[RTTY] RTTY spectrum analysis article

[aflowers at frontiernet.net]

Coincidentally, the audio files in the article are
almost perfectly representative of an S2 signal and a S9+20 signal 400 Hz away
(which would be 62db with 6db per S unit). I'm measuring the gap between the
signals, not mark-to-mark, but that's probably irrelevant for the purpose of
discussion. There is a test case right there if anyone wants to see if AGC
matters to their software. The files are in "MMV" format so that
someone can just decode them in MMTTY with the playback function. You can try
various profiles and see if you get either or both of them to decode. If you
want to use other software (or a modem) you can just rename the extensions to
".wav" and play them from one computer to another (or into your
modem) just as if it were coming from your radio. That might be an interesting
experiment for the curious.  I didn't do any comprehensive testing of demodulators since that wasn't my aim.
Jim, I think the ST-8000 has a dynamic
range of around 80dB (I'm sure someone will correct me), so it should have the dynamic range with some room to
spare. You could play those files into the ST8000 and see what happens.  
Andy K0SM/2
 
 
 
----------------------------------------------------------------------

Message: 1
Date: Thu, 10 Jan 2013 09:11:58 -0600
From: "Jeff Blaine" <keepwalking188 at yahoo.com>
To: "Jim W7RY" <w7ry at centurytel.net>, "RTTY Mailing List"
    <rtty at contesting.com>
Subject: Re: [RTTY] RTTY spectrum analysis article
Message-ID: <E902D9367DEC44458622B80DDF97F52F at w520>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
    reply-type=response

That may be the case.

Then again, a s9+20 300 hz away from a s2 is going to have more in-band 
signal content on top of the s2 - at least enough to wipe that signal out. 
Now maybe that +20 is super clean and crisp but I don't find that to the 
normal case.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Jim W7RY
Sent: Thursday, January 10, 2013 9:03 AM
To: RTTY Mailing List
Subject: Re: [RTTY] RTTY spectrum analysis article

I disagree Jeff. If an S2 signal you are trying to receive is 300 or 400 Hz
away from a S9+20 signal, the radios AGC will not allow you to receive the
week signal. Filters in the radio are essential!

73
Jim W7RY