[AMRadio] Screen Modulated 813

david knepper collinsradio at adelphia.net
Mon Dec 11 12:29:35 EST 2006

Zirconium getters best at about 1000 degrees C, this why large metal anode 
transmitting tubes like the 4-400A, 4-1000A, and 3-500 must be operated with 
a dull red to red anode color.  Zirconium also releases some gasses and 
absorbs other gasses at various temperatures.  The varying temperature 
across the length of the anode (and as the anode heats and cools) allows the 
gettering agent to absorb a wide variety of gasses.

You can do what you will but I like to run a little color on my large 

Dave, W3ST
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----- Original Message ----- 
From: "John Lawson" <jpl15 at panix.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Monday, December 11, 2006 12:00 PM
Subject: Re: [AMRadio] Screen Modulated 813

> On Mon, 11 Dec 2006, david knepper wrote:
>> John, you better check your copy of  Eimac's classic on the Care and 
>> Feeding of Power Amplifier Tubes.
>   Which edition?   I think I have 'em all...   ;}
>  I strenuously re-iterate the point that making a sweeping omnibus 
> generalization about 'red plates re-adsorbing gasses' is just that: a 
> generalization, and can be (disastrously) not true in a lot of cases....
>> Of course, running a 6146 red hot is not acceptable.  I was referring to 
>> large transmitting tubes like the 4-400A's, etc.
>   Y'all didn't say that - you said "...the tube..."
>   Nit-pickingly yours:
> John
> DM09fg
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