[Amps] More parasitic choke questions

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Wed, 28 Jul 2010 15:11:22 +0200, "DF3KV" <df3kv at t-online.de> wrote:

>Why is that [not absoring any HF power] impossible?   
>On HF the resistor is almost shorted out by the inductor.
>The power absorbed will be less then 0.5% of the desired HF with a typical
>amp.

REPLY:

You answered your own question. Almost shorted out is not the same as
shorted out, and .5% is not the same as zero. 

Some people have a bad habit of taking a very small value and rounding
it off to zero. Sometimes it doesn't matter, sometimes it does. In
this case, it does. 

I'll say it again:  A conventional VHF parasitic suppressor is going
to dissipate significant HF energy when running on the higher HF
bands. The trick is to get the inductance low enough to bypass most of
the HF energy around the resistor while still having enough inductance
to effectively suppress the parasitic. The balance between the two is
not super critical but it often takes some cut and try to get it
right. Even commercial amp makers don't always get it right as
evidenced by many burned up suppressor resistors. 

73, Bill W6WRT