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Author Topic: Diameter of radials in verticals  (Read 4416 times)
EA5BZ
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Posts: 14




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« on: September 12, 2010, 03:57:29 AM »

Hello friends:
I have been reading and normally we use 18 awg (1mm diameter) radials in our radials systems.
My question is: Why?
And ... could we improve performance if we use higher diameters?

Thank's a lot.
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K3GM
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Posts: 2424




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« Reply #1 on: September 12, 2010, 05:38:48 AM »

It's a balance between economics, desired tensile strength, and the quantity of radials to be installed.  When only a few radials are used, gauge will improve efficiency.  With many radials, gauge becomes unimportant as return currents are divided  over a large number of conductors.  Another consideration is what's going on in the area they occupy.  Example, I mow my field with a tractor.  The 16 AWG surface radial radials I use will withstand the tractor tires much better than #24 magnet wire.
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K7KBN
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Posts: 3597




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« Reply #2 on: September 12, 2010, 09:27:21 AM »

Hello friends:
I have been reading and normally we use 18 awg (1mm diameter) radials in our radials systems.
My question is: Why?
And ... could we improve performance if we use higher diameters?

Thank's a lot.

"...improve performance...?"  Perhaps - experiment and see if there's any improvement.
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73
Pat K7KBN
CWO4 USNR Ret.
K0ZN
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Posts: 1826




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« Reply #3 on: September 13, 2010, 11:36:43 AM »

Hi.

In the real world, at Amateur power levels, the gauge of the wire is not important electrically (assuming you have a reasonable number of radials). It is mostly
about cost and mechanical strength. It IS important that you use copper wire and not steel, however!!  Steel rusts and rust has a high resistance at RF.

My personal experience with a couple of ground mounted verticals is that AWG #14 copper wire seems to be a decent compromise between cost and strength for buried
radials and the wire seems like it will last many, many years in our soil. If you have corrosive soil conditions a larger gauge is appropriate.
If you are using the radials as guy wires on a Ground Plane antenna, then mechanical strength is very important and a moderately large gauge is needed for
mechanical safety and reliability.

73,  K0ZN
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KH6DC
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Posts: 771




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« Reply #4 on: September 13, 2010, 10:07:00 PM »

I used #14 ga stranded copper wire I bought from Home Depot in 300 ft spools. It was cheap at $20 per spool and #14 seems like a good number and it was something the ARRL Antenna Book suggested.  73, Delwyn
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73 and Aloha,
de Delwyn, KH6DC
K9KJM
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Posts: 2415




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« Reply #5 on: September 15, 2010, 10:35:21 PM »

As already pointed out, The main reason for selecting lighter gauge wire is for cost.  And mechanical strength is important. The very light gauge wire can be broken in areas with extreme freeze/thaw cycles, Or easily cut with a shovel, etc.

#14 gauge copper does seem to be a pretty fair compromise of economy vs strength.

Commercial AM broadcast stations used to use #10 gauge soft copper, And are now going to #10 gauge heavy copperclad steel wire, with the increasing costs of copper, And copper theft.
IF the coppercladding is heavy enough, That type of wire should last for many years before the steel starts to rust through. (Note that this is special copper cladding made for burial, NOT thin cladding as used on antenna wire)
Pure copper wire's lifespan in most any soil type can be measured in hundreds, If not thousands of years!

Around here, I have found it cheaper to buy insulated solid copper wire from a discount home supply type store and just zip the insulation off with a handy knife. (Stretch it out between two supports to keep tension on it while doing so.)  Bare copper wire being actually more expensive by the time shipping etc is added in.

(If burying radials, Use BARE copper so it adds to your lightning ground system.  There is no point to attempt to "tune" in or on the ground radials- Just make them as long as you can. At least a 1/4 wave at your lowest frequency is nice.) If installing elevated radials, Insulated wire should be used for safety, And elevated radials can be "tuned" to length.
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K3GM
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« Reply #6 on: September 16, 2010, 04:50:36 AM »

I often wondered if buying and stripping 14-2 Romex would be more economical than 500' spools of THHN?  Pulled taut Romex should be a cinch to separate the wire from the plastic jacket using a razor blade. 250ft of 14-2 is going for forty-two  bucks a Home Depot which would yield 750ft.  Wonder how that compares to THHN per foot?
« Last Edit: September 16, 2010, 07:42:26 AM by Tom Hybiske » Logged
N3QE
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Posts: 5494




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« Reply #7 on: September 16, 2010, 07:03:39 AM »

I think it largely has to do with whatever is economical, locally available and easily plantable. In many cases "economical" means "I already have it" rather than anything to do with commodity prices.

I have seen everything from insulated copper to bare copper to copper clad steel to aluminum to stainless steel wire being used as radials. Other than some Noalox or equivalent for the non-copper stuff I'm not sure there's any electrical difference.

Tim.
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W0BTU
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« Reply #8 on: September 17, 2010, 03:02:05 PM »


In the real world, at Amateur power levels, the gauge of the wire is not important electrically (assuming you have a reasonable number of radials). It is mostly about cost and mechanical strength.

Precisely. While there may be a difference in efficiency on paper, in the real world you will never notice it.

Quote
  It IS important that you use copper wire and not steel, however!!  Steel rusts and rust has a high resistance at RF. ...

I agree. Mostly.

I put down 120 60' radials at a previous QTH, made from galvanized electric fence wire. At the same time, I buried an anode bag (connected to the radials) to help protect them from corrosion. Do a Google search for "cathodic protection" or "anode bag" and you'll see why it's possible to use galvanized steel radial wires lying on the surface of the earth without worrying too much about corrosion.

If you're not going to do that, better use copper.
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