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: [email protected] [mailto:[email protected]] Em nome de Paul Stoetzer Enviada em: domingo, 25 de maio de 2014 12:49 Para: [email protected] 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 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb