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#41
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Yacht Rf ground and radials
wrote:
Cecil Moore wrote: Didn't they notice that the water lever dropped? Not usually. They fill the hole in the water with so much money they never notice anything else. :-) Darn, when are they going to invent a spellchecker that can tell the difference between "level" and my typo, "lever"? -- 73, Cecil http://www.qsl.net/w5dxp |
#42
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Yacht Rf ground and radials
In article , Cecil Moore wrote: Didn't they notice that the water lever dropped? Not usually. They fill the hole in the water with so much money they never notice anything else. :-) Darn, when are they going to invent a spellchecker that can tell the difference between "level" and my typo, "lever"? Even a semantically-sensitive AI-type context checker would have had problems with that one. "Water lever" is an obvious reference to the float-and-valve arrangement in a toilet's water tank, and everybody (including good AI systems) know very well that boats are the best invention ever made for flushing money down a toilet. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#43
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Yacht Rf ground and radials
Reg, G4FGQ wrote:
"At radio fgrequencies the impedance of the connection to ground will be that of the connecting wire only, even before the resistance of the connecting wire to the water is taken into account." In general, Reg is correct. I`ve installed a marine radio on a yacht, engine powered not the sailing kind. It worked well as expected and the owner paid promptly. I`ve also installed radios of various types in many vessels including large ones used on the high seas and small work boats serving the near offshore. But, I never installed an antenna using radials on a boat or ship. Radials can be hazardous to eyes and body parts at sea. For VHF, a 1/2-wave coaxial antenna has the same gain as a ground plane but needs no radials. For HF, it`s easy and effective to use a loaded vertical antenna against the sea as a return path. Best regards, Richard Harrison, K5WZI |
#44
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Yacht Rf ground and radials
Roy Lewallen writes:
bob wrote: I dont have NEC4 is it too much to ask you to run the model. Radials over sea water versus a direct connection? Sure. How many, how high, and how long? The foot-long wire produces efficiency of virtually unmeasurably close to 100%. So radials can't be significantly better. What sort of efficiency are you expecting from the radials? How does a copper wire behave when submerged in salt water? Won't it corrode rapidly, so that you don't get a metal to salt water connection, but a capacitive coupling across copper oxide? Not a rhetorical question, btw. I really don't know the answer. 73 LA4RT Jon |
#45
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Yacht Rf ground and radials
Jon Kåre Hellan wrote:
Roy Lewallen writes: bob wrote: I dont have NEC4 is it too much to ask you to run the model. Radials over sea water versus a direct connection? Sure. How many, how high, and how long? The foot-long wire produces efficiency of virtually unmeasurably close to 100%. So radials can't be significantly better. What sort of efficiency are you expecting from the radials? How does a copper wire behave when submerged in salt water? Won't it corrode rapidly, so that you don't get a metal to salt water connection, but a capacitive coupling across copper oxide? Not a rhetorical question, btw. I really don't know the answer. 73 LA4RT Jon The copper alloys widely used in wires are quite resistant to corrosion. Even when immersed in pure seawater, their corrosion rate there is on the order of 0.025 mm/year. Unfortunately polluted waters can increase that rate. The metal to water interface may indeed be affected by the corrosion layer. This problem is frequently seen by electricians when installing grounding rods in the earth. However, I imagine the capacitance in this case would provide sufficient coupling at RF so that it would not be a problem. Biofouling might be of greater concern if corrosion does not occur fast enough. 73, Chuck NT3G ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#46
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Yacht Rf ground and radials
chuck wrote:
The copper alloys widely used in wires are quite resistant to corrosion. Even when immersed in pure seawater, their corrosion rate there is on the order of 0.025 mm/year. Unfortunately polluted waters can increase that rate. What then, would be polluted water? Salt water seems polluted enough. tom K0TAR |
#47
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Yacht Rf ground and radials
chuck wrote:
The copper alloys widely used in wires are quite resistant to corrosion. [...] 73, Chuck NT3G I don't know about corrosion resistance, but the copper wire used in electrical conductors is very high purity. This is needed since any contaminants reduce the conductivity. Here are a few quick references: Copper is made with different purities depending on the application. The highest grade copper is electrical grade. It is 99.99% pure and is used for electrical cables because it has the best electrical conductivity. Electrical grade scrap must never be mixed with any of the lower purity grades such as plumbing tube scrap. This contains too much phosphorus which drastically reduces the electrical conductivity. The lower grades of scrap can be used to make copper alloys or chemicals. The copper sulphate you use in your school laboratory has probably been made with scrap copper. http://www.schoolscience.co.uk/conte...opch32pg3.html Copper Facts Electrical Copper is the standard benchmark for electrical conductivity. It conducts electrical current better than any other metal except silver. Copper is routinely refined to 99.98% purity (even more pure than Ivory Soap) before it is acceptable for many electrical applications. Number 12 (AWG) copper wire is the most common size used for branch circuit wiring in buildings. The amount of copper products consumed in the U.S.A. this past year would make a size 12 wire that could encircle the Earth 2,630 times or make 140 round trips to the Moon. http://www.copper.org/education/c-fa...lectrical.html Regards, Mike Monett |
#48
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Yacht Rf ground and radials
Tom Ring wrote:
chuck wrote: The copper alloys widely used in wires are quite resistant to corrosion. Even when immersed in pure seawater, their corrosion rate there is on the order of 0.025 mm/year. Unfortunately polluted waters can increase that rate. What then, would be polluted water? Salt water seems polluted enough. tom K0TAR Copper piping and water jackets are often badly corroded when decaying plant and animal mater and sediment are dormant in the pipe. This is likely to be more troublesome in marinas and harbors than in the open ocean (Sargasso Sea excepted, maybe). "Particularly detrimental are sulfate-reducing bacteria in bottom mud and sediment and on the natural sulfates in seawater." from "The Boatowner's Guide to Corrosion" by Everett Collier. 73, Chuck NT3G ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#49
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Yacht Rf ground and radials
You are all making a song and dance about it.
Whatever the ground electrode system happens to be, the impedance to Earth cannot possibly be less than the series impedance of the connecting lead. Which can be quite high at HF. In my opinion, the most effective ground will always be a short, thick, direct connection from the radio equipment to the internal hull of a metal boat. If you like, you can connect whatever else you have in mind in parallel with it, probably at the other end of a long lead, and it won't make the slightest improvement in performance. Just use your loafs. And Happy sailing! ---- Reg, G4FGQ. |
#50
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Yacht Rf ground and radials
What then, would be polluted water?
==================================== Well, for starters, you could urinate in it. |
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