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Amateur Extra License Class

Amateur Extra License Class. Chapter 8 Radio Modes and Equipment. Digital Protocols and Modes. Symbol Rate, Data Rate, and Bandwidth Data speeds Air link. Speed that data is transmitted over the air. Data stream. Speed that data is transferred between modem & PC. Data throughput.

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Amateur Extra License Class

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  1. Amateur Extra License Class Chapter 8 Radio Modes and Equipment

  2. Digital Protocols and Modes • Symbol Rate, Data Rate, and Bandwidth • Data speeds • Air link. • Speed that data is transmitted over the air. • Data stream. • Speed that data is transferred between modem & PC. • Data throughput. • Overall data transfer speed.

  3. Digital Protocols and Modes • Symbol Rate, Data Rate, and Bandwidth • Data rate = Bits per second (bps). • Symbol rate = Symbols per second (baud). • Data rate may or may not equal symbol rate. • RTTY or 1200 baud packet • Data Rate = Symbol Rate. • bps = baud • 9600 baud packet • Data Rate = 2 x Symbol Rate. • Bps = 2x baud

  4. Digital Protocols and Modes • Symbol Rate, Data Rate, and Bandwidth • Required bandwidth. • BW = B x K • B = Symbol rate in bauds. • K = Factor relating to shape of keying envelope.

  5. E2D02 -- What is the definition of baud? The number of data symbols transmitted per second The number of characters transmitted per second The number of characters transmitted per minute The number of words transmitted per minute

  6. E8A15 -- What would the waveform of a stream of digital data bits look like on a conventional oscilloscope? A series of sine waves with evenly spaced gaps A series of pulses with varying patterns A running display of alpha-numeric characters None of the above; this type of signal cannot be seen on a conventional oscilloscope

  7. Digital Protocols and Modes • Protocols and Codes • Protocol . • Set of rules controlling the exchange of digital data. • Protocol does not specify method of modulation. • e.g. – Packet uses SSB on HF & FM on VHF.

  8. Digital Protocols and Modes • Protocols and Codes • Code. • Method of changing information to digital data. • Elements  Individual symbols that make up the code. • Code does not specify how data is transmitted. • e.g. – Morse code can be sent by radio, flashing light, or sound.

  9. Digital Protocols and Modes • Protocols and Codes • Morse and varicode. • Most codes use the same number of elements (bits) in each character. • Baudot & ASCII are examples. • Some codes have a variable number of elements (bits) per character. • This is called Varicode. • Morse & PSK31 are examples.

  10. Digital Protocols and Modes • Protocols and Codes • Morse and varicode. • Morse. • 2 Symbols. • ❶ = Signal on. • ⓪ = Signal off. • 5 Elements. • Dit = ❶. • Dah = ❶ ❶ ❶. • Inter-element space = ⓪. • Inter-character space = ⓪⓪⓪. • Inter-word space = ⓪⓪⓪⓪⓪⓪⓪.

  11. Digital Protocols and Modes • Protocols and Codes • Morse and varicode. • PSK31. • 2 elements. • 0. • 1. • Number of elements per character varies from 1 to 10. • Requires less bandwidth. • Two 0’s in a row  Space between characters.

  12. Digital Protocols and Modes • Protocols and Codes • Baudot. • a.k.a. – International Telegraph Alphabet Nr 2 (ITA2) • Elements • Mark. • Space. • Characters. • Combinations of 5 elements each. • Each element = 1 data bit.

  13. Digital Protocols and Modes • Protocols and Codes • Baudot. • Maximum of 32 (25) characters. • Special characters LTRS & FIGS (shift codes) switch between 2 sets of characters. • Maximum of 60 different characters can be represented. • Upper-case letters only. • Start & stop bits frame each character.

  14. Digital Protocols and Modes • Protocols and Codes • ASCII. • 2 Elements • 1. • 0. • Characters  Combinations of 7 elements each. • An 8th bit called a parity bit may be added. • Parity bit used to detect some types of transmission errors. • Or the 8th bit could be an additional data bit. • Each element = 1 data bits.

  15. Digital Protocols and Modes • Protocols and Codes • ASCII. • Maximum of 128 (27) characters. • Both upper & lower case letters can be encoded. • 256 (28) maximum characters (if 8 data bits). • Start bit at beginning of each character. • Stop bit(s) at end of each character. • 1, 1.5, or 2 stop bits can be used.

  16. E2E09 -- Which of the following HF digital modes uses variable-length coding for bandwidth efficiency? RTTY PACTOR MT63 PSK31

  17. E8C01 -- Which one of the following digital codes consists of elements having unequal length? ASCII AX.25 Baudot Morse code

  18. E8C02 -- What are some of the differences between the Baudot digital code and ASCII? Baudot uses four data bits per character, ASCII uses seven or eight; Baudot uses one character as a shift code, ASCII has no shift code Baudot uses five data bits per character, ASCII uses seven or eight; Baudot uses two characters as shift codes, ASCII has no shift code Baudot uses six data bits per character, ASCII uses seven or eight; Baudot has no shift code, ASCII uses two characters as shift codes Baudot uses seven data bits per character, ASCII uses eight; Baudot has no shift code, ASCII uses two characters as shift codes

  19. E8C03 -- What is one advantage of using the ASCII code for data communications? It includes built-in error-correction features It contains fewer information bits per character than any other code It is possible to transmit both upper and lower case text It uses one character as a shift code to send numeric and special characters

  20. E8C12 -- What is the advantage of including a parity bit with an ASCII character stream? Faster transmission rate The signal can overpower interfering signals Foreign language characters can be sent Some types of errors can be detected

  21. Digital Protocols and Modes • Digital Modes • Digital mode consists of protocol plus modulation method. • Can be used to transmit voice, video, or data. • Different FCC emission designators for each type of information. • Digital signals can be regenerated several times without error.

  22. Digital Protocols and Modes • Digital Modes • CW. • Actually an AM emission (A1A). • Speed usually expressed in words per minute (wpm). • Use standard word PARIS. • PARIS contains 50 elements. • 50 elements in 60 seconds = 0.83 baud. • Baud = wpm / 1.2 • Typical shape factor (K) for CW is 4.8. • BW = (wpm / 1.2) x 4.8 = wpm x 4.

  23. Digital Protocols and Modes • Digital Modes • CW. • Keying envelope  Shape of the leading edge and the trailing edge of each element. • Changing keying envelope changes K and consequently changes bandwidth. • The slower the rise & fall times of the signal, the narrower the bandwidth.

  24. Digital Protocols and Modes • Digital Modes • CW. • Keying envelope & resulting bandwidth when the rise & fall times are 2 ms.

  25. Digital Protocols and Modes • Digital Modes • CW. • Keying envelope & resulting bandwidth when the rise & fall times are 8 ms.

  26. Digital Protocols and Modes • Digital Modes • FSK/AFSK. • FSK = shifting frequency of oscillator (F1B or F1D). • AFSK = modulating SSB transmitter with frequency-shifted tones (J1B or J1D). • AFSK with properly adjusted SSB transmitter is not distinguishable from FSK. • BW = (K x Shift) + B. • Typical value for K is 1.2. • BW = (1.2 x 170) + 45.45 ≈ 250 Hz. • Selective fading.

  27. Digital Protocols and Modes • Digital Modes • PSK31. • G3PLX developed PSK31 for keyboard-to-keyboard communications. • PSK = phase-shift keying. • 31 = data rate (31.25 baud). • Uses a variable-length code (Varicode). • Most common characters have shortest code. • Uses 00 as separator between characters. • Bandwidth ≈ 37.5 Hz. • Narrowest of all HF digital modes, including CW. • Special sinusoidal shaping of characters minimizes bandwidth.

  28. Digital Protocols and Modes • Digital Modes • HF Packet. • Uses AX.25 protocol (same as VHF packet). • Limited to 300 baud. • Mostly FSK at 300 baud. • VHF packet uses AFSK at 1200 baud. • Not well suited for HF propagation conditions. • Needs good conditions with minimal fading. • Higher data rate than RTTY, AMTOR, or PSK31 when conditions are good.

  29. Digital Protocols and Modes • Digital Modes • PACTOR (J2D). • PACTOR-I developed by DL6MAA & DK4FV. • Overcome shortcomings of AMTOR & HF packet. • Works well in weak-signal & high-noise conditions. • PACTOR-II & PACTOR-III used today. • Automatic repeat request (ARQ) used to eliminate errors. • Adjusts speed (“trains”) to match conditions. • 5 kbps data rates possible. • Used to transfer binary files.

  30. Digital Protocols and Modes • Digital Modes • Winlink. • Not really a mode but a system of modes, protocols, & Internet services to provide e-mail & file transfer services. • One of the more poplar applications of PACTOR. • Does NOT support direct keyboard-to-keyboard operation.

  31. Digital Protocols and Modes • Digital Modes • Multitone Protocols. • MFSK16. • Uses 16 tones to modulate signal. • Bandwidth ≈ 316 Hz. • Data rate ≈ 63 bps. • Includes error correction. • MT63. • Uses 64 tones to modulate signal. • Bandwidth ≈ 1 kHz. • Includes extensive error correction.

  32. Digital Protocols and Modes • Digital Modes • WSJT Protocol. • Developed by K1JT for weak-signal VHF/UHF work. • Family of 5 digital protocols. • FSK441 for meteor scatter. • JT65 for moonbounce (EME). • Will copy without error signals below the noise level! • JT65-HF developed for HF operations. • JT6M for 6m meteor scatter. • EME for monitoring your own signals bounced off the moon. • CW for 15 wpm EME QSO’s.

  33. Digital Protocols and Modes • Digital Modes • Transmitting digital mode signals. • Transmitted signal quality EXTREMELY important! • Do NOT overdrive transmitter audio! • After setting ALC & microphone gain, perform on-air test. • 2nd receiver. • Nearby station.

  34. E2D01 -- Which of the following digital modes is especially designed for use for meteor scatter signals? WSPR FSK441 Hellschreiber APRS

  35. E2D03 -- Which of the following digital modes is especially useful for EME communications? FSK441 PACTOR III Olivia JT65

  36. E2D09 -- Under clear communications conditions, which of these digital communications modes has the fastest data throughput? AMTOR 170-Hz shift, 45 baud RTTY PSK31 300-baud packet

  37. E2D12 -- How does JT65 improve EME communications? It can decode signals many dB below the noise floor using FEC It controls the receiver to track Doppler shift It supplies signals to guide the antenna to track the Moon All of these choices are correct

  38. E2E01 -- Which type of modulation is common for data emissions below 30 MHz? DTMF tones modulating an FM signal FSK Pulse modulation Spread spectrum

  39. E2E04 -- What is indicated when one of the ellipses in an FSK crossed-ellipse display suddenly disappears? Selective fading has occurred One of the signal filters has saturated The receiver has drifted 5 kHz from the desired receive frequency The mark and space signal have been inverted

  40. E2E06 -- What is the most common data rate used for HF packet communications? 48 baud 110 baud 300 baud 1200 baud

  41. E2E07 -- What is the typical bandwidth of a properly modulated MFSK16 signal? 31 Hz 316 Hz 550 Hz 2.16 kHz

  42. E2E08 -- Which of the following HF digital modes can be used to transfer binary files? Hellschreiber PACTOR RTTY AMTOR

  43. E2E10 -- Which of these digital communications modes has the narrowest bandwidth? MFSK16 170-Hz shift, 45 baud RTTY PSK31 300-baud packet

  44. E2E11 -- What is the difference between direct FSK and audio FSK? Direct FSK applies the data signal to the transmitter VFO Audio FSK has a superior frequency response Direct FSK uses a DC-coupled data connection Audio FSK can be performed anywhere in the transmit chain

  45. E2E12 -- Which type of digital communication does not support keyboard-to-keyboard operation? Winlink RTTY PSK31 MFSK

  46. E4A09 -- Which of the following describes a good method for measuring the intermodulation distortion of your own PSK signal? Transmit into a dummy load, receive the signal on a second receiver, and feed the audio into the sound card of a computer running an appropriate PSK program Multiply the ALC level on the transmitter during a normal transmission by the average power output Use an RF voltmeter coupled to the transmitter output using appropriate isolation to prevent damage to the meter All of these choices are correct

  47. E8A12 -- What type of information can be conveyed using digital waveforms? Human speech Video signals Data All of these choices are correct

  48. E8A13 -- What is an advantage of using digital signals instead of analog signals to convey the same information? Less complex circuitry is required for digital signal generation and detection Digital signals always occupy a narrower bandwidth Digital signals can be regenerated multiple times without error All of these choices are correct

  49. E8C04 -- What technique is used to minimize the bandwidth requirements of a PSK31 signal? Zero-sum character encoding Reed-Solomon character encoding Use of sinusoidal data pulses Use of trapezoidal data pulses

  50. E8C05 -- What is the necessary bandwidth of a 13-WPM international Morse code transmission? Approximately 13 Hz Approximately 26 Hz Approximately 52 Hz Approximately 104 Hz

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