[time-nuts] Re: GPS failed

[Björn via time-nuts]

Sent from my Phone

> On 13 Jul 2022, at 02:34, Bob kb8tq via time-nuts  
> wrote:
> 
> Hi
> 
> The “typical” Symmetricom cone shaped GPS antennas are targeted at 
> cell phone tower applications. Being mounted on the same structure
> as multiple cell transmitters puts them in a significant RF environment. 
> They have a *lot* of filtering built into the antenna to try to prevent 
> overload
> issues. 
> 
> As with a lot of things, Symmetricom simply rebrands antennas made by
> others. Not all cone shaped antennas are identical. However it’s a pretty
> good bet that most of them are very similar to what Symmetericom ( and
> the other folks ) supply for cell applications. 
> 
> The “other end” of the range are the multi band saucer shaped “survey” 
> antennas. They tend to have a lot less filtering and be more focused at 
> allowing the user to access a wide range of frequencies ( both GNSS and
> supplemental services) via a single device. Lots of filtering also tends to 
> mess up delay here or there, that’s not a great thing for high precision 
> work. 
> 
> Bob
>> 

Bob,

That was true 10-15 years ago. Good quality surveying antennas often has quite 
decent filtering on each band they are designed for. 

/Björn 
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[time-nuts] Re: GPS failed

[Mark Spencer via time-nuts]

Thanks Bob.

I believe this is what I have (I would need to climb up on the roof to double 
check the part number (assuming the label is still legible..))

https://www.microsemi.com/document-portal/doc_view/133381-58532a-datasheet

Best regards
Mark Spencer

Sent from Mail for Windows

From: Bob kb8tq
Sent: July 12, 2022 11:19 AM
To: Discussion of precise time and frequency 
measurement
Cc: Mark Spencer
Subject: Re: [time-nuts] GPS failed

Hi

The “typical” Symmetricom cone shaped GPS antennas are targeted at
cell phone tower applications. Being mounted on the same structure
as multiple cell transmitters puts them in a significant RF environment.
They have a *lot* of filtering built into the antenna to try to prevent overload
issues.

As with a lot of things, Symmetricom simply rebrands antennas made by
others. Not all cone shaped antennas are identical. However it’s a pretty
good bet that most of them are very similar to what Symmetericom ( and
the other folks ) supply for cell applications.

The “other end” of the range are the multi band saucer shaped “survey”
antennas. They tend to have a lot less filtering and be more focused at
allowing the user to access a wide range of frequencies ( both GNSS and
supplemental services) via a single device. Lots of filtering also tends to
mess up delay here or there, that’s not a great thing for high precision
work.

Bob

> On Jul 12, 2022, at 9:39 AM, Mark Spencer via time-nuts 
>  wrote:
>
> For what it is worth...
>
> I have a commercial grade ( Symmetricom ?) GPS antenna on the roof of my 
> home.  I don't recall ever having any issues with GPS reception despite 
> having / had various other transmit / receive antennas on the roof for 
> various frequencies from 1.8 MHz thru 1.3 GHz.  Power levels on some bands 
> (not including 1.2 GHz thru 1.3 GHz where I have never exceeded approx 10 
> watts) can equal or occasionally exceed 100 watts.
>
> As far as I know all my GPS receivers are using the typical 1.5 GHz GPS band.
>
> As usual the experiences of others may differ from mine.
>
> Best regards
> Mark Spencer
>
>> On Jul 12, 2022, at 12:08 AM, Matthias Welwarsky via time-nuts 
>>  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
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe send an email to time-nuts-le...@lists.febo.com
>>
>>
>>
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>>
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[time-nuts] Re: GPS failed

[Bob kb8tq via time-nuts]

Hi

The “typical” Symmetricom cone shaped GPS antennas are targeted at 
cell phone tower applications. Being mounted on the same structure
as multiple cell transmitters puts them in a significant RF environment. 
They have a *lot* of filtering built into the antenna to try to prevent overload
issues. 

As with a lot of things, Symmetricom simply rebrands antennas made by
others. Not all cone shaped antennas are identical. However it’s a pretty
good bet that most of them are very similar to what Symmetericom ( and
the other folks ) supply for cell applications. 

The “other end” of the range are the multi band saucer shaped “survey” 
antennas. They tend to have a lot less filtering and be more focused at 
allowing the user to access a wide range of frequencies ( both GNSS and
supplemental services) via a single device. Lots of filtering also tends to 
mess up delay here or there, that’s not a great thing for high precision 
work. 

Bob

> On Jul 12, 2022, at 9:39 AM, Mark Spencer via time-nuts 
>  wrote:
> 
> For what it is worth...
> 
> I have a commercial grade ( Symmetricom ?) GPS antenna on the roof of my 
> home.  I don't recall ever having any issues with GPS reception despite 
> having / had various other transmit / receive antennas on the roof for 
> various frequencies from 1.8 MHz thru 1.3 GHz.  Power levels on some bands 
> (not including 1.2 GHz thru 1.3 GHz where I have never exceeded approx 10 
> watts) can equal or occasionally exceed 100 watts.
> 
> As far as I know all my GPS receivers are using the typical 1.5 GHz GPS band.
> 
> As usual the experiences of others may differ from mine.
> 
> Best regards 
> Mark Spencer
> 
>> On Jul 12, 2022, at 12:08 AM, Matthias Welwarsky via time-nuts 
>>  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
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe send an email to time-nuts-le...@lists.febo.com
>> 
>> 
>> 
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[time-nuts] Re: GPS failed

[Mark Spencer via time-nuts]

For what it is worth...

 I have a commercial grade ( Symmetricom ?) GPS antenna on the roof of my home. 
 I don't recall ever having any issues with GPS reception despite having / had 
various other transmit / receive antennas on the roof for various frequencies 
from 1.8 MHz thru 1.3 GHz.  Power levels on some bands (not including 1.2 GHz 
thru 1.3 GHz where I have never exceeded approx 10 watts) can equal or 
occasionally exceed 100 watts.

As far as I know all my GPS receivers are using the typical 1.5 GHz GPS band.

As usual the experiences of others may differ from mine.

Best regards 
Mark Spencer

> On Jul 12, 2022, at 12:08 AM, Matthias Welwarsky via time-nuts 
>  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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> 
> 
> 
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[time-nuts] Re: GPS failed

[John Sloan via time-nuts]

> I'd like to get some opinions and war stories regarding GPS reliability at 
> high RF level and elevation locations. 

At last count I’ve got ten GPS/GNSS active antennas scattered around the
house (I have a very understanding spousal unit), including one in the
kitchen skylight and one outside. We are currently in a sunspot cycle, and
this summer has been an unusually active season. Several times I’ve seen
one or more of my systems fail, sometimes for a couple of days at a time.

I subscribe to the NOAA Space Weather Prediction Center alert system.

https://www.swpc.noaa.gov/communities/space-weather-enthusiasts

Inevitably about the time I’m thinking about swapping an antenna to see if
it fixes the problem, I get an alert from the SWPC warning about a major
coronal mass ejection event.

I’ve finally learning to check the SWPC web site first before messing with
hardware. I’ve also learned to check the systems before sunrise (I’m an
early riser anyway) and after sunset.

In each case the systems effected came back to working order without my
having to do anything. Some antennas - regardless of location - seem to
be affected more than others.

(Why so many antennas? Five of them are GPS-disciplined NTP servers. Two
of them are part of a little NTP/GPS monitoring system I built. Two are
part of a Differential GNSS test bed I run 24x7. And one is just the test
antenna to my work bench for whatever I’m working on.)

- John

--
J. L. Sloan Digital Aggregates Corporation
+1.303.489.5178 3440 Youngfield Street
mailto:jsl...@diag.com  #209
http://www.diag.com Wheat Ridge CO 80033 USA




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[time-nuts] Re: GPS failed

[Björn via time-nuts]

Hi Matthias,

There has been interference reported and resolved between 23cm and Galileo, 
which have signals in the 23cm band. 

/Björn 

Sent from my Phone

> On 12 Jul 2022, at 09:20, Matthias Welwarsky via time-nuts 
>  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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>> To unsubscribe send an email to time-nuts-le...@lists.febo.com
> 
> 
> 
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[time-nuts] Re: GPS failed

[Scott McGrath via time-nuts]

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=0.5





Content by Scott
Typos by Siri

On Jul 12, 2022, at 3:20 AM, Matthias Welwarsky via time-nuts 
 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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[time-nuts] Re: GPS failed

[Matthias Welwarsky via time-nuts]

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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> To unsubscribe send an email to time-nuts-le...@lists.febo.com



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[time-nuts] Re: GPS failed

[Bob kb8tq via time-nuts]

Hi

These days there are folks who make a living tracking down interference
sources in the vicinity of ports and airports on a contract basis. Many of
the issues are navigation related. Some of it is GPS. Some is other stuff 
( like 5 GHz WiFI and radar …)

Bob

> On Jul 11, 2022, at 1:28 PM, Oz-in-DFW via time-nuts 
>  wrote:
> 
> On 7/11/2022 8:43 AM, Andy Talbot via time-nuts wrote:
>> I also heard a case of a GPS antenna going unstable, oscillating and taking
>> out most of the boats in a marina.
> There have also been several cases of cheap active TV antennas doing the same 
> thing. There was a case 10 or more years ago that shut down an LA marina and 
> the Port of Long Beach for several days until it was located.
> 
> Oz (in DFW, Texas near the airport)
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[time-nuts] Re: GPS failed

[Hal Murray via time-nuts]

Andy Talbot said:
> I also heard a case of a GPS antenna going unstable, oscillating and taking
> out most of the boats in a marina.   The Radio Communications Agency (as our
> enforcement body was then, before it became Ofcom) had to be called out to
> identify the problem. 

There was an interesting story about a similar event in GPS World back in Jan 
2003
This was from TV antenna amplifiers that were oscillating in/near the GPS band.
It/they took out the Moss Landing (Monterey Bay) harbor.

The Hunt for RFI
  http://gpsworld.com/the-hunt-rfi/
Unjamming a Coast Harbor
James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul 
McGill, Richard W. Adler


-- 
These are my opinions.  I hate spam.


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[time-nuts] Re: GPS failed

[Brian Lloyd via time-nuts]

On 7/11/22 12:48, jeanmichel.friedt--- via time-nuts 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.


Yes, they do. Still, it is annoying to be piloting an aircraft in 
instrument conditions and have GPS go away. When it has happened usually 
I am prepared to switch back to VOR navigation.


--


 

Brian Lloyd
706 Flightline
Spring Branch, TX 78070
br...@lloyd.aero 
+1.210.620.0011
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[time-nuts] Re: GPS failed

[Oz-in-DFW via time-nuts]

On 7/11/2022 8:43 AM, Andy Talbot via time-nuts wrote:

I also heard a case of a GPS antenna going unstable, oscillating and taking
out most of the boats in a marina.
There have also been several cases of cheap active TV antennas doing the 
same thing. There was a case 10 or more years ago that shut down an LA 
marina and the Port of Long Beach for several days until it was located.


Oz (in DFW, Texas near the airport)
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[time-nuts] Re: GPS failed

[JC via time-nuts]

Google 'GPS testing notices'


On Mon, Jul 11, 2022 at 1:15 PM jeanmichel.friedt--- via time-nuts <
time-nuts@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" 
> 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@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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> >
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[time-nuts] Re: GPS failed

[jeanmichel.friedt--- via time-nuts]

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"  
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 
>>  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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> 
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[time-nuts] Re: GPS failed

[Bob kb8tq via time-nuts]

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 
>  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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[time-nuts] Re: GPS failed

[Carsten Andrich via time-nuts]

The u-blox SAW filtering is great. We've carried out various RF 
measurements with +40 dBm EIRP at 2.53 and 3.75 GHz with some u-blox 
ANN-MB within <2m of the Tx antennas. While we haven't conducted 
in-depth comparisons with a superior ground-truth, my current conclusion 
is that the u-blox RTK performance is not (noticeably) affected by 
strong out-of-band emissions. Without extensive filtering the Tx power 
would likely steamroll any LNA/receiver. Of course, as John pointed out, 
this won't help against in-band interference.


Best regards,
Carsten

On 11.07.22 15:16, John Ackermann via time-nuts wrote:

Hi Skipp -- there is a lot of info about interference mitigation in the u-blox 
integration manual for the ZED--F9T (available under the docs at 
https://www.u-blox.com/en/product/zed-f9t-module).  It might give you some 
clues, and I think might also point to another u-blox app note on the topic.

Most of the antennas I've seen that have an LNA also include a SAW filter.  I 
also once found on either Amazon or eBay so e new-product, relatively 
inexpensive, high pass filters with cutoff around 1 GHz.  Those would help 
knock down broadcast, trunking, etc. stuff.  (But of course nothing will help 
with on-frequency crud coming from outside the GPS system.)

John

On Jul 11, 2022, 8:49 AM, at 8:49 AM, 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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[time-nuts] Re: GPS failed

[David G. McGaw via time-nuts]

With the new 5G hardware, we are seeing all manner of new interference, 
some of it quite broad-band.  A good antenna with sharp SAW filter may 
help, but not if the emmisions are in-band. Besides broad-band, there 
also can be 2nd harmonic emissions that cause interference.  We had this 
problem with an Iridium ground station (just above the GPS L1 frequency) 
for scientific balloon data that had a new cell installation placed 
nearby.  We had (and thankfully were able to) have the cell base station 
shut down while we were flying.


73,

David N1HAC

On 7/11/22 9:27 AM, paul swed via time-nuts wrote:

Skipp
I am aware at least in the US that there is the possibility of 5G
interference along with newer possible bands that 5G can use. I have read
several articles in a publication called GNSS.


Thats why I am using wwvb at 60 KHz. Humor intended.
Regards
Paul
WB8TSL

On Mon, Jul 11, 2022 at 8:49 AM skipp Isaham via time-nuts <
time-nuts@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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[time-nuts] Re: GPS failed

[Andy Talbot via time-nuts]

There is a 3G/4G Supplementary Downlink allocation at 1492MHz in some
countries.   Close enough to cause problems.

Andy
www.g4jnt.com



On Mon, 11 Jul 2022 at 14:40, paul swed via time-nuts <
time-nuts@lists.febo.com> wrote:

> Skipp
> I am aware at least in the US that there is the possibility of 5G
> interference along with newer possible bands that 5G can use. I have read
> several articles in a publication called GNSS.
>
>
> Thats why I am using wwvb at 60 KHz. Humor intended.
> Regards
> Paul
> WB8TSL
>
> On Mon, Jul 11, 2022 at 8:49 AM skipp Isaham via time-nuts <
> time-nuts@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@lists.febo.com
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> >
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[time-nuts] Re: GPS failed

[Andy Talbot via time-nuts]

I have had one, and possibly two, low cost active antennas  go unstable and
start oscillating.  These are the  magnetic car mount type with a ceramic
patch antenna.   The ceramic patch has quite a high Q and determines the
frequency the unstable RF front end takes off at - which is obviously at
1575.42 plus / minus a few tens of kHz.   Needless to say, all local GPS
receivers are jammed

I also heard a case of a GPS antenna going unstable, oscillating and taking
out most of the boats in a marina.   The Radio Communications Agency (as
our enforcement body was then, before it became Ofcom) had to be called
out to identify the problem.

Andy
www.g4jnt.com



On Mon, 11 Jul 2022 at 14:37, Lux, Jim via time-nuts <
time-nuts@lists.febo.com> wrote:

> On 7/10/22 4:19 PM, 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).
>
> yes, this happens.  We used to have a Pendulum timing receiver with a
> typical "small white cone" type amplified antenna - if someone was on
> the roof with a cellphone, it lost lock, presumably from the (way out of
> band) emissions.
>
>
> As to where the interfering source is - it doesn't take much, and it
> could be some distance away.  After all, this was the big deal with
> LightSquared - it was moderately high powered terrestrial broadcast
> transmitters in the satellite downlink band next to GNSS.
>
>
> >
> > 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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> > To unsubscribe send an email to time-nuts-le...@lists.febo.com
> >
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[time-nuts] Re: GPS failed

[paul swed via time-nuts]

Skipp
I am aware at least in the US that there is the possibility of 5G
interference along with newer possible bands that 5G can use. I have read
several articles in a publication called GNSS.


Thats why I am using wwvb at 60 KHz. Humor intended.
Regards
Paul
WB8TSL

On Mon, Jul 11, 2022 at 8:49 AM skipp Isaham via time-nuts <
time-nuts@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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[time-nuts] Re: GPS failed

[Lux, Jim via time-nuts]

On 7/10/22 4:19 PM, 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).


yes, this happens.  We used to have a Pendulum timing receiver with a 
typical "small white cone" type amplified antenna - if someone was on 
the roof with a cellphone, it lost lock, presumably from the (way out of 
band) emissions.



As to where the interfering source is - it doesn't take much, and it 
could be some distance away.  After all, this was the big deal with 
LightSquared - it was moderately high powered terrestrial broadcast 
transmitters in the satellite downlink band next to GNSS.





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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[time-nuts] Re: GPS failed

[Chris Caudle via time-nuts]

On Sun, July 10, 2022 6:19 pm, skipp Isaham via time-nuts wrote:
> 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.

Did you test the original antennas in a different environment to see if
they still work at all?  Perhaps the amplifier in the antenna housing
failed on the original three antenna.

> 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.

If you are implying that you think the antenna are still working, but
cannot handle the RF environment at that location which is what caused the
GPS failure, I would be dubious.  You said hilltop location, so my first
suspicion would be damage to the antenna induced by a nearby lightning
strike.

>  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).

Spectrum allocation is controlled reasonably tightly.  If there were
widespread problems due to increased EMI then you would know relatively
quickly from the number of people using GPS every day.

-- 
Chris Caudle

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[time-nuts] Re: GPS failed

[John Ackermann via time-nuts]

Hi Skipp -- there is a lot of info about interference mitigation in the u-blox 
integration manual for the ZED--F9T (available under the docs at 
https://www.u-blox.com/en/product/zed-f9t-module).  It might give you some 
clues, and I think might also point to another u-blox app note on the topic.

Most of the antennas I've seen that have an LNA also include a SAW filter.  I 
also once found on either Amazon or eBay so e new-product, relatively 
inexpensive, high pass filters with cutoff around 1 GHz.  Those would help 
knock down broadcast, trunking, etc. stuff.  (But of course nothing will help 
with on-frequency crud coming from outside the GPS system.)

John

On Jul 11, 2022, 8:49 AM, at 8:49 AM, 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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[time-nuts] Re: GPS failed

[Tom Holmes via time-nuts]

Hey Skipp!
A couple of thoughts…
Why do you need an amplified antenna in a high and open spot, unless the coax 
run is longer than about 40’?
Is it practical to move one of the existing antennas away from the current 
location as a test to see if it’s a failure vs overload? Assuming it is 
physically practical to do so, of course. 

From Tom Holmes, N8ZM

> On Jul 11, 2022, at 8:49 AM, 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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