[amsat-bb] Re: Future radical satellite designs

Robert Bruninga bruninga at usna.edu
Mon Jul 9 08:48:21 PDT 2007


Regarding a 10m PSK-31 uplink:

> How long were the antennas?

On PCSAT2, the HF system shared the 19" 2m whip.  It was a sharp
tune, but we got it resonant with a simple LC diplexer..  But
then our box was a bigger counterpoise.  We were less successful
with our 5" cubesat and it's 4' whip.  Again, a deployment
anomoly cause that experiment to also fail.
 
> It's a bit difficult to do the springy ruler trick in a
cubesat when  
> they get above 70cm quarter wave unless its a tether :-)

But remember that the uplink stations are using say 25W on 10m.
And there is a 14 dB link advantage compared to VHF.  And then
there is the weak signal performance improvement of PSK-31.  So
we figured you could give up maybe 10 dB or so in the antenna
system, and still have a viable PSK-31 10m uplink.

Also, instead of trying to match the 19" whip to a 10m 50 ohm
receiver, if the front end of that receiver was tuned to be a
voltage probe, then better antenna efficiency would be possible
too?...

Bob, WB4aPR



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