>>Phil W2GE 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??
Not sure, Can not find any data here on the 572-b in regards to this.
I'm sure it's writen down some where, I just haven't found the hiding
place...
But I can tell you that 8000pf and it shunted by a .1µh inductor then
placed across the input to ground works on 160m. Fair enough for tube
type exciters pushing a pair of these on 160m. I'd say scale it to 50mhz.
Oughta be close.
>>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?
>R. L. Measures, 805-386-3734, AG6K
>Beats me. I know of no way to neutralize a grounded-grid amplifier.
Try reading Radio Handbook 23rd edition pg 15-12 Topic Grounded Grid or
Cathode Driven RF Amplifiers and pg 16-2, 16-3, 16-7, 16-8, 16-9. Also
see pg 14-26 as well as pg 18-25.
Good luck.
73, Jerry krr2ak@juno.com
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