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

[Dan Mertely]

Something to look for:  Generally, band reject filters have
rather significant (and "bouncy") phase changes at both the
low and hight frequency transition points.  It could lead to
cal problems in the adjacent sub-bands.  -Mert


Rick Perley wrote:
>     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. 
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