[evlatests] Sampler statistics with fully attenuated T304s

[Walter Brisken]

A few of us were wondering at one point what the sampler output would be 
for a zero input level.  The closest I could come was to set both the RF 
and OUTPUT attenuators in the t304s to 31dB and place an upper limit on 
the self noise of the samplers.  Here are the histograms in text form for 
the 8 samplers:

level	14A	14B	14C	14D	16A	16B	16C	16D

-6	0	0	0	0		0	0	0
-5 	0	0	0	0		0	1	43248
-4 	707	0	0	0		0	175431	934787
-3 	985383	0	0	0		2	873047	70541
-2 	62486	2640	0	12740		884886	97	0
-1 	0	1045355	67102	1035809		163688	0	0
  0	0	581	772727	27		0	0	0
  1	0	0	208522	0		0	0	0
  2	0	0	225	0		0	0	0
  3	0	0	0	0		0	0	0

Ant 16 T304A seems dead.

Note that for 14C all values of L304.OBSERVE_BAND_SELECT (except 5, which 
was used in the above) gave a wider distribution so it is likely that 
the width is due to some signal still getting through the attenuators.
Aside from 14C (and not commenting about 16A) a limit of less than 1 
sampler unit of noise is incurred in the sampling.

-Walter