THE WIRELESS ENGINEER A ND EXPERIMENTAL WIRELESS
VOL. XI. JANUARY, 1934. No. 124
Editorials What is Demodulation? to a non-military condition, and not the collection of the military elements for use. IN our correspondence columns we. publish Similarly, if we turn to a dictionary for a letter from a Canadian reader with examples, we find decarbonise, to deprive reference to the regrettable fact that the of carbon ; dechristianise, to destroy Chris- word " demodulation " is used by different tian elements ; deconsecrate, to deprive in people two entirely different senses. Our of the character given by consecration ; correspondent plumps for the American depopulate, to deprive of population ; and usage, and it may be that there is something so on. In every case the idea is that of the to say for it, but we certainly do not agree restoration or conversion to a different that " demodulation here has its logical condition by the removal or destruction of meaning as related to modulation." In our something. In this country demodulation opinion the American use of the word to is used in this sense, viz.: the partial or mean detection or rectification is a misuse entire removal or suppression of the modu- of the word ; it may be a convenient misuse ; lation, thus restoring the carrier more or it is certainly a very common one in America. less to its original unmodulated condition. Starting from an unmodulated high -fre- If one wanted to use the water which was quency carrier, it is modulated by causing absorbed in a body one would speak of its amplitude to vary. What would anyone extracting the water and not of dehydrating whose judgment had not been warped by the body ; the latter expression would give continual use of the word in a special sense an entirely wrong idea. In our opinion understand by the demodulation of this it is equally wrong and misleading to refer modulated carrier ? Surely the restoration to a valve as a demodulating valve when its to the previous unmodulated state, either function is to extract and pass on the wholly or in part. When an ionised space modulating element from the modulated is said to have been de -ionised one merely carrier, the carrier itself being generally means that the space has been restored to its destroyed. If " rectifier " is undesirable- un -ionised condition, and, generally speaking, and our correspondent appear_, to dislike one does not care what has become of the it in spite of the time-honoured grid -leak ions. When a State is demilitarised, one and anode -bend rectifiers-and it is thought thinks only of the restoration of the State necessary to include the term " modulation," January, '934 2 THE WIRELESS ENGINEER & we would suggest that our American friends correspondent for twenty years. If it is should find something equivalent to " modu- true, or even if there is any truth whatever lation extractor," and leave the word in it, it is a very important matter which " demodulator " for that which really de- calls for immediate investigation. There modulates in the proper sense of the term. should now be available ample data to It would be wrong, however, to assume that prove or disprove the truth of the statement. everybody in America uses the term in Field strength measurements have been preference to " detection" or "rectification." made on many transmitting aerials and it In Radio Engineering, by Terman of Stanford should he a relatively simple matter for University, the word " Demodulation " is to broadcasting authorities to compare measure- be found in the index, but with the reference ments made after one or two years' operation results obtained when the aerial ; the ' ` see Detectors " and it is as Detectors with that they are described in the text. Our was undergoing its preliminary tests. If correspondent is probably correct as to the these investigations show any appreciable date of the coining of the term demodulation. variation in the radiating efficiency of the It is not mentioned in Morecroft's Principles aerial we shall be very surprised, and we of Radio Engineering published in 1921. shall certainly be faced with a problem which will merit the serious attention of all broadcasting organisations. Our corres- The Earth Resistance of pondent does not say whether he suspects Transmitting Aerials the aerial current of falling away from its IN this issue we publish a letter from a initial value-which would be detected by correspondent suggesting that trans- means of an aerial ammeter or whether mitting stations deteriorate rapidly after he thinks that the earth becomes so poisoned commencing operations, and that within that the radiation for a given aerial current a short time the signals which were originally is reduced. Such points can safely be left loud fade away until they can only he heard until we know if there is any objective with difficulty. This is referred to as a experimental support for the alleged pheno- phenomenon which has been known to our menon. G. W. O. H.
The new German short-wave centre at Zeesen, near Berlin, with directional aerial " arrays" for transmission to North and South America, South Africa and the Far East. An omni-directional service is also provided for. EXPERIMENTAL. WIRELESS 3 January, 1934
Ultra -short Radio Waves * Refraction in the Lower Atmosphere By R. L. Smith -Rose, D.Sc., Ph.D., A.M.LE.E., and J. S. McPetrie, B.Sc., A.M.I.E.E. (The National Physical Laboratory)
ABSTRACT.-This paper considers some aspects of the problem of the refraction of electric waves in the lower atmosphere due to the variation of density of the air with altitude. As a result of this refraction the path of waves between a transmitter and receiver is curved in a manner concave to the earth's surface. It is shown that for average atmospheric con- ditions the radius of curvature of this path is about six times the radius of the earth. The effective maximum range between a transmitter and receiver using waves following such a curved path is calculated for different heights of the two stations, and is shown to be materially greater than the maximum range obtainable assuming that the waves employed follow a straight line tangential to the earth's surface. A summary of previous work is given and particular attention is drawn to the experi- mental evidence on wavelengths between 0.5 and 8 metres indicating possible communication ranges of nearly fifty per cent. in excess of those determined by the rectilinear or optical path.t On the basis of the calculations made in this paper, it appears that the curvature of the waves by refraction is not sufficient to explain some of the experimental results. The phenomenon of fading, which was encountered in some of the experiments, is explicable, however, as the result of convection currents in the air causing a variation in the refractive index. The possible contribution of diffraction effects around the curvature of the earth is mentioned, but is not considered in any detail.
I. General transmitter, elevated to 2,460 feet, would CnNSIDERABLE interest has been pass tangentially along the earth's surface, aroused recently as the result of success- and then on to the receiver at an altitude of ful experiments demonstrating the 1,115 feet.$ It was evident, therefore, that application of electric waves of less than one the waves from the transmitter were subject metre in wavelength to practical radio to a considerable deviation, which allowed communication. In March, 1931, a demon- them to bend round the earth's surface. stration was given by the International This deviation could be produced either by Telephone and Telegraph Laboratories of optical diffraction of the waves round the radio communication across the English curvature of the earth, or by the refraction Channel on a wavelength of about 17 cm.1 of the waves in passing through the lower More recently, Marconi' has obtained com- regions of the atmosphere. It is the purpose of of munication on a wavelength of 50 cms. over this paper to discuss some aspects the distances up to 168 miles from a transmitter latter possibility. near Rome and a receiver situated on the of by Path island of Sardinia. In each of these experi- II. Limitation Range Rectilinear ments reflectors were used at the trans- If the waves from a transmitter T in Fig. i mitting end to concentrate the radiation into are restricted to rectilinear paths then the a beam, and a similar reflector was used at maximum range obtainable will be TR1, the receiving end to improve the efficiency where R1 is the point at which the tangent of the whole system. A feature of Marconi's TR1R2 touches the earth's surface. The experiment which attracted attention was distance d1 between transmitter and re- that the range obtained (168 miles) was in ceiver is commonly referred to as the maxi- excess of the maximum distance (about 107 miles) at which a straight line from the $ In the lecture by Marchese Marconi, the optical range as determined by this rectilinear path was * MS. accepted by the Editor, March, 1933. given as only 72 miles, which is inconsistent with the t Since the writing of this paper, the above heights of transmitter (75o m.) and receiver (34o m.) communication ranges have been considerably described. (See I 'orld Radio, December 30th, extended. 1932, p. 1,380.) January, 1934 4 THE WIRELESS ENGINEER & mum range obtainable by the so-called ments an experimental radio channel was optical path. At points within the range installed in 1929 to link up Corsica with the TR, reception will be possible by means of French land -line telephone system. By the waves which arrive at an angle to the earth's use of parabolic reflectors at both ends, it surface. Simple consideration of the geo- has been found possible to reduce the power metry of Fig. I will show that the above to 150 watts, and still maintain a commercial limiting distance between transmitter and service under all conditions. 'With a wave- receiver is given by the expression i/2h1R to length of 5 or 6 metres, regular communica- of an% approximation sufficient for most prac- tion can be maintained with a power 35 tical purposes, where h, is the height of watts. Experience with this service first the Ltransmitter above the surface and R brought to light the fact that the distance at which the waves can be satisfactorily T R1 R2 received is beyond the limit of the straight h2 h, line optical path tangential to the earth's e surface (see Fig. 1). It was also noticed that PG towards sunset on warm, bright days, fading 5 occurred on the received signals. This fading was not experienced on overcast days or long after sunset. These experiences were considered to establish the fact that the short waves employed are refracted in travelling through the lower atmosphere to such an extent as to produce a total deviation in the vertical plane of about 2° from the rectilinear path. The fading effects were attributed to the variation in refraction resulting from the density variations of the Fig. 1. -=Showing optical path of waves from a air over the sea, as the latter cools down transmitter at T to receivers at R, and R2. in the neighbourhood of sunset. The gain in signalling range which results from the is the radius of the earth. If the receiver normal steady refraction effects appears to is raised to a height h2 the range is be considerable, e.g., in the case of the correspondingly increased by an amount Corsica -France service, the optical range is d2 = '2h2R, as indicated by the point R2 in about 109 miles, whereas the actual distance Fig. 1. operated is nearly 130 miles. In June, 1932, installations of a more III. Practical Results with Ultra -short complete nature were carried out with a view Waves to providing a permanent commercial radio In addition to the results obtained by link in the normal telephone service13. In Marconi, to which reference has already been order to avoid the effect of adverse climatic made, there are several examples of com- conditions upon the overhead lines, the munication having been established on ultra - height of the station in Corsica was reduced short wavelengths at distances considerably to about 66o feet, while that on the mainland in excess of this rectilinear or optical range. was reduced to about 1,640 feet. It was For example, in 1926 experiments were also found desirable to increase the wave- carried out by the French Government with length employed, and these are now 7.6 in. a view to establishing communication be- for communication in one direction and tween France and the island of Corsica, a 8.2 m. in the opposite direction. Under distance of about 130 miles.3 With the these conditions fading effects are sometimes transmitter at an altitude of 2,30o feet and experienced, but they are not sufficient to the receiver at 1,740 feet above sea -level, impede normal communication. communication was easily established over A year or two ago the Radio Corporation this distance on a wavelength of 3.5 metres of America4, explored the possibilities of using an input power at the transmitter of providing radio -telephone communication about 500 watts. Following these experi- between the individual islands of the EXPERIMENTAL WIRELESS 5 January, 1934
Hawaiian group in the Pacific Ocean. These located at the top of a mast 82oft. high, and islands are separated by uninterrupted sea was supplied with a power of about 150 paths varying from 20 or 3o up to 190 miles, watts, while the second set supplied about and it was found easily practicable to estab- 2,000 watts to its aerial at the top of a mast lish commercial communication over these 4oft. high. The receiver was in the optical distances by installing the transmitters and path of the low power, elevated transmitter, receivers at suitable elevated points. At but not in that of the set of higher power, wavelengths of about 7 metres, and with the and it was observed that the signals from aid of directional antenna systems, the the two emitters were of approximately the actual ranges were again found to be con- same intensity. Special tests were carried siderably in excess of those given by the out to confirm the absence of any down -
optical or rectilinear path. For example, coming radiation at the receiver ; yet it was with transmitter and receiver at 4,80o and found that there was a distinct diurnal 1,700 feet respectively, the range obtained variation of signal strength, particularly was 190 miles instead of 134 miles by the on hot sunny days. rectilinear path. In addition to the " commercial " results Extended tests showed that the signal described above, a certain amount of success reception was remarkably free from atmos- has been achieved by amateur experimenters pherics and fading, and from any effect of working in their allotted band on a wave- weather or day and night conditions. As a length of about 5 metres. Successful tele- result of these experiments a telephone phony experiments have been carried out network has been planned, which will link in this country over distances up to 50 the Hawaiian islands together, using a miles', using transportable apparatus and series of wavelengths between 5.5 and S.5 a power supply of less than io watts. In metres. America, enthusiastic experimenters have Some experiments of interest in this used an aeroplane to obtain the necessary connection have also been carried out in altitude for their apparatus, and com- Moscow with a view to ascertaining the munication was established with ground possibilities of ultra -short waves for broad- stations at distances up to ioo miles8. casting and other purposes5. An experi- In this connection it may be noted that ex- mental transmitter was installed on the periments from aircraft to ground have been roof of a building in Moscow, 15oft. high made in Germany, in which the range ob- and operated on wavelengths of from 3.3 tained was over three times the limit im- to 8 metres. With a radiated power of posed by the horizon, a further confirmation about 25o watts, and a super -regenerative of the existence of the bending effects pre- receiver, good reception was obtained at viously described. distances up to 8 miles in the streets of the It will be seen from the above brief review city, and up to about 47 miles outside that there is a good deal of evidence already Moscow. The latter distance, it will be available to show that the range of ultra - noted, is well beyond the horizon from the short waves is not confined to the rectilinear transmitter, and this was attributed to optical path, as depicted in Fig. 1. Among diffraction of the waves round the curvature the possible explanations which can account of the earth, an explanation which is appa- for this increased range, the two most likely rently supported in this case by the fact that are based upon diffraction and refraction on a wavelength of 8 metres the received effects respectively. The amount of diffrac- signals were about 5o times as strong as tion of electric waves around the curved those on 5.6 metres. surface of the earth would he expected to Certain experiments carried out in this decrease as the wavelength is reduced ; country by the Radio Research Boards whereas in the case of refraction through the are of interest in connection with this sub- lower regions of the atmosphere the devia- ject. With the co-operation of the Post tion, and so the range obtained, would (in Office, signals from two transmitters at the absence of anomalous dispersion pheno- Rugby on a wavelength of 5.5 metres have mena) be expected to become larger as the been received at various distances up to -14 wavelength is decreased. Unfortunately, miles. One of these transmitters was there does not seem to be sufficient corrobora- January, 1934 THE WIRELESS ENGINEER &
tive evidence at present available to decide to know the refractive index of the atmo- whether the deviation increases or decreases sphere to considerable accuracy. with the wavelength. In the following This matter was further discussed by J. S. sections certain aspects of the refraction McPetrie and R. M. Wilmotte1Ó in 1927, theory are discussed. who showed that if electromagnetic waves sent upwards from the earth are to return to IV. The Refraction of Waves in the Lower the earth's surface, the dielectric constant Atmosphere of the air must vary in a particular manner In a paper published in igi.L, J. A. Hem- with altitude. Making use of the results of ing9 discussed the deviation of electro- recent investigation of the temperature of magnetic waves by refraction in the atmos- the atmosphere at heights up to 15o km., it phere due to the decreasing density of the was found that the required condition was constituent gases with increasing height not satisfied. It was concluded that for above the earth's surface. It was pointed waves starting out at angles of elevation of out that a ray emitted from a source on the more than about 2' to the earth's surface, earth's surface, starting in a direction ordinary atmospheric refraction plays a tangential to the surface, would be bent in negligible part in the transmission of waves passing through the atmosphere and would to long distances, which, for wavelengths in therefore follow a path the curvature of excess of 8 or 9 metres, is now generally which would be concave to the earth. The accepted as being due to the effect of ionised problem had already been considered in layers in the upper atmosphere. astronomy, and it was known that incoming rays of light from stars or other celestial bodies were refracted in the atmosphere so that their apparent zenith distances were less than the true ones. At the time of publica- tion of the above paper, the interest of in- vestigators was chiefly concentrated upon the finding of an explanation for the trans- mission of electric waves, at wavelengths of several hundred metres to considerable distances, of the order of a quarter of the circumference of the earth. Fleming came conclusion refraction Fig. 2.-Showing curved path of refracted wave to the that ordinary TR2, TRg, compared with the optical path TR1. through the atmosphere, in the absence of from elevated transmitter at T. ionisation, would not account for such long- distance transmission. He also showed that The experimental work on the propaga- if the atmosphere were composed of the gas tion of ultra -short waves summarised in krypton, waves starting out tangentially Section III above makes it desirable to from the surface of the earth would follow a reconsider the problem, and particularly to circular path of curvature equal to that of investigate the paths of waves which start the earth, and such waves would therefore off at angles of less than 2". above the earth's he expected to travel right round the earth surface, and travel through the lower to the Antipodes. regions of the atmosphere at heights of only In 1927, T. Y. Baker14 considered in one or two kilometres. some detail the problem of the refraction of of Refracted Wave electric waves through a hypothetical atmos- V. Calculation of Path phere, in which the direction of propagation It is evident on general grounds that of the waves is everywhere at right -angles refraction of electric waves in the lower to the wave -front, and the wave -velocity atmosphere will increase the effective range is inversely proportional to the refractive of a transmitter. For example, in Fig. 2, index. An important point that emerged TR1 represents the limiting rectilinear path from this paper was the fact that in order of waves from an elevated transmitter T to compute the correct track of electric reaching the earth's surface. Waves start- waves through the atmosphere it is necessary ing from T in a direction above TR1 will be EXPERIMENTAL WIRELESS 7 January, 1934 refracted towards the earth in passing suc- (6,560 feet), as being the limiting height of cessive regions of air of increasing density. interest in this phase of radio communica- Thus such waves would follow a curved path tion at the present time. TR2, reaching the earth at R2 beyond the point R1. To an observer at T the horizon Altitude. Density Radius of would appear to be at R2, whereas for ------of air Curvature rectilinear propagation it would he at R1. Metres. Feet. gms. per c.c. kms. m. In the case of light, this phenomenon is " 0 0 0.001226 37,200 5.8 termed depression of the horizon " and is 500 1,640 0.001167 38,500 6.o well known to sailors. After passing the 1,000 3,280 0.001112 40,000 6.2 earth tangentially at the point R2, the waves 1,500 4,920 0.001058 42,000 6.5 will rise again into the atmosphere, arriving 2,000 6,560 0.001007 43,300 6.7 at an elevated receiver at the point R3. The path TR2R3 is obviously reversible for waves From this table of results it is seen that transmitted in the opposite direction. If as the ray travels outwards through the the lower atmosphere is heated, the density earth's atmosphere the radius of curvature and so the refractive index decrease, and of its path increases steadily, and for the the bending of the waves will be less marked. heights with which we are chiefly concerned It is on this basis that Jouaust explained the this radius appears to lie between about signal -fading effects observed in the France - 5.8 and 6.7 times the radius of the earth. Corsica transmission, particularly near sunset The actual values of this curvature will after a hot, sunny day when heated air was obviously depend upon the pressure and rising from the sea and causing a fluctuation temperature conditions prevailing at the in the deviation produced in the waves point in question, and these may vary con- transmitted. siderably for different parts of the earth's The determination of the curved path of a surface. ray starting from the earth's surface, and In view of the somewhat indefinite nature subject to refraction in the lower atmosphere, of these atmospheric conditions, it would is the inverse of the problem of astronomical seem to be of little value to calculate accu- refraction which was first considered by Lord rately the curved path followed by the Rayleigh". The calculation of the path waves. It will be a sufficient approxima- for the case of a source of radio waves was tion for the limited experimental data so given in Fleming's paper,' to which reference far available if we assume the curvature of has already been made. the ray to be constant and so follow a A more rigid analysis of the problem is circular path. On this assumption the outlined in the appendix to this paper, in possible range of transmission d for a which it is shown that a ray leaving a radio source at an altitude hi, i.e., the distance transmitter in any direction from a point on of the horizon for an observer at such a the earth's surface will follow a path, the height, is given by radius of curvature of which is nearly six d d d) times that of the earth. As the path of the hi- (sec. - zl - m(sec. -I )sec. wave rises in the atmosphere, the density of R nil? the air decreases, and therefore, as seen from When the distance d is less than a few equation (II) in the appendix, the radius of hundred miles, this equation reduces to curvature of The path increases. The follow- ing table gives the results of calculations d=VRh1 Dit made with the aid of equation (II), making na - I use of the definition of the international which is the form given by Jouaust.t Graphs standard atmosphere to obtain values of showing the relation between d and h are average atmospheric conditions. The last two columns give respectively given in Fig. 3 for a few typical values of the radius of ni. diagram curvature of the ray path calculated On this the curve for the in the optical or rectilinear path is reproduced, above manner, and the ratio m of this radius to the radius of the earth. The results * Humphreys " Physics of the Air," 1920, p. 448. are restricted to an altitude of 2,000 metres t Ref. 3, p. 487. January, 1934 8 THE WIRELESS ENGINEER & this referring to a value of ni equal to communication link. It is interesting to infinity. It is seen from this diagram that observe that Jouaust also reports that for the increase in effective range for values of visual observations on a light beacon made m greater than 6 is not large. In the DISTANCE IN MILES case where is also elevated the transmitter 100 125 150 175 2' 25 50 75 to a height 112, the corresponding range is given by the relation :-- - s,o a 2nt zna (1 _ R1i1 m-z Rh, nz-r 80 1' p p cÿ - 5,00 F F The analysis provided in this section takes F F 1 no account of any variation of the refractive .8. index with wavelength. This results from ' -400 the assumptions that the refractive index depends only upon the dielectric constant 1' of the air and that its conductivity plays 3,00 a negligible part at the radio frequencies under consideration. 2. 000 VI. Comparison of Theoretical and Experi- 0 mental Results With the aid of the diagram forming too i Fig. ,;, we are now able to examine the prac- tical results already discussed on the basis of this refraction hypothesis. In the follow- I--- 200 --- ing table a summary of these results is given, DISTANCE IN KILOMETRES and for each case the value of m has been Fig. 3.-Curves giving relation between height deduced to give agreement between the and distance to earth's surface, for a circular theoretical range and that obtained experi- path, of radius m times radius of earth. mentally. In considering these results it must he remembered that the experimental in France on the Atlantic Coast over a period ranges are not definite distances at which the of several years the value of m, connecting SUMMARY OF RESULTS OF RANGE TESTS ON ULTRA SHORT WAVES.
Value Height of of m required Location Distance Trans- Optical to give Wave - Date and of Experi- Covered mitter Receiver Range Distances length Reference. ment. (miles). h1 (ft.). h2 (ft.). (miles). Covered. (metres).
1929 Jouaust .. Nice to 128 2,500 1,700 109 5 5 Corsica. 1931 Beverage Oahu to 190 4,800 1,700 134 2 7.1 and Peterson & Hawaii 8.2 Hansell 1932 Marconi .. Rome to 168 2,460 1,115 107 2 0.57 Sardinia.
received signals were suddenly cut off. The the altitude of observation with the distance disappearance of the signals at the limiting of the beacon, varied from 15 in January to range is naturally a gradual process, and in 7 in August. all the experiments severe signal -fading was Reverting to the above table, it is seen reported at these distances. that in order to explain the results obtained The value of ni. = 5 agrees with that de- in the Hawaiian Islands tests and in Mar- duced by Jouaust for the France -Corsica coni's experiments, on the basis of atmos- EXPERIMENTAL WIRELESS 9 January, 1934 the required value In the case of a non-conductor, this may be pheric refraction alone, the following form containing the This would appear to be some- converted to of In is 2. refractive index a of the material : to explain completely on the what difficult - r basis of the refraction effects discussed above. µ2+2 = Aq The variations in atmospheric conditions i.e. (p. - i) (a. + 1) = Aq met with at different points on the earth's µ2+2 surface are insufficient to account for such value of ni. The variation in In the case of a gas, it is known that the value a small less than one part in a water vapour content from zero to saturation of differs from unity by thousand, and we may thus write : only a small contribution towards provides -I=Ag .. .. (2) a variation in the value of m. A possible a explanation of this apparent discrepancy which is the form of Gladstone and Dale's law for contribution which the refractivity of gases. might be found in the Hence, in order to ascertain the variation of the diffraction effects might make to the received refractive index of air with height above the earth's signal intensity. The diffraction of electric surface, we must know the law connecting the waves around the earth has been studied by density of the atmosphere with altitude, which but the subject may need may be determined in the following manner. G. N. Watson12, If p is the pressure, q the density, T the absolute further consideration in the light of modern temperature, and R the universal gas constant, experimental data obtained on ultra -short these quantities are connected by the well-known wavelengths. The effects of diffraction, how- equation : ever, will decrease as the wavelength is p = RqT .. (3) in reduced, and they are probably insufficient Considering a vertical column of air of unit themselves to explain the fading phenomena cross-section, the equation of equilibrium at any which have been observed in the experiments point is : recorded. If the received signals were due, dp gq .. (4) in equal proportions, to waves arriving by dh then a mere phase diffraction and refraction, where h is the height of the point under con- change of the latter relative to the former sideration and g is the gravitational constant. fading of signals from would account for the Now a maximum down to complete inaudibility. dp l p dq dT of The general conclusion of this section dh Yq dh + T dh paper must therefore be, that while on the eqn. (3) of atmospheric refraction a range From the basis dT of in excess of the optical dp=RT.dq +Rq. communication dh dh or rectilinear path distance can be accounted dh for, there appear to be some discrepancies If we assume T = To - ah which warrant the further investigation of where To is the absolute temperature at the from the theoretical and experi- earth's surface, and a is the rate of decrease of the subject this surface, then mental aspects. temperature with height h above out -Rqa (5) The work described above was carried dh=RT.dhdP as part of the programme of the Radio Research Board and is published by the Combining (4) and (5) we have : permission of the Department of Scientific gq=RT.dh - Rqa and Industrial Research. APPENDIX = R(To - ah) .61-A - Rqa through the Calculation of Path of Waves q(Ra g) Atmosphere dq - dh R(To - ah) (a) Variation of refractive index of air with height above the earth's surrjace. dq_ (Ra -g).dh It can be shown that the dielectric constant K of a g R(To - ah) substance is related to its density q by the equation* Integrating : K-1=Aq (I) .. .. (Ra g) K+2 q - log (To ah) + B log-= Ra - where A is a constant. B is a constant of integration. Theory, 1913, where N. R. Campbell : Modern Electrical p 34 January, 1934 io THE WIRELESS ENGINEER & Inserting the limiting condition that the density (b) Radius of curvature o/ path o/ ray through is 90 at the earth's surface, i.e., for h = o, we get air. Let TP, Fig. 4, represent the path of a ray starting R from the point T log q = slog on the surface of the earth, g Ra (To- ah) radius R, the point I' being at a height h above log To the + log 4o + R Ra surface, where h is very small compared with g Ra /Tp ah\ whence log q- - log - R. 4o Ra l To ) Let l be the length of the normal from and the centre 9=(1-ah)(R -1) of the earth O on the line 90 \ To PQ, which is tangential In order to reduce equation (6) to numerical to the ray path at P. values, it will be convenient to make use of the We then have for any definition of an International Standard Atmos- position of P along the phere as adopted by the Air Ministry for the gradua- ray path, at which the tion of altimetres on a uniform basis*. This refractive index is µ definition assumes that the air is dry and has lµ = C .Fig. 4. uniform composition a .. (8) at all altitudes. The tem- where C is a constant. perature of the air at mean sea level is taken as 15°C, and the barometric height, reduced to o°C, Further, the radius of curvature p of the as 76o mm. of mercury. Under these conditions ray path atthe point P is given by the atmospheric pressure is 1,033 gms. per sq. cm., dh and the density of the air is 0.001226 gms. per c.c. p-Rdl (9) For any altitude up to i i,000 metres the rate of Froin decrease of temperature under these conditions is this, we have o.0065°C. per metre. d cla Inserting the above quantities in = Ii dh equation (6) dl we obtain : fr which, making use of (8), gives q 0.0o65h\4.26 dh 40 1 288 ) p= - Rd Fl _ (1 - 22.6 x to -6h) 4.26 .. (7) dh where h is the height above sea level in metres. -µ dµ In our problem we are, as already stated in the paper, only interested in heights of about 2,000 For air the refractive index is of the order 1.0003, metres or less, and the values of so that in equation (to) µ may be put the density of the unity equal to air at heights within this limit are given in the without appreciable loss of accuracy. following : table dh Hence p = _ dµ Density in gms. but from equations (2) and (6) per c.c. of d d Tempera- A ah dh 490 1 1 Rva Height ture Pressure Air d To Ra ,J To) (metres). (degrees (milli- Dry saturated neglecting terms containing squares and higher Centi- bars). with powers of h grade). Air. water TO p t vapour. = (11) AYoa r g 1)[1 ah g o 15 1,013 0.001 226 0.001219 \h'a - T0(Ra 500 11.75 954 0.001 167 0.001160 - 2)1 1,000 8.5 899 0.001112 0.001 107 Substituting the values used for obtaining the 1,500 5.25 846 0.001058 0.001052 numerical equation (7) together with the value of 2,000 2.0 795 0.001007 0.000993 A = 0.227 for air, we have for h = o 288 P 0.227 X 0.001226 Since the above definition of an international X 0.0065 4.26 standard atmosphere assumed that the air was dry, = 37.2 X 106 metres. the last column of the above table shows the altered = 37,200 kilometres. values of the density at different heights, assuming the air to be saturated with water vapour. From = 5.8 R these figures it will be seen that the change in REFERENCES density of the air with humidity is of the order 1. " Micro Ray Wireless," Electrician, 1931, Vol. 108, of less than one per cent. 509-510. pp. 2. G. Marconi : " Radio Communication by Means of Very See Air Publication, No. 1173 Short Electric Waves," World Radio, 1932, Vol. 15, pp. (1925), H.M. Stationery Office. 1314, 1346-47, 1379-80. EXPERIMENTAL \VIRELESS II January, 1934
:1. R. Jouaust : " Les Ondes Très Courtes," Onde Electrique, level not much higher than the region of reflex 1930, Vol. 9, pp. 5-17. " Some Details Relating to the Propagation of Very Short action. Much of the work performed by policemen, Waves," Proc. I.R.E., 1931, Vol. 19, pp. 479-488. commissionaires, sorters, inspectors, and night 4. H. H. Beverage, H. O. Peterson and C. W. Hansell : " Applica- watchmen is of this type. tion of Frequencies above 20,000 kilocycles to Communica- tion Problems." Proc. I.R.E., 1931,- Vol. 19, pp. 1313- Whatever views may be taken as to the replace- 13:3:3. ment of man by machinery, there is much to be said 1. R. M. Shmakov : " The Experimental Investigation of for the elimination of monotonous labour and for Ultra -Short Waves." A summary of the original Russian paper is given in Experimental Wireless, 1931, Vol. 8, the discouragement of the multiplication of low p. 316. types of brain, and in this respect the photo -electric 6. Radio Research Board, Report for the year 1931, p. 30. cell may be regarded as a eugenic boon. - Wireless World, October 14th, 1932. In valve relay 8. O S T, May, 1932. the fundamental circuits which 9. J. A. Fleming : " On Atmospheric Refraction and its Bearing are described by the authors, the thyratron plays on the Transmission of Electromagnetic Waves Round an important part, since it is capable of controlling the Earth's Surface." Proc. Phys. Soc., 1914, Vol. 26, pp. 318-332. 20 kilowatts with an input signal of only r micro -
10. J. S. McPetrie and R. M. Wilmotte : " Refraction of Electro- watt. The thyratron is at its best on A -C mains magnetic Waves Round the Earth's Surface," Nature, for it resets itself at each cycle and can be phase 1927, Vol. 119, pp. 317-318. controlled to give a graduated output. Relays I I. Lord Rayleigh : " On the Theory of Stellar Scintillation," Phil. Mag., 1893, Vol. 36, pp. 129-142. are always designed to give warning if any part 12. G. N. Watson : " The Diffraction of Electric Waves by the fails, thus if lights are to be switched on at sunset Earth." Proc. Roy. Soc., 1919, 95, pp. 83-99. they will glow automatically upon the breakdown 1:3. E. Picault: "The radio -telephony link with Ultra -Short Waves between the Continent and Corsica." Rev. Gen. of a valve or a battery. d'Electricite. 1932, Vol. 32, pp. 169-572. Counting and timing gear is extensively used for 14. T. Y. Baker : " On the Refraction of Electro -Magnetic purposes Waves in a Spherically Stratified Medium." Phil. 3fag., such as counting newspaper bundles and 1927, Vol. 4, pp. 95:-9811. timing races. The interruption of a beam is used to operate burglar alarms or to open doors or lift gates when anyone approaches. Smoke can be detected by the reduction of illumination of one cell in a balanced circuit. In the hold of a cargo New Book boat where severe conditions would cause rapid deterioration of a cell, the air is pumped up to a Photo-electric Cell Applications. central chamber and there examined. Dangerous By R. C. WALKER and T. M. C. LANCE. gases can be detected by allowing them to alter Pp. 193 (Figs. III.) [Pitman, 1933. Price, the transparency of a chemical indicator. Ss. 6d. In the advertising world, a window display may The photo -electric cell, after a long and eventful be set in motion by light reflected from a hand scientific history, now holds an important place held in front of the window. Or a train may among industrial mechanisms and it is the purpose interrupt a beans of light so that an advertisement of this book to describe and explain the many uses flashes on for ,;o seconds at the side of the track. to which such light-sensitive devices can be put in Road signs are similarly operated by motor -car the commercial world. The authors, who have headlights. In the reproduction of talking films, gained much experience with the General Electric it is interesting to note that infra -red light is used Co., have concentrated on practical applications : to form the beans which is modulated by the sound there is no mathematics and but little physics in track : this is because the flicker of a lamp on A -C the book. This is no drawback, since the theoreti- mains which causes hum in the loud -speaker is cal treatment is already available in the excellent much less pronounced in the infra -red ; also in the book* by Campbell and Ritchie. case of tinted films the colour is practically trans- The first impression produced upon the mind of parent to infra -red so that the sound intensity does the general reader is likely to be one of amaze- not vary. ment at the way in which the scientific toy of ten Many other applications to phototelegraphy, years ago has become established as a reliable television, and scientific instruments are ade- industrial machine. Wherever two objects differ quately described. in shape, size, or colour, one can be taken and the There are a few errors which should be corrected other left ; Wherever a moving object, alive or in the 2nd edition. The footnote to p. 8 defines the inanimate, casts a shadow, gates can be opened, himen in terms of the standard candle and the lux barriers closed, or warning signals set into action. in terms of the Hefner candle, but no country uses It is remarkable how closely the electric eye con- mixed units of this kind. On p. 15 the lumen is nected to a power relay can simulate the mental wrongly used as a unit of illumination. On p. 28 and muscular processes which operate at a low energy is given in microwatts. The differences 3 * Photographic Cells, by N. R. Campbell and D. Ritchie between Figs. and .} should be more explicitly [Pitman 15s.] stated. R. T. B. January, 1934 THE WIRELESS ENGINEER &
The Effective Resistance of Inductance Coils
at Radio Frequency ), An Abstract by B. B. Austin, B.Eng., A.M.I.E.E., of a Paper by S. Butterworth
1.0. --Introduction shown that the best shape of all is a single IN 1926 The Wireless Engineer, then known layer solenoid in which the winding length as Experimental Wireless published a most is equal to one-third of its diameter. The complete treatise by S. .Butterworth on best single layer disc Coil should have a the " Effective Resistance of Inductance Coils v at Radio Frequency." This treatise was ; published in four separate issues and occupied 8 some thirty-two pages. The subject was dealt with very completely and the sources of the º=o various losses carefully analysed. 8 The writer recently wished to make a con- siderable number of H.F. coil calculations 4 and therefore referred to this treatise. b=02+ It soon became apparent however that it 2 D would not be possible to pick out the neces- sary formulae immediately and make the =0'5 L0 1 0 desired calculation. In fact the whole trea- Ì tise had to be carefully read through and notes made of the parts relevant to the B 1111 work in hand ; this required quite a number of hours work. The paper was thus con- s densed into a few pages. kliei` As it is some time since the original paper appeared, it is thought that the re- publication of it in this abstract form will \2 be of interest to readers. No original work D-125 has been done, but in one or two of the =1.50 i ) tables extensions have been made to cover 01 0'2 03 04 05 coil shapes not given and which the writer required. Fig. 1. 2.0.-General winding depth equal to one quarter the The circular Coil being the most general external diameter. For a multi -layer Coil shape in use, consideration is limited to this there is a wide range of choice all of which type of Coil. A multi -sided Coil (i.e., one would be equally efficient. If 5t 3b = D with not less than six sides) may be taken the condition for maximum efficiency is as equal to a circular Coil the diameter of never very greatly departed from. which is the mean between the inscribed and D = External Diam. t = winding depth. circumscribed circles of the polygon. For convenient reference a list of symbols b = winding length. used has been included at the end of the 3.2. Influence of Wire Diameter article. The losses in a Coil at high frequencies may Design Procedure be divided into three parts :- 3.1. Influence of Coil Shape (A) The copper loss which would occur The shape of the Coil has considerable if the wire were straight ; this loss decreases influence on the H.F. resistance. It can be * MS. accepted by the Editor, February, 1933. EXPERIMENTAL WIRELESS 13 January, 1934 with increase of the diameter of the wire. 3.3.-Calculation of Inductance It is denoted in the following by R,. As Coils have always to meet an inductance (B) The increase of copper loss due to the requirement it is necessary to be able to wire being coiled. This loss increases with determine inductance for any Coil shape. increase of wire diameter. It is denoted in I the following by Rh. (C) Dielectric losses. These are not likely I6 to be serious for wavelengths above 300 -- metres if ordinary precautions are taken. Experiments show them to be 30-40 % of the 14 Ilk total loss at 30o metres with coils wound on t solid wood formers, while 2 D with carefully oOy chosen dielectric the loss is from 10-20 % of INKo\SGIII the whole. I'o 1N From (C) above it will be seen that at s 30o metres the calculated value of H.F. 38 resistance may be taken as 8o % of the total. rs From (A) and (B) it will be seen that for a given shape and inductance of Coil, as the D4 b diameter of wire is increased one source SOLEN01 of copper loss will increase and the other S NOLE LAYER -- decrease. There is therefore a certain 32
20
0 1 02 0'3 0 4 05 06 07 16 D 02 04 06 08 1'0 1.2 1.4 b 16 D Fig. 3. t 14 l5=0 Usually this means calculating the number of turns for a pre -determined shape. 12 The inductance of a coil may be written as : L = L0N2 D/i000 .. (i) Lo io where N = number of turns, D = external diam. (cm.), L = inductance in µH. and 8 Lo is the shape factor given by Figs. i and 2. Fig. i has as parameter and Fig. 2 6 t has D as parameter. 4 3.4.-Calculation of Best Wire Diameter. 2 =0'5 (Solid Wire.) D Knowing the Coil shape and number of o 0'2 04 06 06 10 I2 14 turns the best wire diameter must now be D found. Fig. 2. The sources of loss were indicated in paragraph 3.2. It can further be shown diameter of wire at which the rate of that if the wire diameter is chosen so that increase of one loss will equal the rate of R, = Rh for any type of Coil, the least loss decrease of the other, and at this diameter will never be greatly departed from. It the total loss will be a minimum. may sometimes be an advantage to use a B January, 1934 14 THE WIRELESS ENGINEER & wire of slightly less diameter than that given diameter of a single strand. The value of P by the following method. It is however an is slightly modified and is found from the easy matter to calculate the H.F. resistance expression for a gauge or two on either side of that cal- n2S2L 24 P2=Q+ .. D3 (3)
2'0 in which v is a function of " n " and has the
TABLE. 16 VALUES OF THE FUNCTIONS F AND G. S
d = diameter of wire (cm.) ; p = resistivity (cgs units 1 '2 0145
0'25 = frequency cps ; Z =,rd NlY . For copper of resistivity 0'375 o' 0'5 1,700 cgs units dVf = 9.28 or Z = .1078d/f .
0'4 Z. 1 + F. G. Z. 1 + F. G. 0 01 02 03 04 05 0'6 07 t 0.0 1.000 - 5.2 2.114 0.790 D - - - 5.4 2.184 0.826 4. 0.1 1.000 - 5.6 2.254 0.861 Fig. 0.2 1.000 5.8 2.324 0.896 0.3 1.000 Z4/84 6.0 2.394 0.932 0.4 1.000 - - - culated, and take the lowest. The value of 0.6 1.000 0.00097 - - - be found from expression : P can the 0.6 1.001 0.00202 6.2 2.463 0.967 0.7 1.001 0.00373 6.4 2.533 1.003 pz LS2 0.8 1.002 0.00632 6.6 2.603 1.038 .. (2) 0.9 1.003 0.01006 0.8 2.673 1.073 D3 1.0 1.005 0.01519 7.0 2.743 1.109 where S is found from Figs. 3 and 4. The 1.1 1.008 0.02196 7.2 2.813 1.144 1.2 1.011 0.03059 7.4 2.884 1.180 Íz 1.3 1.015 0.04127 7.6 2.954 1.218 value of can now be determined and the 1.4 1.020 0.0541 7.8 3.024 1.251 1.5 1.026 0.0691 8.0 3.094 1.287 value of Pd read off from the curve of Fig. 5. 1.6 1.033 0.0863 8.2 8.185 1.322 The value of " d " is now known. In the 1.7 1.042 0.1055 8.4 3.235 1.357 1.8 1.062 0.1265 8.6 3.306 1.393
following values : 3, 9, 27 . . 3? strands, the number of strands which are to be used is first n = I 3 9 27 large (No. of strands) settled. A o = o 0.9 3.3 10.4 0.4n practically available number of strands is thus always chosen. Formula 4 is now modified and becomes 40 R,=RB+Rh=R{I +F (k K2N2 - äo2 + 4D2 n2d2G} (5) 30 where m=1 n = number of strands. d = diam. of one strand eins. K R = D.C. resistance of stranded con- 20 ductor. do = overall diam. of conductor in mm. = V'.o7n (see following paragraph.) 00 k is a function of n as follows lo :- 3 n = 3 9 27 large k = 1.55 1.84 1.92 2 A slight difficulty occurs in calculating the value of do the overall diameter of the 02 04 0 6 0'8 1'0 12 14 stranded conductors. As a rough approxi- b mation therefore d0 is taken as independent D of d and is given by Fig. 6. do2 = o.o7n . .. .. (6)
The best diameter " d" of an individual 5 strand is then found from formula 2 and Figs. 3 and 4 exactly as for a solid wire. 3.6.-Calculation of H.F. Resistance. (Solid Wire.) The formula for the combined copper 40 losses may be written :
Rc=R3+Rh=R{1- f- F- I- 1(KDd)2G} (4)
Where ` R = D.C. resistance of coil. K 30 I + F & G. are found from the Table. D = External diam. of coil cros. d = Diameter of wire cros. (Not in- cluding insulation.)
N = Number of turns. 20 K = Is found from Figs. 6, 7 and 8. For Coil shapes other than single layer, disc \. or multi -layer, see S. Butterworth's paper, 00 appendix. 3 3.7.-Calculation of H.F. Resistance. 10o M=l 01 02 0 3 04 05 0'6 0'7 (Stranded Wire.) t
As the best type of stranded wire contains Fig. 7. B 2 January, 1934 16 THE WIRELESS ENGINEER &
This is nearly correct for gauges between L = Inductance in microhenries. 36 and 44 S.W.G. La = An inductance factor found from In general the best wire diameter will be Figs. i or 2. slightly less than calculated by paragraph N = Number of turns in coil. 3.5. Therefore, where a Coil is required to P = A factor found from equation 2. cover a range of frequencies, the best wire f = Frequency in cycles per second. diameter should be found for the highest d = Diameter of solid wire or a single frequency, then the condition of minimum strand in cms. except in Fig. 5 resistance will fall inside the range of the where it is in mm. working frequency. Alternatively the H.F. n = Number of wires in a stranded con- 50 ductor. S = Shape factor found from Figs. 3 or 4. a = Factor depending on number of strands. R = D.C. resistance of conductor in ohms. 40 K = Factor given in Figs. 6, 7 or 8. k = Factor in Formula 5 depending on number of strands. d0 = Overall diameter in mm. of stranded conductor (see Formula 6). 30 The Physical Society's Exhibition K THE Twenty-fourth Annual Exhibition of Scientific Instruments and Apparatus, ar- 20 ranged by the Physical Society, will be held on January 9th, loth and r1th, 1934, at the Imperial College of Science and Technology, Imperial Institute Road, South Kensington, S.W.7. The Sessions will be as follows :- Tuesday, January 9th, 1934 (admission by 10 ticket only), 3 p.m. to 6 p.m. and 7 p.m. to io p.m. Wednesday, January loth, 1934 (admission by ticket only), 4 p.m. to 6 p.m. and 7 p.m. to to p.m. Thursday, January rrth, 1934 (admission without ticket), 3 p.m. to 6 p.m. and 7 p.m. 02 04 06 08 1'0 1 2 t4 b to to p.m. D The leading manufacturers of scientific instru- Fig. 8. ments will be exhibiting their latest products in the Trade Section. The Research and Experi- mental Section will contain contributions from most resistance may be found for a gauge or two of the important research laboratories in Great on either side of that calculated and that Britain, and there will be a special sub -section gauge chosen which gives the least resistance devoted to experiments of educational interest. In addition, the work submitted for the Craftsman- over the working range. ship Competition by apprentices and learners will be on view. 3.8.-H.F. Resistance of a Straight Wire Discourses will be delivered each day at 8 p.m For a straight wire the formula becomes as follows :- .. .. January 9th-R. S. Whipple, M.I.E.E., Re= RB=R(I-}-F) (7) F.Inst.P., " The Evolution of the Galvano- where i -{- F is found from the Table. meter." January Toth-J. Guild, A.R.C.S., D.I.C., 3.9.-List of Symbols F.Inst.P., " The Instrumental Side of Colorimetry." D = Diameter of Coil in cms. January Trth-Sir Ambrose Fleming, D.Sc., b = Winding length of coil in cms. F.Inst.P., F.R.S., " The History and Develop- t = Winding depth of coil in cms. ment of the Thermionic Valve." R3 = Copper loss in a straight wire. Members of Institutions and Scientific Societies may obtain tickets from their Secretaries ; tickets Rh = Increase in Copper loss due to coiling may also be obtained direct from the Exhibition the wire. Secretary, 1, Lowther Gardens, Exhibition Road, R = Total Copper loss in ohms. S.W.Q. EXPERIMENTAL WIRELESS 17 January, 1934
The Reduction of Filament -Battery Coupling in Amplifiers* By W. L. Watton, B.Sc., A.R.C.S., D.I.C. (The National Physical Laboratory) SUMMARY.-A frequently unsuspected source of coupling between different stages of valve amplifiers is described. Its nature is investigated, and methods are suggested for reducing the amount of coupling from this cause. Curves are given showing the amount of reduction to be expected from any given arrangement. Introduction experiments now to be described show that, in general, this is not so. THE use of valve amplifiers to increase the sensitivity of physical measure- Preliminary Experiment ments is steadily growing and it would Preliminary experiments had shown that be true to say that, but for the amplification for minimum alternating component of afforded by such amplifiers, certain measure- voltage across the filament the values of the ments now being carried out would be condensers should bear a certain relation to impossible. In the design of high -gain one another. It was found, in fact, that if amplifiers many difficulties arise ; but per- haps the most important of these is the r = the alternating current in the filament undesired coupling between the different CZ stages of the amplifier. Methods for the was eliminated for any value of C, from reduction of the coupling due to valve 0.01 µF. to 2µF. provided that the ratio r inter -electrode capacities and the common was unaltered. It was found, however, that high-tension battery have frequently been the value of r depended upon the circuit constants, and that any adjustment of these described ; but there appears to be little information upon the coupling caused by resulted in a change in the value of r. In following the use of a common low-tension battery order to study this variation, the for filament heating. experiments were carried out. For sim- In the use of complicated wireless receiving plicity, the first experiments were made sets, or when using amplifiers of very high upon diodes. gain, trouble has frequently been experi- Experiments on Diodes enced due to this cause. Bainbridge -Bellt The circuit shown in Fig. 2 was set up. z investigated this inter- action and showed The valve is used as a diode with its grid it could be elimin- and anode connected together. For these that An ated by one of three experiments there was no anode load. methods. Of these, 800 - signal of about 2 V. r.m.s. was injected the first method sug- into the anode circuit of the valve. The gested, namely, that primary winding of the amplifier input of connecting a transformer was connected across the fila- decoupling condenser ment, a large condenser C being inserted to Fig. 1. the low-tension accu- (C2, Fig. i) to the avoid short-circuiting positive end of the filament in addition to mulator. the usual condenser to the negative end, has The sensitivity was greatly increased by proved most useful in practice. was using for filament heating a battery having It normal implicitly assumed in that paper that these an e.m.f. 2 volts higher than the voltage rating of the filament. A resistance, condensers should be equal in value ; but of suitable value, connected in series with double * MS. accepted by the Editor, July, 1933. the battery and filament, served the t Experimental Wireless, January, 1931, p. 18. purpose of reducing the potential difference January, 1934 18 THE WIRELESS ENGINEER & across the filament to the normal value, and Experiments on Triodes of artificially increasing the resistance of the Experiments were now made on triodes, circuit battery across which the alternating for which purpose the arrangement in Fig. 4 potential difference was developed. The was used. A signal of only 0.2 V. r.m.s. amplifier was connected across the filament was impressed on the grid in order to as before. It was shown by experiment that this arrangement did not alter the value of r obtained when a battery of correct voltage was used. The amplifier employed was 2,000 O tuned to 800 -- and had a gain of about 7o d.b. A pair of telephones, connected in its output, served to indicate the best adjustment of C1 and C2. Complete silence in the telephones could not be obtained, but 8 co TO it was possible to detect a change in r of AMPLIFIER about 2 per cent. with a decoupling resistance of 2,000 Sl ; the minimum improving with 6V. higher values of the decoupling resistance. t L.T. Method The method employed was as follows. -H.T. The condenser C1 was fixed and of value Fig. 4 r.00 F. A battery of known voltage was reduce, as far as possible, any effects due to connected to the H.T. the curvature of the valve characteristics. terminals in Fig. 2. The method of operation was the same as The anode current was for the diode experiments. Some experi- noted and the con- ments were also made in which the grid bias denser C2 adjusted to E, was varied instead of the high-tension give minimum signal voltage. It was found, however, that the 02 in the telephones, and effect of a change in E, was exactly the its value was then same as that of a change in Ea of an amount observed. From a equal to times the change in grid bias o knowledge of the H.T. (whereµ is the amplification factor of the 2 mfds battery voltage, the valve at that point of its characteristic). resistance in Accordingly, in the case of triodes, the value TOi the anode AMPLIFIER of r was plotted against the expression (Ea + µE,)-the " lumped voltage "-which will be denoted by E1. A curve very similar to Fig. 3 resulted. H.T. - ANODE VOLTS Further experiments in which the anode load and decoupling Fig. 2. aV. Fig. 3. resistance were sepa- Ef . rately varied showed circuit, and the anode current, the actual that so long as the e P.D. between anode and filament (negative lumped voltage E1 end) Ea, could be calculated. This was was not altered, the E1 repeated for different values of the high- value of r remained un- Fig. 5. tension voltage and the values of r (= C2 changed. In the case when C1 = I) plotted against the corre- of variations of filament voltage of the valve sponding value of Ea. A curve such as that (within necessarily small limits) it was found shown in Fig. 3 was obtained. Similar but that the curve of r against E1, while of the not identical curves were obtained with same type always, was different for different valves of other types, which were chosen to filament voltages. Fig. 5 shows curves for have filaments as diverse as possible. two different filament voltages. EXPERIMENTAL WIRELESS i9 January, 1934
Experiments upon a valve used as an i.e. if C2 P1 oscillator showed that the same curve was C1 P2 as when the valve obtained for this condition value of r obtained represents, upon with the same The was used as an amplifier the hypothesis, the ratio of p, to p2. operating voltages. Discussion of Results An examination of the (r, E1) curves from the diode and triode experiments showed that, for the same valve, and for a fixed filament voltage, the curves were identical. We have, therefore, to explain the nature of the curve and the reason for its dependence upon the filament volts. Both the shape of the curve and its dependence upon the p.d. be explained by the across the filament can Fig. 7. following theory. Consider a valve in which the filament is bridge arrangement can be two parts, both A similar imagined to be divided into if, instead of using two condensers emitting. Considering one obtained of which are C, and C2, the condenser C1 is connected, part, this can be regarded as a complete the negative filament terminal, but valve having a slope not to to the slider of a potentiometer connected resistance p1. Similarly filament. If r1 and r2 are part forms across the valve the other the resistances between the tapping point a valve of slope resist- on the potentiometer and its negative and ance p2, these hypo- then balance is in positive ends respectively, thetical valves being when parallel as far as anode obtained circuits are concerned. ri P1 This is represented in r2 P2 Fig. 6, which includes This arrangement was tried experimentally the essential connec- found to work as predicted by theory. Fig. 2. An and tions of In practice, however, the two -condenser TO AMPLIFIER Fig. 6 examination of was found more convenient. show that it can method Fig. 6. will We can now explain the variation of r be redrawn as in Fig. 7. voltage in the case of an bad minimum with lumped This at once explains the ordinary valve. on p. since the resistance R mentioned i8, Fig. 8 let the horizontal axis represent by a resistance in the In is not compensated distance along the opposite arm. A better minimum can be J Y filament (assumed at a aE negative ter- f obtained by connecting the temperature) i to the slider of a uniform minal of the H.T. battery and let the vertical across the valve º El 1X1 iP potentiometer connected axis represent poten- being suitably adjusted. - DISTANCE + filament, the slider to the ALONG FILAMENT R in parallel tial with respect This has the effect of connecting end of the it has no effect on negative Fig. 8. with the source, where filament. the balance of the bridge. Since in the OY shows the potential at compared with the Then the line experiments R was large any point on the filament. Suppose the of C, and C2 it can be neglected reactance of a diode is given a positive potential Fig. 7 anode for the moment. It will be seen that E f the filament voltage. and that the current Et much less than is a bridge network Then only that portion of the filament Ox, will be a minimum if to the amplifier will be negative with respect to the anode i r and only electrons from that portion will _9cwC2 reach the anode. 9WC1 the filament Pl P2 Hence if, as before, we imagine January, 1934 29 THE WIRELESS ENGINEER & to be in two parts, in this 80 case p2 will be much ;so 1) - J 72 larger than p1. We should w expect r to be very small. U If now we imagine that ó 64 -63'4 (r. 0'2 E1 Elf, the whole of the = 56 filament will be contribut- 5 0 - 52'8 (r=0I.4 ing to the anode current. U 48 469 (r=b'6 Hence p1 and p2 will be of I lj 43'0 the same order of magni- - J 40 0'0 lr=5)'8(r -1u tude, but since at the z positive end of the fila- o 32 ment there will still be no , . 'o r 0'8 24 anode current, is still w0 r=o6` p2 í/,-2UM11111- r . 0'4 larger than p1. general z r=02 In r=0'1. p2 will always be greater than p1 since there will always be a greater differ- 8 ence in potential between the negative o end of the 4 filament and the anode 0.5 10 15 20 2.5 than between the positive VALUE OF 02 CHOSEN RATIO - end and the anode. As IDEAL VALUE OF 02 the anode volts increase, Fig. 1o.-Decoupling experiments. however, this difference will Decoupling resistance 5,000 S2, C1 = 2 µF. become relatively smaller and in the limit, observed facts. The same reasoning applies with infinitely large anode volts, this differ- to valves of different filament ratings, ence will be negligible and p2 will tend to although in this case other factors enter to the value of p1. This is exactly what is prevent quantitative information being given observed in the curves of Fig. 5. which would apply to all filaments. From the explanation above we should The possibility that the variation of expect that the smaller the filament voltage temperature along the filament* might be E f the smaller will he the anode voltage contributing to the phenomenon described required to make p2 approach p1, i.e. for r was not lost sight of. It was found by test to approach unity. This agrees with the that this effect was negligible under the cc conditions of the experi- 1'5 zm ments. w 0 z Practical Application O U This method of decoupling I-10cc has already been used with a great success at the Radio FCC-w W5 Research Station. It was r desired to work an oscil- I- F lator and a high gain amp- 330'5 r r e'a lifier, tuned to the same zI - frequency, r= 1'0 from a common w r- low-tension battery. Trouble O was experienced due to coupling between the oscil- º 0 0.2 lator and the amplifier, which I- 04 06 08 10 12 1'4 16 18 2'0 2 2 2'4 cc VALUE OF 02 CHOSEN was reduced to an imper- RATIO IDEAL VALUE OF C2 * Cf. G. Stead, Fig. 9.-Decoupling Jour. Inst. experiments. Values assumed (for minimum) Elect. Engrs., London, 1921, 59, C1 = 2 µF., R = 5,000 S2, w = 5,000 r/s. 427. EXPERIMENTAL WIRELESS 21 January, 1934 ceptible value when a second decoupling bottom bend of its anode-current/grid-volts condenser of suitable value was used. characteristic, the value of C2 should be Reference has been made on p. 19 to the about one -fifth that of C1. In this con- fact that the balance of the network is nection curves are given in Fig. 9 showing never perfect by reason of the resistance R. the fractional reduction in the alternating The minimum will improve, however, if R is current flowing through filament battery made much larger than the reactance of with such an arrangement. The curves show the condenser C1 (Fig. 7). Happily, this the reduction of current for several fixed condition is that required to be satisfied for ratios of when the valve is used under the greatest decoupling of the high-tension 2 battery, so that, in practice, the minimum conditions such that the best minimum will be very good. Generally the ratio of would be obtained when the ratio was that C2 to C1 must be obtained from an experi- plotted in the x-axis. The same results are ment, but it is not always essential that the plotted on a decibel scale in Fig. io. condensers C1 and C2 should be in exactly the correct ratio. Indeed, most in cases, the Acknowledgment introduction of the second condenser C2 of a value about four -fifths that of C1 will This work arose in connection with the reduce common filament battery coupling programme of the Radio Research Board to an amount which is negligible. In the and the present note is published by per- case where the valve is used with the grid mission of the Department of Scientific and so negative that the valve is working at the Industrial Research.
Background Noise in Amplifiers The Spontaneous Action Due to Thermal Agitation and Schrott Effects Paper by Messrs. E. B. Moullin, M.A., A.M.I.E.E., and H. W. M. Ellis, B.A., Grad.I.E.E., read before the Wireless Section I.E.E. on 6th December, 1933
Abstract other, so that the net effect is zero. At any instant THE paper deals with the spontaneous excita- of time, however, there may well be some net tion of any oscillatory system by random current in any element. impulses, and, in particular, the spontaneous Applying this reasoning to an oscillatory (LCR) excitation of a circuit by the chaotic movement of circuit, it is shown that the free electrons within it. The paper first dis- LI2 = CV2 = kt cusses Brownian movements, stating the well- known physical quantity known as Boltzman's Where k is Boltzman's constant. If the condenser constant, IT' = kt, where k is Boltzman's constant plates are connected to the input of a valve amplifier = 1.372 X IV -16 erg per degree C. In 1900 the voltage will be magnified sufficiently to produce Drude showed that many of the observed facts of an audible or visual effect. In the case of an electrical conduction in metals could be explained acoustic amplifier containing no resonant circuit by supposing the metal to contain a large number of radio frequency and of uniform response up to, of free electrons moving about among the mole- say, 5o kc/sec., the dominant portion of the noise cular interspaces. We thus picture that every- will be due to the circuit attached to the input where in a conductor there is a " gas " of free grid, because this receives the full magnification electrons which are in frequent collision with the of the amplifier. If this circuit has a natural molecules of the metal. During the flight -time frequency well within the acoustic range, the mean - between two collisions the moving electron pro- square response of a telephone will be the same as duces a magnetic field and hence is, for such time, that resulting from applying an audio -frequency equivalent to a steady current in the element of harmonic voltage V such that V2 = kt/C. The circuit represented by its free path. In any finite character of the noise changes as the natural fre- element of circuit there are on the average as many quency of the circuit is increased. It is always a electrons moving in any one direction as in any scratchy, hissing noise, but the general level of January, 1934 22 THE WIRELESS ENGINEER &
pitch rises with the frequency of the circuit. When paper, Curve A of Fig. 9 showing galvanometer the frequency of the circuit approaches the limit deflection against frequency, again confirming of audibility the noise -level will decrease, but the the relation stated above. response of a thermo-galvanometer would continue The second part of the paper discusses the to increase. Schrott effect which is due to the passage and When the circuit is lightly damped the noise - arirval of individual electrons from filament to level will not be measurably reduced if the amplifier anode. As a result,. there is a p.d. across the characteristic is altered to that of a band-pass anode -circuit impedance due to the arrival of system giving uniform response between 3- po and discrete electrons and additional to that resulting 2 po. If the amplifier has a narrow band -width from thermal agitation. round the natural frequency of the circuit, the From expressions derived for the value of the noise level will be reduced considerably. The Schrott effect, it is shown that the Schrott voltage total response of a resonant circuit is independent is directly proportional to the charge of an electron of its resistance, but the character of the noise is and also to the mean anode current. It is shown altered because increasing the resistance increases in the paper that the agitation voltage in the circuit the relative amplitude of the lower component is negligible compared with the Schrott voltage frequencies. in the same circuit. When a triode is working The expressions given above were subjected to with full space -charge limitations, however, the experimental confirmation verifying the appli- Schrott voltage is usually small compared with the cation of Boltzman's constant. A six -stage re- voltage in the same circuit due to the thermal - sistance -coupled amplifier, elaborately screened, agitation effect which occurs in the circuit connected giving an overall amplification of 2 X roe, was between the grid and filament. If a given potential applied to a power stage containing a thermo- is maintained at the anode and the filament current galvanometer. ioo units of galvanometer de- is increased from a low value up to the rated con- flection was produced by an applied p.d. of about ditions, it is found that the Schrott effect rises and then falls off to a limiting value, which obtains when the valve is working in rated 2.05µV conditions. The paper then proceeds to develop expressions 30 for the Schrott voltage in work- ing conditions, from which it appears that the Schrott effect is likely to be more im- portant than that of thermal agitation. The signal/noise ratio can be improved by increasing the mutual con- ductance of valves provided e that the increase is not accompanied by an increased anode current. Lastly, the paper discusses the interaction of spontaneous oscillations with a carrier voltage, i.e., as an effective modulation. From the analysis which is derived it appears that the thermal -agitation voltage in the input circuit produces a negligible effect in 0 0.0025 0.005 00075 0.001 combination with the carrier (,ig51 as compared with the effect of the Schrott voltage in the FIG. 3. first anode circuit. The authors are unable, however, 3 volts. A resonant circuit consisting of o.3 H to say whether this accords with experience. and a capacity, variable in steps from i,000 to The signal/noise ratio can be improved by 10,000 µµF, was arranged in a screened case, the increasing the radio -frequency magnification condenser terminals of the condenser being con- and will tend to a value which is independent of nected to the input grid. Fig. 3 shows galvano- the magnification and depends chiefly on the meter deflection plotted against 1/C. The bend Schrott effect in the anode circuit of the first h.f. is due to the characteristic of the amplifier falling valve. It is suggested that the most effective way at high frequencies, and it is shown in the paper to improve the ratio is to modify the construction that correction for this gives the linear relation of screened -grid valves so as to provide greater illustrated. The paper also describes further values of mutual conductance with decreased measurements from which the value of Boltzman's anode current. It is also suggested that the constant is carefully determined. random phase of spontaneous oscillation will help The effect of temperature is also shown in the to make the noise voltage much less when rectifica - EXPERIMENTAL WIRELESS 23 January, 1934 tion is by a linear detector. Until such an investiga- Ballantyne tracing a proportion of noise to ionisa- tion has been carried out it is useless to discuss the tion effects. He described a comparative method of noise measurement which was in use for the testing of receivers, and suggested that the problem of linear detection was less difficult than the 20 authors indicated. MR. F. NANCARROW did not agree with the authors' estimate of the relative practical im- portance of the Schrott and thermal -agitation effects. In his experience most noise originated o in the input circuit and it was normal to find the noise -level reduced by 6 to io db by detuning ,., 15 v the first circuit. Similar views were expressed by the next two speakers, MR. BLUMLEIN and MR. o A. MUMFORD. v B -cs After the authors had briefly replied to the dis- cussion, the meeting terminated with a vote of v thanks proposed by the chairman, Mr. G. Shearing, 10 O.B.E. 9 o,..- ...-c > B.B.C. Checking Station
`..3
Base -line
-200 0 200 900 Temperature, `C. FIG. 9. signal/noise ratio in a superheterodyne receiver or in an ultra -selective tone -corrected receiver. Discussion DR. RAVLINSON, in opening the discussion, criticised the mechanical analogy of random motion which the authors used in the paper. He queried the conclusions about reduction of noise with band -width and said that he had not found this in experience. He also sought information on the increase of background noise which occurs when a separate -heterodyne oscillator is switched in. MR. B. S. GOSSLING referred to the fundamental manner in which the work had begun, and illus- trated a theorem by Dr. N. R. Campbell, giving an expression for the distribution of random pheno- mena. MR. B. WILLIAMS suggested a modified form for the Schrott voltage applied to the grid of a valve, Although primarily intended for checking the quoting measurements on high -gain amplifiers wavelengths of the European broadcasting which gave good agreement with the expression stations, the Tatsfield receiving station of the derived. B.B.C. also covers the short-wave bands. The MR. HIRSCHMAN referred to the work of Llewellyn wavemeter in the photograph has a range of mentioned in the paper and to recent work of between Io and loo metres. January, 1934 THE WIRELESS ENGINEER & Correspondence Letters of technical interest are always welcome. In publishing such communications the Editors do not necessarily endorse any technical or general statements which they may contain. Do Transmitting Stations Get Tired ? However unimportant, or even commendable, To the Editor, The Wireless Engineer such a state of affairs may be in literary circles, SIR-In the October 27th issue of The Wireless in the technical press the situation is much less World, "D. Exer," a contributor, refers to the desirable. The word in question is " demodula- tion," which apparently has one meaning in mystery of stations that lose power ; within a few weeks or months of their opening, signals fade America and another in Great Britain. slowly away until they can no longer be heard, or As used in Great Britain, demodulation means a heard only with difficulty. decrease in depth of modulation, the opposite to This is a phenomenon with which I have been rise in modulation. A typical example of the use familiar for twenty years. It affects all types of of the word occurs in E. V. Appleton and D. radio stations-spark, C.W., telegraph or broad- Boohariwalla, " The Mutual Interference of Wire- casting, on any wavelength. less Signals in Simultaneous Detection," The Wire- } The initial range of the station when first opened, slowly decreases after a less Engineer, page 137, March, 1932 : few months, and is never regained at any subsequent " If strong and weak signals of carrier fre- date unless major changes are made in equipment. quency intensities S and W respectively are In the July i4th, 1926, issue of The Wireless World, simultaneously received with a linear detector, under the heading : " Do Transmitting Stations the modulation of the weak signal is reduced Suffer from Fatigue ? " I described my observations to # . . . in detail. I quote from that letter : a fraction of its original value. The " There are only S two possible variables in a demodulation influence of the weak signal on the transmitting station which cannot be closely checked strong signal is . . . small." up. One is the surface condition of the aerial wire, and the other is the earth connection and the con- On page 150 of the same issue of The Wireless dition of the surrounding soil. . Engineer, P. G. Davidson says in a letter to the " As regards the earth connection, ordinary soil is editor : not accustomed to having umpteen kilowatts of " It is to be noted that demodulation of the current pumped steadily into it. After a few weeks interfering transmission of such has, in a sense, taken treatment, what sort of electrolytic actions place, for only one of the necessary three com- take place, and in what way does that soil become decomposed ponents has survived. or altered in character in the imme- " I suggest that the error Dr. Robinson makes diate vicinity of the earth plates ? Has anybody ever investigated lies in the idea that the whole process of de- that point ? " modulation is effected by the detector." I don't think the surface condition of the aerial makes any material difference, but I am still curious A large number of other instances of the use of about the earth connection-the only part of a the word with this meaning have occurred in the transmitter which has not, to my knowledge, been British radio journals since 1928. closely investigated. It is perhaps significant that, In America, on the other hand, demodulation is during the course of many years of close association used to mean the reverse of modulation, and is with ship transmitters as a seagoing operator, I therefore equivalent to detection. This definition have never yet known a ship transmitter whose range of the word is given by Brainerd and Mcllwain, fell off after the first few weeks or months of operation. " High Frequency Alternating Currents," John Provided that no major changes are made in the Wiley and Sons, New York, page 2 : installation, and provided also that the installation " When is efficiently maintained, this modulated signal reaches its its range remains constant destination, its frequency must be lowered to its year after year. It is very difficult, of course, for an observer ashore original frequency in order that the original to check the range of a constantly sound may be reproduced by the receiver. This moving ship ; that can only be done accurately by the ship's operators. process is termed detection, or demodulation." The important point is that a ship's earth And even J. A. Fleming in " The Propagation of connection is constantly being renewed. Electric Currents," Constable and Co., 1927, Several other correspondents agreed with my page 399, says : observations in 1926, but still, nearly eight years later, the " In the plate circuits of these last valves we mystery apparently remains unsolved. have coupled ordinary telephone receivers, May I commend this problem to the serious atten- which are tion of adequately equipped acted upon by the voice currents research organisations ? disentangled by these demodulating valves from A. DINSDALE. respective New York. their carrier currents." Fleming almost certainly took this use of the What is Demodulation? word from the original article describing Bell System To the Editor, The Wireless developments in carrier telephony, " Carrier Engineer Current Telephony and Telegraphy," by Colpitts SIR,-A rather interesting case of a word with and Blackwell, Trans. A.I.E.E., Vol. XL., pp. two meanings has recently become of some moment. 205-296, 1921. Probably the word was coined EXPERIMENTAL WIRELESS 25 January, 1934 by Bell System engineers for this use, and has It is difficult, indeed impossible, to define a gradually spread outside of that organisation. " stage " without reference to highly technical Apparently the word appeared in British literature concepts and without recourse to scientific language. some years later, independently of its employment Further, I consider that, for the purposes of classifi- in America, with the difference in meaning noted cation, certain stages of an instrument should be above. In Canada, as a result, we have been omitted in the description. blessed with both meanings. I would exclude any stage which acts purely The exi..ting situation clearly should not con- as a rectifying stage. That is to say, I would tinue. It remains then for the technical press exclude the power rectifying stage in A.C. mains to agree to drop one or the other usage. The operated instruments and H.F. rectifying stages present writer votes emphatically to retain the (which might be called demodulating stages, meaning of detection. Demodulation here has its but for the unfortunate misuse of this word). logical meaning as related to modulation. This Leaky -grid, power -grid and anode -bend rectifying usage of the word is widespread in both commercial stages would be included, however, for they are and technical fields. At the same time, the word not rectifying stages only : the modulation of the fills a real need. " Detection " is a word of which signal undergoes amplification in all these three the literal meaning and the technical meaning have cases, subsequent to rectification. The only now nothing in common, and is merely a relic of H.F. rectifiers to be excluded therefore, are the pre -valve days. It merits only an early oblivion. diode thermionic valve rectifier, and the metal The fact that the British tendency has been to H.F. rectifier, where the signal " amplification " substitute so unsuitable a word as " rectification " is less than unity. I would also exclude the local - for " detection " strengthens this point. oscillator stage of a superheterodyne receiver, Demodulation, as used to mean decrease in depth but would include the " mixer" or " frequency - of modulation, on the other hand, has little to changing " stage. recommend it. So far as the writer is aware, the I would further exclude any rectifying circuits word has been thus used only in connection with and thermionic valves (or metal rectifiers) employed the phenomena involved in the simultaneous for automatic gain control purposes, and would detection of two modulated waves. " Masking " reckon, also, every push-pull stage (Class A, or " masking effect " seem excellent alternatives. Class B, or Q.P.P.), and also valves operated in In any case, it seems highly undesirable to coin a parallel, as a single stage. specific technical word to describe an effect re- Thus, an A.C. mains operated instrument, latively so unimportant, which is so readily de- comprising two screened -grid H.F. stages, power- scribed by the use of ordinary terms. grid detector, pentode power -output stage, and Montreal, Canada. C. B. FISHER. thermionic valve power -rectifier, would be classed -stage J as a four instrument. If the detector valve were replaced by a double -diode triode valve, and Valves or Stages ? an automatic gain control circuit added, the To the Editor, The Wireless Engineer. instrument would still be a four -stage instrument. Neither the separation of the functions of demodula- SIR,-From the time when the thermionic tion and amplification at modulation frequency, valve was first used in a radio instrument it has nor the use of automatic gain control, been the practice of radio engineers to constitutes classify the introduction of an additional " stage " in the receivers and amplifiers by the number of " valves " interpretation of the word. employed. was a mode true This satisfactory of classi- I should define a " stage," therefore, in the fication as long as power was derived from batteries, following terms while one valve was :- and used for one purpose A radio receiver or gramophone amplifier has only. n stages when it incorporates n valve -circuits, With the use of the power rectifier valve for excluding the circuits of power rectifiers, thermionic- supplying operating power a difficulty arose as diode or metal rectifiers, used for H.F. rectification to whether that valve should be included in the receiver only or for automatic gain control purposes, and description for the purposes of classification, local oscillator valve -circuits in superheterodyne and, quite wisely, most engineers and physicists instruments : groups of valves in a push-pull decided that it should be excluded. It is well- circuit (Class A, Class B, and Q.P.P.), and known that manufacturers have, in the past two valves years, connected in parallel, to be reckoned as one stage or three included this rectifier in the classi- only. W. F. FLOYD, fication-solely for advertising reasons, however. Technical Editor The Music From time to time much has been written on Seller & Radio Music Trader. this matter in The Wireless World and elsewhere. London, W.C.r. The latest development (which has evoked this letter) is an announcement by E. K. Cole, Ltd., that their instruments are now classified according The Beat Frequency Oscillator to the number of " stages " they incorporate. A To the Editor, The Wireless Engineer " stage " is defined by them as representing SIR,-Arising from the article on the above subject roughly " the amount of work done by a single in the September issue of this Journal, the following valve in the days before ` complications set in '." points may be worth noting. They occurred Such a move has been long overdue, and it is during the writer's investigation of the problem to be hoped that other manufacturers will abandon under Professor Fortescue at the City and Guilds the " number of valves " designation. A " stage " College. In the experimental setting up of the should be defined with scientific accuracy, however. best oscillator, owing to uniform response being 26 THE WIRELESS ENGINEER & required over rather high beat frequencies (2o,000 effected by passing (say) the weaker signal through to 40,000 c/sec.), due regard had to be paid to the a single tuned circuit. exact principles involved. With the above precautions, it may be assumed Two high -frequency voltages that a range of beat frequencies of constant ampli- vi cos wit tude can be produced with as small a percentage of and 02 cos w2t harmonics as may be desired. The kind of linear detector and low pass filter circuit following it are simultaneously applied to the detector. The need a little consideration. resultant input may be written* Diode detection (with positive volts on the grid) would give a very good linear characteristic vl cos wit -1- 02 cos (wi + 0)2 wi)t under - correct conditions, but is not recommended owing = (y, + y2 cos w2 - wit) cos wit - (v2 sin w2 - wit) to lack of sensitivity. Anode -bend detection is sin wit perferable, and by means of a high resistance in / the anode circuit the characteristic may be made =-- "V vit -}- 0,2 + 20102 cos COI - w2t, cos (wit + 111) linear. From a number of valves tested, an AC/P with ,00,000 Q as the anode resistance was -1 02 sin £02 - wit where 1/, = tan found most suitable for this purpose and for accept- vi -{- V2 cos 012 - wit ance of the large signal vi without grid current. = V cos (wit + e The bias to be applied is - 25 V. The beat response for a square -law detector is 1'0 proportional to 172, i.e., to both vi and v2 (20,02), and since one of these is to be variable it does not suit our purpose from the point of view of constancy 08 of output over the best frequency range. For a linear detector, however, the response is proportional to V, i.e., to o-6 la Fig. I.-Anode 11412 + 022(/1 + cos w2 - w1 current -grid volt - e 120+2022 0 4 age characteristic ¡2viv2 cos w2 of AC/P valve (i)( - 2) - witl2 , I + 1\ /1 T . . with anode resist- I . 2 1 ance = 100,000 which contains the full range of harmonics. If, 52 and H.T. however, vi> >02, we may neglect v22 compared battery= 120 with vie, andwe get response is proportional to volts. 16 14 12 10 8 8 4 2 0 v2 1 011/ I - cos w2 col . t f -Vg vl - / As regards the filter, originally the writer, too, as i.e. (vi + 02 cos w2 - wit) did the authors of the September article, decided to Thus the beat note output contains harmonics have a properly terminated network designed to which can be made as small as we please by re- cut off above the highest beat frequency required. duction of 02 compared with vi. The pure beat Calculation gives L of the order of a henry, depending note output is then proportional to v2, the weak upon the terminating impedances and the cut-off h.f. signal, but is independent of vi, the strong h.f. frequency. It is not easy to construct such signal. Hence, the weak signal is provided by the a large -valued inductance without introducing fixed oscillator. sufficient self -capacity to upset the original design. In practice, considerable care must be taken Of course, a more complicated network in which to see that 02 (measured at the rectifier terminals) the inductance is tuned could be worked out, but remains fixed when the condenser belonging to the this is undesirable. On second thoughts, it is strong oscillator is varied. This must be tested seen that a filter to cut off at the upper beat fre- with the strong oscillator off (say by disconnecting quency is not required, since, having followed out its filament supply). More often then not, owing the above directions, no harmonics of the beat to the comparatively large coils associated with the frequency are present. Instead, only the signal coupling of a large signal to the detector, it will be high frequencies are to be cut off, and in this case found that v2 is affected. To remedy this, a a much lower value of L (order of mH.) is required. periodic, or rather untuned, coupling is essential. This is easy to construct without any upsetting Failure to observe this practical point may result in self -capacities. considerable annoyance in accounting for un- Much of the bother connected with constant - expected results. amplitude, variable -frequency heterodyne oscillators As pointed out by Kirket, a further necessary may be avoided by paying due consideration to requirement for the purity of the beat wave is the above points. M. SLAFFER, B.Sc. that one of the h.f. signals is pure. Under these conditions we cannot get harmonics of the funda- Distortion in Public Address Loud Speakers mental beat wave. This may conveniently be To the Editor, The Wireless Engineer
* Butterworth, E.W., 1929, p. 62o, eqns. (1) to (5). SiR,-In the design of apparatus for radio and t Kirke, E.W., 1927, p. 68. acoustical purposes care is required to reduce alien EXPERIMENTAL WIRELESS 27 January, 1934 frequencies to a negligible amount. There is no e being the particle amplitude at the variable truly linear characteristic in practice. When the abscissa (x -- C). For infinitesimal pressures amplitude, whether electrical or mechanical, ex- C«I, so e' << I and (2) degenerates to ceeds a certain limit, alien frequencies become troublesome. It is usual to tacitly assume that if a e" + ße' - = o (3) diaphragm vibrates sinusoidally, the sound is everywhere of this waveform, i.e., the medium (air) For sinusoidal motion = - .2e, so (3) can be itself acts linearly. This is a natural assumption, written since the theory of sound is based on infinitesimal .. pressures, which are accordingly inaudible. During e"+ßC'+k2C=o (4) the passage of a wave the air pressure varies, but where k = w/c. The well-known exponential horn the density of the medium is (in theory) assumed equation has this form, but the velocity potential ,h constant. Near a powerful source, the density at is used in place of e. In this case and are the wave crests exceeds that at the troughs. linearly related. Consequently the former travel more rapidly than London. N. W. MCLACHLAN. the latter and tend to overtake them. Thus the wave alters in shape as it progresses, its slope tending to become perpendicular to the direction of transmission. This aspect of plane wave propaga- Book Review tion is fully discussed in Rayleigh's Sound (vol. 2, section 249 et seq., 2894). The fact that no change Sub -Harmonics in Forced Oscillations in Dissipative in waveform has been reported in loud speaker Systems work is doubtless due to the use of waves which By P. O. PEDERSEN. 86 pp. G.E.G. Gad., expand from the source outwards. In a plane wave Copenhagen. 8 kr. there is no expansion, the only correcting influence Professor Pedersen is the Principal of the Royal being that of viscosity which is very small. Technical College in Copenhagen and is well known Some time ago in studying the theory of horns, to older radio engineers as the fellow -pioneer with I computed throat pressures of the order 1/25th Poulsen in the development of the arc generator. atmosphere with a public address speaker. It was Six years ago he published a comprehensive volume thought that alien frequencies might occur in the on the propagation of radio waves. The mono- output beyond the mouth. I have been unable to graph under review shows the same mathematical test this experimentally, but an analytical, investi- thoroughness. Although there is a section en- gation by S. Goldstein and myself indicates that, titled " experimental investigations," the book is provided the throat pressure does not exceed a mainly a mathematical investigation of the pro- certain large value, expansion of the waves prevents perties which the coefficients of the differential the alien frequencies from being large relative to equations must possess in order that an applied the main frequency. force of a given frequency may set up oscillations The general equation for the propagation of of a half or quarter of that frequency. This is sound waves of finite amplitude in a straight horn an important question in connection with loud of infinite length, having any cross-section (similar speakers and one on which letters have appeared throughout the length), can be shown to be in our correspondence columns in the past. The conclusion arrived at by Prof. Pedersen is ( +ß'c2 X f in systems with one degree of freedom second = o . . (I) that e+X(1+C') sub -harmonics may occur, but that with two where = particle amplitude at any axial distance degrees of freedom the second sub -harmonic may e set up a fourth sub -harmonic. This can arise with x,-}- from the throat ; a a loud speaker diaphragm which must be regarded =c z z A as possessing several degrees of freedom. This . C_ Utz , X= xz A 1 fourth sub -harmonic needs very careful tuning Area at (x for its production and is destroyed by very slight changes, even a change in the humidity of the room Area at x cc)x being enough to prevent it-which is very fortunate. y = 1.42 for air ; c = velocity of sound. Second sub -harmonics are, however, of common be given special For an exponential horn A2 = A 0ef4s + 0, A 1= A 013.,so occurrence and should attention in acoustics but also in physical x = epe and x' = ßeP e'. Substituting these not only technical quantities in (I) we obtain the differential equation and physiological acoustics. of an exponential horn when the sound pressure This is a book which can be recommended to is finite. Thus those who are interested in the mathematical treat- ment of this important question. 5')r+1e(r-1)F4 pptt tt (I + It is written in English-and very good English. eS + YS (1 + S') c2 -0 (2) G. W. O. H. January, 1934 28 THE WIRELESS ENGINEER & Abstracts and References Compiled by the Radio Research Board and reproduced by arrangement with the Department of Scientific and Industrial Research
PAGE PAGE Propagation of Waves .. .. 28 Directional Wireless 41 Atmospherics and Atmospheric Acoustics and Audio -Frequencies.. 42 Electricity .. 31 Phototelegraphy and Television .. 44 Properties of Circuits 33 Measurements and Standards .. 46 Transmission .. .. 33 Subsidiary Apparatus and Materials 50 Reception .. .. 34 Stations, Design and Operation .. 53 Aerials and Aerial Systems 37 General Physical Articles .. 53 Valves and Thermionics .. 39 Miscellaneous .. .. 54
PROPAGATION OF WAVES mentioned in 1933 Abstracts, pp. 494 and 558-559 ON Two METHODS OF IONOSPHERIC INVESTIGATION. cf. also Schafer and Goodall, p. 558. V. (Proc. -E. Appleton. Phys. Soc., RADIO OBSERVATIONS DURING THE [Second] INTER- Ist Sept., 1933, Vol. 45, 5, No. Part 25o, NATIONAL POLAR YEAR (1932-3).-E. V. pp. 673-688.) Appleton. (World -Radio, The two methods of ionospheric investigation, loth and i7th Nov., 1933, Vol. 17, Nos. 433 and 434, results of which are described in this paper, are 613-614 and 654-655.) (i) a rapid series of measurements of the equivalent pp. The substance of the R.I. discourse. See also path P' of atmospheric waves for different fre- Nature, 4th Nov., 1933, Vol. 132, quencies f and the construction therefrom of a pp. 703-704. A preliminary account was dealt with in 1933 (P', f) curve, and (2) a series of (P', t [time]) curves Abstracts, p. for different frequencies over the period when each 613. frequency becomes critical for the extraordinary IONISATION OF THE IONOSPHERE.-K. A. Norton. wave for F layer ; this gives a curve showing the (Nature, 28th Oct., 1933, Vol. 132, p. 676.) connection between time and the maximum number This letter supports the suggestion of Tonks of electrons per cc in F layer. From the 'examples (1933 Abstracts, p. 559) that the relation between chosen to illustrate the methods " the following ionisation density N and critical frequency f should deductions and measurements concerning iono- mf 2 ,mf spheric characteristics are made Magneto - be N = rather than 3 Z . The writer :-(a) e2 2 ez ionic double refraction is caused region ; by E this finds that each electron moves through a distance shows, as was previously demonstrated in the case very large compared to the of region F, free electrons average electron spacing that are the effective in a time short compared with that of the radio electrical agents. (b) For daytime conditions, and wave, so that the space average field is applicable more frequently in summer than in winter, evidence £2 of the existence of a protuberance or ' ledge ' on to the problem, giving the value N = "le region F is found, which most probably indicates that under direct solar influence this region is IONISATION DENSITY AND CRITICAL FREQUENCY.- sometimes composite. Evidence of the existence L. Tonks. (Nature, 4th Nov., 1933, Vol. 132, of ionisation between regions E and F (' inter- p. 710-71I.) mediate region ') has also occasionally been This letter supports a previous letter of the writer obtained at noon, so that the whole ionospheric (see preceding abstract). The writer considers an configuration may be regarded as a composite elastic force of the form - ar acting on a bound structure of four components. From the point of electron, which he replaces by a Coulomb force due view of practical radio communication, however, to the ion when the electron is regarded as free. it is sufficient to regard the ionosphere as divisible He calculates this by supposing the positive ion to into two main regions, E and F, but where it is be uniformly distributed throughout a sphere of necessary to consider further the ionospheric fine structure it is proposed to name the four com- volume and finds a restoring force - 4 . Ne,r 3 ponents, at successive increasing equivalent heights, to replace the - ar used for the bound electron. regions E', Eta, FI and Fn. Usually only regions He thus arrives at the conclusion that the polarisa- E1 of and F" are importance." The term Region e tion term disappears and that the valid formula is is suggested for the abnormal ionised region pro- as stated. duced by corpuscles at or slightly below the height of the normal Region E due to ultra-violet light. SHORT WAVE PROPAGATION IN THE EARTH'S The occurrence of Region e has been found by MAGNETIC FIELD [Theoretical Investigation]. Naismith and the author to be correlated either -K. Försterling and H. Lassen. (Ann. der with magnetic storms or with thunderstorms. The Physik, 1933, Series 5, Vol. 18, No. i, deductions from the curves obtained, of which pp. 26-6o.) examples are given in this paper, have already been The writers give the well-known investigation on EXPERIMENTAL WIRELESS 29 January, 1934 classical lines of the propagation of a plane homo- AUTOMATIC RECORDING OF THE HEAVISIDE LAYER geneous wave in a homogeneous ionised gas, for an [Heights and Echo Amplitudes].-H. E. arbitrary direction of propagation relative to an Hohmann and K. Kreielsheimel. (E.N.T., external magnetic field. They neglect the Lorentz October, 1933, Vol. Io, No. 1o, pp. 392-396.) polarisation term : " since the free charges (ions, Description of the Heinrich -Hertz Institute electrons) are irregularly distributed and their equipment used for the Polar Year observations in distribution is unchanged by the field of the wave, Norway. The pulse transmission is controlled by they exert on the average no force on one another. a magneto -ignition -system rotating cam driven by Since, further, the electrical polarisation of the gas a synchronous motor ; at each rotation of the cam molecules has no effect, owing to the small density, the high negative grid bias blocking the oscillator the total electric force acting on an electron is is removed, so that the oscillator is in action for 3/Io 000 sec. at intervals of 1/25 sec. At the e(E I (v. H))" . They find expressions for the recording equipment another cam controls the refractive indices of the medium and discuss them discharging of the time-base circuit capacity : by for waves of length less than 200 m, neglecting means of the " spark advance/retard " mechanism an accurate and phase regulation is the effect of collisional friction ; the positions of convenient the zeros and infinities of the refractive index µ possible : thus in the record of Fig. 5, between the are found. The effect of a small amount of friction ist and 2nd hour this adjustment was made and in the neighbourhood of the infinities is considered. the ground -wave track brought into the picture. A dispersion curve is given for A = 84 m, angle a This record was a straightforward echo -time record, between direction of propagation and magnetic using the " negative " process in which the signi- ficant features are the white tracks produced by field = 65°. Curves are also given showing µ2 as a function of height above the ground for three the gaps " between the feet " (as it were) of the different laws of variation of ionisation with height, signal peaks. for a = 25°, ñ = 84 m. The polarisations corre- Later, however, the records were made to include sponding to the two values ofµ are considered. not only the echo -time (i.e. layer -height) indications, The effect of collisional friction is neglected and the but also echo -amplitude indications. This was polarisation of the waves at the earth's surface, accomplished by inclining the co-ordinate system assumed to be the limiting value given by N --s o, of the fluorescent screen at a fixed angle (e.g. 30°) to the time axis of the recorder. white is found to be circular : the sense of rotation is The such that, for downcoming waves in the northern " negative " tracks are still made, to represent the hemisphere, the slower wave is of left-handed times of the signals and echoes ; but, in_ addition polarisation. Reflection and refraction at a plane to these, the bright summits of the deflections boundary are considered and determinantal ex- (where the ray has to reverse its direction) are now pressions for the reflected and refracted waves " positively " projected on to the moving strip in obtained. These are discussed in various degenerate the form of dark lines. The distance between such cases, including those of propagation transverse a line and the middle of the corresponding white and longitudinal to the field, of electron density track, measured at the correct angle (Fig. 6) gives tending to zero, of frequency tending to infinity, a measure of the signal amplitude. Fig. 7 is an and of the two media differing only slightly from example of such a double record, taken in Norway. one another. Circular polarisation of all waves, magnetic field, are also MEASUREMENTS OF THE HEIGHT OF THE KENNELLY- and a vanishingly small HEAVISIDE LAYER.-G. Elias, C. G. A. is found J. assumed. Under these conditions it that von Lindern and G. de Vries. of of the two polarised (E.N.T., no splitting one circularly October, 1933, Vol. 1o, IO, pp. 400-404.) waves takes place on crossing the plane boundary, No. small. Shorter version (without description of apparatus) and the reflected energy is very Propagation of the Dutch paper dealt with in 1933 Abstracts, in a medium with continuously varying refractive index is dealt with by summing the effect of a P. 496. number of the slightly differing layers referred to MEASUREMENTS OF HEIGHTS OF THE KENNELLY- above. With the assumption that p, varies very HEAVISIDE LAYER IN JAPAN. I.-AUGUST, little in a wavelength, it is found that practically 1932, TO JANUARY, 1933 [Beginning of no reflected energy is split off from the main wave Polar Year Programme].-T. Minohara and during its passage through the medium. Total Y. Ito. (Rep. of Rad. Res. in Japan, June, reflection takes place where the wave is at grazing 1933, Vol. 3, No. I, pp. L-I-L-31 : in incidence to the stratification. At perpendicular English.) incidence reflection takes place where µ = o. A series of monthly reports. The apparatus When the electron density is very small the wave employed will be described in a later issue (see next undergoes no change. [For an account of magneto - abstract). No deductions are made. For previous ionic theory and its application to wireless studies measurements by the same workers see 1932 of the ionosphere, see Appleton, 1933 Abstracts, Abstracts, p. 515. p. 30.] MEASUREMENTS OF THE IONISED LAYER HEIGHTS CONTINUOUS MEASUREMENTS OF THE VIRTUAL IN JAPAN [Description of Equipment for HEIGHTS OF THE IONOSPHERE [on a Fre- Pulse -Method Measurements].-T. Minohara quency of 4 loo kc/s].-T. R. Gilliland. and Y. Ito. (Rep. of Rad. Res. in Japan, (Proc. Inst. Rad. Eng., October, 1933, Vol. 21, September, 1933, Vol. 3, No. 2, pp. 99-113.) No. IO, pp. 1463-1475.) See 1933 Abstracts, For previous work, using the frequency -change p. 614. method, see 1932 Abstracts, p. 515. In English. C January, 1934 30 THE WIRELESS ENGINEER &
EFFECT OF THE LEONID METEOR SHOWER ON THE REPORT OF COMMITTEE ON RADIO PROPAGATION IONISED UPPER ATMOSPHERE.-T. Minohara DATA [Field Strength Graphs, Atmospheric and Y. Ito. (Ibid., pp. 115-125.) Noise Level Curves, Fading, etc.: Extension Observations, with the equipment referred to of Madrid Committee Data].-(Proc. Inst. above, on echoes during the showers in November, Rad. Eng., October, 1933, Vol. 21, No. Io, 1932. Conclusions reached are that meteors greatly PP. 1419-1438.) increase the number of echoes : the latter " come The frequency range covered is 150 to 1700 kc/s : down in rapid succession, and the chain of echoes distances extend up to 5 000 km. continues for 1/loo sec. or more." The meteors form ion clouds: " small meteors ionise the atmo- THE PROPAGATION OF MICRO -WAVES TO CON- sphere in the upper region, and the large meteors SIDERABLE DISTANCES.-G. Marconi. (La do likewise in the relatively lower region. The ion Ricerca Scientifica, 15th/31st Aug., 1933, clouds caused by large meteors would be one of 4th Year, Vol. 2, No. 3/4, pp. 71-72.) the causes of the great diversity in the degree of Announcement of the results dealt with in ionisation in the upper atmosphere and of the 1933 Abstracts, p. 615, r -h column. variations in the mode of propagation of radio SOME CHARACTERISTICS OF ULTRA -HIGH -FRE- waves." In English. QUENCY [5.I Metre] TRANSMISSION.-H. JAPANESE URSIGRAM. I.-FROM SEPTEMBER, 1932, Muyskens and J. D. Kraus. (Proc. Inst. Rad. TO MAY, 1933.-(Rep. of Rad. Res. in Japan, Eng., September, 1933, Vol. zr, No. 9, June, 1933, Vol. 3, No. I, pp. U-I-U-13 : in pp. 1302-1316.) English.) Experiments at the University of Michigan. A field -strength contour map of the neighbourhood SOLAR ACTIVITY AND RADIO RECEPTION.-H. T. is given, the receiving and calibrating methods Stetson. (Sci. Abstracts, Sec. B, July, 1933, being briefly described. The attenuation constant Vol. 36, No. 427, PP. 465-466.) is found to be o.36. Tests on receiving -aerial RADIO TESTS IN CANADA DURING THE SOLAR lengths show the importance of a properly re- ECLIPSE OF 31ST AUGUST, 1932J. T. sonant receiving aerial ; other tests were made in Henderson. (Hochf:tech. u. Elek:akus., which the transmitting aerial (full -wave dipole) September, 1933, Vol. 42, No. 3, pp. 79-85.) was rotated in various planes, and the results See 1933 Abstracts, pp. 264 (Henderson) and indicate that horizontally polarised radiation is 264-265 (Henderson and Rose) ; also 264 more rapidly attenuated than vertically polarised (Rose). (cf. Trevor and Carter, 1933 Abstracts, p. 334 see also Esau and Köhler, p. 381). LOW -FREQUENCY [Long -Wave] RADIO RECEIVING MEASUREMENTS AT THE BUREAU OF STAND- ULTRA-SHORT-WAVE TRANSMISSION [With Curves of ARDS IN 1931 AND 1932 [with Correlation Aeroplane and Motor -Car Reception on 4.5 between Sunspot Numbers and Average Metres, and Calculated Curves].-C. R. Transatlantic Signals, Atmospherics, and Englund. (Bell Lab. Record, November, Polarisation of Reflected Wave : etc.].- 1933, Vol. 12, No. 3, pp. 66-71.) E. B. Judson. (Proc. Inst. Rad. Eng., -FREQUENCY September, 1933, Vol. 21, No. EXPERIMENTS IN ULTRA -HIGH COM- 9, pp. 1354- MUNICATION [on 3 -Io Metre Waves, including 1363.) Transmissions from Summit of Mt. Fuji].- SHORT-WAVE COMMUNICATION BETWEEN AIR T. Nakai, R. Kimura and S. Ueno. (Rep. LINERS OVER 2 000 MILES. (World -Radio, of Rad. Research in Japan, June, 1933, Vol. 8th September, 1933, Vol. 17, No. 424, 3, No. I, pp. 7-17: in English.) Abbre- p. 303: paragraph only.) viated translation of the paper dealt with 173, -h CALCULATION OF SHORT-WAVE FIELD STRENGTHS: in 1933 Abstracts, p. r column. COMPARISON WITH OBSERVED VALUES.- LUMINOUS DISCHARGE BETWEEN LECHER WIRES Nakai : Namba and Tsukada. (See end of IN A PARTIALLY EVACUATED TUBE [and abstract under " Directional Wireless.") Its Use for Visual Study of Micro -Wave NIGHT TRANSMISSION OF MEDIUM -FREQUENCY Circuits].-Hershberger, Zahl and Golay. [Broadcast] WAVES BETWEEN 40 AND 2 000 (Physics, September, 1933, Vol. 4, No. 9, KILOCYCLES.-S. Namba and S. Ueno. pp. 291-293.) See 1933 Abstracts, p. 498, (Rep. of Rad. Res. in Japan, September, l -h column. 3, Sec. 7.) 1933, Vol. No. z, Abstr. p. ELECTROMAGNETIC WAVES IN A WIRE, WITH Short abstract only of paper in Japanese on CONCENTRATED ENERGY SOURCE.-W. Kes- field - strength measurements on U.S.A. and senich. (Journ. of Tech. Phys., Moscow, European broadcasting stations (distances 500- No. 5/6, Vol. z, 1932, pp. 398-411 : in 000 km). Curves give the relation between Russian.) distance and night intensity. Author's summary :-The theoretical foundation ATTENUATION OF OVERLAND RADIO TRANSMISSION of practical methods of calculating radiating IN THE FREQUENCY RANGE 1.5 t0 3.5 MEGA- systems is discussed. The necessity of a strict in- CYCLES PER SECOND.-C. N. Anderson. vestigation of electromagnetic waves in open con- (Proc. Inst. Rad. Eng., October, 1933, ductors, for concentrated energy sources, is pointed Vol. 2I, No. 10, pp. 1447-1462.) The I.R.E. out, and the general formulation of the problem Convention paper, an abstract of which was given. A solution is found for each of two cases, dealt with in 1933 Abstracts, p. 439. an infinitely small and an infinitely large wire EXPERIMENTAL WIRELESS 31 January, 1934 radius, giving spherical and cylindrical energy ON THE REALITY OF THE RESIDUE OF SPHERICAL dispersion in propagation along a wire. LIGHTNING. -E. Mathias. (Comptes Rendus, 3oth Oct., 1933, Vol. 197, No. 18, pp. CONTRIBUTION TO THE STUDY OF THE [Seismic] 962-964.) WAVE P. -P. Caloi. (La Ricerca Scientifica, 15/31st Aug., 1933, 4th Year, Vol. 2, No. BALL LIGHTNING [With Photographs]. -J. C. 3/4, Supp. pp. 25-46.) Jensen. (Physics, October, 1933, Vol. 4, VELOCITY OF ELASTIC WAVES IN GRANITE AND No. to, pp. 372-374.) NORITE.-L. D. Leet. (Physics, October, BREAKDOWN AT LIGHTNING ARRESTERS ON H.T. 1933, Vol. 4, No. to, pp. 375-385.) LINES OCCURRING AT SUNRISE [Ionising Effect]. -F. Ringwald. (E.T.Z., 31st Aug., ATMOSPHERICS AND ATMOSPHERIC 1933, Vol. 54, No. 35, p. 856.) See also ELECTRICITY 1932 Abstracts, pp. 89 and 577, George and CORRELATION OF RADIO ATMOSPHERICS WITH Brownlee : Menge. METEOROLOGICAL CONDITIONS. -T. Nakai. LIGHTNING ARRESTERS FOR THE PROTECTION OF (Rep. of Rad. Res. in Japan, September, 1933, AIRCRAFT WIRELESS EQUIPMENT, INVESTI- Vol. 3, No. 2, pp. 155-175.) The full English GATED WITH THE CATHODE-RAY OSCILLO- version of the Japanese paper dealt with in GRAPH .-H. Viehmann. (E.T.Z., 5th Oct., 1932 Abstracts, pp. 335-336. 1933, Vol. 54, No. 40, pp. 956-958.) SURVEY OF THUNDERSTORMS -2ND ANNUAL RE- The paper deals chiefly with the DVL homo- PORT. -(Electrician, 27th Oct., 1933, Vol. geneous-field air-gap protector based on the tit, No. 17, p. 528.) writer's previous investigations (1931 Abstracts, p. r -h col.) which is provided with tungsten ELECTRICAL DISTURBANCES APPARENTLY OF EXTRA- 377, ionising points : when the transmitter is in action TERRESTRIAL ORIGIN [" Static Hiss " Type these points give a glow discharge which strongly Atmospherics]. -K. G. Jansky. (Proc. Inst. ionises the main gap, while if the transmitter is not Rad. Eng., October, 1933, Vol. 21, No. to, working the arrival of the surge produces a similar See preliminary letter, pp. 1387-1398.) effect. It is suggested that this method of pre - 1933 Abstracts, p. 561, l -h column. ionisation should be useful also in power engin- AUDIO -FREQUENCY ATMOSPHERICS [Swishes, eering. A final section deals with glow -discharge - Tweeks, etc.: Their Habits and Origins]. - tube arresters. The introductory section mentions E. T. Burton and E. M. Boardman. (Proc. a Telefunken suggestion of connecting the aerial, Inst. Rad Eng., October, 1933, Vol. 21, before it enters the aircraft, through a coupling No. 10, pp. 1476-1494.) coil to the main body of the aircraft, the radio appa- The writers' observations lead them to the con- ratus being coupled inductively and with the intro- clusion that Barkhausen's " multiple reflection " duction of sufficiently high insulation. This plan theory (1931 Abstracts, p. 376) fails for swishes, is admitted to provide excellent protection, but the but is satisfactory for tweeks. It is suggested necessary matching involves almost a re -design that swishes may be related to the occasionally of the apparatus. observed phenomenon of swinging and flashing CORONA DUE TO SURGES [Investigation by use of auroral beams (cf. Garber, next column). Dust Figures]. -Y. Toriyama. (E.T.Z., ON THE ELECTRIC CHARGE COLLECTED BY WATER 21st Sept., 1933, Vol. 54, No. 38, pp DROPS FALLING THROUGH IONISED AIR IN 909-910.) A VERTICAL ELECTRIC FIELD.-J. P. Gott. (Proc. Roy. Soc., Oct., 1933, Vol. 142, No. THE METEOR SHOWERS OF 9TH OCTOBER, 1933.- A E. Esclangon. (Comptes Rendus, 16th 846, pp. 248-268.) The experiments here described (with one size of October, 1933, Vol. 197, No. 16, pp. 801-804.) drop only) give results in accordance with C. T. R. OBSERVATION AND PHOTOGRAPHY OF THE METEORS Wilson's theory of the mechanism of thunder- OF 9TH OCTOBER, 1933.-G. C. Flammarion storms and the electric charge brought down by and F. Quénisset. (Comptes Rendus, 3oth rain. Oct., 1933, Vol. 197, No. 18, pp. 978-979.) DEVELOPMENT OF THE LIGHTNING DISCHARGE. - ON THE AUDIBILITY OF THE AURORA BOREALIS Ashmore. (Nature, 23rd Sept., 1933, Vol. [Observations from a Height of 2 000 Feet : 132, P. 477.) Streamers take 6-8 Seconds to pass Overhead A note recording a suggestion due to S. E. Ash- at about too Feet Height, with Crackling more that Schonland and Collens' letter on the Sound : Draperies emit Sound for Minute development of the lightning discharge (November or more on end]. -C. M. Garber. (Science, Abstracts, p. 616) receives confirmatory evidence 8th Sept., 1933, Vol. 78, No. 2019, pp. froln the noise heard in a wireless receiver during 213-214.) " be a storm. The first click " may due to the pre- OBSERVATIONS ON POLAR AURORAS AT SCORESBY liminary downward avalanche of electrons and the SOUND DURING THE POLAR YEAR [including lightning flash " heard " afterwards may be that Phase Opposition between Sunspot Curves progressing by thermal ionisation. and Auroral and Magnetic Curves]. -A. COSMIC RAYS AND LIGHTNING [Suggestion that Dauvillier. (Comptes Rendus, 3oth Oct., Penetrating Particles make Conducting 1933, Vol. 197, No. 18, pp. 997-1000.) Paths]. -J. Tandberg. (Nature, 4th Nov., The writer concludes :-" Time differences of 1933, Vol. 132, p. 712.) some tens of hours with respect to the passage of a C2 January, 1934 32 THE WIRELESS ENGINEER & focus of solar activity across the central meridian GLOW DISCHARGE AT HIGH PRESSURES [Io t0 760 have often been reported, but this is the first time mm Hg]. -A. von Engel, R. Seeliger and that a displacement of a half -period of solar M. Steenbeck. (Zeitschr. f. Physik, 1933, rotation has appeared so clearly. This result is of Vol. 85, No. 3/4, pp 144-16o.) the greatest importance. Not only does it ruin the theories attributing the auroral and magnetic pheno- THE EFFECT OF ULTRAVIOLET ILLUMINATION ON mena to ultra-violet rays emitted by the sun, by THE ELECTRIC SPARK. -J. Claussnitzer. (Physik. Zeitschr., 1st Nov., 1933, Vol. 34, attributing the observed delays to the passage No. 21, time of the electrified particles, but it also proves pp. 791-807.) that it is the fine equatorial coronal jets which are THE NATURE OF GAS Ioxs.-O. Luhr. (Phys. the sole cause of these phenomena. The study Review, 15th Sept., 1933, Series 2, Vol. 44, of eclipses has actually shown that the most intense No. 6, pp. 459-462.) coronal jets are not radial and that they spring, not " The mass of gas ions formed in a glow dis- from the edges of the solar disc, but in front of or charge and aged up to lob impacts was determined behind this. In a period of solar minimum the by a Dempster type of mass -spectrograph. . . . electronic jets coming from an active focus have Air ions include all possible nitrogen and oxygen an energy sufficiently reduced for them to be bent, ions, the aged air ions consisting principally4of by the solar magnetic field of M. Deslandres, to such Nt, N,, and O+ together with the oxidesjof an extent that they reach the earth in a direction nitrogen." opposite to that of their emission, like a wide cometary tail, diffuse and bent back." METEOROLOGICAL AND SOLAR INFLUENCES ON THE INTENSITY OF COSMIC RADIATION. -V. CONTINUOUS PHOTOELECTRIC RECORDING OF POLAR F. Hess and others. (Helvet. Phys. Acta, AURORAS [and the Variation of Intensity in Fasc. 7, Vol. 6, 1933, pp. 480-482.) the Ratio 1 : Io4].-A. Dauvillier. (Comptes Rendus, 9th October, 1933, Vol. 197, No. PENETRATING POWER AND ABSORPTION CO- 15, pp. 780-781.) EFFICIENT OF COSMIC RADIATION. -E. Lenz. (Zeitschr. Physik, 1933, Vol. 85, 7/8, These first records show a fluctuation of I : 104 f. No. in a period of minimum solar activity. " There is pp- 435-438.) no connected geophysical phenomenon susceptible THE ELECTRICAL CONDUCTIVITY OF THE LOWER to variations of such proportions." The inter- ATMOSPHERE PRODUCED BY COSMIC RADIA- national notation (o-4) represents practically the TION. -E. Lenz : Regener. (Helvet. Phys. logarithm of intensity. The importance of such Acta, Fasc. 7, Vol. 6, 1933, p. 479.) quantitative measurements is stressed. Summary only of results derived from Regener's measurements. The maximum value of ionising MAGNETIC OBSERVATIONS AT SCORESBY SOUND power was at a height of 13 km, the value being DURING THE POLAR YEAR. -J. P. Rothé. (Comptes Rendus, 6th Nov., 1933, Vol. 197, 45 I/cm3sec. compared with 12 I/cm3sec. at 25 km. At the latter height the ion content was I x Io' No. 19, pp. 1057-1059.) Among the results I/cme and the conductivity 5o x Io -12 ohm-' cm -3. mentioned, a periodicity of was also about 28 days, both for very disturbed days and for It found that the latitude -dependence of the cosmic radiation at sea level showed a complete calm days, occurred regularly throughout the year : with the beginning of the disturbance of 3oth April, 1933, symmetry regard to the geographical equator. was particularly clearly marked at Scoresby Sound, THE ABSORPTION CURVE OF THE COSMIC RADIA- and an examination of the hours of arrival indicates TION AND ITS SIGNIFICANCE.-E. Regener. that this beginning was not simultaneous over the (Helvet. Phys. Acta, Fasc. 6, Vol. 6, 1933, pp. whole earth, but that the disturbance travelled 450-456.) Additional to the paper dealt with from the magnetic North, eastwards, taking about in 1933 Abstracts, p. 442, r -h column. r minute to encircle the globe. ON THE TECHNIQUE AND DESIGN OF WILSON CONTRIBUTION TO THE CHARACTERISATION OF CLOUD -CHAMBERS. -O. Dahl, L. R. Hafstad MAGNETIC AGITATION [Measuring the Actual and M. A. Tuve. (Review Scient. Instr., Length of the Recorded Curves Day by Day July, 1933, Vol. 4, No. 7, pp. 373-378.) by means of a Curvimeter].-Y. Labrouste. A PORTABLE DOUBLE GEIGER COUNTER. -R. D. (Comptes Rendus, 25th Sept., 1933, Vol. 197, Bennett, J. C. Stearns and W. P. Overbeck. No. 13, pp. 653-655.) (Ibid., pp. 387-390.) ON THE TERRESTRIAL REPERCUSSIONS OF VARIA- THE MECHANISM OF THE GEIGER -MÜLLER COUNTER TIONS OF SOLAR ACTIVITY [and the Pre- [for Cosmic Rays]. -W. Christoph and W. ponderant Importance of the Invisible Active Hanle. (Physik. Zeitschr., 15th Aug., 1933, Foci]. -A. Nodon. (Comptes Rendus, 23rd Vol. 34, No. 16, p. 640.) October, 1933, Vol. 197, No. 17, pp. 907-908.) ON THE POSSIBILITIES OF APPLICATION OF A NEW ON CERTAIN REGULARITIES WHICH APPEAR IN THE PROPORTIONAL AMPLIFIER [for Cosmic Rays]. SUCCESSION OF SOLAR PHENOMENA. -H. -G. Hoffmann. (Naturwiss., 8th Sep- Deslandres. (Comptes Rendus, 11th Sept., tember, 1933, Vol. 21, No. 36, p. 662.) 5933, Vol. 197, No. II, pp. 589-593.) PROGRESS OF WORLD -SURVEY OF COSMIC RAYS. - NEW CYCLE OF SUNSPOTS MAY BEGIN IN NEXT A. H. Compton. (Trans. Am. Geophys. FEW MONTHS. -(Sci. News Letter, 28th Oct., Union, 14th Annual Meeting, April, 1933, 1933, Vol. 24, No. 655, p. 276.) pp. 154-158.) EXPERIMENTAL WIRELESS 33 January, 1934
PROPERTIES OF CIRCUITS use a short segment of transmission line in place of a tuned circuit. Parallel wires are generally pre- THE EFFECT OF INDUCTANCE ON THE INTERMITTENT and adjustments GLOW DISCHARGE [and Applications as ferred, for ease of construction Constant -Frequency Sine -Wave Generator but the writer (using Pistolkors' method) obtain, Music, an expression for the total radiation resistance of for Bridge Measurements, Electrical case, etc.]. E. Kock. (Physics, October, a concentric line and, applying this to a specific -W. finds a value of only o.o86 ohm compared with 1933, Vol. 4, No. Io, pp. 359-361.) The insertion of an inductance in the con- 3.02 ohms for open wires. denser arm of an intermittent glow -discharge circuit PRODUCTION AND UTILISATION OF MICRO -RAYS [in- was found to change the voltage/frequency curve : cluding Mathematical Treatment of Re- the wave form of the voltage across the condenser tarding -Field Oscillator : Constant (Opti- became sinusoidal, and other new wave forms were mum) Frequency Curves and Their Import- introduced. Within a certain range, the frequency ance for Amplitude Modulation : etc.]. - was practically independent of voltage, resistance or A. G. Clavier. (Electrical Communication, tube characteristics. July, 1933, Vol. 12, No. I, pp. 3 -II.) SELF-EXCITED NON-LINEAR VALVE OSCILLATIONS REMARKS ON THE MODULATION OF ULTRA -SHORT [Relaxation Oscillations : Comparison be- WAVES [Two Optimum Values of Anode tween " Capacity " and " Self -Inductance " Potential for Pierret Circuit Modulation]. - Connections, etc.]. -H. Straub. (Helvet. E. Pierret. (Journ. de Phys. et le Rad., No. 4, Phys. Acta, Fasc. 6, Vol. 6, 1933, pp. Vol. 4, 1933, pp. 79-80 s.) 385-410: in German). Conclusion of the paper referred to in 1933 Abstracts, p. 62o, A SPECIAL TYPE OF MAGNETRON OSCILLATION r -h column. [fulfilling the Barkhausen-Kurz Formula]. - A. A. Slutzkin and P. P. Leljakow. (Physik. ON SOME GENERAL PROPERTIES OF RESONANCES IN Ber., 1st Aug., 1933, Vol. 14, Vol. 15, p. 1266.) NON-LINEAR MECHANICS. -N. Kryloff and N. Bogoliùboff. (Comptes Rendus, 23rd ON THE THEORY OF THE ELECTRON -SPACE -CHARGE Oct., 1933, Vol. 197, No. 17, pp. 908-910.) OSCILLATIONS [Retarding -Field Circuit : the For previous work of these authors see 1932 Advantages of a Graphical Treatment]. - Abstracts, p. 403. M. Dick. (Helve!. Phys. Acta, Fasc. 7, Vol. 6, 1933, German summary only.) ALL -PASS NETWORKS [Attenuation Constant Zero pp. 486-488: at All Frequencies : for Delay or Phase - ULTRA -SHORT [Micro-] WAVES IN OPPOSED -PHASE Correcting Networks]. -K. Nagai. (Rep. EXCITATION [Retarding -Field Oscillator : of Rad. Res. in Japan, September, 1933, the Grid Electrode Circuit as Frequency- Vol. 3, No. 2, Abstr. Sec. p. 9: abstract Determining Element : Effects of Anode : only of paper in Japanese in English.) Diameter : Design of Special Valves for a NETWORK SYNTHESIS." -C. M. Gewertz. (Book Continuous Range of Wavelengths from Review in Proc. Inst. Rad. Eng., October, 13.5 to 17.5 cm]. - J . Müller. (Helvet. 6, 1933, 1933, Vol. 21, No. Io, p. 1498.) Phys. Acta, Fasc. 7, Vol pp. 491- in German.) See also 1933 Abstracts, THE CALCULATION OF MODULATION PRODUCTS 493 : [for Valve Characteristics]. -Bartlett. (See PP 443-444. under " Valves and Thermionics," p. 40.) FREQUENCY MULTIPLICATION AT ULTRA -HIGH FRE- OUENCIES BY CATHODE-RAY SWEEPING OVER THE MUTUAL REACTION OF ANODE AND GRID TOOTHED DISC. --S. L. Ting. (Wireless CIRCUITS IN AMPLIFIERS AND BROADCAST October, 1933, Vol. Io, No. 12I, RECEIVERS [Simplified Treatment with Engineer, Curves and Tables]. -W. Kautter. (E.T.Z., PP. 555-556.) 21st Sept., 1933, Vol. 54, No. 38, p. 922 : MICRO -WAVES AND THEIR USE IN RADIOCOM- summary only.) MUNICATION [Survey of Circuits for Trans- mission and Reception : Royal Naval TRANSMISSION Institute Researches : List of Shortest A MAGNETOSTATIC OSCILLATOR FOR THE GENERA- Wavelengths reached by Various Workers : TION OF I TO 3 cm WAVES. -C. E. Cleeton and etc.]. -N. Carrara. (Alta Frequenza, N. H. Williams. (Phys. Review, 1st Sept., August, 1933, Vol. 2, No. 3, pp. 465-496.) 1933, Series 2, Vol. 44, No. 5, p. 421.) The writers have produced continuous waves of FEATHERWEIGHT SETS FOR THE ULTRA -HIGH 28 : especially length about I cm, using tubes of the split anode FREQUENCIES [56 and Mc/s type, of very small dimensions. The letter describes for Soaring Planes (Gliders)]. -R. A. Hull. their measurement by means of a simple grating (QST, September, 1933, Vol. 17, No. 9, spectrometer consisting of two parabolic brass PP. 27-31.) mirrors, about 1 m in diameter, and an echelette FREQUENCY STABILISATION OF TRANSMITTER BY grating. Two LUMINOUS QUARTZ RESONATORS EACH RADIATION RESISTANCE OF CONCENTRIC -CONDUCTOR CONTROLLING A PHOTOCELL. -Lorenz Com- TRANSMISSION LINES [and Comparison with pany : Gerth. (German Pat. 568 795, pub. Parallel Lecher Wires : for use in Micro - 24.1.1933.) For a method also using Wave Oscillator Circuits].-R. Whitmer. luminous quartz resonators but employing (Proc. Inst. Rad. Eng., September, 1933, Vol. the gaseous conductivity at resonance, see 21, No. 9, pp. 1343-1353.) Pat. 568,794, pub. 24.1.1933, Lorenz : For wavelengths below i m it is customary to Herzog. January, 1934 34 THE WIRELESS ENGINEER &
A STUDY OF THE FREQUENCY VARIATION OF VALVE (impracticable) : single side -band and quiescent GENERATORS (VI) -OSCILLATION CHARACTER- carrier (valuable in combination with other systems ISTICS OF B -BATTERY -LESS OSCILLATORS. - as adding to privacy, apart from other merits). S. Ishikawa. (Rep. of Rad. Res. in Japan, SUPPRESSION OF TRANSMITTER HARMONICS: COR- June, 1933, Vol. 3, No. I : Abstracts Section, p. 3 : short English summary of RECTION.--Dietsch. (Electronics, July, 1933, Japanese paper.) Vol. 6, No. 7, p. 199.) Correction to the " For use with a heterodyne wavemeter, a B - article referred to in 1933 Abstracts, p. 565, battery -less oscillator is recommended, because of 1-h column. its simplicity of operation and because of absence of frequency variation due to fluctuations in the THE CALCULATION OF HARMONIC PRODUCTION IN plate supply source. The paper describes the THERMIONIC VALVES WITH RESISTIVE LOADS [up to Sixth Harmonic].-D. C. Espley. oscillation characteristics of such an oscillator, and (Proc. Rad. Eng., Vol. also compares it with other normal or dynatron Inst. October, 1933, oscillators as regards frequency stability." For 21, No. Io, pp. 1439-1446,1 previous work see 1933 Abstracts, p. 37, r -h column. GRID .MODULATED VALVE TRANSMITTERS [Square - DEVELOPMENT OF THE QUARTZ CONTROL OF Topped H.F. Modulating Voltages. -Tele, TELEFUNKEN HIGH -POWER STATIONS. funken : Buschbeck. (German Pat. 577 871, - : R. Bechmann. (Telefunken -Zeit., April, 1933, pub. 6.6.1933 Hochf: tech. u. Elek : akus. October, 1933, Vol. 42, 4, Vol. 14, No. 63, pp. 17-29.) No. p. 147.) Including a description of the new, self-contained " All grid modulation methods involve a move- " vacuum quartz " with continuous temperature ment of the working point of the h.f. grid a.c. poten- regulation (see under " Measurements and Stan- tial in time with the modulation frequency : as a dards ") and the bridge circuit in which it is used. result, in addition to the height of the anode - This combination is employed at the Langenberg current curve being altered, its breadth also is and Breslau, and the Zeesen short-wave, broad- changed, giving -even with a rectilinear valve casting stations. The mean and maximum devia- characteristic -a non-linear modulation character- tions of Langenberg and Breslau are less than istic. According to the invention the h.f. modu- 50 c/s (constancy at least 5 x b). lating potential is given a rectangular wave form, io so that the breadth of the anode -current impulse THE TECHNIQUE OF LONG-DISTANCE RADIO COM- remains constant." MUNICATION [Survey of Transmitters, Modu- lation Methods, Frequency Stabilisation, ON THE ADJUSTMENT OF [the Choke Coils and the Beam Aerials, etc.). Gori. (Alta Neutralisation and Balancing of the Push - -V. Fre- of quenza, August, 1933, Vol. 2, No. 3, pp. Pull Circuits Short -Wave] POWER AMPLI- (Rep. 377-420.) FIERS. -S. Amari. of Rad. Res. in Japan, June, 1933, Vol. 3, No. I : Abstracts TRITET MULTI -BAND CRYSTAL CONTROL : A UNI- Section p. 4: summary only of Japanese VERSAL FIVE -BAND [I.75-28 Mc/s] TRANS- paper: in English.) MITTER EXCITER UNIT. -J. J. Lamb. THE INVERTED ULTRAUDION AMPLIFIER : WORKING (QST, October, 1933, Vol. 17, No. Io, pp. 9-15.) THE TRIODE AS A SCREEN -GRID TRANS- MITTING AMPLIFIER. - H. Romander. FADING ELIMINATION BY ROTATING POLARISATION (QST, September, 1933, Vol. 17, No. 9, OF DIRECTED BEAM : ROTATION FREQUENCY pp. 14-18.) LOWER THAN OSCILLATING FREQUENCY : SIMULTANEOUS " DIRECTION WOBBLE."- APPLICATIONS OF THE DYNATRON [to Receivers, Wavemeters, Standard Signal Generators, (Hochf:tech. u. Elek:akus., August, 1933, Audio Oscillators : to Measurement of R.F. Vol. 42, No. 2, p. 75 : U.S.A. Pat. No. r 898 058, pub. 21st Feb., 1933, RCA and Resistance, Power Factor, Admittance, etc. : Lindenblad.) Precautions for obtaining Full Advantages]. -M. G. Scroggie. (Wireless Engineer, THE SINGLE SIDE -BAND SYSTEM APPLIED TO October, 1933, Vol. IO, No. 121, pp. 527-54o.) SHORT-WAVE TELEPHONE LINKS. -A. H. With a bibliography of 35 items. The writer Reeves. (bourn. I.E.E., September, 1933, concludes :-" The dynatron is, as has been seen, Vol. 73, No. 441, Pp. 245-279.) The full useful. It might be still more useful if the valve paper, a summary of which was dealt manufacturers cease to regard it as an accident." with in 1933 Abstracts, p. 391, 1-h col. PRIVACY SYSTEMS FOR RADIO TELEPHONY. -A. J. RECEPTION Gill.-(P.O. Elec. Eng. bourn., October, THE RECEPTION OF ULTRA -SHORT [Decimetre] 1933, Vol. 26, Part 3, pp. 224-230.) WAVES WITH THE RETARDING -FIELD Switched -channel system : masking speech by AUDION.-H. E. Hollmann. (Hochf:tech. u. other noises (impracticable) : frequency -transpos- Elek:akus., September, 1933, Vol. 42, No. 3, ing (plain inversion, spread sideband, and split Pp 89-99.) band systems-" scrambling ") : systems intro- A full account of the researches dealt with in ducing delay (with transposition of order of sounds): Abstracts, 1933, p. 621. Reference is made to phase -change or frequency -change signalling (dubi- Carrara's paper (1933, p. 38, r -h col.) " which in ous) and periodic variation of carrier frequency certain points arrived at analogous results,without EXPERIMENTAL WIRELESS 35 January, 1934 however drawing from them all the conclusions AN OUTLINE OF THE ACTION OF A TONE-CORRECTED here treated." HIGHLY SELECTIVE RECEIVER. - E. B. Moullin. (Proc. Inst. Rad. Eng., September, A NEW REGENERATIVE DETECTOR CIRCUIT FOR 1933, Vol. 21, No. 9, pp. 1252-1264.) ULTRA -SHORT WAVES [Regeneration de- The writer concludes :-' Since we find ulti- pending on Capacitive Impedance common mately that the permissible difference of frequency to Grid and Plate Circuits : " the Cathode between stations depends only on the acoustic Impedance Ultraudion "].-R. Hilferty. reproducer, we might suspect that the highly (QST, November, 1933 Vol. 17, No. selective circuit and tone corrector are not neces- pp. 15-17.) sary. But this is not so, because the whole effect C.w. telegraphy may be received at 56 Mc/s as depends on the action of a linear detector in shifting on lower frequencies. The receiver may be made the acoustic spectrum : the detector has this to function super-regeneratively by increasing the property only if the desired r.f. voltage dominates s.g. voltage to the point of " squegging." " Con- the undesired voltage. This automatic domination trary to expectations, however, it has been found can be secured only by means of a receiver which that there is little to be gained by super -regenera- has a very narrow band width to radio frequency. tion excepting in the case of a badly frequency - This narrow band width will necessitate a tone - stable modulated carrier. For an excellently correcting system : this system is simplest when carrier, straight regeneration produces the more it has to correct the resonance curve of a simple satisfactory results." resonant circuit." [and the " Stenode COMPARISON BETWEEN SUPER -REGENERATIVE AND TONE CORRECTING AMPLIFIERS (See Radiostat " Receiver]. -G. Priechenfried. REGENERATIVE RECEPTION.-Hilferty. Vol. preceding abstract.) Gf. Reinartz, p. 36. (Wireless Engineer, September, 1933, 10, No. 120, pp. 487-49o.) FEATHERWEIGHT SETS FOR THE ULTRA -HIGH THE EFFECT OF THE RECTIFIER AND CIRCUIT FREQUENCIES [56 and 28 Mcls : especially SELECTIVITY ON INTERFERENCE. -F. M. for Soaring Planes (Gliders)].- R. A. Hull. -Radio, 8th and 15th 1933, Vol. 17, No. 9, pp. Colebrook. (World (QST, September, Vol. 17, Nos. 424 and 425, 27-31.) Sept., 1933, pp. 298, 30o and 333-334.) SUPERHETERODYNES [Adaptor ULTRA -SHORT-WAVE A NOTE ON DEMODULATION UNDER PRACTICAL for 5-7 m Waves]. -W. T. Cocking. (Wire- CONDITIONS [" Apparent " Demodulation less World, 24th November, 1933, Vol. 33, of a Weak by a Stronger Station]. -M. V. pp. 4o6-407.) Callendar. (Wireless Engineer, September, Ex- -CAR 1933, Vol. io, No. 120, pp. 480-483.) THE NEED FOR THE SUPPRESSION OF MOTOR perimental investigation of the phenomenon INTERFERENCE WITH ULTRA -SHORT-WAVE Appleton, Cole- RECEPTION.-(QST, November, 1933, Vol. discussed by Butterworth, brook, Lewis and others (Abstracts, 1931, 17, No. II, p. 9.) ; 96 ; etc.). p. 440 ; 1932, p. 523 1933, p. ON BROADCAST INTERFERENCE : VDE COMMISSION DEMODULATION WHICH IS LITTLE AFFECTED BY PROPOSED REGULATIONS FOR PREVENTION OF ITS OCCURRENCE IN SUPER- Sep- FADING: MAN-MADE STATIc.-(E.T.Z., 28th REGENERATIVE RECEPTION. H. O. Roosen- tember, 1933, Vol. 54, No. 39, pp. 945-951.) stein. (Hochfaech. u. Elek:akus., Sept., With numerous diagrams relating to the and 1933, Vol. 42, No. 3, pp. 85-89.) various types of electrical apparatus The writer points out that while modern high- the recommended methods of treatment. grade broadcast receivers are provided with special devices to compensate for fading, the ASPHALT EMULSION REDUCES [High -Voltage] IN- super -regenerative circuit has the innate property SULATOR RADIO TROUBLES [Interference]. - of equalising signal amplitudes differing in the ratio F. O. McMillan. (Elec. World, 5th August, of as much as a thousand to one. " Since this 1933, Vol. 102, No. 6, pp. 185-187.) remarkable fact, so far as the writer is aware, has of a theoretical investi- STEAM TRAINS [and Steam never been the subject INTERFERENCE FROM gation, the following paper gives an explanation Blasts from Cylinders as a Possible Cause] : of the phenomenon." It is shown that for such CORRESPONDENCE.--(World-Radio, 20th and necessary and suf- November, 1933, " fading -free " reception it is 27th October, and 3rd demodulation characteristic (field- 17, pp. and 586.) ficient for the Vol. 515, 551 strength/rectified current) to have a logarithmic to I = logaat E + B : then [Man -Made] ELECTRICAL INTERFERENCE. - A. form corresponding 17th and 24th Nov., if the field strength is modulated between the Morris. (World -Radio, II I2 17, Nos. and 435, limits E1 and E2, the current fluctuation - 1933, Vol. 434 pp. 651, depends only on the ratio 653 and 691-692 ; to be continued.) = Alog,,t EI/E2, which E1/E2 (i.e. on the degree of modulation) and not on RECEIVING AERIALS the absolute values of E1 and E2, i.e. on the fading. THE REACTANCE OF BROADCAST receivers (on a 3.8 m AND ITS INFLUENCE ON THE FUNCTIONING Tests on super -regenerative REJECTOR CIRCUITS.- wave, with an aerial power of i watt) showed that OF ABSORPTION AND in telephone Klutke. (See under " Aerials and Aerial there was neither an appreciable change Systems ".) signal strength, nor distortion, when the distance January, 1934 36 THE WIRELESS ENGINEER & between aerials was decreased from z 000 m to 2 m. AUTOMATIC GAIN CONTROL FOR THE [" Single - This held good when the telephones were connected Signal ") SUPERHET [Adaptation of System directly behind the leaky -grid detector, so that the used in RCA Diversity Reception]. -J. J. result could not be due to the limiting action of Lamb. (QST, November, 1933, Vol. 17, over -loaded amplifier valves. The demodulation No. II, pp. 32-33 and 35.) characteristic of such a receiver was then plotted, the current in the transmitting aerial (for a 7 -metre DEVELOPMENTS IN CRYSTAL FILTERS FOR S.S. wave) being varied from 0.04 to 4 amperes and the [" Single -Signal "] SUPERHETS.-J. J. Lamb. rectified current changes in the audion anode (QST, November, 1933, Vol. 57, No. II, circuit, produced by switching -on the unmodulated PP. 21-24.) transmitter, being measured. The resulting char- acteristic was found to be almost exactly logarithmic S. -G. VALVE AS SUPERHET DETECTOR [Mathematical (Fig. 2). In his next section the writer analyses the Analysis and Deductions]. -C. B. Fisher : super -regenerative process to see how this char- White. (Wireless Engineer, October, 1933, acteristic arises. Finally he shows that although Vol. Io, No. 121, pp. 541-542.) with such a receiver non-linear distortion is bound " The analysis of the general case establishes to occur, it is hardly more serious (for transmitter these results [White, 1933 Abstracts, p. 99] except modulation percentages up to 5o %) than that given that modulation is shown to be due to the variation by a square -law detector : while complete freedom of the plate resistance with grid -voltage, and not from distortion can be obtained by giving the to variation of as stated by White, and shows transmitter an exponential modulation char- other desirable operating conditions." acteristic. A patent for such a process has been applied for. DETECTOR CIRCUIT WITH SCREEN -GRID VALVE : DAMPING ADJUSTMENT WITHOUT CHANGE A TYPE OF SUPER -REGENERATIVE RECEIVER USING OF TUNING. -Philips' Company. (German A SQUEGGING " " ULTRA -HIGH -FREQUENCY Pat. 567 859, pub. 17.5.1933 : Hochf:tech. u. OSCILLATOR TO GIVE THE INTERRUPTION Elek:akus., Oct., 1933, Vol. 42, No. 4, p. 148.) FREQUENCY, AND OPERATING WELL ON C.W. The input circuit of the tetrode is connected across SIGNALS.-Reinartz. (QST, September, 1933, the control grid and cathode, the output comes from Vol. 17, No. 9, p. 66.) Cf. Hilferty, p. 35. the screen grid. In the anode circuit there is a closed circuit tuned to the signal : it is not back - NOTE ON THE MODE OF ACTION OF SUPER -RE- coupled to the grid circuit, the damping reduction GENERATIVE RECEIVERS [Correspondence]. being accomplished by change of anode voltage. -Y. Marrec : P. David. (L'Onde Élec., June, 1933, Vol. 12, No. 138, pp. 326-328.) AUDION [Leaky -Grid Detector] WITHOUT BLOCKING Argument on David's paper on the three CONDENSER OR LEAK. -Loewe and Rothe. types of super -regenerative reception (1928 (German Pat. 576 035, pub. 6.5.1933.) Abstracts, p. 519). Those parts of the control electrode exposed to electron bombardment are AUTOMATIC FADING COMPENSATION coated with a badly IN BROAD- conducting substance, and the electrode is given a CAST RECEIVERS [using : Variable -Mu Valves positive bias. Owing to the collecting of electrons Short Survey, including Magnetron Method]. -(E.T.Z., on the badly conducting coating the arrangement 26th Oct., 1933, Vol. 54, No. 43, behaves as an audion. PP. 5043-1045.) AUTOMATIC VOLUME CONTROL, " CRACK KILLER " CONSTANTLY ILLUMINATED PHOTOCELL AS DE- TECTOR IN MAINS -DRIVEN RECEIVER, TO AND FADING COMPENSATOR, USING A AVOID MAINS NOISES. SELENIUM PHOTOCELL. -H. Thirring. (Funk - -Radio Patents Cor- Magazin, August, 1933, Vol. 6, No. 8, pp. poration. (German Pat. 575 554, pub. 484-485.) 29.4.1933.) FADING ELIMINATION BY CONTROLLING LOCAL [Complete Elimination of] " Hum " IN [Mains - NOTE -GENERATOR BY COMBINED OUTPUT Driven] SHORT-WAVE RECEIVERS.-( World- OF RECEIVERS FED FROM SPACED AERIALS. - Radio, 17th Nov., 1933, Vol. 17, No. 434, RCA. (German Pat. 574 178, pub. 10.4.1933.) p. 66o.) ON THE APPLICATION OF NEON TUBES IN A LIMITER AMPLIFIER WITH VARIABLE BAND BREADTH, USING [for Fading Compensation in Telegraphic A VARIABLY COUPLED ABSORBING CIRCUIT. Reception : Very Successful up to zoo -RCA. (German Pat. 574 567, pub.18.4. w.p.m. or over]. -K. Ono and H. Seki. 1933 : Hochf:tech. u. Elek:akus., September, (Rep. of Rad. Res. in Japan, September, 1933, Vol. 42, No. 3, p. 112.) 1933, Vol. 3, No. z, Abstr. Sec. p. 13: abstract only of paper in Japanese.) SELECTIVE RECEPTION USING LONG CLOSED LOOP EARTHED AT BOTH ENDS, WITH SEVERAL GLOW -DISCHARGE -TUBE COUPLING FOR AMPLIFIERS. AMPLIFIERS DISTRIBUTED AT INTERVALS : -H. Smith and E. E. Hill : Peek. (Wireless OUTPUTS COMBINED AFTER PHASE ADJUST- Engineer, September, 1933, Vol. io, No. Izo, MENT. -J. H. Hammond. (U.S.A. Pat. See 1933 Abstracts, p. : I P. 492). 212 the goo 283, pub. 7.3.1933 : Hochf:tech. u. present writers quote an earlier patent Elek:akus., September, 1933, Vol. 42, No. 3, for such a coupling. p. 112.) EXPERIMENTAL WIRELESS 37 January, 1934
A STUDY OF RECEPTION FROM SYNCHRONISED TUNING SCALES ON BROADCAST RECEIVERS. -E. BROADCAST STATIONS [Common -Wave Schwandt. (Funktech. Monatshefte, Sep- Broadcasting]. -C. B. Aiken. (Proc. Inst. tember, 1933, No. 9, PP 347-350.) Rad. Eng., September, 1933, Vol. 21, No. g, THE WIRELESS WORLD D.C. SUPERHET [4 -Valve]. - pp. 1265-1301.) W. T. Cocking. (Wireless World, 29th Giving the practical results of an extensive September and 6th October, 1933, Vol. 33, analysis of the detection of two modulated waves pp. 262-265 and 292-294.) of identical carrier frequency. Experimental work The principal features aré a single -valve fre- confirms the theoretical results, e.g. that time - quency changer and a duo -diode second detector delays of the order of 200 microseconds may pro- in which metal rectifiers (Westectors) are employed. duce serious distortion, and that a delay as small BATTERY ECONOMY WITH THE WESTECTOR " as 5o microseconds requires a 2 : I carrier ratio to prevent distortion. The investigation leads to the [applied to Existing Receiver]. -W. T. suggestion of supplying service to an urban area Cocking. (Wireless World, 24th November, Vol. by a number of low -power transmitters : to avoid 1933, 33, P 405.) the severe requirements of audio -frequency pro- DETECTOR INTERACTION [Causes and Elimination gramme distribution to these transmitters, the of Certain Whistles in Superheterodynes].- carrier would be modulated at a central point and G. J. Redfern. (Wireless World, 17th the modulated wave distributed over r.f. trans- November, 1933, Vol. 33, p. 398.) mission lines of equal lengths, or directly by radiation. BUILDING A WHISTLE FILTER. -W. T. Cocking. (Wireless World, loth November, 1933, RADIO RECEIVERS [Survey of Broadcast, Com- Vol. 372-373.) Naval Receiver Circuits, etc.]. 33, pp. mercial and - (Wireless M. Boella. (Alta Frequenza, August, 1933, HARMONIC DISTORTION. -D. A. Bell. 1933, Vol. Vol. 2, No. 3, pp. 42 I-464.) World, loth November, 33, PP. 378-379.) HEXODE CIRCUITS. Wigand. (Radio, PRACTICAL -R. World -Radio, 8th Sept., B., F. für Alle, Sept., 1933, PP. 397-404.) A BICYCLE CRYSTAL SET.-( 1933, Vol. 17, No. 424, p. 301.) AN ULTRA -SELECTIVE HEXODE SUPERHETERODYNE von THE LOUDSPEAKER IN THE HOME : ALTERNATIVE RECEIVER FOR 15-2 000 METRES. -H. 23rd der Bey. (Funktech. Monatshefte, September USE OF HEADPHONES. -(The Times, No. pp. Oct., 1933, p. 25.) 1933, 9, 367-371.) In the course of this short article the Wireless BY REDUCTION OF QUIESCENT ANODE CURRENT Correspondent remarks : " That the British wireless RECTIFYING PART OF INCOMING A.C. AND manufacturer does not generally provide a set in USING AS EXTRA GRID BIAS. -RCA. which the loudspeaker and telephones can be used (German Pat. 574 457, pub. 13.4.1933.) alternatively is really very remarkable." HINTS ON SHORT-WAVE RECEIVER DESIGN.--(World- AND AERIAL SYSTEMS Radio, 29th September, 1933, Vol. 17, AERIALS No. 427, pp. 406 and 408: to be continued.) HE REACTANCE OF BROADCAST RECEIVING AERIALS AND ITS INFLUENCE ON THE FUNCTIONING WHY NOT TRY THE DIODE ? [Additional Advan- OF ABSORPTION AND REJECTOR CIRCUITS besides Tonal Quality, compensating tages, [Wave Traps : Apparent Amplifying Effect of Valve]. -(World -Radio, for Need an Extra close to the True Adjustment : etc.]. - loth Nov., 1933, Vol. 17, No. 433, pp. 617- F. Klutke. (Hochf:tech. u. Elek:akus., 618.) September, 1933, Vol. 42, No. 3, pp. 99-105.) employed WHAT IS AN " EXPANDING " RECEIVER ? [3 -Circuit In many cases where wave traps are 3 -Valve Receiver convertible to 3 -Circuit the interfering signal strength is increased just 4 -Valve by switching-in a Second R.F. before the correct adjustment is reached. Some- Stage]. -Schaub. (Radio, B., F. für Alle, times this maximum occurs when the wave -trap than that for the October, 1933, PP. 476-477.) condenser is at a value greater true wave -trap action (" positive sign effect "), THE WIRELESS WORLD A.V.C. THREE.-( Wireless sometimes when it is smaller (" negative sign World, 13th and loth October, 1933, Vol. 33, effect "). Observations over the whole broadcast pp. 298-301 and 318-320.) scale show that, in general, with the lower fre- Difficulties in applying A.V.C. to receivers with quencies the " negative sign " is in evidence, overcome by the only a single r.f. stage are here unaffected by more or less accurate tuning ; with employment of the delayed amplified system of the high frequencies the same is true of the A.V.C. " positive sign " ; while with the intermediate WHY TUNE BY WAVELENGTH ?-R. W. Hallows. frequencies the sign can be changed at will by a (Wireless World, loth October, 1933, Vol. 33, alteration of the tuning. The writer gives investigation of these pp. 316-317.) theoretical and experimental The writer maintains that so long as stations phenomena and draws certain practical conclusions remain closely identified with their wavelengths or of interest for reception and test -room purposes. confusion is bound to arise when It has formerly been maintained that the effects frequencies, between wavelength changes, even of a minor nature, occur ; could be explained by a magnetic coupling he therefore puts forward a scheme for the abolition the inductance of the wave -trap and the receiving of the familiar scale in favour of numbered channels. circuit. Although this would, in certain circum- January, 1934 38 THE WIRELESS ENGINEER & stances, yield a voltage amplification, in most p. 167, l -h col.] the solution of various problems cases the possible coupling is too small to cause relating to the antenna system is greatly facili- such marked effects ; moreover, a decrease of such tated." The radiation reactance mentioned above coupling (e.g. by screening) has no appreciable affects both the velocity constant and the damping influence on the result. The writer's explanation, constant of the wave on the antenna wire. Experi- that the voltage rise is due to the introduction of a ments with a crystal -controlled generator are series resonance between the various reactances in described which confirm this theoretical result the aerial circuit, is consistent with all the observed also tests with aerials situated above ordinary results. He first gives the theoretical basis of this ground and above ground artificially metallised, hypothesis, and then describes its experimental showing that ordinary moist ground may be taken confirmation. One practical consequence of the as a conductive surface for short waves so far as work is to bring into prominence a method of " such aggregating quantities as radiation resistance increasing the selectivity of a simple receiver by and reactance are concerned." the simultaneous use of an absorption (or a rejector) circuit and a reactance circuit in series with the ON THE CALCULATION OF THE TOTAL RADIATION aerial. Another, and more important RESISTANCE IN A SHORT-WAVE DIRECTIVE application, ANTENNA [with Reflector].-H. Takeuchi. is in measuring technique : " it is shown in section V that the current strength (and thus the (Rep. of Rad. Res. in Japan, June, 1933, Vol. 3, I : voltage drop across No. Abstracts Section p. 2 : short a fixed resistance), in a circuit summary only of Japanese containing only dissipative resistances in paper.) See also addition Kato and Takeuchi, 1933 p. 505. to an absorption or rejector circuit, is (as follows Abstracts, from equation 9) a function of C (or I/C) which is THE FUNCTION OF THE REFLECTOR IN A SHORT- symmetrical with respect to the resonance point of WAVE DIRECTIVE ANTENNA.-Y. Kato and the wave -trap. It is thus possible to ascertain the H. Takeuchi. disappearance of the reactance of a circuit without (Ibid., p. 2.) " The formulas given are useful in laborious phase measurements, simply by examining determining the necessity or not of feeding the the current strength as a function of C or of 1/C for reflector in any directive antenna." symmetry with respect to the resonance point of THE SURGE IMPEDANCE OF A HALF -WAVE DIPOLE the wave trap : this can be done easily and with great accuracy." OF A BEAM ANTENNA.-T. Mizuhashi. (Ibid., pp. 2-3 : summary only of Japanese BROADCASTING TRANSMITTING AERIALS WITH VER- paper.) TICALLY CONCENTRATED RADIATION [LOW - The surge impedance is treated electrodynamic - Angle Radiation to avoid Near Fading : ally. " Considering all the current elements of Zeesen Short -Wave, Disc, Cylinder (Polygon) half -wave dipoles as Hertzian oscillators, the electric and One -Wire (Breslau) Medium -Wave force induced in each element is integrated along Aerials]. - O. Böhm. (Hochf:tech. u. the axis of the half -wave dipole from its mid -point, Elek:akus., October, 1933, Vol. 42, No. 4, which is in zero potential, to one end of it. The PP. 137-145.) surge impedance is derived directly from this See many past abstracts. With regard to the integrated voltage. The calculated value for the Zeesen aerial the writer suggests that such aerials surge impedance of a half -wave dipole is should be very useful for ultra -short (4-8 m) 3o sin h-1(A/d) - 49.47 + 954.95 waves. ohms, where A is the wavelength and d the diameter HORIZONTAL of the wire used in the dipole. The effects due to AERIAL SYSTEM WITH THE ADVANTAGE of OF HORIZONTAL the presence other half -wave dipoles have also POLARISATION [reducing been considered, and the results of calculations Zone of Silence] BUT WITHOUT MARKED DIRECTIVE shown." EFFECT. - SFR : Gouriaud. (French Pat. 749 288, pub. 21.7.1933 Rev. NOTE ON DIPOLE RADIATION THEORY.-W. H. : Wise. (Physics, October, 1933, Vol. 4, Gén. de l'Élec., 28th Oct., 1933, Vol. 34, No. 17, p. 134D.) No. Io, pp. 354-358.) A square of four insulated half -wave horizontal " By fitting certain general asymptotic series aerials, fed at the ends of one diagonal. solutions of the wave equation to known expressions for wave -function components at the surface of the THEORY OF THE COMPLEX [Short -Wave Beam] ground and on the upper infinite hemisphere, ANTENNA.-K. Tani. (Rep. of Rad. Res. in recurrence relations between the successive terms Japan, June, 1933, Vol. 3, No. 1, pp. 19-88 : of the asymptotic series for some of the dipole in English.) wave -function components are obtained." From author's summary :-" In this paper is proposed a general theory of the beam antenna of ON THE CALCULATION OF RADIATION RESISTANCE straight wires, based on the views as set forth by OF ANTENNAS AND ANTENNA COMBINATIONS : Léon Brillouin and developed by A. A. Pistolkors. ERRATUM.-Bechmann. (Proc. Inst. Rad. Useful tables for the design of beam antennas are Eng., September, 1933, Vol. 21, No. 9, p. 1367.) Correction to an equation added. . The paper emphasises the following in the paper dealt with in 1931 p. 556. points : (1) The theory is applicable regardless of Abstracts, the phase relation of the antenna current. (2) It THEORY AND PRACTICAL APPLICATION OF DIRECTED suggests that in the problem of the short-wave RADIATION.-Ochmann and Rein. (Hochf: antenna, radiation reactance is no more negligible tech. u. Elek:akus., August, 1933, Vol. 42, than is radiation resistance. (3) By introducing No. 2, pp. 68-72.) two quantities RAB and XAB [see 1932 Abstracts, Second and final part of the survey dealt with in EXPERIMENTAL WIRELESS 39 January, 1934
l -h col. The Telefunken a triode, by connecting a saturated diode in the Oct. Abstracts, p. 567, anode " fir tree," Marconi -Franklin, Sterba, Chireix- triode anode circuit and thus keeping the aerial systems are treated briefly. current constant, does not obtain the full effect Mesny and other intro- A section deals with reflectors, another with the because the filament battery for the diode influence of the ground on the directive effect. duces a capacity to earth. The present writers In the two parts together more than a hundred replace the diode by a caesium photocell with a literature and patent references are listed. saturation voltage of about 3o v and an emission, when illuminated by a 4o -watt lamp, of o. .0 FHA SHORT-WAVE AERIAL GIVING INCREASED GROUND They also use a the (Sewig, 1932, pp. 469-470). WAVE [Vertical Series of Sections, screen -grid valve instead of a triode. With a Lowest a Quarter -Wave Earthed Aerial, Telefunken RES 044 the calculated amplification the Remainder Half -Wave Dipoles]-Lorenz is 590 : owing to the incomplete saturation of the Company. (German Pat. 577 349, pub. photocell the actual value obtained was some 5% 29.5.1933: Hochf:tech. u. Elek:akus., Oct., lower. The anode current was 0.3-0.5 mA, which 1933, Vol. 42, No. 4, p. 147.) the photocell yielded easily for many hundreds SHORT-WAVE AERIALS FOR THE TRANSMISSION OF of hours. The range of anode -voltage variation CIRCULARLY POLARISED WAVES. Tele- was 15o v-enough for the control of a hot -cathode - is particularly funken and Hagen : Salto. (German Pats. cathode-ray tube. The circuit Nos. 568 346 and 569 073, pub. 18.1.1933 suitable for this purpose, owing to its small de- more suitable : Hochf:tech. u. Elek:akus., pendence on frequency. A still and 28.1.1933 with a June, 1933, Vol. 41, No. 6, p. 223.) valve is the RENS 1264, indirectly heated, penetration coefficient of only o. i % compared EFFECTIVE HEIGHT OF TRAILING AIRCRAFT AERIALS with the o.2% of the other valve. AS AFFECTED BY SPEED: COMPARISON (See WITH FIXED AERIALS.-Fassbender. TRANSMITTING VALVES FOR ULTRA -SHORT WAVES. abstract under " Miscellaneous.") -Kohl and Pintsch. (German Pats. Nos. 876, 7.2.1933 and BERYLLIUM AS MATERIAL FOR AIRCRAFT AERIALS. 569 745 and 569 pub. -Fassbender. (Ibid.) 9.2.1933.) The first patent deals with the use of an insula- TESTS ON TRANSMITTING AND RECEIVING AERIALS ting or semi -conducting anode in a retarding -field FOR ULTRA -SHORT [5.I Metre] WAVES.- valve, to reduce the grid/anode capacity. In the Muyskens and Kraus. (See abstract under second patent a spiral grid is closed by a strap to " Propagation of Waves," p. 3o.) form an oscillatory circuit : between this grid and AERIALS [Match- the outer concentric retarding cylinder lies a circle EXPERIMENTS WITH SHORT-WAVE cathode. At the Circuit : of hot cathodes or a single spiral ing Aerials and Receiver Input or a Comparison of Signal Strengths with In- centre there is either another hot cathode a small positive or negative verted -L and Dipole Aerials : etc.].- cold electrode at Microm. (World -Radio, 27th Oct. and potential. 1933, Vol. 17, Nos. 431 and 432, 3rd Nov., FOR ULTRA -SHORT-WAVE GENERATION 585.) TRIODE PP. 549 and [particularly for Retarding -Field Circuit : SCREENED AERIAL LEADS FOR BROADCAST RE- Grid wound on itself to form Closed Oscil- CEPTION.-A. Forstmeyer and W. Wild. latory Circuit].-Te-Ka-De : Pintsch. (Ger- (T.F.T., September, 1933, Vol. 22, No. 9, man Pat. 576 87o, pub. 17.5.1933 : Hochf: pp. 219-225.) tech.u.Elek: akus., Oct., 1933, Vol. 42, No. 4, Various types of construction are discussed : P. 148.) with different curves show the variations of capacity A CONTINUOUS factors (including the amount of eccentricity of the SPECIAL VALVES FOR GENERATING RANGE OF MICRO -WAVES FROM 13.5 TO 17.5 central conductor) : etc., etc. CENTIMETRES. - Muller. (See reference THE RECEIVING AERIAL AND ITS SCREENING.- under " Transmission," p. 33.) Monatshefte, W. Kautter. (Funktech. TUBES October, 1933, No. io, pp. 381-387.) NEW INTERMEDIATE -POWER TRANSMITTING [Types RK -18, 800 and 83o].-G. Grammer. QUICK AND NEARLY ACCURATE METHOD OF CAL- (QST, September, 1933, Vol. 17, No. 9, pp. CULATING THE ELEMENTS OF A CATENARY.- 33-34 and 68.) E. Mathieu. (Rev. Gén. de l'Élee., 23rd Sept., Of the RCA -800 it is mentioned that it is con- 1933, Vol. 34, No. 12, pp. 371-373.) servatively rated at 35 w output up to 6o Mc/s ; it will oscillate at 1.5 m in regular circuits. VALVES AND THERMIONICS A TRANSMITTING VALVE FOR ULTRA -SHORT WAVES. abstract, and be- VOLTAGE AMPLIFICATION USING SCREEN -GRID -Grammer. (See above VALVES WITH FULL UTILISATION OF THE low.) AMPLIFICATION FACTOR [" Constant Anode PUTTING THE TYPE 800 TRANSMITTING TUBE TO Current Method " : particularly suitable IN [Full WORK : HOW TO USE IT R.F. for Cathode -Ray Oscillography].-R. Sewig Wavelength] AND CLASS (Zeitschr. f. tech. Rating at 5 Metres and W. Kleinschmidt. B AUDIO CIRCUITS.-J. L. Reinartz. (QST, Phys., No. io, Vol. 14, 1933, pp. 388-390.) 1933, Vol. 17, No. 1I, pp. 27-30.) (Abstracts, 1931, pp. 41-42) November, Rudolph's method See also above. of obtaining maximum voltage amplification with January, 1934 40 THE WIRELESS ENGINEER &
THE SELECTION OF TYPES OF VACUUM TUBES AS A STUDY OF VACUUM TUBE CHARACTERISTICS [and SOURCES OF HIGH -FREQUENCY POWER [in- the Computation and Measurement of cluding Ultra -Short Waves]. -W. C. White. Fundamental and Second Harmonic Co- (Gen. Elec. Review, September, 1933, Vol. 36, efficients, etc.]. -S. Chiba and T. Sugi. No. 9, pp. 394-397.) (Rep. of Rad. Res. in Japan, September, 1933, NEW INFORMATION ABOUT THE COLD-CATHODE Vol. 3, No. 2, Abstr. Sec. p. 8 : abstract only of paper in : VALVE. -H. Keller : Hund. (Radio, B., Japanese in English.) F. Für Alle, October, 1933, pp. 449-450.) THE CALCULATION OF HARMONIC PRODUCTION For previous references to the Hund valve see IN THERMIONIC VALVES WITH RESISTIVE 1933 Abstracts, pp. 328 (r -h) and 274 (l-h column). LOADS [up to Sixth Harmonic].-D. C. The cathode consists of the glow -discharge elec- Espley. (Proc. Inst. Rad. Eng., October, trodes inside a perforated cylinder. The glow - 1933, Vol. 21, No. IO, pp. 1439-1446.) discharge potential is about 35 y for a rare gas THE filling, about loo v for air filling. CALCULATION OF MODULATION PRODUCTS The cylinder [for Valve potential is about 150 v higher. One or more Characteristicsl.-A. C. Bartlett. grids, concentric (Phil. Mag., Oct., 1933, Series 7, Vol. 16, with the cylinder, and a con- No. centric anode with a star -shaped cross section 107, pp. 845-847.) (" to Author's summary :-A modified form of Taylor's avoid asymmetries "), complete the valve. Theorem The material and surface of the electrodes have is derived which allows functions of cosines to be developed directly in series of cosines no effect on the action : even iron may be used. of multiple angles. This is applied to the deter- A COLD -CATHODE AMPLIFIER TUBE [Glow -Dis- mination of the modulation frequencies in a non- charge Tube with Amplification Factor linear device such as a thermionic valve. about 4 : suitable for A.F. Amplification or SURFACE CONDITIONS AND STABILITY Photocell Control]. -H. J. Reich and W. M. OF CHARACTER- ISTICS IN SCREENED -GRID TUBES. L. Hesselberth. (Electronics, October, 1933, p. -P. 282.) Copeland. (Journ. Franklin Inst., Oct., 1933, Vol. 216, No. 4, pp. 417-426.) THE CONSTITUTION OF GLOW DISCHARGES [Appli- This paper emphasises the influence of secondary cation to Thyratrons]. -H. Rothe and W. emission on the characteristics of screen -grid Kleen. (Naturwiss., 27th Oct., 1933, Vol. valves ; instability of characteristics is caused 21, No. 43, P. 772.) by the marked change in secondary emission with A high -frequency modulation of the stationary surface contamination. discharge current has been observed in thyratrons in the region of the pre -glow discharge, when THERMIONIC CATHODES FOR GAS -FILLED TUBES working with direct voltage. [Crimped Ribbon in Various Forms]. This seems to show E. F. Lowry. - that the dependent or semi -dependent discharges (Electronics, October, 1933, are built up of a number of electron groups. pp. 28o-281.) CONTRIBUTIONS TO THE IONISATION TIME OF THYRATRONS [and the Factors TUNGSTEN - THORIUM controlling It]. PROBLEM (Activation of Tungsten with -L. B. Snoddy. (Physics, Thorium Content). October, 1933, Vol. 4, No. IO, -E. Chalfin. (Hochf : pp. 366-371.) tech. u. Elek : akus., September, 1933, NE\V VALVES AND THEIR USES [Double -Diode - Vol. 42, No. 3, p. 105 : summary only.) Triodes, H.F. Pentodes, Class B Valves]. - An experimental checking and extension of (World -Radio, 3rd Nov., 1933, Vol. 17, Langmuir's researches. The assumption that at No. 432, Pp. 577-578.) maximum emission a monatomic layer is present (maximum THE CATKIN IN THE MAKING. (Wireless World, 3rd atomic heat of evaporation) is confirmed. November, 1933, Vol. Comparative measurements of the activation- and 33, pp. 358-360.) evaporation -velocities of thorium, at the same RECENT ADVANCES IN THE CONSTRUCTION OF temperature, show that the number of evaporating THERMIONIC VALVES [Transmitting, Re- atoms for O = r is only about 5-15% of the number ceiving, and Rectifying]. -C. Matteini. of atoms reaching the surface for O = o : whereas (Alta Frequenza, August, 1933, Vol. 2, Langmuir's " induced evaporation " theory demands No. 3, PP. 346-376.) equality. Other results not conforming with the THE LIEBEN VALVE PATENTS [and Their Expira- theory are found. tion].-(E.T.Z., 16th Nov., 1933, Vol. 54, THE EVAPORATION OF ATOMS, IONS AND ELECTRONS No. 46, pp. 1119-1120.) FROM CAESIUM FILMS ON TUNGSTEN. - A MAINS -DRIVEN VALVE TESTING INSTRUMENT J. B. Taylor and I. Langmuir. (Phys. FOR ALL TYPES OF VALVES. Review, i5th Sept., 1933, Series z, Vol. 44, -A. Hamm. No. (Funktech. Monatshefte, September, 1933, 6, pp. 423-458.) No. 9, pp. 357-362.) " Precision methods for measuring the number of caesium atoms adsorbed on tungsten are described. GRAPHICAL DETERMINATION OF THE DETECTION With these methods for determining O (the fraction CHARACTERISTICS OF A TRIODE [and Its of the tungsten surface covered with cs), the rates Special Superiority over Analysis when of atom, ion and electron emission are measured Signals are Very Large]. -Y. Fukuta and as functions of O and T, the filament temperature." E. Kido. (Rep. of Rad. Res. in Japan, The rate of atom evaporation, the heat of evaporation, September, 1933, Vol. 3, No. 2, Abstr. Sec. the production of electron and ion emission for pp. 8-9 : abstract only of paper in Japanese.) zero field, the work function, the condensation EXPERIMENTAL WIRELESS 41 January, 1934 coefficient, surface migration, the mechanism by the inclusion of caesium atoms in thick layers of evaporation and condensation, and transient of caesium oxide, a considerably greater emission effects are discussed and a " surface phase postulate" can be obtained than from caesium oxide layers is set up, " according to which all the properties with caesium ions adsorbed on the surface. A of the adsorbed film are uniquely determined by O new method of manufacturing cs2o layers con- and T." taining caesium atoms is given." EMISSION CHARACTERISTICS OF TUNGSTEN FILA- MENTS [Temperature and Emission Ripples DIRECTIONAL WIRELESS due to A.C. Heating : by Cathode -Ray Kuno. (Rep. [Long -Distance] FIELD -STRENGTH MEASUREMENTS Oscillograph Method]. -T. OF SHORT of Rad. Res. in Japan, September, 1933, AND DIRECTIONAL OBSERVATIONS WAVES. Nakai : Tsukada. (Rep. of 3, No. 2, 181-194.) -T. Vol. pp. Rad. Research in Japan, June, 1933, Vol. 3, FLUCTUATION NOISE DUE TO COLLISION IONISATION No. I, pp. 89-98 : in English.) IN ELECTRONIC AMPLIFIER TUBES [Theo- Short description (to be amplified later) of a field - retical and Experimental Investigation]. - strength measuring equipment with a frequency S. Ballantine. (Physics, September, 1933, range of nearly 4 to 15 Mc/s, together with an Vol. 4, No. 9, pp. 294-306.) account of its calibration. In conjunction with a vertical aerial it is used for measurements on THE THERMIONIC EFFECT AND ITS LAWS. -B. English, American and Australian stations, while Rossi. (Alta Frequenza, August, 1933, Vol. with Tsukada's improved goniometer-type direction 2, No. 3, PP 327-345.) finder (1933 Abstracts, p. 102, r-h col.), using an From the author's summary :-" Considering the aerial system consisting of " two sets of elemental electrons liberated from a metal as constituents of a Adcock aerials each having a vertical part of 4 perfect gas, and applying to them the Fermi metres and a horizontal part of 6 metres in length," statistics, an emission formula is obtained which and a hut raised off the ground, " directions may is in perfect agreement with experimental results. usually be determined within an error of about ± 2° The action of superficial impurities is traced to the and even in the most unsatisfactory condition within formation of an electrical double layer which 5°," the stations used in these tests being Rocky facilitates or impedes the escape of the electrons, Point and New Brunswick, Rio de Janeiro, and according as its positive face is turned towards the Buenos Aires. outside or the inside of the metal." In field -strength measurement the deflection of the final detector plate meter may be taken if A NEW [Experimental] METHOD FOR DETERMINING OF signals are strong enough. Otherwise an audibility THE THERMIONIC WORK FUNCTIONS a non -modulated signal no ITS APPLICATION TO NICKEL. meter is used. With METALS, AND - difference is found on the whole between the two G. W. Fox and R. M. Bowie. (Phys. Review, values 2, Vol. 44, No. 5, methods ; with a modulated wave the Ist Sept., 1933, Series obtained by the audibility meter are smaller, by an PP. 345-348) average of 5 db, than those given by the plate - THE CALCULATION OF THE WORK FUNCTION FROM circuit meter. For the records taken with the SIMPLE CONSTANTS OF THE MATERIAL. - apparatus here described, during the first period F. Rother and H. Bomke. (Zeitschr. f. Sept. to Dec., 1932, see ibid., F-oo to F-24. These Physik, 1933, Vol. 86, No. 3/4, pp. 231-24o.) include dotted curves giving the predicted field - A formula is found which gives a good quanti- strength values calculated by the method of tative representation of all work functions so far Namba and Tsukada (Abstracts, 1933, p. 497, l -h measured. column, Namba). Observations of " Polar echo " are also recorded (1932, p. 516, Namba). For the MEASUREMENTS ON CONTACT POTENTIAL DIFFER- second part of this paper see ibid., September, FACES OF ENCE BETWEEN DIFFERENT 1933, Vol. 3, No. 2, pp. F -23-F-52. COPPER SINGLE CRYSTALS.-B. A. Rose. (Phys. Review, 1st Oct., 1933, Series 2, Vol. HYSTERESIS OF THE VALVE GENERATOR AT DIFFER- 44, No. 7, PP- 585-588.) See also Farns- ENT HEIGHTS OF FLIGHT [in Airships, etc.]. - worth and Rose, 1933 Abstract, p. 631. H. Lowy. (Physik. Zeitschr., Ist Oct., 1933, Vol. 34, No. 1g, pp. 730-731.) WORK FUNCTION AND DISTANCE BETWEEN ATOMS. - previously made use of hysteresis W. Distler and G. Mönch. (Zeitschr. f. The writer has 84, No. and unstable oscillations in valve circuits, described Physik, 1933, Vol. 5/6, pp. 271-275.) by Appleton and Van der Pol (Phil. Mag., 1922), REMARK ON THE PAPER BY J. H. DE BOER AND to determine the distance of airships from the M. C. TEVES : THERMAL AND PHOTOELEC- ground (Physik. Zeitschr., 1925, Vol. 26, p. 649). TRIC EMISSION FROM CAESIUM/CAESIUM- In the present paper he extends the study to the OXIDE CATHODES AND THE INFLUENCE EX- discovery of the presence of water beneath the ERTED BY INCLUSION OF CAESIUM ATOMS airships to a depth of loo m if the airship is at a IN THE DIELECTRIC [and a New Method of height of 25o m above the ground. The phenomenon Manufacture]. -P. Görlich : de Boer and is due to the change of capacity of the antenna Teves. (Zeitschr. f. Physik, 1933, Vol. 85, with height above the ground and with the electro- No. 1/2, pp. 128-130.) magnetic constants of the ground. See also For the paper in question see 1933 Abstracts, Abstracts, 1930, pp. 55-56, and 1933, p. 640, l -h p. 573, l -h col. The present note shows " that, column. January, 1934 42 THE WIRELESS ENGINEER &
MEASUREMENTS OF DISTANCE FROM A REFLECTING A TRANSPORTABLE APPARATUS FOR THE MEASURE- WALL, BY MODULATED TRANSMISSIONS. - MENT OF REVERBERATION TIME AND SOUND R. Hell. (German Pat. 564 8oz, pub. INTENSITY. -J. Holtsmark and V. Tand - 3.5.1933 : Hochf : tech. u. Elek : akus., Oct., berg. (E.N.T., October, 1933, Vol. Io, 1933, Vol. 42, No. 4, p. 148.) No. Io, pp. 389-392.) A return to the principle of the earliest method DIRECTION FINDER WORKING ON AUDIBLE OR -the direct measurement of the time taken for INDICATED MAXIMUM [Maximum Difference the full sound to decrease to a value lower by a of Rectified Signals from Directional and definite Non -Directional amount. The new equipment functions Aerials].-R. Hell. (German as follows :-the sound from the loud speaker is Pat. 644, pub. 2.6.1933 Hochf : 577 : tech. received on a condenser microphone: the voltages u. Elek : akus., Oct., 1933, Vol. 42, No. 4, are amplified and rectified, 148.) and taken to a relay. P. When the current through the relay reaches a DVL WORK ON AIRCRAFT DIRECTION FINDING.- certain value the armature moves over, with the result that (I) the loud speaker is off, (z) DVL : Fassbender. (See abstract under cut the " Miscellaneous.") amplification is increased by a definite and fixed amount, and (3) a time -measuring instrument is A METHOD OF PROVIDING COURSE AND QUADRANT introduced and measures the time till the relay IDENTIFICATION WITH THE RADIO RANGE armature falls back. When the sound has decayed BEACON SYSTEM. -F. W. Dunmore. (Bur. so much that the armature is no longer held over of Stds. Journ. of Res., September, 1933, even with the increased amplification, the armature Vol. II, No. 3, pp. 309-325.) falls back and (4) cuts out the timing instrument, By cardioid directional identification signals (5) restores the amplification to its original lower (from the beacon's " transmission -line " aerial value, and (6) again starts up the loud speaker; system) such as 1 dot in westerly direction, 2 dots thus the whole cycle begins again. in easterly, and so on. The time measurement is carried out electrically, by measuring the potential across a condenser EQUI -SIGNAL GUIDING BEAM BY ALTERNATE charging through a resistance. In the circuit KEYING OF PASSIVE DIPOLES ON EITHER diagram of the whole apparatus, the last two valves SIDE OF EXCITED DIPOLE [as used for on the right, and the circuits between them, con- Ultra -Short -Wave Aircraft Beacon]. - stitute this timing circuit : the last valve has only Lorenz Company. (German Pat. 577 350, the task of indicating, by its anode -circuit milliam- pub. 30.5.1933: Hochf : tech. u. Elek : akus., meter, the mean of a number of observations. This Oct., 1933, Vol. 42, No. 4, p. 148.) See same milliammeter is used to measure the 1933 Abstracts, p. 162, l -h column. sound intensity when the apparatus is converted, by the turning of a switch, into an intensity RADIO BEACONS IN THE SERVICE OF AERIAL meter. NAVIGATION [Survey : including Inter- locking Signal, Rotating Field, Variable REVERBERATION MEASUREMENTS WITH A COM- Speed Rotating Fields (Loth), Aicardi, and PLETELY AUTOMATIC APPARATUS. -M. J. O. Leader Cable Systems]. -Mioche. (Ann. des Strutt. (Rev. d'Acoustique, January, 1933, P.T.T., October, 1933, Vol. 22, No. Io, Vol. 2, pp. 1-26.) See 1932 Abstracts, PP. 841-873.) P 529. RADIO -BEACON ORGANISATION ON THE NORTH PERFORATED STEEL SHEETS PASS SOUND WAVES EUROPEAN COASTS. -G. Meyer. (Telefunken - [Optically Reflecting but Sound -Passing Zeit., April, 1933, Vol. 14, No. 63, pp. 5 -II.) Domed Ceiling for Planetarium] -(Electronics, August, 1933, Vol. 6, No. 8, pp. 222-223.) DESCRIPTION OF THE RADIO APPARATUS FOR RADIO BEACONS AND FOR THEIR RECEPTION A COMPACT, ALTERNATING -CURRENT OPERATED BY SHIPS AT SEA. -A. Leib. (Ibid., pp. íI- SPEECH INPUT EQUIPMENT [for Broad- 16.) casting : with M.C. Microphone, Copper - Oxide Rectifier for Volume Indication, ACOUSTICS AND AUDIO -FREQUENCIES etc.]. -W. L. Black. (Proc. Inst. Rad. Eng., October, 1933, Vol. 21, No. Io, pp. 1409- THE ACOUSTIC PROPERTIES OF BROADCASTING 1418.) STUDIOS. -G. Lubszynski and H. Weigt. (Hochf : tech. u. Elek :akus., October, 1933, BEAT -FREQUENCY OSCILLATOR : A MAINS -OPERATED 42, Vol. No. 4, pp. 127-135.) INSTRUMENT PRIMARILY DESIGNED FOR TEST- (i) Loudness [comparison of conditions at the ING TALKING -PICTURE RECORDING APPA- microphone and at the ear] : (2) persistence RATUS AND COMMERCIAL AMPLIFIER EQUIP- [contrasted with reverberation time, which is of MENT. -M. F. Cooper and L. G. Page. much less importance in practice] : (3) the placing (Wireless Engineer, September, 1933, Vol. of the microphone : (4) : damping (5) distribution Io, No. Ito, pp. 469-476.) of damping : (6) stationary waves : (7) frequency dependence of damping : (8) types of microphone : [Two Simple] AUDIO -FREQUENCY VALVE OSCIL- (9) practical applications of results to the design LATORS FOR THE LABORATORY. -G. R. Todd. of ' talks " studios, medium, large and extra (Journ. Scient. Inslr., October, 1933, Vol. large studios. Io, No. Io, pp. 327-328.) EXPERIMENTAL WIRELESS 43 January, 1934
[Stretched Steel] STRING -CONTROLLED ALTERNA- analysis of a measured frequency curve is then TING-CURRENT SOURCE [using Special Car- given ; the satisfactory agreement between cal- bon -Disc Modulator]. -L. H. Stauffer. (Re- culation and measurement demonstrates the use- view Scient. Instr., September, 1933, Vol. 4, fulness of the equations and curve tables contained No. 9, PP. 483-485.) in the paper. A MAGNETOSTRICTION FILTER [70 C/S Band With DISTORTION CANCELLATION IN AUDIO AMPLIFIERS 20 000 c/s Resonant Frequency].-H. H. [Input and Output connected through High Hall. (Proc. Inst. Rad. Eng., September, Resistance : Voltage between Point on this 1933, Vol. 21, No. 9, pp. 1328-1338.) and " Earthy " Point amplified and fed For use in a harmonic analyser. Monel metal was back to Input Circuit]. -W. Baggally. used : the effects of different heat treatments are (Wireless Engineer, August, 1933, Vol. Io, discussed, and the design of coils and shields. A No. 119, PP- 413-419) single rod, supported at its mid -point, gave a band THE ACOUSTICAL PERFORAMNCE OF A CONE -TYPE c/s wide, 3o db up from the minimum : about 7o SPEAKER. A. two rods in series, coupled by a valve, gave a curve [Inductor Dynamic] LOUD -D. : Engineer, August, of the same width as much as 6o db up from the Oliver GEC. (Wireless minimum. 1933, Vol. 10, No. 119, pp. 420-429.) An investigation on the lines discussed in a A SIMPLE FREQUENCY BRIDGE. -Davies. (See previous paper (1931 Abstracts, p. loi). under" Measurements and Standards," p.48.) A PIEZOELECTRIC LOUD SPEAKER FOR THE HIGHER ELECTRICAL METHODS FOR THE PRODUCTION AND AUDIO FREQUENCIES [using Sawyer's MEASUREMENT OF MUSICAL FREQUENCIES " Bimorph " Rochelle Salt Units : for [particularly the Use of the " Robinson " Composite Reproducing Systems]. - S. Bridge]. -P. Nicolas. (Sci. Abstracts, Sec. Ballantine : Sawyer. (Proc. Inst. Rad. Eng., A, September, 1933, Vol. 36, No. 429, p. October, 1933, Vol. 21, No. Io, pp. 1399- 1029.) 1408.) For Sawyer's work see Abstracts, Io1, and 1933, A PHONIC MOTOR [for Frequencies up to 7 500 c/s]. 1932, p. p. 332. -Ikebe. (See under " Subsidiary Appa- LOUD SPEAKER WITH AUXILIARY WINDING IN ratus and Materials," p. 52.) SERIES WITH M.C. AND CLOSELY COUPLED TO FIELD WINDING : TO ELIMINATE MAINS ANALYSIS AND STUDY OF MACHINE NOISES. - Company. (U.S.A. J. F. Bouscasse. (Sci. Abstracts, Sec. A, NOISES. -Magnavox pub. 14.3.1933 : Hochf: August, 1933, Vol. 36, No. 428, 909-91o.) Pat. 1901 331, pp. tech. u. Elek:akus., September, 1933, Vol. THE VOLTAGE -TRANSFORMER IN THE L.F. AMPLI- 42, No. 3, p. 112.) FIER [Input and Inter -Stage Transformers]. TO ELEC- (Telefunken -Zeit., April, 1933, APPLICATION OF KENNELLY'S METHOD R. Gürtler. TRODYNAMIC LOUD SPEAKERS. -G. le Guen. Vol. 14, No. 63, pp. 29-53.) transformers (Sci. Abstracts, Sec. A, August, 1933, Vol. Author's summary :-Voltage 36, No. 428, (" grid " transformers), which in a l.f. amplifier p. 909.) have to amplify a broad frequency band, can be A NEW ALTERNATION PHONOMETER [for Studying represented, as is well known, by three equivalent Conditions for Apparent Equality of Loud - circuits : (1) at low frequencies, as an open Speaker Output, etc. : Analogous to Flicker circuited transformer, (2) at medium frequencies as Photometer]. -H. P. Knauss and F. E. a parallel -resonance connection and (3) at high Hale. (Review Scient. Instr., August, 1933, frequencies as a series resonance connection, of the Vol. 4, No. 8, pp. 447-448.) leakage inductance and transformer- and valve - capacities. From these equivalent circuits equations THE GREAT TELEFUNKEN LOUD SPEAKER EQUIP- are derived showing the relation between the con- MENT ON THE TEMPELHOFER FIELD, BERLIN stants of the amplifier stage and of the trans- [for a Crowd of I,]-2 Millions]. -(Telefunken - former on one hand, and the linear (amplitude) Zeit., April, 1933, Vol. 14, No. 63, pp. 53-55.) distortions on the other. These equations are the LOUD SPEAKER COST versus QUALITY [Comparison suitable both for the design calculation and 5" Types]. S. Knowles. The most im- of and if -H. analysis of transformer stages. (Electronics, September, 1933, PP. 240-242, portant formulae are reproduced in curve tables 256 and 26o.) See also 1933 Abstracts, p. for use. practical 447, 1-h column, " Back to Quality . . . Certain special cases are also dealt with : trans- former stages with series grid resistance, frequency AN ARTIFICIAL EAR FOR RECEIVER TESTING : curves without peaks (without positive linear dis- AN ARTIFICIAL VOICE FOR TRANSMISSION tortions) and with very high peaks. It is shown STUDIES. -F. L. Crutchfield : E. W. Holman. that for a given stage and a given permissible dis- (Bell Lab. Record, November, 1933, Vol. 12, tortion at the upper and lower limits of frequency, No. 3, pp. 81-84 : 85-88.) there is an (electrically) optimum transformer with inductance and maximum turns RECENT DEVELOPMENTS IN HEADPHONE DESIGN. minimum primary and M.C. Types]. M. ratio (and therefore maximum voltage magnifi- PART 2 [Ribbon -F. for such an optimum Colebrook. (World -Radio, loth and 27th cation). The design equations 43o and 431, transformer are derived, and a typical design cal- October, 1933, Vol. 17, Nos. culation worked out. As an example, the PP. 505, 507 and 542-543) January, 1934 44 THE WIRELESS ENGINEER &
A NEW CONDENSER MICROPHONE FOR MEASURING usual fluorescent screen is a purely optical effect AND RECORDING.-von Ardenne Laboratory. due to total reflection at the glass/air surface of (Hochf:tech. u. Elek:akus., April, 1933, Vol. separation. Its effect in television is very serious : 41, No. 4, p. 152.) the writer shows that in an ordinary tube it may limit : ELECTROSTATIC MICROPHONE WITH SOLID ELEC- the obtainable contrast to a ratio r 2 or I : 3 TRODE WITH NUMEROUS HOLES OF SUCH at best. Two principles for overcoming the difficulty are discussed : to make DEPTH THAT THE AIR COLUMNS HAVE A the circle of FREQUENCY ABOVE IO 000 CYCLES/SECOND. halation so small that it is practically of the same -G. Neumann. (German Pat. size as the spot itself, and to make it larger than 574 428, the useful part of the screen. Dealing first with pub. 12.4.1933 : Hochf:tech. u. Elek:akus., September, 1933, Vol. 42, No. 3, p. 112.) the second plan, the writer points out that for a glass/air surface the limiting angle for total reflec- THE CALIBRATION OF ELECTROSTATIC MICROPHONES. tion is about 45°, so that the radius of halation is -(Génie Civil, 16th Sept., 1933, Vol. 103, about twice the thickness of the glass wall ; thus No. 12, 288: summary only.) to make the halation diameter equal to the usual screen diameter would involve the use of a wall THE CONDENSER MICROPHONE [Equivalent Circuits : about 4 cm thick. Such a wall of glass would Mathematical Theory of Sensitivity, etc.: hardly be practicable, but the ordinary wall could Experimental Confirmation].-K. Kobayasi. be thickened externally by a layer of liquid of (Rep. of Rad. Res. in Japan, September, about the same refractive index as glass, the final 1933, Vol. 3, No. 2, pp. 194-207.) outer wall being again of thin glass (Fig. 3). NON-LINEAR DISTORTIONS OF [Carbon] MICRO- The first plan, to make the halation very small PHONES.-H. J. von Braunmühl and W. in diameter, is impossible where the fluorescent material is Weber. (E.T.Z., 2nd Nov., 1933, Vol. 54, fused deep into the glass or spread with No. 44, pp. 1068-1070.) the usual binding material : a modern spot is of The tests here described lead to the conclusion the order of 0.5 to I.o mm, and therefore a wall that, for a description of the performance and the thickness of about o.i mm would be necessary, judging of the merit of a microphone, it is not which would not stand atmospheric pressure. sufficient to give the strength of the combination This difficulty can be overcome by depositing the screen on the glass tones for a few arbitrary primary frequencies : the not wall, but on a very thin non -linearity must be known over the complete transparent carrier (e.g. a mica disc) close to, but range of frequencies and intensities. separated from, the glass wall. Old methods of using such a separate screen carrier gave a gap of THE PRESENT POSITION OF HOME -RECORDING OF several mm and produced distortions due to slight GRAMOPHONE RECORDS. - H. Kluth. flaws in the glass wall : it was, indeed, for this (Funktech. Monatshefte, September, 1933, reason that in recent tubes the screen has been No. 9, pp. 351-354.) deposited on the glass itself. But by making the gap very small, " SOUND HANDWRITING " [Synthetic Sound].- only just large enough to prevent actual contact, this trouble is avoided and halation W. Saraga : Pfenniger : Fischinger. (Funktech. overcome (Fig. 4). Such a method is not only Monatshefte, October, 1933, more No. Io, pp. 403-406.) See also 1933 practical than that of Fig. 3 but is also Abstracts, p. 332 (two). optically superior, since the light ray after passing through the wall takes up its original line, so that AEF PROVISIONAL RESOLUTIONS ON ACOUSTICAL a much higher percentage of the total luminous TERMS AND DEFINITIONS.-(E.T.Z., Ioth output reaches the aperture of an external lens. August, 1933, Vol. 54, No. 32, pp. 783-784.) A " compromise solution " of the halation Including definitions of " Reflexionsgrad," difficulty is given by keeping the fluorescent " Schluckgrad " (degree of " swallowing -up "), particles to the surface of the glass wall instead " Absorptionsgrad " and " Durchlassgrad." These of fusing them into it (cf. Figs 5a and b). For are respectively the ratios of the reflected sound many purposes sufficient freedom from halation energy, the energy not returned, the absorbed is given by depositing the particles " loosely " on energy, and the transmitted energy, all to the the surface of a thin binding layer with a refractive incident energy. index as small as possible : this plan has for some years been used in the writer's television receiver CONTRIBUTIONS TO THE THEORY OF OLD AND NEW tubes. Finally, halation troubles can be TYPES OF PIANO [particularly the Sound avoided by making the screen transparent : in this case Qualities given by various Hammer Actions, the light totally reflected including the " Micro -Hammers " used in from the glass/air surface either penetrates the screen or is again totally the Neo-Bechstein].-S. Sawade : Nernst. reflected by it, and in the latter (if (Zeilschr. f. tech. Phys., No. 9, Vol. case the screen 14, 1933, refractive index is suitably chosen) is prevented, PP. 353-362.) by multiple total reflections, from producing halation trouble. Unluckily PHOTOTELEGRAPHY AND TELEVISION up to the present no transparent screen (e.g. uranium glass) of high THE SERIOUSNESS OF HALATION [LiChthOfStÖrung] efficiency has been found. The writer concludes IN CATHODE-RAY TUBES, AND ITS ELIMINA- by pointing out that the troubles discussed do not TION.-M. von Ardenne. (Hochf:tech. u. exist, or can always be overcome, in screens which Elek:akus., October, 1933, Vol. 42, No. 4, are viewed directly : thus screens deposited on PP. 113-115.) metal are completely free from halation (see next The halation round the luminous spot on the two abstracts). VIRELESS 45 January, 1934
tt Pti y CY CATHODE-RAY TUBE: NOISE AS A LIMITING FACTOR IN AMPLIFIER DE- 4ZG A PROJECTING OSCILLO - SIGN. --O. E. Keall. (Marconi Review, 4 Path to avoid Electron Sept./Oct., 1933, No. 44, PP 5-12.) ses " : Conducting Screen Completion of the paper dealt with in 1933 4,74,53.0.Y2Z0lcr+ S,'Anode, to avoid Loss of Abstracts, p. 631, l -h column. Measurements on p+44A tnting Screen for Frontal a Io c/s -too kc/s television amplifier are included, o`Sta and Projection]. -M. von and there is a long appendix on the shot effect. Engineer, , No. zz, THE KERR CELL AND ITS APPLICATION TO TELE- °fie pp. VISION [and the Marconi Company's Multiple S IN THE FIELD OF CATHODE- Kerr Cell and Optical System for Projector PMENTS FOR MEASURING PUR- Receiver]. -N. Levin. (Marconi Review, L TELEVISION. -M. von Ardenne. Sept.,/Oct., 1933, No. 44, PP. 13-21.) . Monatshefte, September, 1933, Further development of the system referred 333-340) to in 1933 Abstracts, p. 573, l -h column. n of deflection due to earth's KERR CELL BIASED BY DOUBLY REFRACTING by slight magnetisation of the anode MICA SCREEN.-Hoyer : Pungs and Vogler. .rode of magnetic material) : elimina- (See under " Measurements and Standards.") -point error " (thus removing one of ims of the high-vacuum tube in com- IMPROVED KERR CELL FOR PROLONGED WORKING. 1 gas -concentrated tubes) : cathode -T. W. Case. (French Pat. 748 285, pub.
y use of platinum as carrier, and design 1.7.1933 : Rev. Gén. de l'Élec., 28th Oct., , give very sharply defined spot : a new 1933, Vol. 34, No. 17, p. 133 D.) xet tube (Figs. 2, 3 and 4) : new tubes for THE CRYSTAL CELL. H. Traub : von Okolicsanyi. ...dl observation projection without dis- -E. and (Wireless World, loth Oct., 1933, Vol. 33, ..ortion (see two preceding abstracts) : etc., etc. PP. 323-324.) " LINE MODULATION " [Thun Variable Spot -Speed Description of the new zinc sulphide crystal Modulation Method] IN TELEVISION. -(Funk - light modulator which has been developed for Magazin, August, 1933, Vol. 6, No. 8, pp. television purposes by von Okolicsanyi (1933 521-525.) See also von Ardenne, 1933 Abstracts, p. 63o, r -h col.). A summary of its Abstracts, pp. 46-47. advantages over the ordinary nitro -benzol Kerr cell is also given. NOTES ON TELEVISION DEFINITION [Number of Lines needed for Various Scenes under NOTE ON NEW METHODS TO MODULATE LIGHT. - Various Conditions]. -W. H. Wenstrom. G. Wataghin and R. Deaglio. (Proc. Inst. (Proc. Inst. Rad. Eng., September, 1933, Rad. Eng., October, 1933, Vol. zI, No. Io, Vol. 21, No. 9, pp. 1317-1327.) PP. 1495-1496.) See 1933 Abstracts, p. Io6. (1931 Using Gannett's method of analysis GAS DISCHARGE TUBES AND THEIR APPLICATION Abstracts, p. 331, r -h col.) extended to higher TO TELEVISION : WITH DISCUSSION. L. orders of definition and to more comprehensive -N. Harris : GEC. (Journ. Television Soc., scenes. Among the conclusions arrived at are :- March, 1933, Series z, Vol. I, Part 7, pp. 8o -12o -line two-way telephone television is now 217-226.) The full paper, a summary of technically possible and adequate for the purpose which was referred to in 1933 Abstracts, this applies also to 12o -zoo -line theatre projection p. 278, r -h column. of electrically transmitted news films. 400-800 -line theatre television, equivalent to the standard TRANSMISSION OF LIGHT BY A FLEXIBLE UNIT cinema, appears to be a practical impossibility at OF QUARTZ. -H. Dejust and E. Perrin. present : this applies also to 200 -400 -line home (Sci. Abstracts, Sec. A, July, 1933, Vol. 36, television, suitable for continued universal enter- No. 427, p. 793.) tainment, though izo -line home television appears technically possible now for short ranges, and gives INVESTIGATIONS ON CUPROUS OXIDE PHOTOCELLS. fair to good results for faces, small groups, etc. A CONTRIBUTION TO THE PROBLEM OF THE BARRIER -LAYER PHOTOELECTRIC EFFECT. - TELEVISION TRANSMISSION OVER A LIGHT BEAM W. Bullan. (Physik. Zeitschr., 15th Oct., AT BRITISH ASSOCIATION MEETING. -Marconi 1933, Vol. 34, No. 20, pp. 745-756.) Company. (Electrician, 8th Sept., 1933, Author's summary :-The factors to be con- Vol. III, No. 2884, p. 299.) sidered in the use of cuprous oxide photocells for practical measurements (spectral sensitivity, maxi- TELEVISION PROGRESS.-(Wireless World, 6th and mum efficiency factor and temperature dependence) 13th October, 1933, Vol. 33, pp. 288-290 are discussed and investigated. The nature of the and 302-304.) metal of the electrode from which the current TELEVISION AT THE BERLIN RADIO EXHIBITION, is taken has no influence on the position of the 1933.-G. Kette. (Funktech. Monatshefte, selective maximum of the effect. Gold -sputtered October, 1933, No. Io, Supp. cells are used to show that the direction of the pp. 53-61.) photoelectric current depends on the wavelength THE FERNSEH COMPANY'S CONTINUOUSLY WORKING of the incident light. The most favourable thickness INTERMEDIATE-FILM TELEVISION PROJEC- of the copper oxide layer for an optimum current TION RECEIVER FOR 3 X 4 -METRE PICTURES. yield is found to be o.1 mm for all wavelengths in -G. Schubert. (Ibid., pp. 62-63.) the visible spectrum. It is possible to exert an D January, 1934 46 THE WIREI SS arbitrary influence on the temperature character- with Deaglio's result, that -4 istic of the photoelectric current by choosing electrolytic conductors under; different metals for the electrode. Complete Gtk, THE ELECTRICAL CONDUCTIVI Le independence of the temperature may be attained TALS [for Photoelectric`+osfals ' in a wide range of temperature. W. Lehfeldt. (Zeitschr. of be 85, No. 11/12, PREDICTION OF THE PHOTOELECTRIC POWER OF Vol. pp. 7I7. 444 e CERTAIN BODIES FROM THE STRUCTURAL MEASUREMENTS ON CONTACT POTE C,. NUMBER ATTACHED TO THE FORMULA OF ENCE BETWEEN DIFFERENT YS. THESE BODIES. -H. Spindler and R. Coustal. COPPER SINGLE CRYSTALS. -B (Comptes Rendus, 30th Oct., 1933, Vol. 197, (Phys. Review., Ist Oct., 1933, No. 18, pp. 982-984.) Vol. 44, No. 7, pp. 585-588.) In spite of the similar natures of cucl, cusr Farnsworth and Rose, 1933 Abstract and cul, only the second displays a clear photo- electric effect analogous to that of cu2o in the THE GLOW -DISCHARGE LAMP AS A PHOTOELI usual copper/copper-oxide cell. This result is CELL. -K. Mahlmann. (Radio, B., . explained by the writers according to Spindler's Alle, November, 1933, pp. 502-506.) table of elements, resembling the periodic table, PHOTOCELLS IN THEIR TECHNICAL FIELDS C but with atomic indices quite different from the APPLICATION, and INDUSTRIAL PLANTS USING atomic numbers. The cusr cell has a sensitivity PHOTOCELLS. -L. Weisglass : H. Keller. about three -fifths of that of a good cu2o cell of the (Funk -Magazin, August, 1933, Vol. 6, same size, but deteriorates under prolonged 8, No. pp. 486-491 : 492-498.) action of light. The first paper includes a description of the ion a AND Geiger -counter provided with photosensitive BARRIER -LAYER PHOTOELECTRIC EFFECT layer (Rajewsky, 1931 Abstracts, p. 276,1-h col.), EINSTEIN'S RELATION. -F. VOR Körösy and 15th and used as a light detector with a sensitivity P. Selényi. (Physik. Zeitschr., Sept., Io 000 times as great as that of the eye. 1933, Vol. 34, No. 18, pp. 716-718.) The writers have previously found that differ- COMBINED PHOTO AND AMPLIFIER TUBES. -H. A. ently coloured illuminations produce different Mcllvaine. (Electronics, August, 1933, Vol. effects on barrier -layer photoelectric cells (Ab- 6, No. 8, p. 224.) 1932, pp. 231-232 and 469). Other writers stracts, REMARK ON THE PAPER BY J. H. DE BOER AND have not found this (Goldmann and Lukasiewitsch, Gleason, M. C. TEVES : THERMAL AND PHOTOELECTRIC 1933, pp. 220-221 and 221: 5933,15 47, EMISSION FROM CAESIUM/CAESIUM-OXIDE l the discuss the -h column). In this note writers CATHODES AND THE INFLUENCE EXERTED which the effect is to be expected. conditions under BY INCLUSION OF CAESIUM ATOMS IN THE LOW -RESISTANCE SELENIUM PHOTOCELL: VERY DIELECTRIC [and a New Method of Manu- THIN METALLIC AND INSULATING RIBBONS facture].-Görlich. (See under " Valves WOUND AND DIPPED IN SHELLAC, ONE EDGE and Thermionics," p. 41.) THEN POLISHED. -C. Chilowsky. (French GENERAL PROPERTIES OF PHOTOELECTRIC CATHODES pub. 236.1933 Rev. Gén. Pat. 747 791, : [Survey, including Recent Types of Photo- de l'Élec., 3oth Sept., 1933, Vol. 34, No. 13, cell : with Characteristic Curves]. -G. p. 103 D.) Déjardin. (Rev. Gén. de l'Élec., 21st and CONTRIBUTIONS TO THE CRYSTAL PHOTOELECTRIC 28th Oct., 4th and 11th Nov., 1933, Vol. 34, EFFECT [Preliminary Communication]. -G. Nos. 16, 17, r8 and 19, pp. 515-526, 555-566, Mönch. (Naturwiss., loth Oct., 1933, Vol. 591-607 and 629-637.) 21, No. 42, pp. 751-752.) THE CAESIUM -OXYGEN -SILVER PHOTOELECTRIC CELL The writer did not observe the crystal photo- [Properties and Method of Manufacture]. - electric effect with artificial, glass -clear single crys- M. J. Kelly. (Bell Lab. Record, October, tals of cuprous oxide. All natural substances 1933, Vol. 12, No. 2, pp. 34-39.) investigated in which the crystal photoelectric effect was observed, with the exception of cinnabar, had MEASUREMENTS AND STANDARDS the negative pole for the thermo-element, while with artificially treated substances the positive pole was THE VISUAL RECORDING OF RESONANCE CURVES the warm one. [of Broadcast Receiver Circuits or Complete Amplifiers]. -G. Ulbricht : Schuck. (Hochf: REMARK ON THE PAPER BY R. DEAGLIO : " PHOTO- tech. u. Elek:akus., October, 1933, Vol. 42, ELECTRIC EFFECT IN SINGLE CRYSTALS OF No. 4, PP 135-137.) CUPRITE." -G. Mönch and R. Stühler : The writer first gives an outline of the RCA - Deaglio. (Zeitschr. f. Physik, 1933, Vol. 85, Victor apparatus described by Schuck (1933 No. 1/2, pp. 131-134.) Abstracts, p. 39, l -h col.) : this may employ an For Deaglio's paper see 1933 Abstracts, p. 573, oscillograph, though the writer indicates that in r -h col. Also cf. Joffé, ibid., just above, and the back Germany it is more usual to rely on maximum references there given ; also Nasledow and Neme - meter readings. He considers the equipment rather now, ibid., p. 400. The writers of the present note complicated and expensive, and goes on to describe have made experiments on the variation with time a simpler arrangement employing a cathode-ray of the magnitude of the crystal photoelectric effect oscillograph without the usual elaborate relaxation - in single crystals of cuprite ; these do not agree oscillation time base. This latter device is only EXPERIMENTAL WIRELESS 47 January, 1934
necessary when the frequency -controlling rotating electrode capacities and valve emission and inde- condenser varies its capacity in proportion to time, pendent also of the crystal damping." See also so that to obtain stationary images a time -pro- next abstract. portional horizontal -axis deflection is required. By driving the rotating condenser by a synchronous NEW TEMPERATURE -COMPENSATED QUARTZ OSCIL- motor, and by suitably designing the shape of its LATORS [with Temperature Indicating and Coils inside the Con- rotating plates so that the capacity varies sinusoi- Regulating Evacuated tainer].-R. Bechmann : Telefunken Com- dally with time, the writer is able to use the 5o c/s mains to pany. (E.N.T., September, 1933, Vol. Io, voltage provide the horizontal deflection. No. Or a rotary off 9, pp. 371-376.) converter driven d.c. mains may The oscillators here described are of the type have the " sine -wave " condenser plates mounted used in the on its axis, while it also provides the sinusoidal Langenberg broadcasting station (Semm, 1933 Abstracts, p. 54, 1-h col.) The writer voltage for the horizontal deflection. shows first that the ordinary Pierce oscillator circuit THE DELINEATION OF RESONANCE CURVES BY A is subject to frequency fluctuations, due to small MIRROR OSCILLOGRAPH AND A SECOND voltage changes, which can be kept down to below MIRROR MOUNTED ON THE SPINDLE OF THE 2 X 10-e. In the Heegner two -valve circuit VARIABLE CONDENSER OR VARIOMETER.- (Fig. 3) a frequency is excited for which the crystal A. Meir and R. Hinkelmann. (E.T.Z., 26th has a minimum resistance, and the effects of capa- Oct., 1933, Vol. 54, No. 43, pp. 1051-1052.) cities parallel to the crystal are eliminated (Tele- funken Pat., 1933 Abstracts, p. 576, 1-h col.) ; but A CONTINUOUS [Mains -Driven] RECORDER OF RADIO even FIELD this circuit is subject to the above -mentioned INTENSITIES.-K. A. Norton and variations. on voltage, S. E. Reymer. (Bur. Skis. The dependence anode of Journ. of Res., however, is decreased by keeping the oscillator September, 1933, Vol. I I, No. 3, pp. 373-378.) damping low ; for reason, Using a potentiometer recorder (Brown, or this among others, the Leeds quartz container is evacuated. Frequency fluctua- and Northrup) in a bridge circuit, to record tions due to vibration or jars are reduced below the plate resistance of the first valve in the i.f. 2 x to-7 by the stable method of mounting the amplifier of a superheterodyne receiver with AVC. eliminate quartz plate. By means of the special thermo- To variations due to power-supply vol- static arrangement surrounding the crystal and tage fluctuations, one of the three bridge -arm inside the (Telefunken and Bechmann, resistances is the plate resistance of a similar valve. container 1933 Abstracts, p. 28o, I -h col.) and the bridge and Some specimen results on broadcast transmissions amplifier circuits with which combines to give are given. The paper was read at the 1933 URSI it Meeting. continuous regulation, the temperature is kept constant within about I/20°C. " By special FIELD -STRENGTH MEASURING [and the B.B.C. measures not dealt with here the temperature " Counting Recorder " giving Total Time constancy can be made appreciably greater even during which Signal Strength exceeds than this." With the usual type of crystal, cut Each of Ten Predetermined Values].- perpendicular to the electrical axis, and having (World-Radio, 6th October, 1933, Vol. 17, a temperature coefficient of 20 x to-, per i °C, this No. 428, PP 433-434.) regulation gives a constancy better than I x Io e. [Long-Distance] FIELD -STRENGTH MEASUREMENTS PIEZOELECTRIC CRYSTAL MOUNTING WITH TEM- AND DIRECTIONAL OBSERVATIONS OF SHORT PERATURE COMPENSATION [Electrodes held WAvEs.-Nakai : Tsukada. (See under apart by Ring of Greater Expansion Co- " Directional Wireless.") efficient].-Bechmann and Osnos. (German PIEZOELECTRIC OSCILLATOR, PIERCE'S CIRCUIT Pat. 574 456, pub. 18.4.1933 : Hochf:tech. [Linear Theory, and Practical Discrepancies u. Elek:akus., September, 1933, Vol. 42, No. 3, due to Grid/Cathode Capacity Variations p. III.) produced by Space Charge].-K. Heegner. PIEZOELECTRIC QUARTZ OSCILLATORS WITH ARBI- (E.N.T., Sept., 1933, Vol. so, No. 9, pp. TRARY TEMPERATURE COEFFICIENTS, IN 357-371) PARTICULAR ZERO.-R. Bechmann. (Natur- " To sum up it can be stated that for a Pierce wiss., 20th Oct., 1933, Vol. 21, No. 42, p. oscillator, according to the linear theory, a valve 752.) of steep slope and small penetration coefficient is The oscillators are cut with calculable angles of desirable. But the steeper the slope the more inclination of the normals to the surfaces to the marked is the grid/cathode capacity variation optical axis of the crystal. produced by the space charges in the valve. Loose coupling between anode circuit and grid circuit ON TOURMALINE OSCILLATORS.-S. MatSumura improves, to a limited extent only, the dependence and S. Ishikawa. (Rep. of Rad. Res. in of the frequency on the tuning of the anode circuit Japan, June, 1933, Vol. 3, No. I, pp. 1-5 [under some conditions a reduction off the anode/ in English.) grid capacity may actually cause a deterioration " For high -frequency use it is best to cut a thin of frequency constancy, and a certain strength of plate so that its surfaces shall be perpendicular coupling is necessary to counteract the effect of to the optic axis, and to apply the alternating small changes in the damping of the crystal on the electric field along the Z-axis." In this case, amplitude of the vibrations]. resonance oscillation will occur with longitudinal It still remains to design an oscillator which shall mode of vibration, its frequency being given by - possess a definite frequency independent of the f = 1/2 1, . V e33/p, where 4 and c33 are the length D 2 January, 1934 48 THE WIRELESS ENGINEER & and the adiabatic elastic constant in the direction micrometer : the galvanometer is in the anode of the Z-axis, and p is the density (cf. Koga, 1933 circuit of a retarding -field micro -wave generator, Abstracts, p. 5o). " The physical properties of the and an opposing e.m.f. is derived from a potentio- tourmaline may differ slightly with the variety of the meter across the filament battery instead of from crystal. Although their numerical values as a whole the additional battery used by Dowling. The cannot be given here, if we take c33 = 160.63 X Io10 writer's method of measuring the micro -waves is dynes/m-12 and p = 3.12, the wave constant, that to set up stationary waves between the dipole and is the ratio of the wavelength in metres to the a reflecting sheet of metal, and to explore the field thickness in millimetres, may be found from the with a mounted resonator rod : as this passes from above formula to be about 83.62 m/mm, which is antinode to antinode, large galvanometer deflec- smaller than that of the X -wave in X -cut quartz tions occur in a very sharply defined way, and the plates." wavelength is found by measuring the intervals. With a 7 -metre push-pull oscillator (crystal The potential antinodes can also be indicated by a between the grids) the frequency variation with loud -speaking telephone connected across an ad- change of filament voltage from 3.6 to 6 IT, or change justable voltage -regulating resistance inserted, for of plate voltage from 150 to 90 v, was within the instance, in the positive h.t. lead to the grid. The order of 0.001%. The frequency changes slightly writer goes on to describe the use of various types of with the capacity of the tuning circuit, the variation radiometric condensers and inductances (using increasing as the capacity gets large. The fre- a mercury thermometer or thermostatic bimetal quency also varies (by about -32 x io -5) when strip) which can be placed close to the oscillating a condenser introduced in parallel with the crystal dipole. Heat radiations then have the effect of is increased from 6 to 13 µµF : the amplitude de- gradually throwing the resonator into tune, pro- creases simultaneously. Care must therefore be ducing a maximum of galvanometer deflection. taken to avoid unnecessary capacity here. The RADIATION RESISTANCE OF CONCENTRIC -CONDUCTOR is 0.004% between 2o° temperature coefficient - TRANSMISSION LINES [and Comparison with and 48°C. See also 1933 Abstracts, p. 514, r -h Parallel Lecher Wires : for use in Micro - column -two. Wave Oscillator Circuits].-Whitmer. (See FREQUENCY STANDARDISATION BY INTERNATIONAL under " Transmission.") (Sci. Abstracts, COMPARISON. -A. Wainberg. AN EXTENSION OF A MAXWELL MUTUAL -INDUCT- 36, No. Sec. B, September, 1933, Vol. 429, ANCE FORMULA TO APPLY TO THICK SO- P. 587.) LENOIDS. -H. B. Dwight and S. H. Chen. A PRECISION METHOD OF ABSOLUTE FREQUENCY (Physics, September, 1933, Vol. 4, No. 9, MEASUREMENT. -H. Kono. (Rep. of Rad. pp. 323-326.) Res. in Japan, September, 1933, Vol. 3, in THE HIGH -FREQUENCY MAGNETIC FIELD OF A No. 2, pp. 127-136.) The full paper, FLAT SPIRAL COIL [compared with the D.C. of which was referred English, a summary Field]. -S. Githens, Jr., and O. Stuhlma.n, to in 1933 Abstracts, p. 49, r -h column. Jr. (Review Scient. Instr., October, 1933, A SIMPLE FREQUENCY BRIDGE [Modified Hughes Vol. 4, No. 10, pp. 542-545.) Extension of Balance].-R. M. Davies. (fount. Scient. the work dealt with in 1933 Abstracts, Instr., September, 1933, Vol. Io, No. 9, p. 35, 1-h column. PP. 274-276.) A QUASI -STATIONARY CALCULATION OF THE Author's abstract :-It is shown that a simple NATURAL WAVELENGTHS OF SINGLE -LAYER of the well-known Hughes balance modification FLAT AND CYLINDRICAL COILS. -H. Zuhrt. leads to a useful frequency bridge, which, under (Archiv f. Elektrot., 4th Oct. 1933, Vol. 27, certain conditions, can be balanced by a single No. io, pp. 729-742.) adjustment. The bridge was tested against a Completion of the paper referred to in Nov. phonic motor, and the results obtained are within Abstracts, p. 633, r -h col. the limits of accuracy of the apparatus, namely I part in I 000. SELF-INDUCTANCE IN THE CASE OF DISTORTION OF THE CONDUCTING CIRCUIT. - R. Riihle : AUTOMATIC TEMPERATURE COMPENSATION FOR Dunton. (E.T.Z., 17th and 31st Aug., 1933, THE [" Micrometer "] FREQUENCY METER. Vol. S4, Nos. 33 and 796-798 and -G. F. Lampkin. (QST, October, 1933, Vol. 35, pp. 17, No. Io, pp. 16-19, 58 and 6o.) 843-845.) NOTE ON A MODIFIED REACTANCE/FREQUENCY B -BATTERY -LESS OSCILLATORS FOR USE WITH CHART [modified by Addition of Inverted HETERODYNE WAVEMETERS. - Ishikawa. Scale graduated in Micromhos for reading (See abstract under " Transmission.") Susceptances].-J. R. Tolmie. (Proc. Inst. MODULATED PENTODE OSCILLATOR.-( Wireless Rad. Eng., September, 1933, Vol. 21, No. 9, World, 25th August, 1933, Vol. 33, p. 183.) pp. 1364-1366.)
ULTRA -SHORT WAVES : 60 CM ZERO -SHUNT CIRCUIT MEASURING INDUCTANCE WITH A RESISTOR [Owen -NEW METHODS FOR MEASUREMENT - Bridge, with Resistance in One Ratio Arm CONTROL BY RADIOMETRIC CONDENSERS and Capacitance in the Other, brought into AND INDUCTANCES. -G. G. Blake. (Elec- Commercial Use by Design of Reactance trician, 8th Sept., 1933, Vol. Iii, No. 2884, independent of Frequency and by Screening pp. 279-280.) Scheme]. -T. Slonczewski. (Bell Lab. The zero -shunt circuit referred to is a modi- Record, November, 1933, Vol. I2, No. 3, fication of that used by Dowling in his ultra - PP 77-80.) EXPERIMENTAL WIRELESS 49 January, 1934
THE MEASUREMENT OF VERY SMALL INDUCTANCES turbances and these may be still further eliminated [0.1 Microhenry, with Inaccuracy not ex- by the introduction of a differential galvanometer. ¡%, in spite of presence of Resist- ceeding THE ELECTRO -OPTICAL KERR EFFECT AS A MEANS 4 5 : ances as high as or Ohms Substitution OF MEASURING VOLTAGE AND CURRENT AT Method, using 25 Mc/s Frequency].-C. L. VERY FREQUENCIES [Wavelengths Fortescue. (Journ. Scient. Instr., October, HIGH down to about 14 Metres].-H. Hoyer : 1933, Vol. io, No. io, pp. 301-305.) Pungs and Vogler. (Archiv f. Elektrot., ON A METHOD OF DETERMINING THE COEFFICIENT 4th Oct., 1933, Vol. 27, No. io, pp. 691-708.) OF MUTUAL INDUCTION, MEASURED AS SELF- Investigation and further development of the INDucTION.-L. M. Chatterjee. (Physik. Pungs-Vogler method (193i Abstracts, p. 567, Zeitschr., i5th Sept., 1933, Vol. 34, No. 18, l -h col.). The sensitivity is increased by biasing pp. 711-712.) the working point to the straight part of the The principle of the method here shortly des- characteristic not by applying a d.c. potential cribed is that the primary coil is connected in a (as in sound -film procedure) but by the use of an bridge and its (a) inductance and (b) resistance are auxiliary double refraction produced by a crystal measured with the secondary coil (i) open and (mica) screen. The operation of the apparatus is (2) short-circuited. The secondary coil is then simplified by the use of a Pulfrich (Zeiss) com- connected in the bridge and the process repeated parison photometer. The limitations of the method with the primary coil in the place of the secondary. are discussed. A frequency of 3 X io7 c/s is still The mutual induction may then be deduced. well below the region of dielectric -constant change in nitrobenzol, which for the pure liquid should be A METHOD OF MEASURING THE SELF -CAPACITANCE around Ioe c/s. But the process of cleaning is so OF COILS needed a [Only Reading being difficult that it is desirable not to rely on too great Capacitance Difference three times as great a purity, but to minimise the action of the im- as Required Capacitance].-M. G. Scroggie. by keeping the field strength down to (Wireless Engineer, September, 1933, Vol. io, purities 2 kv/cm and thus reducing the heating. No. 120, about pp. 477-479.) This is made possible by the increased sensitivity A NEW CAPACITY-METER.-W. L. Beck. (Proc. given by the biasing mica. At first it was found Phys. Soc., Ist Nov., 1933, Vol. 45, Pt. 6, that this device introduced trouble connected with No. 251, pp. 765-767.) refraction effects in the liquid flow, between the The measurement of capacity is based on the plate electrodes, arising from the slight unavoidable comparison of the impedance of the condenser warming. This trouble was eliminated by replacing under test with a calibrated standard impedance the plate electrodes by " comb " electrodes (Fig. 14) . in a differential rectifier circuit, of which a descrip- A NEW FORM OF CURRENT -MEASURING SYSTEM IN tion is given ; the balance is indicated by a d.c. simplifies the com- THE CATHODE-RAY OSCILLOGRAPH.- galvanometer. The meter and Ruska. (See under parison of capacities over a wide range of values. Matthias, von Borries " Subsidiary Apparatus and Materials.") A DIRECT -READING CAPACITY METER [suitable for A NEW HIGHLY SENSITIVE MAINS -DRIVEN VALVE Rapid Routine Testing : Fleming Commu- VOLTMETER [for Voltages of the Order of tator Principle, but using Vibrator Contact]. 0.01-1.0 Volts].-M. von Ardenne. (Funk - -D. C. Gall. (Journ. Scient. Instr., October, Magasin, August, 1933, Vol. 6, No. 8, Vol. io, Io, pp. 326--327.) 1933, No. pp. 517-520.) CALCULATION OF THE CAPACITY OF A CIRCULAR THE SHADOW CROSS " METER [Circular Scaled PLATE CONDENSER WHOSE PLATES ARE Instrument with Shadow Pointers giving INCLINED AT AN ANGLE TO ONE ANOTHER.- Simultaneous Readings of Real and Apparent H. Nitka. (Zeitschr. f. Physik, 1933, Vol. 85, Powers, Power Factor, etc.].-P. M. Pflier. No. 7/8, pp. 504-510.) (E.T.Z., 14th Sept., 1933, Vol. 54, No. 37, A NEW RADIO -FREQUENCY PHASE METER [Original PP. 887-889.) Voltages heterodyned to Convenient Audio - THE MEASUREMENT OF CRITICAL POTENTIALS WITH Frequencies for Phase Measurement : of A SCREENED GRID VALVE.-F. L. Arnot. Higher Accuracy than Cathode -Ray Oscillo- (Journ. Scient. Instr., September, 1933, graph].-R. R. Law. (Review Scient. Instr., Vol. io, No. 9, pp. 294-295.) October, 1933, Vol. 4, No. io, pp. 537-539.) THE STRING ELECTROMETER." --T. Wulf. (Book A NEW CIRCUIT ARRANGEMENT IN THE USE OF THE Review in Journ. Scient. Instr., September, WHEATSTONE BRIDGE.-E. Hasché. (Physik. 1933, Vol. io, No. 9, p. 297.) Zeitschr., 15th Sept., 1933, Vol. 34, No. 98, THE LINDEMANN pp. 718-720.) THE EFFECTIVE CAPACITY OF The present note describes an extension of an ELECTROMETER. --J. J. McHenry. (Journ. arrangement of a Wheatstone bridge, two of whose Scient. Instr., October, 1933, Vol. io, No. io, arms consist of two equal amplifier valves (for the PP. 305-310.) elimination of valve disturbances), to a form con- NOTE ON THE CONSTRUCTION AND USE OF THE taining a sensitive galvanometer in the anode THERMAL WATTMETER [for Frequencies up current circuit of the valves (i.e. connecting the to io7 c/s : Accuracy within I %].-B. A. two anodes), whose deflection is compensated by a Sharpe. (Journ. Scient. Instr., October, suitably chosen, constant bias. The arrangement 1933, Vol. io, No. io, pp. 318-321.) can be conveniently used for the analysis of dis - Practical tests on a wattmeter using the circuit January, 1934 5o THE WIRELESS ENGINEER & here employed were described by Zickner and RECENT PROGRESS IN THE FIELD OF CATHODE-RAY Pfestorf (1931 Abstracts, p. 107, 1-h col.). The EQUIPMENTS FOR MEASURING PURPOSES AND present paper includes methods of correcting the TELEVISION. -von Ardenne. (See under inaccuracies due to imperfect matching of com- " Phototelegraphy and Television.") mercial components. THE SERIOUSNESS OF HALATION IN CATHODE-RAY ABSORPTION AND REJECTOR [«aVe Trap] CIRCUITS TUBES, AND ITS ELIMINATION. -von Ardenne. AND THEIR USE IN MEASURING TECHNIQUE. (Ibid.) -Klutke. (See abstract under " Aerials and Aerial Systems.") A NEW HIGH -EFFICIENCY CATHODE-RAY TUBE : APPLICATIONS AS A PROJECTING OSCILLO - THE STANDARD -CELL COMPARATOR, A SPECIALISED GRAPH. -von Ardenne. (Ibid.) POTENTIOMETER [Measuring the Small Differ- ence between E.M.Fs of Cell under Test and THE CATHODE-RAY TUBE. -M. VOR Ardenne. Reference Cell, but with Mechanical Com- (Book Review in Electrician, 24th Nov., 1933, puting Feature which automatically Adds Vol. 1I1, No. 2895, p. 643.) this Difference to the Reference E.M.F., thus CATHODE-RAY OSCILLOGRAPH TIME -BASE EQUIP- giving Direct Reading]. -H. B. Brooks. MENT USING GLOW -DISCHARGE TUBE WITH (Bur. of Stds. bourn. of Res., August, 1933, EXTERNAL SYNCHRONISING ELECTRODE. Vol. 11, No. 2, pp. 211-231.) von Ardenne Laboratory. (Hochf:tech. -u. EARTH -RESISTANCE MEASURING APPARATUS FOR Elek:akus., April, 1933, Vol. 41, No. 4, SINGLE READING WITHOUT CALCULATION.- p. 152.) See also next abstract. Trub, Tauber & Company. (Electrician, 8th A SYNCHRONISABLE STROBOSCOPIC LIGHT SOURCE Sept., 1933, Vol. III, No. 2884, pp. 291- FOR VIBRATION INVESTIGATIONS [of Loud- 295.) speaker Systems, Sound -Film Mechanism AEF PROPOSALS ON STANDARD SIGNS AND SYMBOLS. etc.]. -von Ardenne Laboratory. (Hochf:tech. (E.T.Z., 27th July, 1933, Vol. 54, No. 3o, u. Elek:akus., April, 1933, Vol. 41, No. 4, PP. 736-739) p. 152.) Using the glow -discharge tube with external AEF PROPOSALS ON THE REPRESENTATION OF electrode employed in the oscillo- DIELECTRIC LOSSES.-(E.T.Z., 17th Aug., synchronising Vol. 54, No. 809.) graph time -base equipment referred to above. The 1933, 33, p. sprayed -on metal coating half surrounding the tube, SUBSIDIARY APPARATUS AND MATERIALS and forming the external electrode, acts simul- taneously as a light screen for the observer and as THE DESIGN AND EXAMPLES OF SYMMETRICAL a reflector for the glow -discharge light. FILTER CIRCUITS BY THE METHOD OF W. CAUER.-E. Glowatzki. (E.N.T., September MODERN APPLICATIONS OF THE CATHODE-RAY and October, 1933, Vol. to, Nos. 9 and Io, OSCILLOGRAPH [including Recording and pp. 377-386 and 404-415.) Demonstration of Valve Characteristics and The writer asserts that the instructions given in Acoustic Frequency Curves]. -J. Kammer- Cauer's book (see David, 1933 Abstracts, p. 443) loher. (E.T.Z., 19th Oct., 1933, Vol. 54, have not unfairly been criticised as too short. No. 42, pp. 1019-1021.) In view of the great practical value of the contents With specimen oscillograms taken with a von of the book the writer here reproduces some of the Ardenne tube. more important tables (some of them in an extended form) and explains the method of using them. A CATHODE-RAY OSCILLOGRAPH FOR RECORDING USING A SINUSOIDAL For a correction to Part I see bottom of p. 415. RESONANCE CURVES, TIME BASE. -Ulbricht. (See abstract under FILTERS IN ACTION [Action of a 7 -Stage Band -Pass " Measurements and Standards.") Filter demonstrated visually by a Series of Pendulums]. -C. E. Lane. (Bell Lab. THE CATHODE-RAY OSCILLOGRAPH.-A. L. M. Record, September, Vol. 12, No. i, Sowerby. (Wireless World, 3rd November, 1933, Vol. PP- 2-7.) 1933, 33, PP- 356-357.) AN IMPROVED D.C. AMPLIFYING CIRCUIT [Develop- VOLTAGE AMPLIFICATION USING SCREEN -GRID ment of Soller's Single -Valve Balanced VALVES WITH FULL UTILISATION OF THE Circuit]. -L. A. Du Bridge and Hart Brown. AMPLIFICATION FACTOR [" Constant Anode (Review Scient. Instr., October, 1933, Vol. 4, Current Method " : particularly suitable for No. Io, pp. 532-536.) Cathode -Ray Oscillography].-Sewig and Soller's circuit (1932 Abstracts, p. 654,1-h col.) Kleinschmidt. (See under " Valves and balances out e.m.f. changes : the new circuit is less Thermionics.") critical in adjustment and also neutralises changes A NEW FORM OF THE CURRENT -MEASURING SYSTEM in emission current by balancing the plate current IN THE CATHODE-RAY OSCILLOGRAPH.- against the current to the space -charge grid. A. Matthias, B. von Borries and E. Ruska. THE USE OF VALVES FOR THE AMPLIFICATION OF (Zeitschr. f. Physik, 1933, Vol. 85, No. 5/6, FEEBLE CURRENTS [Photoelectric or Ionic : PP 336-352.) the Much Greater Sensitivity of the " Bridge" The writers have brought the current deviating or Differential Circuit]. -K. Zuber. (Helvet. coil into the evacuated space in the cathode-ray Phys. Acta, Fasc. 7, Vol. 6, 1933, PP. 495-503: tube and given it the form of a long pyramid - in German.) shaped box, with spaces for the passage of the EXPERIMENTAL WIRELESS 51 January, 1934 electron beam. This gives a very sensitive measur- stabilisation of mains voltage. Theoretically the ing system of small inductance, which increases the arrangement gives an absolute voltage constancy, sensitivity of current measurement by several but in practice this is only approximately attained, orders of magnitude. The constants of such coils since the lamp characteristic is not strictly linear are calculated and reproductions of oscillograms of and also shows hysteresis loops. The effect of transients are given which agree well with the these phenomena on the stabilisation is examined results of calculation. experimentally for various conditions of load, using V mains. It is found that the the 200 and 205 d.c. ON THE USE OF CATHODE-RAY TUBES [and bridge circuit is from io to 5o times as good as the Correction of Errors due to External Mag- potentiometer circuit also investigated, even when netic and Electrostatic Fields]. -K. Nentwig. [the special] stabilisator tubes were used. Smaller (Funktech. Monatshefte, October, 1933, No. io, variations are given even than with a cascade PP 391-393.) arrangement requiring two lamps. THE SPLITTING OF FILAMENTARY ELECTRON The use of the glow -discharge bridge involves BEAMS [Fadenstrahlen] AT A CYLINDRICAL no special design of glow -discharge tubes with PROBE. - W. Rollwagen. (Zeitschr. f. small a.c. resistance, since this is compensated for. Physik, 1933, Vol. 86, No. 3/4, pp. 157-160.) Combinations of series and bridge arrangements are found to be specially advantageous. In this ON THE IMMERSION OBJECTIVE OF GEOMETRICAL case the glow -discharge lamps are only lightly ELECTRON OPTICS. -H. Johannson. (Ann. modulated, so that the best use is made of the der Physik, 1933, Series 5, Vol. 18, No. 4, approximately linear characteristic. It is also PP. 385-413.) shown, by superposition of a.c., that the bridge The immersion objective " of geometrical connection works better than the potentiometer electron optics consists of an arrangement of two connection in filtering the d.c. ripple. The value plane stops of diameter about r mm, raised to of this smoothing action is limited by the frequency - different potentials, through which the electron the glow -discharge lamp [its a.c. are dependence of beam passes. The properties of such a system resistance increasing by about 25 % for a frequency investigated in analogy to the properties of objec- rise from 5o to 500 c/s]. Finally, the use of the tives in geometrical optics, and the influence of glow -discharge bridge for a mains -driven audion various geometrical dimensions and voltage com- voltmeter is discussed, and the merit of the stabilis- binations is examined. Comparison of different ation shown by comparison with direct connection systems leads to the discovery of an optimum type to the mains. of system and to a rule for the choice of size of the system in order to obtain a desired magni- STABILISING ANODE VOLTAGES IN MAINS -DRIVEN fication in the region of optimum images. RECEIVERS [the " Smoothing Tube " and the Glow -Discharge " Stabilisator "].-K. LOW -VOLTAGE IMPULSE CIRCUITS [using Thyra- Nentwig. (Radio, B., F. für Alle, November, trons : for Cathode -Ray Oscillographs].- 1933, 1933, PP 481-485.) I,. B. Snoddy. (Physics, September, The " Glättungsrohre," with its one plane Vol. 4, No. 9, pp. 327-331.) electrode inside a second U-shaped electrode, is A CONTROL PANEL FOR AN OSCILLOGRAPH LABORA- only suitable where no voltage higher than 15o v is TORY. -R. T. Pennoyer and S. O. Evans. required. The " Stabilisator " potential divider (Gen. Elec. Review, September, 1933, Vol. (see many past Abstracts) is free from this limi- 36, No. 9, pp. 389-393.) tation. THE PRODUCTION OF STRONG, CELLULOSE ACETATE THE CALCULATION OF SERIES RESISTANCE AND a FILMS [e.g. 1 x ro cm Thick with- CURRENT SOURCE FOR [Glow -Discharge] standing I Atmosphere]. -L. Harris and STABILISER TUBES. -J. von Frommer. E. A. Johnson. (Review Scient. Instr., (E.T.Z., 31st Aug., 1933, Vol. 54, No. 35, August, 1933, Vol. 4, No. 8, pp. 454-455.) pp. 839-841.) Calculations regarding the multiple -electrode voltage dividers referred TO GLASS SEALS. de Laszlo. (Journ. COPPER -H. to in 1933 Abstracts, p. 577, r -h column Scient. Instr., September, 1933, Vol. io, (" Stabilovolt " Patent). No. 9, pp. 296-297.) THE [Glow -Discharge Tube] STABILISATOR AS PHOTOGRAPHIC PLATES FOR USE IN SPECTRO- TIME -MARK RECORDER FOR LOOP OSCILLO - SCOPY AND ASTRONOMY. K. III .-C. E. GRAPHS. Franz. (E.T.Z., 28th Sept., Mees. (Journ. Opt. Soc. Am., July, 1933, -K. 1933, Vol. 54, No. 39, p. 938.) See also Vol. 23, No. 7, pp. 229-233.) Continuation preceding abstract. of the work referred to in 1932 Abstracts, p. 418, r -h column. THE MARCONI STABILOVOLT CURRENT SUPPLY SYSTEM. -(Marconi Review, Sept./Oct., 1933, CONTRIBUTIONS TO THE STABILISATION OF VOL- No. 44, pp. 22-26 : to be continued.) TAGES BY GLOW -DISCHARGE LAMPS [and the Great Superiority of the " Glow Discharge THE GLOW DISCHARGE AT ATMOSPHERIC PRES- Bridge " Circuit over the usual " Stabilisa- SURE. -H. Thoma and L. Heer. (Zeitschr. tor " Potentiometer Circuit]. -K. Lämm- f. tech. Phys., No. io, Vol. 14, 1933, pp. of the chen : Körös. (Hochf:tech. u. Elek:akus., 385-388.) Further development October, 1933, Vol. 42, No. 4, pp. 119-126.) work referred to in Abstracts, 1933, p. 112, Author's summary :-This work investigates a l -h column. See also Heer, 1933, p. 578, l -h bridge circuit with a glow -discharge lamp, for the column. January, 1934 52 THE WIRELESS ENGINEER &
VOLTAGE -REGULATION OF A.C. GENERATORS [by the impedance of fixed condensers of various the Use of Glow -Discharge Potential Dividers different types and capacities at 6o Mc/s. and Valves]. (Helvet. -W. Druey. Phys. ON SOME MECHANICAL AND THERMAL PROPERTIES Acta, Fasc. 7, Vol. 6, 1933, PP. 488-490 in German, with circuit OF ELECTRICAL INSULATING MATERIALS diagram.) (NATURAL AND CERAMIC). -U. RetzOw. (Zeit- NEW GLOW -DISCHARGE TUBES [" Universal," for schr. f. tech. Phys., No. 10, Vol. 14, 1933, Resonance Indication, Generation of Oscilla- PP. 424-427.) tions, : etc. " Amplitude," for Limiting : EFFECT OF TEMPERATURE AND FREQUENCY ON THE " Smoothing : " etc.]. -C. W. A. Pasewaldt. DIELECTRIC CONSTANT, POWER FACTOR, (Funk -Magazin, April, 1933, Vol. 6, No. 4, AND CONDUCTIVITY OF COMPOUNDS OF PP 255-259.) PURIFIED RUBBER AND SULPHUR. -A. H. THE USE OF TRIODE VACUUM TUBE RECTIFIERS Scott, A. T. McPherson and H. L. Curtis. TO SUPPLY CONSTANT VOLTAGE. -L. A. (Bur. of Stds. Journ. of Res., August, 1933, Richards. (Review Scient. Instr., September, Vol. II, No. 2, pp. 173-209.) 1933, Vol. 4, No. 9, PP 479-482.) See 1933 PROPERTIES OF MYCALEX [with Electrical Data Abstracts, p. 636, r -h column. up to loo Mc/s].-W. W. Brown. (Proc. INITIAL IMPULSE INDICATOR [for Determining Inst. Rad. Eng., September, 1933, Vol. 21, Which of a Series of Rapidly Occurring No. 9, pp 1338-1342.) Events happened First: Arc -Back Indica- THE LOW -LOSS STEATITE MATERIALS FREQUENTIT tion in Mercury -Vapour Rectifier Sets, AND FREQUENTA [including Dielectric Loss etc.]. -O. W. Livingston and H. W. Lord. Data at Wavelengths down to 6 Metres]. -- (Electronics, September, 1933, pp. 257 and E. Albers -Schönberg. (Zeitschr. V.D.I., 260.) 3oth Sept., 1933, Vol. 77, No. 39, pp. 1077- 1078.) A PHONIC MOTOR [for Frequencies up to 7 500 c/s (4 500 r.p.m.) : Free from Hunting : Uni- THE DIELECTRIC LOSSES OF INSULATING OILS AT formity in Pole Pitch and Form obtained VERY HIGH FREQUENCIES [I07 -I08 C/S]. - by Spur -Gear Design of Rotor]. -T. Ikebe. H. Beck. (Physik. Zeitschr., Ist Oct., 1933, (Rep. of Rad. Res. in Japan, September, Vol. 34, No. 19, pp. 721-729.) Vol. 3, No. 2, 1933, pp. 177-180.) DIELECTRIC CONSTANTS OF AQUEOUS SOLUTIONS THE DIRECT SUPPLY OF MULTIPLE TELEPHONE AT VERY HIGH FREQUENCIES [ Á = 60 Cm]. SYSTEMS BY " TELEPHONIC " GENERATORS -E. Plötze. (Ann. der Physik, 1933, Series [48 -Volt Dynamos requiring No Floating 5, Vol. 18, No. 3, pp. 288-298.) Batteries or Filters]. -H. Fontaine. (Ann. LAMINATED OR NON -LAMINATED HIGH -FREQUENCY des P.T.T., October, 1933, Vol. 22, No. Io, CORES ? and IRON -POWER CORES [Ferro - pp. 874-908.) cart]. -A. Schneider : G.W.O.H. (Wireless THE APPLICATION OF X-RAYS TO THE STUDY OF Engineer, September, 1933, Vol. ro, No. 120, THE ACTIVE MATERIALS IN LEAD ACCUMU- PP 491-492 and 467-468). Continuation LATORs.-G. Génin. (Rev. Gén. de l'Elec., of the discussion dealt with in 1933 Abstracts, 26th Aug., 1933, Vol. 34, No. 8, pp. 235-243.) p. 515, 1-h column. EXPERIMENTAL DETERMINATION OF THE EDGE THE FER -X RADIO -FREQUENCY TRANSFORMER.- CORRECTION FOR PLATE CONDENSERS OF R. Wittwer. (Radio, B., F. für Alle, October, RELATIVELY SMALL DIAMETER AND LARGE 1933, PP 455-456.) See also 1933 Abstracts, THICKNESS. -F. Keller and W. R. Lehmann. p. 579, 1-h column. (Zeitschr. f. Physik, 1933, Vol. 85, No. 3/4, NIRESIST, A HIGH -QUALITY CAST IRON [alloyed pp. 253-256.) with Monel Metal and Ferrochrome]. -R. Tables and curves are given from which the Hanel and R. Müller. (Zeitschr. V.D.I., amount by which the measured capacity differs 21st Oct., 1933, Vol. 77, No. 42, p. 1142.) from that calculated from the usual formula may COMPENSATION OF THE D.C. MAGNETISATION IN be read off, for circular plate condensers of area 1.77 to Ioo sq. IRON -CORED CHOKING CoILS.-F. Vilbig. cm and distance between plates of 1933, Vol. I to 6 mm. (T.F.T., September, 22, No. 9, The edge correction, in percentage of 237-238.) the measured capacity, is found to be independent pp. of the dielectric constant. THE USE OF POLARISED -GRID VALVES [Thyratrons] AS PROTECTING RELAYS. -R. Wideröe : CALCULATION OF THE CAPACITY OF A CIRCULAR AEG. (Rev. Gén. de l'Elec., 19th Aug., 1933 PLATE CONDENSER WHOSE PLATES ARE Vol. 34, No. 7, pp. 197-202.) INCLINED AT AN ANGLE TO ONE ANOTHER. - OF H. Nitka. (Zeitschr. f. Physik, 1933, Vol. STATIC CHARACTERISTICS HOT -CATHODE THY- 85. No. 7/8, RATRONS [Important Anomalies : the Effect PP- 504-510.) of a Magnetic Field]. -Y. Watanabe and BY-PASS CONDENSERS FOR 5-METRE [Ultra -Short - T. Takano. (Journ. I.E.E. Japan, August, Wave] WORK.-( Wireless World, 29th Sep- 1933, Vol. 53 [No. 8], No. 541 : English tember, 1933, Vol. 33, pp. 266-267.) summary pp. 62-64, Japanese paper pp. 673- The performance of by-pass condensers on the 679.) ultra -short wavelengths has not hitherto received Among other results, it is found that when the much attention. Measurements are here given of magnetic field is suddenly made or broken the arc EXPERIMENTAL WIRELESS 53 January, 1934 may start even with a high negative grid bias. A COMBINED TESLA COIL AND VACUUM TUBE [Oil - " These experiments lead us to consider that an Immersed H.F. Resonance Coil with Its electron emitted from a hot cathode can obtain a High -Potential End forming Inner Elec- velocity high enough to start ionisation, on account trode of a Vacuum Tube]. -C. C. Lauritsen of an e.m.f. due to the sudden change of a magnetic and R. Crane. (Review Scient. Instr., Sep- field." tember, 1933, Vol. 4, No. 9, pp. 497-500.) A THYRATRON LABORATORY RECTIFIER [with A SIMPLE CONSTANT -TEMPERATURE CONTROL CIR- Grid Bias from Regulating Device con- cUIT.-H. Clarke. (Journ. Scient. Instr., sisting chiefly of Resistance in series with October, 1933, Vol. Io, No. io, pp. 329-330.) Neon Lamp]. -R. M. Kime. (Electronics, SPECIAL August, 1933, Vol. 6, No. 8, p. 219.) TELEPHONY SLIDE RULES [" Reactance" and " Cross -talk Transmission Equivalent "]. THE PARALLEL OPERATION OF GRID -CONTROLLED -(E.N.T., October, 1933, Vol. io, No. Io, RECTIFIERS. -E. Uhlmann. (Archiv f. pp. 422-423.) Elektrot., 1st Aug., 1933, Vol. 27, No. 8, A SIMPLE OF pp. 586-596.) METHOD ANALYSING STRIP RECORDS OF REGISTERING APPARATUS : A CRITICISM CURRENT DIRECTORS : A.C. RECTIFIERS AND AND REPLY. -H. Hä.ussler : Dalchau. A.C. FREQUENCY TRANSFORMERS.-O. Löbl. (E.T.Z., 21st Sept., 1933, Vol. 54, No. 38, (7_eitschr. I'.D.I., 24th June, 1933, Vol. 77, p. 926.) See 1933 Abstracts, p. 285, l -h No. 25, pp. 684-69o.) column. THE THEORY OF THE DIRECT CONVERSION OF POLYPHASE TO SINGLE PHASE CURRENT BY STATIONS, DESIGN AND OPERATION MERCURY -VAPOUR CONVERTERS.--R. Fein- THE [Police] RADIO PATROL SYSTEM OF THE CITY OF berg. (Archiv f. Elektrot., Ist Aug., 1933, NEW YORK. -F. W. Cunningham and T. W. Vol. 27, No. 8, pp. 539-557.) Rochester. (Proc. Inst. Rad. Eng., Sep- tember, 1933, Vol. 21, No. 9, 1239-1251.) A NEW BARRIER -LAYER RECTIFIER [CUS/Cu2S pp. between Copper Electrodes]. -M. Anas- EXPERIMENTS IN ULTRA -HIGH -FREQUENCY COM- tasiadés. (Comptes Rendus, 2nd Oct., MUNICATION [on 3 -Io Metre Waves,including 1933, Vol. 197, No. 14, pp. 647-678.) Transmissions from Summit of Mt. Fuji]. - NEW T. Nakai, R. Kimura and S. Ueno. (Rep. STATICAL ELECTRICAL MACHINES : OF CON- of Rad. Res. in Japan, June, 1933, Vol. STANT POLARITY, AND PRACTICALLY INDE- 3, No. I, pp. in Abbrevi- PENDENT 7-17: English.) OF ATMOSPHERIC CONDITIONS : ated translation of the paper dealt with OUTPUT 3 WATTS. -P. Jolivet. (Comptes in 1933 Abstracts, p. 173, r -h column. Rendus, 9th Oct., 1933, Vol. 197, No. 15, PP 744-746.) A STUDY OF RECEPTION FROM SYNCHRONISED BROADCAST STATIONS [Common -Wave EDGES IN HIGH -VOLTAGE TECHNIQUE. -H. Kropp. Broadcasting]. -Aiken. (See under " Re- (Archiv f. Elektrot., 4th Oct., 1933, Vol. 27, ception," p. 37.) No. 10, pp. 681-69o.) EXPERIMENTS WITH A RADIO BROADCASTING LACQUER -COATED RESISTORS OF HIGH RESIST- SYSTEM UTILISING THE NETWORK OF DIS- ANCE. -Bureau of Standards. (Journ. Frank- TRIBUTION LINES OF AN ELECTRIC SUPPLY. - lin Inst., October, 1933, Vol. 216, No. 4, I. Miura. (Rep. of Rad. Res. in Japan, Sep- P 542) tember, 1933, Vol. 3, No. z, pp. 137-154.) A preliminary note on a method of preparation The full paper, in English, with in 1933 of reliable dealt resistors of high resistance of the order Abstracts, p. 639, l -h column. of Ios to to12 ohms. A pyrex rod is coated with graphite and the rod, thus prepared, is coated with KETTERING'S RADIO RELAY SYSTEM [" Wired glyptal lacquer. Wireless "].-T. H. Hall. (Elec. Review, 15th Sept., 1933, Vol. 113, No. 2912, p. A CONTINUOUSLY VARIABLE RHEOSTAT DISPENSING 345) WITH SLIDING CONTACTS [Wire -on-Drums Principle in Practical Form, with Single - RADIO RELAY SYSTEMS.-(Ibid., 29th Sept., 1933, Knob Control]. -L. H. Bainbridge -Bell. Vol. 113, No. 2914, PP- 414-415.) (Journ. Scient. Instr., September, 1933, Vol. DISCUSSION ON " SUPERVISORY AND CONTROL io, No. 9, pp. 295-296.) EQUIPMENT FOR AUDIO -FREQUENCY AMPLI- SKIN EFFECT IN RECTANGULAR CONDUCTORS. - FIERS " [and the Bell System Volume In- Forbes and Gorman. (Elec. Engineering, dicators with " Duration Characteristic " September, 1933, Vol. 52, No. 9, pp. 636-639.) of the Ear]. -A. F. Rose : Sohon. (Proc. Inst. Rad. Eng., October, 1933, Vol. 21, ADJUSTING THE INDUCTANCE OF SCREENED COILS No. Io, p. 1497.) For Sohon's paper see BY PERMANENT DEFORMATION OF SCREEN. - 1933 Abstracts, p. 286. Philips Company. (German Pat. 573 635, pub. 4. 4.1933-) GENERAL PHYSICAL ARTICLES THE THYRATRON TUBE AS A STROBOSCOPE. -B. L. DIELECTRIC CONSTANT AND IONISATION VOLTAGE OF Robertson and T. A. Rogers. (Gen. Elec. GASES [and a Formula Connecting Them]. - Review, October, 1933, Vol. 36, No. Io, A. Güntherschulze. (Zeitschr. f. Physik, 1933 PP- 455-457.) Vol. 86, No. 3/4, PP 249-252.) January, 1934 54 THE WIRELESS ENGINEER &
INVESTIGATIONS OF THE INFLUENCE OF A MAGNETIC ABSORBOMICROMETRIC MEASUREMENTS [with the FIELD ON THE DIELECTRIC CONSTANT OF Absorption Ultra -Micrometer] AND THEIR ARGON AND OXYGEN, BY A NEW RESONANCE PRACTICAL APPLICATIONS IN CIVIL ENGI- METHOD. -H. Voss. (Zeitschr. f. Physik, NEERING " [Book Notice]. -P. Santo Rini. 1933, Vol. 85, No. 3/4, PP. 172-179) (E.T.Z., 16th. Nov., 1933, Vol. 54, No. 46, A resonance method (Gerlach) is used to show p. 1131.) See 1932 Abstracts, p. 361, r -h that " a magnetic field of r o8o gauss has, for column. a wavelength of 3o m, no influence on the di- A TELEGRAPH DISTORTION MEASURING SET [With electric constant a of argon and of oxygen which Low -Voltage Cathode -Ray Tube]. -V. J. is larger than A = 4.6 X I0-7 for argon and Terry and C. H. W. Brookes -Smith. (Elec. Ae = 3.1 X to-, for oxygen." Communication, July, 1933, Vol. 12, No. I, THE ELECTRICAL DIFFUSION OF IONS IN GASES pp. 15-23.) CONTAINING CHARGED IONS OF BOTH SIGNS. RADIO MANUFACTURERS ASSOCIATION ACCEPTS -N. Wolodkewitsch. (Zeitschr. f. Physik, NATIONAL ELECTRICAL MANUFACTURERS 1933, Vol. 84, No. 9/1o, pp. 593-609.) ASSOCIATION CODE. -(Electronics, September, Theory and experiment show that the variation 1933, PP 238-239.) with time of the a gas charge density in containing THE VII INTERNATIONAL HIGH VOLTAGE CON- ions of both signs is given by the same as formula FERENCE IN PARIS, 1933. PART III [in- that in a gas with ions of one sign only. cluding Lightning Protection and Broadcast THE MOBILITY OF POSITIVE IONS IN GASES [Theoreti- Interference]. -H. Feiner. (E.T.Z., 2nd cal Investigation]. -T. Edqvist. (Physik. Nov., 1933, Vol. 54, No 44, PP. 1062-1065). Zeitschr., 15th Aug., 1933, Vol. 34, No. 16, 1933 -ELECTRICAL 618-623.) BERLIN RADIO EXHIBITION, pp. MUSIC : HOME RECORDING : TELEVISION :
ELECTRICAL AND OPTICAL MEASUREMENTS OF HIGH NOVELTIES OF RECEIVER DESIGN : COM- FREQUENCY GAS DISCHARGES. -L. Rohde PONENTS. -(Radio, B., F. für Alle, Sep- and H. Schwarz. (Zeitschr. f. Physik, 1933, tember, 1933, pp. 4I9-438.) Vol. 85, No. 3/4, pp. 161-171.) THE OFFICIAL [Post Office, Air Ministry, Navy, The writers find that, at very high frequencies, etc.] SPECIAL EXHIBITS AT THE IOTH GERMAN the resistance of the gaseous column may be regarded RADIO EXHIBITION. G. Kette. (E.T.Z., as constant over a period. give an equivalent They 9th Nov., 1933, Vol. 54, No. 45, pp. circuit whose properties reproduce those of the 1085-1088.) discharge. THE LOTH PARIS RADIO EXHIBITION. -M. Adam. ON THE THEORY OF THE DIFFUSION OF HIGH - (Génie Civil, 23rd Sept., 1933, Vol. 103, VOLTAGE ELECTRONS. -J. Winter. (Comptes No. 13, 304-308.) Rendus, 16th October, 1933, Vol. 197, No. 16, pp. pp. 828-829.) THE EMISSION OF A VERY SOFT RADIATION FROM ELECTRIFIED DIELECTRICS, and STUDY OF MISCELLANEOUS THE RADIATION OF SEMI -CONDUCTING CELLS [Short] YEARLY REPORT OF THE ELECTRICAL BY MEANS OF A SPECTROGRAPH in Vacuo. - ENGINEERING AND RADIO DIVISION OF THE G. Reboul : G. Déchêne. (Comptes Rendus, GERMAN AIRCRAFT RESEARCH ESTABLISH- 26th June, 1933, Vol. 196, No. 26, pp. 1987- MENT [DVL].--H. Fassbender. (E.T.Z., 1989 : 1989-1991.) 14th Sept., 1933, Vol. 54, No. 37, pp. 885-887.) 51 -RAYS [Mitogenetic Rays] AFFECT FULL-GROWN Researches on selective fading : " alternate AS WELL AS YOUNG CELLS.-Kowarzyk. aerial " transmission (1933 Abstracts, pp. 557-558) (Sci. News Letter, loth June, 1933, Vol. 23, effective height of trailing as aerial affected by No. 635, p. 361.) For previous work on speed (even at 35o km/h the standard trailing aerial these rays see Magrou, Abstracts, 1932, has an effective height twice as great as that of a p. 301, and 1930, p. 177, r -h columns. soundly designed fixed aerial) : beryllium as a ELECTRICAL DEVICE FOR MEASURING MITOGENETIC substitute for phosphor -bronze : noise exclusion RAYS [Modified Geiger Counter].-Rajewsky. by flying helmet with telephones : direction -finding work (including investigation of twilight errors, (Science, 14th July, 1933, Vol. 78, No. 2011, u.s.w. rotating -frame tests, tests of Telefunken Supp. p. 6.) target -flight indicator) : fog landing (including PHOTOCELLS IN THEIR TECHNICAL FIELDS OF improved aerial designs for reception of landing - APPLICATION [including Modified Geiger beam signals) : tests of GEC and Siemens & Counter] and INDUSTRIAL PLANTS USING Halske acoustic height -meters : cathode-ray PHOTOCELLS.-Weisglass : Keller. (See oscillograph : glow -discharge -tube indicator for under " Phototelegraphy and Television.")
high-speed engines : instrument for indicating the INVESTIGATION ON MITOGENETIC RADIATION BY beginning : of ice formation etc., etc. MEANS OF A PHOTOELECTRIC COUNTER POST OFFICE RESEARCH.-(Electrician, 27th Oct. TUBE. -E. Lorenz. (Phys. Review, i5th and 3rd Nov., 1933, Aug., 1933, Series 2, Vol. Vol. III, pp. 497-498 44, No 4, PP - and 554.) 329 -330: abstract only.) THE RESEARCH WORK OF THE MARCONI COMPANY THE EMISSION OF RADIATION BY CHEMICAL RE- [Critical Review of Eccles's " Wireless "].- ACTIONS. -R. Audubert and Van Doormaal. (Marconi Review, Sept.lOct., 1933, No. 44, (Comptes Rendus, 59th June, 1933, Vol. 196, PP I-4.) No. 25, pp. 1883-1885.) EXPERIMENTAL WIRELESS ;; January, 1934
Some Recent Patents The following abstracts are prepared, with the permission of the Controller of H.M. Stationery Office, from Specifications obtainable at the Patent Office, 25, Southampton Buildings, London, W.C.2, price il- each.
BINAURAL SYSTEMS drum D. On the outside of the drum is arranged light-sensitive cells C, C,, December, 1931. No. a pair of semi -circular Application date, 14th 394325 shown separately in Fig. (1a), which perform the The action of the ears in determining the direc- necessary transformation of the varying light- tion of a source of sounds depends in part upon values into equivalent electric currents. The phase -difference and in part upon relative intensity. photo -electric cells C, C, are replaced by glow - For the lower frequencies, phase is the predominant lamps when used for reception. The advantage factor, and, in general, for a given obliquity of sound the phase -difference is approximately pro- portional to frequency. For higher frequencies the head begins to function as a " baffle " and causes appreciable intensity -differences which are interpreted in terms of direction. To reproduce binaural effects in sound -trans- mission, at least two directionally sensitive micro- phones are suitably spaced to represent the ears, and are then connected to a number of loud speakers through circuits comprising amplifiers, whereby the relative volume of the loud -speaker output is automatically controlled by the direction of the source of sound relative to the microphones. At low frequencies, differences of phase in the micro- phones are also reproduced as differences in volume at the loud -speaker. The invention is applicable to radio transmission and reception, and to the recording and reproduction of sounds for talking motion pictures. Patent issued to A. D. Blumlein and Electric and Musical Industries, Ltd.
SIGNALLING SYSTEMS (1 a) Convention date (1 S.A.), 19th December, 1931. No. 394446 No. 395242 To reduce mutual interference and faulty re- lies in rotating the comparatively light and com- ception due to reflection from the Heaviside layer, pact mirror M instead of the larger and heavier short-range broadcasting and television pro- perforated scanning drum D. grammes are distributed through beams of light Patent issued to I. M. K. Syndicate, Ltd. modulated by the radio -frequency signals. The transmitters consist of elevated beacons, fitted with high -intensity arc -lamps. The electrodes of Convention date (Germany), 12th December, 1931. the latter are screened, since only the light coming No. 394883 from the incandescent gas between the electrodes After the transmission of each scanning line, a will respond to the HF oscillations impressed upon short interval occurs during which a synchronising the lamp current. At the receiving end a lens impulse is sent. To prevent the operation of the mounted in a rotatable tube is directed on to the " spill -over " circuit used for line control, say by particular beacon transmitter selected. The re- a picture signal instead of by the special syn- ceived rays are directed by the lens on to a valve chronising impulse, the release valve (such as a amplifier with a photo -electric input. thyratron or glow -discharge tube) is normally Patent issued to British Thomson Houston Co., subjected to a paralysing bias, which is removed Ltd. at the end of each line by the action of a straight - wire electrode inside the cathode-ray tube. This TELEVISION SYSTEMS electrode, which is of the same height as the picture, receives a progressive charge from the cathode Convention date (Germany), 14th April, 1931. ray as it traverses the viewing screen. At the No. 394446 end of each traverse, the accumulated charge is An image I is focused by a lens L on to a mirror just sufficient to offset the initial bias and release M which is rotated by a motor P so as to throw the the " spill -over " device. reflected light in succession over a series of spiral Patent issued to Telefunken Ges. fur Drahtlose holes arranged around the periphery of a stationary Telegraphie m.b.h. January, 1934 56 THE WIRELESS ENGINEER &
REACTION CONTROL Convention date (U.S.A.), 16th February, 1932. Convention date (Germany) ist December, 1931. No. 393550 No. 392466 An auxiliary pentode valve is fed with an input The back -coupling coil L of the detector valve voltage derived from the rectified carrier -wave, Vi is connected in series with a resistance R and and delivers an amplified LC voltage to control the cathode of the preceding HF amplifier V. the gain of the HF stages. The advantage of Control of reaction is effected by a tapping P using a pentode valve as control lies in the high D.C. translation gain given by a relatively -small increase in the total HT supply to the set. The arrangement is particularly suitable for portable, midget, and other compact types of receiver. Patent issued to Marconi's Wireless Telegraph Co., Ltd.
DETERMINING DISTANCES Convention date (U.S.A.), 26th December, 193o. No. 393344 A navigator is enabled to determine his distance from a fixed transmitter, radiating waves of the same frequency but varying characteristics, by ascertaining the difference between these character- istics as a measure of the distance sought. For instance one set of waves is radiated from an open aerial and the other from a closed loop ; or two No. 392466. radiation fields of different attenuation, or pre- determined range, are transmitted. At the receiving connected to the cathode of the detector. Simul- end, the signals may be arranged to give a visual taneously a compensating bias is applied to the indication, with or without the use of a locally - grid of the HF amplifier which tends to offset generated oscillation ; or " null " or balanced any variation in amplification caused by the change methods of reception may be used to give the in reaction. desired information. Patent issued to Telefunken Ges für drahtlose Patent issued to E. G. Gage. Telegraphic m.b.h. DOUBLE-RESONANCE CIRCUITS. AUTOMATIC VOLUME CONTROL Application date, 17Uí November, 1931. No. 393983. Convention date (U.S.A.), 23rd October, 1931. A complex coupling -circuit of the band-pass No. 391373 type, tunable over a range of frequencies, and having each tuning point two To increase the sharpness of at resonant values separated control, on any by a constant amount, is fluctuation of the carrier wave, an auxiliary valve characterised by the is shunted feature that mutual inductance is eliminated, the across the input to the ordinary detector double -hump response valve, and acts (a) to rectify being due entirely to the part of the incoming self-inductance and of signal voltage, and (b) capacity the component to amplify the direct -current elements. The circuit component in the output from the detector valve, shown in the Figure, for thus increasing the instance, has one resonant frequency due to the biasing voltage used to control elements K1, the " gain " of the preceding H.F. stages. Ll, L,, L3, KZ, L4 in series, and Patent issued to Marconi's Wireless Telegraph L1 L2 L3 Co., Ltd.
Convention date (Germany), 6th June, 1931. No. 393415 In a receiver for modulated carrier -wave energy, a rectifier valve having a characteristic curve of substantially logarithmic form (over a range of input amplitudes of about 1 : io) is utilised to give L4 an output which is independent of the amplitude No. 393983 of the carrier -wave within these limits, but which varies directly as the percentage modulation of another due to the figure -of -eight path K1, L,, the carrier. A mathematical analysis is given, K3, K2, L3, K4, back to K1. The condensers K,, and the arrangement as a whole is distinguished K, are ganged. The arrangement may be used from the known super -regenerative circuit,-in as an input or intervalve coupling, or for linking which the rectifier characteristic also approximates the local oscillator with the HF input in a superhet to a logarithmic curve. receiver. The position of certain of the reactances Patent issued to Telefunken Ges für drahtlose may be interchanged. Telegraphie m.b.h. Patent issued to N. P. Hinton. EXPERIMENTAL WIRELESS 57 January, 1934
SHORT-WAVE RECEIVERS are two auxiliary electrodes in the form of frusto - conical rings, or metallic deposits laid on the Convention date (Germany), 18th June, 1931. internal surface of the glass, each being electrically No. 393755 separate and charged with increasing voltages The Figure shows a circuit designed primarily designed to accelerate the electron stream. For for the reception of short-wave television signals instance, the lower ring near the cylindrical anode covering a bandwidth of from three to fifteen carries a voltage of zoo and the upper ring, nearer million cycles, the incoming signals being hetero- the fluorescent screen, a voltage of 500. The dyned by a local oscillator O. The relatively large anode proper is at 300 volts relative to the cathode. -I
LOAD
1 No. 393755. The usual deflecting or scanning plates are arranged in or about the centre of the zoo -volt ring. Patent issued to International General Electric Co., Inc.
Convention date (Germany), 3oth November, 1931. No. 394580 In order to avoid disturbing luminous pheno- mena in a cathode-ray tube for receiving television, loading capacity of the anode circuit of the screen - detector, the usual incandescent cathode is replaced by a grid valve 1 allows it to act as a first hollow cylinder having a highly-emissive coating .passing the intermediate frequency to subsequent on its external surface. This is heated to a tem- screen -grid stages 2 and 3. The output from the perature not exceeding a dull red by electronic latter is fed to a second detector 4 and then through bombardment from an internal oxide -covered an aperiodic amplifier comprising resistance - filament. The cathode -cylinder is, of course, kept capacity coupled stages 5 --- 7. Typical values for at a positive potential relatively to the filament, the circuit elements are given in the specification. and the same voltage -source may be used to bias Patent issued to M. von Ardenne. the usual Wehnelt electrode. Patent issued to Telefunken Ges. fur Drahtlose CATHODE-RAY TUBES Telegraphie m.b.h. Convention date (Germany), 13th December, 1930. No. 393651 When the cathode is directly heated, observation POWDER-CORE INDUCTANCES shows that the spot of light formed by the impact of the ray against the fluorescent screen is of uneven Application date, 15th December, 1931. No. 394327 intensity. This is due to the influence of the mag- Use is made of a known type of spraying -gun netic field from the heating current which causes to cover a coil of wire with magnetic powder, the the individual electrons to oscillate within the particles of which have previously been coated path of the stream. According to the invention with an insulating film of oxide produced by the cathode is constructed so as to have an emissive spraying through a suitable medium such as surface of restricted area which is shielded from the oxygen, steam, or water. Alternatively, the mag- magnetic field in question. The modulating or netic powder and an insulating solution of synthetic accelerating electrode is also screened so as to resin may be simultaneously sprayed on to the coil. apply only a " point " electric field to the stream. The wire may originally be treated in the form of Patent issued to U. W. Doering. a flat helix, and a number of these subsequently assembled to form an inductance of the desired Convention date (Germany), 9th October, 1931. value. No. 393826 Patent issued to B. S. Cohen ; F. O. Barralet ; Between the anode and the fluorescent screen and E. D. Hebden. January, 1934 58 THE WIRELESS ENGINEER &
TELEVISION RECEIVERS HETERODYNE S.W. RECEIVERS Convention date (France), 20th December, 1930. Convention date (U.S.A.), 16th January, 1932. No. 394341 No. 394267 A cathode - ray The Figure shows a circuit designed to receive tube comprises a wavelengths of the order of one centimetre to half cathode K, an a metre. The signal energy is received on a dipole anode a to which aerial A, with a parallel tuned Lecher -wire shunt S (1 a) the incoming sig- to ground, and is applied through blocking con- nals are applied densers C to the plate and grid of a Barkhausen- through a coupling Kurz oscillator O. For a half -metre wave the oscil- M, and scanning lator is tuned by the condenser C1 to 603 mega- electrodes C1, C2. cycles, and the resulting beat frequency of 3 mega- The ordinary cycles is passed through a condenser to a combined fluorescent screen super -regenerative, second -detector, and amplifier is, however, re- combination. This comprises two push-pull valves placed by a par- V1, 172 back -coupled to a split input -circuit through tition P of thin a coil L. The valve V1 acts as a regenerator and sheet glass, covered the valve V2 as a combined " degenerator " and or impregnated low -frequency quenching -oscillator. The plate cir- with a coating of cuit L2, C2, is tuned to the quenching frequency, metallic oxide (or C1 a thin slice of 02 agate). This in effect divides the cathode tube pro- per from a second gas -filled chamber or glow -tube N con- taining a second anode A, shown in cross-section in Fig. (1a), which No. 394341 forms a viewing screen. As the cathode ray sweeps over the surface of the par- tition A, it causes each elementary portion of the latter to act momentarily as an individual cathode and so to project a point of light through the glow - lamp chamber N on to the viewing-screen. Patent issued to Compagnie pour la Fabrication des Compteurs et Materiel d'Usines à Gaz.
Application date, Ist January, 1932. No. 394710 An auxiliary scanning -device, driven synchron- ously with the main scanner, is provided to build up a second image. The latter enables a skilled operator to " monitor " the main image, i.e., to perform the synchronising and framing adjustments necessary to enable an unskilled observer, or audience, to view the principal picture under the best conditions. Patent issued to Marconi's Wireless Telegraph Co., Ltd. ; H. M. Dowsett ; and D. L. Plaistowe.
TELEVISION APPARATUS Application date 16th December, 1931. No. 393978 In a mirror -wheel used for television scanning each individual mirror is mounted upon a ball - seated carrier, designed to fit into a cupped recess in the wheel or disc and to be locked in position No. 394267. at any desired angle to the surface or periphery. The arrangement lends itself to mass manufacture, and is back -coupled at this frequency to the coil and allows of easy adjustment without throwing L3. Both L2, C, and L3, C3 act as short circuits any strain on the mirror elements. for the high signal frequency. Patent issued to Marconi's Wireless Telegraph Patent issued to Marconi's Wireless Telegraph Co., Ltd., and R. J. Kemp. Co., Ltd.