JT65 on 6 Meters SMOGfest 2006 Joe Taylor K1JT WSJT History 2001: FSK441 for meteor scatter 2002: JT44 for EME 2002: JT6M for MS, ionoscatter on 6 m 2003: JT65 for EME, with FEC 2004: JT65B, JT65C 2005: JT65 Deep Search decoder; Open Source code release 2006: Linux and FreeBSD versions; many algorithmic improvements;
programming team formed Design Goals for JT65 Work at lowest possible signal levels Conform to standard operating practices Exchange all info required for valid QSOs Good QSO rate for contests, DXpeditions Very high confidence in copied information Extremely low probability of false QSOs
JT65 Specs Sync tone at 1270.5 Hz, pseudorandom keying sequence Data tones up to 1448 Hz (A) Keying rate 2.7 baud Structured, compressed messages Reed-Solomon (63,12) code with six-bit symbols WSJT Statistics: September 2006
Total users: >3000 Nearly all amateur MS uses FSK441 JT6M popular on 6m JT65 EME users: 300 600 JT65 EME QSOs: >40,000 30% of entries in 2005 ARRL EME contest used JT65 (on 2m, >70%) JT65 EME, Band-by-Band 6 m: QSOs made almost daily
2 m: 1-yagi to 2-yagi QSOs common 70 cm: usage slowly increasing ? 23 cm: usage increasing With 2.33m TVRO dishes, 5 Watts is enough! JT65: Differences from CW
Structured messages Error-correcting code Synchronized transmissions Transmissions can be averaged Copy is all or nothing Roughly 10 dB advantage Percent of transmissions copied Measured JT65 Performance 100 Shorthand 80 Sync
28 BC + Grid/Rpt 24 28 Shorthand Sync limit: 30 dB DS (dB) Short65 (dB)
28* 32 *Callsign must be in list Some EME Politics On a web site: only two characters need to be decoded to print full EME messages Editorial in a respected VHF/UHF journal: the JT65 mode when using the Deep Search Decoder needs to recognize just only 2 letters but displays a full callsign. Another web site: All JT65 QSOs made using the DeepSearch Routine are not complying with long established EME QSO guidelines and are not eligible [for this Top List] due to partial copy. WRONG See paper How Many Bits Are Copied in a JT65
Transmission? published in DUBUS, 3/2006 Future WSJT plans? Enhanced meteor scatter mode ? Connection to Linrad / Winrad ? New soft-decision RS decoder EME Echo and Measure modes 30-bit JT65 messages Expanded waterfall: 0 5 kHz Expanded waterfall bandwidth WSJT 5.9.6
30-bit Messages 1. 2. 3. 4. 5. 6. Bits CQ de 3Y0X 30 de K2TXB 30 K2TXB 3Y0X OOO 72
3Y0X K2TXB RO 72 TXB de 0X RRR 30 73 de K2TXB 30 Notes: No grid locators Reports and Rs tagged with callsigns Numerical reports optional Messages 5 and 6 can be shorthands No need for a callsign list JT65+ JT65 Decoding Thresholds Message type KV KV Avg DS Short65
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