[evlatests] Lunar PDif tests -- Q-band results

[Rick Perley]

    We continue to try establish the basic behavior of the 'PDif' gain 
monitoring mechanism at various bands.  Previous tests have used Cyg A 
and Tau A as 'standard sources'.  These work fine at lower frequency 
bands, but do not provide enough of a power increment at K, Ka and Q 
bands to establish if, and by how much, the PDif compression occurs. 
    Bob Hayward suggested that we look at the moon, an large blackbody 
emitter that will provide lots of power at high frequencies.  We did a 
trial run on Thursday morning, using all 8 (cassegrain) frequency 
bands.  The results for Q-band are given here.  Other bands will follow 
as time allows. 
    The tests were done in 8-bit mode.  The appropriate procedures were 
followed to ensure proper power levels were set. 
   
Q-Band:

AC frequency = 48 GHz.  BD frequency = 42 GHz.
The increment in system temperature appears to be about 140K, which 
doubles to triples the system power.  More than enough to establish the 
magnitude of the PDif compression. 

EA08 gives zero PDif (nothing but noise) on all four IFs.
EA10B gives integer zero PDif. 
Otherwise, all functioning antennas provided good PDif data.  The 
following table gives the observed 'PDif Compression':  
PDif(Moon)/PDif(coldsky):

Antenna         A          B         C          D
----------------------------------------------------
01                 93          91        98         87
02                100         92        87         92
03                 95          94        90         98
04                 98          91        88         93
05                102         91        83         88
06                  96         92        88         95
07                  98         97        88         84
08                         zero PDif
09                              out
10                  94        XX       91         81
11                  93         89        92         92
12                  99         94        93        100
13                  99         95        90         90
14                 101       87        100        98
15                   86        93         88         85
16                   96        91         94        96
17                   91        93         81        83
18                   98        91         90        93
19                   95        78         98        93
20                   80        81         92        94
21                   95        92         96        91
22                  101       94         91        89
23                   97        95         93        97
24                   88        89         94        90
25                   96        97         98        92
26                  100       93         96        93
27                   91        93         88        93
28                   97        95         87        90
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