[amsat-bb] AO-73 tonight at 02:58Z

Paul Stoetzer n8hm at arrl.net
Thu Aug 7 00:53:12 UTC 2014

Good evening,

I will be on AO-73 tonight at around 02:58Z, calling CQ at around
145.965 MHz. These passes usually don't have much, if any, activity
and I'd like to drum up a bit more.

The satellite will enter sunlight at 03:05:45, giving about 7 minutes
of transponder time here in Washington, DC. I will be operating off a
south facing balcony, so I will probably lose the satellite about 30
seconds before the transponder shuts off.

Tips for working AO-73:

-Do not use computer control, the transponder frequencies are not
stable and this will only result in frustration. Besides, manual
Doppler control is much more fun than letting the computer do all the

-I usually start a pass by trying to find myself come into the top
edge of the passband (145.970 MHz). To do this, I usually start
transmitting around 435.130 MHz and tuning up slowly until I can hear
myself enter the passband. Then I can move around the transponder
easily. Remember to tune your uplink to maintain an constant downlink
frequency (the opposite of FO-29).

-Keep power output down. The transponder has a very sensitive receiver
and a very active AGC circuit. Excessive uplink power will not make
your signal louder - it will only reduce that available for others on
the transponder. With a clear view of the horizon, 5 watts to an Arrow
or Elk is plenty for horizon to horizon coverage. Very slightly more
might be necessary if you are beaming through trees or other
obstructions, but try to keep power to 25-40 watts ERP.

Hope to hear you on this evening!


Paul Stoetzer, N8HM
Washington, DC

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