[amsat-bb] AO-7 Recent Behavior

[Paul Stoetzer]

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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>>
>