[evlatests] New (?) X-band RFI

[Mert]

Hi Rick.  There is a passive-only band between 10.680 and 10.700 GHz, but
10.7-12.7 GHz is all fixed microwave (terrestrial point-to-point) and
space-to-earth satellite transmissions.  We (RA) do have some footnoted
protections there, but only to the extent that their transmissions might
affect the 10.680 and 10.700 GHz band.  Those are the "hooks" that Harvey
Liszt has been using to try to prevent RFI from the new SpaceX StarLink
broadband internet service from being too disruptive to RA.

I know that there are some fixed microwave systems in the area in the "11
GHz band", but I'd have to check on the exact frequencies.  Otherwise I'd
say that you are seeing standard GSO satellite transponders.  (StarLink is
non-GSO, so we could only be sure of a StarLink detection if we see the
source away from Dec 0.  GSO downlinks have been in the 10.7-12.7 GHz
band, like, forever.  30-40 MHz bandwidth per transponder channel sounds
likely.)  -Mert


> In a recent run, some strong RFI, seen only short spacings only (due to
fringe-winding and A config) was seen between:
> 10.950 and 11.190 GHz.
> The spectral characteristics show these to be in 6 spectral 'chunks',
each 40 MHz wide.
> The RFI was not seen on the (northern) calibrator, but was obvious on
the target source, located at Dec = -5.5  So, likely a geostationary
satellite.
> @Dan:  Any idea what's responsible?
> Rick
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