Don't forget that the Satellite TV system in the building AND the Forecast Office's TV wall have broadband amplifiers in many IDFs in the building. Check with Kyle Keys and Ken Brown on this.
From: Gerry Creager <[log in to unmask]<mailto:[log in to unmask]>>
Reply-To: OU Amateur Radio Club <[log in to unmask]<mailto:[log in to unmask]>>
Date: Wednesday, November 7, 2012 11:20 AM
To: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>>
Subject: Re: Fwd: Fwd: GPS Interference
My first thought is that there's something nearby with a flyin' TV
preamp. Those can become effective broadband noise generators. I've
seen this before. If it's on a motor home or RV, it's likely only
powered when someone' s watching TV. If they sit down to watch the
afternoon soaps... well, you know.
The analyzer I'm gonna bring back is a lot more portable than mine
(mine's similar to a Zenith portable TV: weighs a ton, and has 2
handles. The one coming back is better.
gerry
On Wed, Nov 7, 2012 at 11:10 AM, Kim Elmore <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Of course, in cases of intentional GPS denial the source wants to avoid
being found because, once found, it is very shortly afterward "neutralized."
How portable is your spectrum analyzer? Info about no apparent interference
during approaches is good -- it has to be local. Curious that it's only in
the afternoon, though. It also has to be pretty close by and likely
unintentional. Something has gone bad; just a matter for finding it.
73,
Kim N5OP
On 11/7/2012 10:53 AM, Gerry Creager wrote:
I think I'll be bringing back a good spectrum analyzer and antenna
set, and I know (I hope!) where my lab-grade GPS preamp is. We can
snoop on Monday. Finding these is an interesting exercise and even the
military has trouble finding 'em. That's one of the problems with
combatting GPS denial in the real world.
gerry
On Wed, Nov 7, 2012 at 10:47 AM, Kim Elmore <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Agreed: this has to be L1. I'll bet the military has ways to find stuff like
this. We don't necessarily want them to "neutralize" it, only find it. For
the past several days, I've noticed that my automotive GPS says it's lots
satellite lock when I leave from work, but is fine otherwise. I initially
suspected interference, but also wondered if it was a hardware issue. It's
clearly interference.
GPS signal levels are quite low, so finding the source with a spectrum
analyzer and good yagi should make for a straightforward fox hunt. All we
need is the spectrum analyzer. We need the spectrum analyzer because a
narrow-band receiver isn't helpful if the source is broadband. There must be
at least one available to us via OU's EE department or possibly the ARRC
lab. There also have to be hams around that have them -- we simply need to
find one that's willing and able to help.
73,
Kim N5OP
On 11/7/2012 10:18 AM, Gerry Creager wrote:
Or a harmonic from, e.g., a television broadband preamp. I have seen
interference from those, although usually at other frequencies, a
number of times. And I concur, this has to be an L1 interference
problem. While it could be within the 20 MHz primary passband, I
strongly suspect broadband rather than carrier noise.
73 gerry
On Wed, Nov 7, 2012 at 10:07 AM, Peter Laws <[log in to unmask]<mailto:[log in to unmask]>> wrote:
They don't use the military "P-code", so it's the L1 frequency, 1575.42 MHz
that is being affected. Anything +/- 50 MHz or so would be suspect. Could
be a spur from an IF on something using a higher frequency, too.
On 11/07/12 09:50, Zac Flamig wrote:
Just in case any of you guys know something...
Zac
-------- Original Message --------
Subject: Fwd: GPS Interference
Date: Wed, 07 Nov 2012 05:33:35 -0600
From: Bob Staples <[log in to unmask]<mailto:[log in to unmask]>>
To: [log in to unmask]<mailto:[log in to unmask]>
Please note the email from Forest Mitchell ( WFO) and advice me of anyone
you know or that may be conducting experiments that would interfere with
the GPS signal ?
Thanks,
Bob D Staples
-------- Original Message --------
Subject: GPS Interference
Date: Wed, 07 Nov 2012 04:20:17 -0600
From: Forrest Mitchell <[log in to unmask]<mailto:[log in to unmask]>>
To: Bob Staples <[log in to unmask]<mailto:[log in to unmask]>>
CC: David Andra <[log in to unmask]<mailto:[log in to unmask]>>, [log in to unmask]<mailto:[log in to unmask]>,
[log in to unmask]<mailto:[log in to unmask]>, John Pike <[log in to unmask]<mailto:[log in to unmask]>>, Daryl Williams
<[log in to unmask]<mailto:[log in to unmask]>>, Doug Speheger <[log in to unmask]<mailto:[log in to unmask]>>, Rick
Smith <[log in to unmask]<mailto:[log in to unmask]>>
In the past week, we have been experiencing interference with acquiring
a GPS signal for the radiosondes we launch for Upper Air flights. The
GPS signal is critical towards acquiring accurate wind data aloft.
The interference is centered around the NWC, as measured by coworkers
using a variety of GPS devices. The interference occurs during the
afternoons, affecting us
during our launch window from 5-6:30 pm. It then disappears around 7
pm. There is no interference during the morning flights.
Is there some experiment being performed by someone within the NWS
community that could be causing the interference? We would appreciate
your efforts to find the source
so that we may create a solution to allow us to perform our mission in
its entirety. Thank you.
--
Peter Laws / N5UWY
National Weather Center / Network Operations Center
University of Oklahoma Information Technology
[log in to unmask]<mailto:[log in to unmask]>
College of Architecture, Regional and City Planning, MRCP '16
--------------------------------------------------------------------------
Feedback? Contact my director, Matt Younkins, [log in to unmask]<mailto:[log in to unmask]>. Thank you!
--
Kim Elmore, Ph.D. (CCM, PP SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph,
GROL)
“People that make music together cannot be enemies, at least while the music
lasts." – Paul Hindemith
--
Kim Elmore, Ph.D. (CCM, PP SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph,
GROL)
“People that make music together cannot be enemies, at least while the music
lasts." – Paul Hindemith
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