by Harry Lythall - SM0VPO

Without access to a Spectrum Analyser or a VHF Oscilloscope (and that is most of us) then it can often be quite hard to get circuits to work, or even find out what is going on the completed project. A basic 10K probe can be used to detect the presence of RF and even give an indication of the order of magnitude of the same. Here is a basic 10K RF probe.

D1 should be a Germanium point contact detector diode or a "Zero Bias" silicon diode. The multimeter should be set to the voltage or milliampere range. If you have not got a multimeter then use any-old micro/milliameter inseries with a suitable resistor.

With a voltmeter then you can get a reasonable indication of the RF voltage level. If you want the probe only for HF circuits then you could increase the 10pf capacitor a little (say - 47pf) so the sensitivity becomes more uniform at lower frequencies.

Have fun from Harry - SM0VPO

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