This RF circuit measures transmission power from 0.25 W to 10 W. The maximum frequency depends on the diode and the gauge is an analog instrument. A multimeter can be used instead.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...