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Re: [rsgb_lf_group] Re: LF: JT9-2 and JT9-5 mode application

To: "[email protected]" <[email protected]>, "[email protected]" <[email protected]>
Subject: Re: [rsgb_lf_group] Re: LF: JT9-2 and JT9-5 mode application
From: Rik Strobbe <[email protected]>
Date: Thu, 8 Nov 2018 22:12:22 +0000
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Thread-topic: [rsgb_lf_group] Re: LF: JT9-2 and JT9-5 mode application
Hi Paul,

Adding even slower modes in the application is not difficult.
But the slower we go the more stringent the frequency stability requirements 
are. For groundwave this is limited by the TX and RX stability, but for skywave 
propagation the mood changes of miss ionosphere could be nefast.
136 kHz might be better suited for JT-10 ot JT-30 than 472kHz.
Stefan might be interested in JT-86400 (one message a day) for ULF ;-)

About JT9 coding: for this I am using another exe file of the WSJT-X suite. It 
seems to work fine, both for free and structured messages.

73, Rik  ON7YD - OR7T

Van: [email protected] <[email protected]> namens 
N1BUG [email protected] [rsgb_lf_group] <[email protected]>
Verzonden: donderdag 8 november 2018 22:57
Aan: [email protected]; [email protected]
Onderwerp: [rsgb_lf_group] Re: LF: JT9-2 and JT9-5 mode application

Hello Rik,

I am very interested in this! Thank you very much for your work!
Tomorrow I will download the program.

I think we badly need these slow modes for the average LF operators
(which is most of us at least on this side of the pond).

If the beta tests are successful, would it be possible to add JT9-10
and perhaps even JT9-30? For trans-Atlantic QSOs I think these could
be very helpful.

How did you transmit JT9-2 signals for the QSOs? I can do that with
my U3S but it can only send free text messages limited to 13
characters. It cannot send the packed messages normally used for QSOs.

Paul N1BUG

On 11/8/18 4:29 PM, Rik Strobbe wrote:
> Dear all,
> a few months ago there was a short discussion about a "revival"
> of the slower JT9 modes such as JT9-2 and JT9-5.
> These modes existed in early versions of WSJT-X, and had the
> advantage of a better S/N treshold level, at the cost of longer
> transmissions. But unfortunately thse modes were abandoned in
> later WSJT-X version.
> As a result I raised this question in de WSJT-X developers group,
> but there was no intention do implement these modes again, as the
> focus was more on the (further) developing of new(er) modes.
> Having a closer look at the WSJT-X source code I noticed that the
> JT9 decoding was done in a separate executable and with some
> assistance of Joe, K1JT, I managed to write an application that
> used this executable for decoding.
> As this executable only decodes JT9 signals, not JT9-2 and JT9-5,
> I had to use a lttle trick: speeding up a JT9-2 recording by a
> factor 2 results in a JT9 signal (at the double frequency) that
> can be fed to the JT9 decoder. The same can be done for JT9-5
> (now speeding it up 5 times).
> Some tests showed that this way a JT9-2 signal could be copied at
> a 2.5dB better S/N treshold compared to JT9(-1). Not completely
> the theoretical 3dB, but 2.5dB can often be the difference
> between a failed or successful QSO. JT9-5 hasn't been tested
> yet.
> All this was done "manually" and it was rather time consuming.
> So I decided to write an application that I named SlowJT9. It
> takes care of all the conversions and frequency shifts.
> Besides JT9-2 and JT9-5 it also supports JT9(-1) for convenience
> reasons.
> Over the past weeks I tested the application in JT9 mode and
> after more than a dozen QSO's I feel that it now time to release
> a beta version.
> Whoever is interested can download the SlowJT9 installation file
> at
> For now only a Windows version of SlowJT9 is available. But as
> the used IDE has cross platform facilities it should be possible
> to support other operating systems as well in the future.
> The aim of this beta version is: - To test if the application is
> working properly. - To find out if JT9-2 and/or JT9-5 have a
> sufficient S/N advantage over JT9(-1). - To find out if there is
> sufficient interest in using these modes to continue the
> project. Therefore all comments, bug reports and suggestions are
> most welcome via the Blacksheep RSGB LF Reflector, Yahoo RSGB LF
> Group or directly at [email protected]
> 73, Rik  ON7YD - OR7T




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