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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