[Amps] Parasitic Suppressor 4-1000A

[Steve Thompson]

Saandy wrote:
> ....yeah! Now, you have arching, like you wanted (HI).
> 
> It probably needs more inductance in the suppressor. According to W6SAI
> (blessed his memory), the 4-1000 needs  4 turns, 16 gage, ½ inch diameter
> suppressor coil with 2 47 ohms 2Watt resistors in parallel.
I'm intruiged by this, and I'm wondering if I'm misunderstanding something.

As I understand it, the tube doesn't oscillate in isolation - it's a 
combination of several factors, including the impedance presented to the 
plate. At some frequency there's an impedance in the wiring from the 
plate to the tune-C and then to ground that allows oscillation. Knowing 
the frequency and impedance allows you to design a suppressor to prevent 
oscillation, but the frequency and impedance can vary a lot with wire 
lengths, component choices and layout - in which case, how can there be 
a specific design of suppressor for a particular tube?

Out of interest, I'd love to know the frequency of oscillation and the 
impedance at the plate at that frequency - anyone out there got an 
oscillating amp and the equipment to measure impedance?

Steve