I have seen tantalum plate 813s made in the 60s. RCA made them if I
recall.
They actually had more area than say a 4-125A which has the same dissipation.
It just gets a little hotter and brighter to dissipate the heat via radiation.
Just like the 4-125A, 250th etc.
73
Bill wa4lav
At 01:09 PM 3/29/2011 -0400, Diane & Edward Swynar wrote:
>Hi Carl,
>
>"...Tap the 10M coil in the center with the Tune cap which gives a 4X stepup
>for the required C. Do not add a seperate L coil. The last 4x 813 amp I
>built used the vacuum variable with the tap and it ran full power even at
>the high end of 10M."
>
>********************************************
>
>Yes, thanks for that info...
>
>A very nice classic example of that very technique may be seen in early/mid
>60's editions of the ARRL HANDBOOK: the piece I'm thinking of deals with
>mono-band amplifiers, all employing paralleled 813s...
>
>MUST READING if you're thinking of ever using one of these venerable jugs on
>10...!
>
>BTW Carl, have you ever seen an 813 WITHOUT that rugged graphite plate...? I
>found a couple at a Hamfest a few years ago wherein the plates---I
>swear---look like the plates used in 811A's, only fed with steroids!
>
>"Tin plate" construction all the way. How they can dissipate the graphite
>plate's 125-watts I do NOT know...
>
>I've never tried them on the air yet---and can find no reference in the
>books on them either...
>
>~73~ de Eddy VE3CUI - VE3XZ
>
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