This pocket-sized VHF receiver was found in Radio Electronics magazine from January 1961. It uses a transistor and tunes to the 11-meter band, considered VHF at the time.
Found in American documentation from the 90's, this JFET stage has an input impedance of 500 M...
We found this circuit in a 1995 documentation. It can measure frequencies from 100 kHz to over 100 MHz...
This circuit was obtained in a documentation from the 70s. The operational amplifiers used are...