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

[D. Platt]

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