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Soundcard Digital Communications

Soundcard Digital Communications. Scott Honaker N7WLO. Connecting Your Radio. Radio connections should be made in the following order Power Supply Antenna Computer Mike Key – if you must A computer connected to the radio is the second only to the antenna in importance.

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Soundcard Digital Communications

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  1. Soundcard Digital Communications Scott Honaker N7WLO

  2. Connecting Your Radio • Radio connections should be made in the following order • Power Supply • Antenna • Computer • Mike • Key – if you must • A computer connected to the radio is the second only to the antenna in importance Scott Honaker - N7WLO

  3. Evolution of Acronyms • Human transmitted digital • CW – Operator determines performance • Machine sent digital • RTTY – Baudot 5-bit code • Machine sent corrected data packets • Packet – APRS – TCP/IP • High noise immunity RTTY replacements • PSK31 – QPSK – MFSK – MT63 • Intermittent channel weak-signal modes • HSCW – FSK441 (WSJT) • Extreme weak signal mode • JT44 (WSJT) Scott Honaker - N7WLO

  4. Soundcard Packet • AGW Packet Engine for 1200 or 9600 • Supports Terminal, TCP/IP, DX Cluster, Digipeater • APRS Software support via APRSPoint, UI View and WinAPRS • Supports multiple simultaneous connections • Allows remote use over a network/Internet Scott Honaker - N7WLO

  5. PSK 31 • Designed by Peter G3PLX • Based on the RTTY mode of operation useful for live keyboard to keyboard QSO • Works at 31.25 bauds • Uses varicode character coding providing 50wpm • Give very good copy under low Eb/No numbers and is thus suitable for QRP • That instead of using FSK or on/off keying uses BPSK or QPSK with a Viterbi decoder • Uses advanced DSP and narrow band (31 Hz!!) techniques Scott Honaker - N7WLO

  6. PSK 31 Frequencies Scott Honaker - N7WLO

  7. QPSK • Quadernary Phase-Shift Keying • Four phases instead of 2 for PSK • Extra capacity used for error-correction • Improvements of up to 5 fold in error-rate • Not as good for QRP (3dB hit) • Extra transmission delay • More frequency sensitive (within 4Hz) • Must use correct sideband • Start BPSK and switch to QPSK Scott Honaker - N7WLO

  8. MFSK 16 • Sixteen tone carriers, ~16Hz apart • 42 WPM in 316Hz with FEC • High rejection of pulse and broadband noise due to narrow bandwidth per tone • Low baud rate for sensitivity and multi-path rejection - data bit rate higher than symbol baud rate • Tolerance of ionospheric effects such as doppler, fading and multi-path Scott Honaker - N7WLO

  9. MT 63 • Uses 64 tone carriers • 100 WPM at ~1KHz wide • Even more FEC than MSFK • Up to 25% of data can be destroyed • Long delay due to heavy error-correction • ID is generally done in CW Scott Honaker - N7WLO

  10. HamScope Software Scott Honaker - N7WLO

  11. High Speed CW • Used for Meteor-Scatter • Machine sent 100-2000 WPM • Allows contacts over paths lasting only seconds – “pings” • No error correction • Transmission schedule negotiated • No random QSOs Scott Honaker - N7WLO

  12. FSK 441 - WSJT • Like HSCW, one uses a high-speed loop to complete a QSO over several short bursts of signal • 100% duty cycle, so no extra energy wasted by On/Off keying • More user-friendly interface--like RTTY or PSK31 modes • Much better S/N than HSCW at same speed • Each character takes about 2.3ms to send with four tones. That’s 441 baud. Scott Honaker - N7WLO

  13. FSK 441 Spectral Display Scott Honaker - N7WLO

  14. JT 44 - WSJT • Uses long term signal averaging to recover a signal that is up to 30dB below the noise floor! • Humans have “short ears” limited by their sensory memory—they can only analyze a signal in a small timeframe • Computers can analyze in relatively large timeframes • Inspired by the PUA43 mode (with dedicated hardware) • Uses 44 tones, one for each character in the PUA43 alphabet (same as FSK441), plus a synchronization tone. Each character is assigned a unique frequency • Slow transmission speed: 5.38 baud • Highly redundant (FEC) Scott Honaker - N7WLO

  15. JT 44 Signal Decoding Scott Honaker - N7WLO

  16. JT44 – Terrestrial Use • JT44 works well on troposcatter paths that are too short for MS enhancement • Several operators have used it on 6m for borderline TE, and marginal Es openings. • Microwave non-line-of-sight paths • Could be a good way of overcoming atmospheric absorption above 10GHz • Contest stations can make otherwise impossible contacts Scott Honaker - N7WLO

  17. JT44 – EME Use • JT44’s ability to recover extremely weak signals makes it ideal for EME • Most activity by arranged schedule. • 144MHz is the most popular band. • Also operation on 50 MHz, 432MHz, and 1296 MHz so far…. • A pair of single-yagi stations should be able to work each other, with QRO power • Portable EME operation can be a reality Scott Honaker - N7WLO

  18. What Does It Take? • Windows PC • Windows 98 or higher recommended • Pentium 150MHz or better • SoundBlaster compatible soundcard • Most laptop sound systems work • More expensive cards have less noise and are more frequency stable/accurate • Interface cabling • RigBlaster or Rascal interfaces not necessary Scott Honaker - N7WLO

  19. 144.390 Computer/Radio Interfacing Line or Speaker Output Line or Mike Input Interface COM Port COM Port Push-to-talk (PTT) Receive Audio Transmit Audio Computer ControlCI-V or CAT Scott Honaker - N7WLO

  20. Soundcard Interfacing • Most radios have audio in/out PTT on back via a Data or AUX port • These line level in/outs are best • Mike/speaker levels can be used with appropriate attenuation • PTT support generally via transistor or optoisolator switch • PTT can be done with CAT port but requires radio-specific software Scott Honaker - N7WLO

  21. PTT Switching Scott Honaker - N7WLO

  22. Soundcard Interface Scott Honaker - N7WLO

  23. Field Day Use on VHF • VHF/UHF QSO counts are notoriously low • The vast majority of QSO are voice • FD scoring gives 1 point for voice, 2 points for CW and 2 points for data QSOs • Typical VHF QSOs might be 80 – all voice • If 50% added soundcard modes, we get 5 points per station rather than 1 • 80 points becomes 240 points • This doesn’t count QSOs now possible with PSK Scott Honaker - N7WLO

  24. Remote Control • Radio tuning, antenna rotation, transmission and reception are all computer controllable • This software is easily remote controlled via Terminal Server or NetMeeting • Access can be via LAN or Internet • There are shared radios on the Internet Scott Honaker - N7WLO

  25. Resources • AGW Packet Engine • http://www.raag.org/sv2agw/inst.htm • PSK 31 Home page • http://aintel.bi.ehu.es/psk31.html • WSJT Home Page • http://pulsar.princeton.edu/~joe/k1jt/ • HamScope Software • http://www.qsl.net/hamscope/ • MixW Software • http://www.tav.kiev.ua/~nick/mixw/mixw.htm • Rascal Interface • http://www.packetradio.com/rascalmkv.htm Scott Honaker - N7WLO

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