[FedCom] New antennas on the Secret Service suburban

[lora & david]

About 6 months ago the US Coast Guard published a warning for boats equipped
with GPS and radio shack and certain other amplified TV antennas. Seems the
receive preamp radiates in the GPS spectrum and can cause GPS navigation
errors.
David
----- Original Message -----
From: "Dave Emery" <die at dieconsulting.com>
To: <lists at lazygranch.com>; <fedcom at mailman.qth.net>
Sent: Sunday, August 08, 2004 11:42 PM
Subject: Re: [FedCom] New antennas on the Secret Service suburban


> On Sun, Aug 08, 2004 at 10:09:36PM -0700, gary wrote:
> > Unless they can localize the jamming, I just don't see how it could be
> > done without a notam. Airports have GPS approach patterns these days.
>
> I'm inclined to agree, it completely surprised me that there
> would any chance of deliberately jamming such a vital service, used not
> just for aircraft navigation but lots other uses including AVL systems
> for tracking emergency vehicles and cell site time and frequency control
> and many other critical uses.
>
> And there well may have been other explanations - what I
> experianced is just an unexplained behavior of a device in my lab, a
> behavior I have only noticed earlier when the antenna  connector came
> loose (that wasn't the problem this time though).
>
> I did not attempt to use other instrumentation (such as a
> spectrum analyzer) to try to diagnose the cause of the anomaly, I was
> too busy following the  convention on TV and listening to convention
> related radio traffic.   It was just something I noticed in passing
> and fiddled with for a few minutes to see if the thing had gone belly
> up for some reason.
>
> IF the problem was caused by RFI I'd actually be more
> inclined to guess that it might be strong signals (presumably in
> L band somewhere) on OTHER than GPS 1575.42 mhz frequency that were
> causing problems for my receiver (overload) than actually something
> jamming GPS (especially for the whole Boston area).
>
> Civilian GPS receivers don't have all that tight rf preselection
> so a strong signal nearby might have made the thing fail...  and that
> incidently, might also explain GPS failure during POTUS visits
> as well.
>
> And I frankly cannot entirely rule out interference from some
> radio or another I had running at the time - I have observed that
> certain scanners (RS 2006s amoung others) radiate enough local oscillator
> signal in L band that if you tune them to the right frequency they
> will jam nearby GPS receivers.   The antenna for my GPS standard is
> some distance away on the rooftop above my lab/shack but it is possible
> there could have been a problem.
>
>
>
> --
>    Dave Emery N1PRE,  die at dieconsulting.com  DIE Consulting, Weston, Mass
02493
>
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