Great Reply Tim,
I try to tell the ops on AO7 to watch there input power. This old lady just can't handle us old men pumping the high power into her.
By the way, I had some very distorted signal the other morning and was so afraid she was damaged.
Best 73's AO7 ops,
See ya on the bird!
Dave, kn4ok
Mike, Piraja and all, Please take a moment to visit the page on the AO-7 Web site that includes an ssay from AO-7 Project Manager Jan King, W3GEY. You will find that essay here: ttp://www.planetemily.com/ao7/history.php?PHPSESSID=5cc1e3be993405e687967faffcac4407 According to Jan, AO-7 no longer uses batteries in its current condition. It is owered completely by the solar array. He explains fully what he believes to ave happened. Here are some excepts for the full essay Jan wrote, which appears n the page I provided the link to (NOTE - scroll down toward the borrom of the age to find Jan's report): "I am certain what has happened (and I know why): The battery did fail short. irtually all of the cells failed in a shorted mode eventually. This shorted ondition placed a shunt across the solar arrays and prevented current from oing to the satellite loads (i.e. the transponders, in particular). Some time efore G3IOR reported hearing the spacecraft again the short on one of the cells 1 out of 10) failed a second time. This time, it went from short to "open." hen it went open this released the shunt that was pulling the array voltage own and allowed the current to pass to the satellite loads. Since there is no attery at all now (because one cell went open), when AO-7 goes into eclipse ith each orbit, the satellite has no power to operate and shuts down in the ark."
lso:
People should realize that the solar arrays are old and they don't put out more han a few watts now. That's the only power available to run the ransponders.So, if they uplink too much power it will just cause the ransmitter to sort of 'cave in.' The voltage on the satellite bus begins to sag adly when a heavy demand is placed on the transponder (by a large uplinking ignal) since there is nothing there to regulate it and then the oscillators in he receiver and transmitter chain start changing frequency. People call this FMing' and that is what is going on."
an's entire essay is fascinating. The primary reason I consider AO-7 the flagship of the amateur satellite fleet s her amazing story and legacy. I consider myself blessed and fortunate to have n opportunity to work the "Grand Old Girl" now, more than 25 years after she eached orbit. Even on her bad days - and today appears to be one, as I write his - I am able to clearly copy my CW signal on the downlink from about 20 egrees elevation running only 5 watts out of a Yaesu FT-817 from my handheld lk dual-band yagi - and working from inside my home on the second floor, my plink signal shooting through the second-floor ceiling and roof. I believe she poils us on her good days with the ability to enable contacts that span oceans nd continents - even with a station like mine.
am grateful for every orbit during which I am able to hear such an amazing iece of amateur-radio hardware still working as hard as she can.
3 to all,
im - N3TL
_______________________________ rom: Mike Rupprecht mail@mike-rupprecht.de o: ps8rf Piraja ps8rf@hotmail.com; amsat-bb@amsat.org ent: Wed, April 14, 2010 12:25:03 PM ubject: [amsat-bb] Re: AO-7 is not OK Hi Piraja, Yes, I made similar observations. If the CW is active on 70cm you can hear ometimes a very strong deviation in frequency. he CW beacon partly not decodable. I agree with you it could be an effect y low batteries or due heavy usage. ee some graphs here: http://www.dk3wn.info/p/?cat=21 73, Mike K3WN
----Ursprüngliche Nachricht----- on: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] Im uftrag von ps8rf Piraja esendet: Mittwoch, 14. April 2010 13:22 n: amsat-bb@amsat.org etreff: [amsat-bb] AO-7 is not OK
ome days we are seeing very strange behavior in the AO-7. In some orbits an only hear the feedback on the downlink when the satellite is approaching y station at about 30 degrees elevation, before is impossible to hear any ignal via AO-7. Using two pre-amplifier, one in the TS 2000x and the other ith 0.6 noise with 20 dB gain. During the orbits we transmiting power with f 30 watts. The satellite does not respond. Tried with 15 watts It was hen that we hear at certain points on the downlink audio too low. Its best erformance is when the satellite is almost 90 degrees from my station. et it seems that the satellite is asking for help. This seems the batteries are not getting enough loads. Or maybe it's xcessive use of power by the users of the satellite. Maybe it's time for the users of AO-7 rethink the best ways to keep QSO hrough it, such as the use of LOW POWER so that over time the satellite is tabilized. "Long live the AO-7" 73' Piraja, PS8RF The Amateur Radio is supportive and helpful in any circumstance.
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______________________________________________ ent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. ot an AMSAT-NA member? Join now to support the amateur satellite program! ubscription settings: http://amsat.org/mailman/listinfo/amsat-bb ______________________________________________ ent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. ot an AMSAT-NA member? Join now to support the amateur satellite program! ubscription settings: http://amsat.org/mailman/listinfo/amsat-bb