[FLWSS] 222 tube amps and more

[Dail, Walter]

 Graham,
  If you are having to drive the amp with 25w then your grid voltage is probably going more negative and cutting the tube
off. Your IMD's may be getting worse. You should never need more than 8-10W  to drive that tetrode on 222. 
 
The resistor swamping technique definitely does work. I use that method on my 2m amp. I can't remember but I may
be using that method on 222 also. I'd have to pull out the cavity to look.
 
Walter K4HV
 

and will take 25w drive now for 350w out. lock the input varicaps for your best input on the  tube rack/tray.
the output  much easier push the plunger in to uhf and and lock in i found my best forward peak around 90 on the counter and have not had to adjust this since. 
 
Another technique which could be tried (experiment)  to broadband the input by swamping the grid  into a hipower noninductive resistor @ 50 Ω  isolating grid bias with a disc cap around 1200pf at input from rig  you would see 50 ohm resistive at the grid, would take some experimenting which is best cap to use . 
I wish i knew the formulas for matching a tube input as measured  and understood the nomenclature a little better  presently trying to make a real 6m input into a sb200 so far the stuff on the internet hasn't worked i looked through some of my arrl handbooks and didn't see any examples other than for a 3cx800   this tube 50 Ω input so not a good example ..
so  i tried the swamping trick on the sb200 closest i ve got to 6m input yet  
 
73 ke4wbo


		 

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