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John S wrote in :
Maybe because NFPA 70 costs $150 US? Yes, standards are expensive things and it is a frustration when researching. Anyway, NFPA makes recommendation on the wires for ham antennas specifically, and it may be binding in some places. I suspect the reason for ignoring it is that the advice is unaccepable to most hams. That said, it does seem over the top in some areas, and is hardly comprehensive in its thinking. For example, the prescription for feedlines seems to not be aware of the existence and use of coax. I guess it is these gaps that give critics the basis for arguing against the whole thing. Anyway, in respect of antenna wires, it does not 'permit' annealled copper or other low strength materials, and it 'requires' a minimum conductor diameter of #14 for up to 150' span. They may have had in mind the risk to persons and property where low strength conductor are broken in high wind and make contact with power lines. Owen |
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#2
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On 7/31/2011 3:26 PM, Owen Duffy wrote:
John wrote in : Maybe because NFPA 70 costs $150 US? Yes, standards are expensive things and it is a frustration when researching. Anyway, NFPA makes recommendation on the wires for ham antennas specifically, and it may be binding in some places. I suspect the reason for ignoring it is that the advice is unaccepable to most hams. That said, it does seem over the top in some areas, and is hardly comprehensive in its thinking. For example, the prescription for feedlines seems to not be aware of the existence and use of coax. You refer to the "continuously enclosed metallic shield", I suspect. I guess it is these gaps that give critics the basis for arguing against the whole thing. Anyway, in respect of antenna wires, it does not 'permit' annealled copper or other low strength materials, and it 'requires' a minimum conductor diameter of #14 for up to 150' span. They may have had in mind the risk to persons and property where low strength conductor are broken in high wind and make contact with power lines. That is precisely why. (ice loads, too) |
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#3
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On 8/1/2011 7:52 PM, Jim Lux wrote:
On 7/31/2011 3:26 PM, Owen Duffy wrote: John wrote in : Maybe because NFPA 70 costs $150 US? Yes, standards are expensive things and it is a frustration when researching. Anyway, NFPA makes recommendation on the wires for ham antennas specifically, and it may be binding in some places. I suspect the reason for ignoring it is that the advice is unaccepable to most hams. That said, it does seem over the top in some areas, and is hardly comprehensive in its thinking. For example, the prescription for feedlines seems to not be aware of the existence and use of coax. You refer to the "continuously enclosed metallic shield", I suspect. I guess it is these gaps that give critics the basis for arguing against the whole thing. Anyway, in respect of antenna wires, it does not 'permit' annealled copper or other low strength materials, and it 'requires' a minimum conductor diameter of #14 for up to 150' span. They may have had in mind the risk to persons and property where low strength conductor are broken in high wind and make contact with power lines. That is precisely why. (ice loads, too) NFPA (according to what you posted) requires heavier gauge wire for transmitting than for receiving. Transmitting makes the wire weigh more? |
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#4
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On 8/2/2011 11:24, John S wrote:
On 8/1/2011 7:52 PM, Jim Lux wrote: On 7/31/2011 3:26 PM, Owen Duffy wrote: John wrote in : Maybe because NFPA 70 costs $150 US? Yes, standards are expensive things and it is a frustration when researching. Anyway, NFPA makes recommendation on the wires for ham antennas specifically, and it may be binding in some places. I suspect the reason for ignoring it is that the advice is unaccepable to most hams. That said, it does seem over the top in some areas, and is hardly comprehensive in its thinking. For example, the prescription for feedlines seems to not be aware of the existence and use of coax. You refer to the "continuously enclosed metallic shield", I suspect. I guess it is these gaps that give critics the basis for arguing against the whole thing. Anyway, in respect of antenna wires, it does not 'permit' annealled copper or other low strength materials, and it 'requires' a minimum conductor diameter of #14 for up to 150' span. They may have had in mind the risk to persons and property where low strength conductor are broken in high wind and make contact with power lines. That is precisely why. (ice loads, too) NFPA (according to what you posted) requires heavier gauge wire for transmitting than for receiving. Transmitting makes the wire weigh more? No but it does make it more dangerous to persons and things on which it might fall if it breaks. -- Tom Horne, W3TDH |
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#5
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On 8/2/2011 7:33 PM, Tom Horne wrote:
No but it does make it more dangerous to persons and things on which it might fall if it breaks. Come on, Guys! While it's a great idea to follow every official code and reccomendation, and that no one in their "right mind" would ever consider anything less than the lowest gauge copperweld wire for their antenna, the original question is answerable by "Yes, you can make a serviceable antenna out of speaker wire." Will it stay up as long as a Copperweld antenna held in place by1/4 inch thick 100 percent nylon rope? No it won't. But it will work. Surprisingly well, in fact. Let the new guys learn, and throw up antennas that work. As they have to put up a new one every so often, they will eventually learn about more long lasting antennas, as well as ones that might have a better pattern, and other effects that bear on performance. But the idea that hams are responsible for restrictive covenents (in reality, Cable television is more responsible for antenna covenants than anything else) or that the choice of speaker wire is going to electrocute the neighbors is doing a disservice to the new guys and gals. I can say this with some conviction because I was one of those noobs once, and nearly didn't even get on HF because with all the input, I gave up on putting up an antenna because nothing was good enough. I didn't have enough space, I didn't have enough height. There just wasn't any use in getting on the low bands. I needed a separate antenna for every band because ladder line was awful and traps were bad and every other option was awful except for some idealized correct antenna, coax fed, at the proper height. - 73 de Mike N3LI - |
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#6
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On Tue, 02 Aug 2011 23:11:33 -0400, Mike Coslo rearranged some electrons
to say: But it will work. Surprisingly well, in fact. My present HF antenna is a piece of 4-conductor ribbon cable, with 60 feet of each outside conductor pulled off to make a 120 foot dipole, the rest of the cable being used as a feedline to a balun and thence to a tuner. Is it ideal? No. But it's good enough to work 45 states so far on 75m, a few dozen DX contacts on 20 and 40m, etc. Plus, it's nearly invisible against the side of the house. During field day, I used a homemade doublet fed with 450 ohm ladder line to the same tuner, remotely mounted in a waterproof box, I was able to work 15m and 80m on the same antenna, made a few hundred contacts. Eventually (when the leaves fall) I plan to replace the ribbon cable dipole with the doublet and the remote tuner on some tall trees in the backyard. |
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#7
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Hear! Hear!
I would have been off the air forever if this newsgroup had been my only source of knowledge. I would have been afraid! What I didn't know about Jx and SWR didn't make any difference -- I was on the air and really enjoying the hobby! I didn't even know how to solder then! Irv VE6BP (first licenced in '58) "Mike Coslo" wrote in message ... On 8/2/2011 7:33 PM, Tom Horne wrote: No but it does make it more dangerous to persons and things on which it might fall if it breaks. Come on, Guys! While it's a great idea to follow every official code and reccomendation, and that no one in their "right mind" would ever consider anything less than the lowest gauge copperweld wire for their antenna, the original question is answerable by "Yes, you can make a serviceable antenna out of speaker wire." Will it stay up as long as a Copperweld antenna held in place by1/4 inch thick 100 percent nylon rope? No it won't. But it will work. Surprisingly well, in fact. Let the new guys learn, and throw up antennas that work. As they have to put up a new one every so often, they will eventually learn about more long lasting antennas, as well as ones that might have a better pattern, and other effects that bear on performance. But the idea that hams are responsible for restrictive covenents (in reality, Cable television is more responsible for antenna covenants than anything else) or that the choice of speaker wire is going to electrocute the neighbors is doing a disservice to the new guys and gals. I can say this with some conviction because I was one of those noobs once, and nearly didn't even get on HF because with all the input, I gave up on putting up an antenna because nothing was good enough. I didn't have enough space, I didn't have enough height. There just wasn't any use in getting on the low bands. I needed a separate antenna for every band because ladder line was awful and traps were bad and every other option was awful except for some idealized correct antenna, coax fed, at the proper height. - 73 de Mike N3LI - |
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#8
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On 8/3/2011 4:48 PM, Irv Finkleman wrote:
Hear! Hear! I would have been off the air forever if this newsgroup had been my only source of knowledge. I would have been afraid! What I didn't know about Jx and SWR didn't make any difference -- I was on the air and really enjoying the hobby! I didn't even know how to solder then! Right. But I would like to say that it isn't at all that the information is wrong. In fact, the experts are generally 100 percent right. And that is where some of the problems are. A noob comes in, and gets 3 different answers, and becomes hopelessly confused because they would seem to contradict each other. They don't really know how to figure it out. It isn't confined to this group. Another group I'm in where I am a bit of an expert, Amateur telescope making, some times suffers from the same thing. My point is that I'm not trying to chide the experts. After all, it's not very graceful to bust peoples chops when they take the time to answer a question. I's more begging them to realize that I'm a bit of an idiot, and easily confused! - 73 de Mike N3LI - |
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#9
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On 8/2/2011 8:24 AM, John S wrote:
On 8/1/2011 7:52 PM, Jim Lux wrote: On 7/31/2011 3:26 PM, Owen Duffy wrote: John wrote in : Maybe because NFPA 70 costs $150 US? Yes, standards are expensive things and it is a frustration when researching. Anyway, NFPA makes recommendation on the wires for ham antennas specifically, and it may be binding in some places. I suspect the reason for ignoring it is that the advice is unaccepable to most hams. That said, it does seem over the top in some areas, and is hardly comprehensive in its thinking. For example, the prescription for feedlines seems to not be aware of the existence and use of coax. You refer to the "continuously enclosed metallic shield", I suspect. I guess it is these gaps that give critics the basis for arguing against the whole thing. Anyway, in respect of antenna wires, it does not 'permit' annealled copper or other low strength materials, and it 'requires' a minimum conductor diameter of #14 for up to 150' span. They may have had in mind the risk to persons and property where low strength conductor are broken in high wind and make contact with power lines. That is precisely why. (ice loads, too) NFPA (according to what you posted) requires heavier gauge wire for transmitting than for receiving. Transmitting makes the wire weigh more? An interesting observation. You'd have to go look at the history of that article in the code to find out why. It's not impossible that they were following standard commercial installation practice/recommendations back in the day, and it was "acceptable power loss" related. (the wire sizing for AC branch circuits is based on tolerating a 2% voltage drop, not overheating of the conductor) |
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