[Amps] AL811, AL811H or AL572 mods to 6m

[Gudguyham at aol.com]

In a message dated 8/2/2006 3:49:29 P.M. Eastern Standard Time,  
g3rzp at g3rzp.wanadoo.co.uk writes:

That  deals nicely with the output side. But 811s and 572s have very long 
grid  leads, which make them awful bloody things at 30, let alone 50MHz. So  
personally, I wouldn't touch them with a barge pole (as the saying goes) on 6.  I 
suppose you could series tune the grids to resonance, but I have doubts  about 
the resulting efficiency at the end of the day. The spacing is enough  for, I 
suspect, transit time to start coming into play, as well as the gain  
dropping because of cathode lead impedance.
73
Peter  G3RZP



An SB-200 running a pair of 572B tubes will make a good 700 watts output on  
6 meters.  As long as it is run in SSB and the proper type of parasitic  
suppressor is used, it will be stable with proper tune up.  Granted,  they are 
troublesome if you do not finesse properly, however they can be coaxed  to work 
just fine on 6 meters.  Lou