Re: [amsat-bb] AO-7 behavior

[Emily Clarke <w0eec@xxxxxxxxx>]

Hello Freeman,

I've been collecting data about AO-7's behaviour for about 18 months now, 
and it's difficult to say exactly what is happening. I can only speculate 
that what you describe lies deep in the logic programming (remember, 
discrete programming, there is no "CPU").  My minimal (and I stress 
minimal) research has led me to speculate that OSCAR 7 follows a logic 
stream like this:

1) Open the repeater in Mode B (it's most powerful but most draining mode) 
and activate the beacon.
2) Wait for control operator codes to be sent.
3) Monitor the bus power
4) If the power drops below a certain level, switch to Mode C (second most 
powerful and less draining mode)
5) If the power drops again, switch to Mode A (third most powerful mode and 
more less draining mode)
6) If the power drops again, switch to D (off)

I talked at length with Dick Daniels about this, and he thinks the 
person(s) who did this logic programming are no longer available, but that 
the archives (uncatalogued - in a closet at AMSAT offices) that Jan King 
had before he moved to Australia may hold some clues.  However Dick 
indicated this scenario might ring a bell.

It's impossible to tell what is happening what is happening with AO-7 since 
we can't have a lot of confidence in the TLM.  So I can only speculate that 
as more people use AO-7, the likelihood of AO-7 dropping to C or A is more 
likely.  I may take some blame for this as I believe my own enchantment 
with AO-7 has made it's use more popular.  With an increase of users both 
using AO-7 and the 432MHz weak signal band, and additional wideband space 
based radar contribute to an increase to the power density into AO-7's 
passband . If you also consider FM pirate stations, you can see how this 
may have increased the power density in the uplink band.

In the past I thought this was seasonal, and I think that AO-7 is more 
resilient during the equinox.  However since AO-7 is sans batteries and 
fickle, we can only speculate what is happening.

73,

Emily



At 08:07 PM 11/1/2004 -0700, you wrote:
>Has anyone noticed AO-7 suddenly dropping power in the evening passes
>over North America?  I have seen this several times lately with AO-7 as
>it passes over the extreme northern border of Canada.  The power, all of
>a sudden, drops several DB.  Any QSO I was in the middle of ends due to
>lack of signal.  I can no longer hear my own downlink, although I can
>sometimes hear the other station very  faintly.
>
>Have others seen this, or should I look at my gear closer?  This only
>happens with AO-7.
>
>
>-Freeman, N5FPP
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---------------------------------
W0EEC - CM87tm
AMSAT Area Coordinator - San Francisco Bay Area
http://www.projectoscar.net    http://www.PlanetEmily.com 
http://www.emilyshouse.com/experthams/ao7/

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