I may be obsessing.

When putting trifilar winds around a toroid, does it matter how the
three wires are twisted before they are wound?

The easiest way is to just twist the two "outside" wires around the
"center" wire. The outside wires would wind up a little longer. It
would just a moment longer to plait or braid them, which would make
them equal length. Does it matter?

Ken KC2JDY


Ken
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Yes it does matter, if you are trying to hold a particular Zo to
get maximum bandwidth. I use ribbon cable or multiwire
rotator cable to get the spacing between the wires to be
consistent. The bandwidth is MUCH wider than you
get with twisting or braiding.

Rick N6RK
"Ken" wrote in message
...
I may be obsessing.

When putting trifilar winds around a toroid, does it matter how the
three wires are twisted before they are wound?

The easiest way is to just twist the two "outside" wires around the
"center" wire. The outside wires would wind up a little longer. It
would just a moment longer to plait or braid them, which would make
them equal length. Does it matter?

Ken KC2JDY


Ken
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remove "zz" from address)

On Mon, 29 Nov 2004 12:23:53 -0500, Ken wrote:
Does it matter?

Hi Ken,

The technique matters at the peripheries of what you seek to
accomplish. The tight conjunction of wires (the are properly
transmission line) reduces their characteristic Z. This is a positive
attribute if you seek that characteristic. Recall that the best line
Z is found through the math of finding the root of the product of the
two Zs being transformed (in other words, does that tight conjunction
lend itself to this root of the product).

However, there are many topologies in winding these items, and not all
conform to this technique. For some, you want separation so that the
loss and isolation characteristics are maximized at the margins of
frequency operation (typically high end use).

So, yes it matters. The real question is: Does it matter for you?

73's
Richard Clark, KB7QHC

In message , Ken
writes
I may be obsessing.

When putting trifilar winds around a toroid, does it matter how the
three wires are twisted before they are wound?

The easiest way is to just twist the two "outside" wires around the
"center" wire. The outside wires would wind up a little longer. It
would just a moment longer to plait or braid them, which would make
them equal length. Does it matter?

Ken KC2JDY


Ken
(to reply via email
remove "zz" from address)

From my experiences with winding small torroids for CATV, the bandwidth
(at least at the HF end) definitely better when you interwind
(interleave) the windings.

We put this down to the fact that it probably minimises the capacitance
between the turns of the same wire. For example, suppose you use red,
green and blue wires. As you progress around the circumference, you have
a regular sequence of red, green, blue - red, green, blue etc etc. You
will never have a red adjacent to a red etc.

Note that, in principle, you could wind bifilar and trifilar using bare
wire, and (with care) never have the adjacent turns touching.

One manufacturer used to use special bifilar and trifilar wire (like
miniature flat twin (and triple).

If you do want to twist, we found that twisting the wires would give you
a more consistent (and lower) characteristic impedance. This is probably
because, if the wires are kept in good contact with each other, the
capacity per length is consistent. However, there is no point in
twisting any more than is sufficient to keep the surfaces of the wires
in intimate contact.

I never thought of braiding (also called 'platting' in the UK). Sound
like hard work to me!

Ian.

--

On Mon, 29 Nov 2004 17:42:15 GMT, "Rick Karlquist N6RK"
wrote:
Yes it does matter, if you are trying to hold a particular Zo to
get maximum bandwidth. I use ribbon cable or multiwire
rotator cable to get the spacing between the wires to be
consistent. The bandwidth is MUCH wider than you
get with twisting or braiding.

I happen to have some "rainbow" 28-ga. ribbon that I could try.

What happens when I have gone once around the toroid and need to put
a bunch more windings on? Just lay it on top of the first layer
without regard to the position of what is under?

Ken KC2JDY

Ken
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On Thu, 02 Dec 2004 16:49:25 -0500, Ken wrote:

What happens when I have gone once around the toroid and need to put
a bunch more windings on?

Hi Ken,

Get a bigger toroid.

73's
Richard Clark, KB7QHC