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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

WSJTMeteors, 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
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
wsjt what is it
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
requirements for optimizing minimal qsos
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
design of fsk441
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
design of jt6m
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
design of jt65
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
fec in jt65
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)
compressed and encoded jt65 messages
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 ...

does it work
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
measured sensitivity
Measured sensitivity

Measured sensitivity of JT65

what equipment do i need
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
installing wsjt
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
vk7mo eme dxpedition
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
vk7mo dxpedition scorecard
VK7MO DXpedition Scorecard
  • EME QSOs on 2m: 156
  • EME QSOs on 70 cm: 6+
  • Nearly all QSOs random: no internet
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