[ARC5] BC-221 question

[Hubert Miller]

Possibly most people think "adjust load coil ( or tuned load circuit ) for maximum selectivity and call it a day".
The National HRO has this load tuned circuit variable; this is how overall selectivity is varied in that receiver.
In addition, the BC-348 manual has you align the secondary ( only on the "old style BC-348 filter" ? ) for 
desired selectivity instead of just "tune for max" type instructions.
-Hue Miller