How Long Is Your Coax? Testing with NanoVNA

You can use a NanoVNA to measure coax length or distance to fault, similar to a TDR using the Transform function.

*Note the model I use is a NanoVNA SAA-2N - not the H4*

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⏱️Chapters⏱️
0:00 What's the length?
0:24 Velocity factor
1:31 Setting up the NanoVNA
4:23 Measuring the cable

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[kensejkora]

Great video, Hayden. On many of the newer firmware versions (latest for the SAA-2N is v1.3.31 dated ~18-Jun-2024) there is actually a feature to directly measure the cable length. After you turn on the NanoVNA, invoke the menu, select 'Back' (if necessary), then select 'Measure', and then select 'Cable (S11)'. After you enter the velocity factor in percent, the display will show the cable information such as the characteristic impedance, length in meters, and return loss. Also, you can select more sampling points to improve resolution, such as 401 points vs 101 points. This is accessible under the 'Stimulus' menu as 'Sweep Points'. Again, great video. 73 Ken -- WBØOCV

[jez]

Always nice to see ways to use the nanoVNA.

[mandytuning]

Best 5min of any nanovna video. Simple and straight to the point without crazy formulas.

[FEPLabsRadio]

I knew it could do that, I've never done it on the nano though. Good work mate!

[wespurdy]

This is really helpful. I recently installed a cable through my roof from a large roll and cut off the end and installed a plug. But I have no idea how much cable I used. I will now use this to find out, thanks 👍

[mikeb]

Hayden, this is great stuff. I actually use an Anritsu S412E at work. I am also S412E certified and ETA line and antenna sweep certified. I use my VNA and S4401A quite a bit but don’t know all of its capabilities. Thanks again. Mike. AF4AY

[yetiradiovkyt]

Excellent video mate. I have a VNA but don’t fully understand its many features.

[hugov]

It's pronounced "ess one one" not "ess elevent". The numbers are indices in a 2x2 matrix.

[bitemykrank]

And in the time you took to set up the VNA, and " guesstimate " your cable length, Myself, with no help from anyone, and using a simple tape measure not only measured 10 seperate cables, but I even managed to put the antenna's back up in the air aswell.

[Davidm-MTPT]

You can also use the numbers on the jacked of the coax and subtract one from the other :)

[forgetyourlife]

When I look up velocity factor for rg-8x every manufacturer has a different percentage.

[WaschyNumber]

Hello
I'm new to HAM and learning, I would like to ask how long can a cable be, for testing for example a nanovna to the radio or to a antenna, I mean if it can't be direct connected on the radio or antenna and so on, becourse of space reason on the devices, please ?

[RobB_VKES]

If you want to improve resolution calibrate the VNA, only calibrate over the expected range of frequencies rather than the full 3GHz. 101 points over 3GHz is very sparse. The VNA simply interpolates between the 101 calibrated points leading to a false sense of measurement confidence.

[DGrdan-mt]

Hi, Is it possible to measure the length of the 75ohm cable, rg6 or rg11?

[ashemoski]

I can't believe it took me 2.5. minutes to realize that Nano has N connectors! (When you mentioned "the SMA version...") 😳

[Penfold]

How much does a good or poor calibration impact the measurement ?

[DreadMakerRoberts]

Challenge. I have a co-axial cable connected to an antenna wire. If I know the velocity factor of the wire can I have the vna read from the connector at the antenna to its final length to get the wire length?

[gregwmanning]

I need to get a two port device, I wonder if this is it?

[knvbw]

Next video would be good to learn how to find the velocity factor of your cable; since the same type of cable will be different between manufacturers and even batches, for the no name wholesalers.

[martinpetig]

never seen a vna with N connector ... mostley sma... never heard a new invention ...measuring tape? 😁 🤣😂