Empathy List Archives

W

w0kgw

Mon, Mar 12, 2007 6:30 PM

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 w0kgw@citlink.net

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 w0kgw@citlink.net

MF

Mike Fahmie

Mon, Mar 12, 2007 6:35 PM

When you get to the sub-100 ns level UTC is not GPS. And
UTC(NIST) isn't UTC(USNO). Even the national labs don't
agree down to the last ns.

/tvb

Remember that no one lab has the true UTC clock. UTC is an offset to Atomic
Time (TAI), and TAI is the weighted average of hundreds of clocks in dozens
of National Labs all over the world. The Bureau International des Poids et
Mesures (BIPM formerly BIH) collects data and publishes TAI, the
International Earth Rotation Service (IERS), determine when Leap Seconds
increment/decrement the offset based on variations of the earths rotational
period.

See: http://www.bipm.fr/en/scientific/tai/tai.html for details!

-Mike-

> >When you get to the sub-100 ns level UTC is not GPS. And >UTC(NIST) isn't UTC(USNO). Even the national labs don't >agree down to the last ns. > >/tvb Remember that no one lab has the true UTC clock. UTC is an offset to Atomic Time (TAI), and TAI is the weighted average of hundreds of clocks in dozens of National Labs all over the world. The Bureau International des Poids et Mesures (BIPM formerly BIH) collects data and publishes TAI, the International Earth Rotation Service (IERS), determine when Leap Seconds increment/decrement the offset based on variations of the earths rotational period. See: http://www.bipm.fr/en/scientific/tai/tai.html for details! -Mike-

JR

Jason Rabel

Mon, Mar 12, 2007 6:46 PM

This is the basic problem with our hobby... I proudly tell people that I
can measure time to trillionths of a second, but am hard pressed for a
good answer when they ask "why do you need to?"

I find myself giving the deer-staring-into-headlights look when people ask
me that same question!

>This is the basic problem with our hobby... I proudly tell people that I >can measure time to trillionths of a second, but am hard pressed for a >good answer when they ask "why do you need to?" I find myself giving the deer-staring-into-headlights look when people ask me that same question!

MW

M. Warner Losh

Mon, Mar 12, 2007 6:52 PM

In message: 000701c764d6$cfdc51d0$0a00a8c0@Inspiron
"Jason Rabel" jason@extremeoverclocking.com writes:
: >This is the basic problem with our hobby... I proudly tell people that I
: >can measure time to trillionths of a second, but am hard pressed for a
: >good answer when they ask "why do you need to?"
:
: I find myself giving the deer-staring-into-headlights look when people ask
: me that same question!

I usually give the Sir Edmund Hillary answer: because it is there.

Warner

In message: <000701c764d6$cfdc51d0$0a00a8c0@Inspiron> "Jason Rabel" <jason@extremeoverclocking.com> writes: : >This is the basic problem with our hobby... I proudly tell people that I : >can measure time to trillionths of a second, but am hard pressed for a : >good answer when they ask "why do you need to?" : : I find myself giving the deer-staring-into-headlights look when people ask : me that same question! I usually give the Sir Edmund Hillary answer: because it is there. Warner

JA

John Ackermann N8UR

Mon, Mar 12, 2007 7:05 PM

M. Warner Losh said the following on 03/12/2007 02:52 PM:

In message: 000701c764d6$cfdc51d0$0a00a8c0@Inspiron
"Jason Rabel" jason@extremeoverclocking.com writes:
: >This is the basic problem with our hobby... I proudly tell people that I
: >can measure time to trillionths of a second, but am hard pressed for a
: >good answer when they ask "why do you need to?"
:
: I find myself giving the deer-staring-into-headlights look when people ask
: me that same question!

I usually give the Sir Edmund Hillary answer: because it is there.

There it is. Wait, it just was there. Oh, there it is. Darn it,
missed again.

M. Warner Losh said the following on 03/12/2007 02:52 PM: > In message: <000701c764d6$cfdc51d0$0a00a8c0@Inspiron> > "Jason Rabel" <jason@extremeoverclocking.com> writes: > : >This is the basic problem with our hobby... I proudly tell people that I > : >can measure time to trillionths of a second, but am hard pressed for a > : >good answer when they ask "why do you need to?" > : > : I find myself giving the deer-staring-into-headlights look when people ask > : me that same question! > > I usually give the Sir Edmund Hillary answer: because it is there. There it is. Wait, it just was there. Oh, there it is. Darn it, missed again.

MF

Mike Feher

Mon, Mar 12, 2007 9:16 PM

Sounds like Heisenberg :). -

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Ackermann N8UR
Sent: Monday, March 12, 2007 3:06 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier --
ananswer, and a question

M. Warner Losh said the following on 03/12/2007 02:52 PM:

In message: 000701c764d6$cfdc51d0$0a00a8c0@Inspiron
"Jason Rabel" jason@extremeoverclocking.com writes:
: >This is the basic problem with our hobby... I proudly tell people that

I

: >can measure time to trillionths of a second, but am hard pressed for a
: >good answer when they ask "why do you need to?"
:
: I find myself giving the deer-staring-into-headlights look when people

ask

: me that same question!

I usually give the Sir Edmund Hillary answer: because it is there.

There it is. Wait, it just was there. Oh, there it is. Darn it,
missed again.

time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

Sounds like Heisenberg :). - Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of John Ackermann N8UR Sent: Monday, March 12, 2007 3:06 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- ananswer, and a question M. Warner Losh said the following on 03/12/2007 02:52 PM: > In message: <000701c764d6$cfdc51d0$0a00a8c0@Inspiron> > "Jason Rabel" <jason@extremeoverclocking.com> writes: > : >This is the basic problem with our hobby... I proudly tell people that I > : >can measure time to trillionths of a second, but am hard pressed for a > : >good answer when they ask "why do you need to?" > : > : I find myself giving the deer-staring-into-headlights look when people ask > : me that same question! > > I usually give the Sir Edmund Hillary answer: because it is there. There it is. Wait, it just was there. Oh, there it is. Darn it, missed again. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

S

shoppa@trailing-edge.com

Mon, Mar 12, 2007 9:46 PM

John Ackermann N8UR jra@febo.com 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 up six matched cables to go from the splitter to
the receivers -- they all test within about 1 nanosecond of each other.

Obsessive compulsive? Me?

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 :-).

Tim.

John Ackermann N8UR <jra@febo.com> 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 up six matched cables to go from the splitter to > the receivers -- they all test within about 1 nanosecond of each other. > > Obsessive compulsive? Me? 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 :-). Tim.

DB

Dr Bruce Griffiths

Mon, Mar 12, 2007 10:39 PM

Tim Shoppa wrote:

John Ackermann N8UR jra@febo.com 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 up six matched cables to go from the splitter to
the receivers -- they all test within about 1 nanosecond of each other.

Obsessive compulsive? Me?

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 :-).

Tim.

time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

John

Your not quite obsessive enough.
The cable delays (including the antenna to splitter cable) should also
be a multiple of half the signal period to minimise the effects of
residual mismatches at either end of the cable.

Bruce

Tim Shoppa wrote: > John Ackermann N8UR <jra@febo.com> 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 up six matched cables to go from the splitter to >> the receivers -- they all test within about 1 nanosecond of each other. >> >> Obsessive compulsive? Me? >> > > 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 :-). > > Tim. > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > John Your not quite obsessive enough. The cable delays (including the antenna to splitter cable) should also be a multiple of half the signal period to minimise the effects of residual mismatches at either end of the cable. Bruce

LV

Lester Veenstra M0YCM

Mon, Mar 12, 2007 10:52 PM

This is, incidentally, why isolators should be used on these runs.
This does create a problem with LNAs that are DC powered via coax, however
the reality is that many antennas and receivers do not have that great a
match to the coax impedance and could benefit from the clean up of an
isolator. (however as magnetic devices, I wonder about the delay stability
of isolators as a function of temperature)

And while on the obsessive kick, if using splitters, unused ports must be
terminated.

Group delay measurements of an RF transmission system can reveal a lot of
problems that simple loss and return loss will not catch.

Lester B Veenstra
M0YCM K1YCM M0YCM/6Y5 K1YCM/6Y5

Mail Address:

Lester Veenstra
Dawn Cottage
Norwood, Harrogate
HG3 1SD UK

Telephones:

Office 940-6456
Office +44-(0)1423-846-385
Home: +44-(0)1943-880-963
UK Cell: +44-(0)7716-298-224

-----Original Message-----
<NIP>
John

...... minimise the effects of
residual mismatches at either end of the cable.

Bruce

time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

This is, incidentally, why isolators should be used on these runs. This does create a problem with LNAs that are DC powered via coax, however the reality is that many antennas and receivers do not have that great a match to the coax impedance and could benefit from the clean up of an isolator. (however as magnetic devices, I wonder about the delay stability of isolators as a function of temperature) And while on the obsessive kick, if using splitters, unused ports must be terminated. Group delay measurements of an RF transmission system can reveal a lot of problems that simple loss and return loss will not catch. Lester B Veenstra M0YCM K1YCM M0YCM/6Y5 K1YCM/6Y5 Mail Address: Lester Veenstra Dawn Cottage Norwood, Harrogate HG3 1SD UK Telephones: Office 940-6456 Office +44-(0)1423-846-385 Home: +44-(0)1943-880-963 UK Cell: +44-(0)7716-298-224 -----Original Message----- <NIP> John ...... minimise the effects of residual mismatches at either end of the cable. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

BJ

Bill Janssen

Mon, Mar 12, 2007 10:56 PM

I just put a Z3801A on Ebay. This is a Z3801A without an antenna or
power supply
It is a clean unit and powers up and locks on to the satellites
The computer port has options set to RS232. The item no. is 190092049523

Thanks
Bill K7NOM

I just put a Z3801A on Ebay. This is a Z3801A without an antenna or power supply It is a clean unit and powers up and locks on to the satellites The computer port has options set to RS232. The item no. is 190092049523 Thanks Bill K7NOM

time-nuts@lists.febo.com

Delay through GPS antenna splitter/amplifier -- an answer, and a question