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Yes. 73, Willie N1JBJ

I can give a practical use - you have a box of cable (whether Cat 5 or coax or HV neon wire) where it's not obvious how much is in the box (since you didn't buy the stuff with "foot markings" on the

Dear all, Could someone answer this:- Why is there this obsession to electrically measure the physical length of an arbitrary length of coax? Unless you are trying to make a long distance physical

See also a couple of videos from Alan W2AEW on this subject, including a simple TDR circuit which I have built and works adequately for my needs. Chris G4CWS

Kind of circling back around to *this* question. You've got a spool or coil of coax sitting in front of you.? How do you measure the physical length without actually unspooling or measuring the spool

"Scavenger Time Domain Reflectometer Coaxial Cable Tester," Stan Johnson, W0SJ. QST, May 2021, pps. 30-33. 73, Vince N2JRS

Does this kit TDR require an oscilloscope to make the measurement? [email protected]> wrote:

The latest versions of the NanoVNAs provide the TDR function.

Syd, I would like a board of kit if it is still available. Please provide details. Thanks, Mike N2MS

Sounds intriguing, do you have more details, or maybe a pointer to the QST project? If you made your boards with OSHpark, you can designate them as public, so anyone can order them. Not sure if other

In an older publication of QST there was a TDR project. I made it and it works quite well for measuring electrical length of a coax and from that you can calculate the velocity actor. If you can find

I too was having the same problem of my NanoVNA-H not being recognized by DfuSe Demo. However, I tried ST's STM32CubeProgrammer. It was able to recognize the DFU device, and I could upgrade the

Try 0.66 and measure a piece of the same cable with a ruler and the VNA. Adjust VF until the two agree. If you can see the dielectric, use the VF for another cable with the same dielectric. Glenn --

How many answers need to be posted about this? I posted a link that gives the info for the most common materials used, including foam polyethylene and foam polystyrene. Zack W9SZ

Most *solid dielectric* cables are close to 0.66 Foam dielectric tends to be faster (because the Vprop is related to the permittivity of the dielectric, and foam is lower than solid)

You have no way to know, unless you make another measurement to compare physical and electrical length.

Not that there can’t be reasons for doing this (buying x feet of new coax to replace it with), but if you state the reason for wanting this measurement, maybe there’s a different way to solve the

Look at the end of the cable. If the insulation between the outer shield and center conductor is a hard and solid material the velocity factor will probably be 0.66. If this insulation is a soft foam

Here's more data: https://www.febo.com/reference/cable_data.html Zack [email protected]> wrote: <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_conte

Most of the commonly found cables have a velocity factor of 0.66. Zack W9SZ <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>