[AMPS] 572b's as a robust oscillator

[Jerry Devine]

>>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
[text|uuencode|59kb ea]                                                  
        'Our people are warriors,  often savage, but we are also many
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