[time-nuts] Re: GPS failed

[JC]

Google 'GPS testing notices'


On Mon, Jul 11, 2022 at 1:15 PM jeanmichel.friedt--- via time-nuts <
time-nuts at lists.febo.com> wrote:

> for what it's worth ... the UK gov. is nice enough to warn about GPS
> jamming
> exercises
> https://www.ofcom.org.uk/spectrum/information/gps-jamming-exercises
> not sure about the US of A announcements on such activities. At least in
> France
> I have never seen such warnings.
>
> Best, JM
>
> --
> JM Friedt, FEMTO-ST Time & Frequency, 26 rue de l'Epitaphe, 25000
> Besancon, France
>
> July 11, 2022 7:42 PM, "Bob kb8tq via time-nuts" <time-nuts at lists.febo.com>
> wrote:
>
> > Hi
> >
> > Are all the receivers the same type / model? If so what are they?
> Various
> > receivers made over the last 20 years have some “issues” that can pop
> up.
> >
> > Is the antenna gain properly matched to the needs of the receiver? Some
> > are designed for a “target gain” of 20 db, others 30, some 50. Match a
> > 20 db receiver with a 50 db antenna …. you have issues.
> >
> > Are all the hilltops in common view of each other? Somebody jamming their
> > ankle bracelet could be the simple answer if they are ….
> >
> > Just what overloads this or that receiver often is a bit obscure. Most
> are pretty
> > good at taking out CW tones. It often takes something a bit more complex
> > to drive them insane. This makes testing a bit exciting.
> >
> > Lots of strange and weird possibilities.
> >
> > Bob
> >
> >> On Jul 10, 2022, at 3:19 PM, skipp Isaham via time-nuts <
> time-nuts at lists.febo.com> 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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