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Author Topic: #11 wire for toroid  (Read 2265 times)
N6HPO
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Posts: 39




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« on: May 27, 2010, 07:41:36 PM »

Hello Everyone,

I am in the process of getting the parts together for a rotatable dipole that I'm making. I am trying to find a retail outlet that has # 11 enameled magnet wire.

There are just a few places that I have found that carry it; those that do will only sell me $125.00 worth. I need just enough for a 2" diameter, 1/2" thick doughnut! The #11 has been suggested to withstand about 400 watts.

Can anyone help me? If # 14 wire will do about 250 watts, if I had to, I could use #12 wire to wind the toroid.  Undecided

Still, I need such a small quantity of wire. Any supplier sell 25 foot rolls...or less?  Huh

Many thanks for taking the time to respond!

Alan...N6HPO
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N3OX
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Posts: 8847


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« Reply #1 on: May 27, 2010, 08:17:48 PM »

There are just a few places that I have found that carry it; those that do will only sell me $125.00 worth. I need just enough for a 2" diameter, 1/2" thick doughnut! The #11 has been suggested to withstand about 400 watts.

By who, and how did they arrive at that?   I can't imagine a toroidal loading inductor wound on a 2" toroid that would be limited by the copper loss difference between #14 and #11 wire.  I would think that core heating would dominate in either case.  A quick EZNEC estimate of the RF resistance of the two sizes on 7MHz suggests that #14 wire has a RF resistance of about 40 milliohms/foot and #11 is about 28 milliohms/foot at that frequency.

Seems like you're going to peak out at Q = 200-250 for an iron powder toroid. If that's the case, an estimate I've done here suggests that if you use #14 wire, less than 10% of the resistance is wire resistance.

What I actually did was grabbed a #2 toroid for a low pass filter I'm building... it's 2.9uH, about 130 ohms at 7MHz.   If we assume Q=200, that's 0.65 ohms total loss resistance.  It's got about 10 turns of wire, and that's about 15 inches of wire.   If my EZNEC resistance estimate for #14 is correct then the wire resistance is only 0.05 ohms, about 8% of the total resistance.  If you used the #11, the wire resistance would be 0.035 ohms and about 6% of the total for this particular coil.    The percentage should get better with higher reactance at least until you start to get close to stuffing the core as full as you can get in a single layer.

I'm fairly certain that you'll cook the core long before the wire heating becomes a problem if you use #14 if you have that on hand.  If you're too worried about it you could sling some teflon sleeving over #12 but I feel like that will just make it heavier and hard to wind for no good reason.

73
Dan

« Last Edit: May 27, 2010, 08:24:01 PM by Dan » Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W5FYI
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Posts: 1045




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« Reply #2 on: May 27, 2010, 08:47:27 PM »

It's odd that you would need such a large conductor for a balun. Nonetheless, check with your local industrial motor repair shops. Chances are they have the odd-size wire gauges, and might just give you the few feet you need. You could also twist two AWG14 wires together to make a #11 equivalent conductor.

You can buy short lengths of #10 house wire at any hardware store. Although it's not going to be magnet wire, you can buy insulated wire, or you could run uninsulated wire through the appropriate size of Teflon spaghetti. (I'm told that some model airplane hobby shops sell Teflon fuel line in various sizes). GL
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AC2Q
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Posts: 348




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« Reply #3 on: June 03, 2010, 10:02:26 AM »

Alan,
#14 Insulated House Wire will handle Legal Limit all day long assuming a reasonable Impedence Match.

Yes, Ye Trolls...I said Legal Limit All Day Long, come and get me  Wink

AC2Q


Hello Everyone,

I am in the process of getting the parts together for a rotatable dipole that I'm making. I am trying to find a retail outlet that has # 11 enameled magnet wire.

There are just a few places that I have found that carry it; those that do will only sell me $125.00 worth. I need just enough for a 2" diameter, 1/2" thick doughnut! The #11 has been suggested to withstand about 400 watts.

Can anyone help me? If # 14 wire will do about 250 watts, if I had to, I could use #12 wire to wind the toroid.  Undecided

Still, I need such a small quantity of wire. Any supplier sell 25 foot rolls...or less?  Huh

Many thanks for taking the time to respond!

Alan...N6HPO
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WB6BYU
Member

Posts: 13243




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« Reply #4 on: June 03, 2010, 12:11:26 PM »

I agree - look for a local shop that rewinds motors or such.  They will have magnet wire in many different
sizes and will probably sell you what you need (if they don't just cut off a chunk and give it to you.)
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AD6KA
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Posts: 2237




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« Reply #5 on: June 08, 2010, 11:41:50 PM »

Quote
...if they don't just cut off a chunk and give it to you.

Good luck with that. I once asked for 3 feet of enameled #18 magnet
wire off of a 500 foot spool, and the store said no.

Electronic City in Burbank, CA. Never been there since then.
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WB6BYU
Member

Posts: 13243




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« Reply #6 on: June 09, 2010, 08:24:22 AM »

If they are in the business of selling 500' spools of wire, likely not.

But if they are in the business of rewinding motors they will be using the wire off the spools, not
selling it by the spool, and you stand a better chance of getting some.
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