[evlatests] Antenna 12A

[Keith Morris]

First of all, I meant 3 seconds, not 300 milliseconds.

Second, Hichem is fixing this as we speak, and looking for others that 
may have the same problem.



Keith Morris wrote:
> The "o period" field in the T304 in 12A is set to 10 seconds.  In all 
> other modules, this field is set to 300 milliseconds.  This fix should 
> be added to the MIB fix file until such time as the MIB can be safely 
> reprogrammed.
> 
> 
> 
> Rick Perley wrote:
>>     A most peculiar effect is noted in antenna 12, IF 'A':
>>
>>     In the test done yesterday wherein I change bands each minute, all 
>> (functional) antennas return to a uniform, stable, and repeatable fringe 
>> level, with a single exception:  antenna 12, in IF 'A'. 
>>
>>     For this antenna, at all bands *except* X, the fringe power level 
>> abruptly changes about 20 seconds after all others have established 
>> their continuity.  For most bands, this occurs about 30 to 40 seconds 
>> after the command to change band has occurred.  The change in effective 
>> power (the square of the amplitude jump) is large!
>>
>>     L     8 dB down
>>     S      erratic, up and down.
>>     C     15 db up
>>     X     No effect (but the observation followed referenced pointing at 
>> X band, so I bet the effect is there)
>>     Q      9 dB down
>>     Ka    6 dB up
>>     K      6 dB down
>>     U      7 dB up
>>
>>     The sequence listed above is the order in which the observations 
>> were made. 
>>     This 'effect' most likely originates in the T304's attenuators.  
>> It's as if 'set and remember' has been replaced for this IF with 'set, 
>> and readjust it later'.  As expected, the switched power tracks the 
>> change. 
>>
>>
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> 

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