Tim,
Thanks for sharing. I am particularly interested in your statement that
"MMTTY works better on "slowish RTTY" senders", which lends credence to the
notion that the best way to improve RTTY reception is to improve RTTY
transmission. Do you have any insight into the source of those slowish
transmissions? A particular RTTY program or product? Or a particular
hardware device?
IF I remember correctly, Joe W4TV write a summary about serial port UARTs
several years ago, describing the compromises inherent in getting 45.45 baud
FSK from a serial port. Perhaps Joe can refresh my memory?
and, no - GRITTY would not decode BARTG75. I ended up with just 2tone and
MMTTY in that contest yesterday.
-larry (K8UT)
-----Original Message-----
From: Tim Shoppa
Sent: Monday, April 27, 2015 10:02 AM
To: rtty@contesting.com
Subject: [RTTY] More GRITTY observations
Used three decoders in SP DX contest this past weekend. One each of MMTTY,
2Tone, and GRITTY.
The fabulous 15M openings to JA and YB we've had the past couple weeks in
my mornings, were a real treat.
The signals that 2Tone worked well on, GRITTY worked well on too. Hard to
pick a clear winner, glad to have all three up and in play. I especially
paid attention on weak signals.
I usually completely disable squelch in other simpler decoders but have not
really arrived at the right squelch setting for GRITTY. Probably I
shouldn't mess with it. Clearly there is some interaction between bandwidth
and GRITTY decoding squelch that I haven't quite gotten the feel of.
The dynamic range of the GRITTY waterfall is superb. It is good for
"Seeing" weak signals in the noise.
GRITTY AFC is superb. I hate hate hate MMTTY AFC, if I leave it on all the
time it wanders off to infinity. 2Tone AFC works well on longer
transmissions but with short contest exchanges it often doesn't have time
to keep up. GRITTY AFC was just superb for the off-frequency callers.
Correct me if I'm wrong, but it looks like it could "back-decode" after
switching AFC frequency.
I have noticed there are some "slowish RTTY" senders out there with odd
longer no-deedle idles between characters. MMTTY decodes these well, but
2Tone and GRITTY struggled with these. It seems like 2Tone and GRITTY have
"flywheels" that don't necessarily wait for the start bit - this works well
for full-speed signals, but when the gap between stop and start bit is
stretched it doesn't work so well.
I did succesfully adjust MMTTY and 2Tone for the 75 baud BARTG. I don't
think GRITTY supports 75 baud, but I've never been good at reading
documentation :-).
Tim N3QE
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