On 01/29/21 15:45, Zach Metzinger wrote:
I might also hazard a guess that either or both of the U4 or U2 power amplifier driver stages has failed.
I did a little more thinking, and one might be able to figure out if antenna deployed or it is a amplifier issue.
Transmit a powerful two-tone signal that is demonstrated on a ground model of the linear transponder (really a translator) to cause distortion products from the 1st mixer to fall in the passband, but just barely enough power to make this happen (given the additional path loss and possible polarization loss).
If the distortion products are detectable on the downlink, then the antenna is deployed and the IF strip is likely still active. The failure is probably in the PA section.
If the distortion products are not detectable on the downlink, then there is attenuation between the ground station and the first mixer (or you need a more sensitive RX antenna). This points to a failed antenna, coax, LNA, etc etc. This is a failure before the PA, in any case.
While the lack of detectable telemetry points more toward the failure being in the PA section, that failure could be additional and unrelated.
--- Zach N0ZGO