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