[evlatests] Antenna issues from 28 July

[Ken Sowinski]

On Thu, 30 Jul 2009, Rick Perley wrote:

>    Some interesting oddities occurred during the 5-hour run on 3C286,
> last Tuesday night:
>
>    1) Antennas 3 and 23 have a large residual phase wind -- 3 to 3.5
> turns over the 5 hours.  No other antenna has a net phase slope.

shadowing?  This antenna is on CE1 and 3C286 was setting
in the NW.

>    2) Antenna 2 showed a 50% drop in visibility phase over the last
> hour -- this was a smooth drop, as if  pointing had wandered off
> somewhat.  No other antenna had any such effect.

These are the outermost two antennas on the east arm.
No explanation offered.

>    3) Antenna 25 had numerous stepwise amplitude gain changes -- the
> ratio of the highest to lowest is a factor of 2 (equivalently, a factor
> of four in power).  These changes were accompanied by distinct changes
> in bandpass ripple.  Are we sure the attenuators weren't changing on
> this antenna?

It certainly looks like they were changing.  Hard to see
think of a reason.  Was this antenna included from the
very beginning and never removed from the array?