[Amps] Plate impedance

[David C. Hallam]

The formula given in RCA Transmitting Tube Manual TT-5 is

Rp = 2(Eb - Ebmin)/Ibmax

Where

Eb =  Plate (or anode) voltage at value chosen for operation
Ebmin = Plate voltage at minimum of swing; for a tetrode it must be not less
then the screen voltage
Ibmax = Plate current at Ebmin

David
KC2JD

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
Behalf Of Will Matney
Sent: Monday, April 10, 2006 11:18 AM
To: amps at contesting.com
Subject: Re: [Amps] Plate impedance


Peter,

In this edition of the Radiotron Designers Handbook, 3rd edition, (c) 1945,
it says;

(1) "The plate resistance (rp) is the rate of change of plate voltage with
change of plate current, and the grid voltage being maintained constant".

The formula here uses (u) for amplification factor, (gm) for mutual
transductance, and (rp) for plate resistance.

rp = u / gm

(2) "The plate resistance is given by the change of plate voltage divided by
the change of plate current for constant grid voltage, that is;

Ep1 - Ep2 / Delta Ip

Delta, meaning the delta sign before Ip which means change in.

I have a copy of the RCA transmitting tube book, and that may be where I
read that. I forgot about even having a copy! I'll dig it up where ever it
is and take a looksie. I saw the 1950's version of the Radiotron Designers
Handbook has over 1000 pages. This old one has 352 counting the index. Of
course it is all tube info too.

I would still like to find the factors for A, AB1, AB2, B, and C just for
sh**s and grins.

*********** REPLY SEPARATOR  ***********

On 4/10/06 at 3:17 PM Peter Chadwick wrote:

>I seem to remember my RCA TT4 handbook listed the load impedance as the
>plate swing divided by Ib0, the quiescent plate current. A typo, obviously.
>
>73
>Peter G3RZP
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