This 4-tube circuit was found on a Radio Craft from December 1945. The circuit has excellent sensitivity. Power comes from a power supply with a transformer.
Shown in Radio Electronics June 1953, this circuit needs a small adjustable source of 0 to 3 V and...
This circuit is suitable for the calibration of old analog oscilloscopes. It was found in...
This circuit was found I a 1965 Radio Schack documentation. The transistors are from that time,...