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Re: AO-7 report.- Band switching



James Duffey queried...

>"When AO-7 is powered all the time doesn't the on board
> housekeeping unit control the mode and switch between mode A and Mode B?"


"The following information is from AMSAT NEWSLETTER dated Sept 1974

The two repeaters are operated alternately by means of a timer arrangement,
but repeater selection and output power control can also be accomplished by
ground command."

And . "from Jan King, W3GEY, who provided the following information in an
email ...

It appears that the 24 hour clock that would cycle the transponders between
modes A and B is working but, it gets reset every time the satellite goes
into eclipse"

Which by my understanding, will produce a change of mode from A to B (or B
to A if you prefer) every 24 hours with no eclipse event. I believe there
have been cases where excessive power drain (usage) has resulted in a mode
change mid-timer, but I haven't been able to document that.

Roger
WA1KAT

----- Original Message ----- 
From: "James Duffey" <JamesDuffey@comcast.net>
To: <la2qaa@amsat.org>
Cc: <amsat-bb@amsat.org>; <Eu-amsat@yahoogroups.com>
Sent: Sunday, August 05, 2007 11:32 AM
Subject: [amsat-bb] Re: AO-7 report.


> John  - When AO-7 is powered all the time doesn't the on board
> housekeeping unit control the mode and switch between mode A and Mode B?
>
> Having a full time Mode B LEO linear transponder is great, in my
> opinion, having a Mode A LEO one will be even better. - Duffey
> On Jul 31, 2007, at 5:32 AM, John Hackett wrote:
>
> A study of the AO-7 eclipse charts for the last 3 years shows a
> progression
> toward non-elipse orbits in late 2007 - 2008.
>
> In effect, this means that AO-7 in all probability will not change mode
> unless anything untoward happens.
>
> It also means that we appear to have a permanent mode-B LEO linear
> transponder for the forseeable future ... providing operators follow the
> recommended operating proceedure.
>
> Please *do* decrease your power as the satellite approaches TCA to
> avaoid
> FM'ing.
>
> This not only helps the satellite, it helps the other operators in the
> passband.
>
> Don't be fooled by propagation anomolies. The mode-B transponder is
> working
> well and will continue to do so providing the alligators go and play
> somewhere else. Under normal circumstances you do NOT !! need a lot of
> power. Please use only the necessary to maintain adequate
> communications. If
> you can't copy people adequately, you should improve your receiving
> capabilities rather than increasing your uplink power ... remember,
> aluminium is cheap and it's a lot more user friendly to everyone
> concerned
> .... with perhaps the exception of your neighbours.
>
> For all intents and purposes, AO-7 is a QRP satellite. Please treat
> it as
> such.
>
> 73 John.   <la2qaa@amsat.org>
>
>
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> _______________________________________________
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