[evlatests] antenna 28 pointing still bad

[Ken Sowinski]

> On Tue, 11 Nov 2008, Ken Sowinski wrote:
>
>> Meanwhile I can say two things about how the antenna is
>> misbehaving.  These signatures amy be a consequence of the
>> azimuth encoder tracking error, or be independent problems;
>> it is hard to distinguish.  1) The measured azimuth pointing
>> is proportional to elevation and varies about an arc-min
>> between elevations of 15d and 115d (over-the-top).  It is
>> *not* fit by the usual perpendicularity term.  2)  The
>> measured elevation pointing error is bistable; between about
>> 70d and 150d it is close to zero, elsewhere it is about
>> -0.5 arc-min.  Neither of these two signatures can be fit
>> by any terms in the standard pointing model.  I have plots
>> illustrating these if anyone wants to look at them on
>> Wednesday.

A more careful look at the elevation pointing errors described
under 2) suggest that the two states correspond to looking in
the south or north.  The transitions occur at about 90 degrees
and about 250 degrees.  It is hard to see any connection, but
there may be a dependence on the cable wrap chosen when looking
in the north.