Hi Rik,
We are well aware that propagation-induced signal distortions at LF and
MF are very different (and generally much smaller) than at HF. The
extremely narrow bandwidths used by discontinued sub-modes JT9-2, JT9-5,
JT9-10, and JT9-30 took advantage of these differences and provided
sensitivities not otherwise achievable. However, the data rate of these
sub-modes was proportionally smaller, as well. A minimal standard QSO
takes 12 minutes in JT2 and 3 hours in JT9-30. As a result none of
these submodes ever gained any significant use.
We now consider JT9 to be essentially a "legacy mode", and we have no
plans to bring back JT9-2, etc. In the meantime we have developed
better ways of achieving lower S/N decoding thresholds, with new coding
and modulation schemes. At present these ideas and tentative plans are
on the "back burner", but we may return to them in due course.
Of course, all of our past code can be recovered from the open-source
archive. With dedication, someone with enough time and interest could
resurrect what's needed to make a working platform for JT9-2, JT9-5,
etc. I do not recommend this approach, because better schemes are possible.
-- 73, Joe, K1JT
On 9/6/2018 2:59 AM, Rik Strobbe wrote:
Hello,
I hope I am at the right place with my question (if not so, please let
me know where I need to be).
I am using JT9 on the 630 meter band (472-479kHz), it is an excellent
mode to work distant stations. But even with JT9 is is very difficult to
cover distances of over 5000km.
At these wavelength it is a hard job to get some signal radiated
(antennas are very small compared to then wavelength), so most stations
have an ERP of less than 1W.
In addition, depending on the countries, there is a ERP limitation
between 1 and 5 W EIRP. So increasing the radiated signal is often not
an option.
In an early version of WSJT-X several "flavours" of JT9 were available:
JT9-1 (1 min sequence), JT9-2 (2 minutes sequence) and JT9-5 (5 minutes
sequence).
JT9-2 would give an extra 3dB (more or less), very often the difference
between success and failure on 630m DX.
I believe JT9-2 and JT9-5 were abandoned because there were issues with
the doppler shift and multi-path propagation on HF, but this is less
critical on lower frequencies and on 630m at least JT9-2 was very useful.
Question 1: Is the early version of WSJT-X (that supports JT9-2 and
JT9-5) still available somewhere?
Question 2: Would it be feasible to implement JT9-2 and eventually JT9-5
in a new version of WSJT-X? This would also take advantage of
the decoding improvements made the last years.
73,
Rik, ON7YD - OR7T
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