[evlatests] L-Band RFI

[Rick Perley]

    A new observation at L-band gave me some decent looks at our current 
environment.  A few interesting issues ...

    1) Radar signals are easy to identify because of their regular 
pulsing (really cool to see in SPFLG!).  We have radar signals at:

    1254.5, 1300.0, 1310.0, 1320.0, 1330.0, and 1338.0 MHz.  The signals 
at 1300, 1320, and 1338 are very weak.   None of these will cause any 
future troubles, as they are nowhere near strong enough to contaminate 
adjacent channels (after Hanning-like smoothing).  Zap the affected 
channel, and move on ...

    2) In the past we've had *huge* signals, very wide in frequency, 
centered near 1245 MHz.  These are definitely not radars.  However, in 
this new observation, these are virtually absent. 

    3) The entire band between 1929 and 1989 MHz is occupied with what I 
believe are cell emissions.  (Dan -- is this right?)  In the more 
distant past (a couple years ago), these were entirely open.  The 
signals are quite strong.  Pity. 

    4) The two 128-MHz-wide bands centered at 1435 and 1820 MHz are 
almost entirely free of RFI. 

    5) The internal 1408.0 MHz birdie, reported on a few days back, is 
still with us, with the same characteristics as reported earlier. 

    Rick