Field Strength Meter (CB6538E)

Found on Popular Electronics this circuit has variations found throughout this site and section. The transistor can be any general purpose.

Peak Signal Indicator (CB25966E)
This LED indicator circuit uses an LM339 comparator. The circuit was found in the January 1995...
3 V Amplifier (CB482E)
This circuit is originally recommended as hearing aid or stethoscope. The output transducer is a...
Frequency Doubler (CB4869E)
This low-frequency circuit for alternating signals is from an early American 1980s documentation. The...