[Amps] Need for input tuning circuit

[Vic Rosenthal]

Bill L. Fuqua wrote:
> But, if you are only operating CW or FSK it is not needed. Due to the fact
> that intermodulation distortion is not an issue. You can operate class C.
> The only need for some ( very little) linearity only to prevent key clicks.
> If you used a very nonlinear amplifier such as class E key clicks will be
> produced when using OOK or CW.  That is why for CW they modulate the power
> supply. It softens the turn on and off. 

Years ago I built some 813 amplifiers for CW work.  I used the standard 
clamp-tube circuit in which class-C bias is generated by the grid current flow 
through a resistor (i.e., the bias is in effect rectified driving voltage) and 
the clamp tube protects the tube by removing screen voltage when the key is up. 
  This had the advantage of preserving the keying waveshape while running the 
tubes in full class-C for efficiency.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco