I've been watching with interest the use of the narrow versions of the
various data modes being used on the 500kHz band, and anyone who reads
RadCom will see the mention I made in the Data Column last month of
the parallel FSK and PSK31 trials..
Joe Taylor, K1JT has written a suite of programmes using
multi-frequency FSK coupled with heavy source coding and forward error
correction for extreme weak signal communications on VHF through to
Microwaves, especially targetted at Tropo, EME and Meteor scatter.
I mention it on this reflector as he has now introduced two new
embryonic modes (JT2 and JT4) that include narrow shift options (a few
tens of Hz overall) that may be well-suited to MF communications.
I suggest a visit to his web site to read up on the modes and
techniques he employs, and download the latest version of WSJT. The
main web page doesn't mention JT2 / JT4, but the beta version at 5.9.8
is detailed in the links shown here, and experimenters are invited to
download an try it out. There is quite a lot of description and
theory supplied, and makes for a fascinating read!
The heavy error correction and redundancy adds considerably to the
weak signal capability.
Main WSJT site http://physics.princeton.edu/pulsar/K1JT/
JT2/4 description http://physics.princeton.edu/pulsar/K1JT/JT2_JT4.TXT
Download latest WSJT software
http://physics.princeton.edu/pulsar/K1JT/WSJT598.EXE
I implemented direct DDS-generated JT65B on the GB3VHF 2m beacon a
couple of years ago, and the mode is now being used on the GB3RAL
40/50/60/70.05MHz beacon family. Details of GB3VHF can be found on my
web page shown below. Reception reports all agree on the mode's
extreme weak signal capability and a major improvenment over CW alone.
It will be interesting to see if the narrow band versions have
anything to offer the lower end of the spectrum.
Be aware though, the JT modes do rely on quite accurate timing, and PC
clocks need to be set to within a second or two of each other.
Andy G4JNT
www.scrbg.org/g4jnt
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