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Hi guys and greeting from Buenos Aires, Argentina. We're in full country quarantine since thursday, I was planning on buying some cable, but our govt acted so fast that I had no time, so I'm stuck at home with a couple of rolls of coaxial cable and wanting to improve my external antenna for my HT.
Have a Hugen VNA with Eddy 0.7 firmware but still don't trully know how to use it besides basic stuff.
They are probably 75ohm but from photos I found on the web some may actually be rg58, can you guys tell me how to use nanoVNA to know the cable impedance?

Thanks

Try these:

/g/nanovna-users/topic/69269493

50 or 75Ω, it shouldn't make a big difference unless you are wanting to push high power through it.

Saludos Pablo,

You could use the TDR function of the NanoVNA to check the impedance of an unknown coax cable by soldering a non-inductive variable resistor (value within the range of the suspected cable impedance) at the far end of the coax cable. Normally if you leave the end of the cable open circuit you will see a reflection due to the impedance mismatch. Vary the value of the variable resistor and once you see that the reflection is gone you know that the resistance that the variable resistor is set to is equivalent to the cable impedance. Just measure the resistance of the variable resistor with a DMM and you're good to go.

Hope that helps.
Alex

Pablo you can also take a look at this video that is very detailed on how to determine the impedance and velocity factor of any unknow coax cable:

Howdy Pablo! This virus should has thrown the world into turmoil... I hope it turns out to be a minor virus, not as bad as the flu.
As far as coax for antenna for an H/T, I would assume around 145 MHz and/or 445 MHz for ham bands?

I use a good quality RG-6 for my scanners. This is of course adding in a 1.5:1 SWR but due to being used receive only, it's of little consequence.
I have 800 MHz trunking systems I monitor as well as low band VHF (45 MHz) and the coax I swept is pretty wide band and low loss. I have multiple scanners so I use a small CATV distribution amplifier. Each port is 7 db gain so it compensates for coax losses. I have under 20 meters going to a discone antenna. The amp does provide a bias-t function so i could use an LNA at the antenna....the one I have is 17 db gain but I don't need it. My scanners all have BNC antenna connectors so I use a BNC-F adapter and then about .7 meter pigtails of RG-6 from the amp to the receivers. It all appears to work well.
Food for thought or maybe excess information....

73 de Tim, K4SHF

Thanks a ton guys! have some 50ohm for dummy loads I planned to build, will use and report.