[evlatests] Round-trip phase meters.

[Barry Clark]

> From: vdhawan at aoc.nrao.edu
{snip]
> 	The two round-trip meters did not report identical fiber length, 
> 	one read 95% of the other on (24-hr) average, with variations
>	both ways on 30min timescales. 

The way the meters are implemented, a scale error is not a possible effect.
It is an indication that the meter is not performing as described in its
theory of operation - it is broken.

> 	Question: what was the length of the test fiber compared to the max
> 	in A-array?  NM array?

At the burial depth of 1m, the diurnal effect on the long cable runs should
be down by of order four nepers, so the diurnal effect on the 21 km run 
should be comparable to that of the exposed cable, but not much more.  The 
annual term is almost unattenuated and thus substantial.