Brian,
The trick would be matching the phase. With
broadband solid-state amplifiers, this isn't too
much of a problem. With narrow-band tube amps
using hi-q tuning networks, it would be more
challenging. I have never analyzed the problem to
see exactly how sensitive the phase shift would
be to PI-network tuning, but I suspect this is why
this sort of combining is not done with tube
amplifiers. Better to parallel devices before the
pi-network to increase power capability (as in
using two 3-500Zs in one amplifier vs combining
the output of two single 3-500Z amplifiers).
73 de Mike, W4EF..................
From: "Brian Moran" <brianmo@yahoo.com>
> I perused the ~19 meg archive for "power combiners" --
> from my read, the suggestions were mixed for trying to
> sum the outputs of two HF amps. Has anyone tried the
> following?:
>
> Take two relatively-inexpensive amplifiers, say,
> heathkit sb-220's. Make sure that they both work
> reasonably well. With the hybrid combiner available
> from CCI (make sure to use those resistors in case of
> failure of one amp!), combine their outputs.
>
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