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Re: RS-13 Mode KA Primer

K5OE@aol.com wrote:

> K5OE wrote:
> > >  The convention is to fix your transmitting freq. and adjust the 10 m
> downlink
> >  > for Doppler shift.
> KD9KC wrote:
> >  I disagree.  Unless I read it backward, you tune the higher freq.  What you
> >  express above is OK for mode K, but backward for mode A... unless something
> > has changed ?!?!
> Mike brings up an interesting quandary.  I know the convention is to fix the
> lower freq and tune the higher to compensate for Doppler shift.  What is the
> preferred practice when one station is on mode K and the other is on mode A?
> It makes sense to me to do as Mike suggests, tune the 2 m transmit on mode
> A--especially since the mode K shift is never more than about 2 kHz for an
> entire pass.  I would suspect, though, it makes sense for the mode A station
> to "track" the mode K station's 10 m downlink and tune to it and not to his
> own fixed 10 m downlink.  I realize that's double work for the mode A station,
> but that way both stations move in concert.
> Other opinions/comments or old-timers' experience?

Well, dopplar shift is a function of frequency, and the greater the frequency, the
greater the dopplar shift.  Inversly, the lower the freq, the lesser the shift.
It then becomes appearant that it would be _IN_THEORY_ easier for the mode K
station to follow the dopplar shift on 10m, and also make the minor ajustments on
15m, since this is the freq with the least shift.  In practice, many mode K
stations cannot monitor the downlink while sending, because they are using a
transceiver instead of seperate units.  I resemble this remark (sigh).  Bottem
line is, do what you need to do to complete the contact, and try to be tolerant of
stations crowding you due to dopplar drift.  Happy Mode A new year, only 25 more
states to go, only 44 more grids to go, and only 363 more days to go.

Vy73, Mike. KD9KC  Army MARS: AAV6EV
kd9kc@whc.net - - - kd9kc@amsat.org
Home Page: http://www.qsl.net/kd9kc/
The farthest West ham in West Texas.

El Paso, where the sun spends the winter.

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