[UK-CONTEST] Stacking toroids

[Derek Thom]

Chris,

Some years ago I built an all-band L-match capable of handling 400W with 
ease and incorporating a 4:1 balun so that I could feed a doublet with tuned 
feeders.  Can't remember where the design for the toroidal balun came from 
but I do remember winding each 2-inch toroid with a fibre based insulating 
tape (not the usual plastic stuff) and then winding more tape over the stack 
of 3 toroids.

Feeding a 132ft doublet with 45ft of feeder, the balun never became warm 
even on 160m.

Good luck!
73,
Derek G3NKS

----- Original Message ----- 
From: "Chris G3SJJ" <g3sjj at btinternet.com>
To: "UK Contest Reflector" <uk-contest at contesting.com>
Sent: Monday, March 05, 2012 4:23 PM
Subject: [UK-CONTEST] Stacking toroids


>I want to stack a couple of T300-2 toroids for a project I am working on. A 
>couple of questions -
>
> 1 - Should each toroid be wrapped separately or should the non-painted 
> side of each touch each other and then the whole unit wrapped?
>
> 2 - The finished component will be a 4:1 transformer to match a 160m 
> inv-L. Currently I am using one core which already had 14 turns bifilar 
> wound as
> 4:1 balun but I have just altered the connections, so that one free end is 
> grounded, the other free end goes to a series C and the centre tap goes to
> the Tx. It works well, tuning nicely with the C, although the core 
> saturates at a specific power area, hence stacking. What are the relative 
> merits
> are a straight winding against bifilar.
>
> Chris G3SJJ
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