Cet article est extrait du site de Jean Luc F6HOY : http://www.f6hoy.com/
Avec la prochaine arrivée de vieux Hallicrafters à la maison se pose la question d’un VFO externe capable d’avoir 20 à 25V…
C’était le cas avec mon Jhonson Viking 2!
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-02-2-1024x768.jpeg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-01-300x225.jpeg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-03A-300x225.jpeg)
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.
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-25.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-07-300x225.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-B-03-1024x466.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-B-01.jpg)
The Johnson Viking II needs a fairly large input signal at the VFO socket. Here are two extracts from the Johnson Viking II manual.
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-B-06.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-B-05.jpg)
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.
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-F1LAG-VFO-BUFFER.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-F1LAG-VFO-BUFFER-2.jpg)
>>>>>>>>>>>>>> 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…
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-14-300x225.jpg)
![](http://www.f6hoy.com/wp-content/uploads/2019/04/F6HOY-VFO-B-07-1024x606.jpg)
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.
![](http://www.f6hoy.com/wp-content/uploads/2019/07/F6HOY-VFO-8040-1024x768.jpg)
Merci Jean Luc pour cette réalisation