[evlatests] New (?) X-band RFI

[Steven Myers]

If GEO, array pointing will have moved ~2deg in 10min. Would need to know the LST and/or AZ/EL of event to identify satellite.

> On Jan 26, 2021, at 9:29 AM, rperley via evlatests <evlatests at listmgr.nrao.edu> wrote:
> 
> Dan, et al.:
> 
> Looking at more data, it's clear the RFI is from a rapidly moving object.  The duration of the RFI is only 10 minutes or so, after which, all appears close to normal.
> 
> Another thing I noted:  The same RFI is seen at a higher frequency -- 11.46 to 11.82 GHz.  It's clear that these signals are also broadband, and 'blocked' in frequency in a similar manner to that reported earlier, between 10.95 and 11.19 GHz.  The time correlation is exact -- all of these rise and fall in precisely the same way.  They must have the same origin.
> 
> Curiously, the frequency span from 11.19 to 11.46 is completely clean.
> 
> Rick
> 
> On 2021-01-26 11:19, Mert wrote:
>> 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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