Found in the October 1979 Radio Electronics magazine, the purpose of this circuit is to monitor the coolant level in a car's radiator. The circuit is based on the LM1830.
With a coil formed by 7 turns of 26 AWG wire this circuit operates in the 27 MHz range. But you...
The circuit shown is a commercial electronic voltmeter sold in Japan in the 1960s. The circuit is fully...
This amplifier for recording heads was found in a Radio Electronics from September 1963. The...