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Re: LF: SlowJT9 v0.9.02

To: [email protected]
Subject: Re: LF: SlowJT9 v0.9.02
From: Eric NO3M <[email protected]>
Date: Mon, 12 Nov 2018 15:42:05 -0500
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Correct, the original timings were fit into a "window" vs. simple scaling.  Since the slowJT exe wouldn't run in WINE, I just ran a few commands to decode K5DNL:
arecord -c 1 -r 12000 -f S16_LE capture.wav
sox capture.wav capture_tmp.wav speed 2.0
jt9 -9 -d 3 -S 300 capture_tmp.wav
cat decoded.txt

0000   1  -26   0.1   2400.   1   VVV DE K5DNL           JT9

jt9 is the standard executable decoder from WSJTX v1.9.1.

73 Eric NO3M

On 11/12/18 3:12 PM, N1BUG wrote:
Eric brings up a good point. Forget what I said the other day about
beaconing with a U3S to be received by SlowJT9. I believe that won't
work because the U3S uses the original JT9-2, -5, -10, -30 symbol
lengths which are different.

Probably (a guess) in the original, symbol lengths were chosen to
fill as much of the period as possible while leaving enough time at
the end for decoding. I would further guess there were specific
decoders for each submode, or one decoder whose parameters could be
modified for the current submode.

Paul N1BUG

On 11/12/18 2:47 PM, Rik Strobbe wrote:
Hello Eric,

yes, a scale factor of 2 and 5 is used.

I hadn't any information about the old JT9-2 and JT9-5 modes and
those scale factors seemed the most straightforward to me and
make the conversion to JT9 easy.

73, Rik  ON7YD - OR7T

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