[evlatests] New (?) X-band RFI

[Rob Long]

The 40 MHz BW (chunks) sounds like typical comm downlink transponders 
and like was said, if you know where we were on the arc, we can probably 
figure out which satellite you were seeing.

Rob

On 1/26/2021 1:35 PM, rperley via evlatests wrote:
> I'll get you this in a few moments ...
>
> On 2021-01-26 15:26, Steven Myers via evlatests wrote:
>> 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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