[evlatests] Latest on Ka & Q-Band Receiver Installations

[Robert Hayward]

On Tuesday we had rather more success that the last 2 attempts to install
our 3 latest high-frequency receivers on the EVLA:

Antenna 25:
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A-Band S/N 6 was successfully installed (finally) on Antenna 25 after
sorting out earlier problems with its Card Cage as well as a failed LNA.
The receiver was cooling when we left and we could see the Cal when fired
using the T304's total power detectors. Thus all seems to be going
properly so far. The feed had been aligned to the subreflector last week
but the Antenna Mechanics will redo it again since we had to disturb the
alignment when we had to return the receiver back to the lab. I'll forward
Tcal values to Ken tomorrow.

By the way, the Q-Band receiver's heliax cables had accidentally been left
disconnected last week after pulling the Ka-Band system. The Q-Band is now
back in a functional state.


Antenna 1:
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A-Band S/N 5 was successfully installed on Antenna 1 following the
reorientation of the feed tower "spider" by the Antenna Mechanics so the
receiver would fit properly between the Q-Band receiver and the wall. The
turn-buckle brackets have yet to be installed and the Antenna Mechanics
will also have to align the feed to the sub-reflector and the metal plate
over the feed tower will have to be replaced with a Goretex radome.
However, the receiver was cooling when we departed the antenna and we
could see the Tcal being fired in the monitored total power. I'll forward
its Tcal values to Ken as well

While on Antenna 1, we investigated a complaint that the Q-Band's LCP
channel was dead. This was confirmed. As best we could tell, the signal
coming out of the dewar is OK so we removed the MMIC post-amp and Spacek
mixer for evaluation back in the lab. More news on sorting out this
problem shortly.


Antenna 28:
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Q-Band S/N 19 was installed on Antenna 28. The turn-buckle brackets will
have to be installed by the Antenna Mechanics and they will have carry out
the feed-subflector alignment procedure as well as replace the metal plate
with Goretex.

We encountered a problem interfacing to the UX Converter - the LO heliax
didn't have a the required 20 GHz right-angle adapter installed and we
didn't have one on us - so the UX Converter is out of commission until we
send one out tomorrow. Since this antenna is still experiencing pointing
problems, we assumed not being able to use K, Ka or Q-Band for the next 24
hours would not be a problem.

By our reckoning, 3 steps forward and only one step back...

-Bob