| About JT6M |
|
JT6M is part of the WSJT suite of digital weak signal
software applications developed by Joe Taylor, K1JT
(WSJT - Weak Signal by Joe Taylor). JT6M is optimised for 6M meteor scatter but
is equally effective with Tropo, weak ES and scatter modes of propagation. |
Before we continue a few misconceptions need to be cleared
:
- JT6M is not really a "Digital" mode and is in fact FSK. The term "digi-mode" is applied to
JT6M and other modes such as RTTY, PSK, SSTV etc. simply because they are generated by a computer.
- WSJT is not a mode but the name given to suite of digi-modes i.e. JT6M, JT65, FSK441. (just as Microsoft Office is
the name given to a suite of programs i.e. Word, Access, Excel etc.)
- JT6M does not use the search algorithm that is used with JT65.
|
JT6M was first introduced in March 2003, as first beta version, in WSJT
Ver.3.5.1 followed with a better and faster version in Ver.3.6.0. Versions since then have seen further improvements.
The latest full version (pre-WSJT6) available is Ver.4.9.7.. This includes changes relating to JT65 mode; JT6M
mode remains the same. The latest version is now available, V.5.9.7.
You can download WSJT software (freeware) from K1JT's web site .
Don't forget to
read Joe's Update History text file,
click here . |
| You don't need to run high power/large antenna arrays to make QSO's
with JT6M. Many successful QSO's using less than 50W and 3 el yagi have been made. Please give it a try, you'll be amazed ! |
| JT6M uses 44-tone FSK with a "sync tone"
and 43 possible data tones, one for each character in the
supported alphanumeric set. The sync tone is at 1076.66 Hz, and the 43 other possible tones are spaced at 21.53
HZ intervals up to 2002.59 Hz. The tones are keyed at a rate of 21.53 baud, so each one lasts for 1/21.53 = 0.04644 seconds.
The sync tone is ON during every 3rd transmission interval; tones representing two data characters follow each sync tone.
The transmission rate of user data is therefore (2/3)*21.53 = 14.4 characters per second. The transmitted signal sounds
a bit like piccolo music. |
| The program attempts to decode both single pings and an "average message". The
average is the last line displayed during each decoding attempt, and is flagged with an asterisk. The number to the right
of the asterisk is the inferred message length (for example, the number should be 22 for the message -
"G0CHE IK0FTA R38 R38 " - note double space between R38 and G0CHE). If the program finds the wrong length, the average will be garbled or meaningless.
All message lengths should be even numbers, because odd-length messages are padded with an extra space at transmission time in order to make them even. With JT6M
mode it is not uncommon to see incorrect characters near both ends of decoded sequences, where the signal is weak. |
| Joe claims "JT6M can work with signals that are up to 13 dB weaker than those
required for FSK441." |
