Chapter 8 , Protocols and Modes Greg Wolfe KIØKK Thanks to:

 Information from: • The ARRL Library • ARRL Extra Class License Manual • Gordon West Extra Class License Class

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 2 1/11/2020 Section 8-1 Modulation Systems

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 3 1/11/2020 Modulation Review

 A wave can be thought of as having two parts: • The Carrier • The Modulation (the content)  Each type of Modulation has it’s advantages and disadvantages and a typical bandwidth • CW ( or ) ▄ 100Hz • SSB (Single SideBand)* ▄▄▄ 2.8 kHz • AM (Amplitude Modulation)* ▄▄▄▄▄▄ 6 kHz • FM ()* ▄▄▄▄▄▄▄▄▄▄ 1o kHz • TV ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ 6 MHz * Voice modulation is also called Phone modulation Chapter 8 - Digital Modes (G Wolfe - KI0KK) 4 1/11/2020

Emission Designators Pg. 8-2

8-1

Common Designators • Voice SSB : J3E (J3E2K80)

• HF SSB Data: J2D

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 5 1/11/2020 Common Emission Designators Page 8-2

From the International Union - ITU

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 6 1/11/2020 Emission Types Page 8-3

 The regulations part 97 refers to emission types rather than emission designators  Emission types are: • CW • Phone • RTTY • Data • Image • MCW (Modulated CW) • SS (Spread Spectrum) • Pulse • Test Chapter 8 - Digital Modes (G Wolfe - KI0KK) 7 1/11/2020 Frequency Modulation

 FM is the most common VHF mode • Voice • Data

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 8 1/11/2020 Frequency Modulation Viewed on a Spectrum Analyzer Page 8-3

 A unmodulated An carrier is stable in unmodulated frequency carrier

A FM  With Frequency modulated Modulation, the carrier carrier shifts back and forth at the rate of How far the frequency the modulating deviates from the frequency carrier frequency is called the Deviation Chapter 8 - Digital Modes (G Wolfe - KI0KK) 9 1/11/2020 Deviation Ratio Pg. 8-3

 The Deviation Ratio is the ratio of the maximum deviation to the highest modulating frequency [E8B09].

Equation 8.1

In narrow-band FM, the peak deviation is supposed to be 5 kHz or less. Chapter 8 - Digital Modes (G Wolfe - KI0KK) 10 1/11/2020 To Calculate the Deviation Ratio Pg. 8-3 & 4

 To calculate deviation ratio of an FM signal, simply divide the maximum carrier frequency swing by the maximum modulation frequency. • The larger number is divided by the smaller number.

 If the peak deviation of a FM signal is 5 kHz and the maximum modulating frequency is 3 kHz, what is the deviation ratios? • Deviation Ratio = 5 kHz / 3 kHz = 1.67 (Example 8-1) [E8B05]

 Or if the peak deviation is 7.5 kHz and the maximum modulating frequency is 3.5 kHz, then: • Deviation ratio = 7.5 kHz / 3 kHz = 2.14 (Example 8-2) [E8B06]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 11 1/11/2020 Let’s take a look at the FM Spectrum

Deviation Radio of 1.67 Deviation Ratio of 3

Frequency spectrum of FM signals.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 12 1/11/2020 Modulation Index Pg. 8-4

 The Modulation Index is the ratio of the maximum deviation to the modulating frequency at any given instant [E8B01].

Equation 8.2

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 13 1/11/2020 To Calculate the Modulation Index Pg. 8-4

 To calculate the modulation index of an FM signal, simply divide the maximum carrier frequency swing by the instantaneous modulation frequency. • The larger number is divided by the smaller number.

 If the peak deviation of a FM signal is 3 kHz and the modulating frequency is 1 kHz, what is the modulation index? • Modulation index = 3 kHz / 1 kHz = 3 (Example 8-3)[E8B03]

 Or if the peak deviation is 6 kHz and the maximum modulating frequency is 2 kHz, then: • Deviation ratio = 6 kHz / 2 kHz = 3 (Example 8-4)[E8B04]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 14 1/11/2020 Modulation Index

 As the modulation index increases, so does the width of the signal as viewed on a spectrum analyzer

http://www.radio-electronics.com/info/rf-technology-design/fm-frequency-modulation/spectrum- bandwidth-sidebands.php Chapter 8 - Digital Modes (G Wolfe - KI0KK) 15 1/11/2020 Looking at Voice FM Modulation

on a Spectrum Analyzer

Amplitude

Frequency

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 16 1/11/2020 What About the Operating Freq? Pg. 8-5

 Notice that with either FM or PM, the deviation ratio and modulation index are independent of the RF carrier frequency (operating frequency).  It doesn’t matter if the transmitter is a 10m rig, a 2m rig or a 23 cm rig.

• Deviation Ratio = DMAX / M

• Modulation Index = DMAX / m  The maximum modulation index allowed by the FCC rules is 1 on frequencies below 29.5 MHz [E1B07].

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 17 1/11/2020 Multiplexing Pg 8-5

 Multiplexing means combining more than one stream of information into one modulated signal (baseband).  The two common methods are: • Frequency division multiplexing (FDM) • Time division multiplexing (TDM)

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 18 1/11/2020 Frequency Division Multiplexing Pg. 8-5

 With FDM, two or more information streams are merged together in a “baseband” signal that is used to modulate the carrier [E8B10].

Information Stream #1 Baseband Carrier Information Stream #2

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 19 1/11/2020 Time Division Multiplexing Pg. 8-6

 With TDM, two or more information streams are carried over a single channels by so that they occur in separate discreet time slots [E8B11].

 In amateur radio, TDM is used mostly in telemetry, such as from satellites and digital voice modes such as D-Star DV.

Information Stream #1 Information Packet

Sync Sync

Time Information Stream #2

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 20 1/11/2020 How does the modulation index of a phase- modulated emission vary with RF carrier frequency (the operating frequency)? [E8B02]

A. It increases as the RF carrier frequency increases B. It decreases as the RF carrier frequency increases . It varies with the square root of the RF carrier frequency D. It does not depend on the RF carrier frequency

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 21 1/11/2020 What is the modulation index of an FM-phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency, when the modulating frequency is 1000 Hz? [E8B03]

A. 3 B. 0.3 C. 3000 D. 1000

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 22 1/11/2020 What is the highest modulation index permitted at the highest modulation frequency or angle modulation below 29.0 MHz? [E1B07]

A. 0.5 B. 1.0 C. 2.0 D. 3.0

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 23 1/11/2020 What is meant by deviation ratio? [E8B09]

A. The ratio of the audio modulating frequency to the center carrier frequency B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency C. The ratio of the carrier center frequency to the audio modulating frequency D. The ratio of the highest audio modulating frequency to the average audio modulating frequency

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 24 1/11/2020 Which of the following describes frequency division multiplexing? [E8B11]

A. The transmitted signal jumps from band to band at a predetermined rate B. Two or more information streams are merged into a "baseband", which then modulates the transmitter C. The transmitted signal is divided into packets of information D. Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 25 1/11/2020 Section 8-2 Digital Protocols and Modes

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 26 1/11/2020 Digital Modes

 A digital mode consists of both a protocol and a method of modulation.  Digital protocols can be used to convey speech , video or data.  The advantage of using digital modes to transfer information is that the signal and its information can be copied and retransmitted multiple times without necessarily introducing errors.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 27 1/11/2020 Digital Modes for HF General Review

 Frequency Shift Keying • RTTY  Phase Shift Keying • PSK31  Packet Modes • PACTOR •

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 28 1/11/2020 A Basic Digital Communication Setup

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 29 1/11/2020 Digital Communications Signal Formats

The message is in different form throughout the communication system

 The /TNC (Terminal Node Controller) may have significant “smarts”  Uses USB or UART interface to computer

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 30 1/11/2020 Digital Communications Using a

 The PC and the soundcard have the “smarts”  The Audio Interface has no “smarts” and provides isolation between the computer and the radio  The Audio interface can be eliminated by using an external sound card Audio Audio Tones Audio Tones USB/ Tones Data

External Computer w/ Audio Radio Radio Computer Sound Card Interface Sound Card Chapter 8 - Digital Modes (G Wolfe - KI0KK) 31 1/11/2020 Digital Communications Using SDR

 Modern SDR radios use internal sound cards (ICOM IC-7610, Flex 6400)  Audio and Cat (Rig) control are passed inside the PC to the digital APP by specialized software applications  logging can be automated almost entirely  Remote operation is possible

USB/ USB/ Data Data

Computer Radio W/Sound Card Radio Computer

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 32 1/11/2020 Data Speed and Symbols Pg 8-6

 “Speed” is the rate of information transfer or data throughput • Air Link – the actual transmitted signal • The faster the rate, the wider the bandwidth required • Data Stream – the digital data to & from the computer  The individual symbols that make a specific code are the elements Element

• Letter “A”: dit dah; 00011; 01000001; 1111101 • Morse Code Baudot ASCII PSK-31 Varicode

Each 1 and 0 is a Symbol Chapter 8 - Digital Modes (G Wolfe - KI0KK) 33 1/11/2020 A Look at Rate Pg 8-6

 The baud rate refers to the number of data symbols transmitted per second.  On an oscilloscope, the data stream looks like a series of varying patterns of pulses in time.

Fig 8-1

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 34 1/11/2020 Data Rate vs Pg 8-6

 The symbol rate refers to the rate at which the transmitted signal changes in order to convey information [E8C02].  When discussing the speed of an air link, the unit of speed is the baud  Baud counts signaling events that refer to changes in the transmitted signal which represent one symbol.  Thus, the Baud Rate and symbol rate are the same [E8C11].  However in some advanced systems – each data symbol can encode more than one bit at a time. • Example: D-STAR

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 35 1/11/2020 Digital Protocol Pg 8-7

 A protocol is the overall digital specification or set of rules. It includes: • Encoding, Packaging, Exchanging and Decoding  It does not include the RF communication link Example: AX.25 for Packet

Excludes the RF

Computer Modem/TNC Radio Radio Modem/TNC Computer

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 36 1/11/2020 Protocols Controlling the Radios Pg 8-7

 Practical digital protocols require that the receiving and transmitting stations operate under the control of a microprocessor. • Specific segments of the band are set aside for fully automatic control  ALE (Automatic Link Establishment) is fully automatic, under microprocessor control [E2E12]. The microprocessor can change radio frequencies and even bands.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 37 1/11/2020 Common Codes Pg 8-8

 A code is a method by which information is converted to and from digital data

 We will look at: • Morse & Varicode (PSK-31) • Baudot (RTTY) • ASCII (PKT) • Gray Code

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 38 1/11/2020 Morse & Varicode Pg 8-8

 Most digital codes use a fixed number of bits for each character.  A variable-length code (varicode) use a different number of bits in each symbol or character. • The length of a character varies with the frequency of it’s use to save transmission time thus maximizing bandwidth or spectral efficiency.  PSK-31 and Morse use the shortest symbol for the most used character “E” [E2E09].

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 39 1/11/2020 Baudot Pg 8-8

 The is used in RTTY systems and has two elements --- Mark and Space --- each the same length.  The code uses five different mark and space combinations.  A continuous mark tone is an idle state.  Start and stop bits are sent at the beginning and end of each character and are called framing bits.  The framing bits synchronize the transmits and receive systems  A complete character, including the framing bits, is called a frame

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 40 1/11/2020 Sample of the Baudot Code

Binary Decimal Letter U.S. Baudot Figures 00000 0 N/A N/A consists of 5 binary digits 00001 1 E 3 Code 00010 2 LF LF 25 = 32 00011 3 A - So we only have 00100 4 Space Space Elements 32 combinations, 00101 5 S BELL

however we can 00110 6 I 8 double that to 64 by pulling a “trick” 00111 7 U 7 of sending LTRS 01000 8 CR CR or FIGS 01001 9 D $ 01010 10 R 4 Chapter 8 - Digital Modes (G Wolfe - KI0KK) 41 1/11/2020 ASCII Code Pg 8-9

At least 7 bits are for characters 7 0r 8 Bits 27 = 128

Symb DEC OCT HEX BIN Description 128 possibilities ol allows for upper and 32 040 20 00100000 Space lower case letters 33 041 21 00100001 ! Exclamation mark [E8D11] Double quotes (or speech 34 042 22 00100010 " marks) The 8th bit can be 35 043 23 00100011 # Number parity bit, used to 36 044 24 00100100 $ Dollar detect transmission 65 101 41 01000001 A Uppercase A errors or it can be 66 102 42 01000010 B Uppercase B used to extend the 67 103 43 01000011 C Uppercase C character set to 256 [E8D12] http://ascii-code.com/ Chapter 8 - Digital Modes (G Wolfe - KI0KK) 42 1/11/2020 PSK31 Varicode Pg 8-8

PSK-31 uses Varicode that includes upper and lower case letters ? 1010101111 b 1011111 A lower-case “e” @ 1010111101 c 101111 is made up of two A 1111101 d 101101 symbols, however an upper case “E” B 11101011 e 11 has seven symbols f 111101 s 10111 g 1011011 t 101 h 101011 u 110111 www.arrl.org/psk31-spec

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 43 1/11/2020 Grey Code Pg 8-9

 Grey codes are arranged so that only one bit changes between any consecutive value [E8C09]. • Most useful in applications where the data we are sending is counting-up or counting-down.  If a Gray code results in more than one bit being changed between two consecutive characters, it assumes a transmission error has occurred [E8C10].

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 44 1/11/2020 RTTY General Review

 The abbreviation "RTTY" stands for . (G2E07)  FSK vs. AFSK  170 Hz is the most common frequency shift for RTTY emissions in the amateur HF bands. (G2E06)  2125 Hz (mark) or 2295 Hz (space)  LSB is the mode normally used when sending

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 45 1/11/2020 FSK Modes Beyond RTTY General Review

 RTTY uses only two tones (2125 Hz or 2295 Hz)

 MFSK is a more advanced approach to FSK—using multiple tones  For example, MFSK16 uses 16 tones

 The abbreviation "MFSK" stand for Multi (or Multiple) Frequency Shift Keying. (G2E11)

 A major advantage of MFSK16 compared to other digital modes is that it offers good performance in weak signal environments without error correction. (G2E10) Chapter 8 - Digital Modes (G Wolfe - KI0KK) 46 1/11/2020 Bandwidths by Mode General Review

 Various types of modulation have various bandwidths

General Review Width • CW (Continuous Wave or Morse code) ▄ 100 Hz • SSB (Single SideBand) ▄▄▄ 2.8 kHz • AM (Amplitude Modulation)* ▄▄▄▄▄▄ 6 kHz • FM (Frequency Modulation)* ▄▄▄▄▄▄▄▄▄▄ 10 kHz • TV ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ 6 MHz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 47 1/11/2020 Bandwidth (BW) General Review

How wide are you?

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 48 1/11/2020 Digital Signal Bandwidth Pg 8-10

 For a digital signal, the bandwidth is defined as;

 BW = B x K (Equation 8-3)

 Where: • B is the speed of the transmission in baud • K is the shape factor of the keying envelope

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 49 1/11/2020 CW Pg 8-10

 A CW signal has the advantage of being very narrow

 BW = WPM x 0.8 x K (Equation 8.4)

 The “K” is the shape (abruptness) of the keyed waveform. For CW, K is normally a value of 5.

Example  What is the BW of a 13 WPM Morse code signal [E8C05]?  BW = WPM x 0.8 x K = 13 x 0.8 x 5 = 52 Hz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 50 1/11/2020 CW Signal General Review

An oscilloscope is the best instrument to use when

checking the keying waveform of a CW transmitter. (G4B03)

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 51 1/11/2020 CW Bandwidth Pg 8-10

 If the keying waveform has an extremely short rise time and fall time, it will cause key clicks to be head on the signal [E8D04].  To reduce the key clicks, increase the rise and fall times: • A menu-selected adjustment on modern radios [E8D05] • Add capacitance across the key line on an analog radio

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 52 1/11/2020 FSK / AFSK Pg 8-11

 Most Amateur Radio data transmissions employ frequency shift keying [E2E01]

 Direct FSK is created by shifting the frequency  of the transmitter’s oscillator directly.  [E2E11]

 Audio FSK (AFSK) is created by injecting two audio tones into an audio () input.

 The difference between the two tones frequencies is called the shift.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 53 1/11/2020 FSK / AFSK Bandwidth Pg 8-11

FSK or AFSK bandwidth is:  BW = (K x Shift) + B • Where K is a constant that depends on the allowable signal distortion and transmission path. Typically K = 1.2. • B is the symbol rate in baud

Example 8-1  What is the bandwidth of a 170 Hz shift 300-baud ASCII signal?  BW = (1.2 x 170 Hz) + 300 = 504 Hz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 54 1/11/2020 FSK / AFSK Tuning Pg 8-11

Off  RTTY and other FSK/AFSK modes require carful tuning Frequency of the SSB transceiver.

Lissajous Patterns

If one of the ellipses rapidly shrinks in size or disappears, it can indicate selective fading

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 55 1/11/2020 PSK 31 (Phase Shift Keying) General Review Pg 8-12

Thank you Peter Martinez, G3PLX

 The number of data bits sent in a single PSK31 character varies.

 14.070 - 14.100 MHz is the segment of the 20 meter band that is most often used for data transmissions. (G2E04)

14.070 MHz 14.100 MHz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 56 1/11/2020 PSK31 General Review

 The number 31 in the term PSK31 represents the approximate transmitted symbol rate. (G8B10)

Don’t let the smoke out !!!  It is important to know the duty cycle of the data mode you are using when transmitting because some modes have high duty cycles which could exceed the transmitter's average power rating. (G8B08)  If using a 100W transceiver, reduce the transmitter power to 20 – 30 W

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 57 1/11/2020 PSK 31 Shaping

 PSK 31 is the narrowest of all HF Modes! 37.5 Hz typ.

 The bandwidth of a PSK31 signal is minimized by special sinusoidal shaping of the transmitted data symbols

http://forum.radioamateur.ca Chapter 8 - Digital Modes (G Wolfe - KI0KK) 58 1/11/2020 HF Packet General Review

Packet transmissions are more “intelligent” than RTTY or PSK31

 Packets contain header and routing Information. • This may include the packet structure and error correction information

 When the receiving station responds to an ARQ data mode packet containing errors, it requests the packet be retransmitted. (G2E12)

 In the PACTOR protocol, an NAK response to a transmitted packet means the receiver is requesting the packet be re-transmitted. (G2E13)

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 59 1/11/2020 HF Packet Modes

Pg 8-12

 Most HF Packet transmission use FSK at 300 baud. • Contrast that to VHF at 1200 baud [E2E06] • Uses AX.25 same as VHF

 HF Packet has a significantly higher data rate than RTTY, AMTOR and PSK31. [E2D09] • That means it takes up more bandwidth • 40 Byte packets

 HF packet is not very forgiving of fading conditions Chapter 8 - Digital Modes (G Wolfe - KI0KK) 60 1/11/2020 Pactor

 Designed to perform well with noise and weak signals or strong signals

• It supports the transfer of binary files [E2E08]

• Automatically evaluates the conditions and adjust the speed to match.

 Up to 5.2 kbps is achievable in a 2.4 kHz BW

 Winlink is a system of modes and protocols that can be used to exchange files and email. But it does not support keyboard to keyboard communications [E2E05].

 Pactor III and IV is kept proprietary by the German company, SCS Chapter 8 - Digital Modes (G Wolfe - KI0KK) 61 1/11/2020 Multi-tone Protocols Pg 8-13

 One way that Pactor III attains higher speeds is that it uses multiple tones (up to 18 tones)

 MFSK = Multi Frequency Shift Keying

 MFSK16 uses 16 tones and occupies a bandwidth of 316 Hz and runs at abut 63 bps [E2E07] • Supports keyboard-to-keyboard at up to 42 WPM • Forward Error Correction (FEC) sends all data twice with an interleaving technique • Uses a variation of PSK31 Varicode.

 MT63 occupies about 1 kHz of BW and has 64 tones

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 62 1/11/2020 OFDM Modulation Pg 8-13

Orthogonal Frequency Division Multiplexing  Used with wide-band high–speed digital modes  A special type of modulation used with multi-tone modes creates specially-shaped and spaced carrier that interfere with each other as little as possible [E8B08].  Uses subcarriers at frequencies chosen to avoid inter-symbol interference

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 63 1/11/2020 WSJT Protocol Pg 8-14

WSJT is a family of digital protocols developed for demanding VHF/UHF weak-signal communications

 Five different operating modes. Two popular ones are:

 FSK441 for Meteor scatter [E2D01]

 JT65 for EME (moonbounce) [E2D03] • JT65 decodes very well with signals that are well below the noise • JT65 uses 1-minute alternating transmit receive periods synchronized to accurate timing signals

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 64 1/11/2020 WSJT Characteristics Pg 8-14

 WSJT family of protocols use multi-tone AFSK modulation and sophisticated codes to recover signals in the noise floor which are undetectable by the ear [E2D13].  JT65 signals may be detected well below the noise floor [E2D12, E2D14] • Requires accurate timing signal for your PC • Alternating TX periods synchronized to an accurate time clock at 1 minute intervals [E2E03].  FT8 and FT4 are the modes used currently (not reflected in the current text book) Chapter 8 - Digital Modes (G Wolfe - KI0KK) 65 1/11/2020 SDR Based FT8 Operation (Flex 6400)

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 66 1/11/2020 WSJT-X/JT-Alert Using Flex 6400

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 67 1/11/2020 Transmitting Digital Signals Pg 8-14  With AFSK, excessive audio signal levels into the transmitters audio input can overdrive the modulator.  Overdrive creates intermodulation distortion (IMD)  If the transmitter's ALC meter is active during a digital transmission, the signal is overdriving the modulator. (ALC = Automatic Level Control)  Adjust for no ALC reading during Tx [E8D06,E8D07] Chapter 8 - Digital Modes (G Wolfe - KI0KK) 68 1/11/2020 Transmitting Digital Signals Pg 8-14

 A clean PSK signal that is idling will have an IMD level about -30 dB below the main signals. [E8D09]

 There can be several reasons that attempts to initiate contacts with a digital station on a clear frequency are unsuccessful. • Your transmit frequency is incorrect. • You are using a protocol not supported by the other station. • The frequency is being used by another station you are unable to hear.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 69 1/11/2020

PSK31 “Waterfall” with Digipan

IMD Readout

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 70 1/11/2020 PSK31 “Waterfall”

Unmodulated signal - ** IMD Received Readout S/N Signal Readout

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 71 1/11/2020 PSK63 “Waterfall” fldigi

Digital Modes Sounds PSK63 signal

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 72 1/11/2020 Spread Spectrum Pg 8-15

8-4

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 73 1/11/2020 Spread Spectrum Key Points

Pg 8-16

 The signal is spread over a very wide bandwidth by rapidly varying the carrier frequency in a predefined sequence.  Spread spectrum signals appear as wideband noise to a conventional receiver.  The spread spectrum receiver can reject strong undesired signals.  Non-spread signals tend to be suppressed by the spread-spectrum receiver [E8D01]. Spread Spectrum can be used Above 222 MHz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 74 1/11/2020 Frequency Hopping (FH)

Pg 8-16

 Frequency hopping is a form of spreading the RF energy in which the center frequency of a conventional carrier is altered many times a second in accordance with at predetermined pseudo-random code [E8D03].

 The signal may “park” on a http://sss-mag.com/ss.html given frequency for only 10 msec or less, (Dwell Time).

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 75 1/11/2020 Direct Sequence (DS) Pg 8-16

 In direct sequence (DS), a very fast binary stream is used to shift the phase of the modulated carrier [E8D02].

 DS spread spectrum is usually used to transmit http://sss-mag.com/ss.html digital signal's

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 76 1/11/2020 Direct Sequence - WiFi Pg 8-16

 Used in the shared 2.4 GHz band AND 5.6 ghZ  Amateur Radio High-speed mesh networks can be constructed from commercial WiFi routers that have been reprogrammed with custom software to meet Amateur Radio regulations [EC209]  HSMM, BHN, AREN are ham networks.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 77 1/11/2020 Spread Spectrum (Direct Sequence) Pg 8-16

Conventional Signal

DS Spread Spectrum Signals Noise Floor

www.ni.com/white-paper/4450/en/

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 78 1/11/2020 Error Detection and Correction Pg 8-17

 Error detection helps to determine that an error has occurred in a received signal. • Parity bit, single bit errors • Cyclical redundancy check (CRC) can detect multiple bit errors

 Error correction tries to fix the error  Two types of error correction: • Automatic Repeat Request • Forward Error Correction

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 79 1/11/2020 Parity Error Detection Pg 8-17

Remember, an ASCII character consists of 8 symbols:  ASCII letter “A” : __ 1000001 • Insert a zero 01000001 for Even Parity  ASCII letter “C” : __ 1000011 • Insert a one 11000011 for Even Parity  If this is received: 11001011 • An error is declared

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 80 1/11/2020

Error Correction Pg 8-17

Two types of error correction:  Automatic Repeat Request (ARQ) • If the receiving system detects and error, it requests a retransmission of the corrupted packet or message. • Done by sending a NAK (Not Acknowledged message) [E8C08]

 Forward Error Correction (FEC) [E2E02] • Sends some extra data about the information in the message so the receiving station can correct some of the errors. • MFSK 16 sends all data twice • Common FEC codes; Reed-Solomon, Hamming, BCH and Golay codes.

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 81 1/11/2020 What is the relationship between symbol rate and baud? [E8C11]

A. They are the same B. Baud is twice the symbol rate C. Symbol rate is only used for packet-based modes D. Baud is only used for RTTY

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 82 1/11/2020 What is the advantage of including a parity bit with an ASCII character stream? [E8D12]

A. Faster transmission rate B. The signal can overpower interfering signals C. Foreign language characters can be sent D. Some types of errors can be detected

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 83 1/11/2020 What is the necessary bandwidth of a 170-hertz shift, 300-baud ASCII transmission? [E8C06]

A. 0.1 Hz B. 0.3 kHz C. 0.5 kHz D. 1.0 kHz

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 84 1/11/2020 Which of the following indicates likely overmodulation of an AFSK signal such as PSK or MFSK? [E8D06]

A. High reflected power B. Strong ALC action C. Harmonics on higher bands D. Rapid signal fading

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 85 1/11/2020 Section 8-3

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 86 1/11/2020 Fast Scan Television Pg 8-19

 It looks like regular TV  Image Signal Definitions: • US Amateurs use the NTSC signal standard (National Standards Television Committee) [E2B16] • A Frame is made up of 525 horizontal lines [E2B02] • 30 Frames are generated each second [E2B01] • Each Frame consists of two fields, each with 252 ½ lines. • One field contains even numbered lines and the next field contains the odd numbered lines in a NTCS signal. [E2B03]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 87 1/11/2020 Interlaced Scanning Pg 8-20 The dashed line means Beam the beam is turned off. Field 1 262 ½ lines Retrace from Field 1 to Field 2

Field 2 Retrace 262 ½ lines from Field 2 to Field 1

525 total lines Fig 8-7 Chapter 8 - Digital Modes (G Wolfe - KI0KK) 88 1/11/2020 Fields and Blanking Pg 8-20

 At the end of the line, the beam is turned off, or blanked, and returns to the left side to start the next trace.  It is also blanked as it goes from bottom to top.  These timing periods are called horizontal and vertical blanking intervals  Blanking is no longer required for modern displays but the blanking signal is used for timing and synchronization [E2B04]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 89 1/11/2020 The Signal that Produces a Single Line Pg 8-20

Institute of Radio Engineers Time Domain

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 90 1/11/2020 Let’s Add Some Color Pg 8-21

The color is called chroma

The chroma burst helps synchronize the color circuitry 3.5789 MHz [E2B07]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 91 1/11/2020 Vestigial Sideband Pg 8-21

VSB is somewhat like SSB (USB), a portion of the other sideband Sound (LSB) is also transmitted Carrier [E2B06].

VSB uses less bandwidth, but can still be demodulated by simple video detectors [E2B05]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 92 1/11/2020 FM Television & Audio Channels Pg 8-22 & 23  The Video signal is normally an AM signal, but it can also be an FM signal (17 – 21 MHz bandwidth).  Most amateur FM TV equipment operates in the 1.2 GHz, 2.4 GHZ and 10.5 GHz bands [E2B18]

 Audio can be added to a TV signal 3 ways: • Via another band, such as 2 meters (Simplex) • FM audio via a subcarrier – just like a standard analog TV • The AM carrier of the video can also be FM modulated with the sound [E2B08]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 93 1/11/2020 Slow Scan TV (SSTV) Pg 8-23

 Uses 100% transmitter duty cycle • Back the power down!

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 94 1/11/2020 Slow Scan TV (SSTV) Black and White (Monochrome) Pg. 8-23 & 24

 One still image at a time  Horizontal Sync Pulse & Vertical Sync Pulses  Specific (varying) audio frequencies are transmitted using single sideband allowing transmission using SSB modulation. [E2B12] • Line Sync – 1200 Hz [E2B15] • Brightness: Tones of varying frequencies [E2B14] • Black - 1500 Hz • White - 2300 Hz • Gray - In between frequencies  8 Seconds to send one image in 120 lines  Takes about 2 kHz bandwidth

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 95 1/11/2020 Slow Scan TV (SSTV) Black and White (Monochrome) Pg. 8-23 & 24

• Line Sync – 1200 Hz • Brightness: Tones of varying frequencies 1500 Hz is black 2300 Hz is white In between frequencies are various grays

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 96 1/11/2020 Color - SSTV Pg. 8-25

 Scan Line Modes: • 120, 128, 240 or 256 (128 and 256 are the most popular) [E2B13]  Images can take from 12 seconds to > 4 minutes  Vertical Interval Signaling (VIS) to indicate the scan-line mode • Sent during the vertical sync pulse • Operator selects the mode of transmission to use [E2B11]

 Color requires extra bandwidth of 3 kHz [E2B17]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 97 1/11/2020 SSTV Software - MMSTV

SSTV Audio

SSTV Frequencies (MHz) 3.845 7.171 14.230 14.233 21.340 28.680

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 98 1/11/2020 Digital SSTV Pg. 8-25

 DRM (Digital Radio Mondiale) • Developed by commercial SW broadcasters  It only takes a radio and a PC!

Audio Interface

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 99 1/11/2020 Digital SSTV Pg. 8- 25 & 26

 DRM SSTV (amateur) uses about 3 kHz of bandwidth [E2B10]  Permitted in the phone segments of the band  SSTV signals must be no wider than a voice signal using the same modulation mode [E2B19]  The tuning of the radio’s frequency is critical for a good picture  DRM signals may be decoded using software on a PC and a standard HF receiver. [E2B09]

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 100 1/11/2020 What is blanking in a video signal? [E2B04]

A. Synchronization of the horizontal and vertical sync pulses B. Turning off the scanning beam while it is traveling from right to left or from bottom to top C. Turning off the scanning beam at the conclusion of a transmission D. Transmitting a black and white test pattern

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 101 1/11/2020 What is the name of the signal component that carries color

information in NTSC video? [E2B07]

A. Luminance B. Chroma C. Hue D. Spectral Intensity

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 102 1/11/2020 Which of the following is an advantage of using vestigial sideband for standard-fast scan TV transmissions? [E2B05]

A. The vestigial sideband carries the audio information B. The vestigial sideband contains chroma information C. Vestigial sideband reduces bandwidth while allowing for simple video detector circuitry D. Vestigial sideband provides emphasis to sharpen the picture

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 103 1/11/2020 How are analog SSTV television images typically transmitted on the HF bands? [E2B12]

A. Video is converted to equivalent Baudot representation B. Video is converted to equivalent ASCII representation C. Varying tone frequencies representing the video are transmitted using PSK D. Varying tone frequencies representing the video are transmitted using single sideband

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 104 1/11/2020 What signals SSTV receiving equipment to begin a new picture line? [E2B15]

A. Specific tone frequencies B. Elapsed time C. Specific tone amplitudes D. A two-tone signal

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 105 1/11/2020 What is the function of the Vertical Interval Signaling (VIS) code transmitted as part of an SSTV transmission? [E2B11]

A. To lock the color burst oscillator in color SSTV images B. To identify the SSTV mode being used C. To provide vertical synchronization D. To identify the call sign of the station transmitting

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 106 1/11/2020 Next Week – Chapter 9

 Antennas • Basics • Practical Applications • Systems • Transmission Lines • Design

Chapter 8 - Digital Modes (G Wolfe - KI0KK) 107 1/11/2020