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WSJT Meteors, Moonbounce, and More …

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Presentation on theme: "WSJT Meteors, Moonbounce, and More …"— Presentation transcript:

1 WSJT Meteors, Moonbounce, and More …
FSK441 Joe Taylor, K1JT Mid-Atlantic States VHF Conference September 24, 2005

2 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 – 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 JO 2. G3LTE DL9KR JO 3. G3LTF DL9KR JO First 21 (of 63) encoded channel symbols, including FEC:

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 ─ Grids WAS 42

11 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:
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


16 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






22 VK7MO DXpedition Scorecard
EME QSOs on 2m: EME QSOs on 70 cm: 6+ Nearly all QSOs random: no internet








30 … to the demos …


32 WSJT in FSK441 mode

33 Does it work? -- 231 grids on 2m

34 ZS5LEE works K1JT on 2m

35 ZS5LEE works K1JT on 2m

36 K1JT works RN6BN on 2m

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