[amsat-bb] AFSS Radar Beam sidelobes
bruninga at usna.edu
Wed Dec 12 10:06:47 PST 2007
> The ISS flies through the 216.98 MHz AFSSS Radar
> Fence across the southern USA 6 times a day and
> it has an ERP of over 6,000 megawatts. It is only
> for about a second at the peak but even the
> sidelobes are much higher than anything
> a ham station could possibly come up with...
Bit of history on the sidelobes: On the AMSAT-BB you might
remember our PANIC about 6 months ago trying to find a good
OSCAR class station in the Southern states during the final days
of the RAFT satellite (Radar Fence Transponder) to command the
radar receiver ON at exactly the time of passage through the
We could not do it here from Maryland because the satellite was
too low when it passed through that one second beam. But
darned-it-all. When we finally did get a student at UC Irvine
(KF6RDB) to turn it on, of course we found out all about those
sidelobes! He heard the transmitter through most of the pass,
not just the one second when it went through the beam...
If we had thought about that, we could have been doing all kinds
of neat testing from here throughout the mission... Oh well.
Live and learn. The sidelobes would have to have been
attenuated by milliions to not be heard.
Even 50 dB down, is still very strong on VHF... Conidering the
100 meggawatts of transmitter.
The ANDE re-entry campaign is getting HOT. So lets capture that
telemetry and feed it to the APRS-IS...
More information about the AMSAT-BB