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