[evlatests] First Ka-Band Receiver on the EVLA

[Robert Hayward]

Brent, Hollis, Jake and I installed the first Ka-Band receiver (S/N 1) 
on Antenna 4 today and is cooling nicely.

It failed the leak test at Cryo so some rework was required, including 
the opening up of the receiver to remove an offending hair from the 
dewar can O-ring. It's leak rate is now better than a typical Q-Band 
receiver. Thanks to Rudy, Jimmy and Frank for beating it into submission.

As predicted, there was not enough LO Ref power available at the output 
of the UX Converter (we measured about 1 dBm at the receiver input, we 
really need about +6 to +9 dBm to keep the downconverters happy). So the 
amp we salvaged out of the old VLA-style K-Band was definitely needed to 
give us an adequate drive level.

The IF output level (while the receiver was warm) was about as strong as 
the K-Band receiver sitting beside it and we inserted 8 dB pads (just as 
we do with the K-Band). We may need to modify this attenuators as we 
gain experience with the receiver.

Ramon indicates they were unable to do a final alignment check to the 
sub-reflector before they installed the Goretex radome. I think they 
like to do this with a fixture mounted on the feed (a new fixture may 
need to be designed that is small enough to fit inside the feed tower).

We didn't get a chance to do a final check of the switched power at the 
T5. We'll do that tomorrow.

The DC power was glitched thanks to the smoke detector in the Vertex 
Cabin. The antenna had to be resynchronized by Steve and Rob. Ken will 
probably have to check the reset the delays.

Ken also have to play with the pointing and sub-reflector offsets...

-Bob