Andrew O'Brien wrote:
I'm getting many public and private emails from around the world about
JT65A. Some seem to think I'm involved with the software and how it
was to be used for HF. I'm no expert and have only about 40% of the
software mastered at the moment. I have no more clue about HF
applications than anyone else, other than I may have been somewhat
responsible for getting the mode used more on HF.
Keeping in mind that I am a total rookie, I thought I would attempt
to explain the very basics for HF use and respond to some of the many
emails I received today.
JT65A is a mode within the WSJT software and , as Chris explained
earlier today, is an MFSK type of signal. The software was designed
for the very critical aspects of EME and meteor scatter applications.
An essential element of EME and Meteor work is weak signal detection
and careful timing of who is transmitting and who is receiving.
Another aspect is that a series of brief messages are transmitted in a
designated order, these essentially meet the accepted requirements for
a valid contact. These is usually the exchange of call sign, grid
square, and some confirmation of received signals. This would be the
equivalent of perhaps a PSK31 contact where the accepted protocol was
agreed that a valid QSO needed to include : Call sign, QTH, RST, and
acknowledgement that the other station received the sent information.
Somebody suddenly started using JT65A on HF about 2 weeks ago, and us
JT65A ignorant hams simply detected a unknown mode on 20M. My only
involvement was to obtain the software when someone suggested it might
be JT65A and I confirmed the mystery signals were indeed JT65A. After
I mentioned it here and had a QSO, a dozen or so hams jumped on
the mode , spread the word to others, and the HF applications appear
to have excited many hams. I have been amazed by the emails received
today from different parts of the world all indicated their first HF
JT65A QSO or reception.
Early today, someone asked me just what can be done with this mode, is
it a legitimate communication application. Again, I'm no expert, but
I'll answer that with a big Y E S .You can do whatever you like with
it , you could in fact have keyboard chats if you wanted to. The
standard messages can be changed and you could type in how's the
weather at your QTH, if you wanted to. It was not designed for this
, but you can do it. Remember, it was not designed for HF work at
all, so already someone has broken the mold . You can do likewise and
use it in anyway you see fit (within your Government's regulations).
It is no different than Olivia, Hell, ALE, or MT63, in that it just
another mode. The user decides how it is best used. The one major
difference is that the software's default setting is that your typical
transmission lasts about 48 seconds and then you pause for 72 seconds
(12 seconds to the top of the minute and then 60 seconds allocated to
the responding station).
From a practical perspective, this mode appears to have uses that lean
toward the testing of propagation paths since the software always
gives you the SNR of a received station. The software records data
every minute, thus you can leave the software in monitor mode while
away from the shack and get a sense of the propagation upon your
return by looking at what was received, what the SNR was, and where
the stations received were located.
If you are a ham like me, you might like the challenge of making a
contact but not really get in to the whole conversation thing. JT65A
suits people like this by keeping to a minimum exchange and moving
on. However, I will reiterate, you can use the mode to rag chew...
but it would be slow . It could be more efficient than other faster
modes though, since the throughput under poor conditions may be more
reliable than most other modes.
So, play with it. Monitor . Invent new useful ways to use it. It
has been really great to see over 10 DXCC entities on HF JT65A in the
week since we have been pushing it. I wonder who will be the first
to get DXCC JT65A HF.?
As many may know, JT65 was originally written by K1JT(?).
A paper on JT65 can be seen at http://physics.princeton.edu/pulsar/JT65.pdf and
http://physics.princeton.edu/pulsar/K1JT/WSJT_User_600.pdf
As far as I can tell, there is a very large use of FEC which of course cuts
down
on the amount of user data throughput. Additionally, with 65 tones, I believe
that the signal is wider than 500 Hz. Hi Hi.
JT65A is generally used on 50 MHz. Thus JT65A on 6M is more like HF
propagation...ot at least that on 14MHz and above.
It would be wonderful if we could get K1JT to comment on the list for us.
For those who are interested in reasons for wider bandwidths on HF, here is
what
K1JT says, reg. URL http://physics.princeton.edu/pulsar/K1JT/UpdateHistory.txt
1. In earlier versions the vertically-scrolling JT65
