[evlatests] A curious new birdie at X-band

[Rick Perley]

    As part of the 'receiver rotation' experiment, I've taken wideband 
data covering all of L, S, C, and X bands. 

    Looking at the higher half of X-band (10 to 12 GHz), one, and only 
one, piece of RFI is seen.  It's a pure tone, at

    10750 MHz
   
    This is not a harmonic of 128 MHz (but is close -- the 84th harmonic 
is 10752 MHz).  No other birdies are seen, so this tone is definitely 
special. 

    And it's only seen on antennas near the center of the array -- 
strongly arguing for a local origin. 

    The autocorrelations are useful for diagnosis -- unfortunately, only 
half the antennas provide this (what do we have to do to get them all?)

    Antennas with strong 10750 MHz tone are:

    ea13 at W02
    ea15 at E02
    ea22 at N02

    Antennas with detectable tone (but weaker than above list) are:

    ea05 at W08
    ea09 at W10
    ea11 at W06
    ea24 at W04
    ea 26 at W12

    Antennas with no visible tone (in autocorrrelations) are:

    ea01 at N14
    ea03 at E10
    ea07 at E12
    ea17 at E14
    ea19 at W16
    ea28 at E16

    All other antennas provided no autocorrelations.
    The cross-correlation data are consistent with a local origin, near 
the array center.