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Re: Geosynchronous Satellites



On Sun, Dec 24, 2000 at 07:57:47AM -0600, Jon Ogden wrote:
> If STANDARD FM voice is so much better than SSB, why don't EME operators use
> it?  Why is it not used then on VHF weak signal work?  Why don't Aurora
> scatter operators use it?  Or meteor scatter ops?  You have failed to answer

Phil answered this in the original post:

> So where did the truism come from, that FM is bad on amateur           
> satellites? Simple, actually. It comes from the assumption that hams         
> will tolerate poor audio SNRs. If you're willing to tolerate a average
> SNR of, say 10 dB in a 3 KHz bandwidth, then the average RF power is
> indeed less than the 10 dB or so C/N needed to quiet a 15 KHz NBFM  
> detector. But as soon as you up the required audio SNR, even by a few 
> dB, FM once again starts to look better. And digital voice (with good
> compression, FEC and modulation) is better still. That's why the   
> cellular networks started with FM and are rapidly going digital.

(In my own words) SSB is 'better' if you'll tolerate a low
signal to noise ratio; as soon as you want a better ratio,
there is less advantage and eventually it is worse than FM.



Regards
Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
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