[evlatests] R/L phase differences.

[Vivek Dhawan]

Re short-term changes in cross-polarization, reported by Bob Sault:

There is something weird happening.

I still do not think it is in the LO itself, although I'm not as
sure as I sounded this morning. It could still be something different
in the path taken by R and L after bifurcation, downconverter onward.

Some plots are attached, all are 0.4s integration.

1. 14 minutes at X band, default 8435 and 8485. The short jagged
changes are probably mostly from the delay cogs, and are bounded
to ~10 deg pk-pk. There is no long term trend, but the minute-
scale periodicity I do not understand.

2. Same data, 2 minutes segment - I don't know if the various
quasi-peroids are expected or not?


3. K band on orion, 3MHz conntinuum on a strong line. The phase
wander looks quasi-random, and very little sign of the delay cogs.

The other IF pair was tuned to exactly the same frequency, but
shows (on some antennas) a different variation pattern, and on
other antennas a curious symmetry - the wander in one pair is flipped
in sign in the other pair - i.e an up/down symmetry. Again, not sure
what it means, but does not smell good.

V.


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