[amsat-bb] Be kind to our old lady AO-7

Ronald G. Parsons w5rkn at w5rkn.com
Wed May 31 23:42:08 UTC 2017

Lately, AO-7 has spontaneously switched out of Mode B during passes over the US and probably other places. 

Since AO-7’s batteries are not functioning, it relies totally on its solar cells, which have limited capacity. As more users are online, and especially when one or more users are using more than the minimum necessary uplink power, the power system will fail and cause a switch out of Mode B. I have saved a FlexRadio waterfall display of four passes from around 2200Z from the four previous days. In three out of four passes, just before the unexpected mode switch, a strong CW signal popped up around 145.950 MHz. AO-7 switched out of Mode B seconds thereafter. I can’t  say for sure it was the cause but it happened three days in a row. Today’s pass had only one user, a low-power digital signal which appeared briefly, and no mode switch occurred. Screen shot JPG’s are available via the following link.


To minimize the chance of causing a switch out of Mode B, use the very minimum uplink power necessary. Even if a mode switch is not triggered, too much uplink power will cause distortion over the entire passband.

AO-7 has been a great satellite, and she deserves our tender loving care.



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