[AMPS] Switches

[Tom Rauch]

Richard Measures wrote:

> Reasons for using a tetrode in grid-driven configuration is:
> 1.  a power gain of up to 200 vs. the triode's gain of c. 15. 
> 2.  The AB1 neutralized  grid circuit (variable-L resonant with grid-C) is
> a Natural for general coverage.  However, achieving general coverage with
> a G-G triode is not easy.  Maintaining a tuned input Q of approx.  two
> over 9 bands is difficult.  

The amplifier would not be type accepted with less than 50 watts 
driving power for 1500 watts out.

 
> >Unless you add negative feedback in the cathode of the tetrode and 
> >use a well-regulated supply, they aren't so clean.  
> > 
> >> Even so, I think it's being far too sweeping to imply that all tetrodes
> >> have worse IMD performance than (all) triodes. There are far too many
> >> other factors in the design and operation of an amplifier.
> >
> >Of course. Some tetrodes are very clean, but then are some 
> >triodes. 
> > 
> Many Tetrode amps are typically cleaner than transceivers.  Also, Eimac's
> IMD specs are 4x better than they appear.  

That isn't true Rich. You have it exactly backwards.

Eimac uses the commercial standard of dB below one tone of a 
two tone test. It is the other companies who use the ARRL 
method, which makes everything look 6 dB better than it really is.

 
> >> There's no doubt that tetrode amps are much less "plug-and-play" than
> >> triodes. It's easier to get things wrong, either at the design stage or
> >> in operation. But if you do get everything right, a tetrode can give
> >> good IMD performance.
> >
> >The key is "getting everything right". Many hams can't tune a GG 
> >triode properly, I'd hate to see what they sound like with the screen in
> >current limiting!
> 
> Assuming that hams are not capable of adjusting  the load-C for a 
> specified  screen-current, is a load of Bandini.  Is Mr. Rauch on some
> kind of superiority trip or what? >

Just being realistic since I operate on the air, rather than just on 
Internet. 
 
> >> >you still haven't solved the bandswitch problem.
> >> >
> >> Which all tube amps share alike.
> >
> >Exactly. That problem remains the same.
> >
> Multronics make a line of suitable insuuctors.  Jennings makes a line of
> suitable capacitors.  With  9-bands, general coverage makes more sense
> than a bandswitch.    

Won't work on six meters with a roller. Far too many series-resonance problems.

That's a $4000 solution that won't work.


73, Tom W8JI
w8ji@contesting.com

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