Hello, does anyone have any information on the #66 & 67 plug in coils for the National SW-3? These coil cover the broacast band. I have the winding information and wire size but there is a reference to a tap on the primary coil of the detector for both sets of coils. What this tap does I do not know. I suspect it forms a resonant circuit with a capacitor attached to it perhaps? Thanks
Tom
KA1NVZ

Hello Tom:
When you first posted your request I looked at my stash of SW-3 through 5 coils and information. I saw the problem but I did not have an answer.

Today I ran across something I think will answer yoru question. Go to the BAMA boatancher site look at the multiple listings under SW-3 and then down load the PDF named DCSW-3 which is a schematic of one version of the SW-3 drawn using a modern cad software program- IT'S LEGIBLE! by Bob Mattson W2AMI

Have a look at how Bob drew the bandspread and the general coverage coils on his drawing. For the general coverage coils the coil secondary is not taped and the two coil leads connect to pins 1 and 2 on the plug in coil form. For the bandspread coils, the secondary winding is tapped. The cold end of the coil gets connected to coil form pin 2 and the tap gets connected to pin 1. The hot end of the coil goes to a grid cap connector and this grid cap is used instead of the grid cap attached to the chassis mounted two section tuning cap.

It's pretty simple to figure out if you have Bob's excellent drawing in front of you.

Hope this is helpful

Contact me if you have trouble finding the W2AMI drawing on bama

Bruce KG3Z