[evlatests] S9 switch vs. splitter

[Dave Parker]

Thank you for the input.

Dave

On 12/4/2024 4:39 PM, Emmanuel Momjian via evlatests wrote:
>
> Recently*, the S9 switches on the output of the L301-2 in four 
> antennas (ea02, ea08, ea14, and ea17) were replaced with splitters. To 
> evaluate if this would have any impact on astronomical data, several 
> RFI sweeps were acquired.
>
> The evaluation of the data, before and after the modifications, as 
> well as with and without the antennas in question, did not show any 
> noticeable issues in the spectra (e.g., no new strong birdies due to 
> the LO frequencies and/or their harmonics).
>
> It is worth noting that of the tunings used in the RFI sweep, the only 
> time the L301-2 output frequency, or one of its first two harmonics, 
> falls within the recorded observing band is at 12160 MHz. This 
> frequency does show a strong narrow-band birdie, ~20 dB above the 
> noise floor.  However, this signal was already present before the 
> splitter modification and does not appear to have changed 
> significantly in strength after the modification was done.
>
> If you happen to see any new strong birdies in any of your recent VLA 
> data, please let us know asap.
>
> Emmanuel and Paul
>
> *ea08’s S9 switch was replaced with the splitter on or around Nov. 21, 
> 2024. The work on the other three antennas was done on Nov. 25, 2024.
>
>
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