[time-nuts] Re: GPS failed

[Scott McGrath]

I’m going to bring up jamming here as 1) i live directly under a military air route.  2) a local OTR  trucker brings regularly scheduled jamming when he leaves/arrives home.

Your client could also be in proximity to a ‘prepper’ who is running a GPS jammer to prevent ‘three letter agencies’ from tracking them.   Or a trucker doing the same and forgetting to shut down their jammer.   GPS jammers are available ‘under the counter’ at virtually every truck stop in the US.

Yes it’s highly illegal and disrespectful of other system users and in the prepper case will eventually attract the attention of those very authorities they wished to avoid.

A reasonable way to check for jamming is the FAA ADS-B system.   if a ADS-B outage exists in same area and time as client sees GPS failure Client is likely to be experiencing jamming as ADS-B utilizes onboard GPS receivers to report aircraft position using a transmitter at   1090MHz in real time instead of depending on ATC radar to trigger a transponder.

Link to the FAA ADS-B outage system below 

https://sapt.faa.gov/outages.php?outageType=129001450&outageResolution=0.5





Content by Scott
Typos by Siri

On Jul 12, 2022, at 3:20 AM, Matthias Welwarsky via time-nuts <time-nuts at lists.febo.com> wrote:

Hi,

if you're worried about in-band interference, the 23cm HAM radio band is 
reasonably close to the L1 GPS frequency. When I was still active in packet 
radio back in the days, our digipeater DB0DAR lost an interlink due to 
interference with a precision GPS receiver in use by another university 
institute. We had to shut it down. I think they operated a DGPS site at the 
time and our link traffic caused errors in the correction data. Or something.

BR,
Matthias

On Montag, 11. Juli 2022 01:19:18 CEST skipp Isaham via time-nuts wrote:
> Hello to the Group,
> 
> I'd like to get some opinions and war stories regarding GPS reliability at
> high RF level and elevation locations.
> 
> Background:  Three different hill-top GPS receivers, all different types,
> using different antennas mounted on an outside fixiture, plain view of the
> open sky, all stopped working.
> 
> Test antennas were brought in and placed on a fixture well away from the
> original antennas, the recevers went back in to capture and lock.
> 
> From what I understand, the original antennas are what I would call straight
> preamp with no pre-selection / filtering.
> 
> The ordered and now inbound replacements are said to contain a SAW filter
> system. It is the intent of the client to just place these "improved
> antennas" in to service and get on with life.
> 
> I would suspect a GPS antenna (and receiver) could be subject to RF overload
> or blocking, however, we're assuming nothing major has changed at the site,
> nor any nearby location.  One might think there are more GPS receivers
> being pushed out of reliable operation by the world around them, I'm just
> not hearing those stories from a lot of people using them (GPS receivers).
> 
> Any new install GPS receiver antenna ordered will/should contain some
> pre-selection to potentially avoid a problem, even some years down the
> road? Seems like that's where things are going... no more off the shelf,
> wide band, (hot) preamplified GPS antennas in busy locations?
> 
> Thank you in advance for any related comments and/or opions ...
> 
> cheers,
> 
> skipp
> 
> skipp025 at jah who dot calm
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