[time-nuts] Re: GPS failed

[jeanmichel.friedt at femto-st.fr]

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
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com