[evlatests] New Broadband RFI in X-band found

[Dan Mertely]

Hi Rick.  Although it is possible that this is a satellite,
there are a large number (dozens) of point-to-point microwave
links around the area in this frequency range.  Although the
directionality you found doesn't match, I would consider the
most likely offender the GoGo, LLC link we negotiated that
runs from Pie Town up to Davenport peak just NW of Datil.
Those links probably overshoot onto the north arm (+ scatter).

The links are at:
10975.0/36 MHz, (10957-10993) @ +55.9 dBm
11055.0/36 MHz, (11037-11073) @ +55.9 dBm

They seem to cover the frequency range you described, and are
pointed at us.  We negotiated with GoGo a couple of years ago
to move up to the 11 GHz region in order to avoid their planned
6 GHz link from Davenport.  They use the link to connect in to
the Western NM Tele fiber access point in PT from their RX/TX
site on Davenport.  Davenport is one of their upward-looking cell
phone base stations that provide WiFi service to commercial
aircraft (downlinked in the 950 MHz band).  We even negotiated
very precisely on the frequencies in order to avoid the X2 falling
in our H2O allocation in K-band.

If the pointing is definitively to the south, there are still
quite a large number of 10900-11200 MHz links to our south,
although most are at the southern end of the Gila, near Silver
City & Pinos Altos (from which we get a lot of mountain blockage).
I would then consider them more likely culprits than a satellite.

The more common frequency for satellite downlinks in "Ku" band is
11.7-12.2 GHz, which is above the RFI you noted.  (The "fixed"
satellite service allocation in Ku does extend down to 10.7 GHz
though.)  We'll try some sweeps with our azimuth scanning DF
system as well, & I'll send an update if we find anything.

-Mert


Rick Perley wrote:
>     A previously unknown (to me) broadband RFI source has been found in 
> the 'flux densities' data for X-band. 
> 
>     This one covers the range 10952 through 11200 MHz.  It is only seen 
> on southern sources -- and in only a minority of these.  I suspect a 
> geosynchronous origin, perhaps just a single satellite. 
> 
>     Dan -- can you uncover the origin of this one? 
> 
> 
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