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Re: [Amps] reading a tube datasheet

To: "Chris Howard" <>
Subject: Re: [Amps] reading a tube datasheet
From: "Tom W8JI" <>
Date: Tue, 27 Jun 2006 16:23:46 -0400
List-post: <>
> On Tue, 2006-06-27 at 12:22, Tom W8JI wrote:
>>  You are reading more into the data sheet than it is
>> saying.
> It is somewhat disconcerting to have someone say the 
> datasheet
> isn't a reliable source of information.

No one said that that I know of. Although I haven't been 
reading all the posts, at least I certainly didn't say that!

What I said was someone wasn't reading the datasheet 
correctly and applying the information correctly.

> I always assumed when it said something like
> RF Linear Amplifier
> Grounded Grid Class B
> Maximum Ratings
> ________________
> DC Plate Current 0.400 AMP
> that's really what it meant.  Now it seems  maybe not!
> (Why would they put that in there?  Did they just pull 
> numbers
> out of the air?)
> Maybe you could step back a little from the current debate
> and say a word about what the datasheet actually does say?

The data sheet is generated early in the design of a new 
tube by looking at samples under certain limited test 
conditions and by the design goals of the engineers. 
Operation outside the exact letter of  "typical operation" 
is widely accepted and very common. Eimac and other 
companies often OK operation outside the guidelines. The 
data sheets themselves even state "If it is desired to 
operate this tube under conditions different from those 
given here, contact the factory......".

This entire worn out thread centers around two things, tube 
life and operational performance.
As I said before and I'll say one last time:

1.) Everyone agrees tube life is NOT an issue.
2.) Multiple measurements show the tube very linear with the 
load line established at 550mA, and it has far less IM than 
any typical exciter with that load line.
3.) IM is caused by deviation in transfer characteristics, 
NOT by following one constant current curve.
4.) The manual doesn't even tell people to operate at 550mA, 
so that is a non-issue. They are told to establish the load 
line at 550mA and back drive off to 400mA for operation

I really can't contribute anything else to this thread. I 
think everything that needs to be said has been said several 
times. People can always get a copy of "Care and Feeding of 
Power Grid Tubes" and read much of what was said here in 
that book (and read the book several times if they need to 
see it over and over again).

73 Tom 

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