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Author Topic: Piano wire?  (Read 3205 times)
KB3YLQ
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« on: April 21, 2012, 06:51:50 AM »

Just wondering, would piano wire be good for making a 10m dipole? I've got tons of it around. The thickest I carry is #20, which is .045 inch in diameter. It's steel wire, uninsulated. Pretty stiff wire, but coils easily, and I'm used to working with it. The lightest I carry is #13, which is .031 diameter.

Any reason why it wouldn't work?

73,

--Loren
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N3JBH
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« Reply #1 on: April 21, 2012, 07:04:03 AM »

Piano wire is basically high carbon spring steel a few things i think would not be good is the fact that it would rust fairly fast and i think the electrical properties would not be very good. Copper hook up wire sold at most any auto parts store be much better and only reason i suggested that wire was you only need a short piece for 10 meter's and many roll's come in 20 to 30 foot lengths. So you not need to be buying more wire then you need. However ever i find buying wire in 500 foot spools generaly makes me want just play with more antenna's so i buy it that way and enjoy it.... Jeff
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K2DC
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« Reply #2 on: April 21, 2012, 07:09:52 AM »

How would you connect it to the feed line?  I don't think it will take solder.

73,

Don, K2DC
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KB3YLQ
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« Reply #3 on: April 21, 2012, 07:14:59 AM »

Don and Jeff, good points about the solder and rust. Oh well, it was a thought!
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WB6BYU
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« Reply #4 on: April 21, 2012, 08:30:39 AM »

Yes, you can use it, and there may be circumstances when it is appropriate.  I've seen it
used for flexible whips for HTs, for example.

But steel wire has an additional problem in that the RF losses are higher in a magnetic
material than in a non-magnetic one.  That's because the RF has to work harder to
change directions every cycle.  It isn't too bad for wire antennas on HF, but the
losses can be rather high on VHF/UHF.
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KB3YLQ
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« Reply #5 on: April 21, 2012, 08:43:36 AM »

Yes, you can use it, and there may be circumstances when it is appropriate.  I've seen it
used for flexible whips for HTs, for example.

But steel wire has an additional problem in that the RF losses are higher in a magnetic
material than in a non-magnetic one.  That's because the RF has to work harder to
change directions every cycle.  It isn't too bad for wire antennas on HF, but the
losses can be rather high on VHF/UHF.

I hadn't thought of the RF loss in the magnetic wire, but excellent point. Guess that's why I'm a Technician and not a General or Extra yet. Smiley
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W0BTU
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« Reply #6 on: April 21, 2012, 11:48:30 AM »

... steel wire has an additional problem in that the RF losses are higher in a magnetic material ...

Precisely. Much higher.

Besides the extra ohmic losses from the steel's resistivity, you have added losses from the music wire's relative permeability on top of that, and those losses are quite significant.

VK1OD made that point at http://forums.qrz.com/showthread.php?272474-Use-Galvanized-Electric-Fence-Wire-or-Copper-for-Loop&p=2142291#post2142291 . And you can see it on the last table at http://www.vk1od.net/antenna/conductors/loss.htm. The extreme 84% loss of steel MIG welding wire shown in that table is mostly because of its permeability.
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W0BTU
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« Reply #7 on: April 21, 2012, 11:56:33 AM »

Guess that's why I'm a Technician and not a General or Extra yet. Smiley

Don't say that. I've known some pretty smart Technicians over the years. And we run across clueless Extras all the time. :-)

Anyone can decide that they are going to learn, regardless of their license class.
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K0ZN
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« Reply #8 on: April 21, 2012, 10:47:52 PM »


 If it rusts, it will be horrible for RF conductivity; it will essentially turn in to a long resistor !!  Rust has a very high level of attenuation at RF due to the skin effect.

 Generally, steel wire, even galvanized, is bad for anything but a temporary antenna.

73,  K0ZN
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W0BTU
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« Reply #9 on: April 22, 2012, 04:56:51 AM »

 If it rusts, it will be horrible for RF conductivity ...

It doesn't have to rust first for that to happen. See my post #6 above.
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K7KBN
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« Reply #10 on: April 22, 2012, 04:06:35 PM »

Good luck finding a piano tuner willing to work on this antenna!
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73
Pat K7KBN
CWO4 USNR Ret.
W0FM
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« Reply #11 on: April 24, 2012, 01:19:29 PM »

Yeah, I'm pretty sure that a 10 meter dipole made of piano wire would resonate around F sharp.   Grin

Terry, WØFM
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W0BTU
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« Reply #12 on: April 24, 2012, 01:50:43 PM »

Yeah, I'm pretty sure that a 10 meter dipole made of piano wire would resonate around F sharp. 

Depends on how much tension is on it.  Wink

Hey, maybe we could adjust the resonant frequencies of our dipoles that way!  Grin  Quick, let's patent that idea! ;-)
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KB3YLQ
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« Reply #13 on: April 24, 2012, 02:22:02 PM »

Well guys, I do all my tuning by ear, so just call me when you need your piano wire antennas tuned!  Grin
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