[evlatests] S9 switch vs. splitter

[Emmanuel Momjian]

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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listmgr.nrao.edu/pipermail/evlatests/attachments/20241204/b6582b6d/attachment.html>