The purpose of this circuit is to measure the resistance of an antenna at the resonant frequency. The circuit is from an old American documentation for hams.
The critical component of this circuit is the transformer. T1 and T2 can be BD135 and T3 / T4 can...
Found in Popular Electronics from the 90s, this circuit can employ other low power audio...
This circuit is from a 1967 publication. It is possible to power a fluorescent lamp from a 12 V...