[evlatests] WIDAR P-band status update: 17MAR2015: ea13

[Dan Mertely]

ea13 LBR re-check:
I took another look at the signal going into the LOIF rack
yesterday (Thursday 20150319) to see if I could see the cal
signal bounce in the P-band or 4-band bandpasses.  I used
a zero-span, 1 MHz RBW, 100 mS sweep technique with a spectrum
analyzer that had worked very well last year in showing the cal
signal on ea24.

It didn't show, so I also checked ea09 next door.  No sign of
the cal signal there either, so I guess that ea24 at that time
must have been one of the few remaining antennas with the LBR
cal set very high.  Paul and I have some additional tricks up
our sleeves and will do some additional cal problem debug next
Monday (if we can get on).

Meanwhile, after re-connecting the LBR RF coaxes to the proper input
ports of the LOIF rack (repairing my error from yesterday), I also
saved some bandpass plots from the signal going into the LOIF rack.
(Attached.)  The RFI on the RYH side looks weak, as reported by Huib
(below).  The LXV side looks normal on the high frequency side, but
should also show a bit of RFI on the low side--it didn't.  However,
due to the rain I was unable to cross the input coax cables up in
the barrel to test where the weakness was originating--something
else for next Monday.
-Mert

On 3/18/2015 3:24 PM, Huib Intema (NRAO) wrote:
> Dear P-banders,
>
> Here is the outcome of a short VLA WIDAR P-band status test (few minutes
> on 3C48) we ran on the morning of March 17. EA02 and EA04 were out.
>
> Major points of attention are:
>
...
> - EA13 has slow bandpass ripple on XLV (21 MHz = 7.2 m; reported previously)
> - EA13 has low power and somewhat erratic bandpass shape in YRH (about
> 20 percent of median; new)
> - EA13 has slow bandpass ripple on YRH (~22 MHz = 6.8 m; increasing
> since late Jan/early Feb)
> - EA13 has zero Pdiff, meaning no switched power
...
> -- Huib
>
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