[evlatests] L-Band Frequencies

[Rick Perley]

    All:

    I've reviewed the L-band RFI spectrum, using the high-resolution, 
full-band spectra produced during WIDAR0 testing.  Some results and 
recommendations:

    A)  'Low' end:  The satellite RFI begins abruptly at 1524 MHz -- 
from there until 1640 MHz, essentially all is lost (except for a few 
narrow slots).   There are strong emitters (as many of you have found) 
from 1244 to about 1260 MHz, which lies within the current low default 
setting.
    I recommend that for the adjacent low-end tunings we move the 
defaults up by about 20 MHz -- i.e. to center at/near 1328 and 1456 
MHz.  This puts the lower edge of the lower subband at 1264 MHz, and the 
upper edge of the upper subband to 1520 MHz.  This will avoid the worst 
of the signals, but still leaves in the ABQ radars, and the GPS L3 link 
(which is very occasional, so not a big issue).  Not perfect -- but hey, 
it's a rough neighborhood...

    B) 'High' end:   I learn with surprise that for the adjacent high 
frequency pair we have selected centers at 1820 and 1948 MHz.  A bad 
decision, for which I take full responsibility.  The problem is that 
between 1930 and about 1980 MHz lies a multitude of emission, which I 
think are from cell phones. 
    I recommend, for this pair, center frequencies of 1860 and 1732 
MHz.  This will avoid the cell communications, but overlaps some RFI at 
1680 MHz (strong) and 1690 MHz (weak).  However, as I believe these are 
due to meteorological broadcasts, perhaps there is hope these are 
intermittent?  Perhaps Dan Mertely can shed light on this...

    C) There is no need to change the current 'separated' pair 
frequencies (1436 MHz and 1810 (?) MHz) -- these lies in quite safe zones. 

    Rick