[amsat-bb] VO-52, Linear transponders and FM

Bruce Robertson broberts at mta.ca
Mon Apr 23 10:40:55 PDT 2007


The conference for VO-52's second anniversary has on its agenda a
discussion about design of a Hamsat2. This good news got me thinking about
the innovative aspects of Hamsat: principal among these is that it has
succeeded in using convention to determine the mode of operation. What I
means by this is that, as I understand it, in regions of the world where
SSB rigs might be in low supply, it is common practice, encouraged by the
satellite's operators, to use its linear transponders to relay an FM
signal. Here in N.A., and Europe, we use VO-52 nearly exclusively in CW/SSB. 

I can't speak for the rest of the world, but I'd say that in this neck of
the woods, this approach has worked very well. I've only once or twice
heard an FM signal on VO-52, no more often than other birds, and rare
enough that I can assume it was by accident or ignorance.

Given VO-52 success in this score, I wonder:
a) if the operators of other, future, LEO linear birds should likewise
permit their use in FM over appropriate regions of the globe. Since FM is
such a high duty cycle mode, I suspect usage and battery load statistics
from Hamsat might be helpful in guiding others' choices in this matter.

b) what advantage there is in launching a FM-only bird when a linear one
can be used in both modes. I assume there must be reasons of efficiency,
etc. since the designers of KiwiSat, for example, are making circuitry for
both modes.

73, Bruce

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