[evlatests] A curiosity with antenna 12

[Keith Morris]

This turned up in the CX and CK observations today, as well.  Switch S4 
(M301) and S7 (T303) were commanded to a different position at the 
beginning of the scan, and then commanded to the correct position 5 
seconds later.

However, there are other dropouts in T304 power that cannot be explained 
by these switches.  I'm still investigating.



Ken Sowinski wrote:
> On Fri, 25 Jun 2010, Rick Perley wrote:
> 
>>    Michael took a short (27 minute) observation in 2 GHz-wide mode a
>> couple days ago.   Eight full-polarization subbands, each of 128 MHz
>> width, in each of the AC and BD IFs.  In general, beautiful data.
>>
>>    It was noted that antenna 12 had a curiousity -- once every minute,
>> on all subbands, in all polarizations, the amplitude dropped by about
>> 10% for a single 1-second record.  This was the only antenna for which
>> such a effect was noted.  As the script asked for a new scan every
>> minute, I had assumed the 'drop-down' was a first-record, or perhaps
>> second-record problem.  It's not!
>>
>>    This 'drop-down' is a 2nd-record effect -- the 2nd record of every
>> scan is low by this much.
> 
> this is still happening.  It is really synchronous with the
> the new scan and is happening at the antenna.  The evidence
> is that all the T304 power meters show a one or two dB dip
> at each scan.  Since it is seen in the input power meter it
> must be happening upstream of the downconverters.
> 
> _______________________________________________
> evlatests mailing list
> evlatests at listmgr.cv.nrao.edu
> http://listmgr.cv.nrao.edu/mailman/listinfo/evlatests

-- 
Keith Morris
National Radio Astronomy Observatory
1003 Lopezville Rd.
Socorro, NM 87801
575-835-7060 (phone)
575-835-7027 (fax)