[Amps] Multi-Amp w/ Power Combiners

[James Durham]

On Aug 25, 2012, at 9:40 AM, Dr. David Kirkby wrote:

> I think one might struggle with tube amps, as any tuning adjustments on the 
> input or output are likely to change the phase of the signal at the output of 
> the amps. Unless the two signals arriving at the combiner are in phase, you are 
> not going to get the desired effect.
> 
> I might be wrong - I have never tried it, but I suspect it will not be quite as 
> simple as one might like.
> 
> Dave

Yes.
I remember RCA made an AM broadcast rig called the "Ampliphase"
that used two tubes 90deg out of phase and obtained AM by phase-
modulating one of the tubes' RF input to 0 deg or 180 deg compared
to the other tube and it had a reputation for the phase drifting and was
a bear to tune.  This was in the broadcast band.  10 meters with tube
amps combined , worse even than 2 tubes in one box, might be very
difficult  to keep stable. Maybe 160?  

-- Jim , W2XO