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Re: [Amps] SB-220

Subject: Re: [Amps] SB-220
From: R.Measures <>
Date: Thu, 4 Nov 2004 11:35:42 -0800
List-post: <>

On Nov 4, 2004, at 9:39 AM, Bill Turner wrote:

On Wed, 03 Nov 2004 13:58:51 -0500, Will Matney wrote:

Now to me, if the lead(s) length is correct, and the gain high enough,
the internal capacitance of the tube along with the inductance of the
lead(s) could make up a VHF oscillator.


One other factor not mentioned is the Q of the VHF circuit, which has
a great effect on gain.  If the VHF Q is very high, oscillations are
almost guaranteed.

Indeed, Bill. The higher the VHF Q at the anode circuit's resonance, the higher the gain at that frequency, and the greater the chance of regeneration. The relationship between VHF-Rp, VHF-Q, and VHF gain is that all are proportional.

VHF Q is usually not known in most amplifier
circuits, and having a parasitic suppressor circuit is just added
insurance.  I wouldn't be without one.

Bill W6WRT

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Richard L. Measures, AG6K, 805.386.3734.

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