[AMRadio] Screen Modulated 813

Jim Wilhite w5jo at brightok.net
Mon Dec 11 10:24:53 EST 2006

Tubes running red on the plate is not a BIG concern.  It was 
done all the time in commercial service.  It is when they 
get almost white that you need to worry.  A bit of cherry 
red is ok.  Just remember what KYV said, don't exceed the 
plate dissipation of the tubes.

The only other concern is the heat generated.  If you run 
them hot, then be sure they are force air cooled properly 
and the components used in the construction is rated for 


> Jim candela wrote:
>>On AM the single 813 is happy at 70 watts RF
>> out, but it will do 100 watts AM and modulate upward 
>> 100%. It does blush a
>> little but as long as I talk the red stays away.
> That's about how my SB200 runs.  If I run much over 100w, 
> it gets to red for my comfort. I never stop talking so I 
> guess I am at it's peak.
> This would lead me to conclude that I could get at least 
> 200w out of 2 813's in spite of the numbers.  Not a 
> quantum leap but worth the fun project.
> Does that sound right?
> js

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