I have two related questions relating to the subject above, and would
appreciate advice. In more detail: 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
1. Does anyone know of a source for components or parts that could be used to
make such a system? I am willing to consider taking it/them out of existing
assemblies (e.g., military surplus) but would prefer assemble it from "basic"
parts. I won't go so far as to say I'm desperate, but after considerable
looking, I am very flexible and open-minded.
2. It is necessary for the Q's of the tube circuit (probably to be around 10
to 15) and antenna circuit (probably to be around 1) to be compatible with the
range over which the coupling coefficient between the two coils could vary. As
I understand, it is difficult to impossible to get coupling coefficients higher
than about .3 using coils that would be compatible with the voltages and
currents associated with an output of 1.5 KW. Comments, please?
TNX ES 73,
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