[evlatests] Anti-DSR S-Band Filters in ea21 and 23

[Rick Perley]

    The digital satellite radio signals from Sirius and XM satellites 
dump a lot of power into our S-band receivers.   Any subband overlapping 
the 2310 -- 2350 MHz span is currently made useless. 

    Two stop-band filters designed to block this frequency band are now 
in antennas 21 and 24.  They work quite nicely -- the autocorrelation 
spectra show there are no signals within 35 dB of the receiver spectral 
noise power within that frequency range.  In the cross-power spectra, 
there still remain faint remnants of the DSR signals, but these are now 
weak enough to enable observing at adjacent frequencies within the 
subband. 

    The switched power data for the subband containing these signals 
appears to be good, with the expected system temperatures. 

    More tests will be needed to better judge the beneficial effect of 
these filters on the subbands which do not contain the DSR signals.