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GENERAL CLASS Chapter 2

GENERAL CLASS Chapter 2. Need to add charts on emergency operations. Definition of Terms. Modes – ways of conveying information. Modulation – the process of impressing or overlaying information to be conveyed onto the RF carrier wave.

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GENERAL CLASS Chapter 2

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  1. GENERAL CLASSChapter 2 Need to add charts on emergency operations

  2. Definition of Terms • Modes – ways of conveying information. • Modulation – the process of impressing or overlaying information to be conveyed onto the RF carrier wave. • RF carrier – the radio signal that is sent from the transmitter to receiver. • Bandwidth – the amount of spectrum required (occupied) to convey the information.

  3. Voice Modulation • AM – Amplitude Modulation • SSB – Single Side Band • FM – Frequency Modulation • PM – Phase Modulation

  4. HF Operation • On HF operations are not Chanalized. • It is important to understand band plans • DX window use for international QSO • On HF voice communication is SSB • Use LSB below 10 MHz • Use USB above 10MHz • No one has priority on a frequency • If frequency in use look elsewhere • Use Common Curtisy

  5. HF QSOs • Always ask if frequency is in use before CQ • QRL on cw or digital • To start call CQ or answer a CQ • Break into ongoing QSO • Give your call between transmissions • Be courtious • Call at end of QSO

  6. Keeping a Logbook • Most HF operators keep a logbook • Date time(UTC) mode call report • No longer required • Use to confirm QSOs • Useful record in event of FCC inquery

  7. Managing Interference • HF bands not chanelized, you need to be aware of bandwidth • SSB 3kHz • CW 150 Hz (try to space 500hz) • RTTY 200hz • Psk31 50hz • Band conditions change use curitesy

  8. CW and Digital Q signals • QRL – Is this frequency in use. • QRZ – who is calling me • QSY – change frequency • QRS – send slower • QRQ – send faster • QSL – I acknowledge receipt • QSK – the ability to receive between sent tokens • QRV – Ready to receive

  9. CW / Digital Prosigns • K – End of transmission • KN – End of transmission listen for specific station • CL – Closing Station • AR – End of message

  10. AM • Vary the amplitude of the RF carrier in step with the applied voice waveform.

  11. SSB • SSB – one sideband is filtered out, as well as the carrier (suppressed when no audio is present).

  12. SSB Transmitter • This allows for available power to be concentrated into the remaining sideband.

  13. SSB Receiver • The missing sideband is recreated in the receiver as a mirror image of the sideband sent. • (through a beat frequency oscillator (BFO) and another mixer)

  14. FM/PM • Frequency is varied in step with the voice waveform. • Large amplitude – large frequency shift (deviation). • Small Amplitude – small frequency deviation. • Important point – voice volume depends on frequency deviation, not amplitude variation.

  15. FM/PM • The deviation setting between the TX and RX equipment must match for effective operation. • TX narrow, RX wide – low volume. • TX wide, RX narrow – splatter, distortion, clipping.

  16. Data Transmission • CW – Morse Code • RTTY –Radioteletype • AMTOR – Amateur Teleprinting Over Radio • PACTOR • PSK31 • Packet

  17. CW • Data modulation concerns two states, on and off. • Morse code is simplest data mode, you turn the RF carrier on and off to form dits and dahs. • A BFO in the receiver adds some audio to the dits and dahs so that you hear a tone in the speaker.

  18. Data Modulation Techniques • FSK (frequency shift keying) • AFSK (audio frequency shift keying) • PSK (phase shift keying) • All techniques depend on one state for on, the other state for off. • Techniques used to “capture” the receiver circuitry to improve signal to noise ratio (and therefore accuracy). • All ?SK modes are 100 percent duty cycle.

  19. RTTY • Based on a 5 bit code called BAUDOT. • Used primarily on HF. • Comes from the old mechanical teletype days though now mostly by computer. • Uses FSK 170 Hz shift on HF. • No error correction capabilities.

  20. AMTOR • Two modes of AMTOR • ARQ (Automatic Repeat reQuest) • FEC (Forward Error Correction)

  21. AMTOR ARQ • ARQ • TX and RX linked by handshaking. • Three letters sent at a time with error check. • Letters repeated until timeout or received correctly. • Almost 100%.

  22. AMTOR FEC • FEC • No handshaking. • Three letters sent, then the second 3 letters, then first 3 repeated and so-on. • RX compares 3 letter pairs and prints the best copy. • Not 100% but better than RTTY.

  23. PACTOR • Similar to AMTOR but more and variable group length to take advantage of changing band conditions. • Code more computer like which allows for easier transmission of computer compatible data. • Very good error correction.

  24. PSK31 • Similar to RTTY in that no handshake between RX/TX. • Code is a 7 bit code, therefore more characters (upper and lower case etc.). • Error correction allowed by transmitting operation (backspace and delete). • Transmission technique requires very little bandwidth. • Many, many contacts allowed simultaneously in the same space taken by one voice QSO.

  25. Packet • Very much like computer communication mode. • HF and VHF. • Full error correction. • Forward and relay capabilities. • Requires a smart modem (TNC) or specialized software that takes advantage of sound card technology.

  26. Video • SSTV (Slow Scan TV) – sending snap-shots. • Generally an HF mode. • Uses SSB for transmission. • Gray (color) scale represented by amplitude of the wave, low – black, high – white. • Picture built one line at a time.

  27. Quiz Time

  28. Chapter 2 Answers-1 • Section 2.1 • G1B08 – A B C D • G2A01 – A B C D • __PG 2-2_____ • G2A02 – A B C D • G2A03 – A B C D • G2A04 – A B C D • G2A05 – A B C D • G2A06 – A B C D • G2A07 – A B C D • __PG 2-3_____ • G2A08 – A B C D • G2A09 – A B C D • G2A10 – A B C D • G2A11 – A B C D • G2B01 – A B C D • G2B03 – A B C D

  29. Chapter 2 Answers-2 • __PG 2-4_____ • G2B04 – A B C D • G2B05 – A B C D • G2B06 – A B C D • G2B07 – A B C D • G2B08 – A B C D • G2C01– A B C D • __PG 2-5_____ • G2C02– A B C D • G2C03– A B C D • G2C04– A B C D • G2C05– A B C D • G2C06– A B C D • G2C07– A B C D • G2C08– A B C D

  30. Chapter 2 Answers-3 • __PG 2-6_____ • G2C09– A B C D • G2C10– A B C D • G2C11– A B C D • G2D08– A B C D • G2D09– A B C D • G4A10– A B C D • __PG 2-7_____ • Section 2.2 • G2E04– A B C D • G2E07– A B C D • G2E08– A B C D • G2E09– A B C D • G2E11– A B C D • G8B10– A B C D

  31. Chapter 2 Answers-3 • __PG 2-8_____ • Section 2.3 • G1B04– A B C D • G2B02– A B C D • G2B09– A B C D • G2B10– A B C D • G2B11– A B C D • __PG 2-9_____ • G2B12– A B C D

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