[Amps] 813 efficiency

[Carl]

> ORIGINAL MESSAGE:
> On Sat, 23 Feb 2013 10:01:55 -0500, Eddy wrote:
>
>>It absolutely gobsmacks me how some guys in this hobby would rather 
>>whip-out the ol' VISA card & spend literally HUNDREDS on power amplifier 
>>tubes, when the lowly ol' 813---paired with some twins, of course!---will 
>>do the job as well, and at an absolute FRACTION of the price...
>
> REPLY:
> To get the plate dissipation of a single 8877 would take 12 813s.
>
> Would you put them all in a row?  Or a matrix of 3x4? Or 6x2?
> Or maybe in a circle?  Can't wait to hear.  :-)
>
> Bill, W6WRT


The 813 was way underated as are many other tubes of that era, my own use of 
them over decades indicates an ICAS Pd of 200-250W is more realistic and use 
a little air on the glass. I show just a little color on SSB voice peaks at 
1200W for 4 tubes. On CW in a contest enviroment there is a fairly steady 
dark red.

As an AM linear at 350W carrier reducing idle current into deeper Class B 
reduces color to almost nil while maintaining good linearity on the monitor 
and SA.
This works well with other amps such as the Clipperton L.

The 803 is another tube that is way underated for Pd.

Carl
KM1H