[evlatests] antenna 24, mostly

[Mike Revnell]

Attachec are a couple plots from antenna 24 I collected in recent days.

exhibita.eps is from Monday morning. The low baseline level indicates no 
downconverter output power for any IF at the time. There are an assortment 
of spurious spikes across the bands. The feature to note is the mirror 
images of the spikes in IF C (green line). This is typical of what might 
be seen if the high and low wavelength digital fibers are swapped. Note 
that the spike in D does not have a mirror image.

exhibitb.eps is from this morning. Digitizer input power levels are 
normal so the spurs aren't aparrent. The equivalent symptom above would be 
that the shape of the curve would be too symmetrical. This plot looks 
normal to me.

As a comparison exhibitc.eps is from antenna 13 this morning.

Mike Revnell
National Radio Astronomy Observatory
Socorro, New Mexico
mrevnell at nrao.edu
revnell at ieee.org

On Tue, 25 Jul 2006, Ken Sowinski wrote:

> Rob and I tried to track down the problem with 24C.  The cross
> correlation looks funny.  autocorrelation and power levels all
> seem to be OK.  Swapping cables in various places we were able
> to convince ourselves that the problem most likely lay with the
> DTS module.  The final communication from Tom Baldwin was that
> the three colors for IFs A and C were not connected in the
> correct order.  They corrected this.  After a Modcomp failure
> and much travail I was finally able to get the system working
> again to discover that 24C still does the samething.  Tomorrow
> I suggest returning the DTs module to the bench for examination.
>
> Rick made another survey of L band performance across the band
> which he will report on separately.
>
> The reminder of SW time will be used to try to measure interband
> collimations in a systematic way.
>
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>
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