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RE: Something to try to improve AO-40 telemetry reception




Alan is completely correct and recalls for me a feature that
I THOUGHT was documented in the manual.  You can set the agc
speed  on both channels in the DSP2232.  Port 0 is the first
number.  In fixed gain tracking loops it is important to have
some agc present to present the loop with normalized error
signals in the expected tracking range. I will see if I can dig
up my documentation on this.

Bob





-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Alan P. Biddle
Sent: Sunday, December 16, 2001 3:07 PM
To: AMSAT-BB; DSP-2232
Subject: [amsat-bb] Something to try to improve AO-40 telemetry
reception


Hi,

I have been using AO40RVC, and my DSP-2232  using N4HY's enhanced modem
combined with P3T, running in parallel to capture AO-40 telemetry.  Averaged
over several passes, including very poor squint angles, the DSP-2232
outpoints AO40RCV by a small but consistent amount.  Perhaps 1 to 2 percent
better capture.  Of course that number might, and probably wood, change for
your particular receiving system.

However, the results were reversed until I tried a small tweak.  There is an
undocumented AGC command, AGC N/M, which applies to a whatever mode you are
using.  When you change modes, it resets to the default, AGC 2/2.  For the
400 baud TLM switching to AGC 3/3 seems to improve, slightly, the capture
efficiency.  By contrast, using 0 or 1 kills it completely.

I would be interested in anybody else's results.  You might try this with
other modes as well.  So far, no information from Timewave on what this
command is actually doing.


Alan
WA4SCA


-----------------------------------

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helps to know what part of it feels
pain. Be very, very sure, though, that
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