PDA

View Full Version : solid copper vs braided steel wire for antenna?



KD5ZEW
12-01-2008, 04:51 AM
I am making a couple different wire antennas ( a simple dipole and maybe a quasi G5RV for 60/30/15, and I have several types of wires available and just wanted to hear other hams experience with different materials. I have copper clad steel braided wire from a chopped up g5rv, solid copper 20 guage wire and some braided steel picture hanging wire. Due to space limitations the antennas will most likely be inverted V or possibly slopper but no flat top (so relatively low tension on the wires). So information on any good or bad experiences with those wires would be very much appreciated.

Thanks
-John
KD5ZEW

KA4DPO
12-01-2008, 04:55 AM
The steel wire will rust.

KD5ZEW
12-01-2008, 04:57 AM
it's galvanized

AD7N
12-01-2008, 05:24 AM
Few factoids:

1) RF travels along the skin of whatever wire you're using.

2) Copper clad steel and solid copper at the same gauge are electrically identical when talking about <100 watts RF.

3) Copper wire (copper clad or solid) will give a little better sensitivity than galvanized steel. You mention space is limited, so I'm assuming this isn't going to be a huge antenna hundreds of feet long. In that case you'll notice a tiny difference, if any, between copper and steel wire.

Check out this guy's comparison of galvanized steel for antennas: http://www.kongsfjord.no/bm/Antenna%20wires1.pdf


My Recommendation: All things equal, I would go with the copper clad steel - - you get copper conductivity on the outside and the strength of steel on the inside. However, galvanized steel will work quite well if that's what is on hand.

M3KXZ
12-01-2008, 07:22 AM
I wouldn't trust the galvanised steel picture hanging wire. I used some galvanised steel, bought from a DIY store, and intended for outdoor use - it rusted within weeks. Probably due to the salt air as I'm only a couple of miles inland from the sea, but even so I expect it would have rusted anyway. I'm now using 316 marine grade stainless steel and it's perfect.

I'm sure someone will pipe up about losses when using stainless steel vs copper, but it's a matter of a tiny fraction of a dB over normal lengths, and certainly nothing detectable.

W8JI
12-01-2008, 02:23 PM
I wouldn't trust the galvanised steel picture hanging wire. I used some galvanised steel, bought from a DIY store, and intended for outdoor use - it rusted within weeks. Probably due to the salt air as I'm only a couple of miles inland from the sea, but even so I expect it would have rusted anyway. I'm now using 316 marine grade stainless steel and it's perfect.

I'm sure someone will pipe up about losses when using stainless steel vs copper, but it's a matter of a tiny fraction of a dB over normal lengths, and certainly nothing detectable.

Stay away from the woven galvanized steel. It will not last outdoors. I even have short life from a flexible antenna wire that is galvanized steel.

Another factor is the weave of the wire. A shield lay like on RG8 coax has about 3-4 times the RF resistance of a solid sheet with the same surface dimensions when the braid is clean and shiney and compacted. If you loosen the braid up or let it tarnish it is much worse. The braid removed from RG-8 has about the same resistance as a #14 or #16 tinned solid wire at 30 MHz when uncompacted so the lays don't have pressure, and it gets worse when it gets oxidized!

If you weave the conductors, things get much worse. This is because of skin effect. The RF tries to stay on the surface, but the surface weaves in and out so the current flows on many pressure connections along the length. This is very bad news.

73 Tom

W4CBJ
12-01-2008, 02:55 PM
I have used steel wire both solid and stranded on many different occasions. They all worked perfectly fine. As far as the difference...it would take a laboratory experiment to tell the difference. Not worth the effort or worry. Just try it and have fun. So what if it rusts? It is cheap and can be easily replaced. 73 Joe W4CBJ

W8JI
12-01-2008, 04:01 PM
Some people want them to last a long time and stay in the air, others don't mind replacing things.

Myself, I get annoyed when a wire rusts in two and falls, or when the connections start going bad from rust. I've decided I just don't like having something that does everything poorer than something else that is only a few dollars more. But that's just me.

K4NIN
12-01-2008, 04:41 PM
I am making a couple different wire antennas ( a simple dipole and maybe a quasi G5RV for 60/30/15, and I have several types of wires available and just wanted to hear other hams experience with different materials. I have copper clad steel braided wire from a chopped up g5rv, solid copper 20 guage wire and some braided steel picture hanging wire. Due to space limitations the antennas will most likely be inverted V or possibly slopper but no flat top (so relatively low tension on the wires). So information on any good or bad experiences with those wires would be very much appreciated.

Thanks
-John
KD5ZEW

I've been using 18, and even 22 guage speaker wire for my G5RV and loop. Eight bucks for 100 feet. Oh wait, I can split it in two. That's 200 feet for eight bucks. Fine with 100 watts.

M3KXZ
12-01-2008, 07:44 PM
Some people want them to last a long time and stay in the air, others don't mind replacing things.

Myself, I get annoyed when a wire rusts in two and falls, or when the connections start going bad from rust. I've decided I just don't like having something that does everything poorer than something else that is only a few dollars more. But that's just me.

Hear, hear! When I used that galvanised steel a few months ago, it all looked lovely at first. Then I noticed it becoming darker and darker over just a period of days. By the time I took it down it had covered all my stainless steel hardware and my uPVC centre insulator in lovely brown rust! Also, it started off working ok then seemed to get deafer and deafer. I'm not sure if the zinc disappearing and being replaced by rust had anything to do with this, or whether the bands just went quieter and quieter!

Pete

PA5COR
12-01-2008, 08:01 PM
When mixing stainless steel and carbon steel remember to isolate them because the carbon steel will start rusting the stainless steel.
One reason you use isolation sets in pipes when going from carbon steel pipes to stainless steel pipes.

I used stainless steel wire for antenna wire just as easy as copper wire, there will be a difference but it is too small to get worried about it.

Here ship supply stores sell stainless steel flexible cable 3 or 4 millimeters thick not too expensive, it will last a lifetime, and is strong as well.

73,
Cor

K9STH
12-01-2008, 08:34 PM
I use galvanized steel electric fence wires for my above ground radials for both my HyGain HyTower and my 40 meter full sized vertical that I phase with the HyTower. Those on the HyTower have been installed for over 26 years (since my swimming pool was installed and a good number of the buried radials under the HyTower were "dug up") and there is no indication of rust. Those for the 40 meter vertical are considerably newer but they are fine as well.

I have had copper corrode over the years but since the vast majority of my antennas do not use copper I generally don't worry about it. My antennas are mostly aluminum.

Glen, K9STH

AF6LJ
12-01-2008, 09:11 PM
I have used copperweld steel wire, stranded 14 gauge with good results. The only antenna I ever had trouble with was a 40M dipole that was tied off between the corner of a house and a palm tree. It took an 80MPH wind to bend the tree enough to break the wire.

W4INF
12-01-2008, 09:36 PM
Ive used both solid and stranded: 14ga copper insulated I think it is THNN wire, for household wiring, I got both at Home Depot in 500ft spools.

The first roll I got was solid, my thinking is it would be a better wire. I had no idea why it would be better, but thats what I started with. The wire worked just fine... however it ended up not being flexible enough and over a brief time of service with the winds we get, I had the dipole on the ground.

Ive switched over to stranded, on my second roll when doing antenna experiments. Have not had any break on me yet!

So my suggestion is stranded copper insulated.

GL-
Andrew

G0GQK
12-01-2008, 10:35 PM
The best metal for radiating is aluminium and luckily its also the lightest. The next best is copper and that is why since the dawn of radio those with brains used copper for wire antenna's. There has never ever been a manufacturer of antenna's who made them from steel. The antenna you are making for 15,30 and 60 metres is a dipole, not a G5RV.

G0GQK

M3KXZ
12-01-2008, 11:49 PM
The best metal for radiating is aluminium and luckily its also the lightest. The next best is copper and that is why since the dawn of radio those with brains used copper for wire antenna's. There has never ever been a manufacturer of antenna's who made them from steel. The antenna you are making for 15,30 and 60 metres is a dipole, not a G5RV.

G0GQK


The differences in radiating efficiency are negligible, provided the steel is a good non-magnetic stainless steel. And then factor in the durability, and the cost, and 2mm or so stainless steel wire can be a very good option. I buy 50m of 2mm 316 marine grade stainless steel for 18 which ain't too bad really.

Also, it (stainless steel wire) IS used by commercial manufacturers eg
http://www.qmac.com/base_antennas.html

http://www.mobat-usa.com/antenna.htm

http://www.bwantennas.com/pro/veeant.pro.htm

http://www.rf-systems.nl/pdf/litze.pdf

http://www.poynting-europe.com/Poynting/Jamming%20PDF/OMNI-A0092%20Version%202.0.pdf

The list goes on. Also, a huge number of mobile whip antennas are stainless steel. And the wire resistance loss is miniscule compared with the radiation resistance of an antenna, so the impact on antenna performance is negligible.

I use 2mm 316 marine grade stainless steel almost exclusive now for portable and base wire antenna and could not discern a jot of difference in RF performance between a vertical antenna made from stainless steel wire supported by a fishing pole, and a vertical made from copper wire supported by a fishing pole. But the stainless steel wire is so easy to coil and uncoil with no knots or kinks, the connections won't corrode in the salty sea air - it's a winner.

K9STH
12-01-2008, 11:58 PM
GQK:

Actually, copper is a better radiating medium than aluminum and silver plated copper is even better. However, the benefits of the considerably less weight of aluminum makes the use of aluminum very attractive even though it is not quite as good in terms of actual radiation efficiency.

Glen, K9STH

W8JI
12-02-2008, 03:07 AM
I use galvanized steel electric fence wires for my above ground radials for both my HyGain HyTower and my 40 meter full sized vertical that I phase with the HyTower. Those on the HyTower have been installed for over 26 years (since my swimming pool was installed and a good number of the buried radials under the HyTower were "dug up") and there is no indication of rust. Those for the 40 meter vertical are considerably newer but they are fine as well.

I have had copper corrode over the years but since the vast majority of my antennas do not use copper I generally don't worry about it. My antennas are mostly aluminum.

Glen, K9STH


I wish had your galvanized wire for my fence wire. My 6 or 7 year old Beverages made from 17 gauge electric fence wire are now breaking somewhere every few weeks. Worse yet I can't solder the stuff because the heat takes off the galvanized layer and it rust through in a year or so!

I even had bad luck with flexweave wire. It got all rusty at the solder joints and broke.

Give me copper or copper weld any day of the week!

73 Tom

W8JI
12-02-2008, 12:32 PM
The differences in radiating efficiency are negligible, provided the steel is a good non-magnetic stainless steel. And then factor in the durability, and the cost, and 2mm or so stainless steel wire can be a very good option. I buy 50m of 2mm 316 marine grade stainless steel for 18 which ain't too bad really.


It doesn't matter much if you can stick a magnet to the steel or not. That has nothing to do with radiation.

The permeability has an effect on the skin depth but it is the permeability at the radio frequency that matters, not with a steady-state field. It also only affects skin depth.

Sticking magnets to the wire to judge radiation ability is a total waste of time.


73 Tom

KA4DPO
12-02-2008, 04:21 PM
I am making a couple different wire antennas ( a simple dipole and maybe a quasi G5RV for 60/30/15, and I have several types of wires available and just wanted to hear other hams experience with different materials. I have copper clad steel braided wire from a chopped up g5rv, solid copper 20 guage wire and some braided steel picture hanging wire. Due to space limitations the antennas will most likely be inverted V or possibly slopper but no flat top (so relatively low tension on the wires). So information on any good or bad experiences with those wires would be very much appreciated.

Thanks
-John
KD5ZEW


John, the galvanized picture wire is designed for hanging pictures indoors. It only has a thin coating of nickel and it will rust and corrode very quickly when you expose it to the elements. The biggest problem with this is that small areas of corrosion can act like a rectifier and cause all kinds of unwanted RF to occur. The other bad thing that happens is that these same little rectifiers will reduce the received signal on the antenna.

Hot dip galvanized electric fence wire is made to be used outdoors in the weather and will hold up very well. As far as radiating qualities are concerned, Steel, Copper, or Aluminum all work well. You would need some very sensitive laboratory instruments to measure the difference in skin effect and signal radiation between them. Since this is ham radio and you won't be working any deep space probes I wouldn't worry about the differences.

John..

M3KXZ
12-02-2008, 05:01 PM
<snip>

Sticking magnets to the wire to judge radiation ability is a total waste of time.


73 Tom


Just as well I've never bothered to do that then ;)

I had seen mention though that the skin depth of non-magnetic wire is 40 times greater than that of magnetic wire. I'm not sure if this is correct or not, but the info given was 200 um at 5MHz for non-magnetic stainless steel, vs 5 um at 5MHz for magnetic steel. Would this not have a large effect on the wire loss?

I had understood that it was the larger skin depth of non-magnetic stainless steel that considerably lowered the wire loss at RF, and that the skin depth of magnetic steel was so small at RF that the only way for it to have a low enough wire loss would be to heat it above its Curie point. I need to find out more about this. It's not something I've studied before.

73

Pete

W8JI
12-02-2008, 05:42 PM
Just as well I've never bothered to do that then ;)

I had seen mention though that the skin depth of non-magnetic wire is 40 times greater than that of magnetic wire. I'm not sure if this is correct or not, but the info given was 200 um at 5MHz for non-magnetic stainless steel, vs 5 um at 5MHz for magnetic steel. Would this not have a large effect on the wire loss?

I had understood that it was the larger skin depth of non-magnetic stainless steel that considerably lowered the wire loss at RF, and that the skin depth of magnetic steel was so small at RF that the only way for it to have a low enough wire loss would be to heat it above its Curie point. I need to find out more about this. It's not something I've studied before.

73

Pete

Peter,

I'd have to know the permeability at the operating frequency, not at some unknown frequency like near dc.

The problem is caused by magnetic flux concentration. The more flux lines circling a current carrying area the higher the impeadance becomes, but what happens with near steady state fields isn't anything at all like what happens at radio frequencies.

For example a steel chassis on a radio shields for all purposes exactly like aluminum for both magnetic and electric fields at high frequencies. If we place a magnetic steel core inside a coil at radio frequencies the inductance decreases. It only increases inductance if the iron is insulated into tiny particles that don't support eddy currents.

We would have to know how the material behaves at the operating frequency, not at some static or very low frequency.

For example, we can stick a magnet to copperweld and it is no different at all than solid copper at radio frequencies. If it had a solid copper core instead of steel, it wouldn't change a bit at radio frequencies.

I'm sure the permeability has an effect on skin depth, and skin depth affects the cross section available to carry current, but I have no idea what the differences are at radio frequencies.

I do know one thing for sure. Loss is not related to how the material acts with static fields or fields changing at a significantly different rate than the operating frequency.

My only point is I don't want people thinking a magnetic material like steel will make a high resistance conductor or a non-magnetic steel (or even aluminum) would work like a charm. There's a whole lot more at work than that!

It would be interesting to see the RF resistance comparisons between the stainless types. THAT is what would matter electrically or for radiation, nothing else would.

73 Tom

ad: ARScom-1