[evlatests] One more note on 74 MHz

[Mark Claussen]

I note that the birdie also shows up, more weakly, in
An18, IFC.  I have plots that I will give to Steve D. and
Chuck K.   Also, note that, for our standard observing at
74 MHz (which is what we did), the AC and BD IFs are
set to the same *sky* frequency, so this isn't RFI from
the sky.

Mark