[evlatests] 3-bit tests -- 7 Sept.

[Rick Perley]

    Ken/Michael arranged to supply the samplers with a range of input 
powers, from -38 dBm to -26 dBm in 5 levels (i.e. steps of 3 dB). 

    I've reviewed the data.  The power changes are easy to see in the 
gain solutions.  But the curious (disturbing?) result is that there is 
no effective change in rms noise in the 'blank sky' histograms between 
the max and min powers.  The other (disturbing?) effect is that both 
polarizations are much noisier than in the test of last week -- 
typically .25 to .35 Jy rms, when 0.16 is the expected value.  Two 
baselines (22 x 27 and 22 x 28) in RCP have noise over 0.5 Jy. 

    Ken notes is was raining at the time, so perhaps the elevated noise 
is from excess cloud emission.  We think that, over the range in power 
level, the expected effect might be ~10% of the proper noise -- say, .02 
Jy, which is difficult to see in the high noise. 

    We should try again tomorrow, in hopefully better weather