[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Geosynchronous Satellites

on 12/24/00 1:18 AM, Phil Karn at karn@ka9q.net wrote:

> So it really seems to me that SSB's claimed power efficiency is
> largely illusory in practice. We might as well switch to nonlinear
> methods such as FM (or better yet, digital voice) that can give us the
> high audio SNRs we really want while using much less power than SSB.


If you think my recent posting was full of errors, that's fine.  I wasn't
trying to be as mathematically precise as you.  And while I am at it, let's
not begin the digital vs. analog debate again.  When I am talking about FM,
I mean STRICT FM as we know it that you get from your mobile or HT.  FM
voice, not some specially encoded digital signal.

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
that question as it shoots down your statements above.  No one modulation
form is best for all circumstances.  But ham radio IS a different beast than
commercial communications and yes, hams will tolerate a lower SNR.  In fact,
most of the time we have to.  That's part of the fun of it too.

Also, Phil, there are some very valid forms of digital modulation that do
use AM.  They work quite well, IN THE PROPER application.  FM is used in
subscriber units, etc. because of the efficiencies involved in the
modulation (and for some of the reasons you state in your post).  But the
same cannot be said for that base stations that use amplifiers with
efficiencies of 7% (and do NOT argue with me on that one as cellular
amplifiers is my background).

All in all, this discussion is meaningless because we are coming at it from
different sides.



Jon Ogden
NA9D (ex: KE9NA)



"A life lived in fear is a life half lived."

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org