[amsat-bb] Re: Eagle U/V modes
howard at howardlong.com
Sun Oct 8 13:42:13 PDT 2006
> Regarding ETC., could beginners use FM in a specific
> portion of the passband near perigee?
Power and bandwidth issues aside, technically there is no reason why FM
would not work through the transponder, although the equalizing effects of
STELLA in the SDX may distort the signal somewhat because it's designed to
deal with SSB/CW signals.
Regarding perigee: firstly, of course at perigee the footprint is a lot
smaller, so coverage would be a lot smaller. Plus, the spacecraft will be
off-pointing at perigee.
> I realize it is not as power efficient as SSB and CW
It is also much less frequency efficient - currently, we are designing for a
100kHz passband. An FM signal might take 15kHz of that whereas an SSB signal
would only be 3kHz.
The inefficiency from the power aspect that you mention could be mitigated
by converting the FM uplink into an SSB downlink, although of course this
rather cancels your suggestion that FM might encourage more beginning users!
73, Howard W6/G6LVB
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