----- Original Message -----
From: "Joe Subich, K4IK" <k4ik@subich.com>
To: "'Steve Thompson'" <g8gsq@ic24.net>; <amps@contesting.com>
Sent: 08 April 2005 19:50
Subject: RE: [Amps] Grid resonance
>
>
> > From: Steve Thompson
> >
> > Mimicing poor grid grounding by adding .5" of 16swg (14awg)
> > wire between the grid ring and the measurement system ground
> > shifts the low impedance point to about 150MHz and the high
> > impedance one to about 1500MHz while the feedthrough increases
> > to a fairly flat -40dBish from 200MHz to 1.5GHz.
>
> I suspect .5" is a bit conservative (short) for some of the
> poor grounding examples I've seen - particularly those that
> use a series resistor for grid metering. Much more than .5"
> and I suspect you're down around 110 - 120 MHz.
Yes - I'm not sure if it's relevant that the impedance goes 'short' at that
frequency - I figure it's the feedthrough (feedback if you prefer) figures
that matter more. Grid and other 'resonances' all come out in the wash if
you look at input to output isolation. I guess I should go back and measure
the phase as well........
Steve
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