[AMPS] Re:Question: input Z on class AB gnd grid pair 4-400 ??

[Charlie Ocker]

Jan.E.Holm@telia.se wrote:
> 
> With 100W drive and 3kV on a pair of 4-400īs it might
> be a problem to get 1500 out, better run 4 kV on plates.
> I have a 3 tube 4-400 amp 10 - 160m and it runs excelent.
> After 20 years of service it still runs full output and
> the tubes wasnīt even new back then, I run slightly less
> then 4kV on them and they are GG. If you have the hardware
> for a 3 tuber thatīs the way to go.
> 
> 73, Jim SM2EKM
> 
> PS: You can use the same tuned input as a SB-220 (or similar)
>     uses and just tweak it.

Hi Jim,

Thanks for the reply.  Your idea of a 3 holer sounds neat.  I wasn't
expecting to get more than 1200 watts out from a pair of gg 4-400's.  I
think that's about all you can do assuming 60% efficiency in class AB
without exceeding their plate dissipation.

I'm curious what values you used in your tank circuit.  The problem that
I see with 3 tubes is the increased Cout (plate to gnd) that the pi-L
network will see.  It's probably not a problem on 160 through 40, but
the Q of the network must be pretty high on 10m.

BTW, the bottles that I will be using are the pulse rated version of the
4-400, the 4PR400A (8188).  I have 5 of them.

73,
Charlie  N9CO

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