Now that is obsessive!!
:-))
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Dr Bruce Griffiths
Sent: 12 March 2007 22:39
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier
] Delay through GPS antenna splitter/amplifier -- an
answer, and a question
So the cable delay should be a multiple of 317.375...ps.
What's the thermal coefficient of coax?
Typically around 50-100ppm/C depending on the coax.
High velocity cables have lower tempcos
Handwaving...
100 ft of cable
I had a chance recently to look at the performance of the two-port and
eight-port HP GPS antenna splitters on a super-duper network analyzer.
Screenshots of the results are at
http://www.febo.com/time-freq/pages/gps-splitter.
In short, the minimum delay (at the center of the passband) from
of microsecond region it
isn't worth worrying about.
Rob K
- Original Message -
From: John Ackermann N8UR [EMAIL PROTECTED]
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Monday, March 12, 2007 3:03 PM
Subject: [time-nuts] Delay through GPS antenna
measurement
time-nuts@febo.com
Sent: Monday, March 12, 2007 3:03 PM
Subject: [time-nuts] Delay through GPS antenna splitter/amplifier -- an
answer, and a question
I had a chance recently to look at the performance of the two-port and
eight-port HP GPS antenna splitters on a super-duper
In message: [EMAIL PROTECTED]
Rob Kimberley [EMAIL PROTECTED] writes:
: From my experience, your position and hence derived time is based on the
: antenna centre. Cable, splitter, connector, and antenna filter delays all
: need to be taken into account when looking at very accurate
From: John Ackermann N8UR [EMAIL PROTECTED]
Subject: [time-nuts] Delay through GPS antenna splitter/amplifier -- an answer,
and a question
Date: Mon, 12 Mar 2007 11:03:12 -0400
Message-ID: [EMAIL PROTECTED]
John,
I had a chance recently to look at the performance of the two-port and
eight
I had a chance recently to look at the performance of the two-port and
eight-port HP GPS antenna splitters on a super-duper network analyzer.
Screenshots of the results are at
http://www.febo.com/time-freq/pages/gps-splitter.
Super nice plots, John.
Tom Clark, do you have comments?
John,
From: John Ackermann N8UR [EMAIL PROTECTED]
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- an
answer, and a question
Date: Mon, 12 Mar 2007 12:04:06 -0400
Message-ID: [EMAIL PROTECTED]
But we're time-nuts... we DO worry about those things. :-)
Indeed!
Oh my goodness
Tom Van Baak wrote:
John, next time you can borrow that instrument blow
some hot/cool air on the antenna and see what changes
and by how much.
I've heard that the older GPS antennas, the ones with zero
or less RF filtering, were much better for timing applications
but have never seen data
Magnus Danielson wrote:
I would use TDR/TDT for that. :)
My buddy the expert tells me that using frequency sweep rather than
pulse techniques is preferred these days. With multi-GHz sweeps, you
can get better resolution, and you also minimize the problems that
strong external signals can
From: John Ackermann N8UR [EMAIL PROTECTED]
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- an
answer, and a question
Date: Mon, 12 Mar 2007 13:17:50 -0400
Message-ID: [EMAIL PROTECTED]
Magnus Danielson wrote:
I would use TDR/TDT for that. :)
My buddy the expert
[EMAIL PROTECTED]
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Monday, March 12, 2007 3:03 PM
Subject: [time-nuts] Delay through GPS antenna splitter/amplifier --
an answer, and a question
I had a chance recently to look at the performance of the two-port
In short, yes. If you want true traceability to NIST, you need to take
into account UTC(GPS) versus UTC(NIST).
And it gets uglier yet. If you want UTC you have to take
into account the UTC - UTC(NIST) delta, which was about
16 ns in January. See the full 2006 record:
Just a swag, it's probably reasonable to assume that each stage of
filtering adds about 10ns of delay.
That should be reasonable to measure.
Setup a system without the splitter/filter/whatever, and use that to
calibrate a local reference clock. Then insert the unit you want to test and
K
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of John Ackermann N8UR
Sent: 12 March 2007 16:51
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- an
answer, and a question
In message: [EMAIL PROTECTED]
Magnus Danielson [EMAIL PROTECTED] writes:
: Oh my goodness, the PPS is 10 ps late due to unmatched cable-lag! What should
I
: do? (For the egg-clock in the kitchen)
Put a tiny kink in the cable. That should be good for an offset of
that magnitude.
is that a really tiny or maybe a medium tiny or are we talking a pico kink
(which is also smaller than a nano kink)???
i needed a smile for today as my time is up.
tom [EMAIL PROTECTED]
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Tim Shoppa wrote:
John Ackermann N8UR [EMAIL PROTECTED] wrote:
But we're time-nuts... we DO worry about those things. :-)
While we were at it with the network analyzer, we did FDR (frequency
domain reflectometry) to measure the cable delay to the antenna, and I
spent yesterday making
Dr Bruce Griffiths [EMAIL PROTECTED] wrote:
At the lab I worked at in the 80's, all the cables hanging on
the wall-racks were calibrated and labeled in nanoseconds.
But... after the ECL signals got turned into TTL, we just didn't
care anymore :-).
Your not quite obsessive enough.
The
Tim Shoppa wrote:
Dr Bruce Griffiths [EMAIL PROTECTED] wrote:
At the lab I worked at in the 80's, all the cables hanging on
the wall-racks were calibrated and labeled in nanoseconds.
But... after the ECL signals got turned into TTL, we just didn't
care anymore :-).
Your not
So the cable delay should be a multiple of 317.375...ps.
What's the thermal coefficient of coax?
--
These are my opinions, not necessarily my employer's. I hate spam.
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time-nuts mailing list
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One is much better to take the filter's delay in
account rather than NOT USING a filter!!! i can hardly
imagine a GPS receiver/antenna without any form of
preselection, and, unfortunately, they're many of
those filterless units on the market!
73 de Normand VE2UM
Montreal, Qc. Canada
--- John
So the cable delay should be a multiple of 317.375...ps.
What's the thermal coefficient of coax?
Typically around 50-100ppm/C depending on the coax.
High velocity cables have lower tempcos
Handwaving...
100 ft of cable is 70ns or 7ps.
100ppm is 7ps.
10C is 70ps.
So if you start out
Hal Murray wrote:
So the cable delay should be a multiple of 317.375...ps.
What's the thermal coefficient of coax?
Typically around 50-100ppm/C depending on the coax.
High velocity cables have lower tempcos
Handwaving...
100 ft of cable is 70ns or 7ps.
100ppm
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