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re: FM Sat Channel Spaceing 15 vrs 25k



I agree wholeheartedly with your 2 meter analysis.  It is clear that few
people attempt to compensate for doppler in the 2m satellite sub-band.
At 70cm, one HAS to compensate for doppler using anything except *maybe*
wide-band FM (e.g. 38kb packet).  Those who 'tune by ear' (most portable
J-FM operators) might also have to find the right channel by ear if they
are not sure where the satellite is in its orbit.  But they're already
used to doing that.  We need not worry much about those under computer
control.  Thus, i believe the roughly the analysis regarding downlink
channel spacing at 2 meters would also apply at 70cm (and above), since 
we only really need to worry about the granularity of the receiver VFO.  
Thus, it is my feeling that 25 KHz spacing should work fine for downlinks 
at 70cm (and thus 50 KHz would be excessively pessimistic).  

I'm not at all sure about uplinks, and perhaps at 70 cm, 50 KHz spacing 
might make sense.  Aside from a few QSOs on the MIR repeater, i've never
tried a 70cm FM uplink and i'm not at all sure how this works without
computer control.  Perhaps it's not such a good idea for birds intended 
for use by folks just getting started.

		         -- KD6PAG  (Networking Old-Timer, Satellite QRPer)


[Note: I never send unsolicited binary attachments and if you receive anything
purportedly from <kd6pag@qsl.net> that isn't signed with my callsign, then it
probably isn't from me.]
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