A pair of tetrodes or pentodes, grid driven in AB1 need little drive,
so the 12 watts from a K2 may be sufficient for driving something like
a 4CX800. You may need switched tuned inputs instead of passive grid to
drive it with 12W. I think most amplifiers on the market are class AB2
(usually grounded grid), which need plenty of drive. The drawback in
using tetrodes or pentodes in AB1 is the requirement of a regulated high
voltage for the screen grids and the amplifier would probably need
neutralizing also, especially if not operating in passive grid. Most
available tetrodes are ceramic types, so a blower would be necessary too
As you intend only running CW, it may be worthwhile investigating class
E amplifiers which would present you with more modern obstacles to
overcome :-)
73, Dave G3VGR
K2 #4783
Chris Kantarjiev wrote:
[warning thread drift]
The Linear Amp kits seem to need a fair amount of drive. I've been
idly thinking about a linear that would allow me to drive it with
my barefoot K2 and get 600-800 watts out for CW.
I've been told that such things were "common" in the 70s. One description
I was given is
two stages, with a pair of 6CL6 pentodes in class A passive grids,
driving a pair of surplus 4CX250Bs in AB1,a very common design.
0.1W in gives 650W out.
which sort of means something to me, but will certainly start many
evenings of study.
If this was "common", it seems that there should be articles. I haven't
had much luck finding one (there's an article from 1959 that uses
a single 4CX250B). So, how about it, you guys who were there then? :-)
73 de chris K6DBG
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