[ARC5] Selectivity improvement in ARC-5 receivers.

[D. Platt]

Tangential to this conversation, I'm looking at how to lower the 
coupling of the IF transformers within the BC-639( ) receivers.  The IFs 
in those are documented to be over-coupled to provide for a wide 
bandwidth.  Unlike the transformers in the ARC-5 and SCR-274N receivers, 
the structure that Bendix uses is more perplexing.  As things unfold, 
I'll be asking questions of you all.  Its more of a mechanical issue 
that electrical, of course.  It appears that the transformer is built on 
two vertical, parallel plastic tubes, with the windings high on one side 
and low on the other.  What I don't know, is how far down the tuning 
slugs go and do the electrically "overlap".  I don't see why they would, 
however.  It also appears that the best way to provide a decrease in 
coupling or isolation of the windings would be via a mid-point shield of 
some sort.  That's what I'm looking at, now.  Thankfully, these IFTs 
come out easily.

Jeep - K3HVG