[Amps] R. MEASURES PRAYERS ANSWERED

[R L Measures]

On May 31, 2006, at 6:37 PM, Vic K2VCO wrote:

> R L Measures wrote:
>
>> Does this involve keying the amplifier with zero drive, and tuning  
>> the Tune-C and Load-C throughout their ranges?
>
> Summary:
>
> [think of a grid-driven amplifier with link-coupled input and output]
>
> Short the grid tank coil so that there's no possibility of tgtp  
> oscillation at operating frequency.

Shorting the cathode-grid tuned-input of a g-g amplifier shorts the  
VHF feedback path that supports parasites.

> Replace fixed bias with grid leak of 10-20K.  Disconnect any load  
> from output.  Reduce plate/screen v so dissipation rating isn't  
> exceeded.  Adjust grid tuning capacitor in steps from max to min;  
> at each step, tune plate capacitor through full range.  Any flicker  
> of grid current or dip or flicker in plate current indicates  
> oscillation.  If found, use absorbtion wavemeter to determine  
> frequency.

With the feedback path shorted, the amplifier is sure to be stable.   
As I see it, this procedure is some dude's fable.

thanks, Vic
> -- 
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>

R L MEASURES, AG6K. 805-386-3734
r at somis.org