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Re: Thoughts on future "FM birds" (was: proposal formaximizing fm le o contacts)



> At 01:19 PM 8/17/00 -0400, Bob Bruninga said:
> >... the doppler tuning of mode A [uplink] is 5 times greater than doing
> >the same on a 10m uplink.  Yes, the combined up/down total
> >is the same, but with 10m up, the smaller shift is on the uplink,
> >so everyone in the passband retains their relative position about 5 times
> >better and the whole group then moves greater relative to any particular
> >receiver.  Thus a 5 times reduction in the "sliding QSO" problem...

Mike Gilchrest responded:
> Since  convention has the operator tuning the higher frequency of the
> transponder pair, the operator would be tuning the 2 meter uplink on
> mode A, or in your example, the 2 meter downlink; same difference, no
> net "savings," or reduction in any sliding QSO problem.

We both agree that the net doppler change at any one station is the same,
but that was not my point.  My point was that on mode A, everyone slides 3
Khz relative to themselves on the UPLINK, thus the relative position of
QSO's in the passband are always sliding around relative to each other and
can overlap and collide in the passband.

But if we uplink on 10m where the Doppler is negligible, then the relative
positions of the QSO's relative to each other in the passband is 5 times
more consistent.  THus, QSO's can be packed more closely together in the
same available bandwith without crossing into each other.

Yes, now each listener still has as much doppler to tune as before, but it
is only for correcting his own downlink, so still the relative positions
of the stations in the passband remain the same and we can get almost
twice as many non-overlaping QSO's in the same bandwidth.

Bob

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