I'd doubt it's a choke-plate design - too small, and it looks like other Cheap dual-element designs I've seen come out of China. I don't agree with sparkfun's recommendation of using the cheapest Chinese adapters you can buy to get a decent SWR/insertion-loss. What's notably missing in the datasheet besides a clean translation - is data and specifications. Frequency range is quoted as "GPS L1/L1 + GLONASS L1/L2" rather than actually giving a numerical frequency range. There is also the statement: "...equipped with anti-multi-path choke plate, with anti-surge design, can effectively suppress the out-of-band strong interference signal to ensure the reliability of the antenna..." As someone who has occasion to wade through Chinese sales pitches for sneaking their way into well known product families through untrained corporate buyers, this appears to be what I will coin the phrase "pseudo keyword soup". There's just enough somewhat familiar key-word sounding terms in that sentence to suggest: 1) that this is a choke ring, not a "ground plane independent antenna" (what it appears they have actually designed) 2) that it has surge suppression, and that surge suppression is acting as an adjacent band filter (I seriously doubt that) * If it was a choke ring, I expect to see an elevation number for multi-path rejection, as well as plots - and horizontal dimensions (diameter) >10" for single L1 and >12" for dual band L1/L2. * If it has surge suppression, I'd expect to see what surge model they were suppressing * If it had out of band filtering, I'd expect to see cutoffs and dB numbers... Those bullets above would be features a savvy GPS antenna buyer would be looking for, and it's easy to forget to read and verify the performance numbers are actually "good". As an example, this antenna ( https://www.tallysman.com/product/tw3882-dual-band-gnss-antenna/) from a Canadian company has about the same keyword-soup equivalent terms, except the specs are, for lack of a better term IMHO "more reputable" and verifiable. I picked up a few of these a few months back for the car tracking project, with white colored radomes and Type-N male bulkhead connector mounts - about $300/each. Notable, they have a typical antenna axial ratio 1/3 of the Sparkfun antenna, with a max value of 1/2 the Sparkfun part (and it is called out as flat across the whole band), have 5db less of LNA amplification - but at half the current draw (and specifically the LNA performance is invariant from 2.5-16VDC), and specifically the ESD is rated for 15kV of air discharge - the VSWR is better, and they have actual out of band rejection numbers (with good minimum rejection of >30dB, many comon radio types like cellular are >40dB rejection) - and they give the specific bandwidth of each band. It is however not ground plane independent (but my use is vehicular, so not a problem) - but without the ground plane, it's less than half the size of the Sparkfun part, and the recommended non-roof ground plane is 100mm (~2" smaller diameter than the Sparkfun part). You get what you pay for IMHO - while interesting, the Sparkfun part comes across as a puppy trying to get away with playing with wolves, and hoping the other wolves don't notice it's food. Your mileage may vary though. -Tim S On Fri, Nov 13, 2020 at 7:56 PM <time-nuts-request@lists.febo.com> wrote: > From: Robert LaJeunesse <lajeunesse@mail.com> > To: time-nuts@lists.febo.com > Subject: Re: [time-nuts] L1/L2 survey antenna $125 new > Message-ID: > > <trinity-ef99ff3c-a78e-44a5-8ab9-c357610d106c-1605321572235@3c-app-mailcom-lxa15 > > > > Content-Type: text/plain; charset=UTF-8 > > Dana, no plans to buy. Just put up my L1 antenna last weekend. > > Bob L. > > > Sent: Friday, November 13, 2020 at 7:26 PM > > From: "Dana Whitlow" <k8yumdoober@gmail.com> > > To: "Discussion of precise time and frequency measurement" < > time-nuts@lists.febo.com> > > Subject: Re: [time-nuts] L1/L2 survey antenna $125 new > > > > I quote the description on the SparKfun page via the WIndows clipboard: > > > > "Note: This antenna has a TNC Male RP connector found on nearly all > > surveying antennas. We recommend a TNC Male RP to SMA adapter > > < > https://www.amazon.com/DGZZI-2-Pack-Coaxial-Adapter-Connector/dp/B06ZZGGWBS > > > > or > > cable when using with our GNSS receivers." > > > > But the photo on the site appears to show a receptacle, not a pin, for > the > > center conductor, hence > > a standard female configuration. So unless the thread is left-handed, > > which I really can't tell, > > this is a standard (not RP)* female* connector. That's my story and I'm > > sticking to it! > > > > Bob, are you by chance thinking of buying one of these? If so, please > let > > us know which it > > is right away when it arrives. > > > > Dana > > > > > > On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse <lajeunesse@mail.com> > > wrote: > > > > > Just spotted this: https://www.sparkfun.com/products/17382 > > > > > > Datasheet: > > > > https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_GNSS_Antenna_Datasheet.pdf > > > > > > Chokeplate design, 40dB LNA, TNC connector > > > >

I agree with Tim. Adding to that - if someone pitches a *surveying* antenna - antenna calibration data must be easily found on a “well known” antenna calibration database. Or at least supplied by the manufacturer in a meaningful format. https://www.ngs.noaa.gov/GRD/GPS/DOC/page4/antcal.html http://www.geopp.com/pdf/gppigs06_pabs_g.pdf /Björn Sent from my iPhone > On 14 Nov 2020, at 08:12, Tim S <tim.strommen@gmail.com> wrote: > > I'd doubt it's a choke-plate design - too small, and it looks like > other Cheap dual-element designs I've seen come out of China. I don't > agree with sparkfun's recommendation of using the cheapest Chinese adapters > you can buy to get a decent SWR/insertion-loss. > > What's notably missing in the datasheet besides a clean translation - is > data and specifications. > > Frequency range is quoted as "GPS L1/L1 + GLONASS L1/L2" rather than > actually giving a numerical frequency range. There is also the statement: > "...equipped with anti-multi-path choke plate, with anti-surge design, can > effectively suppress the out-of-band strong interference signal to ensure > the reliability of the antenna..." > > As someone who has occasion to wade through Chinese sales pitches for > sneaking their way into well known product families through untrained > corporate buyers, this appears to be what I will coin the phrase "pseudo > keyword soup". There's just enough somewhat familiar key-word sounding > terms in that sentence to suggest: > 1) that this is a choke ring, not a "ground plane independent antenna" > (what it appears they have actually designed) > 2) that it has surge suppression, and that surge suppression is acting as > an adjacent band filter (I seriously doubt that) > > * If it was a choke ring, I expect to see an elevation number for > multi-path rejection, as well as plots - and horizontal dimensions > (diameter) >10" for single L1 and >12" for dual band L1/L2. > * If it has surge suppression, I'd expect to see what surge model they were > suppressing > * If it had out of band filtering, I'd expect to see cutoffs and dB > numbers... > > Those bullets above would be features a savvy GPS antenna buyer would be > looking for, and it's easy to forget to read and verify the performance > numbers are actually "good". > > As an example, this antenna ( > https://www.tallysman.com/product/tw3882-dual-band-gnss-antenna/) from a > Canadian company has about the same keyword-soup equivalent terms, except > the specs are, for lack of a better term IMHO "more reputable" and > verifiable. I picked up a few of these a few months back for the car > tracking project, with white colored radomes and Type-N male bulkhead > connector mounts - about $300/each. > > Notable, they have a typical antenna axial ratio 1/3 of the Sparkfun > antenna, with a max value of 1/2 the Sparkfun part (and it is called out as > flat across the whole band), have 5db less of LNA amplification - but at > half the current draw (and specifically the LNA performance is invariant > from 2.5-16VDC), and specifically the ESD is rated for 15kV of air > discharge - the VSWR is better, and they have actual out of band rejection > numbers (with good minimum rejection of >30dB, many comon radio types like > cellular are >40dB rejection) - and they give the specific bandwidth of > each band. It is however not ground plane independent (but my use is > vehicular, so not a problem) - but without the ground plane, it's less than > half the size of the Sparkfun part, and the recommended non-roof ground > plane is 100mm (~2" smaller diameter than the Sparkfun part). > > You get what you pay for IMHO - while interesting, the Sparkfun part comes > across as a puppy trying to get away with playing with wolves, and hoping > the other wolves don't notice it's food. Your mileage may vary though. > > -Tim S > > >> On Fri, Nov 13, 2020 at 7:56 PM <time-nuts-request@lists.febo.com> wrote: >> >> From: Robert LaJeunesse <lajeunesse@mail.com> >> To: time-nuts@lists.febo.com >> Subject: Re: [time-nuts] L1/L2 survey antenna $125 new >> Message-ID: >> >> <trinity-ef99ff3c-a78e-44a5-8ab9-c357610d106c-1605321572235@3c-app-mailcom-lxa15 >>> >> >> Content-Type: text/plain; charset=UTF-8 >> >> Dana, no plans to buy. Just put up my L1 antenna last weekend. >> >> Bob L. >> >>> Sent: Friday, November 13, 2020 at 7:26 PM >>> From: "Dana Whitlow" <k8yumdoober@gmail.com> >>> To: "Discussion of precise time and frequency measurement" < >> time-nuts@lists.febo.com> >>> Subject: Re: [time-nuts] L1/L2 survey antenna $125 new >>> >>> I quote the description on the SparKfun page via the WIndows clipboard: >>> >>> "Note: This antenna has a TNC Male RP connector found on nearly all >>> surveying antennas. We recommend a TNC Male RP to SMA adapter >>> < >> https://www.amazon.com/DGZZI-2-Pack-Coaxial-Adapter-Connector/dp/B06ZZGGWBS >>> >>> or >>> cable when using with our GNSS receivers." >>> >>> But the photo on the site appears to show a receptacle, not a pin, for >> the >>> center conductor, hence >>> a standard female configuration. So unless the thread is left-handed, >>> which I really can't tell, >>> this is a standard (not RP)* female* connector. That's my story and I'm >>> sticking to it! >>> >>> Bob, are you by chance thinking of buying one of these? If so, please >> let >>> us know which it >>> is right away when it arrives. >>> >>> Dana >>> >>> >>> On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse <lajeunesse@mail.com> >>> wrote: >>> >>>> Just spotted this: https://www.sparkfun.com/products/17382 >>>> >>>> Datasheet: >>>> >> https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_GNSS_Antenna_Datasheet.pdf >>>> >>>> Chokeplate design, 40dB LNA, TNC connector >>>> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.