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WSJT Meteors, Moonbounce, and More …

WSJT Meteors, Moonbounce, and More …. JT65. JT6M. FSK441. Joe Taylor, K1JT. Mid-Atlantic States VHF Conference September 24, 2005. How to push the DX Limits on VHF/UHF bands . Wait for a band opening Get a bigger amplifier Bigger antenna, better feedline, low-noise preamp, …. – or –.

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WSJT Meteors, Moonbounce, and More …

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  1. WSJTMeteors, Moonbounce, and More … JT65 JT6M FSK441 Joe Taylor, K1JT Mid-Atlantic States VHF Conference September 24, 2005

  2. How to push the DX Limitson VHF/UHF bands • Wait for a band opening • Get a bigger amplifier • Bigger antenna, better feedline, low-noise preamp, … – or – • Use efficient coding and modulation

  3. WSJT: What is it? • A computer program • Provides modulation and encoding/decoding, as in PSK31 • Offers several modes • FSK441 for meteor scatter • JT6M for ionoscatter on 6m • JT65 for EME • CW for EME

  4. Requirements for optimizing minimal QSOs • Meteor scatter • Speed > 100 cps • Good copy at 0 dB S/N in SSB BW • EME • Speed ≈ 0.3 cps • Good copy at –20 to –30 dB S/N

  5. Design of FSK441 • Four-tone FSK: 882, 1323, 1764, 2205 Hz • Three tones or “symbols” per character • Keying rate 441 baud • Transmission rate 147 cps • Detection bandwidth 4 × 441 Hz • Short messages sent repeatedly • 30s T/R sequences

  6. Design of JT6M • 44-tone FSK • Sync tone every 3rd symbol • Keying rate 21.5 baud • Detection bandwidth 44 × 21.5 Hz • Short messages sent repeatedly • Message averaging • 30 s T/R sequences

  7. Design of JT65 • Structured messages • Sync tone plus 64 data tones • Keying rate 2.7 baud • Detection BW 66 × 2.7/5.4/10.8 Hz • Powerful Error-Correcting Code • Short messages: RO, RRR, 73 • T/R sequences 60 s

  8. FEC in JT65 • Seems like magic ? • Mathematically rigorous … • RS(63,12) code, 6-bit symbols • Corrects 25 (or even more) symbol errors • “Deep search” does 4 dB better • Soft-decision decoder by Koetter and Vardy (US patent #6,634,007)

  9. Compressed and Encoded JT65 Messages Message Compressed to 72 bits (12 six-bit symbols) ---------------------------------------------------------------------- 1. G3LTF DL9KR JO40 61 37 30 28 9 27 61 58 26 3 49 16 2. G3LTE DL9KR JO40 61 37 30 28 5 27 61 58 26 3 49 16 3. G3LTF DL9KR JO41 61 37 30 28 9 27 61 58 26 3 49 17 First 21 (of 63) encoded channel symbols, including FEC: ---------------------------------------------------------------------- 1. 14 16 9 18 4 60 41 18 22 63 43 5 30 13 15 9 25 35 50 21 0 ... 2. 20 34 19 5 36 6 30 15 22 20 3 62 57 59 19 56 17 35 2 9 41 ... 3. 47 27 46 50 58 26 38 24 22 3 14 54 10 58 36 23 63 35 41 56 53 ...

  10. Does it work ? • Several thousand users, worldwide • You can work “anyone” at 500 to 1300 miles on 6 or 2m, any time • K1JT on 2m (4 x 9 el, 700 W): • WAC ─ EME initials 109 • DXCC 39 ─ Grids 268 • WAS 42

  11. Measured sensitivity Measured sensitivity of JT65

  12. Measured “sync and shorthand” sensitivity

  13. What equipment do I need? • Windows computer with sound card • Minimum: 400 MHz Pentium II, 64 MB RAM (you’ll be happier with more) • WSJT software: free download • Simple interface, serial port to PTT • Audio connections, sound card to radio

  14. Installing WSJT • Free download from WSJT home page: http://pulsar.princeton.edu/~joe/K1JT • Self-extracting EXE file — “click-click!” • Includes a detailed manual in PDF format • full description of each mode • screen pictures • operational hints • index of controls • technical appendices

  15. VK7MO EME DXpedition • Destinations: Cocos-Keeling Island (VK9C) and Christmas Island (VK9X) • Bands: 144, 432 MHz • Antennas: single yagi on each band • Power: 300 W on 2m, 65 W on 70 cm • Mode: JT65B

  16. VK7MO DXpedition Scorecard • EME QSOs on 2m: 156 • EME QSOs on 70 cm: 6+ • Nearly all QSOs random: no internet

  17. … to the demos …

  18. WSJT in FSK441 mode

  19. Does it work? -- 231 grids on 2m

  20. ZS5LEE works K1JT on 2m

  21. ZS5LEE works K1JT on 2m

  22. K1JT works RN6BN on 2m

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