[Amps] Plate Load Impedance

[Phil Clements]

> I am going through the exercise to design the Pi-L network for a new
> amplifier.  Calculating the plate load impedance by two different
methods, I
> come up with two vastly different answers.
> With a tetrode and the formula  for class AB1 operation, I get about
3400
> ohms.  I realize that this formula is an approximation and the
factor of 1.3
> might not be quite right, but.
>
> Using the constant current curves in the Eimac data sheet for the
tube,
> 4CX1500A, and the method given in their book, I come up with a much
lower
> value, around 2500 ohms.  I also realize that there are some
approximations
> in this method too.  However there is a significant difference in
the two
> methods.
>
> Does anyone have any ideas where the truth lies so I can get on with
the
> construction of the Pi network?
>

I always call or E-Mail Reid Brandon @ Eimac to get the strait dope
when I start to roll a new amp.
On a 3CX3000A7 for example, Eimac uses a factor of 1.8. AB1 and a
tetrode will vary your mileage.
Reid is there to make you have a successful marriage between their
tube(s) and your chassis.

(((73)))
Phil, K5PC