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]> 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]> 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, 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