[MRCA] ARC-5/SCR-274-N IF Coil Mod

[mac]

Jeep,

N3RZU did this some years and reported similar results.  Norm  
accomplished this by juggling the existing spacers in the IF xformers  
as I recall.  Also, see ER #103 for a simple second detector mod that  
should help recove the lost audio level.

Dennis D.  W7QHO
Glendale, CA

*************



On Mar 6, 2014, at 9:15 AM, D. Platt wrote:

> Gentlemen,
>
> I've just completed the preliminaries of modifying a set of BC-454-A  
> IF coils to try and enhance selectivity.  With some very basic  
> information, I have successfully moved the two coils apart about  
> 1/2".  There was some trial and error in doing the first one, but I  
> have found a fairly easy way to accomplish the deed.  Having now  
> done so, and making a comparison of the two sets of coils, I find  
> that selectivity has improved by reducing the measured bandwidth  
> about 2 kHz at the 6db points.  I do find, however, that some  
> additional external AF gain was required as the losses in loose- 
> coupling the IF coils has reduced overall throughput amplitude.  Has  
> anyone else done the above and what were your results?  Also, the  
> coils are marked with the "S" (stabilized) mark, as were other  
> components in this junker set (made available courtesy of W3PWW,  
> Ted).  What, in reality, did the "S" modification intend to do?  I  
> sure can't readily see any component differences??
>
> Thanks
>
> Jeep - K3HVG
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