Hi Jerry,
Yes, you certainly do need bifocals.
> >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.
As I said, scaling won't work. You assume, quite incorrectly, the
tube provides the same input impedance on six as it does on 160.
Not a chance.
The 8000 pF you used is 11 ohms on 160. If we place that in
parallel with the correct inductor, the Q is somewhere around 10 on
160. There must be some specific reason you selected a Q of ten,
I wonder what it was?
> Tom if your going to quote me make it complete. AGAIN I SUGGESTED ONE TO
> SCALE THESE VALUES. Bifocals stink huh |-)?
OK, then me repeat it and maybe you will understand what I wrote.
The lead lengths and stray capacitances, as well as the much
different grid impedance, will certainly change the input impedance
of the tube a lot on six meters. There would be a snowballs chance
in hell the values that worked on 160 would work on six, when
scaled to six meters.
Is that clearer?
>
> 73, Jerry krr2ak@juno.com
> [text|uuencode|59kb ea]
> 'Our people are warriors, often savage, but we are also many
> other pleasant things'
>
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73, Tom W8JI
w8ji@contesting.com
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