Negative ion detector (CB21001E)

This tube circuit was found in the magazine 73 for radio amateurs in an issue from the 1980s. Note the transformer used to power the circuit.

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Crystal oscillator with compensation (CB9642E)
This temperature compensated circuit was found in a 1980s American documentation. The power supply...
LM3914 Single Powered Voltmeter (CB25456E)
This circuit is an improved version of the previous ones with the LM3914. We found it in the March...
Precedence Indicator 2 (CB12329E)
This indicator was found in a 1974 publication, but it can be fitted with the BC548 transistor or...