[Amps] 813 efficiency

[Carl]

Ive restored a 1954 QST cover project 813 TX and get around 60% Class C on 
10M at 2200V and it increases to a bit over 70% on 80/40. Grid current on 10 
and 15 isnt as high as Id like.

A modified Globe Champion with an 813 runs about the same at 1000V on 10M 
but with drive right to the max by replacing the 2E26 with a 6146 with 
increased screen voltage.

A 4X 813 GG linear Amp runs a solid 60% on 10M but the HV is 3200V under 
full load and the input and output circuits were tweaked to get there.

The old tech glass tetrodes and pentodes liked their HV, the 4-1000A is a 
prime example.

Carl
KM1H



----- Original Message ----- 
From: "Mike Lord" <k4elv at bellsouth.net>
To: <amps at contesting.com>
Sent: Wednesday, February 20, 2013 3:18 PM
Subject: [Amps] 813 efficiency


> Some time ago (maybe 2 years) there were comments filed on this site 
> regarding increasing the efficiency of the 813 tube on 21 - 28 mhz.  I've 
> looked through my history of this group but failed to find a reference.  I 
> also checked some GE Ham News articles that I've saved.  I realize the 
> tube wasn't designed for this spectrum.  However, I do seem to recall some 
> references being made on this site based upon personal experiences.  I 
> really don't intend to waste the groups time, but I sure would appreciate 
> any circuit suggestions that would lead to increased efficiency of this 
> tube.
>
> 73, Mike K4ELV
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