[evlatests] New Temperature Sensors on Antenna 21 & 22

[Bob Hayward]

Keith Morris & I installed 8 additional temperature sensors on Antennas 
21 & 22. The hope is that this will give us a temperature profile of the 
receivers in the bottom and top floors of the Vertex Cabin. It will also 
allow us to measure the "heat pipe" effect of the feeds on the noise 
diodes.

Thanks to Wayne Koski, we can now feed the signals from these 
temperature sensors into the spare analog inputs of the M303 utility 
module. With Hichem Ben Frej's help, the temperatures are now being 
logged in the EVLA monitor archive.

The sensors have been mounted on the L & Ku-Band receivers located in 
the lower and upper levels of the Vertex Cabin respectively. The 
original intent was to measure the temperature of each feed at the top 
where it enters the roof of the Vertex Cabin and at the bottom near the 
top of the receiver, thus giving us a feel about how each feed, much of 
which sticks outside in the cold, cruel New Mexico climate, modulates 
the temperature of the receivers, and thus the power out of the noise 
diodes.

This was easily done on the L-Band feed. Alas, there is not much of the 
Ku-Band feed inside the cabin (most of it is outside) so there is only 
room for one sensor on the feed. The displaced 2nd sensor was mounted on 
the Q-Band noise diode. It has a waveguide noise diode that may be more 
thermally isolated from the temperature of the bottom plate of the 
receiver, and it is also close to the Model 22 fridge, which generates 
heat and may well be buffering the temperature of the noise diode. (We 
would have liked to put this sensor on the Ka-Band waveguide noise diode 
but there was no way to do that without disassembling the front plate of 
the receiver to gain access.

For future reference, here is a list of the temperature sensor number, 
M303 analog input and where the sensor is located (Antenna 21 and 22 are 
outfitted in identical fashion):

Temp-1   Analog-03   L-Band - Top of Feed (inside of Vertex Cabin)
Temp-2   Analog-06   L-Band - Bottom of Feed (near top of receiver)
Temp-3   Analog-09   L-Band - Noise Diode (inside RF Box)
Temp-4   Analog-12   Air Temp of lower Vertex Cabin near L-Band Rx

Temp-5   Analog-04   U-Band - Feed (inside of Vertex Cabin)
Temp-6   Analog-07   Q-Band - Noise Diode (mounted on bottom of Dewar)
Temp-7   Analog-10   U-Band - Noise Diode (inside RF Box)
Temp-8   Analog-13   Air Temp of upper Vertex Cabin near U-Band Rx

Note that Bob Broilo is hoping to install extra insulation on the 
Antenna 21 Vertex Cabin (above the dish) to see how that would affect 
the air temperature inside.

-Bob