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RE: RE: 38k4 Operation with FT 847



I believe that the DSP2232 MIGHT have sufficient A/D bandwidth
but not the SCAF bandwidth to do the 38400 bps modem.  I will check.
If I can change the sample clock to 4x what it is now, and do a single
channel version or if I can modify the code to work at 2x, I will.
This will be the UO22 modem (with equalizer) modified to run 4
times as fast or a rework to run at 2x or 1x by reducing the number
of samples per baud.  I am not certain it will work. It has been
Sooooooo long since I looked at this stuff, I can no longer even
remember if it is possible to set the filter chips fast enough.
If not, then the only way will be to BYPASS the filter chips,
providing your own external filtering (which we should have
provided for in ancient days).  That said,  I already know that
we have sufficient A/D bandwidth.  That is because we are
oversampling for the 9600 bps modem by a factor of 4.  This can
be done with a 2x demodulator and a modification to the clock
recover and fractionally spaced equalizer.

I will NOT however, do the testing, modification of a rig, interface
to the rig from the DSP2232 etc. necessary to make this work.  I
will do it and throw it as hard and fast as I can over the transom
and walk away.  No updates will be issued.  I will do it or I will
not.  It will succeed or it will not.  I don't have time to spend
hours and hours on this.

Bob
N4HY

-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org]On
Behalf Of Howard Long
Sent: Tuesday, January 25, 2005 10:44 AM
To: Mark L. Hammond; AL7CR; amsat-bb@amsat.org
Subject: RE: RE: [amsat-bb] 38k4 Operation with FT 847


Hi Mark

> a DSP unit (such as the TAPR-interface/EVM56002)

Do you (or anyone!) know if there are 38k4 modems available for the DSP-12
or DSP-2232?

73 Howard G6LVB
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