This circuit can be used to test crystals from 1 to 20 MHz and also has an output to measure their frequency. We found it in the November 1998 Electronics Now magazine.
This FET voltmeter is from an old 1974 amateur radio publication. The circuit can use MPF102 or...
This indicator was found in a 1974 publication, but it can be fitted with the BC548 transistor or...
This circuit was found in the comparator's own documentation, serving others in the same series. The...