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Re: [Amps] Parasitic Resistors

To: <>, <>
Subject: Re: [Amps] Parasitic Resistors
From: "Tom W8JI" <>
Date: Wed, 28 Jun 2006 11:53:52 -0400
List-post: <>
> I had used some metal film that RF Parts sells as 
> non-inductive 'flame proof'.
> When you get to talking to them, the 'engineer' will tell 
> you that they are
> slightly inductive.  I am curious if 'slightly inductive' 
> is too inductive for
> this application.

It depends on the resistor, but I would not use them.  In 
many cases they are too inductive.

Most parasitics in tubes like the 3-500Z actually occur up 
around 180-200MHz. The exact frequency varies with grid lead 
to chassis length.

You can series tune the reactance of small metal film 
resistors out  with a series silver mica capacitor. This 
causes current to shift into the resistor much faster than 
it does with a simple parallel R/L system as frequency is 
increased. This will greatly reduce dissipation at the 
desired frequency and increase dampening at VHF.

Be really careful about blanket claims the inductance won't 

You might have a look at:

73 Tom

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