[evlatests] calibrator flux survey preamble

[Barry Clark]

> Seems to work, but there are peculiarities at C and X band.
> To get enough power out of the deformatters for the T4 requires
> driving the DTS modules very hard.  Only when the sampler value
> RMS is between 30 and 60 is there enough drive to the T4 to allow
> the ALC to level.  This happens for all IFs and only at C and X band.
> The antenna does seem to fringe at C and X band, howver I can say
> nothing about sensitivity.

Sounds like our old friend the oscillating P band receiver, putting a 
very strong birdie in the 1-2 GHz band presented to the DTS.