# Measuring RF voltages with a multimeter

Is it possible to measure RF voltages with a multimeter? I have a multimeter which can measure AC voltages up to 600V RMS, but I'm not sure because I don't know if it assumes the signal to be 50Hz, or at least not several MHz.

I'd like to know the RMS value of the voltage on my antenna. When measured with my multimeter, it shows it's beyond 600V~ RMS. When I measure just before my last inductors I have about 350V~ RMS.

I have a scope which goes up to 400V peak-to-peak on the screen (I'm not sure about its maximum ratings), but I'm reluctant to try, because I'm not sure if the measurements of my multimeter are correct, and I wouldn't like to damage my scope.

So: is it likely that a simple, common multimeter can measure RF voltages? I've seen this circuit which suggests that it's not possible and you have to put something in between the RF and the multimeter:

However, they're rectifying the RF voltage, so they in fact measure with the DC input. My multimeter has an AC input - it's unclear to me if a circuit as this one is still needed in that case.

• en.wikipedia.org/wiki/True_RMS_converter – Kevin Reid AG6YO Jan 31 '15 at 18:33
• Your multimeter may have AC voltage readings but likely not at RF frequencies. I have a Fluke 187 DVM and the AC voltage measurements are reasonably accurate up to about 100 KHz and then the accuracy falls off. Also, most of the time the RF voltage measurement is made on a "sampled" signal via a coupler. This allows the coax to have a straight-line through to the load (Antenna) with very little loss. Since it is sampled via a coupler, you would need to calibrate the voltage readings which usually requires another quality lab style RF voltmeter. – K7PEH Jan 31 '15 at 19:38
• Yep, that makes all sense. Is there a way to tell whether the voltage measured by the multimeter would be too high or too low (and ideally, more or less how much)? I guess not. Will give the converter a shot. – user885 Jan 31 '15 at 20:26