[amsat-bb] MORE POWER !!! EGON ...
archie.hackett at hotmail.com
Mon Aug 23 11:55:41 PDT 2010
To whom it may concern,
A lot of the experienced satellite operarors will recall Jan King
VK3GEY / W3GEY as the project manager for AO-7, consequently, here probably isn't a better
authority on the grand old Lady.
A few years ago GM1SXX and myself were in contact with Jan after I'd discovered and catalogued the operation of the mode timer - and noted the fact that it wasn't as described in the 1974 Amsat newsletter.
After it's resurrection and for several years thereafter I took an active interest in this veritable old girl
but eventually moved over to HO-68.
Due to moving into an old people's facility where aerials are not allowed I had no choice other than to
'bin' the satellite array and disguise a chopped down version as a TV (!) aerial on a small rotor.
Unfortunately, I was limited to 200mW so as not to interfere with the digital TV decoders installed in the rooms.
200mW was adequate on HO-68. however, due to the FM mentality promoted by Amsat, the uplink power
on the other satellites has been increasing ... particularly by the newcomers - who apparently, and mistakenly, think that high power is necessary. It's *NOT* ... nor is an EME class aerial array necessary to work LEO satellites. Ditto circular polarisation.
FACT: polarisation is *ONLY* circular along the boresight of an aerial.
High power is detremental to space bourne transponders - think power budget - causing among other
For the 'details', please read up on the subject. A positive mine of information can be found on the AO-7
Resource Page - (which I stopped administering several years ago) - or ask an experienced operator to explain why! high power is detremental - (power sharing on a linear transponder or 'hogging' it on FM).
As mentioned, Jan King is probably the foremost authority on AO-7. I'd like to quote a couple of his comments ...
* Jan King, W3GEY notes that AO-7 had (has?) a very sensitive receiver and a good uplink antenna.
5 watts EIRP should provide a good downlink. Amplifiers are not required for the uplink.
* Excessive uplink power may be cause FMing of the transponder and may be causing the input voltage to the regulator that provides 6D to fluctuate causing all telemetry to be bad.
Jan also explains - (on the AO-7 resource Page) - how to determine when the telemetry is valid -
(and when it''s not).
Serious operators take the trouble to read the recommended operating proceedures.
Finally, a reminder ... (repeated annually).
The Resource Page log was always meant as an ACTIVITY log - not! a competition. Mistakes that are
not rectified make the statistics, over time, invalid.
One can correct one's own mistakes by clicking on the spyglass to the left of the log entry ... and follow
the onscreen instructions.
The editing facility has*ALWAYS* been there - (but many people don't use it).
Please do *NOT* make several entries for the same pass unless you work more than eight (8) stations
on a particular pass.
73 John. <la2qaa at amsat.org>
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