1 / 33

Digital Communications

Digital Communications. El Paso Amateur Radio Club August 22, 2003 Tom, WB5QLR. Repeat Offender – 8/9/00. Digital Modes. RTTY PSK31 PSK63 MFSK WSJT. Computer Based. Hardware requirements SoundBlaster compatible sound card PC capable of running Win95/98 PTT switching mechanism.

bonner
Download Presentation

Digital Communications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Digital Communications • El Paso Amateur Radio Club • August 22, 2003 • Tom, WB5QLR

  2. Repeat Offender – 8/9/00

  3. Digital Modes • RTTY • PSK31 • PSK63 • MFSK • WSJT

  4. Computer Based • Hardware requirements • SoundBlaster compatible sound card • PC capable of running Win95/98 • PTT switching mechanism

  5. Computer Based • Software • Software for mode of operation • Might have multiple mode in same program

  6. What is NOT Necessary • Heavy teletype • TNC • Special tuning scopes

  7. Main Point #1 • Digital modes can be implemented totally with: • Computer • Sound Card • Software • Simple PTT circuit from serial port

  8. Connections • Receiver audio out into Computer line in • Preferable if audio out is independent of AF gain • Could also run through a 1:1 audio transformer to help isolate grounds

  9. Connections • Computer speaker in Transmitter audio • Use a resistor and 1:1 audio transformer • Optional trimmer pot to control audio level

  10. Audio Connection

  11. Connections • Computer serial port to Transmitter PTT • Circuit includes: • 1 resistor • 2 diodes • 1 transistor • Optional DPST to switch between 2 inputs from serial port

  12. PTT Connection

  13. RigBlaster Interface

  14. RigBlaster Interface - Back

  15. RTTY • Convention is LSB • Been around for a long time

  16. RTTY

  17. PSK and sound • Convention is USB • Most around 14.070 MHz and up • Phase shifted • Variable code – combination of Baudot and Morse • Band width is 31.25 cycles wide • Efficiency ranks with CW • Implemented completely with sound card and software

  18. PSK Tuning – Old Style

  19. PSK Tuning – New Style

  20. PSK Tuning – New Style

  21. PSK Frequencies • 3.580 MHz • 7.080 MHz • 10.140 MHz • 14.070 MHz • 18.100 MHz • 21.080 MHz • 28.120 MHz

  22. PSK 63 • 100 wpm character transmission speed for contest exchanges and macro transmission versus RTTY at 60 wpm • Only 1/5 the bandwidth of RTTY - capable of displaying 24 signals simultaneously on a waterfall or spectrum display • Capable of color thumbnail portrait transmission in less than 2 minutes • Faster sync recovery than RTTY, resulting in fewer errors

  23. PSK 63 • Requires much less power than RTTY for the same communications performance • Identical to PSK31 except for a wider bandwidth of 63 Hz • Improved polar path performance compared to PSK31 • Works with any soundcard-equipped Windows computer and SSB transceiver • High-speed transmission of macros and brag files

  24. MFSK – Mutiple Frequency Shift Keying • A Weak signal digital mode • Advantages • High rejection of pulse and broadband noise due to narrow receiver bandwidth per tone • Low baud rate for sensitivity and multi-path rejection - data bit rate higher than symbol baud rate • Constant transmitter power • Tolerance of ionospheric effects such as doppler, fading and multi-path

  25. MFSK • Disadvantages • Narrow spacing and narrow bandwidth of the individual tone detectors • Drift can be a problem and accurate tuning is essential.

  26. WSJT – Weak Signal by W1JT • Four Modes • FSK441 – Meteor Scatter • JT6M – Meteor Scatter for 6M • JT44 – Tropo and EME • EME Echo – Listening to your EME return • Competitive with 50 watts and 10-11 element beam

  27. Bandpass Comparisons

  28. Resources • RTTY/PSK software • TrueTTY - www.dxsoft.com • 3KHz band pass • On RTTY, both FSK and AFSK • RigBlaster Interface • www.westmountainradio.com/RIGblaster.htm

  29. Resources • PSK Home Page • www.aintel.bi.ehu.es/psk31.html • PSK only software • DigiPan – www.digipan.net • WinPSKse - www.winpskse.com • Other Sites • Great overview - www.qsl.net/kk7lk/psk31.htm • Interface details - www.w5bbr.com/psk31.html

  30. Resources • MSFK • http://www.qsl.net/zl1bpu/MFSK/ • Software – Stream - http://iz8bly.sysonline.it/Stream/index.htm • WSJT • http://pulsar.princeton.edu/~joe/K1JT/ • http://www.qsl.net/wa5ufh/WSJTGROUP/WSJTGROUP.htm • Ping Jockey - http://www.pingjockey.net/cgi-bin/pingtalk

  31. Resources • Articles • QST May, 1999 pg 41-44 • QST May, 2000 pg 42-45 • Book • ARRL’s HFDigital Handbook

  32. Non Digital Resources • Logging software • XMLog - www.xmlog.com • Multiple logs books • Easy reference to notes • Logger - www.qsl.net/kc4elo/ • Little higher level • Includes PSK • Contesting Software – www.writelog.com • Includes RTTY and PSK

  33. Main Point #2 • Fun • Easy • On air demonstration • Slides and references at www.striplingdata.com/w5es

More Related