Indicated for adjustment in transmitters for the 11-meter band, this circuit with analog meter was found in the Radio Electronics magazine of January 1978. The circuit does not use a power supply.
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...
This interesting source or isolation transformer also allows to vary the output voltage by...
In this circuit the CA3140, an operational amplifier, is used as a comparator with the zener diode...