HF Antenna Wire

9 strand hard-drawn copper antenna wire (oxidized)

9 strand hard-drawn copper antenna wire (oxidized)

What is better to use for antenna wire: aluminum ground wire, old coax, or stranded #12 or #10 copper?
I have used all successfully, but I wonder about radiation resistance of each at 70' above sandy loam in Alabama. My land slopes about 30' from north to south across 5 acres with dipoles running east to west.

I use double shielded coax for transmission line when operating at high power. I use RG 6 for UHF/VHF and low power HF. The slight mismatch that RG 6 causes is not noticed when I use my antenna analyzer to tune at near ground level (10').

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starstarstar 		Wow, a wire antenna is NOT rocket science!
by: WB5FKH

I've been using Copper wire for HF antennas for 52 years. You don't need a "professional", or a book, or a doctoral thesis. What type of wire? I used whatever I had available at the time. I've used soft drawn, which will stretch some, Copperweld 12 ga., Flexweave, and Polystealth, AND they all work well! I've never used old coax for an antenna. Why? Its too heavy. My favorite choice which has evolved over the years is Polystealth. The heavier 12 ga. is more suitable for higher power work. I've had 12 ga. work fine for years with full legal limit power applied.
Bare copper will oxidize, and still work as an antenna.(A tenth of a db, or 1db difference,is impossible to detect with the human ear). Antennas, are my favorite part of this hobby. Its fun to experiment! Wire antennas in the real world have a finite life-span, as does your coax. What type of wire antenna? would be a much better question than what type of wire.
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starstarstarstarstar 		Copper-clad Steel vs Soft-drawn Copper Wire
by: Claude VE2DPE

Hi Floyd KD7SLY,

Insulated #14 electrical wire is not suitable for long antennas such as the 160 M OCF dipole. It is too soft and it will break under constant flexing in the wind.

The copper-clad hard-drawn steel wire is much more suitable for this application.

However, as I have already indicated elsewhere on this page, bare copper oxidizes when exposed to the elements. Oxidized copper acts as a resistance to RF and it only has a noticeable effect on receive.

So, if your bare copper-clad steel wire is new and not yet oxidized, you should expect a slow decrease in performance on receive as the copper ages and oxidizes.

If your wire is already oxidized... then you will not see a noticeable deterioration on receive performance over time. The damage will already have been done.

But hey! Your wire cost you nothing! You can't lose.
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starstarstarstarstar 		Wire for 160 M OCF Dipole
by: Floyd Rasmussen KD7SLY

I also need advice. I'm building an OCF 160-6 M antenna. I have available several hundred feet (more than enough) of single strand copper clad hard drawn steel wire (given to me for free from an old ranch).

I also have enough #14 insulated (of course) electrical wire.

I like the idea of using the hard-drawn steel since I could stretch it tight for the 270 ft length needed.

Will the oxide layer matter much ?
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starstarstarstarstar 		Copper Wire For HF Antennas
by: KJ4EGU

Dear OM Paul,

Let me give you a final answer :

1. Generally speaking, metal oxide is not a good conductor. Any physics/chemistry book and any engineering book on semi-conductors will explain why.

2. Using copper wire as antenna during 40 - 50 years without any problems, is not giving a true answer of the problem, because you are not able to measure the radiation efficiency of your antennas. You are not able to verify how your antennas are degrading in performance over the years, because the evaluation is directly related to the HF propagation and not to the antenna itself.

3. Measuring HF antenna properties ( H-V pattern , directivity, radiation efficiency, polarisation, etc... is a very big challenge for a ham radio operator.

4. Even if you install the best state of the art HF antenna at 200 ft above ground, made with gold or silver wire and pure diamonds as insulators.... if the propagation is bad .... DX will still be very difficult to obtain, if at all.

5. Put any piece of oxidized metal as antenna when the HF propagation is wonderful .... you will make probably more DX contacts.

6. My advice is... consult with professional HF antenna designers from some serious companies ( TCI, Grainger, Telefunken , Thomson, Brown Bovery, etc ) and ask them why they NEVER use copper (not coated) as antenna wire.

7. Or if you not convinced, try to download some antenna specs from these companies and you will probably find a definitive answer. Generally they use aluminum-clad steel wire !

Respectfully,
73

KJ4EGU Carlo F.

========================
Comment by VE2DPE editor:

A resonant HF dipole made of bare copper wire will oxidize over time. In spite of this degradation,it will still continue to radiate enough RF energy to make contacts.

However, the big difference will be noticeable on receive.

An increasingly large portion of the scant microvolts of RF - that the antenna manages to capture - will be lost due to the resistive oxidized copper coating (skin of the antenna wire).

Any ham can easily test this. It involves taking down the old oxidized dipole and - immediately - replacing it with a new antenna of the same dimension and made of new copper wire, and installed at the same height.

The improved receiving capability of the new antenna will readily become apparent, all else being equal.
Rating
starstarstar 		Wire for antennas
by: Paul (unverified contributor)

The higher you go the more the diameter of wire/conductors can make a difference. Below UHF/SHF it doesn't make much (if any) difference at all.

The biggy about wire size is if it's big enough to support it's own weight and the weight of the feed line (maybe). I haven't found any reason to use larger than 14 ga. Stranded or solid conductors is another personal choice (which you got the most of).

The 'HandBook' section on antennas covers most of this sort of stuff. The formulas get a little bit 'bigger' but nothing to worry about.

Learn how/why to do it and you don't have to depend on people (like me) to tell you...

In 40 - 50 years I haven't had any particular problem with copper wire. An oxidized copper wire antenna certainly does work. I defy you to say how you can tell the difference between un-oxidized and oxidized copper wire antennas without laboratory type equipment.
Rating
starstarstarstarstar 		About copper wire
by: Kj4egu

Dear OM,

The copper wire without any coating protection above is not a good solution for exterior HF antenna.
Copper have an excellent conductivity , but copper oxyde ( brownish or green patina ) is NOT a good conductor .

Silver oxyde is a good conductor

If you take in account the skin effect of oxidized copper , the degradation is bigger.

I have installed very high power broadcasting transmitters and antennas systems in more than 120 countries . I never seen copper's. antenna in my professional life IN ANY outdoor HF antenna system !

I believe that writing some comments like " forget galvanized wire , tin wire, aluminium ,etc.... " is exaggerated ( probably false statement in my opinion ) without technical and scientific analisis .

I like very much your website . Congratulations.

Best regards.
73's

Carlo F. - KJ4EGU
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starstarstarstarstar
by: Claude VE2DPE

Yours is a multifaceted question!

First I should tell you that the choice of antenna wire depends on the application. The following must be considered as they all play a part on the resulting performance:

- frequency of operation (overall unsupported span of the antenna wire);
- RF power fed to the antenna;
- acidity or salinity of the air;
- wind;
- ice (not applicable in your area ;)
- stealthiness (not a concern in your case I assume ;)

Now you are asking which of the following antenna wires is best:

- aluminum ground wire
- old coax
- stranded #12 copper
- stranded #10 copper

There is so much to take into consideration that ... to answer your query properly would take a whole book! :)

But I'll try and boil it down.


Resistance vs Impedance

Your concern is: radiation resistance of each dipole at 70' above sandy loam in Alabama.

Just to make sure that we are on the same page ... Please note that there is a difference between:

1- radiation resistance - called feed point impedance - is a function of physical length of antenna at a given frequency, position of the feed point on the antenna, height above ground and ground conductivity (for RF) below. In your case, in Alabama, ground conductivity is considered good on average.

2- ohmic resistance of wire to RF energy at a given frequency and power level is a function of wire size (skin area) and quality of outer skin. Note also that resistance to RF is one of the variables that have to be factored in the overall impedance of an antenna.

3- DC resistance of wire.

Not much has been written on the matter of resistance of wire to RF because of the many factors that have to be taken into consideration. What has been written is too often too theoretical to be of any practical use.


DC Resistance vs Resistance to RF

There is a difference between DC resistance and RF resistance of wire.

For example:

#10 copper wire has a DC resistance of 0.9987 ohms per 1000 ft at 25 degrees Celsius. Therefore a dipole cut for 1.85 MHz would span over 253 feet. It's DC resistance would be

(253/1000) x 0.9987 = 0.2527 ohms (at DC)

However, it's an entirely different matter when applying RF energy to that wire!

RF travels on the "skin" of the wire. It's called the "skin effect" in radio engineering literature. Therefore the quality of the outer skin of the wire becomes important (by the way, there is NO appreciable difference in skin effect between stranded and solid core copper wire).


High Power Operating

Now, because you hinted to it, I suspect that you are looking for the best wire to use at HIGH POWER. High power would indeed be the most demanding scenario for a wire antenna.

At maximum legal power on dipoles for 160 meters to 10 meters, you should use:
- #10 (or bigger)
- use stranded wire because it will resist longer to constant flexing in the wind;
- stranded copper-clad steel (i.e. Davis RF CopperWeld (TM)) for 160 & 80 meters;
- stranded copper-clad steel or stranded hard-drawn copper for 60 - 10 meters;

Regardless of the amount of RF power you intend to submit your antenna to, do not skimp on the quality of the copper-clad steel wire. Use reputable and highly regarded brands of wire manufacturers. Stay away from "no-names" - which could be good enough running barefoot but certainly NOT at maximum legal power.

- The quality of bonding between the steel wire and the copper "skin" as well as the thickness and evenness of the copper layer both have an impact on the durability of the wire antenna. Cheap copper-clad wire is more susceptible to corrosion and breakage than higher quality copper-clad wire.


Guarding Against Corrosion and Oxidization

Unless you live in - or downwind from - a highly industrialized area, air quality in your area should not significantly oxidize the copper surface. Nevertheless, do expect a slow increase of resistance to RF over time because oxidization will slowly occur anyway. The "skin" of the wire will slowly become resistive to RF wanting to travel on it.

However, to guard against deteriorating bare antenna wire from oxidization and corrosion - I would recommend FLEX-WEAVE (TM) by Davis RF as follows (at operating powers of less than 500 watts):

- #12 polyethylene black jacketed - or PVC coated black or green - for centrally supported 160 meter dipole or inverted 'V' antenna;

- #14 polyethylene black jacketed - or PVC coated black or green - for centrally supported 80 meter antenna and other dipoles for 60 meters to 10 meters;

- if the antenna wire will risk rubbing against tree branches, polyethylene (PE) coating is highly recommended.

Forget about any other types of wire (aluminum, galvanized steel, tin-clad aluminum, etc.) as they present much higher resistance (less conducting "skin") to RF than copper.

===

I admit to oversimplifying things quite a bit here. But, like I said earlier, I could write a book on this because there is so much to take into consideration.

I hope this info will be useful to you and to others who read this.

73 de Claude VE2DPE
HamRadioSecrets.com

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73 de VE2DPE
Claude Jollet
104-30 avenue des Berges,
Notre-Dame-des-Prairies, Québec, Canada J6E 1M9

QTH Locator: FN36gb

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