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HOMEMADE ACCURATE RF-POWER METER AND DUMMY LOAD 50 OHM

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HOMEMADE ACCURATE RF-POWER METER

It is simple but very precise RF output power meter which can be used for measure the RF output power of radio transmitters, and transceivers

There is a 50 ohm dummy load as well.
Frequency range: 0 to 2 GHz
It can measure from 10 mW to 120 W.

(click on a chematic above to see it in high resolution)

A special 50 ohm / 250W non-inductive resistor was used, but it was enough for me to calibrate the instrument to 120W.

I bought the resistor very cheaply (only $ 2) from AliExpress.

The whole instrument cost me less than 30 dollars including aluminum box and heat sink for dummy load resistor, which is incomparably cheaper compared to factory similar instruments with inflated prices.

Accuracy is more than necessary for all amateur radio purposes. I will not specify, but it is more accurate than several factory instruments from many well-known brands.
There are two videos attached and more photos of the homemade process and precise adjustment and calibration.
There is connector for Digital Voltmeter on the front panel, so One can connect DVM to measure exact DC voltage value and calculate exact RF-power with well-known Ohm`s low formula.

It is possible to make this RF powermeter without any analog meter. Just use a normal Digital Voltmeter (DVM) connected to the DVM terminals on a schematic diagram. In that case you will measure the DC voltage and have to transform (calculate) the volts to RF power with the Ohm`s Law formula. (In that case you have to calculate forward voltage drop on diodes also) All three diodes BAT41 together in series have only 0.3 V voltage drop on 100 microampers current through them. I am using schotkky BAT41 diodes because they have very small capacitance.

I am using 3 diodes BAT41 in series to drop down the diode capacitance in order to increase frequency range up to 2 GHz. Additionally, three diode in series can handle 3 times higher Voltage, which is important if you want to measure RF-power up to 120 W.

A picture is worth a thousand words, so there is whole DIY storry in following pictures.
There are few videos at the bottom of this page also:

The finished RF Power Meter you can see in the video on this LINK

The Calibration process with known DC voltage is on this VIDEO

You can see the Video of measuring the RF output power of handheld UHF radio transceiver with this RF Power Meter HERE

There is another video of measuring the RF output power of several VHF/UHF transceivers HERE

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Mile Kokotov (2021)

Mile Kokotov, M.Sc. is industrial engineer manager and has a master`s degree in technical science with almost 40 years expirience in RF-technology.

Feel free to visit other articles and projects on his website

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