Re: [time-nuts] Cable length calibration (Brooke Clarke)

Hi, Brooke, Very interesting stuff. Thanks for the link. Question - Is any of the older chirp sounder equipment now available on the surplus market?? Thanks. ... MartinVE3OAT On 02/07/2016 12:00, time-nuts-requ...@febo.com wrote: Hi Mike: For quite a while I was heavily into

Re: [time-nuts] Cable length calibration

On 7/1/16 9:04 AM, Brooke Clarke wrote: Hi Mike: For quite a while I was heavily into "chirp" transmissions. These are HF ionosphere radio transmissions that sweep from 2 to 30 MHz at 100 kHz/sec. In order to "tune" the radio to a specific station (you can not tune by frequency) you need to

Re: [time-nuts] Cable length calibration

Hi Mike: For quite a while I was heavily into "chirp" transmissions. These are HF ionosphere radio transmissions that sweep from 2 to 30 MHz at 100 kHz/sec. In order to "tune" the radio to a specific station (you can not tune by frequency) you need to know the start time schedule for that

Re: [time-nuts] Cable length calibration

Hi > On Jul 1, 2016, at 3:40 AM, Mike Cook wrote: > > >> Le 29 juin 2016 à 22:18, Poul-Henning Kamp a écrit : >> >> >> In message <20160629192850.19c29406...@ip-64-139-1-69.sjc.megapath.net>, Hal >> Mu >> rray writes: >> At one point

Re: [time-nuts] Cable length calibration

> Le 29 juin 2016 à 22:18, Poul-Henning Kamp a écrit : > > > In message <20160629192850.19c29406...@ip-64-139-1-69.sjc.megapath.net>, Hal > Mu > rray writes: > >>> At one point they were looking into making a GPS time receiver where the >>> cable length

Re: [time-nuts] Cable length calibration

The 1503 was Tek's long-line (10km) TDR analyzer. IIRC, it put haversine pulses of about 5v onto the line under test (~10v open circuit). The 1502 (~600m line length) put pulses of about 200mV onto the line under test (~400mV open circuit). Best regards, Charles Scott wrote: This is

Re: [time-nuts] Cable length calibration

On 6/30/16 5:52 PM, Tim Shoppa wrote: We are all time nuts, so there's an obvious answer: What you do, is raise the GPS up to a height the same as the cable length. You then drop it, measure the time until it hits the ground, and use d = 0.5 a * t * t to calculate d. Then you correct for the

Re: [time-nuts] Cable length calibration

We are all time nuts, so there's an obvious answer: What you do, is raise the GPS up to a height the same as the cable length. You then drop it, measure the time until it hits the ground, and use d = 0.5 a * t * t to calculate d. Then you correct for the velocity factor. Tim N3QE On Wed, Jun 29,

Re: [time-nuts] Cable length calibration

This is highly dependent on the TDR especially ones designed for long twisted pair runs where a high voltage pulse is used to overcome resistive losses Content by Scott Typos by Siri > On Jun 30, 2016, at 10:59 AM, David wrote: > > The Tektronix 1502 uses a tunnel diode

Re: [time-nuts] Cable length calibration

I'd say it depends on the Time Nut . NVP X Distance will get you close and for a beginning time nut is a worthwhile exercise To improve delay calculations now you need instrumentation that not all especially beginning time nuts own.I've got a 20 Ghz Agilent scope/TDR along with a 110

Re: [time-nuts] Cable length calibration

As a practical matter, in the lab we seldom need a cable delay measured to better than +/- 0.5 ns, which we usually do as a time interval measurement, with a 1 pps into a tee on channel A of a TIC and then the cable from the tee to channel B. For cables up to 40 m or so, just measuring the

Re: [time-nuts] Cable length calibration

Scott wrote: When using a TDR its best if cable is unterminated as the discontinuity at the end is helpful as a marker. Someone else previously asked how you're expected to do TDR on a GPS antenna cable since everything is matched (therefore, presumably, no reflections). There are ALWAYS

Re: [time-nuts] Cable length calibration

On 30 June 2016 at 09:19, Scott McGrath wrote: > If the nominal velocity of propagation is known and length is known delay > is easily determined mathematically > Except that coax does not have a uniform impedance or velocity factor. Both will vary as a function of position

Re: [time-nuts] Cable length calibration

The Tektronix 1502 uses a tunnel diode pulser to produce a 50 picosecond output step of about 200 millivolts. There is a misprint in the theory section of the service manual which says "400 V" instead of "400mV". On Thu, 30 Jun 2016 04:19:43 -0400, you wrote: >If the nominal velocity of

Re: [time-nuts] Cable length calibration

If the nominal velocity of propagation is known and length is known delay is easily determined mathematically Time Domain Reflectrometry is the usual technique for finding cable length but even there the cables NVP is an essential parameter if you want to compute length but not essential in

Re: [time-nuts] Cable length calibration

Yo Poul-Henning! On Wed, 29 Jun 2016 20:18:49 + "Poul-Henning Kamp" wrote: > >How would you do that? > > TDR ? > > If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > >

Re: [time-nuts] Cable length calibration

In message <20160629151528.543f4...@spidey.rellim.com>, "Gary E. Miller" writes : >It works on live ethernet cables, so it can't be too harsh. Ethernet is incredibly robust, to the tune of a couple hundred volts pretty much any way you can connect it. Most GPS antenna preamps will

Re: [time-nuts] Cable length calibration

Yo Poul-Henning! On Wed, 29 Jun 2016 22:57:30 + "Poul-Henning Kamp" wrote: > Most GPS antenna preamps will croak before you get up to 10V. The Fluke TDR is 4V max:

Re: [time-nuts] Cable length calibration

Some of the cheap gigabit network cards can and with surprising accuracy On 29 Jun 2016 22:02, "Gary E. Miller" wrote: > Yo Hal! > > On Wed, 29 Jun 2016 12:28:50 -0700 > Hal Murray wrote: > > > bro...@pacific.net said: > > > At one point they were

Re: [time-nuts] Cable length calibration

Am 29.06.2016 um 22:07 schrieb Gary E. Miller: TDR. The GPS already sends a voltage down the cable to power the antenna. Send a sharp down the cable and see when the reflection comes back. Even some of my cheap managed ethernet switches can do that. What reflection? If the antenna preamp

Re: [time-nuts] Cable length calibration

On Wed, 29 Jun 2016 20:18:49 + "Poul-Henning Kamp" wrote: > If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > > The trouble is how to do it without frying the antenna

Re: [time-nuts] Cable length calibration

Am Wed, 29 Jun 2016 12:28:50 -0700 schrieb Hal Murray : > > bro...@pacific.net said: > > At one point they were looking into making a GPS time receiver > > where the cable length calibration would be built-in. > > How would you do that? > > The obvious way is to

Re: [time-nuts] Cable length calibration

In message <20160629192850.19c29406...@ip-64-139-1-69.sjc.megapath.net>, Hal Mu rray writes: >> At one point they were looking into making a GPS time receiver where the >> cable length calibration would be built-in. > >How would you do that? TDR ? If it wasn't behind a choke, the

Re: [time-nuts] Cable length calibration

possible. -Original Message- From: time-nuts [mailto:time-nuts-bounces+greg.dowd=microsemi@febo.com] On Behalf Of Hal Murray Sent: Wednesday, June 29, 2016 12:29 PM To: Discussion of precise time and frequency measurement Cc: hmur...@megapathdsl.net Subject: [time-nuts] Cable length

Re: [time-nuts] Cable length calibration

Yo Hal! On Wed, 29 Jun 2016 12:28:50 -0700 Hal Murray wrote: > bro...@pacific.net said: > > At one point they were looking into making a GPS time receiver > > where the cable length calibration would be built-in. > > How would you do that? TDR. The GPS already

Re: [time-nuts] Cable length calibration

Hi Hal: I think the cal process is essentially a time domain reflection measure of cable length. The GPS receiver and the cable cal hardware would be in the antenna unit. The 1 PPS signal would be aligned at the output of the cable. -- Have Fun, Brooke Clarke http://www.PRC68.com

[time-nuts] Cable length calibration

bro...@pacific.net said: > At one point they were looking into making a GPS time receiver where the > cable length calibration would be built-in. How would you do that? The obvious way is to compare the time you get with a known-good time, but if you had that, why would you want this new GPS