Wide Band Valve VFO
When some frequency agility is needed to zig-zag between stations in overcrowded HF portions, a VFO is definitely needed.
If low and well stabilized voltages are available, if a sturdy mechanical construction is used to enclose the circuit, if top-quality variable capacitors are available, then a TX based on frequency multiplication is easy to build and rather ample HF portions can be covered with excellent CW tone.
The VFO in the pictures weighs more than 10 kg and uses a 6BQ7A double triode. One section clapp oscillator, the other section as wide band cathode follower, providing a low impedance output.
Only 35 V kedown are provided to the oscillator plate, while 150 V stabilized by an OD3 gas tube, are provided to the cathode follower.
In 6 bands it covers from 1.7 to 3.6 MHz and from 8.0 to 9.5 MHz. More than enough to have all the amateur HF bands at hand, and something more.
The schematic will be published on a near future. Stay tuned ...
Radioman, Nov. 2014
Posted by Radioman | Permanent Link