[evlatests] More on 128 MHz comb

[Rick Perley]

    The limited spectral sweep done by Ken this morning has already 
given us a lot of information on this 128 MHz comb. 

    As noted earlier, it is limited to the antennas towards the end of 
the north arm, and appears strongest on 8 * 10. 

    It is in both polarizations, and is seen in both cross-power and 
autocorrelations. 

    It is seen at L, S, and C bands.  The reason that most of the 
earlier reports have singled out S-band is that the strength of the comb 
is *much, much* stronger in S-band than in any other. 

    The odd harmonics are much stronger than the even.  Most even 
harmonics are not visible -- the strongest is the 32nd harmonic -- at 
4096 MHz.  (But I imagine this one could have a different origin). 

    The lowest frequency I could find the line was at 1408 MHz (11th 
harmonic).  The highest was at 4992 MHz.  Both of these are weak 
compared to the Sband harmnics.

    The strongest harmonic is the 25th, which is at 3200 MHz.  To a 
reasonable approximation, the harmonics weaken uniformly for both higher 
and lower harmonics. 

    There are many other narrow responses seen, not multiples of 128 
MHz.  A complete tabulation will be made when all the data are available.