A VFO 80 / 40 m for the Johnson Viking and others Vintage Transmitters

The VFO is a Wavehunter dual channel VFO based on a single BF245C FET. It gives a moderate amplitude signal and has high output impedance.


The Johnson Viking II needs a fairly large input signal at the VFO socket. Here are two extracts from the Johnson Viking II manual.

Therefore the Wavehunter VFO must be followed by a buffer-amplifier. Based on the above Johnson information and taking some margin, its output capability for the 40m band should be:

 Minimum: 6 V rms (17 Vpp)
 Target: 8 to 12 V rms (23 to 34 Vpp)
 Maximum: 15 V rms (42 Vpp)
 Load impedance: 25 kΩ

Thanks to Alain, F1LAG my brother, for his help and the nice buffer.


>>>>>>>>>>>>>> Read more about the VFO buffer from F1LAG


The frequency meter…

I first tried with a small Chinese tool. Nice but impossible to plug directly. The only way was to do a coupling. And after some hours the display disapeared…

Finaly i used a small frequency meter found in a Hamfest for 2 euros… The knob is coming from a DDS AOR used with my Collins line.