[Amps] A Meeting Ground

[R.Measures]

On Nov 4, 2004, at 12:14 PM, Dennis12Amplify at aol.com wrote:

> Bill,
>
>  I have been reading your posts lately and want to commend you for  
> your
> 'sage' advice.
>
>  I also enjoy Rich's posts but lately he seems to be a bit  cranky.
>
Maybe it's PMS?

>  I guess I would too if I kept having to fight the parasitic  battle.
>
>  I kept thinking about the phase angle thing and realized that for a
> grounded grid amp with .12pfd of plate to cathode capacitance to 
> oscillate at  1000
> megacycles, the uhf circuit gain at that frequency would have to be 
> greater
> than unity at a point where there was either no phase shift, or -/+ 
> 360  degrees
> of phase shift between cathode and anode.
>
>  With the feedback impedance of 1326 ohms at -90 degrees voltage  
> dividing
> with the input impedance of the tube (another vector but a low  
> impedance one),
> It would take a significant amount of stage gain to cause  
> oscillations to
> occur.

Good point, Dennis.
>
>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org