All of my J-Pole and Slim Jim antennas are constructed out of Type-M hard copper tubing. Type-M, also known as Red Copper is primarily used in the plumbing industry for supplying drinking water in homes and businesses. Although with the cost of copper continually increasing, the construction industry is shifting towards other materials for plumbing. But like copper tubing carries water in homes, it also can carry electrons in our antennas.
One thing that makes copper an outstanding choice for antennas is that it is a very efficient conductor of electrical energy. In fact about the only common element that is more conductive than copper is silver. You can imagine what an antenna built out of silver would cost.
From EuroCopper.org:
Weight for weight, outside of precious metals, copper is the best conductor of electricity and heat, it is hardly surprising that about 60% of total copper use is for these purposes.
Copper is used in high, medium and low voltage power networks, and copper conductivity is considered to be the standard to which other conductors are compared.Aluminum cables are being replaced with copper ones, because copper conductivity is twice that of aluminum, making copper cables extremely energy efficient, thus helping reduce energy consumption on a global level.
Copper wire has long been the preferred conductor material in the majority of cables used for power and telecommunications. Having high conductivity combined with a ductility that makes it easy to draw down to close-tolerance diameters, it can also be readily soldered to make economic, durable connections.
| Metal | Conductivity |
| Silver | 106 |
| Copper (pure) | 100 |
| Copper (hard Drawn) | 89.5 |
| Aluminum | 45 |
| Steel | 3-15 |
Table from the Electrical Conductivity of Metals.
With copper being twice as conductive as aluminum and 6 times more conductive than steel, it makes an excellent choice as an antenna material. The increased electrical efficiency means more of your RF energy will go up and out the antenna and not be trapped, creating heat energy. More efficient radiation also means that you can run higher powers with a copper antenna than with other building materials. My J-Poles have been tested to 500 watts without issue and there is no reason why they couldn’t go the full legal limit of power if need be.
Now copper isn’t a perfect building material for antenna, there are a couple of downsides. One is the cost. Copper has almost become a semi-precious metal and its cost continues to rise. As the the housing market improves, copper could again take big price increases.
Copper is a best suited material for base antennas. The metal, while soft and malleable, is quite rigid. Stainless steel has a higher tensile strength, so thinner wire can be used. This makes steel an excellent choice for mobile whip antennas where flexibility is a must. But I wouldn’t use stainless on a base antenna as flexibility isn’t an issue and its low electrical conductivity greatly decreases its efficiency.
On a pure energy efficiency standpoint, copper is the best material to choose for a base station or permanently mounted antenna. More of your signal will get into the air and less RF energy will be turned into heat by the internal resistance of the metal.
I fully agree with you on the use of copper antennas and how well they perform. I’ve made many dipoles and 1/4-wave GND-planes out of copper tubing. However, there is a corrosive factor that I’ve noticed that comes with using copper antennas, i.e. the VSWR’s will change after a few months of outside exposer. Have you come up with a way to compensate for this? Thank you.
Phil, N2MDV
in Poca, WV.
i have thought & wondered if it would be possible to spray the finished product with urethane clearcoat to protect it from getting corroded. i dont know if it would affect its velocity factor or its swr. I guess its worth trying. It might work.
Sal, W6SEL
Sierra Vista, AZ.
Sal,
You can certainly paint the antenna with a clear lacquer to reduce corrosion and keep the antenna bright and shiney. A thin layer of paint or lacquer isn’t enough to affect the velocity factor. At least I haven’t noticed any difference in SWR with a painted antenna.
I have been using a prototype of Michael’s UHF Slim Jim antenna for about a year now. I am very pleased with it’s performance, & the wide SWR spread between 440-470 mhz. I would recommend it to anybody who needs this type of antenna. GARY N4KVE
I made a 2 meter stacked 5/8 wave J Pole from 3/4″ copper tubing, sweat it all together so it is sealed, whip it down with etching acid, clean it all off without touching with your fingers (finger oil not good for paint application), and then apply a liberal coat of lacquer for environmental protection. 10 years it look vertually the same as the day I put it up except for a couple of spots where the lacquer had chipped from a branch hitting it.
Using a field strength meter before and after the painting application showed no change in radiation. and because it was very low SWR accross the entire 2 meter band that if the lacquer did change SWR it was so small I did not notice. However, insure you use a non-metalic lacquer if you want the full benefit of a copper antenna.
My J Pole provided more than 6db gain of power input vers ERP. The omnidirectional doughnut had about a 40 degree (20 up 20 down) lobe angle and out preforms anything I have compared for commercial sold vertical base antennas.
KK6IRZ
Sorry for the addon….
I never had a problem with running 2000 watts CW, 2000 watts FM, and 750 watts carrier with 100% modulation and sometimes a little MORE… :).
Yes you read correctly 2 meter AM!!!
I am sure I could have run more but did not have the equipment to try.
I have used one of michael’s 2 meter J-Pole antennas for about a year now. I live in an area where if some persons knew that my antenna was copper it probably would be stolen. I painted my antenna a gloss black and it does not affect the antenna SWR at all. And I still have my antenna! LOL
Jeff, Jeff ,Jeff,
Remember the 1500 watt limit on all bands? Some are much lower too!
Great article and info on the Slim Jim antenna, planning on building one too. I have painted several vertical antenna’s with Krylon camo paint from Walmart with no ill effects.
Les
KD8JLY
I painted my 2 meter slim jim antenna with Grey kry lon primer 9 months ago when I put it up. No swr problems. Less than 1.1-1 across the band and less than 1.3-1 on 70cm with no special uhf elements.
I was wondering about lighting hitting hitting the j pole it is the highest point around is there anything I can do I put in a lighting arrester between ant. and coax any other ideas WQYT742
Forest,
Lightning protection is an important consideration, especially in parts of the country that are more prone to lightning strikes. I usually recommend grounding the antenna for lightning protection and using an arrestor where the feed line enters your home. You can read more about lightning protection here:
http://www.jpole-antenna.com/2013/03/29/lightning-protection-for-antennas/
Michael
Do you use silver solder for your antennas?
I use rosin core electrical solder for the main components of the antenna and a silver bearing lead-free solder to attach the SO-239 connector to the antenna.
Michael
2-ought Steel Wool, knock the finish down on the copper, then spray with a spray-can of urethane clear – no SWR (negligible at the user level, anyhow) change. Make sure that all your construction is complete on the antenna first, or use a knife to scrape a wide enough area to fully remove the urethane if you have to ‘re-connect’ a joint. I use it for DTV antennas (Gray-Hoverman Type), where the active element is copper and the properly constructed back plane is also copper in a split back (again, in that 550-Mhz span). I get around 15-db gain (before pre-amp) with an uncoated antenna, and the same after completion and painting with urethane (I also coat the 300-75 balun-transformer, to help with ‘rain survivability’, as I’m cheap and use not-so-weatherproof $5 baluns most-often).