[evlatests] Tests on Variable Power output from Ant. 14 T304D

[Rick Perley]

    Bob and I returned to antenna 14 today to do further work on
the peculiar variable power seen last Tuesday from downconverter
`D', in antenna 14. 
    The phenomenon was again seen, with the same characteristics
described on Tuesday.  We soon determined that the phenomenon
is in T304-D alone, and is not seen in any of the other three
downconverter outputs.
    We also checked the stability of the L302 LO input:  over a
twelve minute period, a drift of <0.1 dB was seen, and steps in
power of ~0.01 dB were occasionally noted.   We are assured
by Travis that such changes are far too small to account for
the sporadic change in power level noted at the output of the
T304D module. 
   
    As the weather was cloudy with thunderstorms, it was not
useful to measure system temperature (the clouds were adding
a variable temperature of up to ~7K), nor especially any tests
on the change of SNR throughout the signal chain.  We will
have to attempt these next week.