[evlatests] set-and-remember test results

[Steven T. Myers]

C-band:
One strange thing I see is that at C-band two antennas ea09 and ea20 "missed"
some scans (signal was like off-source noise),

ea09 missed scan 23:43:10~23:43:40

ea20 missed scans 23:43:10~23:43:40, 00:16:10~00:16:40, 00:26:10~00:26:40

ea26 multi states as Rick noted

No signs of 1db offsets, other than the ea26 behavior

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X-band:
I did not see the above behavior at X-band, but did see some strange 
antennas:

ea04 RR 00:11:40.5 - 00:12:09.5, 00:12:40.5 - 00:13:09.5
amplitude dips that lasted a couple scans but only in 1 polarization, e.g. 
(LL was constant), these didnt look like 1db offsets for example.

ea05 1db offsets occasional scans both RR and LL

ea07 RR and LL dips around 23:52 (pointing?)

ea13 missed scans 00:05:40~00:06:10, 00:10:40~00:11:10, 00:12:10~00:12:40

ea26 multi states as at C band

many antennas show variation (some like weather, others not) as Rick noted

On Sun, 21 Feb 2010, Rick Perley wrote:

>    Tests of the 'set-and-remember' observing mode were done Friday
> afternoon.  The test was to observe 3C84 for one hour, switching between
> C and X bands every 30 seconds.  A pretty stern test.  Ideally, there
> will be no amplitude changes (that cannot reasonably be accounted for by
> atmospheric or pointing effects) throughout each band's observations.
>
>    Results:
>
>    A) At C-band, the gain stability looks quite good, with one notable
> exception:  Antenna 26 has two different amplitude states in RCP, and at
> least 3 in LCP (plus some other bizarre phenomena).  In RCP, the two
> states are separated by 1 dB in power.
>    The weather must have been rather poor -- there are small (< 1%)
> changes in cross power on most antennas, acting on plausibly atmospheric
> timescale, well correlated between the two polarizations.
>
>    B) At X-band, the situation is much more confused.  Most antennas
> behave as at C-band, with somewhat larger (but still small) amplitude
> changes well correlated between polarizations.  I would again interpret
> these as the effects of a bad weather day.  But there are some
> spectacular exceptions:
>    Antenna 15 has two amplitude states, in both polarizations.  But the
> step in amplitude is 15%, corresponding to 1.2 dB -- rather farther from
> 1 dB than I had expected.  Is this reasonable?
>    Antenna 26 is quite bizarre, with four different amplitude states,
> again separated by rather more than 1 dB.
>    Antennas 14, 16, 18, 23 and 24 are showing apparent gain stability
> variations which are not plausibly atmospheric (they change in
> synchronism with the switching), and are different between the two
> polarizations.
>
>    The ordering of the IFs at X-band is still reversed, as noted earlier.
>
>
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|:| Steven T. Myers                      |:|  Tenured Astronomer       |:|
|:| National Radio Astronomy Observatory |:|  Ph:  (575) 835-7294      |:|
|:| P.O. Box O, Socorro, NM 87801        |:|  FAX: (575) 835-7027      |:|
|:| http://www.aoc.nrao.edu/~smyers      |:|  smyers at nrao.edu          |:|
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