One of the useful tool that you can make out from your junk box is this rf voltmeter. I found this circuit from the internet and make a prototype out of it which turns out a very handy tool in determining the rms voltage in my hf /vhf projects. I use it to determine the output power of my rf amplifier, setting the null in my balanced modulator, determining the peak voltage output of my oscillator, peaking a band pass filter, etc... It takes only 3 components to start with. I use 1N60 germanium diode to rectify the high frequency AC signal into dc voltage readily compatible with any digital multimeter. The diode exhibits 0.3V of forward bias voltage as measured by my digital multi meter. My prototype rf voltmeter is contained in a small pc board assembled in surface mount fashioned. Two connectors soldered on the edge of the pc board to accommodate the positive and negative probe of my digital multimeter.
Tue, 10/25/2016 - 15:38