best or acceptable wire size for dipole

[AG3Y]

It's GOTTA be TRUE, Steve ! I just read it on the INTERNET ! ! !

[W9GB]

I am building a wire dipole. While I was pricing antenna wire ($ per foot), I start wondering which is better for a dipole?
Solid copper wire or stranded copper wire?
What is the best wire gauge (AWG) 14, 12 or 10 ?

I have used a variety of wire types for building wire antennas (electric fence wire, solid Copperweld, Wireman's Silky, aluminum gutters, electrical wire, etc.)
My preference after 35 years is 14 AWG stranded wire available at your local hardware store. It is readily available, flexible, and easy to use.

I think that solid wire would be better, because the RF signal runs on the outside of the wire (skin effect) -- is that true?

Skin effect does occur, but the difference between solid and stranded wire is minimal for this usage.

The larger the wire, the more broad-banded the antenna will be.

Correct, build a FAT dipole to achieve this effect (2 parallel wires spaced 12 to 36 inches apart from each other).

w9gb

[AG3Y]

Actually, Greg, wouldn't a three dimensional "fat" dipole work better? I have seen the installation at W1AW, and they use at least 4 wires held together with crossed spreaders to form each side of the antenna. Maybe you could get away with three wires, but the spreader arrangement would probably be more difficult, unless you made them of equalateral triangles . HMMMMM there is an idea !

[VK2AKG]

re:

::Kerry, where did that theory come from? Skin effect can't know what the conductor material is, unless you just invented something the scientific community never knew before...

Steve, I thought you might like to have a look here:
http://en.wikipedia.org/wiki/Skin_effect

re:

It's GOTTA be TRUE, Steve ! I just read it on the INTERNET ! ! !

Jim, you may prefer to look in Microwave Engineering by AF Harvey (Library of Congress Catalog Card Number: 62-13097 ) which suitably pre-dates the internet having been published by Academic Press London & New York in 1963.

On page 4 Harvey clearly states:

"The skin depth is inversely proportional to the square root of the conductivity of the material. ..."

73 Frank

[G4ALA]

Just an observation.

The bigger (greater diameter) the wire the larger the outer surface and hence the less the skin resistance will be.

A great advantage of large diameter wire is that the bandwidth of the dipole is increased.

Cage dipoles having several pieces of spaced wire on each side of the dipole held apart by spacers increase the bandwidth considerably.

You probably only wish to have one piece of wire on each side.

Aluminium alloy wire is light, strong, highly conductive, quite large diameter and readily available from most Ham stores (at least, over here in G-land). Ideal!

If you want to go for the jackpot, try coaxial cable to make your dipole. The outer conductor is very large diameter, compared with most wire. However, co-ax is relatively heavy compared with most wire. It will sag under the sort of tension it can tolerate.

But, that is not a problem. You can string up non-conductive rope to give mechanical strength and suspend the co-ax cable beneath the rope at intervals. Sorted!

The question of "best wire" is seldom asked. It seems a very good question to ask.

73

John

G4ALA

[AG3Y]

"Jim, you may prefer to look in Microwave Engineering by AF Harvey (Library of Congress Catalog Card Number: 62-13097 ) which suitably pre-dates the internet having been published by Academic Press London & New York in 1963.

On page 4 Harvey clearly states:

"The skin depth is inversely proportional to the square root of the conductivity of the material. ..."

73 Frank"

Frank, I am always willing to learn something new. There must be other factors at play here beside the conductivity of the material. Your quote is from a microwave journal. Since there is no "skin effect" at DC, and unmeasurable skin effect at normal power line frequencies ( 60, 120 hz etc. ) I would be interested in knowing how frequency factors into the equation. I would love to see the rest of the quote, since it might be rather difficult for the rest of us to obtain that book. We do not all have access to major city libraries !


73, Jim

[AI3V]

"Jim, you may prefer to look in Microwave Engineering by AF Harvey (Library of Congress Catalog Card Number: 62-13097 ) which suitably pre-dates the internet having been published by Academic Press London & New York in 1963.

On page 4 Harvey clearly states:

"The skin depth is inversely proportional to the square root of the conductivity of the material. ..."

73 Frank"

Frank, I am always willing to learn something new. There must be other factors at play here beside the conductivity of the material. Your quote is from a microwave journal. Since there is no "skin effect" at DC, and unmeasurable skin effect at normal power line frequencies ( 60, 120 hz etc. ) I would be interested in knowing how frequency factors into the equation. I would love to see the rest of the quote, since it might be rather difficult for the rest of us to obtain that book. We do not all have access to major city libraries !


73, Jim

Jim, I think you will find "skin effects" are quite noticeable at 60 hz. Copper busbar is rarely more than 1/4 inch thick,[usually, either 3" or 6" x 1/4] Thats the break-even thickness at 60 hz. And round or square cross sectioned Cu is "never" used (edit: for busbar).

Rege

[AI3V]

re:



Steve, I thought you might like to have a look here:
http://en.wikipedia.org/wiki/Skin_effect

re:



Jim, you may prefer to look in Microwave Engineering by AF Harvey (Library of Congress Catalog Card Number: 62-13097 ) which suitably pre-dates the internet having been published by Academic Press London & New York in 1963.

On page 4 Harvey clearly states:

"The skin depth is inversely proportional to the square root of the conductivity of the material. ..."

73 Frank

And if this were not true, than nobody would use stainless steel antennas mobile, We would all use some sort of copper alloy!!!!

Rege

[AG3Y]

Rege, I am not disagreeing with you, because I obviously do not have expert knowledge in this area. But I do have another question.

For years, McIntosh ( not the computer manufacture, but the audio component one ) wound their own audio transformers with square cross-sectioned copper wire. As you probably know, McIntosh components were considered some of, if not THE best audio components in the tube era.

A McIntosh amplifier could pass an audio range of around 25 to 25,000 Hz, a frequency range of over 1000:1 with less than 1dB variation in power output.

Now, obviously, there is a factor much larger than "skin effect" at play here !

I'm thinking such things as inter-winding capacitance ( which the Mac engineers worked hard to minimze ) and cost factors ( which were not a real factor to those engineers, but would be in other applications such as RF Transmitter site grounding ) etc.

A fascinating subject to discuss, but I sure would love to see the entire formula!

73, Jim

[KR2D]

Aluminium alloy wire is light, strong, highly conductive, quite large diameter and readily available from most Ham stores (at least, over here in G-land). Ideal!

I was wondering if anyone used aluminum (or aluminium ) wire for antennas. It's not commonly available here except in very large sizes for high current circuits or mains service drops. It seems ideal for wire antennas because it costs less than copper and weighs much less. Precautions need to be taken for connections to minimize corrosion, but the correct hardware and anti-corrosion substances are readily available.