[amsat-bb] RUDAK psudo ZRO

[Jim White <jim@xxxxxxxxxxxxxxxxxxxxx>]

Aug 10, 2002

Testing of three different DSP modulators continued today during the RUDAK 
window over the US.  Two worked, one didn't. We ran out of window before we 
got to the planned 153k6 testing.

There was an AFSK signal on briefly that produced an FM carrier with a 1 
KHz tone modulating it.

We left a sort of pusdo ZRO test running.  It puts out a carrier at 
2401.864 that starts out at full power and reduces power by 3dB every 10 
seconds.  It goes down to 45 dB below the full power level.  Here at WD0E I 
can't detect the -42 and -45 signals with just a rx in SSB.  Pretty darn 
weak.  Good test of your receive capability.
Note that some IMD products are present when this signal is at higher power 
levels.  Specifically, when just the 9k6 FM downlink is on there are IMD 
products above and below it about 53 Khz.    When the 'ZRO' carrier is also 
on additional IMD products are generated.  One is about 30 KHz below the FM 
signal, another is about 50 Khz above the FM signal.  Don't be confused by 
those.  The 'ZRO' signal is a pure carrier, no modulation.  We would like 
to hear how well the 'ZRO' signal can be heard a low levels.  Reports to 
wd0e@amsat.org please.  The 'ZRO' code will be allowed to run as much as 
possible but may not be on if that hardware is needed for other testing.

The purpose of this code is to further our understanding of how to program 
the DSP hardware.  The objective remains to produce easily usable links to 
RUDAK.

Jim
jim@coloradosatellite.com
wd0e@amsat.org

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