[evlatests] phase jumps on L6 changes

[Gustaaf van Moorsel]

Yesterday I reported on occasional large phase jumps (in the difference
between IF 1 and IF 2) on VLA antennas triggered by a change in L6.  The
signature is a large - many tens - of degrees jump after which the phase
returns to the old value at the next L6 change.  It was suggested I cont-
inue to investigate this behavior, this time by changing bands while keep-
ing L6 constant.  This was done this morning.

I observed in L, C, and X band, one minute each, in rapid succession.  L6
was unchanged between band changes, as were the flukes.  The result is
that none of the phase jumps we now associate with L6 changes were seen.

This lends further credence to the theory that somehow L6 is to blame.
As I reported yesterday, antennas 8 and 12 are the worst offenders.

Gustaaf