[evlatests] C band response

[Gustaaf van Moorsel]

It has become clear from the first reactions after the announcement
of the extended C-band opportunity that observers are particularly
interested in the frequency range 5900 - 6700 MHz, which is not
surprising given the OH and Methanol lines there.  This happens to
be the same interval which in my previous determination of the freq-
uency dependent response shows strong resonances.  However, at 100
MHz between points and a much narrower bandwidth the interval of
interest was insufficiently sampled.

I now present, in the attached plot, the results of a full sweep
covering this interval, with 25 MHz bandwidth (spectral line) and
25 MHz interval between points.  It now much clearer pinpoints the
frequency intervals to avoid.  For comparison, I also observed at
the standard C-band frequency of 4800 MHz (not shown in the plot).
The y-axis is the K value as used in the Observational Status Sum-
mary, assuming its value at standard C-band (4800 MHz) is 6.0 (for
EVLA antennas).

Note that the two OH lines the results of which I showed last Friday
are at 6031 and 6035 MHz, just outside the resonance (at redshift 0).
The methanol line at 6668 MHz lies in a non-resonance zone.

Gustaaf
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