[evlatests] Sensitivity and Dropouts with Phase Switching off

[Barry Clark]

>     For reasons unknown, the data from both 14 and 16, with the
> phase switching on, was of very poor quality.  Amplitude dropouts --
> total dropouts -- occurred regularly in both antennas.  These are
> different than the 10-second interval, partial 'attenuation' that we've
> reported before.  Thus, unhappily, we have no 'before' state.

The dropouts I observed earlier were not "total" but reductions by a
factor of a few.  There is also the interesting fact that the AOC-VLA
link was saturated at the time, making communications slow and hazzardous.
I suggest that the cause of the dropouts is that the computers on the
evla subnet got confused about what the time was, and thus offset the
phase switching by one or more 52 ms ticks.

If this is indeed the case, the best solution would be to buy a computer
with a GPS card to serve as an NTP server.  A much less desirable solution
would be to lock out NTP time resets on L302s except on reboot or on
command.