On 4/1/18 3:29 PM, Azelio Boriani wrote:
An unusual attenuator with a DC pass.
A few feet of RG-174 (or any 0.1" diameter coax) would probably work.
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
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