[evlatests] Current P-band state

[Walter Brisken]

Hi Rick,

Antenna 24, by mistake, did not get its attenuators changed since last 
time and at that time its performance was not so bad (I think about 4.6 
and 5.4 compared to ~3.5 for VLA, then square), so it seems that the poor 
performance must be due to more than just attenuator levels. There is 
another bit of evidence that supports this statement -- that is that _no_ 
EVLA antenna is as good as the typical VLA antenna and there are several 
dB of slop that the VLA system should compensate for.  This is, unless, we 
are overdriving in general the downconverters, which I still think is a 
possibility.  I would have predicted a "10 dB" rule, rather than the "5 
dB" rule I used in setting the attenuators previously.

-W


On Thu, 18 Oct 2007, Rick Perley wrote:

>    The P-band status on the EVLA remains poor.
>
>    EVLA antennas 14, 17, 18, 19, and 23 are close to nominal
> sensitivity on most IFs.   The exceptions amongst these are all on the
> (A,C) side (IF#1).
>    EVLA antennas 11, 21, 24, and 26 all show very poor sensitivity,
> generally low by a factor of 4 or more in apparent efficiency.  26B and
> D give no fringes at all.   (Antenna 21 is definitely better than prior
> to Walter's attenuator adjustment, but remains weak by a factor for four
> or more on all IFs).
>    EVLA antenna 25 gives no fringes on any IF.
>
>    There was no 'global' phase jump between the two P-band scans.
>
>
>
>
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