[evlatests] Ka-Band S/N 2 on Antenna 2

[Bob Hayward]

The installation on Antenna 2 of its Ka-band receiver (S/N 2) is 
complete. The receiver appears to be cooling properly (115K as of this 
moment).

The LO Reference level was adjusted (using a 1 dB pad) to be within +/-1 
dB of the desired 0 dBm power level. I put 8 dB pads on the IF outputs, 
similar to what we use on the K-Band receivers. However, since the final 
output power can't be established until the receiver is cool, we may 
have to change these later to ensure the T303 UX-Converter is well below 
its compression point.

I believe the Antenna Mechanics aligned the receiver to the 
sub-reflector and replaced the temporary metal plate with a Goretex 
radome (they supposedly did this before I arrived at the antenna this 
morning so I may be over-enthusiastic on the virtuosity of the optical 
path).

We've also installed all the test equipment required to carry out total 
power measurements. As you may recall, Rick and I found the spillover 
contribution of the first Ka-Band receiver (and K & Q-Band as well) on 
Antenna 4 to be somewhat high (see EVLA Memo 125). The current thinking 
is that the sub-reflector may be exhibiting elevated resistive losses. 
We will do additional tests with Antenna 2, which is claimed to be a 
good performer, for comparison.

Thanks to Brent Willoughby, Bob Stupak and Craig Hennies from the FE 
Group for their help with the installation, as well as the Jimmy Sanchez 
& Sam Abeyta from the Antenna group and Jim Gregg & Michael Zamora from 
Cryo for slaying a few last minute dragons.

-Bob