[evlatests] L352 round-trip phase: az/el effects.

[Vivek Dhawan]

EA 17 has 2 RTP units installed, measuring the same fiber.

The HVAC in 17 is not well behaved, (previous email) and the reading
of each meter shows a variation in response to the temperature.
However, the difference between the 2 meters has no discernible
temperature signature, which I think is good.

Bob Broilo is on the case.

The RTP difference IS sensitive to both AZ and EL changes, indeed
this is the dominant part of the variability, but its not simple:
it seems to depend on the direction of change as well as the rate.
There are also meter reading changes when neither AZ nor EL were
changing much.

Doug Gerrard and co are investigating if there is some unusual
strain on the fiber in 17.

Vivek.