Found in American documentation from the 90s, this circuit can measure frequencies on a linear scale from 0 to 1 kHz. The components can be changed to measure other ranges.
This circuit for UHF between 800 and 1 000 MHz was found in an American documentation from the...
This circuit can operate between frequencies from 1 to 15 MHz depending on the coil. For 3.5 MHz...
This circuit was found in Radio Electronics magazine from June 1961. The distance between stations is...