Empathy List Archives

MS

Mark Sims

Sun, Apr 2, 2017 5:34 PM

I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable.

My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps.

BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools.

Some “cables” have very long delay numbers.

I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable. My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps. BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools. -------------------- > Some “cables” have very long delay numbers.

BG

Bruce Griffiths

Mon, Apr 3, 2017 3:05 AM

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes.

Bruce

 On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote:

 I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable.

 My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps.

 BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools.

 --------------------

     Some “cables” have very long delay numbers.

     _______________________________________________
     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.

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes. Bruce > > On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote: > > I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable. > > My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps. > > BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools. > > -------------------- > > > > > > Some “cables” have very long delay numbers. > > > > _______________________________________________ > > 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. > > > > >

MS

Mark Sims

Mon, Apr 3, 2017 3:55 AM

I could use the 1PPS output of a crappy GPS receiver. Should have at least 30 ns of jitter. Or for finer, but still noisy, the PPS from the Venus timing receiver is around 6 ns. I'd need at least 100 feet of PTFE coax to get it out the door and back inside with enough cable outside to make a difference. Alas, I have none.

Or I could do it all indoors and set the air conditioning to around 20C and let that cycle the temperature. Or put the cable in the freezer and monitor it while it warms up... hmmm... that sounds fun and easy to do.

I've been pretty amazed by what a TICC can do for $200... I wonder how a GPX chip based one would perform?
I used the TICC to dial in my HP-5065 freq to around 1E-12. I had not adjusted it for a couple of years and it was around 1-E11 off.

From: Bruce Griffiths bruce.griffiths@xtra.co.nz
Sent: Monday, April 3, 2017 3:05 AM
To: Mark Sims; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] TAPR TICC boxed

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes.

Bruce

On 03 April 2017 at 05:34 Mark Sims holrum@hotmail.com wrote:

I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable.

My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps.

BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools.

Some “cables” have very long delay numbers.

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.

I could use the 1PPS output of a crappy GPS receiver. Should have at least 30 ns of jitter. Or for finer, but still noisy, the PPS from the Venus timing receiver is around 6 ns. I'd need at least 100 feet of PTFE coax to get it out the door and back inside with enough cable outside to make a difference. Alas, I have none. Or I could do it all indoors and set the air conditioning to around 20C and let that cycle the temperature. Or put the cable in the freezer and monitor it while it warms up... hmmm... that sounds fun and easy to do. I've been pretty amazed by what a TICC can do for $200... I wonder how a GPX chip based one would perform? I used the TICC to dial in my HP-5065 freq to around 1E-12. I had not adjusted it for a couple of years and it was around 1-E11 off. ________________________________________ From: Bruce Griffiths <bruce.griffiths@xtra.co.nz> Sent: Monday, April 3, 2017 3:05 AM To: Mark Sims; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] TAPR TICC boxed For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes. Bruce On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote: I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable. My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps. BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools. -------------------- Some “cables” have very long delay numbers. _______________________________________________ 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.

AK

Attila Kinali

Mon, Apr 3, 2017 9:22 AM

On Mon, 3 Apr 2017 15:05:55 +1200 (NZST)
Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

This will require several 100 meters of cable to be measureable with
the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase
stable cables reach even <1ppm/K. Measuring a change of 10ppm with
a resolution of 60ps means that the delay has to be in the order of 6µs,
which is close to 1000m of cable. Even if dithering gives another facor
of 10, this still means 100m of cable.

For this level of comparison I would suggest to use a sinusoidal signal,
instead of a pulse, and do phase comparison, which gives a resolution
in the order of 1ps with very little effort, thus reducing the required
cable length to 10-20 meters.

		Attila Kinali

[1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011
http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

On Mon, 3 Apr 2017 15:05:55 +1200 (NZST) Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. This will require several 100 meters of cable to be measureable with the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase stable cables reach even <1ppm/K. Measuring a change of 10ppm with a resolution of 60ps means that the delay has to be in the order of 6µs, which is close to 1000m of cable. Even if dithering gives another facor of 10, this still means 100m of cable. For this level of comparison I would suggest to use a sinusoidal signal, instead of a pulse, and do phase comparison, which gives a resolution in the order of 1ps with very little effort, thus reducing the required cable length to 10-20 meters. Attila Kinali [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011 http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson

BC

Bob Camp

Mon, Apr 3, 2017 11:20 AM

Hi

You could simply immerse all the cables in a swimming pool full of mercury … :)
(bonus points for a link to the prior discussion of that topic ..).

Bob

On Apr 2, 2017, at 11:05 PM, Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes.

Bruce

On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote:

I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable.

My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps.

BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools.

--------------------

    Some “cables” have very long delay numbers.

    _______________________________________________
    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.

Hi You could simply immerse all the cables in a swimming pool full of mercury … :) (bonus points for a link to the prior discussion of that topic ..). Bob > On Apr 2, 2017, at 11:05 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. > > A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes. > > Bruce > >> >> On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote: >> >> I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable. >> >> My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps. >> >> BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools. >> >> -------------------- >> >>>> >>> Some “cables” have very long delay numbers. >>> >>> _______________________________________________ >>> 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.

BG

Bruce Griffiths

Mon, Apr 3, 2017 12:13 PM

Copper jacketed low density PTFE insulated coax cables typically exhibit a net phase change of over 1000ppm during the PTFE phase transition. See figure 2 p14 of the Cables and connectors supplement to March 2017 microwave journal. Solid PTFE insulated cables exhibit an even greater (2 -3x) phase change. to achieve a phase shift tempco of 10ppm/C either hermetically selaed silicon dioxide powder insulated coax or "phase tracking" semirigid or better phase tracking flexible coax is required.

Bruce

 On 03 April 2017 at 21:22 Attila Kinali <attila@kinali.ch> wrote:

 On Mon, 3 Apr 2017 15:05:55 +1200 (NZST)
 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote:

     For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

 This will require several 100 meters of cable to be measureable with
 the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase
 stable cables reach even <1ppm/K. Measuring a change of 10ppm with
 a resolution of 60ps means that the delay has to be in the order of 6µs,
 which is close to 1000m of cable. Even if dithering gives another facor
 of 10, this still means 100m of cable.

 For this level of comparison I would suggest to use a sinusoidal signal,
 instead of a pulse, and do phase comparison, which gives a resolution
 in the order of 1ps with very little effort, thus reducing the required
 cable length to 10-20 meters.

 Attila Kinali

 [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011
 http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf

 --
 It is upon moral qualities that a society is ultimately founded. All
 the prosperity and technological sophistication in the world is of no
 use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson

 _______________________________________________
 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.

Copper jacketed low density PTFE insulated coax cables typically exhibit a net phase change of over 1000ppm during the PTFE phase transition. See figure 2 p14 of the Cables and connectors supplement to March 2017 microwave journal. Solid PTFE insulated cables exhibit an even greater (2 -3x) phase change. to achieve a phase shift tempco of 10ppm/C either hermetically selaed silicon dioxide powder insulated coax or "phase tracking" semirigid or better phase tracking flexible coax is required. Bruce > > On 03 April 2017 at 21:22 Attila Kinali <attila@kinali.ch> wrote: > > On Mon, 3 Apr 2017 15:05:55 +1200 (NZST) > Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > > > > > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. > > > > > > This will require several 100 meters of cable to be measureable with > the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase > stable cables reach even <1ppm/K. Measuring a change of 10ppm with > a resolution of 60ps means that the delay has to be in the order of 6µs, > which is close to 1000m of cable. Even if dithering gives another facor > of 10, this still means 100m of cable. > > For this level of comparison I would suggest to use a sinusoidal signal, > instead of a pulse, and do phase comparison, which gives a resolution > in the order of 1ps with very little effort, thus reducing the required > cable length to 10-20 meters. > > Attila Kinali > > [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011 > http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > > _______________________________________________ > 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. >

BG

Bruce Griffiths

Tue, Apr 4, 2017 11:23 AM

http://www.spacetechexpo.eu/assets/files/2015/Recent-Developments-in-Phase-Stable-Cables.pdf

is a more readily accessible source of data on coax cable delay tempco et.

Bruce

 On 04 April 2017 at 00:13 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote:

 Copper jacketed low density PTFE insulated coax cables typically exhibit a net phase change of over 1000ppm during the PTFE phase transition. See figure 2 p14 of the Cables and connectors supplement to March 2017 microwave journal. Solid PTFE insulated cables exhibit an even greater (2 -3x) phase change. to achieve a phase shift tempco of 10ppm/C either hermetically selaed silicon dioxide powder insulated coax or "phase tracking" semirigid or better phase tracking flexible coax is required.

 Bruce

     On 03 April 2017 at 21:22 Attila Kinali <attila@kinali.ch> wrote:

     On Mon, 3 Apr 2017 15:05:55 +1200 (NZST)
     Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote:

             For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

             This will require several 100 meters of cable to be measureable with
             the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase
             stable cables reach even <1ppm/K. Measuring a change of 10ppm with
             a resolution of 60ps means that the delay has to be in the order of 6µs,
             which is close to 1000m of cable. Even if dithering gives another facor
             of 10, this still means 100m of cable.

     For this level of comparison I would suggest to use a sinusoidal signal,
     instead of a pulse, and do phase comparison, which gives a resolution
     in the order of 1ps with very little effort, thus reducing the required
     cable length to 10-20 meters.

     Attila Kinali

     [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011
     http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf

     --
     It is upon moral qualities that a society is ultimately founded. All
     the prosperity and technological sophistication in the world is of no
     use without that foundation.
     -- Miss Matheson, The Diamond Age, Neil Stephenson

     _______________________________________________
     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.

http://www.spacetechexpo.eu/assets/files/2015/Recent-Developments-in-Phase-Stable-Cables.pdf is a more readily accessible source of data on coax cable delay tempco et. Bruce > > On 04 April 2017 at 00:13 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > Copper jacketed low density PTFE insulated coax cables typically exhibit a net phase change of over 1000ppm during the PTFE phase transition. See figure 2 p14 of the Cables and connectors supplement to March 2017 microwave journal. Solid PTFE insulated cables exhibit an even greater (2 -3x) phase change. to achieve a phase shift tempco of 10ppm/C either hermetically selaed silicon dioxide powder insulated coax or "phase tracking" semirigid or better phase tracking flexible coax is required. > > Bruce > > > > > > On 03 April 2017 at 21:22 Attila Kinali <attila@kinali.ch> wrote: > > > > On Mon, 3 Apr 2017 15:05:55 +1200 (NZST) > > Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > > > > > > > > > > > > > > > > > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. > > > > > > > > This will require several 100 meters of cable to be measureable with > > > > the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase > > > > stable cables reach even <1ppm/K. Measuring a change of 10ppm with > > > > a resolution of 60ps means that the delay has to be in the order of 6µs, > > > > which is close to 1000m of cable. Even if dithering gives another facor > > > > of 10, this still means 100m of cable. > > > > > > > > > > > > > > > > > > For this level of comparison I would suggest to use a sinusoidal signal, > > instead of a pulse, and do phase comparison, which gives a resolution > > in the order of 1ps with very little effort, thus reducing the required > > cable length to 10-20 meters. > > > > Attila Kinali > > > > [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011 > > http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf > > > > -- > > It is upon moral qualities that a society is ultimately founded. All > > the prosperity and technological sophistication in the world is of no > > use without that foundation. > > -- Miss Matheson, The Diamond Age, Neil Stephenson > > > > _______________________________________________ > > 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. > > > > >

BG

Bruce Griffiths

Wed, Apr 5, 2017 6:21 AM

The gold standard is a random pulse source.
Using something like a SPAD as the source of random pulses is popular as the average rate can be easily adjusted by changing the light level. It also avoids using radioactive sources.

Bruce

On 03 April 2017 at 15:05 Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:

For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.

A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes.

Bruce

 On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote:

 I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable.

 My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps.

 BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools.

 --------------------

     Some “cables” have very long delay numbers.

     _______________________________________________
     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.

The gold standard is a random pulse source. Using something like a SPAD as the source of random pulses is popular as the average rate can be easily adjusted by changing the light level. It also avoids using radioactive sources. Bruce > On 03 April 2017 at 15:05 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric. > > A pulse source with somewhat more pulse to pulse jitter may be more useful in that averaging will occur over a wider range of fine interpolator codes. > > Bruce > > > > > On 03 April 2017 at 05:34 Mark Sims <holrum@hotmail.com> wrote: > > > > I implemented the channel offset compensation feature specifically to make measuring cable delays more accurate. I wanted to measure my TDR calibration cable and another very precision delay line. I used Heather to null out the channel/connector delays and then replaced one of the "T" cables with the TDR cable. > > > > My test setup / TICC was coming up with a -306 ps channel offset error. The test signal was the 1PPS output of a FTS4060 cesium. Connecting / reconnecting one of the test setup cables and re-doing the offset test (I was averaging for 1800 seconds) could produce compensation values that varied from -300 ps to -325 ps. Just de-doing the offset test without messing with the cables produced values around -300 to -310 ps. > > > > BNC connectors aren't the best for precision timing. I need to re-run the test with SMA cables / T adapter and the precision HP connector torque wrench and see what that looks like. It would also be fun to lay a coax outdoors and see how the delay changes over a day as it heats/cools. > > > > -------------------- > > > > > > > > > Some “cables” have very long delay numbers. > > > > > > _______________________________________________ > > > 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@lists.febo.com

TAPR TICC boxed