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
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