Or use a choke ring survey antenna and an attenuator :) Dave
-----Original Message----- From: time-nuts [mailto:time-nuts-boun...@febo.com] 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 <xne...@luna.dyndns.dk> 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 -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
