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Re: WAS Re: AO-16 report from Copenhagen



Mark, N8MH noted:
 
> The 437.024 transmitter antenna configuration on AO-16 is Left Hand Circular 
> polarity (LHCP).   The receiving antenna on the bird is a 1/4 wave vertical 
> whip.
>   
This whip operates against the body of the spacecraft as a "ground 
plane"; however the spacecraft body is a cube 22 cm on a side (you can 
see a picture at 
http://128.54.16.15/amsat-new/satellites/satInfo.php?satID=11&retURL=/satellites/status.php 
<http://128.54.16.15/amsat-new/satellites/satInfo.php?satID=11&retURL=/satellites/status.php>). 
This is about half of the quarter-wavelength you'd like to see for a 
proper ground reference, so the actual pattern undoubtedly has some 
weird nulls.
> The fading is quite dramatic, which means the bird is spinning/tumbling, or 
> some combination.  We could never hear this before on AO-16 when it was 
> transmitting its normal PSK signal, since we didn't hear the effect of fading 
> on the uplink in this mode.  Now we hear it, loud and clear!
>
> It does take an uplink signal that is pretty close to on frequency (145.820).  
> Adjusting for Doppler is helpful thing on the uplink.
>   
The receiver has a 15 kHz wide crystal filter with sharp skirts. So if 
your NBFM xmtr is set with a ±5 kHz deviation, you may well find your 
signal hitting the filter "walls". You may get better performance if you 
crank the deviation back a bit.

73, Tom

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