During my experience designing and building electronics, I have ran into problems having the correct test equipment to test a circuit. I decided to build the power meter after finding an article titled "Simple RF-Power Measurement" on the ARRL Technical Information Pages. Unfourtunatly you must be an ARRL Member to view the article that I linked to. The article was written by Les Haywood, W7ZOI, and Bob Larkin, W7PUA, and published in QST Magazine several years ago.
The case is salvaged from a local oscillator on a DMC microwave modem, it covered the portion of the board for RF isolation. The bottom plate was cut from the chassis of another modem. I did not bother grinding the metal to fit flush with the enclosure since it would be thrown around and I wasn't too concerned with its appearence at the time. I included an indicator LED to let me know if I left the power meter on or off. Measurements are read by a DC voltage which corresponds to the input power. The circuit is based on the Analog Devices AD8307 Logarithmic Amplifier chip to take RF measurements.
I built the circuit on copper clad PC board and as usual dead bug style. I am sure it's performance is degraded with how it is built dead bug. However, a majority of my projects are on frequencies less than 30 MHz. The effects of leads and wires on these frequencies should be suitable for relatively good measurements. As i approach 500 MHz the accuracy fades a little. The photo of the bottom of the meter shows my calibration scale. I calibrated the unit to an HP frequency generator and marked the appropriate DC values with dBm output.
