Discussion:
GPS ANTENNA
(too old to reply)
d***@gmail.com
2018-03-31 15:58:19 UTC
Permalink
I found a supplier for high quality GPS antennas at a very reasonable price.
PCTEL GPSL1-TMG-SPI-40NCB.
They have other ones too.
I bought one and it works great.
New in the box, never opened.
The only thing wrong was the 4 base mounting screws were too short (no big deal).
They are on Ebay # 282851759313.
$48.00 shipped.
Thanks,
Don W9BHI

Sent from Mail for Windows 10

_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
cfo
2018-04-01 06:36:27 UTC
Permalink
On Sat, 31 Mar 2018 10:58:19 -0500, donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob kb8tq
2018-04-01 13:42:47 UTC
Permalink
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500, donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
David C. Partridge
2018-04-01 20:21:04 UTC
Permalink
Or use a choke ring survey antenna and an attenuator :)

Dave

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@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-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Azelio Boriani
2018-04-01 22:29:24 UTC
Permalink
An unusual attenuator with a DC pass.

On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
jimlux
2018-04-02 00:11:35 UTC
Permalink
Post by Azelio Boriani
An unusual attenuator with a DC pass.
A few feet of RG-174 (or any 0.1" diameter coax) would probably work.
Post by Azelio Boriani
On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob kb8tq
2018-04-02 00:16:57 UTC
Permalink
Hi

They are indeed a bit unusual. Generally you do a DC block and bias tee ahead of the
attenuator. For a “self contained” approach, a second block and bias tee pulls the DC
of the GPSDO side of the attenuator. My preference has been to just run the bias tee
with an external DC source.

Bob
Post by Azelio Boriani
An unusual attenuator with a DC pass.
On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bruce Griffiths
2018-04-02 01:21:28 UTC
Permalink
Just use a standard attenuator between a pair of bias T's with their dc ports connected together.

Bruce
Post by Azelio Boriani
An unusual attenuator with a DC pass.
On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
David C. Partridge
2018-04-02 01:43:24 UTC
Permalink
just use a bias tee to feed in the antenna volts :)

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] 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.
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@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-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Björn
2018-04-02 07:32:35 UTC
Permalink
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
Post by David C. Partridge
just use a bias tee to feed in the antenna volts :)
-----Original Message-----
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.
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob kb8tq
2018-04-02 13:26:06 UTC
Permalink
Hi

As you rummage around your junk box, do be a bit careful Most of what I have here are
tee’s that include DC blocks. There are blocks that don’t do that. Trying to run your bias
supply into 50 or 25 ohms is not a real good idea.

Bob
Post by David C. Partridge
just use a bias tee to feed in the antenna volts :)
-----Original Message-----
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.
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
ew via time-nuts
2018-04-02 10:07:39 UTC
Permalink
Question
Using L/H  what is too much signal 
Bert Kehren
 
In a message dated 4/1/2018 10:54:23 PM Eastern Standard Time, ***@perdrix.co.uk writes:

 
just use a bias tee to feed in the antenna volts :)

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] 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.
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@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-***@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-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob kb8tq
2018-04-02 14:01:40 UTC
Permalink
Hi

The problem with “to much gain” is that it is very hard to tell when you have to much gain.
The system quite happily chugs along reporting fine S/N ratios. Cut the gain by 20 db and
you get the same C/N ratios. The reason is pretty simple - the noise figure is set by the
front end of the preamp. As long as you have “enough” gain it will dominate. Is “enough”
10 db or 100 db? Either way it’s enough to make that equation work.

The issue comes in mainly because these modules have a limited AGC range (or dynamic
range). For whatever reason, the AGC situation is not reported upstream. If the module has
run out of AGC and is about to loose it …. you simply have no way to tell.

It’s not just TimeNuts that have trouble with this stuff. Very large / smart / big budget / outfits
run into this stuff as well. The same issues of poorly documented system requirements /
non-standard system requirements are a major hassle for them. I’ve seen them spend
major effort because of this stuff.

So how to work it out?

Stuff a (dc blocked) variable attenuator in the line. Pick a sat that is reporting something like
35 db S/N. Flip between two attenuator settings every 30 seconds or so. Note any change.
Do it multiple times with multiple sats. Then move on to your next settings pair. I’d start big,
maybe a 10 db step and go smaller if you can stand the boredom.

As long as 35 db stays roughly 35 db, you have “enough” gain. Since sat’s move and that
impacts S/N, there is no exact 0.05 db sort of number. Even looking at numbers over a day
can be tricky. Things are never quite the same today as they were yesterday.

It does seem strange that you want the minimum gain. It’s not so strange if you dig into things
like land mobile radio design. Your best overload performance is always going to be the
design with barely enough gain in the front end.

Lots of fun.

Bob
Post by ew via time-nuts
Question
Using L/H what is too much signal
Bert Kehren
just use a bias tee to feed in the antenna volts :)
-----Original Message-----
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.
Post by David C. Partridge
Or use a choke ring survey antenna and an attenuator :)
Dave
-----Original Message-----
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
Post by cfo
On Sat, 31 Mar 2018 10:58:19 -0500,
donandarline-Re5JQEeQqe8AvxtiuMwx3w
Post by d***@gmail.com
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
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Loading...