[Amps] More parasitic choke questions

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Fri, 30 Jul 2010 19:36:35 -0400, "Carl" <km1h at jeremy.mv.com> wrote:

>
>The coil must be self resonant at/near the parasitic frequency. 

REPLY:

In all my years as a ham, this is the first time I have heard anyone
say that a VHF parasitic suppressor coil MUST be self-resonant. Where
did you get that from? Did you think of it yourself?

Don't get me wrong - I'm not saying a self-resonant coil won't work,
only that it isn't necessary. Just to be sure I hadn't missed
something, I pulled out my 2010 ARRL handbook and re-read the section
on VHF suppressors. Nowhere is self-resonance mentioned. 

Here is what the handbook has to say about the coil:  "Lz [the
suppressor coil] should be just large enough to constitute a
significant part of the total parasitic tank inductance (originally
represented by LP), and located right at the tube plate terminal(s)."

Note they say "...just large enough". No requirement for
self-resonance or any particular inductance value. 

So I ask again, where did the idea that it MUST be self-resonant come
from?

73, Bill W6WRT