[AMPS] 572-B Input impedance??

[Phil Levin]

TU Rich!  I am also thinking about trying neutralization on the amp,  Maybe
using a piece of solid copper from a piece of house romex wire (abt 14 or 12
gauge I guess?) and running it parallel to one of the tubes abt 1/2 inch
away??, then to the filament choke and wrap abt 4/5 turns around it  in the
same direction that the choke was wound then to ground???  Does that sound
abt right?  It "takes off" when I key it and turn the tune cap, then the
grid skies and the plate turns red, even if I un-key it at that time it
"takes off".  Phil W2GE

Rich Measures wrote:

> >
> >I need the approximate input impedance for a pair of 572-B's??  I am
> >working on the input matching on an SB-200 to six meters.  Abt 60ohms??
> >
> >Still have parasitc oscillation problem and am suspicious abt the plate
> >RF choke,  dipmeter shows resonance at 52 (MHz)???  Any ideas?? ......
> >
> ... put a thin coat of urethane varnish on wire to hold in place, when
> dry, remove enough turns to move resonance above 60MHz.  //  At VHF, I
> would not try to use VHF suppressors.
> .
> -  later,  Phil
>
> Rich...
>
> R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures


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