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#1
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![]() "Bill Turner" wrote in message ... ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC |
#2
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![]() ORIGINAL MESSAGE: On Sun, 01 Jan 2006 20:10:08 GMT, "west" wrote: "Bill Turner" wrote in message .. . ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OK. 1. Running a wire from your rig to ground will not do what you think it will. Any wire is a significant portion of a wavelength at HF and may be many wavelengths at VHF and UHF. On ten meters, for example, eight feet is almost exactly 1/4 wavelegth. If you recall your basic transmission line theory, whatever condition is present at one end of a 1/4 wave line has just the opposite at the other end. If you really do have a good ground connection at the grounded end of the wire, the other is an open circuit. Not very effective for grounding, is it? The effect becomes less as you lower the frequency, but never completely disappears. It is possible to tune out this effect with a suitable coil and capacitor combination, but it really isn't needed anyway. MFJ makes a "ground tuner" or whatever they call it, and I suppose it does work, but think about this: If getting a good RF ground actually improves your signal, you have a SERIOUS problem in your antenna. More on this in the next paragraph. 2. RF does no good flowing through the earth. None at all. Dirt is a poor conductor at any ham frequency and you should do your best to keep your RF out of it. I suspect the idea that "ground" helps your signal came from the very early days of radio when frequencies were very low and wavelenghts were very long... miles long in fact. At those frequencies there are two factors which might make use of ground desireable: The earth is much more conductive at very low frequencies, and miles of wire for an antenna is not easily done. Under those circumstances, working a long wire against ground might actually be a good idea. None of that applies to ham frequencies, of course. At ham frequencies, RF works best when it's up in the air, all of it. Not in the ground, not in your shack, up in the air. Keep that in mind and you can't go wrong. 73, Bill W6WRT |
#3
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![]() "Bill Turner" wrote in message ... ORIGINAL MESSAGE: On Sun, 01 Jan 2006 20:10:08 GMT, "west" wrote: "Bill Turner" wrote in message .. . ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OK. 1. Running a wire from your rig to ground will not do what you think it will. Any wire is a significant portion of a wavelength at HF and may be many wavelengths at VHF and UHF. On ten meters, for example, eight feet is almost exactly 1/4 wavelegth. If you recall your basic transmission line theory, whatever condition is present at one end of a 1/4 wave line has just the opposite at the other end. If you really do have a good ground connection at the grounded end of the wire, the other is an open circuit. Not very effective for grounding, is it? The effect becomes less as you lower the frequency, but never completely disappears. It is possible to tune out this effect with a suitable coil and capacitor combination, but it really isn't needed anyway. MFJ makes a "ground tuner" or whatever they call it, and I suppose it does work, but think about this: If getting a good RF ground actually improves your signal, you have a SERIOUS problem in your antenna. More on this in the next paragraph. 2. RF does no good flowing through the earth. None at all. Dirt is a poor conductor at any ham frequency and you should do your best to keep your RF out of it. I suspect the idea that "ground" helps your signal came from the very early days of radio when frequencies were very low and wavelenghts were very long... miles long in fact. At those frequencies there are two factors which might make use of ground desireable: The earth is much more conductive at very low frequencies, and miles of wire for an antenna is not easily done. Under those circumstances, working a long wire against ground might actually be a good idea. None of that applies to ham frequencies, of course. At ham frequencies, RF works best when it's up in the air, all of it. Not in the ground, not in your shack, up in the air. Keep that in mind and you can't go wrong. 73, Bill W6WRT That makes a lot of sense, Bill. It takes talent to take a rather technical concept and put it into an easy to understand explanation. This post is going in my Ham archive. Thanks again. Cordially, west AF4GC |
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