[amsat-bb] input power question

Mark D. Johns mjohns+K0JM at luther.edu
Sun Jun 16 13:46:55 UTC 2019

This is a very common issue for newcomers to the linear satellites.
Almost every pass, there is someone calling CQ over and over again
with a loud signal, but completely oblivious to the several stations
trying to answer them.

Downlinks on the linear satellites, especially on UHF, are MUCH weaker
than on the FM satellites. Remember that the transmit power of the
satellite is being distributed across an entire passband that many
stations are sharing -- unlike FM, where all the power is just on one
frequency for one station at a time (ideally).

You are going to need the best, low-loss feedline you can afford for
UHF, and that feedline needs to be as short as possible. If your
feedline is more than about 50 feet (or about 15 meters) you are going
to want to have a pre-amplifier very near the antenna. A good pre-amp,
with RF switching so that you don't accidentally blow it up by
transmitting through it, can be had for less than $150 from several
manufacturers. Or, there are designs around to roll your own, if you
are good at that sort of thing.

Good luck, and hope to work you on the linear sats very soon!
Mark D. Johns
KØJM / MØGZO / ex-9H3DJ / ex-KØMDJ
Brooklyn Park, MN USA   EN35hd
"Heaven goes by favor; if it went by merit,
   you would stay out and your dog would go in."
    ---Mark Twain

On Sun, Jun 16, 2019 at 7:26 AM WB8PFZ via AMSAT-BB <amsat-bb at amsat.org> wrote:
> I have completed my sat station but am having trouble hearing myself. I have checked cables and antenna ( M2) sat antenna. All seems well with low SWR. I can hear on the 2 meter downlink. How much power is needed on the UHF uplink? Hope to figure this out shortly. This is being done on the SSB sats. Thanks Mike WB8PFZ
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