[Elecraft] On hand-twisting wires for bifilar windings...

[Tom Hammond]

Hi Folks:

Upon Dave, KK7SS', suggestion, I'm posting this message to the reflector 
for the possible benefit of newbie builders who are agonizing about how to 
get the proper amount of 'twist' into the wires they're winding for a 
bifilar-wound transformer, such as those used in all the Elecraft ATU's and 
the KPA100.

Dave wrote:

>Another question..
>
>For the KXAT1, T1 uses a pair of wires, twisted together at 4 tpi. Having 
>done this before, and having messed it up at least three times, do you 
>have a method than can be done by hand that works well??
>
>I'd use a drill, but my eldest boy borrowed it and (naturally) can't find 
>it. If not, I'm going to try by using the same method I use to braid my 
>daughters hair

Heheh...

Well, I'd already taught myself to do it long before someone else brought 
up the subject of using a drill motor... MUCH too easy for me anyway... If 
there's a difficult way to do it, I'll probably find it.

The way I do it is to place both wires together, side by side and make a 
couple TIGHT twists at one end, and for no more than 1/2"-3/4" of the 
length. These are JUST to hold the wire ends together and they're CUT from 
the final product once it's been more properly wound.

I ensure that each wire in as straight as I can easily make it, and I then 
hold the twisted end between my thumb and next two fingers with one wire 
extending back between the thumb and forefinger and the other wire 
extending back between the forefinger and the middle finger.

Next, I grasp the twisted end with the other hand and continue twisting on 
it AS I pull it away from my fingers. This allows me to impart a measured 
twist to the wires out ahead of my fingers while allowing the free ends of 
the wires to UNtwist, in response to the twisting I'm doing up front.

If you secure the untwisted wire ends, the twist you impart at the front 
will try to cause the loose wires to 'take a set' and this is something you 
don't want to happen. It's just like when the Boy Scouts used to make their 
own rope... if you've ever seen their rope-making machines, one end 
imparted the twist and then the twist was released at the back end.

This method works great for me... been using it for a couple decades, I 
guess. It's a helluva lot longer to explain that it is to DO!

Hope this helps.

73,

Tom  N0SS

p.s.

Yes, you CAN use a drill motor to do the winding, but, generally, by the 
time you get the drill out and set up, I can have the wires all twisted by 
hand and I'm on to more building.