[time-nuts] Re: GPS failed

[Bob kb8tq]

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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