[amsat-bb] AO-7 Recent Behavior

[Paul Stoetzer]

Worked PV8DX, K4FEG, and K4TB on the 21:28Z pass across the middle of the
United States.

Signals were nice and strong at the beginning of the pass, but seemed to
weaken in the middle of the pass. It stayed on the whole time, though.

73,

Paul, N8HM


On Mon, May 26, 2014 at 4:13 PM, Paul Stoetzer <n8hm at arrl.net> wrote:

> Bill,
>
> I did not observe the 17:48Z pass. DJ8MS reports that the satellite got
> much weaker at 17:58Z (http://aar29.free.fr/sat/ao7/ao7log.php).
>
> It apparently shut down at 19:45Z on the second pass. If it simply got
> much weaker as observed on the prior orbit, I could not hear it.
>
> Right before it shut down, I observed KB1RVT's signal start to FM while
> the transponder's noise floor was modulated by a strong CW signal in the
> passband. I replied to him and that was the last I heard of it.
>
> I'll be on next orbit around 21:28Z. Hopefully it stays on the whole pass.
>
> 73,
>
> Paul, N8HM
>
>
> On Mon, May 26, 2014 at 4:08 PM, Bill Bordy, NJ1H <nj1h at comcast.net>wrote:
>
>> Is it just me or did AO-07 shutdown today after working for a few minutes?
>>
>> The passes I observed this on were:
>>
>> 26 MAY 2014 17:48 - 18:04 UTC
>> 26 MAY 2014 19:37 - 19:57 UTC This pass in particular was a Max El of 59
>> for me.
>>
>> at my QTH in FN42.
>>
>> 73,
>> Bill
>> NJ1H
>>
>>
>>
>> On 5/25/2014 2:42 PM, PY5LF wrote:
>>
>>> Paul
>>> On this pass , finishing 18:43UTC ,  AO7 works all the time !
>>> 73
>>>
>>> PY5LF
>>> Luciano Fabricio
>>> Curitiba-PR-BR GG54jm
>>> http://www.qrz.com/db/PY5LF
>>>
>>> -----Mensagem original-----
>>> De: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] Em
>>> nome
>>> de Paul Stoetzer
>>> Enviada em: domingo, 25 de maio de 2014 12:49
>>> Para: amsat-bb at amsat.org
>>> Assunto: [amsat-bb] AO-7 Recent Behavior
>>>
>>> Good morning,
>>>
>>> AO-7 seems to be showing some odd behavior. For about three weeks of the
>>> eclipse cycle, it had been operating perfectly in Mode B with strong and
>>> clear signals on each and every pass. However, yesterday it was off
>>> during
>>> two ascending passes over the United States. It was back in Mode B
>>> during a
>>> pass over the Western United States around 23:30Z last night.
>>>
>>> PY5LF reported that it was in Mode B for 5-6 minutes after leaving
>>> eclipse
>>> and then it abruptly shut off. Reports from Europe on the AAR29 log also
>>> indicate it had shut off on ascending passes.
>>>
>>> My theory is that the sun angles on the solar panels are not ideal at
>>> this
>>> point. When it powers up after eclipse in Mode B, voltages fall such that
>>> the undervoltage detector kicks in and switches the satellite to Mode D
>>> (both transponders off). The satellite would then stay in Mode D until it
>>> loses power on the next eclipse and restarts in Mode B. If this is the
>>> case,
>>> my recommendation to Southern Hemisphere stations would be to wait a
>>> couple
>>> of minutes after it comes out of eclipse to start uplinking to the
>>> satellite
>>> and to keep power levels low until the panels are better illuminated.
>>>
>>> This behavior has not been reported on descending passes, though signals
>>> were reported to be weak and distorted at times this morning over the
>>> United
>>> States. Weak and distorted signals on the two meter downlink may be
>>> partially explained by Sporadic E as six meters has been open most of the
>>> morning.
>>>
>>> 73,
>>>
>>> Paul, N8HM
>>> _______________________________________________
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>>> _______________________________________________
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>>>
>>
>