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>