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All,<br>
<br>
Jason and I spent some time today sorting out the proximate cause for
the<br>
anomalous readings seen last week with the Ka Band Receiver/CCB setup.<br>
<br>
As you'll recall, Brian reported that, when looking at the sky, he
would expect<br>
to see total power counts of about 2,000 to 2,500; but, instead, all
channels<br>
seem to be setting somewhere around 14,000 to 14,500 counts.<br>
<br>
After going through many gyrations, Jason and I determined that the new<br>
TWINAX cable sets had actually swapped the polarity of our differential<br>
signals going into the CCB's input ports...<br>
<br>
Since this would make our readings appear to be "upside down" (i.e.,<br>
"full scale" would read "zero", while "zero" would read "full scale"),
this<br>
could easily explain the anomaly which Brian reported...<br>
<br>
What I DON'T understand though, is how we could have possibly missed<br>
this while conducting our "final" lab tests... Brian, is it possible
that we failed<br>
to conduct any hot/cold tests <u>after</u> we introduced the new
cables? I realize<br>
that, by then, our focus had moved to sorting out phase switch
glitches, etc...<br>
<br>
Anyway, come Monday morning, we'll adjust the polarity of the TWINAX<br>
cables, check (and/or adjust) the calibration of the 16 amplifier
boards; then<br>
run through a series of hot/cold tests to verify our changes...<br>
<br>
INSTRUMENT STATUS...<br>
<br>
At this point, the CCB is running in the Receiver Lab (as ccblab) with
no input<br>
ports connected; although the receiver control cable is still
attached. <br>
<br>
The "demo_client" was disabled at the end of our testing session; so
the CCB<br>
should now be available on the network...<br>
<br>
Randy<br>
<br>
<br>
<br>
<br>
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