[amsat-bb] FM birds

Diane Bruce db at db.net
Sun Jul 27 12:36:09 UTC 2014

On Sat, Jul 26, 2014 at 10:24:15PM -0700, Phil Karn wrote:
> On 07/22/2014 07:49 AM, wa4hfn at comcast.net wrote:
> > SSB/CW birds are the only way to go and if you build it they will
> > come  .
> Think about what it would be like to tune for Doppler while working SSB
> through a LEO satellite on microwave.
> Before you say "computer control", work out the effect of even a tiny
> error in your clock or orbital elements on a high elevation pass and
> remember that SSB has no carrier or pilot tone for closed-loop frequency
> tracking.
> Sure, you could have a second receiver track the satellite's beacon. But
> if you're going to all that trouble, why not just have it track a
> single high speed data stream from the satellite, one that's much less
> affected by Doppler in the first place?

Exactly. It makes much more sense to go digital.

The crucial thing is *not* the complexity of the groundstation
it is the lifetime of the satellite. 

- 73 Diane VA3DB
- db at FreeBSD.org db at db.net http://www.db.net/~db

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