Winding high power xmit toroids

Michael McCarthy, W1NR w1nr at EECORP.COM
Fri Jun 25 22:36:28 EDT 1999

It's been nearly 10 years since I wound one for a 4-1000 amp but
here is what I recall I did:

Lane Zeitler wrote:

> 1. Do the two toroid cores need to be insulated from each other or can I
> just place them tightly next to each other and then wrap them as a package?

   Glue them together with super glue or a few drops of epoxy.  Don't get
too generous with the epoxy.  I had a plate choke held to a Plexiglas rod
with some epoxy and it melted and exploded all over the inside of the amp.
The amp still worked fine...

> 2. What is the best thing to use to hold them together as one piece? Some
> kind of fiberglass tape? Can I buy the stuff at Home Depot?

   3M fiberglass tape.  I have seen it at electrical supply houses.  For sure
at Newark ($$$).  3 layers of tape, then 3 coats of GC electronics polystyrene
Q dope (available from Mouser, Newark, etc.)

> 3. I am using teflon insulated wire. Do I need to insulate the cores before
> applying the wire?

   Absolutely.  As above with glass tape and Q dope.

> Any info greatly appreciated. This is my real first attempt at using toroid
> coils for 160, 80 and 40 meters instead of the regular air wound type a la'
> B & W style.

   On 160, 80 and 40 you should be fine.  I would use three cores if I was
planning on 20 and 15.

Mike, W1NR

**************** Give Every Man His Dew **************
Michael A. McCarthy, President
Everest Engineering Corporation, Consultants
4 Barnes Circle, Marlborough, MA 01752
(508) 460-6737, FAX (508) 460-7951
mailto:w1nr at

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