[Elecraft] 100 Watts or 500 Watts

[george fritkin]

Just  some simple questions.  Why use an 813 for an amp.   125 watt plate 
dissipation,  50 watts of heater power, and a large physical size.  The "modern" 
572b uses 25 watts for heater power has 225 watts dissipation and is cheap. I 
have two SB200s they put out 800 watts PEP and they can be bought real 
inexpensive. Every couple of years I stick new tubes in them for kicks and use 
the pulls as spares or "presents".

I love building, but I am practical too.  But have fun guys and please be 
careful. 

George, W6GF 






________________________________
From: Ron D'Eau Claire <ron at cobi.biz>
To:
Sent: Wed, December 22, 2010 9:20:47 AM
Subject: Re: [Elecraft] 100 Watts or 500 Watts

Time to dig out some old ARRL Handbooks from the 60's. My '62 Handbook has a
nice 813 grid driven amp that runs Class C for CW and AB2 for SSB, the
famous "one band kilowatt" amplifiers using a pair of 813's (each band had
its own RF 'deck' with a common power and metering circuit so each amp could
be pre-tuned and ready to go at the snap of a relay or switch) and a
Kilowatt grid-driven 4-400A amp, in addition to the usual assortment of
ground grid amps. 

A builder today may need to 'beef up' the pi-network output filter to meet
modern spurious emission standards (typically for the second harmonic) or
use an outboard half-wave filter for each band for that purpose. 

Ron (radios should glow in the dark) AC7AC

-----Original Message-----
On 12/22/2010 11:30 AM, a lister wrote:

Grounded-grid is not the only way to design a tube amplifier. Although a
traditional grid-driven circuit is a little more complicated, it's one way
to get more gain.

Amen to that. When I was little, "grounded grid" was vaunted as the way to
use triodes without needing neutralization, even though one took a real hit
on gain. Unfortunately, the old-time big amps that use/used several triodes
in parallel in grounded grid still have a tendency to "take off."

The 813 and the various Eimac ceramic tetrodes are wonderful tubes, and if
one can go high voltage low current, they are excellent performers. Again,
when I was young, solid state devices wouldn't function in the VHF/UHF
region, and the 4CXnnn series were practically a necessity. Need I refer to
the beautiful amps vended by one of the early moonbounce guys?

I for one would like to see designs using these tubes. Not all of us need
linear/linearized amps.

John Ragle -- W1ZI

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