[amsat-bb] Doppler shift question
zmetzing at pobox.com
Thu Jun 6 15:53:52 UTC 2019
On 2019-06-06 09:37, Noel Petit via AMSAT-BB wrote:
> the other reason to stick with AM is that you can hear if other stations
> are trying to break in. FM has capture and blocks all but the strongest
> station. AM can superimpose multiple signals and hear if emergency calls
> may be made. Additionally, in the '30's FM was nearly impossible to
> generate reliably. AM doesn't depend on the transmitter's stability (to
> an extent).
On linear transponder satellites
(https://www.amsat.org/two-way-satellites/), you _can_ hear other
AM is wasteful of power, as others have commented, and has no place on a
power-limited satellite. The carrier, containing no information,
consumes 2/3rds of the transmitted power. The rest of the power is split
between two sidebands carrying the exact same information.
I disagree strongly with your assertion that FM was "nearly impossible"
to generate. (https://en.wikipedia.org/wiki/Armstrong_phase_modulator)
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