This circuit uses a special 1950's RCA strobe tube. It can be built with equivalent components for the rest of the circuit.
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...