[evlatests] Status of the Ka & Q-Band Receivers on Antenna 1

[Robert Hayward]

We repaired the Q-Band receiver on Antenna 1 this afternoon (Friday). You
may recall that the LCP side had died last week and we ended up removing
the 40-50 GHz post-amp and mixer assembly (rather than pulling the entire
Q-Band receiver as we would usually do) on Tuesday after we finished the
installation of the new Ka-Band receiver. Back in the lab, I found that
the post-amp had died. It wasn't a simple popped wire-bond as expected but
a failed MMIC amplifier chip, which I had to replace. After remounting the
assembly, the receiver was back in a good operational state. I believe
this may be the first time we've ever done a repair like this in the field
on a Q-Band.

As for the Ka-Band receiver, it checked out fine also. We were unable to
contact Ken to find out what his latest tests had uncovered this morning
but the last we had heard was that although the receiver was producing
good TP and SP data, there were no fringes. Today, when we went to check
whether the feed might still be covered by a metal plate (or had dead bird
or rodent trapped inside), our fears were allayed as we could see the
Total Power increase as the hatch to the surface was opened and increase
even more as Bob Stupak climbed out with the ubiquitous Hot Load in his
hands. Enough said that the Hot/Sky Y-factor was sizable (well over 7 dB)
suggesting a Trx of 20K or so (which is not too shabby). So the receiver
is certainly well coupled to the sky. Just why Ken is not seeing any
fringes must be a more subtle problem than poor receiver sensitivity...

-Bob