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Introduction to Data Modes: Unlocking New Dimensions in Radio Communication

This comprehensive guide by Mike Richards (G4WNC) explores the world of data modes in amateur radio. It highlights why operators should embrace data modes for efficient spectrum use, effective long-distance communication, and cost-effective solutions. The presentation covers core concepts such as modulation techniques (including PSK-31 and V4Chat), error correction methods, and practical systems that enhance radio operating experiences. Learn to navigate through encoding alphabets, decoding protocols, and how to handle errors in transmission.

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Introduction to Data Modes: Unlocking New Dimensions in Radio Communication

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  1. Introduction to Data Modes Mike Richards G4WNC

  2. The Menu • Data Modes - Why Bother? • Data Modes Flow Chart • Technical bits. Data – Alphabets – Error Correction – Modulation • Practical Systems - PSK-31 • Practical Systems - V4Chat • Summary & Questions Mike Richards - Introduction to Data Modes (HFC 2011)

  3. Data Modes - Why Bother? • Self Education • A new dimension to your radio operating • Efficient use of spectrum • Can be good for DX • You can do it for free! Mike Richards - Introduction to Data Modes (HFC 2011)

  4. Data Modes - Overview Encoding Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet conversion Alphabet conversion Error protection Error correction Tone decoder Tone generation R A D I O L I N K Decoding Mike Richards - Introduction to Data Modes (HFC 2011)

  5. Keyboard to Serial Data A Keyboard ASCII 65 128 64 32 16 8 4 2 1 0 1 0 0 0 0 0 1 Serial data 0 1 0 0 0 0 0 1 Mike Richards - Introduction to Data Modes (HFC 2011)

  6. Data Modes - Alphabets Encoding Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet conversion Alphabet conversion Error protection Error correction Tone decoder Tone generation R A D I O L I N K Decoding Mike Richards - Introduction to Data Modes (HFC 2011)

  7. Alphabets • Why change the alphabet? • RTTY - limited to 5 bits • PSK31 – uses Varicode • Amtor & Pactor – error detection code Mike Richards - Introduction to Data Modes (HFC 2011)

  8. Data Modes - Errors Encoding Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet conversion Alphabet conversion Error protection Error correction Tone decoder Tone generation R A D I O L I N K Decoding Mike Richards - Introduction to Data Modes (HFC 2011)

  9. Dealing with errors – 1: SSB • Ignore • Rely on distant operator to work-out errors • Repeat • Say everything twice • Short messages and confirm • Bit at a time and confirm each transmission • Use phonetics • Add more information to get through Mike Richards - Introduction to Data Modes (HFC 2011)

  10. Dealing with errors – 2: Data Modes • Repeats • Used in simple FEC – 3 characters at a time, delayed by 3 characters • Automatic Repeat Request (ARQ) • Send short bursts and await confirmation • Forward Error Correction • Add extra information Mike Richards - Introduction to Data Modes (HFC 2011)

  11. Dealing with Errors – 3: Repeats Simple Forward Error Correction Original text Repeated text Transmitted text ~ = Data padding Used for AMTOR FEC and NAVTEX marine safety system Mike Richards - Introduction to Data Modes (HFC 2011)

  12. Dealing with Errors – 4: Automatic Repeat Request (ARQ) • Send data in short bursts • Wait for acknowledgement • Repeat on request Data 1 Data 2 Data 3 Data 2 Originator ACK ACK ACK ARQ Distant Stn • Very reliable • Excellent with deep QSB • Say everything once • Only handles 1:1 QSOs • Amtor, Pactor, Packet Mike Richards - Introduction to Data Modes (HFC 2011)

  13. Dealing with Errors – 5: Forward Error Correction (FEC) • Convolutional Coding • Digital version of phonetics • NASA Voyager algorithm • 2 bits out for each 1 input • Output pattern dependent on previous 6 bits • Rate ½ constraint 7 • Used in MFSK16, ROS, WINMOR, V4Chat, QPSK31, JT65A • Walsh functions • Used in Olivia and MT63 1 0 1 0 1 0 1 0 Rate ½ constraint 3 encoder 10 01 01 10 00 11 11 00 Mike Richards - Introduction to Data Modes (HFC 2011)

  14. Data Modes – Modulation Systems Encoding Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet Conversion Alphabet conversion Alphabet conversion Error protection Error correction Tone decoder Tone generation R A D I O L I N K Decoding Mike Richards - Introduction to Data Modes (HFC 2011)

  15. Simple Modulation Systems - FSK Frequency Shift Keying (FSK) 1 Original Data 0 +170Hz Carrier Frequency fc Audio Frequency Shift Keying (FSK) 1445Hz Audio Tones 1275Hz Mike Richards - Introduction to Data Modes (HFC 2011)

  16. Simple Modulation Systems - PSK Phase Shift Keying (PSK) 1 Original Data 0 180 Carrier phase 0 Mike Richards - Introduction to Data Modes (HFC 2011)

  17. Practical Systems – PSK31 • Custom designed for keyboard QSOs • Narrow bandwidth - just 31Hz • Entire 20m activity in one speech channel! • Perfect for normal typing speeds • No error correction – keeps it simple • Most popular mode • Can always find activity Mike Richards G4WNC- Introduction to Data Modes (HFC 2011)

  18. PSK-31 with DigiPan Mike Richards - Introduction to Data Modes (HFC 2011)

  19. Practical Systems V4Chat • Brand new mode in development • Modern AMTOR replacement • Includes FEC and ARQ modes • Derived from the V4 Terminal Node Controller • Activity centred on 14073kHz Mike Richards - Introduction to Data Modes (HFC 2011)

  20. V4Chat in action Mike Richards - Introduction to Data Modes (HFC 2011)

  21. Tips & Questions • Choose the right mode • Keep the power down • Don’t over modulate • Avoid stored text – talk to people • Give useful signal reports • Have a go – it’s fun • Any Questions? • Don’t forget to pick-up a handout Mike Richards - Introduction to Data Modes (HFC 2011)

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