| Page 1 of 2 | 1 | 2 |
|
|
Gold plating antenna elements?
Hi Gang
Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
Gary V. Deutschmann, Sr. wrote:
Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary Why don't you download the demo version of eznec, www.eznec.com/, model an antenna with gold, copper, aluminum, etc. and see for yourself how much difference it makes? -- Jim Pennino Remove -spam-sux to reply. |
|
"Gary V. Deutschmann, Sr." wrote:
Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary The only real downside would be security! :-) -- -------------------------------------- Diagnosed Type II Diabetes March 5 2001 Beating it with diet and exercise! 297/215/210 (to be revised lower) 58"/43"(!)/44" (already lower too!) -------------------------------------- Visit my HomePage at http://members.shaw.ca/finkirv/ Visit my very special website at http://members.shaw.ca/finkirv4/ Visit my CFSRS/CFIOG ONLINE OLDTIMERS website at http://members.shaw.ca/finkirv5/ -------------------- Irv Finkleman, Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP Calgary, Alberta, Canada |
I've seen real-life cases with high-Q microstrip structures where gold
plating actually caused a significant lowering of efficiency. As you point out, nickel is used as a barrier metal to prevent alloying of the gold with the underlying copper. If the gold isn't at least several skin depths thick, significant current flows in the nickel. Nickel is a particularly poor RF conductor, very much worse than copper, because the skin depth in nickel is decreased dramatically by its ferromagnetic permeability. So, if you're able to calculate skin depth, and know what you're doing, and are willing to use quite a bit of gold (particularly necessary at HF and below) you can achieve efficiency with gold plating that's pretty much indistinguishable from that of copper. If you don't know what you're doing, it is possible to substantially degrade the efficiency by gold plating. I'm sure somebody could be conned into buying one, though. Roy Lewallen, W7EL Gary V. Deutschmann, Sr. wrote: Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
Hi Roy;
It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H "Roy Lewallen" wrote in message ... I've seen real-life cases with high-Q microstrip structures where gold plating actually caused a significant lowering of efficiency. As you point out, nickel is used as a barrier metal to prevent alloying of the gold with the underlying copper. If the gold isn't at least several skin depths thick, significant current flows in the nickel. Nickel is a particularly poor RF conductor, very much worse than copper, because the skin depth in nickel is decreased dramatically by its ferromagnetic permeability. So, if you're able to calculate skin depth, and know what you're doing, and are willing to use quite a bit of gold (particularly necessary at HF and below) you can achieve efficiency with gold plating that's pretty much indistinguishable from that of copper. If you don't know what you're doing, it is possible to substantially degrade the efficiency by gold plating. I'm sure somebody could be conned into buying one, though. Roy Lewallen, W7EL Gary V. Deutschmann, Sr. wrote: Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
silver is a better conductor than gold, but will tarnish very easily, might
now be a good idea for what you are intending just my two cents "H. Adam Stevens, NQ5H" wrote in message ... Hi Roy; It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H "Roy Lewallen" wrote in message ... I've seen real-life cases with high-Q microstrip structures where gold plating actually caused a significant lowering of efficiency. As you point out, nickel is used as a barrier metal to prevent alloying of the gold with the underlying copper. If the gold isn't at least several skin depths thick, significant current flows in the nickel. Nickel is a particularly poor RF conductor, very much worse than copper, because the skin depth in nickel is decreased dramatically by its ferromagnetic permeability. So, if you're able to calculate skin depth, and know what you're doing, and are willing to use quite a bit of gold (particularly necessary at HF and below) you can achieve efficiency with gold plating that's pretty much indistinguishable from that of copper. If you don't know what you're doing, it is possible to substantially degrade the efficiency by gold plating. I'm sure somebody could be conned into buying one, though. Roy Lewallen, W7EL Gary V. Deutschmann, Sr. wrote: Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
Nickel can also be the source of IM.
Anyway, isn't Gold's conductivity really low? -- Steve N, K,9;d, c. i My email has no u's. "Roy Lewallen" wrote in message ... I've seen real-life cases with high-Q microstrip structures where gold plating actually caused a significant lowering of efficiency. As you point out, nickel is used as a barrier metal to prevent alloying of the gold with the underlying copper. If the gold isn't at least several skin depths thick, significant current flows in the nickel. Nickel is a particularly poor RF conductor, very much worse than copper, because the skin depth in nickel is decreased dramatically by its ferromagnetic permeability. So, if you're able to calculate skin depth, and know what you're doing, and are willing to use quite a bit of gold (particularly necessary at HF and below) you can achieve efficiency with gold plating that's pretty much indistinguishable from that of copper. If you don't know what you're doing, it is possible to substantially degrade the efficiency by gold plating. I'm sure somebody could be conned into buying one, though. Roy Lewallen, W7EL Gary V. Deutschmann, Sr. wrote: Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
Steve Nosko wrote:
Nickel can also be the source of IM. Anyway, isn't Gold's conductivity really low? Relative Conductivities: Copper 1.00 Aluminum 0.61 Gold 0.706 Nickel 0.198 Now what is IM?? Deacon Dave, W1MCE |
"S" wrote in message et... silver is a better conductor than gold, but will tarnish very easily, might now be a good idea for what you are intending I thought that silver oxide was a decent conductor, which is why it is sometimes used as a plateing material. jim N8EE |
Gang:
Way back in the 60s, I think, there was a very thorough research article in JIEE (Aust.) about RF skin conductivity of various practical metals. Oxygen Free High Conductivity (OFHC) Copper won hands down. Until you heat it, bend it, or look at it cross-eyed, that is. Silver plate is next best, but only if it is hard Silver, not cosmetic Silver which is what you get at your local plating shop. Hard Silver plate is difficult to come by, and uses chemicals which I'm guessing have since been banned by EPA. In my day (1960), hard Silver plate with a Rhodium flash was the most practical high RF conductivity process available. Nowadays, who knows? -- Crazy George Remove N O and S P A M imbedded in return address |
On Fri, 16 Apr 2004 20:40:53 -0400, "JLB"
wrote: "S" wrote in message . net... silver is a better conductor than gold, but will tarnish very easily, might now be a good idea for what you are intending I thought that silver oxide was a decent conductor, which is why it is sometimes used as a plateing material. Hi All, It hardly matters unless you are speaking of switch contacts. Insulated wire's insulation is absolutely unconductive, and yet in the context of antennas it doesn't impact the wire's capacity to carry current. Oxidation products only become a problem at interfaces where they either resist current between the joined conductors, or create a semiconducting barrier. The technician is taught to clean surfaces of tarnish to bring bright metal into contact. Then crimp them (or twist the wire - same thing) for a gas tight seal. Then solder them to weather proof the seal (solder is never meant to be a mechanical join or the conductive path). Common practice allows for solder to provide more functionality than what I describe - this does not elevate the method. Barring the final solder, switch contact faces must meet the same conditions of bright metal and gas tight seals. This is often achieved by pressure (some mistake the so-called "wiping" action as meaning to scrub the oxide away - a useful metaphor but only that; otherwise switches would self demolish in very few operations) and a sustaining current (wet vs. dry contacts). 73's Richard Clark, KB7QHC |
Hmmm...My book says aluminum's resistivity is about 2.6 microohm-cm,
and copper's is 1.7, only a 1.5:1 ratio--though it may not be quite that good for commonly used aluminum alloys. OTOH, copper also suffers from being alloyed. But in any event, it's good to keep in mind that the RF resistance ratio for non-magnetic materials goes as the square root of the bulk resistivity ratio, because higher resistivity materials have larger skin depth. So a 2:1 ratio at DC ends up being only 1.41:1 at RF, and 1.5:1 at DC is only a bit over 1.2:1 at RF. Since both copper and aluminum have good conductivity, it's just not worth sweating in practically all cases, unless the antenna is very short (and thus has very low feedpoint radiation resistance). Actually, what I thought Gary might be getting at is the protection from corrosion that gold might offer, as compared with bare copper. I'd say that it IS worth worrying about protecting your antenna from corrosion. Maybe you just have to think about it long enough to understand that you are lucky to live in a place where corrosion isn't a problem, or maybe you live next to the ocean where salt spray will get the best of almost anything metallic. But like Roy says, gold over nickel is probably a bad idea. Unplated stainless steel antenna wire is probably a bad idea. Painted copper pipe, or anodized aluminum tubing, will probably work well for a long time. Cheers, Tom "H. Adam Stevens, NQ5H" wrote in message ... Hi Roy; It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H |
One place where I can clearly see the difference between copper and aluminum
is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters. Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with the same whip in all cases. This is a case of a short antenna. The difference is significant and easily measured. 73 H. NQ5H "Tom Bruhns" wrote in message m... Hmmm...My book says aluminum's resistivity is about 2.6 microohm-cm, and copper's is 1.7, only a 1.5:1 ratio--though it may not be quite that good for commonly used aluminum alloys. OTOH, copper also suffers from being alloyed. But in any event, it's good to keep in mind that the RF resistance ratio for non-magnetic materials goes as the square root of the bulk resistivity ratio, because higher resistivity materials have larger skin depth. So a 2:1 ratio at DC ends up being only 1.41:1 at RF, and 1.5:1 at DC is only a bit over 1.2:1 at RF. Since both copper and aluminum have good conductivity, it's just not worth sweating in practically all cases, unless the antenna is very short (and thus has very low feedpoint radiation resistance). Actually, what I thought Gary might be getting at is the protection from corrosion that gold might offer, as compared with bare copper. I'd say that it IS worth worrying about protecting your antenna from corrosion. Maybe you just have to think about it long enough to understand that you are lucky to live in a place where corrosion isn't a problem, or maybe you live next to the ocean where salt spray will get the best of almost anything metallic. But like Roy says, gold over nickel is probably a bad idea. Unplated stainless steel antenna wire is probably a bad idea. Painted copper pipe, or anodized aluminum tubing, will probably work well for a long time. Cheers, Tom "H. Adam Stevens, NQ5H" wrote in message ... Hi Roy; It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H |
That's much, much more difference than can be explained by the different
conductivities of the metals. Either some very resistive alloys are involved, or there are differences between the antennas other than the type of metal. Roy Lewallen, W7EL H. Adam Stevens, NQ5H wrote: One place where I can clearly see the difference between copper and aluminum is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters. Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with the same whip in all cases. This is a case of a short antenna. The difference is significant and easily measured. 73 H. NQ5H |
Roy
The measurements are reproducible. That's for sure. And you can bet the aluminum in the Tarheel and Hi-Q are alloys. Using the Nott (just copper, no plating) I get a 9 ohm load at resonance on 20, 10 ohms on 40 and 80. With a simple toroidal autoformer the mobile rig sees 50 ohms resistive at resonance on all three bands. 73, NQ5H H. "Roy Lewallen" wrote in message ... That's much, much more difference than can be explained by the different conductivities of the metals. Either some very resistive alloys are involved, or there are differences between the antennas other than the type of metal. Roy Lewallen, W7EL H. Adam Stevens, NQ5H wrote: One place where I can clearly see the difference between copper and aluminum is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters. Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with the same whip in all cases. This is a case of a short antenna. The difference is significant and easily measured. 73 H. NQ5H |
Roy
I looked up the numbers. The Nott is 2" diameter bare copper 3' long. The Tarheel is 2" diameter painted aluminum 4' long. The Hi-Q is 1" diameter powder-coated aluminum 3' long. I used the same whip for all measurements. If we take the conductivity of copper to be 100, aluminum is then 60 and aluminum alloys are as low as 30. That's a factor of two between the Nott and Tarheel and the reduced surface area of the Hi-Q explains the additional resistance there. Considering the difference in surface area and resistivity among the antennas, the measured impedances seem quite reasonable to me. 73 H. NQ5H "Roy Lewallen" wrote in message ... That's much, much more difference than can be explained by the different conductivities of the metals. Either some very resistive alloys are involved, or there are differences between the antennas other than the type of metal. Roy Lewallen, W7EL H. Adam Stevens, NQ5H wrote: One place where I can clearly see the difference between copper and aluminum is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters. Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with the same whip in all cases. This is a case of a short antenna. The difference is significant and easily measured. 73 H. NQ5H |
"Tom Bruhns" wrote in message m... Hmmm...My book says aluminum's resistivity is about 2.6 microohm-cm, and copper's is 1.7, only a 1.5:1 ratio--though it may not be quite that good for commonly used aluminum alloys. OTOH, copper also suffers from being alloyed. But in any event, it's good to keep in mind that the RF resistance ratio for non-magnetic materials goes as the square root of the bulk resistivity ratio, because higher resistivity materials have larger skin depth. So a 2:1 ratio at DC ends up being only 1.41:1 at RF, and 1.5:1 at DC is only a bit over 1.2:1 at RF. Since both copper and aluminum have good conductivity, it's just not worth sweating in practically all cases, unless the antenna is very short (and thus has very low feedpoint radiation resistance). Actually, what I thought Gary might be getting at is the protection from corrosion that gold might offer, as compared with bare copper. I'd say that it IS worth worrying about protecting your antenna from corrosion. Maybe you just have to think about it long enough to understand that you are lucky to live in a place where corrosion isn't a problem, or maybe you live next to the ocean where salt spray will get the best of almost anything metallic. But like Roy says, gold over nickel is probably a bad idea. Unplated stainless steel antenna wire is probably a bad idea. Painted copper pipe, or anodized aluminum tubing, will probably work well for a long time. Cheers, Tom On the other hand, aluminum is lighter. Might be worthwhile to compare the resistance of an Al and Cu conductors (solid and tube) of the same length and the same weight. I am pretty sure AL wins at 60 Hz. Tam/WB2TT "H. Adam Stevens, NQ5H" wrote in message ... Hi Roy; It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H |
H. Adam Stevens wrote:
With a simple toroidal autoformer the mobile rig sees 50 ohms resistive at resonance on all three bands. Got any idea what the efficiency of your autoformer is? I'm assuming a single coil for a primary, tapped down for the load. Would a 4:1 transmission line transformer be more efficient over all the bands? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
It's measurably better than a tuner in terms of near-field strength;
14 turns of #12 insulated copper wire on a ferrite toroid ripped from an R7. How much coax is needed for that transmission line transformer? Mobiles are so inefficient, I'm always looking for that last 0.1 db. 73 H. NQ5H "Cecil Moore" wrote in message ... H. Adam Stevens wrote: With a simple toroidal autoformer the mobile rig sees 50 ohms resistive at resonance on all three bands. Got any idea what the efficiency of your autoformer is? I'm assuming a single coil for a primary, tapped down for the load. Would a 4:1 transmission line transformer be more efficient over all the bands? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Roy Lewallen wrote in message ...
That's much, much more difference than can be explained by the different conductivities of the metals. Either some very resistive alloys are involved, or there are differences between the antennas other than the type of metal. Roy Lewallen, W7EL By the way, I found a very nice and complete listing of conductivities of aluminum alloys at http://www.ndt-ed.org/GeneralResourc...ctivity_Al.pdf just after I posted last night. Others may find this useful. Even the worst of them is not as much as three times the DC resistivity of the best. So at RF, the worst aluminum alloy will have about twice the loss of the same diameter copper conductor. Cheers, Tom |
There are several variables here other than the conductivity of the
primary metal. Again, what you're seeing is not "the difference between copper and aluminum" as initially stated, but a number of other factors -- diameter, length, coating, and alloy --, combined. If the DC conductivity of two materials differs by a factor of two, their RF conductivity differs only by a factor of the square root of two, or about 1.4. This is because the skin depth is greater in the less conductive material, which partially offsets the conductivity difference. The relatively small difference in DC conductivity between pure copper and aluminum is further reduced by this effect, so you'll very seldom be able to see any difference. Roy Lewallen, W7EL H. Adam Stevens, NQ5H wrote: Roy I looked up the numbers. The Nott is 2" diameter bare copper 3' long. The Tarheel is 2" diameter painted aluminum 4' long. The Hi-Q is 1" diameter powder-coated aluminum 3' long. I used the same whip for all measurements. If we take the conductivity of copper to be 100, aluminum is then 60 and aluminum alloys are as low as 30. That's a factor of two between the Nott and Tarheel and the reduced surface area of the Hi-Q explains the additional resistance there. Considering the difference in surface area and resistivity among the antennas, the measured impedances seem quite reasonable to me. 73 H. NQ5H "Roy Lewallen" wrote in message ... That's much, much more difference than can be explained by the different conductivities of the metals. Either some very resistive alloys are involved, or there are differences between the antennas other than the type of metal. Roy Lewallen, W7EL H. Adam Stevens, NQ5H wrote: One place where I can clearly see the difference between copper and aluminum . . . |
"H. Adam Stevens, NQ5H" wrote in message ...
The Nott is 2" diameter bare copper 3' long. The Tarheel is 2" diameter painted aluminum 4' long. The Hi-Q is 1" diameter powder-coated aluminum 3' long. A 2" diameter bare copper rod or cylinder at 14MHz, 3' long, should have an RF resistance about 6 milliohms. The worst aluminum alloy you're likely to see should be about 12 milliohms; 24 for the 1" diameter. What am I missing here? How does that translate to a change from 9 ohms to 20 ohms to 30 ohms at the feedpoint? If the cause is resistance heating of the copper or aluminum tube, what's doing the impedance transformation, and how is it so efficient? That much loss should result in measurable temperature rise in the tube (or wherever the loss is), at 100-W power levels. Or perhaps my image of what you're measuring is all out of whack. Same loading coil in each case? I'd kind of expect the loading coil to be the main loss mechanism, if all the connections are tight. Puzzled and seeking enlightenment, Tom |
Thanks for all the excellent commentary guys!
My reason for the question was not really looking for a major improvement in the operation of the antenna, but more longetivity. I'm getting close to retirement and have moved to a new state. Whatever I put up, I want it to stay up and keep looking nice for about 20 years or longer. I lived in my last home for over 20 years, my backyard was almost solid copper from all the radials I had run over the years, plus when I first moved there, I did the entire backyard in 2x4 welded wire fabric, a layer of straw and some grass seed, then another layer of 2x4 welded wire fabric running the other way, then eventually sod over that. The last antenna I put up, a Butternut I used 3,500 feet of wire to make the radials and tied them to the welded wire fabric. I have set up an area at the top of a hill, am in the process of grading this area to flat, and hopefully within a couple of months have everything up except the antennas. I have cheap access to a plating company who will plate everything to keep it from corroding. When I checked into the price of gold plating, it was only a couple of bucks more than stainless silver or stainless brass and I was just thinking perhaps the gold would last longer and perhaps even work better. I have 1,225 sq. ft. of small link aluminum chain link fencing that is going to be buried as the start of my ground system in this graded area. I am also having a 62 foot fiberglass utility pole (50 feet after installation) installed at the corner of the house, this will hold my VHF/UHF antenna's and the my HF Inverted Vees, plus be the center of two dipoles, etc. Up near the antenna farm there will be another 30 foot fiberglass utility pole (after installation), which will be horizontal with the 50 foot pole at the house. I'm just trying to get everything planned out on paper before I do anything as it's easier to erase a pencil line than redo an antenna farm after the fact. In effect, I'm going to duplicate as closely as possible what I had in St. Loo and hopefully add a few more, since I now have the space. TTUL Gary |
What about silver plated RF connectors?
As far as that goes, there are also plenty of gold plated connectors out there. Jim N8EE "Richard Clark" wrote in message ... On Fri, 16 Apr 2004 20:40:53 -0400, "JLB" wrote: "S" wrote in message . net... silver is a better conductor than gold, but will tarnish very easily, might now be a good idea for what you are intending I thought that silver oxide was a decent conductor, which is why it is sometimes used as a plateing material. Hi All, It hardly matters unless you are speaking of switch contacts. Insulated wire's insulation is absolutely unconductive, and yet in the context of antennas it doesn't impact the wire's capacity to carry current. Oxidation products only become a problem at interfaces where they either resist current between the joined conductors, or create a semiconducting barrier. The technician is taught to clean surfaces of tarnish to bring bright metal into contact. Then crimp them (or twist the wire - same thing) for a gas tight seal. Then solder them to weather proof the seal (solder is never meant to be a mechanical join or the conductive path). Common practice allows for solder to provide more functionality than what I describe - this does not elevate the method. Barring the final solder, switch contact faces must meet the same conditions of bright metal and gas tight seals. This is often achieved by pressure (some mistake the so-called "wiping" action as meaning to scrub the oxide away - a useful metaphor but only that; otherwise switches would self demolish in very few operations) and a sustaining current (wet vs. dry contacts). 73's Richard Clark, KB7QHC |
|
On Sat, 17 Apr 2004 21:45:46 -0400, "JLB"
wrote: What about silver plated RF connectors? As far as that goes, there are also plenty of gold plated connectors out there. Hi Jim, What about them indeed? If they don't meet the requirements of bright untarnished metal, then they need pressure mating (all the good ones I know specify this - but deeply embedded within their core manufacturing specs) e.g. Amp RF connectors: "Insufficient contact force will give rise to metal to oxide junctions. The classic rectifiers were metal oxide by composition. "The applied mounting force is concentrated in the surface area of the protrusion which, on engagement with the panel, punctures the existing oxide layer to give a metal-to-metal, gas-tight junction." The gold plating, presumably, precludes giving rise to oxidation products; however, pressure then becomes an issue of mating surface area (Ohms). Every precision contact used for Resistance and Voltage standards (in the old days) were tapered brass plugs that could be wedged into the jack with a twist (pressure). They knew about gold then too, but brass served admirably. 73's Richard Clark, KB7QHC |
Well Tom, I'm just looking to explain the data: I'm puzzled as well.
Same truck, Durango with a ball mount right rear. Same MFJ analyzer. Same very short coax from inside the truck. Everything grounded with 2" copper strap. Same 14.300 MHz; Same whip. The measurements repeat reliably. Three motor-tuned antennas, Nott, Tarheel, Hi-Q. Three different impedances at resonance (ie purely resistive load.) 9, 20 and 30 ohms. Now I can see the radiation resistance being slightly higher with the Tarheel, it's a foot longer, but that hardly explains a factor of two. So it must be the loss resistance. Part of the difference is the base tube, and the copper/aluminum/diameter issue obeys the appropriate scaling laws. (BTW I think the Hi-Q is 1.5" diameter, but I'm not sure and I am not at the ranch where the antenna is stored.) When I adjust the tap on the transformer to give a 50 ohm load to the MFJ for each antenna, the Nott gives the greatest near-field signal strength. Perhaps a further investigation of the remaining sources of resistance is in order. The Hi-Q should have the least leakage, it's a beautiful piece of work. The Tarheel appears to be built of better materials than the Nott. (Lexan vs PVC for example.) Go down to 80 meters and they're all 10 ohms; coil losses clearly dominate there where radiation resistance is tiny. I think a complete solution to Maxwell's Equations would be helpful, but I'm busy at the moment. For all I know the paint or powder coating on the aluminum antennas is the real culprit. The Nott's just bare copper. What is the radiation resistance of an 8 foot whip antenna resonant in a 16.5 foot world? Just a bit less than 10 ohms, right? Maybe the comparison should be to BARE aluminum. Just my morning thought on a puzzle I've been looking at for several months. 73 es tnx fer qso de nq5h k "Tom Bruhns" wrote in message m... "H. Adam Stevens, NQ5H" wrote in message ... The Nott is 2" diameter bare copper 3' long. The Tarheel is 2" diameter painted aluminum 4' long. The Hi-Q is 1" diameter powder-coated aluminum 3' long. A 2" diameter bare copper rod or cylinder at 14MHz, 3' long, should have an RF resistance about 6 milliohms. The worst aluminum alloy you're likely to see should be about 12 milliohms; 24 for the 1" diameter. What am I missing here? How does that translate to a change from 9 ohms to 20 ohms to 30 ohms at the feedpoint? If the cause is resistance heating of the copper or aluminum tube, what's doing the impedance transformation, and how is it so efficient? That much loss should result in measurable temperature rise in the tube (or wherever the loss is), at 100-W power levels. Or perhaps my image of what you're measuring is all out of whack. Same loading coil in each case? I'd kind of expect the loading coil to be the main loss mechanism, if all the connections are tight. Puzzled and seeking enlightenment, Tom |
Thanks Richard
You may have solved my problem! I will definitely check into using bronze. Thanks Gary |
I have 1,225 sq. ft. of small link aluminum chain link fencing that is going to be buried as the start of my ground system in this graded area. which will most likely disintegrate in the ground into white powder. Yuri, K3BU |
"Yuri Blanarovich" wrote in message ... I have 1,225 sq. ft. of small link aluminum chain link fencing that is going to be buried as the start of my ground system in this graded area. which will most likely disintegrate in the ground into white powder. Anyone remember "beldfoil" aluminum sheilded cables? It was sold in the 70's as a replacement for copper shielding. After a few months exposure to salt air, the aluminum turned into white powder, leaving only the drain wire as a sheild. Not very effective. I think they've given up on that, and gone back to copper, though I have seen copper shield used along with the aluminum-mylar material. |
|
But then, maybe SILVER (AG) ! Silver is one heck of a conductor, and what,
pray , when it Oxidizes (AG - O) ? Turns out that the conductivity of Silver Oxide is almost as great as SILVER! (but, as for the effeciency, , unless severe resistance (perhaps in a hi "Q" loading coil for a mobile) Doubt would make much difference that could be detected! Jim NN7K -- No trees were killed in the sending of this message. However, a large number of electrons were terribly inconvenienced ! "H. Adam Stevens, NQ5H" wrote in message ... Hi Roy; It's worse than that: Copper will diffuse throught the gold and pile up on the surface. I showed that with an Auger microprobe at Motorola decades ago. So to go to a gold surface, nickel is mandatory, then a thick gold coating; Too expensive! It's not like the switch from aluminum to copper, which is a 2x resistivity improvement. You just can't beat plain old copper. 73 H. NQ5H "Roy Lewallen" wrote in message ... I've seen real-life cases with high-Q microstrip structures where gold plating actually caused a significant lowering of efficiency. As you point out, nickel is used as a barrier metal to prevent alloying of the gold with the underlying copper. If the gold isn't at least several skin depths thick, significant current flows in the nickel. Nickel is a particularly poor RF conductor, very much worse than copper, because the skin depth in nickel is decreased dramatically by its ferromagnetic permeability. So, if you're able to calculate skin depth, and know what you're doing, and are willing to use quite a bit of gold (particularly necessary at HF and below) you can achieve efficiency with gold plating that's pretty much indistinguishable from that of copper. If you don't know what you're doing, it is possible to substantially degrade the efficiency by gold plating. I'm sure somebody could be conned into buying one, though. Roy Lewallen, W7EL Gary V. Deutschmann, Sr. wrote: Hi Gang Since the radiation of an antenna is done primarily on the surface of the elements (or wire) would gold plating the elements increase the efficiency of the antenna in any way? Gold sounds expensive, but if thin enough, one ounce of gold could plate an entire football field. Brass corrods, nickel is usually used as the first plating before another metal like gold is plated over that. If the cost for gold over the cost of brass is only about 1 buck per foot of element length, making cost not relavent to the question. Would a gold plated antenna work better than aluminum or nickel plated? TTUL Gary |
Ah, finally, someone who knows what the conductivity of silver oxide is.
Although I believe silver sulfide is much more common than oxide, I've been able to find the conductivity of the sulfide but not the oxides. Just what are the conductivities of the silver oxides (AgO and Ag2O)? Which are we most likely to find on the outsides of wires? Are they really more common than the sulfide? Roy Lewallen, W7EL Jim wrote: But then, maybe SILVER (AG) ! Silver is one heck of a conductor, and what, pray , when it Oxidizes (AG - O) ? Turns out that the conductivity of Silver Oxide is almost as great as SILVER! (but, as for the effeciency, , unless severe resistance (perhaps in a hi "Q" loading coil for a mobile) Doubt would make much difference that could be detected! Jim NN7K |
Roy Lewallen wrote:
Ah, finally, someone who knows what the conductivity of silver oxide is. Although I believe silver sulfide is much more common than oxide, I've been able to find the conductivity of the sulfide but not the oxides. Just what are the conductivities of the silver oxides (AgO and Ag2O)? Which are we most likely to find on the outsides of wires? Are they really more common than the sulfide? Roy Lewallen, W7EL An interesting and eventually amusing link on silover sulfide http://www.eecs.cwru.edu/misc/AMANDA...er_revised.doc another: http://www.brushwellman.com/alloy/tech_lit/sep02.pdf and this: http://nepp.nasa.gov/whisker/reference/tech_papers/chudnovsky2002-paper-silver-corrosion-whiskers.pdf It is interesting that the NASA paper refers to silver sulfide as non-conductive, while the first paper gives a short and tantilizing tidbit about forcing it into conductivity. Hope you find the links interesting! - Mike KB3EIA - |
Mike,
Thanks very much for the links. They furnished quite a bit of information about silver, its alloys, and its salts, that I didn't know. They do seem to support what I had thought about sulfide being more common than oxide, and added chloride to the list of common tarnishes. And maybe the reason for the elusiveness of information on the conductivity of silver oxide is because of the strange nonlinear effects reported in the first paper. Hopefully Jim will be able to fill us in about that, since he apparently has some information on the oxides. I'm frankly startled that any oxide can have conductivity within even a few orders of magnitude of a good pure metal, so I hope he'll post the information soon. One of the links notes that only silver alloys (particularly with copper) tend to oxidize, so in order to get a coating of silver oxide, you'd need to coat your wire not with pure silver, but with an alloy that's somewhat more resistive than copper to begin with. Does that mean, Jim, that the conductivity of the plated wire would actually improve as it oxidizes? A paper I read some time ago showed that silver plating nearly always consists not of pure silver but of some alloy (as one of the links pointed out), and nearly all those alloys have a conductivity less than copper -- some, much less. So if you want to reap whatever benefit there might be in silver corrosion products over copper ones, you'll have to put up with lower conductivity in the uncorroded wire. Seems to me to make more sense to use enameled or insulated copper wire to begin with, but I guess some folks think the appearance of silver is worth the hassle. The only resistivity information I have is for AgS, which is apparently a common corrosion product, and its resistivity is about 100,000 times as great as silver. This isn't necessarily bad, since both a perfect conductor and a perfect insulator provide a lossless coating. The loss incurred by conductors of intermediate quality depends on the frequency and coating thickness, so it can be hard to draw conclusions about what compound might be better than another except in a specific case. Roy Lewallen, W7EL Mike Coslo wrote: Roy Lewallen wrote: Ah, finally, someone who knows what the conductivity of silver oxide is. Although I believe silver sulfide is much more common than oxide, I've been able to find the conductivity of the sulfide but not the oxides. Just what are the conductivities of the silver oxides (AgO and Ag2O)? Which are we most likely to find on the outsides of wires? Are they really more common than the sulfide? Roy Lewallen, W7EL An interesting and eventually amusing link on silover sulfide http://www.eecs.cwru.edu/misc/AMANDA...er_revised.doc another: http://www.brushwellman.com/alloy/tech_lit/sep02.pdf and this: http://nepp.nasa.gov/whisker/reference/tech_papers/chudnovsky2002-paper-silver-corrosion-whiskers.pdf It is interesting that the NASA paper refers to silver sulfide as non-conductive, while the first paper gives a short and tantilizing tidbit about forcing it into conductivity. Hope you find the links interesting! - Mike KB3EIA - |
Hi Yuri
I lived in my last house for slightly over 20 years. Although a high percentage of the welded wire fabric decomposed over that time, leaving iron in the soil, evidenced by all of my hydrangeas turning bright blue, the areas of aluminum fencing never did deteriorate. In fact, the fencing I will be using is the same fencing that surrounded my property for those 20 years, with the lower ends buried over a foot into the ground. Not the actual fence, but a partial roll I had left over after constructing the fence. That had been in storage all this time. If I could find a company that makes this same small weave aluminum fencing I would have them do my whole yard at my new house. But I have not found it available anywhere. Perhaps as you pointed out, it don't hold up under certain conditions. My aunt lived in Florida for awhile, she had the same type awnings installed, by the same manufacturer even, that she had installed some 25 years earlier in St. Loo, they didn't hold up but only 4 years and were full of holes. Assumably from the salt air. TTUL Gary |
Gary Deutshmann, Sr. wrote:
"If I could find a company that makes this same small weave aluminum fencing I would have them do my whole yard at my new house." Copper radials could be better. Ed Laport who worked with Brown, Lewis, and Epstein at RCA wrote on page 121 of "Radio Antenna Engineering": "The radial disposition of wires in a buried or surface ground system is dictated by the natural paths for returning ground currents. Meshes opf crossed wires which were once widely used, should not be used with vertical radiators because the return paths are not direct and eddy-current losses in the closed loop circuits of the mesh can be appreciable." Best regards, Richard Harrison, KB5WZI |
Richard Harrison wrote:
Ed Laport who worked with Brown, Lewis, and Epstein at RCA wrote on page 121 of "Radio Antenna Engineering": "The radial disposition of wires in a buried or surface ground system is dictated by the natural paths for returning ground currents. Meshes opf crossed wires which were once widely used, should not be used with vertical radiators because the return paths are not direct With a fine enough ground spacing, though, I would think that the path is 'direct enough?' and eddy-current losses in the closed loop circuits of the mesh can be appreciable." I thought the entire point of the ground plane was that the induced currents are necessary to make up for the current sources that are 'supposed' to have come from the 'missing' half of the antenna? |
Hi Richard
Thanks for the advice! However, I do use copper radials from each vertical. From my Butternut HF9Vw/160 I used 3,500 feet of copper wire to make the radial bed. These were tied to an 8 foot grounding stake and connected to the antenna's grounded mast. I have antennas that did not work well at all when placed in the front or side yard, but worked quite well in the back yard over all of that mesh of buried wire! Because of this, I'm planning on trying to duplicate as closely as possible, what I had that worked so well for the last 20 years. TTUL Gary |
| All times are GMT +1. The time now is 04:50 AM. |
|
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com