[Amps] Triode Amps

[Rob Atkinson]

>My guess is that the hardware to withstand higher B+ Is hard to come by.

That's not a problem.  Plenty of parts out there that can work.  Lots
of AM rigs swing up to at least 4 KV DC on positive modulation.  Then
the peak of each RF cycle goes higher.  A couple guys, one now SK (Bob
W2ZN) run or used to run Continental power pebbles on 160.  That was a
PWM rig that ran a pair of 3-500s in the final with a third one used
as the switch.  8 KV from the h.v. supply.

No, the problem isn't h.v. parts; it's stabilizing the PA so it
doesn't take off when the anode v. gets up over 4 KV.  Cathode driven
is easier, one reason for its popularity, but even a g.g. 4-1000 can
get squirrely on the high bands with 5 or 6 KV on the plate.

BTW a pair of 3-500s will produce 1500 w. in g.g. cathode driven
linear service but it takes more drive than a lot of hams can produce,
around 130 watts.  That's partly because modern amplifiers don't use
plug in coils for band changes which optimize the Q for each band.
The 3-1000 is a better choice because it's rated for higher plate v.
Harris and BTI used it.

73
Rob
K5UJ