That's good information and supports the idea of a low-power signal.
Also, though, your antenna is atop the aircraft, and regardless, being
airborne, you get a view of more satellites (most of the time!).

Thanks, Chip!
gerry

On Wed, Nov 7, 2012 at 10:52 AM, Legett, Carey IV <[log in to unmask]> wrote:
> For what it's worth, we're not experiencing any problems with the GPS
> approaches to the airport. One passes a mile or two west of NWC at about
> 1500ft.
> -Chip, WX9EMT
>
> On Nov 7, 2012, at 10:47, "Kim Elmore" <[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]> 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]>
> To:     [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]>
> To:     Bob Staples <[log in to unmask]>
> CC:     David Andra <[log in to unmask]>, [log in to unmask],
> [log in to unmask], John Pike <[log in to unmask]>, Daryl Williams
> <[log in to unmask]>, Doug Speheger <[log in to unmask]>, Rick
> Smith <[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]
> College of Architecture, Regional and City Planning, MRCP '16
> --------------------------------------------------------------------------
> Feedback? Contact my director, Matt Younkins, [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.vcf>