 3 MHz to by tuning while the ship is at its ba se. Accurate 300 MHz. logging of dial setting during pretuning can eliminate

ORIGINAL 1-82 ...... ,- ,-

COMMUNICA TIONS NAVSEA 0967-LP-000- 0010 GENERAL

SANDING BLOCK �--��--�------�[J

CLEANING SOLVENT TYPE 140r . 2. 5 YARDS OF CHEESE CLOTH .

3. 6 SHEETS ARMOUR SANDPAPER WORKS CROCUS CLOTH OR EQUIVALENT. 4. I SPRING-TENSION GAUGE GRADUATED IN 1/2 OUNWi . 5 I BLOCK BAKELITE OR OTHER SMOOTH-SURFACED SUBSTANCE 2" X 3!4 " X 1/8".

6 3!8" X 5" BAKELITE ROD (OR NON- METALLIC ROD ).

Figu re 1-34. The Necessary Equipment for Servicing Slip Rings and Brushes.

Radio-Beacon Transmitters Navigational-aid transmitters are restricted Tune the receiver- coupler coil until the shor e­ to radio-beacon equipments and are relatively station signal is of maximum amplitude, making sure simple. A complete transmitter may include as that the signal on the scope is below saturation. little as a radio-frequency oscillator, a pulse modu­ While making this adjustment, note the antenna lator, a keyer, and a power supply. current. The antenna current will be somewhat Receiver Coupler Tuning in Radio-Beacon reduced when the receiver coupler is far off tune. Transmitters It may be necessary to slightly retune the trans­ mitter after tuning the receiver coupler. WARNING When the transmitter includes coil taps, set High voltage, dangeous to life, is present them according to the equipment instruction manuals . in transmitters. Before making any Other transmitter adjustments, which are peculiar internal adjustments, set the high and to the individual equipment being tested, will have to low voltage switches to OFF .

ORIGINAL 1-83 · ,

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COMMUNICATIONS NAVSEA 0967-LP-000- 001 0 GENERAL

be performed according to the appropriate equipment ary; its purpose is to eliminate regeneration and other instruction manual. undesirable effects. Connect an RF signal generator with an un­ (2) Receiver S ensitivi ty Tests for N avigati ona l modulated output to the antenna input of the receiver. Equi pments Beginning with the standard input voltage , inc rease Prepa ratory St e ps th e signa l generator voltage output in s te ps of about 1. Check the power supply and line -inpu t volt - ages. 1.4, 2, 3, :'>, 10, 100, and 1000 times its standard in­ put. At ea c h step, the fr. on each side of the ,· oltm e t er and the diode load (high with respect of th e center frequ ency . to ground). Possi bly the resistor w il l not b e neces s -

RIGINAL O 1-84 ...... - ...... - ...-

u..�MMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

amo unt of the noise pro ducing copper salts 1-13 SUPPLEMENTARY DATA and oxides (rectifiers ) remained between the strands and in the cen tral fibre core . Cover­ The function of this subsecti on ing the brushed wire with a combinat ion of is to record ma intenance and opera­ greases , wh ite lead , and other compounds de­ layed more corrosion, bu t it did not neutra­ tional info rma ti on of a general lize the remaining salts. Also, wire brushing nature that has been generated may break some strands of the wire and allow since the re vi sion of Se cti on 1. them to become noise sources from corona. Info r mation wi ll not be organized Ac tivities specifying an acid or "bright­ ener" dip for the wire rope realized that wire under subject categori es but wi ll brushing could not reach be tween the wire be subjoi ned to thi s section as strands and , there fore , a liquid cleaner would future changes ar e issued . give a cleaner and more uniform appearance . [n theory , one would expect to clean the maj or part of every strand except for the contact points to adj acent strands ; however, it is the salt at just these contact points which give a. Buoyant Ca ble Antennas-Preparation of Spa res the most trouble to rad io frequency currents . It is doubtful that the difference in gener­ ated noise products between the two cleaning Submarine s havi ng the inboard recoverable methods could be noticed . The acid or buoyant cable antenna installed usually "brightener" dip has a hidden and long term carry spare buoyant cable and spare termina­ problem which may not be eviden t unt il some tion tips, but no spare UG-1 820/U connector . future date when ship's personnel are inj ured The UG-1 820/U connects the buoyant cable by a falling wire . A SAFETY HAZARD existS antenna to the rotary coupler in the hub of after an acid bath or "brightener" dip due tg the re el. In the event of a casualty to the a residue remaining in the fibre core of the antenna the UG-1 820/U must be disassembled wire rope and cont inuing to etch the strands on to the spare cable before a new antenna until they break somewh ere along the length can be deployed . Thi s routine takes 1-1/2 (810) to 2 ho urs . of the an tenna. The time required to stream a replacement antenna after a casualty can be si gni fi cantly c. Wi re Rope Anten na s-Cleaning and Preservation; reduced if spare UG-1 820/U connectors are Cleaning Precautions carried on board as well as the usual cable and termination tip s. One or more antenna s can then be assemb led whi ch would be ready Wi th the increasing use of viny lite jack· for immediate use . The cable gui de on the eted wire rop e for ins tallation of wire an­ front of the reel should be modi fi ed as tennas , it is necessary that activities be shown in Figure 3-II-B1 4 of Handb ook for aware of this improved wire and the best tech­ Submarine ·Antenna Improvement Program, USL niques for maint aining its watertight in te- Report 551B, so that the UG-1 820/U can be 5rity , Th is article wi ll give the ge neral passed through it while attached to the approach and particulars for sealing out water antenna . at all connections . Re fer to the September The UG-1 820/U is available from stock 1970 edition of the Shipboard Antenna Sys tem under FSN 5935-247-0745 at $3 .00 each . (796) Details (Volume 2) NAVSHIPS 0967-177-3020 for the Mil Specs wh ich apply and the ordering procedure , Paragraph 2.2.1 refe rs to the 5/16 b. Wire Rope Antennas-I ncrea sed life Using Improved inch wire rope for transmitting (approve d Materi als source) , and paragraph 2.2.2 speci fies FSN This ar ticle out lines pro cedures which 6145-542-6519 for 1/8 inch wire rope with are NOT acceptable for cleaning wire rope an­ vinylite jacke t for receiving . tennas on surface ships . Methods and pro ce­ The installation of jacketed wi re ro pe dures wh ich may enhance appearance or are easy in conj unct ion wi th the sealing procedures in to apply , but re sult in eventual det erioration this ar ticle will eliminate monthly mainte­ of the wires , shall NOT be used. NAVSEC has nance , and quarterly PMS will be little more des ignated that vinylite jacketed wire rope is thar. a visual inspection fo r weathertightnes s to be us ed in new and repl acement in stalla­ and the normal meggering of insulators . tions ; therefore , cleaning of old unj acketed Ac tivities an ticipating ant enna overhaul wire rope is unnecessary . should , several months in advance , submi t a In the procedures used previous ly , only non-sto cknumbe red requisition to ESO for both the outside of the wire lay was in a pos ition �he vinylite jacketed wire and seve ral quart s to be wirebrushed and , conse quently , a large of Scotch Clad #1706 (gray or black) pr eserva-

OR IGINAL 1-85 i • I ...... ,- ,- ,- ,-

COMMUNI CATIONS NAVSEA 0967-LP-000-0010 GENERAL tive coating (6 months shelf life) , If the No bare metal should be exposed to the assorted conne cting hardware cu rrently in­ weather ; even jacketed wires used for safety stalled has· been un coated in the weathe-r; for links and downhauls mus t have a good coating a year or more , it may be more economi cal in at the ends to prevent water from wetting the manpower and effort to requisition new hard­ wire and "wicking" the length of the wire ware rather than to clean up the old. under the jacket, Figure 1 is a typical wire rope connec­ Scotch Clad 1706 is stronger than paint tion block whi ch was prepared using the pro­ and of such consistency that gaps can be cedures of paragraph 2,4 in Volume 2 of the bridged , as are found around all threaded Shipboard Antenna System Details and the im­ fasteners , and seizing, caused by salt intru­ proved materials of this article , Silicone sion , can be prevented at any connection grease, DC-5 (FSN 6850-963-5402) is substi­ whether it be antenna or no t. tuted for the Hard Film Gun Slushing Compound In re ference to the whip antenna preserv­ in paragraph 2,4,c, because of its availabil­ ing article in EIB 785 , no te that Scotch Clad ity in a tube and ease of application and re­ 1706 will probably make a stronger seal around moval, The arrows in figure 1 point to the the large mounting bolts wh ich were shown cov­ wh ite sil icone rubber, RTV- 731 (FSN 5330-842- ered with DC-1890 . Comments regarding this 6380) or RT V-102 (FSN 8040-225-4548) , which is procedure can be �e nt to the Naval Ship En­ forced into the gaps between the connector gineering Center, Norfolk Division , Code 6621 , plates after final assembly and tightenin g of Naval Station, No rfolk , Va, 23511. the bolts , If excess DC-5 is evident on the This procedure supplements the PMS now vinyl jacket at the point of ent ry to the con­ in the Fleet , The PMS will be updated to in­ nector , wipe clean with solvent dampened rag clude this procedure , (8 10) before forcing silicone rubber into the ad­ jacent cracks and around the wire to com­ pletely seal the connector . Allow the silicone rubber to harden over­ d. Mag n esyn Compa ss Transmitters in Submarines­ night , Now, preserve all watertight connec­ Adjustment of tors with at leas t two coats of Scotch Clad 1706 wh ile on the open deck, Read the label Normal adjus tments of magnesyn trans­ on the can fir st, Store in the paint locker mitters in submarines have long pres ented with other volat ile solvent compounds (6 problems due to the necessity for op ening the months shelf life) , Apply the Scotch Clad 1706 with a 1 or 1 1/2 inch paintbrush (throw away when through) so that the hardware and ,...---- PLATFORM 3 or 4 inches up the vinyl jacket are 100% covered , Apply a second coat at leas t 30 min­ utes later, as suring that all cracks at bolt PRESSURE FORWARD heads and washers are sealed as well as wire PROOF t entry points . DOME

r------l NEW I I NEW I I RTV RUBBER I I I TRANSMITTER I I

� :L ______� _j MAGNET MAGNET HOLDER HOLDER FOR E-W FOR E-W ADJUSTMENT ADJUSTMENT

MAGNET HOLDER FOR ._____ N-S ADJUSTMENT Figure 1. Connector Plates Sealed with White Silicone Rubber Figure 1. Method of Mounting Corrector Magnets

ORIGINAL 1-86 I' ...... - .. -

I NAVSEA 0967-LP-000-0010 COW,1UN CAT I OilS GEilE R/\L

pressure proof dome and the watert ighc en­ An tenn a DC Resistance Notes closure of the transmi tter. This is partic­ ularly difficult at sea an d also exposes th e equipment to damage by th e elements . AS-1688/SPS-4R IV) LOW- Approximately a direct To permit rough adj us tmen t of the short , as measured at· transmitter without opening th e equipment either the hyb rid or the enclosures , some activities have moun te d cor­ an tenna inputs . Hybrid can re ctor magnets outs ide the pressure proof be separated from the dome . This method ca� also be us ed for co r­ an tenna inputs, or may not rections beyond the range of the internal be used , in some ins tallations . correc tors . One such method , devised by th e Pearl AS- 2188(XN-l)/U HIGH-Over 20 megohms , meas­ Harb or Naval Shipyard, is shown in figure 1. AS -2188/U ured at either the sum or AS- 2189(XN- l) /U the difference input to the This method employs standard co rrector magne t AS-2189/U hyb ri d. Hybrid is tied holders and fasci cular cobalt corrector mag­ directly into the antenn a ne ts with the amount of correction de termined and cannot be separated. by the numb er of wires used in each holder. Material required: AS -2787/U LOW-Essentially a short Th ree corrector magne t holders (FSN circuit , as measured at the 1H66 05-369-4425) and one corrector magnet set antenna inputs. Hybrid can (FSN 1H6605-211-6746 ). !1? 15! be disconne cted from antenna .

CAUTION e. Dummy Plug forTe l etype Panel If there is an RF swi tch in the line , DO NOT use a megger , as it The common practice of us ing a pat ch will burn out the switch diodes . plug or one end of a pat ch cord to open Also , the DC res is tance measure­ loops or isolate equipment in a TTY patch ment will be in error. pane l is unsafe . Not only, does this practice present a dangero us shock hazard , but it do es not AS- 177 LOW- 50 ohms or less. See Note always provide proper isolation of equipment 1 or TTY loops . This uns afe practice can be avoi ded �ith th e us e of an anpropriate dummy AS-177A HIGH-Over 20 megohms . See Notes plug. AS- 177B 2 and 3. Th e dummy plug is avai lable in the supply sys tem under FSN 9N59 55-642-0743 at a cos t of .$ .17 each . In this cas e "Each " repres ents a package of 5 dummy pluP.s . (1?:20) NOTES :

1. Early versions of AS- 177A antennas moun t on 1" ext ra heavy pipe (1 . 315" OD) ; others f. IFF Antennas DC Resi stance-Inform ation concerning require l- l/2" extra heavy pipe (1.900" OD) . 2. AS- 177A mounts on 1-1/2 x 11-1/2 threads/inch extra heavy pipe . AS- 177B us es There appears to be a need to summarize the same size pipe but requi res no threading. DC re sistance characteristics of all ava ilable 3. AS- 177 TM NAVSHIPS 92642 , which became IFF antennas , as follows : NAVSHIPS 0967-958-0010 by cove r sheet , states Antenn a DC Res istance Notes "resistance of an tenna and cable should be neg­ AT- 352 /UPA HIGH-Over 20 me gohms ; ligible." Quite the opposite. T-2 to NAVSHIPS AT- 352A/UPA measured at an tenna input . 92642 (Aug '63) and T- 3 to NAVSHIPS 096 7- AT- 352B/UPA 0010 (Mar '67) correctly state "resistance shou .d be HIGH."

AS -1065/UPX LOW-Essentially a short ; less than 5 ohms . See EIB #767, 15 Dec 1969 , P. 13 and EIB #776 , 20 Ap r 1970, P. 12 .

ORIGINAL 1-87 . . ' . . .. . - ..- ..- ..- ..

GENERAL COMMUNICATIONS NAVSEA 0967-LP-000-0010

1li.lt(_nallce Hint : g. Degau ssing Rectifier--Power Supp ly r� "1 0 obtain th e maximum service life Ma intenance 'ron rectifier conponents , it is recommended �ha t the air filters on all uni ts be in­ The tollowi ng ma intenan ce article ap­ spected and cleaned in accordance with the cl ies to Typ e ��-]A Inte rna tiona l Telephone & Telegraph Corpora tion Aut oma tic Degaussing requirements of Ma in tenance Index pages EL- 20/10-30 EL-20/10-A2 , Equipments on DD� 2 Cl, DLG 6 Cl , DLGN 25 or as applicable. and 35 , CGN �. and LPD 1 Cl ships . Th ese documents require a quarterly cleaning Data Period , Type , Sou rce : of the filters . Th is recommenda tion , wh ile JanPary 1971 through August 1972. Ma­ bas ed upon condi tions and ma intenance data teri,,j Hi story Report , Ma intenance Support fro� degaussing power suppli es , is equally Office , 3ci/MDCS , Report No . 4790.S2704 .A-08 applicable to all other forced air cooled �a intenance actions for Interna tional static power supply equipments having air Telephone and Te legraph Corporation , Type filters . Re lated to this , ships force should G�l-lA automa tic degaussing equipment for ascertain tha t th e Equipment Guide List the period January 1971 through Augus t 1972 (EGL) , required for the EL20 - Quar terly have been .reviewed. This review was in­ Ha intenance Requirement Card , is comp leted to stigated as a result of excessive failures ensure that all applicable static power sup­ of the main power re ctifiers in the de­ plies are covered and rescheduled accordingly. gaussing M coil power supplies as noted ( /:"/ u 8 ') )) from CASREPTS . Discussion : An excessive number of failures of the ma in powe r rectifiers in the degaussing M h_ Unauthorized Topside Alterations coil powe r supplies have been no ted in recent months wi th prac tically no failures (This ar ticle is condensed from the of th e corr esponding rectifiers in th e FPQP NAVSHIPS TECH NEWS March 1973 issue) coil powe r supplies . Both units are of the Every ship requires dep endable com­ same ty pe, differing only in rating and in munications to perform as signed missions me th od of cooling . The M coi l unit is a effectively . A ship is useless as a com­ 25 kilowatt, blower cooled unit wh ile the bat system, a repair vessel, an aircraft FPQP uni t is rated at 5 kilowatts and is carrier , or a harbor tug if it loses its convection cooled . Both uni ts are loca ted ab ility to communicate . In recent years in the same general area in the ma chinery the volume of shipboard communications has spaces and should be expec ted to require increased dramatically . This rapid expan­ abnut the same degree of corrective ma in­ sion has led to thP �e"Pln�ment of increas­ �enance . An alysis of the data contained in ingly sophis ticateJ equipment wh ich places a �lai ntenance History Repor t for the period �ign demands on s� ;tern parameters . To handle January 1971 through Augus t 1972, however, th is increase in an organi zed and thorough shows tha t 90 ma in power rectifiers were manner , each class of active ships has under­ replaced in the M coil power supplies com­ gone , or is presently in the process of pared I.Jith only two replacements in the undergoing , ex tensive communica tions an­ FPQP coil uni ts . Based upon common con­ tenna system design. This design views the ditions found on a number of ships recently , ship 's topside as a total system, incorpb­ this disparity is attributed primarily to rating inputs from the MIP (Mi litary Im­ high temperatures inside the M coil power provement Plan ) and the F�W (Fleet Mo dern­ supply cabinet resul ting from the reduction ization Program) . The design also considers in the flow of cooling air through the all known future installations on or changes cabinet caused by clogging of the air filter to topside structures including weapon sys­ wi th an accumulation of dus t and lint par­ tems , radar sys tems , replenishment systems , ticles . Th e condi tion of the air filters or any sys tem -requiring topside space , and as found during inspection ind ica tes that arranges the an tenna system so tha t whenever :he air filters were not being inspected one of these future systems is ins talled the and cleaned as required by the Planned impact to the existing antenna sys tem is minimized . Ha intenance Sub-Sys tem. Becaus e of the high The communica tions antenna system is not :: emp_e ra tures the temperature sensitive an isolated , independent systen . It must be cectifiers experience increased internal tailored carefully to a particular ship type losses wh ich accelerates aging effects and so that it can operate effectively within results in prema ture failure , as ev idenced by the large number of replacement recti­ th e general cons traints of space , weight, high amb ient rf fields , and in direct comp e­ fiers required . tition with other users of the ship topside env i ronment . The entire ship, from the top

ORIGINAL 1-88 ...... - ... - ... - ... -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

of the mas t to the wa terline, is a complex For additional Lnforma tion about why sheet of interacting rf current streams com­ unauthorized topside erections may cause more prising the antenna system and has a direct problems than they solve , the readers are influence on individual communications an­ referred to the informative publ ication tenna system performance characteristics . "Shipboard An tenna Sys tems-Communications Antenna radiation pattern, feed point impe­ Antenna Fundamentals ," Volume No . 1, NAVSHIPS dance, and intercoupling data depend not 0967-177-3010, Sep tember 1972. (This docu­ only on frequency and the antenna loca tion, ment updates NAVSHIPS 900121(A) "Shipboard but also on the surrounding structures . The An tenna Details , Chap ter 1, Antenna Funda­ res tricted area available on ships for mentals" dated 1 June 1958) . rf:./H H551 placing ahtennas causes most of the communi­ cations antennas to be affected by the presence of adj acent radiators and parasitic structures . Examp les of topside modifica­ i. Broad-Band Interference Generation in Ship's tions which can seriously affect antenna per­ Tops ide Structures formance include adding deck houses ; mas t and yardarm configurations revised by Recent fleet reports have indicated ser­ Christmas lights , wires , rigging of mast ious HF commu nications prob lems due to self­ lights , etc. ; antenna additions , deletions , generated ship in terference . This interfer­ or relocations ; changes in communications ence is characterized by intermi ttent noise antenna couplers or filters ; and alterations bursts wh ich affect a large part of the HF to weapons or ECM and radar system location . frequency spectrum . Non-comb atant type ships Due to the magnitude of factors having with large amoun ts of running rigging used influence on an antenna, the quickest (at for underway replenishment purposes are par­ least for the LF, MF, HF and VHF frequency ticularly sus ceptible to this prob lem. ranges ), as we ll as the mos t cost effective , method of checking ou t an antenna is to meas­ The sources of this prob lem have been ure the electromagne tic parameters on a identified as various topside me tal lic ob­ suitably prepared model. There is often jects rubbing or touching each othe r inter­ considerable apprehension, by forces afloat, mittently wh ile ship transmitting antennas that a laboratory-controlled solution may not are energized. The cause of the problem is work in the real wo rld . However , years of the currents induced in these obj ec ts, as a experience have verified that data ga thered normal consequence of an t enna ra diation. by-model t esting will closely parallel actual The sudden changes in cur re nts produced by shipboard tes ting , provided topside struc­ the make and break contact between these tures have not been altered or added . items produces spikes of noise wh ich can be Modeled antenna-arrangement designs that have heard continuously across a wi de frequency been closely followed during ship cons truc­ range . The prob lem is espe cially bad wh ere tion or overhaul can be made ineffective by whip antennas , ope rat ing with inp uts of topside modification (such as unknowingly 1 KW, are located atop kingposts support ing erecting parasi tic struc tures or twe aking a UNREP ri gging. Th e kingpost becomes part of matching network ) performed by shipyards or the radiating system, thus inducing high operating forces who are unaware of the con­ vo ltages in span wires and outhauls . Ship 's sequences of their actions . Indeed , an in­ speed , humidity , relat ive wind ve locity and dividual sys tem might operate more efficiently temperature can have a strong influence on but the total ship 's antenna sys tem could be the generation of broadband noise. subs tantially degraded . There is no simple cure for this inter­ To ensure satisfactory performance from ference but a numb er of fixes can be employed , an an�enna placed in the bes t loca tion avail­ depending on the circumstances , wh ich wi ll ab le, the ins talling engineer must have a ei ther eliminate or minimi ze the prob lem. good understanding of the complex electro­ A ma jor considerat ion is the st owage of magnetic nature of interact ing , und esired rigging involv ed with UNREP and cargo handling coupling be tween the antenna and other top­ equipment . Such equipment shou ld be stowed in side objects . Each antenna is custom-fitted a manne r to minimi ze rubb ing , scraping , or to its environment and then be comes a vic tim bumping between me tallic components . Out­ of th at environment . Any attemp t to alter hauls , span 1-1 ires and other cab les should be che topside in a piecemea l manner wi thout pulled taut and tied off with nylon or hemp analyzing the effects on other systems would rope . be a reckless attemp t at solving a problem. The use of non-metallic hardware such as 1t a problem exists , the proper approach to­ life lines , safety nets , stanchions , etc. ward a solution is to contac t the Ships eliminates the possibility of me tal to me tal Logistics Manager, who can in turn task contact . In some instance� , it may be more NAVSEC to provide analysis and a solu tion . economical to completely insulate a metallic

ORIGINAL 1-89 ...... - ..- .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

obj ect from the surrounding structure than to k. lo udspea ker Testing in Shipboard Announcing replace it with a non-me tallic one . Systems Transmitter powe r in exc ess of the leve l required for good commun icat ions should not Loudspeaker testing on shipboard an­ nouncing systems is commonly accomplished be used. Operating tra nsmitters at maximum OOD power greatly extends the area in wh ich by reques ting the to make a count test; efec tive speakers are ident if ied by their metal obj ects wi ll sustain induced vo ltages , d low volume or total failure to produce any and thus become capab le of producing broad­ sound . While this test method is effective , band impu ls ive noise . Circuits carrying it is also inconven ient because it requires heavy traffic should be rout ed to an tennas the active pa rticipation of the OOD , and furthest removed from areas wh ere running because it unnecessarily energizes all the rigging is ins talled and handled. speakers in the system in order to test a Long term remedial action includes the single speaker , result ing in annoyance to installat ion of br oadband an tennas and re­ the rest of the crew. ceiving and transmitting multicouplers. A better method of testing individual The reduction in the number of ant ennas will speakers is to temporarily disconnect the permit the antenna arranger to reduce EMI speaker from the ship 's wiring , and then prob lems by increasing the separation be­ connect an audio signal genera to r (such as tween susceptib le are as and transmi tting the AN /URM-12 7 or the CAQI-201C) to the antenn (EIB 862) as . high voltage side of the transformer (terminals MC70V and MCC COM) . When the signal generator is adj usted to deliver a tone of about 1 KHz , at a leve l of 30 to 50 vo lts rms , a loud sound will be produced j. NTDS Computers, l:hta Display s, Peripheral and in a properly operating speaker . In this Communications Sy stems Cooling Water manner, the announcing sys tem loudspeakers a , Tem peratures--Informa tion Concerning may be tested one at time with minimum annoyance . (E/8 863)

NAVSECNORD IV representatives vi siting NTDS equ ipped ships and stat ions have noted many instances where coo ling wa ter supplied to subj ect systems was being ma intained at tem­ I. Teletypewriter Equipmen t-Maintenance Hint peratures as low as 55° F. Since these te m­ pera tures are obviously far below normal am­ bient tempera tures of associated equ ipment The purpose of this article is to pro- · spaces, cond ensation frequently occurs on in­ vide information concerning stock numbers u ica terior equ ipment surfaces causing con:os iuu , for l b r nts and cleaning agen ts specified arcing in high vo l tage circuits and even tual on Maintenanc e Re quirement Cards for tele­ equipment failures. This is espec ially true typewriter eq uipment . in ships operat ing in hi gh humid ity env iron­ The federal stock numbers for thes e ment s. lubrJcants and cleaning agents may be found The purpose of this ar ticle is to correct in the Electronics Ins tall at ion and Main­ the false assumption of many cognizant ma inte­ tenance Book (EIMB) , General Maintenance , nance personnel that the forego ing cooling NAVSHIPS 0967-000-0160 , tab les 3-3 and 3- 6. water temperatures are normal and to ensure Quant i ties of lubri cants required is to be that all NTDS maintenance per sonnel adhere to de termined by us ing activities . the following : Lint free rags may be ordered under 1. Ma intain cooling wa ter supplied to Federal St ock Number 79 20-401-80 34 , p ackage subj ect systems equ ipment hea t exchangers at a of 100 . temperature of 73° F ±3 °·. Federal Stock Number 9150-252-6173 2. Align circuits on ly when equipment specified in EIB 798 dated 22 Mar 1971 is operating tempera ture has stabilized with for a non-flui d oil wh ich is intended for cooling wa ter temperature ma intained within use with "Mi te" TT-29 9/UG series equipme nt . the forego ing limits. Th is oil is not to be used on Mo del 28 Tele ­ 3. Become generally familiar with the typewri ter equipment . capabilities of own ship ' s coo ling wa ter tem­ Inclusion of this information will be perature control system . (ElB 879) recommended for fu ture revision of Teletype­ writer Mai ntenance Requirement Cards . (EIB 885)

/ OR IGINAL 1-90 ...... - .. - .. - .. -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

; the connector , either , nut" type as in figure m. Weatherproofing and Corrosion Prevention of Topside 1 or "flang e" type as in figure 2, has Perma­ Hardware-Additional Details to EIB 854 tex applied at time of assembly into the case. Sealant dabbed on later and painted is only The article in EIB 854 wa s enthusias­ effective against direct wa ter entry and its tically received and many comments were corrosion, but for pressurized cab inets it contributed--both pro and con . mu st be applied between the ca se and the The con comments are all about a single connecto r. Applied this way even a moder­ point--SAFETY . All hand s have been advised ately tight enclo sure is effectively sealed many times to be car eful of solvents--a par­ if pressur ized. ticular case is carbon tetrachlor id e, a pop­ The following procedure is suggested as a ular cleaner and fire ex t ingu i sher of a few method for sealing cable connector s such that years ago now replaced by a "safe" (but not removal of seal ing ma terial is easy and leaves very) solvent 0-T-620C (tricloroethane 1,1,1) . the connector s clean and not full of sticky Section 413 of NAVSHIPS 9600 is qu ite illumi­ sealant. (Add a ground wire to the connector nating in regard to the explosive and suffo­ if the wires inside don' t have shrinkable cating properties of � ga s, par ticularly the sleeving over each soldered connec tion as re­ evaporative produc ts of cleaners, paints, quired for Safety in MIL-STD-1310C .) pocket cigarette lighter fluid and "safe" sol­ 1. Ensure connector is clean and dry . vents . NAVS HIPS 9600 .413 is one page of real 2. Apply a light coat of silicone grease ev eryday informa tion . "Safe" solvents such as (DC-5 or equivalent, NSN 6850-00-963-54 02) to tricloroethane (methylchloroform) mentioned in connector threads . the first EIB article are absolutely forbidden 3. Reconnec t connec tor plug . on submar ines and must be stored in a paint 4. Cable armor causes wicking of salt locker on surface ships . Equally ha zardous wa ter into the pins if the armor is secured und er the connector clamp back . If armor is are spray cans of anything . Freon (which is present cut the armor back 4 inches from the the most used spray can propellant) is taboo connector , add a ground strap about 6 inches on submarines and combined with paint/solvent from the connector and serve the end of the it makes a first class hazard for below decks armor and new ground strap clamp with vinyl use on surface ships . It is recommended that tape. See figure 3. spray cans of solvent be maintained at a 5. Using sil icone rubber (sel f-bond ing ) minimum level and issued to wo rking personnel tape (NSN 597 0-00-955-9976) wrap an over­ for topside and aloft use only . lapping layer from the panel to the cable. The pro comments encouraged publ ication Ma ke sure holes of the connec tor at the cable of more weatherproofing techniques . This clamp are covered and continue the tape about article is to standard ize the installation and 2 inches onto the cable. See figure 4. preserva t ion of connec tors whic h are exposed 6. Using vinyl plastic tape (NSN 5970- to water and sal t spray. With th is proc edure 00-284 -8410 typical) wrap the connector with for protec tion of connections corrective main­ one or two layers from the panel to the armor . tenance can proceed quickly and without worry Pull the tape tight and overlap about one half . that a corrosion problem is hidden inside the connector. 7. Apply at least two co ats of Scotch­ Proper pr epar ation of connectors used ka te (NSN 5970-00-962-3335) from the panel to the cable. The Sco tchkote is designed to topside will insure long life. The next time pro tect vinyl tape from the weather ; regular a chassis connector is removed during correc ­ tive ma intenanc e put it back using this tech­ paint and other co atings will soften the tape and cause it to unwind . See figure 5. nique. Wire brushing , solvent clean , Perma tex The explanation for the two different II and a final coat of paint make a tight seal against corrosion and minimize connector re­ kinds of tape is tha t the first layer won 't stick to the connector and the second layer placement and chassis co rrosion . No te that plus the Sco tchko te provides strength and

/

PERMATEX n Figure 1. Nut Type Connector Figure 2. Flange Type Connector

ORIGINAL 1-91 ...... - ... - ... - ... -

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

weather tightness. A jacknife will lay open this cocoon with a straight leng thwise cut leaving the connector in original cond ition with no stickness or clogged threads. Don 't forget to tape over or plastic bag any cable connector removed and to be left unconnec ted overnight . Rain and salty air can begin building an insulating layer on the pins pretty quickly. A couple of precaut ions with Permatex type products: 1. The stock system type II wa s coming through too thin for awhile. GSA wa s notified last year. 2. All three types are almost impossible to remove from clothes . 3. Don 't use on gaskets (even edges) Figure 5. Application of Scotchkote that are to be reused . Us e DC-4 or 5 on re­ usable gaskets unless something el se is al­ ready specif ied. (EIB 896) 4. Type III really sticks; keep it away f rom nut and bolt threads .

Figure 3. Removal of Cable Armor

Figure 4. Taped Connector and Cable

ORIGINAL l-92 ...... · , . . ..- .. - ..- .. -

COMMUNICATI ONS NAVSEA 0967-LP-000- 001 0 GENERAL

n. Cable Terminating Aid lor Terminating lllocklor IDF/ MDF

The terminat ing block shown in figures 1 through 3 of this art icle is recommended to fac ilitate the terminating of cable on an lDF/ block . With the use of the terminating MDF block (figure dressed wire ends to be ter­ 2) minated are held firmly in place, thus elimi­ na t ing the need to reloc ate color-c oded wires that have already been determined . The ter­ minat ing bl ock allows neatne ss of finished wo rk, thereby decr eas ing the possibil ity of a defec tive term inat ion . Con struction of the terminat ing block is in acc ordance with gur es and 3. fi 2

'·:

1. Figure Terminating Block for IDF/MDF

'. J ORIGINAL 1-93 ...... - ,- ,- .. -

COMMUNICATIONS NAVSEA 0967-LP-000-001 0 GENERAL

HOLES 3/16", 2

14------7- 1/2"------�

Figure 2. Construction and Use of Cable Terminating Block

LIST OF MATERIAL -- NO. DESCRIPTION QTY REMARKS

LUCilE BLOCKS CD 2 PA N-TY NO. PLT1M-CP lOR EQUIV.) II� CABLE TIES 2 113) MACH INE SCREW, STEE<.#I0 -32 x3/8 " I MACHINE SCREW, STEEL I 11-D #I0-32x 1" FLAT WASHERS, STEEL# 5 10 3 NUTS, STEEL (6 110-32 2 WINGNUT, STEEL# (7 10-32 I __ ..-- -'� ------.}-_J ------2 ------7 ------

89G) \ EIB Figure 3. Materials and Construction of Terminating Block

ORIGINAL l-94 ......

COMMUNICATIONS NAVSEA 0967-LP-000-0010 GENERAL

o. HF Communications Antennas, Trussed Monopo le� q. MARS Operations Afloa t--Au thori­ zation and Appl ication Informati o n

Attention is invited to the fact tha t A recent issue of ALL HANDS magazine the Navy now reco�ne nds the use of two ver­ (March published an article "All sions only of the trussed r:,o nopole Hr' co�u­ 1976) About MARS providing' information on the nications antenna s for shipboard installa tion. " system . NAVTELCOM INSTRUCTION 2371.1 of 6. These antenna s ( known familiarly as "trus sed October 1975 promulgates the policies, whips" ) are : instructions , and guidance concerning the a. A foot three-wire open tip de­ 35 Navy-Marine Corps Military Affiliate Radio sign standardized for operation from 2-30 System MHz receive ( or 4-12 MHz tra nsmit ) . (MARS) . Ships and ac tivities desiring to apply b. A foot four-wire open tip design 15 for MARS operations should request applica­ standardized for operation from MH z, 10-30 tion Form DD-630 from : receive or transmit . These reco�e ndations follow from an extensive study performed by the Na va l Elec­ Chief, Navy-Marine Corps MARS tronics La boratory Center ( NELC ) , Sa n Diego Bldg . 17 , 8th & S. Courthouse Rd . and sponsored by NAVSEA 6102. Compl ete de­ Arlington , VA 22204 tails necessary for con struction of the two trussed mo nopoles and results of mecha nical/ Autovon 222-0393 or commercial electrica l tests are conta ined in NELC 202-692-0393 Technical Document of 1 De cember 1974 376 The completed Form DD-630 (three entitled Standardized Trussed Monopole Co�u­ copies) should be forwarded with a letter nications Antenna . TO wa s widely distri­ 376 of transmittal originated by the command buted to Na vy co� nds and shipya rds ; official exercising military jurisdiction to the requests for copies may be addressed to NELC foregoing address . Information copies of Sa n Diego CA ATTN: Code However , 92152 2100. the transmittal letter shall be addressed all requests for full size reproducible copies to the chain of command . Upon receip t of or prints of the antenna drawings appearing the DD -630 applications , the MARS office as figures l and 2 of TO should-be ad- 376 �o.· Hl forward a station license with MA.RS dressed to NAVSEA , Washington, DC , rad io call sign , a copy of the MARS Com­ 20362, Attn : Code 61 4. (EIB 897) munication Instructions NTP-8 ( ) and in­ formation concerning the established Maritime Mobile Radiotelephone/Teletype Network . p. Defective Rotron Muffin Fans in (EIB 930) Teletype Equipment- -Ma intenance Hin t Frequency Meter Re placement on IC

The purpose of this article is to Swi tchboard in Navigation Center-­ recommend a maintenance act ion to relieve Availab ility of a possible deficiency present in certain The purpose of this ar ticle is to an­ Rotron Muffin Fans . The affected fans are nounce the av ailability from NSPCC Mechan­ labeled Mark 4 Series M-747 and are date icsburg , PA of a new 3-1/2-in. round fre­ coded between 9010 and 71480. The code is quency meter manufactured by the A & M Com­ stamped on the outside of the venturi , or pany to replace a present me ter manufac­ on one of the legs. A defective manufac­ tured by the American Machine and Foundry turing process in these particular fans (AMF) Company . may cause arcing and momentary flashover Mo st of the frequency me ters which of the plastic duct , result ing in the loss have been used in the Fleet were furnished of fan operation . Mark 4 fans , other than by the AMF Company . Informa tion received as indicated herein , are not affec ted. The from the Fleet ind icates that the 400 Hertz Rotron Mu ffin Fan Mark 5 is not affected . frequency me ter on the I.C. sw itchboard in The recommended action is to inspect the nav igation center on the SSN 637 , the mu ffin fan during routine maintenance. SSBN 598, and SSBN 608 classes register If it is one of the affected fans , remove incorrectly when the energy being monitored and replace with a new muffin fan, other contains certain harmonics , even though than the affected series and date codes . the harmonic content is within accep table (EIB 930) ship specifications . A typical symptom re­ ported is oscillation of the meter pointer at a rate which is obviously faster than reasonable. Sometimes the meter pointer

ORIGINAL l-95 ...... - ... -

COMMUNICATIONS GENERAL NAV SEA 0967-LP-000-0010 will "peg" off-scale when a load is applied . C5510.93B, enclosure (2) , section 1, paragraph Another symptom of harmonic influence on lu (2). the frequency me ter is different readings Figure lA illu s t rat es a typical receive on different phases. teletype circuit wi th both a page printer and Existing installations where the fore­ a reperforator on the same loop . Figure lB going symptoms are observed can be cor­ illustrates the insert ion of the SMD at the in­ rected by replacement of the present fre­ put to the page printer in that loop . Figure quency me ter with the new meter manufac tured 2 illustrates a typical box housing with flange by the A & M Company wh ich is available type construction to prov ide adequate shielding . from NSPCC Mechanicsburg , PA and identified Figure 3 is an outline and mounting drawing of by FSN lN 6625-00-054-2143 . (EIB 930) a typical box housing for the �ID . Figure 4 illustrates component mounting (assembly drawing) and interconnecting data . S . Installation of Selector Magnet Driver Tempest criteria requires that the SMD The purpose of this article is to provide be installed to provide ad equate shield ing Tempest criteria for the installation of a to the driver and the interconnecting cables. selector magnet driver (SMD) when such a de­ The SMD shall be physically located as close vice has been otherwise approved as a change to the associated teletypewriter as possible . to the teletype sys tem. Many receive teletype­ Primary a. c. power for the SI1D shall be con­ writer systems encounter excessively high nected to the primary a.c. power terminals of signal distortion on teletype lo ops lvh ich can the ex isting teletypewriter . Only shie lded be reduced by the in stallation of an SHD at cable shall be used for signal and power cables. the inpu t to the receive pag e printer . The SMD Cable shields shall be bonded to ground at is essentially a relay wh ich isolates the tele­ each end of the cables. The SI1D box housing typewriter input circuit from the teletype shall be bonded to ground via the mounting loop . Prior to installation on non-me tallic hard1va re to a foundation, shelf or cabinet

hull ships , command s shall assure that the use · ich is already bonded to ground . of the SMD is no t in conflict with OPNAVINST

TELETYPEWRITER . I PAGE PRINTER RECE IVE TELETYPE CRYPTO PATCH UNIT PANEL

I TELETYPEWRITER REPERFORATOR

Figure 1 A. Typical Receive Teletype Loop.

TELETYPE SELECTOR RECE IVE TELETYPEWR ITER CRYPTO PATCH MAGNET PAGE PRINTER UN IT PA NEL DR IVER f--

TELETYPEWRI TER REPERFORATOR

Figure 1 B. Typical Receive Teletype Loop With Selector Magnet Driver.

l-96 ORIGINAL ...... - .. - .. -

COMMUNICAT IONS NAVSEA 0967-LP-000-0010 GENERAL

Figure 2. Typical Box Housing With Flange Type Construction.

ORIGINAL 1-97 GJ " I"Tl " I" 143 3 6 z 4 2 I"Tl ;::o t·------)::> r-r I " 9 +' 1 16 57" ==;i c -- -- 464------I, -G) B '' i(NOTE 7) --��-E s_ l_ ---=!r 5" 2" AR 16 6"REF I" 4 ' R=l'ftl 2 ..J._-t-- � . +t. :l .. I +A -+,A .------#-----+--;1------�� I - L_: L_: ( NOTE 3) z I {' :_14 )::> - ___j --t+l--!1----L I rc+ ------< \,.I (/) - -- - _,,� I"Tl L .. )::> 2 316 t L. 0 L3tREF_j 1.0 1, t------5" [8"REF " (j) ------.! "--.J I I 1.0 I CXl � '"'0 I )PART OF FIND NO. I I 0 0 HOLE SCHEDULE 0 LT R SIZE NO. REQ I 0 0 A 9/64" 4 __, B 3/16" 4 0

5/16"DIA OR c 4 TO SUIT

D 5/8 " I . E 7/ 8" I _L__ I,

("') 0 3: 3: c z >--< 0 ("') ;::o )::> >--< --l GJ >--< >--< 0 z z )::> Figure 3. SMD Box Housing, Outline and Mounting Drawing. Vl '

1, ...... ,- ,- ,- ,-

COMMUNICAT IONS NAVSEA 0967-LP-000-001 0 GENERAL

II II tJ ,, It II ,, ,, II 11 II II 1 II II I /1 It ,, ,, I'' '' ,,, ,,

SEE LIST OF MATERIALS FOR FIND NUMBERS

Figure 4. SMD Component Mounting (Assembly Drawing) and Interconnecting Data.

ORIGINAL 1-99 ...... ,- .. - .. - ...

NAVSEA GENERAL 0967-LP-000-0010 COMMUNICATI ONS

Subs titution of items in the list of g. Find Nos . 8 through 16 mounting materials may be made providing the following hardware may be su bstituted to suit component essential criteria is maintained : mounting holes . a. Find No . 1. Box and box-cover mu st h. Find J';o . 17 . Terminal lugs may be be me tal . Cover, when in place , shall have crimp or solder. me tal-to-metal bond to the box . The following no tes app ly to figures b. Find No . 2. Selector magnet driver . 2, 3 and 4: No substitution . 1. All dimensions are in inches. c. Find No . 3. Terminal board shall have 2. Locate the SND box as close as a minimum of six lug connections inside the possible to the associated teletypewriter. box . Terminal board lugs shall accept wire 3. Use these dimensions to locate size AWG 14 (for power) and A\o/G 28 (for signal ). holes in selector magne t driver (Find No . 2) d. Find No. 4. Power cable shall be cover. Mount selector magnet driver to box )-conductor , minimum wire gage Alo/G 1 4 , '"i th using sheet metal screws (Find No . 16) . overall shield . 4. Connect power leads (BLK & WHT) to ex­ e. Find No. 5. Signal cable shall be isting teletypewriter equipment . 2-conductor , minimum '" ire gage A\.JG 2 8 , with 5. Connect cable shields and third wire ov erall shield . power ground to case . f. Find No s. 6 and 7. Box connectors 6. If substitute ter minal board is used , shall securely fas ten to the box and provide match drill mounting holes using terminal board a snug fit for penetrating cables . as template . 7. If substitute box connectors are used , drill to suit . Find No. Des cription

1 1 Metal box with cover for complete shield ing , aluminum , 6 x 8 x 3.5 inches, Bud Rad io Inc model OU-3009A, or equivalent . 2 1 Selector magnet driver 58ls-oo-On 5-9728 3 1 Terminal board , barrier, screw type , 5940-00-983-605 3 double row , front connection (linked ),

rated voltage 300 vo lts , class 3 7TB12 . 4 A R Cable , power , )-conductor AHG 14 , 6145-00-83R-0005 overall shield , type 3SJ-14 5 A R Cable , signal , 1-pair shielded , A\.J(; 28 6145-00-553-7823 type RG-108A/U 6 1 !:lox connec tor , two-screw , for non­ metallic sheathed cable .450 to .720 inch diameter , trade size 3/4-inch. T&B part no . 3303 , or equivalent 7 1 Box connector , two-screw , for non me tallic sheathed cable .187 to .500 inch diameter, trade size 1/2-inch. Appleton part no . BC-7286 , or equivalent 8 4 Screw, machine , slotted , steel cadmium p lated , U NC-2A , 6-32, length 3/4-inch. 9 4 Washer, flat-round , steel cadmium plated , id .156 inch. 10 4 Washer , lock-spring , helical , steel cadmium plated , #6. 1 1 4 Nut, plain-hex , machine , steel cadmium p lated , J NC-2B, #6-32. 12 2 Screw , machine , slotted , steel cadmium plated , U NC-2A , 8-32 , length l/2-inch . 13 2 Washer, flat ·round , steel cadmium plated , id .188 inch. 14 2 Washer, lock-spring, helical , steel cadmium plated , #8 . 15 2 Nut , plain-hex , machine , steel cadmium plated , U NC-2 B, UB-32. 16 2 Screws , sheet metal, 11 8-32 . 17 4 Terminal lug , ring tongue , stud size 8, terminal size 14 . (EIB 912) R GI A O I N L l-100 ·, ...... ,- ,-_ .. - .. -

COMMUNICAT IONS NAVSEA 0967-LP-000-00 10 GENERAL

t. Silver Plated Components Used in H i gh Power of the item that is missing (the item not Transmitters-Repair of shipped) . Some of the equipment s involved are : In �ieu ot having plcted and burned silver plated contacts and components TT-570/UG replated by a commercial firm, Navy personnel TT-571/UG can locally clean and replate on site , thus TT-603/UG effecting a cost saving in maintenance funds TT-605 /UG and possible extended down time on equipment . AN/UGC-77 (EIB 7 Components requiring cleaning and/or AN/UGR-9 94 ) replating can be removed from equipment and disassembled as though they were going to be sent out to a commercial firm for replating . . Teletypewr iter Clutch Shoe Lever Each part requiring cleaning and/or replating can be cleaned by brushing with "Tarn-X" Cleara nce--Information Concerning compound and then cleaned in an ultrasonic It has come to the attention of this cleaner using the normal cleaning agents . command that various activities have been After cleaning , the components should be making the adjustment of the teletype thoroughly rinsed and brushed a second time clutch shoe levers improperly. The gap with the "Tarn-X" compound , rinsed again and between the clutch shoe lever and its stop cool air dried . Any burned areas should be lug should be 0.055 inch to 0.085 inch removed with a fine sand paper or wire brush . greater when the clutch is engaged than Replating is accomplished by applying when the clutch is disenga�ed . For a one "Cool Amp" powder with a damp rag or small hundred words per minute machine , the gap stiff brush, depositing a silver plate on between the clutch shoe lever and its stop the component by lightly rubbing the area lug should be 0.070 inch to 0.075 inch to be plated . greater when the clutch is engaged than Materials required for this process : when the clutch is disengaged . a. TARN-X , JELMAR CO . One Illinois The procedure for making clutch shoe Center Suite 2820 Merchandise Mart , Chicago , lever gap check is as follows . Trip the IL 60654, $14 .50 per gallon - 4 gal . minimum . clutch and rotate it until the clutch shoe b. COOL AMP Silver Plate Powder , lever is toward the bottom of the unit . COOL AMP CO ., 8603 175th Av e. , S.W. , Align the head of the clutch drum mounting Portland , OR 97219, $23.25 plus postage per screw with the stop lug . Manually compress pound . the shoe lever against the stop lug and This procedure may not be successful allow it to snap apart . Measure the gap in cases of extremely severe burned or with the clutch, thus engaged , and note pitted components where the me tallic surface the reading . Disengage the clutch and has been badly damaged . (EIB 944) measure the gap . Subtract the second read­ ing from the first reading . The difference between the two readings is the clearance requirement for the clutch shoe lever . . Low Level Tel etype Equlpment-­ (EIB 951) General Informa tion The purpose of this article is to insure that the Electrical Service Assembly (ESA) and wiring are packaged together with the low level teletype equipment whenever either item is shipped for any reason such as :

(l) A Surplus Item (2) Overhaul/Repair (3) A Direc t Turn in Item

Since the (ESA} is a' component part of the low level teletype. equipment , the two items are listed togeth�r as a single unit under one National Stock Number (NSN) . Therefore , when either item is shipped , both items must be kept together to prevent the repurchasing

ORIGINAL 1-l 01 ...... - ...- ... - ...-

GENERAL NAVSEA 0967-LP-000-0010 COMMUNICATIONS

w. Information on Bonding to Meet TEMPEST-Rela ted Installation Criteria

The purpose of this art icle is to provide a tabulat ion of nat i onal stock numbers and prices ( estimat ed ) for various bond straps and bonding hardware, and additional information conc erning Tempist-related bonding requirement s. For Tempest-relat ed purposes , bond straps are required only on resili ent mounted equipment , slide foundations , crypt ographic and cryptographic anci llary equipment , and power iine filters . The resilient mounted equip­ . ; ment , frequencly called shock-mounted equipment , and slide foundations do not have an RF bond met al-to-metal cont act between the equipment itself and its supporting foundat ion , and there fore needs a bond strap . Crypt ographic and crypt ographic anc illary equipment is that equipment with a type desig­ nation having a suffix or prefix of "TSEC ." Power line filters , becaus e of their construction , require bond straps . Other equipment may use the metal­ to metal contact inherent in the mount ing hardware, provided that paint , grease, lacquer and other resistive materials are removed from the surface contact area prior to mount ing , that all available mounting holes ar e used , and that the diamet er of the mount ing bolts , nut s and washers conform to the existing mount ing holes . What is a good bond to ground? Why not use the safety ground wire if it exist s? The definition for bonding used in Tempest-related installation criteria is short and to the point . "The proc ess of physically providing a posit ive , direct and cont inuous , metallic , low impedance d.c . to RF path between conducting mat erials ." Each word in that definition is important , but probably the mo st important are the "low imp edance d.c. to RF path." Th is means the minimum possible impedance is required throughout the frequency spectrum from 0 Hz into the radio frequencies . For a bond strap to meet this requirement , it must have certain minimum dimensions such as those specified in the detailed bonding requirement paragraphs of MIL-STD- 1680. The conductor in a power cable used for safety (3rd wire ground ) cannot qualify as a bond . The length of the cable from the equipment to the power distribution panel whe re the safety conductor is connected to ground may be 15, 20 or 25 feet in length. Any conductor this long is not a low impedance d.c. to RF path . The flexible bond strap is intended for those eauipments that necessarily must be moved in the course of normal operations , such as to gain access for teletype paper replenishment , or for changing switch settings. The mo st common usage is on the slide foundation in an equipment cabinet . Using the ma terial listed below, the bond strap should no t exceed 12 inches in length (some installations may require as much as 14 inches), but should always be as short as practicable .

Unit of Item Issue Price NSN

Flat braided wire foot 25 � 9I-6145-00-669-5552 (l-inch, 352 wires , (The NSN listed in 36 AWG uncoated copper) MIL-STD-1680 , para. 5.1.13.3 is incorrect)

Tube, me tallic foot 92¢ 9C-4710-00-277-4023 (0.840-inch diameter)

The solid bond strap shall no t be longer than 8 inches and not less than 3/4-inch in width (the length-to-width ratio shall no t exceed five-to-one). The thickness of the flat copper shall not be less than 0.020-inch . Nat ional stock numbers for common lengths of

ORIGINAL 1-102 ...... - .. - .. - .. -

COMMUNICAT IONS NAVSEA 0967-LP-000-00 10 GENERAL

solid bond straps are tabulated below . Solid bond straps in excess of 5 inches are not available in the supply system and must be fabricated locally .

Unit of Item Issue Price NSN

Bus , conductor each 26¢ 9G-6150-0l-016-4648 (length 2", cadmium plated bond strap)

Bus, conductor each 27¢ 9G-6150-0l-016-5289 (length 3" , cadmium plated bond strap)

Bus , conductor each 29¢ 9G-6150-0l-016-5288 (length 4", cadmium plated bond strap)

Ground strap each 44¢ 9G-5940-00-025-9083 (length 5", cadmium plated bond strap)

A minimum of 5/16-inch hardware is required in order to provide sufficient electrical bonding contact area . The split-lock and flat washers of 5/16-inch hardware provide this bonding contact area . Hardware of lesser dimensions will not . Commonly used hardware that is available in the supply system is listed below : Unit of Item Issue Price NSN

Screw, cap , hex each 9¢ 9Z-5305-00-753-4322 (5/16-inch dia, length

1" ' cadmium plated)

Screw, cap , hex each 3¢ 9Z-5305-00-225-9081 (5/16-inch dia, length 1-1/4" , cadmium plated)

Washer, lock , 5/16-inch 100 50¢ 9Z-5310-00-407-9566

Washer , flat, 5/16-inch 100 78¢ 9Z-5310-00-809-3078

Nut , plain, hex , each 20¢ 9Z-5310-00-829-9981 5/16-inch

The bond strap loses its effectiveness un less grease , paint , lacquer, dirt and other resistive ma terials are removed from the area where the bonding strap is connected to the equipment or the foundation (bonding co ntact area) prior to mounting . Bond straps had previously been required on many other equipments in the Tempest environment . Th ese requirements have been considerably reduced . Therefore many bond straps may exist on equipment that no longer require them . Such a case may exist for rack-mounted or non-resilient mounted equipment . However, during in itial installation of this equipment , the surface contact area surrounding the mounting hardware may not have been properly prepared for a good bond , in that the bond strap was being used for this purpose. If this surface contact area surrounding the mounting hardware is properly cleaned of paint , dirt and other resistive ma terials , the bond straps are no longer required . Retaining these bond straps certainly does no harm , if they are maintained in good condition . But frequently these bond straps fall into disrepair, are not connected at one end , or have an abundance of paint or other resistive materials between the bonding surfaces . If the bond strap falls into disrepair , and it is not required , it might be we ll to remove the bond strap , provided the surface contact are a of the "'"''n �{,g hardware is properly cleaned . (EIB 957)

/ ORIGINAL 1 - 1 03 ... - ... - ... - ... -