Or find an Arra “level set” variable attenuator. 3844 and 3854 models can often be found cheaply, have dc-pass and attenuate at both L1 and L2.
/Björn Sent from my iPhone > On 2 Apr 2018, at 03:43, David C. Partridge <[email protected]> > wrote: > > just use a bias tee to feed in the antenna volts :) > > -----Original Message----- > From: time-nuts [mailto:[email protected]] On Behalf Of Azelio > Boriani > Sent: 01 April 2018 23:29 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS ANTENNA > > An unusual attenuator with a DC pass. > >> On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge >> <[email protected]> wrote: >> Or use a choke ring survey antenna and an attenuator :) >> >> Dave >> >> -----Original Message----- >> From: time-nuts [mailto:[email protected]] On Behalf Of Bob >> kb8tq >> Sent: 01 April 2018 14:43 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS ANTENNA >> >> Hi >> >> Indeed, it is *very* easy to put to much gain in front of a timing GNSS >> receiver. These beasts are trying to dig out a signal that you can’t even >> see with a spectrum analyzer. >> It’s way to far below the noise floor to detect that way. They optimize >> things pretty tightly to get that done (and to hit a price target ….). Put >> to much gain in front of them and they get unhappy. >> >> Making this even more crazy, the survey industry standard antenna *does* >> have a lot of gain. Survey receivers need way more gain in front of them >> than timing receivers. Put a survey antenna directly on a timing device and >> trouble will likely be the outcome. Equally, a survey instrument probably >> will not be happy with a timing receiver. >> >> Why all this nonsense? As far as I can tell, it goes back to how the very >> early L1 / L2 survey boxes were designed back in the 1980’s and early >> 1990’s. They made a basic decision to put a lot of gain at the antenna. >> Motorola came along with their GPS modules later on. They made a *very* >> different decision about how to distribute the gain. There are very good >> arguments on both sides for why they did it this way. >> The bottom line is still - you need to match things up … >> >> Bob >> >>> On Apr 1, 2018, at 2:36 AM, cfo <[email protected]> wrote: >>> >>> On Sat, 31 Mar 2018 10:58:19 -0500, >>> donandarline-Re5JQEeQqe8AvxtiuMwx3w >>> wrote: >>> >>>> I found a supplier for high quality GPS antennas at a very >>>> reasonable price. PCTEL GPSL1-TMG-SPI-40NCB. >>> >>> *** SNIP *** >>> >>> I had one of those on 25m cable, and it worked fine on a Tbolt , >>> until i got an active antenna splitter that also had some gain. >>> Then i had to replace it w. a 26dB version of same type, else the >>> "Jackson Lite" was loosing sync. >>> >>> What i mean here, is that you can get too much gain too. >>> >>> Btw: Good price. >>> >>> CFO >>> Denmark >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
