[Amps] amp with push-pull output and magnetic coupling to the antenna

[gdaught6 at stanford.edu]

Gene May wrote...
 
> I am beginning the design of a 160 - 10M amplifier that will be cathode-driven, 
push-pull, probably use tetrodes (tentatively 4CX600J's) and couple the tubes' tank 
circuit to the antenna circuit with what is often nicknamed a "swinging link".  
A "swinging link" would couple the antenna circuit coil magnetically to the tubes' 
tank circuit by having the antenna coil on an arm that swings or meshes in and out 
of a gap in the tank coil; the amount of coupling is varied and mechanically adjusted 
by changing how far or deeply the coils are meshed together.  Around fifty years ago 
and more, this was a common technique.  However, as many readers of this probably 
know, it is, ah, "uncommon" now.  I have looked far and wide for the mechanical 
components to accomplish this, unsuccessfully.  Now the specific questions:

As I recall, the inductance of the swinging link (and therefore, the physical size) 
varies quite a bit from 160m - 10m.  This necessitates having different plug-in tank 
coil assemblies for different bands, or a monstrous rotating turret/switch.  The same 
would likely be required for the cathode circuit components.  This is not to say it 
can't be done, but it sounds to me like a real challenge to accomplish.  

73,

George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 1-2, 2011