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Re: PSK-31 Satellite Donwlink Opportunity?



On Sun, 25 Feb 2001, Jon Ogden wrote:

> How are you going to avoid the transmitter from de-sensing the receiver if
> it is in-band?  You'd need some mighty good filtering even with a 1.4 MHz
> split.  Wouldn't you totally lose any RX sensitivity?

Exactly.  That is the challenge.  But here are some thoughts..

1) The RX sensitivity does not have to be that great, since people on the
ground can run 25 watts (Radio shack 10m rig) and the satelite is only
running say 100 milliwatts (or whatever we finally calculate).  Thus the
RX can be 20 dB or so less sensitive than a "normal" 10m receiver and
still get the same performance as the Uplink as on the Downlink...

2) If isolation can still not be achieved in the 4" Cubesat, then we just
buy two of them with a tether between them.  THey can separate several
yards with the XMTR in one and the RX in the other...

Anyway, that is the design challenge.  FInid out what it takes and then
see if it can be built....

de WB4APR, Bob


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