[Amps] Bill's novel idea of parasitic suppression.

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Tue, 13 Apr 2010 02:41:59 -0700, "Jim Thomson" <Jim.thom at telus.net>
wrote:

>
>Ok, between  low C  and high L..... and  at the other extreme, High C.. and Low L... there is an infinite amount of combo's
>that would still resonate on the parasitic freq.   Which combo would provide the widest BW ??   I think it would be the 
>low C, High L  combo.. but not sure ?     Has anybody tried  this b4 ?   On paper, it looks like it would work.... and no
>resistor required.    It would amount to a series resonant tuned circuit... and should suck out the parasitic freq.   

REPLY:

My thinking on the resistor is to broaden the width of the trap. This
may or may not be necessary depending on how much the resonant freq of
the anode parasitic varies with changes in tuning of the pi-net. 

I have not used this circuit yet - haven't needed it - so some
experimenting would be required.

I also had a thought on pre-setting the resonant freq of the trap. I
would lay out the trap with the exact lead lengths and positions it
will have in the amp, then connect a jumper across the open ends. This
will convert it into a parallel resonant circuit which can be
grid-dipped to match the resonant freq of the anode circuit. Then when
the jumper is removed and the trap installed, its freq should be
pretty close to dead on. If anyone has another suggestion for
pre-tuning I would like to hear it.

73, Bill W6WRT