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Why not measure the capacitance of the adaptors, alone, without the cable. You may have to borrow or buy those connectors identical to those on your cabled adaptors. Yes, a longer cable would also

Dave (W?LEV) - I looked at the method you described to determine the characteristic impedance of coax cable. See the attached plots from SimSmith using RG-58A/U.

Jim Lux and I have both written 1 MegOhm (if Jim had such a resistor). Not that this an optimum value by any means. It's just what we had. The sole purpose of the resistor is to keep voltage from

You could calibrate, with the 10 dB pad in place.? The SNR of the measurement is worse, but it's still valid. The other thing is that the output Z of the NanoVNA is probably pretty close to 50 ohms.

Also low inductance, low capacitance. Kent, AC1HJ

Over and above the NANOVNA issue: I presume you are dealing with a BJT amplifier? Even with a FET PA, the following should be considered. The input and output impedances of a power amplifier (PA)

This firmware conatain measure cable option (MARKER->MEASURE->CABLE): Use 1/4 wavelength (on image this marker 1 point) For detect cable impedance used 1/8 wavelength (on image this marker 2 point)

You can also iterate the VF. Measure the cable length exactly. Use Transform and set VF to a guessed value for the cable. Set the marker at the cable end on the curve (the top) and see what length the

I need to measure S11 going into an RF power amplifier (1-15 MHz range of interest.) While the amplifier has proven stable (so far) when driven through a 10 dB attenuator (from RF source), I am

Fred: You would need a resistor which would handle the power AND the voltage it would see; for legal limit transmit power, many otherwise-suitable resistors have insufficient voltage rating. Phil AD5X

No, not necessarily. Some types of these do not short both conductors together and even if they do, there's no guarantee that the potential of the feedline will be the same as that of your device

Yeah, longer would be better, and there's no need to cut a specific length to make the measurement. Any reasonable length you have lying around can be used as long as you can measure its physical

Exactly.? Or you can put in 100 for the VF, measure the length, and compare the measured length to the actual physical length.? VF = physical length/VNA length@100 VF I'd use more than a meter long

I have an idea for finding the velocity factor of any cable. Please let me know if this could work. The NanoVNA can measure cable lenth accurately if the cable’s VF is known and can be input into

I would always discharge an antenna coax before measuring, just to be on the safe side. However, I would assume that if one has an unun, balun, or matching transformer between the antenna an receiver

I always connect my coax from all antennas to ground when not in use. No problems with static then and I can measure them any time I need/want to. Well, as long as I've just disconnected them from

This is true, and one of the wires connecting one port to the other might be "inside the VNA" (i.e. the chassis ground)

Megohms. I used to use scrap black vacuum hose - it was UV resistant and happened to be conductive, and best, it was cheap. Now, I'd probably just use a 1 Meg resistor if I had one.

If your antenna is fed with coax, it appears as a single "wire". However, in reality, it consists of two conductors: 1) The single inner conductor, and 2) The outer braid. Fields are conducted to/from

I have a 1 MΩ permanently connected across the output of my transmatch. When the feedline is disconnected from the transmatch (most of the time), I have a 50 Ω resistor paralleled with a 70 volt