[Amps] SB220 Improvements

[2]

>2 wrote:
>
>> **  An early 2, 3-500Z circuit from Eimac's Bill Orr used chokes/caps on
>> the grids.  Heath, Drake and Kenwood copied the idea.  However, I have
>> yet to read an account of Bill Orr's reasoning behind the idea. 
>
>Didn't the 30L1 do this as well?  

**  Good point, Vic.  Yes.  Maybe Bill Orr copied the idea from Collins 
Radio? My take on Orr is that he was more of a merchandiser than an 
innovator.  

>Maybe they all copied Collins.  As I
>understand it, the caps are series resonant with the grid lead inductance at
>some frequency, and -- at least at that frequency -- move the grid potential
>closer to ground, improving stability (again, only at one frequency).  

**  True, however, my guess is that the added XC only cancelled enough 
811A grid lead XL to move the grid resonance up a few MHz.  I tried using 
smaller grid caps on a squirrelly SB-220.  The 220's stability at 110MHz 
seemed to improve only slightly so I began experimenting (1985) with 
lowering the Q of the anode circuit 's 110MHz resonance.  

>The chokes are there to provide a DC path, of course.
>
>73
>Vic K2VCO
>


-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 
www.vcnet.com/measures.  
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