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Stainless Steel Wire - OK for antennas?
I recently acquired a large quantity of very flexible stranded
stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave |
On Mon, 23 Aug 2004 18:11:53 -0400, Dave wrote:
just a matter of being too finiky? Hi Dave, Yes. No one is going to notice something less than half a dB (which by definition is unnoticeable). 73's Richard Clark, KB7QHC |
I recently acquired a large quantity of very flexible stranded stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave The best use of it would be for the Beverage receiving antennas. Extra resistance helps to retard the reflected wave and "sharpens" the pattern. Otherwise it would beat the heck out of DLM, EH, CFA or Fractuled antennas. Yuri, K3BU |
I recently acquired a large quantity of very flexible stranded
stainless steel wire at a garage sale. was wondering if this could be used for wire antennas for HF. Of course it could be used. The resistance loss is insignificant. It will actually increase your SWR bandwidth. Certain Comercial Ham antennas use a fixed resistor to improve bandwidth and lower SWR. So go for it and see what happens. 73 Gary N4AST |
It will be strong but the trade-off is the higher resistance/loss.
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Oly thing I don't like about the stuff is that it can cut you, if too small. Copper just breaks. |
The best thing about it is - you already have it. Use it.
"Dave" wrote in message ... I recently acquired a large quantity of very flexible stranded stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/30/2004 |
On Mon, 23 Aug 2004 22:26:34 GMT, Richard Clark
wrote: Yes. No one is going to notice something less than half a dB (which by definition is unnoticeable). This may be true for upper HF, but for MF/low-HF dipoles the situation may be a bit different. The dipole length is inversely proportional to frequency and the skin depth (and hence AC resistivity) is directly proportional to the square root of frequency. Thus the net effect is that the total dipole resistance is inversely proportional to the square root of the frequency. Thus a dipole cut for the lower band has a larger resistance than an antenna cut for a higher bands, provided that the same wire type is used. The resistivity and skin depth depends on the material and apparently varies quite a lot depending of the type of stainless steel, since various sources give quite different values. The skin depth for copper at 1.8 MHz is about 50 um, while for some stainless steel, it appears to be around 200 um. Both values are well below the OP's 850 um conductor diameter. One source claimed that the stainless steel has a 52 times DC resistivity compared to copper, so factoring in the large skin depth, the AC resistivity at 1.8 MHz would be more than 12 times that of the copper wire of the same size. An other source specified the stainless steel resistivity as 43E-8 ohm/m and while the 0.85 um diameter conductor with 0.2 mm skin depth would have an effective cross section of 0.4 mm2 and with the 80 m length of the 1.8 MHz dipole, the total resistance would be 86 ohms. Compare this to the nominal 73 ohm radiation resistances for a half wave dipole and more than half of the transmitter power would be dissipated in the losses. However, since the current distribution is not uniform along the dipole, the effective losses are not that quite as bad. On the other hand, if the dipole is close to the ground, the radiation resistance is well below 73 ohms, so again, we are in the -3 dB efficiency ballpark value. With a 1500 W transmitter, the losses are about 1 W/m, this should help melting any frost accumulated on the wire during a cold night:-). Now the question is, is this 80 m stainless steel strong enough to support itself, even if supported in the middle at the feed point. For a copper wire with the same diameter, the resistance would have been below 10 ohms and the losses about 0.5 dB. Paul OH3LWR |
On Tue, 24 Aug 2004 09:56:29 +0300, Paul Keinanen
wrote: Compare this to the nominal 73 ohm radiation resistances for a half wave dipole and more than half of the transmitter power would be dissipated in the losses. Hi Paul, And still, no one would notice. In fact, I gave the loss 100 Xs copper, lowered the frequency to 1MHz and saw roughly 6dB loss - the "standard" S-Unit, against which propagation variations would toss that around to wider variation. I suppose it wouldn't do for EME, but I don't know any work at 1MHz for EME. Still, and all, this determination is easily within the scope of the free distribution of EZNEC which allows any user to make an informed decision about a choice being OK. 73's Richard Clark, KB7QHC |
On Tue, 24 Aug 2004 09:56:29 +0300, Paul Keinanen
wrote: Two corrections: An other source specified the stainless steel resistivity as 43E-8 ohm/m The unit of resistivity is of course ohm m (not ohm/m). With a 1500 W transmitter, the losses are about 1 W/m, this should help melting any frost accumulated on the wire during a cold night:-). With 50 % efficiency (-3 dBd gain), the losses are about 800 W and when divided evenly along 80 m will give 10 W/m (not 1 W/m), which in addition to frost will also melt ice and keep the birds away :-). Paul OH3LWR |
That's what they use for mainstay antennas on yachts. they work well (the
groundplane helps of course). Brad VK2QQ "Dave" wrote in message ... I recently acquired a large quantity of very flexible stranded stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave |
You've gotten a lot of conflicting advice. Let me add mine.
Without going through the numbers in detail, Paul, OH3LWR's analysis looks sound. However, he neglected one factor. The skin depth is also inversely proportional to the square root of the permeability. Some stainless steels are ferromagnetic, with a permeability I'd guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance, by at least a factor of 10. If you do the analysis with realistic numbers, you'll find that loss can become at least several dB if the wire is magnetic, and worse with longer (40 or 80 meter) dipole lengths. So my recommendation is to check the wire with a magnet. If it's magnetic, expect longer antennas to be quiet and broadband (which amateurs crave) but lossy (which most don't seem to care about). Non-magnetic stainless isn't likely to produce objectionable loss, except perhaps at an 80 meter dipole length or longer. You can get a qualitative feel for the loss by comparing the 2:1 SWR bandwidth of an antenna made from the wire with the bandwidth from a dipole made from copper wire. The broader it is, the lossier it is. Roy Lewallen, W7EL Dave wrote: I recently acquired a large quantity of very flexible stranded stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave |
More succinctly, it all boils down to -
Copper antenna wires are so efficient (say 98 percent) an increase in loss by 10 times (down to 80 percent) is not noticeable. --- Reg |
On Tue, 24 Aug 2004 12:48:29 -0700, Roy Lewallen
wrote: Without going through the numbers in detail, Paul, OH3LWR's analysis looks sound. However, he neglected one factor. The skin depth is also inversely proportional to the square root of the permeability. Some stainless steels are ferromagnetic, with a permeability I'd guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance, by at least a factor of 10. My skin depth figures are base upon a quick web search, so I have no idea how typical these figures might be or is it likely that the OP would have a similar wire. If you do the analysis with realistic numbers, you'll find that loss can become at least several dB if the wire is magnetic, and worse with longer (40 or 80 meter) dipole lengths. If my original assumptions are correct, the original poster (OP) should also check the dissipation of each meter of antenna conductor, since above 1.8 MHz, it appears that the power dissipation per meter is slightly higher than at 1.8 MHz, thus the wire temperature is higher (and might even affect the sag of the wire when transmitting:-). So my recommendation is to check the wire with a magnet. If it's magnetic, expect longer antennas to be quiet and broadband (which amateurs crave) but lossy (which most don't seem to care about). Non-magnetic stainless isn't likely to produce objectionable loss, except perhaps at an 80 meter dipole length or longer. In addition, since the OP had a large quantity of the wire, I would suggest building a conical dipole antenna from the wire. Not only will the current (and losses) in each leg be lower, but also the bandwidth would be larger. Paul OH3LWR |
This is interesting. Are the negative effects due to the fact that induced
magnetism will persist, and thus set up additional impedence on the line ? and does this skin effect caused by the magnetism vary significantly with frequency ? "Roy Lewallen" wrote in message ... You've gotten a lot of conflicting advice. Let me add mine. Without going through the numbers in detail, Paul, OH3LWR's analysis looks sound. However, he neglected one factor. The skin depth is also inversely proportional to the square root of the permeability. Some stainless steels are ferromagnetic, with a permeability I'd guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance, by at least a factor of 10. If you do the analysis with realistic numbers, you'll find that loss can become at least several dB if the wire is magnetic, and worse with longer (40 or 80 meter) dipole lengths. So my recommendation is to check the wire with a magnet. If it's magnetic, expect longer antennas to be quiet and broadband (which amateurs crave) but lossy (which most don't seem to care about). Non-magnetic stainless isn't likely to produce objectionable loss, except perhaps at an 80 meter dipole length or longer. You can get a qualitative feel for the loss by comparing the 2:1 SWR bandwidth of an antenna made from the wire with the bandwidth from a dipole made from copper wire. The broader it is, the lossier it is. Roy Lewallen, W7EL Dave wrote: I recently acquired a large quantity of very flexible stranded stainless steel wire at a garage sale. It is about 0.85 mm (around 1/32 inch) in diameter and extremely strong. I was wondering if this could be used for wire antennas for HF. I seem to remember seeing something about SS not being ideal. Is this a real consideration or just a matter of being too finiky? Thanks - Dave --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
Hal Rosser wrote:
This is interesting. Are the negative effects due to the fact that induced magnetism will persist, and thus set up additional impedence on the line ? Not if I understand you correctly. The effect I'm describing isn't an impedance due to inductance, as you seem to imply. It's that the density of an AC current decays exponentially from the surface downward into a conductor, increasing the resistance of that conductor (known as skin effect). The skin depth is a measure of how rapidly it decays and therefore how resistive a conductor will be, and the skin depth is a function of the frequency, the DC conductivity of the material, and its permeability. I'm sorry I'm not able to explain why increased permeability decreases the skin depth except that it's due to the increased magnetic field opposing current into the conductor (which might be what you tried to say). I'm sure you can find a lot about skin effect on the web, as well as in any electromagnetics text. and does this skin effect caused by the magnetism vary significantly with frequency ? I honestly don't know the answer to this. The permeability of ferromagnetic materials does vary with frequency, in what appears to be an unpredictable way. Whether this value or the DC permeability should be used for calculation, I don't know. I suspect that the DC permeability should be used, and the permeability change with frequency regarded as a change in effective permeability -- but I don't know for sure. I'd really appreciate it if anyone who does know would comment. Of course, skin depth varies with frequency even if the permeability is constant. Roy Lewallen, W7EL |
Roy, W7EL wrote:
"Some stainless steels are ferromagnetic, with a permability I`d guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance by a factor of 10." Being ferromagnetic does not disqualify an antenna material. Most CB whips are stainless steel. They aren`t too lossy because they are only about 1/4-wave at 27 MHz and must be large enough in diameter to be durable. In the range of 0.55 MHz to 1.7 MHz, most transmission is from ordinary non-stainless steel towers. The only coating on many of these is paint. The cross-section to length ratio is economically small, but I doubt the loss added by using nonplated steel could be measured. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote in message ... Roy, W7EL wrote: "Some stainless steels are ferromagnetic, with a permability I`d guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance by a factor of 10." Being ferromagnetic does not disqualify an antenna material. Whoa... now you are misquoting Roy. He never did DISQUALIFY the use of stainless steel He clearly stated in technical terms what stainless steel lacked in an area that is important with respect to radiation. I suspect the use of stainless steel for consumer antennas is an engineering one to prevent rust and antenna mechanical distortion which outways the loss in efficiency. It was this difference that Roy was alluding to and is the reason why amateurs take note of the characteristics of material used and is why aluminum,copper and the like is used in the communication world. Many in the amateur community allude to communication obtained with a wet string but in no way are they DISQUALIFYING the use of aluminum and the like. Stop throwing mud and get with the program. You will never,ever make the smallest piece of your mud stick to the likes of Roy and Tom with mis quotations. Art Art Most CB whips are stainless steel. They aren`t too lossy because they are only about 1/4-wave at 27 MHz and must be large enough in diameter to be durable. In the range of 0.55 MHz to 1.7 MHz, most transmission is from ordinary non-stainless steel towers. The only coating on many of these is paint. The cross-section to length ratio is economically small, but I doubt the loss added by using nonplated steel could be measured. Best regards, Richard Harrison, KB5WZI |
On Thu, 26 Aug 2004 16:05:46 GMT, "
wrote: Stop throwing mud more trolling |
I suspect the use of stainless steel for consumer antennas
is an engineering one to prevent rust and antenna mechanical distortion which outways the loss in efficiency. ================================ Your suspicion is well founded. ECONOMICS INVARIABLY RULES. --- Reg |
You're correct that CB whips, 2 meter whips, AM broadcast towers, and
the like are just fine because of their large diameter. But think about it a little bit. If you reduce the frequency by a factor of two, the length of a resonant antenna increases by a factor of two. The skin depth decreases by a factor of the square root of two, so the resistance per unit length increases by this factor. So at half the frequency, the resistance of a resonant antenna has increased by the square root of two. Furthermore, you don't typically use 1/4 inch diameter wire for an HF dipole, for example. (And most hams presumably wouldn't make an HF dipole from surplus broadcast towers -- but then I haven't seen your station.) Assuming you're using a resonant antenna of constant diameter, the loss gets higher as the frequency gets lower. Now go back and read what I wrote. Notice that I said that the wire was most likely to be a problem with antennas on the order of an 80 meter dipole length. Now you understand (I hope) why that qualification. If you use an antenna at a frequency higher than its primary resonance (such as a 40 meter dipole on 15, or a G5RV on a high frequency band), the loss gets greater yet, since the skin depth decreases with frequency. Roy Lewallen, W7EL Richard Harrison wrote: Roy, W7EL wrote: "Some stainless steels are ferromagnetic, with a permability I`d guess at 100 or more. That reduces the skin depth, and therefore increases the RF resistance by a factor of 10." Being ferromagnetic does not disqualify an antenna material. Most CB whips are stainless steel. They aren`t too lossy because they are only about 1/4-wave at 27 MHz and must be large enough in diameter to be durable. In the range of 0.55 MHz to 1.7 MHz, most transmission is from ordinary non-stainless steel towers. The only coating on many of these is paint. The cross-section to length ratio is economically small, but I doubt the loss added by using nonplated steel could be measured. Best regards, Richard Harrison, KB5WZI |
Roy, W7EL wrote:
"Notice that I said that the wire was most likely to be a problem with antennas on the order of an 80 meter dipole length." 80 meters isn`t the lowest nor the highest frequency ham band, but could be a problem for various reasons. Loss is directly proportional to resistance in the familiar current squared times resistance formula. Resistance increases due to skin effect only as the square root of the frequency while resistance varies directly with the conductor length which varies inversely with frequency. Loss gets worse for a given wire size as frequency drops because you need longer wire for a 1/4 wavelength. It doesn`t get worse as fast as it would if there were no skin effect because as frequency lowers, current penetration grows and wire resistance drops due to reduction of the skin effect. But, the longer wire is inevitable along with its higher resistance at the lower frequency. At RFE, as soon as a new frequency became available we would often erect a Signal Corps rhombic kit and start broadcasting. These weren`t made for 100KW so the dissipation lines soon melted and the rhombics became bidirectional. At the end of WW-2, many Central Europeans fled to South America. When we strengthened and replaced our dissipation lines, we discovered we had built a large loyal audience among the fugitives. Not too surprising since we were programming with some of their favorite entertainers who were also exiles. Too bad we had to eliminate the signal flooding South America, but other broadcasters had claims on the frequencies we were using for a South American audience. Best regards, Richard Harrison, KB5WZI |
|
There's been much discussion.
The end-to-end RF loss resistance of a half-wave copper dipole is given by - R = Squareroot( Lambda / 2 ) / D ohms. Where Lambda is the free-space wavelength in meters and D is wire or rod diameter in millimetres. Much more simple and easier than measuring it. For example, the overall loss resistance of a 14 awg, 40m dipole, is 2.73 ohms. For another metal, multiply R by the square root of resistivity and the square root of permeability, both relative to copper. ---- Reg, GFGQ |
Walter, W2DU wrote:
"Were the rhombic dissipation lines made of high resistance wire?" The Signal Corps rhombic kits we had were manufactured by the Wind Turbine Company and were most distinguished by a unique one-piece ceramic insulator designed to hold both transmission line cables as it sat atop a support. The lines were made of 3 no. 12 Copperweld wires twisted together. We discarded these as our transmission lines needed larger cable and wider spacing for the same 600-ohm line. The kit included short tower sections meant as transmission line supports. Triangular tower sections were made of (3) vertical steel rods with wire sides where the wire weaved back and forth between rods. Every steel piece was welded at intersections and assemblies were all hot-dipped galvanized. They were good structures. The rhombic curtain was a 3-cable type, spread apart vertically at the side towers to reduce impedance variations. The same Copperweld cable, (3) twisted no. 12`s, was used for each of the 3 separate cables, as that used in the transmission line. An exponentially tapered feedline was used to attach the wide-spaced attachment to the curtain overhead to the more narrow transmission line down below. Its aim was matching 800 ohms to 600 ohms. My recollection is that the dissipation line at the far end of the rhombic terminus was itself made to match 800 ohms rather than using another tapered line. Too many insulators of varied size, I suppose. So, the down line at the far end had uniform spacing. The dissipation line itself was relatively small stainless steel wires until we replaced them with much larger wire and spacings. It ran back and forth down the centerline of the rhombic. The rhombics were aimed at central Europe from Portugal. Their reverse radiation bathed nearly all of South America with strong signals for as long as the rhombics were without dissipation lines. I have no statistics on where the fugitives concentrated. I know that before WW-2, many Europeans had sought opportunity in South America. The war made it plain that the persecuted needed a new haven outside of Europe. It was also clear that the persecutors might escape responsibility if they fled Europe following the war. I`ve personally been struck by the numbers of people I`ve encountered in Santiago de Chile, Buenos Aires, and Rio de Janeiro, obviously residents, not tourists, speaking Central European languages. A lot of these newer arrivals already had families residing in those countries. There are a lot of Brits in South America too. In Argentina, many came to do good and stayed to do well. Hurlingjham is a British neighborhood in B.A. with its own polo grounds. People send their fourth generation offspring back "home to the U.K." for education. The main street (high road) of Santiago is Avenida O`Higgins. Best regards, Richard Harrison, KB5WZI |
O'Higgins is not English. He was an important part of the fight to
breakaway from Spain. I found the descriptions of the rhombics interesting. Thanks. My son changed my operating system over the weekend. The change was long overdue. This is first test of whether I am able to post. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Richard Harrison" wrote snip There are a lot of Brits in South America too. In Argentina, many came to do good and stayed to do well. Hurlingjham is a British neighborhood in B.A. with its own polo grounds. People send their fourth generation offspring back "home to the U.K." for education. The main street (high road) of Santiago is Avenida O`Higgins. Best regards, Richard Harrison, KB5WZI |
On Mon, 30 Aug 2004 21:12:06 -0400, wrote:
O'Higgins is not English. He was an important part of the fight to breakaway from Spain. "Richard Harrison" wrote snip Hurlingjham is a British neighborhood in B.A. with its own polo grounds. People send their fourth generation offspring back "home to the U.K." for education. The main street (high road) of Santiago is Avenida O`Higgins. Hi All, Buenos Aires certainly does not lack for Spanish names in its various barrios and along its streets, but not all of them are mono-cultural. Notable in both their in-country airport and a road nearby is the name Jorge Newberry. The Thames can be found in Palermo. You can stay the night in the Hotel Waldorf or Hotel Lancaster in the Retiro and shop at Kelly's - the Irish Embassy is also located in this barrio. There is also the British Arts Center in the Retiro, as well as the Torre de los Ingleses (a monument to the English) across the street from the Plaza Libertador General San Martin (which contains a wall of names of the fallen in the Malvinas). When I visited the Cementario de la Recoleta there were plenty of English and Irish surnames from 150 years ago - not unusual at all. However, Buenos Aires also sports a very large population of Italians and is the home to the largest settlement of Jews outside of Europe and the US. When we were in La Plata, we ate at schnitzel at a Bavarian styled restaurant. 73's Richard Clark, KB7QHC |
Richard Clark wrote:
"You can stay the night in the Hotel Waldorf or the Hotel Lancaster in the Retiro and shop at Kelly`s-" I usually stayed at the Claridge just off the pedestrian shopping street La Calle Florida. The company installed me there on my first arrival in Buenos Aires as I had no preference. When I returned there after a 6 month absence and was joyfully greeted by my name from the doorman. I was hooked. On one of my 6 month tours in Argentina, I decided to give the Sussex Hotel across the street from the Claridge a try as all the oil field hands seemed to stay there. I arrived out of cigarettes, dying for a smoke, and asked the desk clerk if the Sussex had a smoke shop. When the clerk said no, I told him to send my luggage on up to my room while I shopped for cigarettes. The clerk spyed me when I re-entered the hotel and called me over to give me a message from my wife who was very eager to see me. I thanked him although at that time I`d never been married, but I had discovered the main attraction of the Sussex Hotel! And they say a gringo is no damn good when he speaks Spanish! Best regards, Richard Harrison, KB5WZI |
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