[evlatests] Antenna 14 FRM interference

[Bryan Butler]

it's not really possible to do this without hand-editing the scripts. 
i'll talk to ken about how to modify our standard 4-band scripts to do 
it (it's not trivial there either, but can be done).

i recognize it's a stop-gap to do that, and hopefully you guys are 
working on the real solution.

	-bryan


Frank Schinzel wrote on 6/3/16 10:20 :
> Hi Dan,
>
> On 06/03/2016 10:06 AM, Dan Mertely wrote:
>> Hi Frank.  Thanks for the investigation.
>>
>> I'm a bit confused.  In the AC14_FRM_on.ps plot the strong (RFI?)
>> signals at 54.75 &  77.4 MHz are > 100.  On the AC14_FRM_on_zoom.ps
>> plot the same signals are < 20.  Shouldn't they be the same amplitude
>> & just go off the scale (since you zoomed in on the vertical scale)?
>>
>
> I think those points got chopped off its exactly the same data that is
> plotted just limiting the values to between 0 and 20. It might not draw
> a line between points when there is more than one point outside of that
> range. You can see that in IF6, that is most affected, there are only a
> few scattered points with no line drawn through.
>
>> We are familiar with the problem and probable cause.  One (very
>> temporary) solution is to set-up the scripts to (or to have the Op
>> manually) turn off the FRM during the data collection portion of
>> observing.  This would only be for the purpose of allowing 4m
>> testing to continue until the problem is fixed.  Is that possible?
>> -Mert
>>
> That is probably a question for Bryan. Is there a scripted way to be
> able to turn the FRM power off for antenna 14? Currently, somebody has
> to actively login to the antenna 14 ACU and manually turn off and back
> on the FrmPwr. This makes dynamic scheduling of 4-band observations
> without this interference impossible, unless we can script this in
> somewhere.
>
>     Frank
>
>>
>>
>>
>>
>> On 6/2/2016 4:31 PM, Frank Schinzel wrote:
>>> Hi everyone,
>>>
>>> We did today a test today to verify the extend of the FRM interference
>>> from antenna 14 at 4 band. We observed Cas A at low elevation with the
>>> antennas facing West. We did one 5 min scan with the FRM off and another
>>> one with the FRM on. The interference clearly shows up. What surprised
>>> me the most is that cross-correlation products in IF6 show this as
>>> correlated interference present across the entire B array (see attached
>>> config.pdf).
>>>
>>> For your enjoyment I have made comparison plots across the band for XY
>>> auto-correlations of antenna 14 (AC14_FRM_off.pdf, AC14_FRM_on.pdf, and
>>> AC14_FRM_on_zoom.pdf).
>>>
>>> I also added an example of two cross-correlation plots with FRM on and
>>> off just showing IF6 XY (XC_FRM_off.ps and XC_FRM_on.ps). Those are for
>>> two baselines one between 14 and the neighboring antenna 23 and one
>>> where I didn't see strong interference in the cross-correlation between
>>> antennas 14 and 22.
>>>
>>> It would be great if we could address this issue in the near future
>>> before we take some more 4-band data.
>>>
>>>       Frank
>>>
>>>
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>
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