[RTTY] Signals that don't decode

[wa4jqs at mikrotec.com]

I saw the same thing during the contest was just hunting new band
contacts. someone said they must have been running 850 shift. but i found
them to be between 170 hz and 200 hz. went to the work shop and turned on
the receiver there and my scope. what i was was very over driven signals
with the osc freq drifting. i had a ts 570sg that would do this if i over
drove the audio input. when i turned on the alc and dropped the signal
input to a level where i had no ALC action the freq was stable. this may
have been what you were seeing. a lot of the signals i see on FT8 are very
over driven. seem like most ops figure they just leave the audio gain at
11 o'clock  like they do on ssb and it is ok. BUT it is NOT. just look at
the ALC action .

73 Tony WA4JQS
RTTY since 1963

SNIP


> In the ARRL RTTY roundup in January, this happened with a YV5. He came
> back to me as KM9G a couple of times, then said there was something
> wrong with my signal. Several years ago, I had the same problem with a
> D44 in the CQ WW RTTY contest. In both cases, I would come back to
> calling the station every so often, but never worked either one. There
> have been a few other instances of this, but these are the two which
> have stuck in my memory.
>
> This is very frustrating and I wish I could figure out the cause. There
> must be a subtle incompatibility of some sort. Any ideas? Thanks!
>
> 73,
>
> John, K9MM
>
> rtty-request at contesting.com wrote:
>
>> Date: Mon, 12 Feb 2018 16:20:04 -0000
>> From: "David G3YYD" <g3yyd2 at btinternet.com>
>> To: <rtty at contesting.com>
>> Subject: [RTTY] Signals that don't decode
>>
>> I found during the CWWPXRTTY contest at the weekend that there were
>> some signals with so much jitter on them that would not decode at all.
>> They all sounded very similar with similar shaped spectrums. I am
>> wondering if there is some software and in this case maybe it is radio
>> firmware rather than a general purpose computer software that is
>> generating this signal.
>>
>> I had one guy who kept calling me fortunately he was weak so I just
>> kept on running and copying others.
>>
>> Does anyone know what this might be? Better still if someone has a
>> sound file of the TX being received then I would love a copy of that
>> sound file to have a look at.
>>
>> Thank you for those who gave me a Q and hopefully a new prefix at the
>> same time.
>>
>> 73 David G3YYD aka M7T in contests
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