[evlatests] Antenna 12A

[Keith Morris]

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)