> Of course, if the designer used tetrodes with passive grid and
> perhaps an input LPF to absorb any input capacitance (see Svetlana
> application note), then a five or six position output tank switch
> would be usable.
You can, with the correct tube and proper components, make a
somewhat broadband input. The problem is the amp is a tetrode,
and to do it right the rest of the circuitry costs a lot more than you
save on the switching.
The key word is "right". Some people think unregulated voltages
aren't a problem. The fact is, tetrodes are dirty enough when
properly regulated. Look at the IMD comparisons of the ETO amp
with a tetrode compared to an AL-800H...which is a low dollar 1500
watts SSB duty-cycle amplifier.
Even if the operating problems of getting a customer to load the
tetrode correctly are solved, and you accept the reduced IMD
performance and fact that tubes may be a future problem (a tetrode
is harder to substitute with another tetrode than a triode is with
another triode), you still haven't solved the bandswitch problem.
You'd still need a vacuum cap...or else have to switch an inductor
between the tube and the tank on almost every band....to get
decent performance from 160-6 meters.
There isn't any emerald road with tetrodes.
73, Tom W8JI
w8ji@contesting.com
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