EMRFD Message Archive 4471

Message Date From Subject
4471 2010-03-26 10:42:11 Glen Leinweber toroid winding with large dia. wire
Not ANOTHER toroid winding post! ;-)

Reading EMRFD (or was it SSD?) that it may be better to
use slightly smaller wire, rather than try to tightly wind a
large diameter copper wire around a small toroid. I believe
that the thought was that a coil might have more stable
inductance if its wire conformed to the toroid form more
closely - using too-large wire makes it very difficult to
wind tightly.
It occurred to me that stranded wire might be more
malleable when toroid winding. So tried an experiment:
wind two toroids, one with unstranded #18 magnet wire,
and compare with another wound with a bundle of
smaller magnet wires having the same cross-section area.
I can't measure how stable the inductance might be, but
I can measure coil Q and inductance.

The toroid form is a T50-6. Incidentally, looked up AL
values on the web, finding values between 40 - 47 for
this core.
#18 magnet wire has diameter of 0.403" and 0.0064
ohms-per-foot. #28 magnet wire has diameter of 0.0126"
and 0.065 ohms-per-foot...so a bundle of ten parallel
#28 wires should have about the same resistance as a
single #18 wire. Paralleled ten #28 together, and twisted
them in a drill. This makes a bundle larger than a single
#18 wire, so you can't get as many turns on a toroid. I
managed to get 12 turns of this bundle onto a T50-6.
I could easily wind 12 turns of #18 onto a T50-6, but
it took considerably more effort, and I suspect the #18
got a little work-hardened after winding.

In a Q-measuring fixture, measured both @ 8MHz, and
@ 18 MHz.

at 8 MHz:
bundled inductance 0.622 uH, Q=125
#18 single: 0.659 uH, Q=184
at 18MHz:
bundled inductance 0.651uH, Q=167
#18 single: 0.692 uH, Q=244

These inductances all work out to a range of 43-48 for the
"AL" winding factor - seems to fit the accepted range of
40 - 47 published on the web. Self-resonant frequency of
sold #18 was 92 MHz., the bundled toroid was 100 MHz.

Any conclusion?
The bundled wires DO wind a lot easier than #18 single,
conforming to the toroid nicely. I'd think a coat of Q-dope
would fix them down even more. But it seems that you
take a hit on coil Q - the single wire seems better electrically.

Was surprised to see self-resonant frequency of the bundled
toroid higher than the solid #18 toroid. It was more tightly
wound, with turns more tightly adjacent to each other, while
the #18 solid had its turns more spread out over the toroid
form.
4472 2010-03-26 11:52:58 Dave A simple toroid question
If I am building something that specifies winding a toroid with X turns
of 28 gauge on a T-37 core, what impact will it be if I use 30 gauge
wire instead. It always seems like I don't have the exact wire gauge
specified but have something close.


[Non-text portions of this message have been removed]
4473 2010-03-26 11:58:39 KB9BVN Re: A simple toroid question
Virtually none.


----- Original Message -----
4474 2010-03-26 12:10:41 Leon Heller Re: A simple toroid question
4476 2010-03-26 16:05:27 Dave Re: A simple toroid question
Thanks for the replies so far. I suspected the exact wire size didn't
matter too much at least for low power. However, is the same true for
bifilar and trifilar wound toroids (such as baluns)? Do I have to
adjust the turns per cm or something like that.

Dave

Leon Heller wrote:
>
>
>
4477 2010-03-27 04:03:47 Leon Heller Re: A simple toroid question
4478 2010-03-27 19:03:42 Kerry Re: A simple toroid question
A bloke named Peter Lefferson managed to apply science to the design & construction of bifilar twisted lines of any desired Zo (within practical limits) in 1971; see his paper "Twisted Magnet Wire Transmission Line".

Published by the IEEE (PHP-7, #4, Dec 71).

A good read.
4479 2010-03-28 11:12:46 Gian Re: A simple toroid question
4480 2010-03-28 12:55:41 Kerry Re: A simple toroid question
Would it be possible to have a copy of such paper loaded in Files or shared via mail ?

*******************

I think there would be copyright problems in doing this; otherwise I would be delighted to share it.
4481 2010-03-28 13:05:32 Neil Douglas Re: A simple toroid question
4482 2010-03-28 13:11:21 Kerry Re: A simple toroid question
Good one, Neil; the first link is to the paper I described.

Your link is incomplete; let's try this;

http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_
148_71.pdf

Kerry.
4483 2010-03-28 13:16:21 Kerry Re: A simple toroid question
The problem with the links must be a quirk of Yahoo; my attempt was no better. :(

They work fine if you copy-&-paste.
4484 2010-03-28 13:52:53 k5nwa Re: A simple toroid question
<
http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_148_71.pdf
>

At 03:08 PM 3/28/2010, you wrote:
>
>
>Good one, Neil; the first link is to the paper I described.
>
>Your link is incomplete; let's try this;
>
><http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_>http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_
>148_71.pdf
>
>Kerry.
>
>

Cecil
k5nwa
< www.softrockradio.org > < www.qrpradio.com >
< http://parts.softrockradio.org/ >

Never take life seriously. Nobody gets out alive anyway.
4485 2010-03-28 13:52:55 Sam Morgan Re: A simple toroid question
Kerry wrote:
> The problem with the links must be a quirk of Yahoo; my attempt was no better. :(
>
> They work fine if you copy-&-paste.
>
it's the line wrap guys,
the last part of long urls gets wrapped around and you have to copy/paste it to
the end of the 1st line in ur browsers

click this:
http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_

copy and paste this on the end of the above line in ur browser:
148_71.pdf
--
GB & 73
K5OAI
Sam Morgan
4486 2010-03-28 13:58:08 k5nwa Re: A simple toroid question
Look it up on Google, there are various methods
to minimize the breakup of a URL even with line breaks in you mail client.

My favorite that works the best is;

< URL >
There are 4 spaces between the brackets, then you
paste the URL in the center of the four spaces,
this works even with URLs that are several lines long.


At 03:52 PM 3/28/2010, you wrote:
>
>
>Kerry wrote:
> > The problem with the links must be a quirk of
> Yahoo; my attempt was no better. :(
> >
> > They work fine if you copy-&-paste.
> >
>it's the line wrap guys,
>the last part of long urls gets wrapped around
>and you have to copy/paste it to
>the end of the 1st line in ur browsers
>
>click this:
><http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_>http://www.physics.princeton.edu/~mcdonald/examples/EM/lefferson_ieeetphp_7_
>
>copy and paste this on the end of the above line in ur browser:
>148_71.pdf
>--
>GB & 73
>K5OAI
>Sam Morgan
>

Cecil
k5nwa
< www.softrockradio.org > < www.qrpradio.com >
< http://parts.softrockradio.org/ >

Never take life seriously. Nobody gets out alive anyway.
4489 2010-03-29 05:24:50 Gian Re: A simple toroid question