[evlatests] WIDAR data

[Walter Brisken]

On Mon, 24 Nov 2008, Michael Rupen wrote:

> Did you check this in a single (1 second) integration, and separately for the 
> three different LO offsets?   We want the fewest possible turns of phase
> within a single integration, to see whether this all works as expected.

Yes -- the non-detection of the aliased maser line holds for both scan 
averages and for individual (coherent) integrations.  However, there is 
some unexplained excess power in channels IF3/997-1005 that shows up when 
incoherently averaging over 1 scan.  The magnitude of this power is 
similar for each offset frequency used.  The odd thing is that the mirror 
image of the brightest maser line should lie in channel 993 where in fact 
there is nearly no excess power, and the shape of the excess power bump 
does not match that of the maser spectrum.  The source of this extra power 
is uncertain.  It could be another maser feature far enough from the phase 
center to average out over a few minutes.

If possible, on the next similar test, it would be good to observe with 
two frequency tunings to identify reflected(aliased) from real signal.

-W