[Amps] How do I determine Class

[R.Measures]

On Sep 2, 2004, at 9:07 AM, Will Matney wrote:

> Bill,
> I was reading about this a while back. If I recall, the spacing 
> between the screen grid and the anode in power tetrodes help control 
> secondary emission reaching the screen from the anode. If you recall 
> the innards of a power tetrodes, the screen and control grid are in 
> precise alignment and are close together. But the anode is a good 
> distance beyond the screen. In pentodes or beam tetrodes (most which 
> still are called pentodes) of course, the suppressor grid or the beam 
> plates keep the secondary emission from reaching the screen being at 
> ground potential. I'm pretty sure I was reading this in either the 
> Care and Feeding texts by Eimac, or in the RCA Transmitting Tube 
> manual. One of the two spoke about this same thing.
>
> This makes me wonder, why don't more if any amateur amps use power 
> pentodes?

Compared to tetrodes, pentodes are more difficult to manufacture, which 
translates as more costly and their sockets are even more so. The 
largest pentode made is the 5cx3000A.  It costs a bunch more than a 
4cx10,000D, it puts out only c. half as much suds, and, more 
importantly, it does Not have handles.

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org