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Groundplane, or something else?
What characteristics would a 1/2 wave dipole have if one side was near vertical, and the other side buried along the ground? Would it act like a poorly counterpoised groundplane vertical, or something else? Any redeeming qualities? Ed |
You guessed it...It's a vertical with one radial...
Qualities? Hummmm....It's a subpar dipole... Hummmm....it's a subpar vertical too...:/ Any redeeming qualities would have to be in the eye of the beholder..MK |
You guessed it...It's a vertical with one radial... Qualities? Hummmm....It's a subpar dipole... Hummmm....it's a subpar vertical too...:/ Any redeeming qualities would have to be in the eye of the beholder..MK In what manner would this vertical be "subpar? "If one were looking for for a vertical with more radiation in one direction, would this be something to consider? Ed |
On Sun, 30 Jan 2005 06:01:26 GMT, Ed
wrote: What characteristics would a 1/2 wave dipole have if one side was near vertical, and the other side buried along the ground? Would it act like a poorly counterpoised groundplane vertical, or something else? Any redeeming qualities? Ed It would fit on your real estate. If you add three radials you would have a good ground plane. I have had in the past the Taylor Radio 4 band vertical and the Hustler 5 band vertical. I ran both of them with only a 6 foot ground rod in the ground with no radials. They worked. I doubt that they worked as well as my dipoles at 65 feet or so, but they did work. Why do you want the antenna? That may determine how good it is. If you want a 'money is no object super duper DX antenna', then it won't be worth the time of day. But if you need an antenna to fit precisely where that antenna is so you can occasionally rag chew and not spend any more money for an antenna, it will be perfect. -- Buck N4PGW |
Ed wrote:
What characteristics would a 1/2 wave dipole have if one side was near vertical, and the other side buried along the ground? Would it act like a poorly counterpoised groundplane vertical, or something else? Any redeeming qualities? When two radials are 180 degrees apart and elevated, they tend to cancel the radiation from each other. When you bury one radial, you ensure that ~half your RF energy is lost. If you bury that one radial vertically, you do indeed lose half your signal since you have put half of your dipole underground. Ground mounted verticals give up approximately half their power to ground losses. Then they give up approximately another 3 dB to a rotatable dipole. Approximately 10 ohms of the feedpoint impedance for mobile antennas is ground losses. (Please note that everything I said is approximate. :-) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Compared to a vertical with more ground radials, I believe you'd have
less radiation in other directions rather than more in the desired direction. Roy Lewallen, W7EL Ed wrote: In what manner would this vertical be "subpar? "If one were looking for for a vertical with more radiation in one direction, would this be something to consider? Ed |
It would be subpar because of excess ground losses #1. You only have
one radial, and the antenna is low to the ground. As far as radiation in one direction, I agree with Roy. It would probably be about the same in that direction as another "poorly grounded" antenna, except that in the other directions, it would be even worse. I think in the real world, you will find it to be hardly directive at all. Or at least enough to be useful anyway...To be really directive, a vertical system needs multi elements. IE: phased verticals, bobtail curtains, etc...A bobtail curtain is a mean antenna on 40m at night. Only the curtains, and the few lucky dogs running yagi's could beat my elevated ground plane to VK land late at night. A friend of mine across town ran a bobtail curtain. He could dog my GP most every night. But he's got three elements compared to my one... MK |
wrote:
It would be subpar because of excess ground losses #1. You only have one radial, and the antenna is low to the ground. As far as radiation in one direction, I agree with Roy. It would probably be about the same in that direction as another "poorly grounded" antenna, except that in the other directions, it would be even worse. EZNEC agrees. With four radials one foot above ground the gain is -0.53 dBi. With one radial one foot above ground the gain is -1.62 dBi in the direction of the one radial and - 6 dBi in the opposite direction. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
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On Sun, 30 Jan 2005 22:56:55 -0600, Cecil Moore
wrote: wrote: It would be subpar because of excess ground losses #1. You only have one radial, and the antenna is low to the ground. As far as radiation in one direction, I agree with Roy. It would probably be about the same in that direction as another "poorly grounded" antenna, except that in the other directions, it would be even worse. EZNEC agrees. With four radials one foot above ground the gain is -0.53 dBi. With one radial one foot above ground the gain is -1.62 dBi in the direction of the one radial and - 6 dBi in the opposite direction. How does it rate it with that one radial buried in the ground as in the OP rather than above the ground? -- 73 for now Buck N4PGW |
Buck wrote:
Cecil Moore wrote: EZNEC agrees. With four radials one foot above ground the gain is -0.53 dBi. With one radial one foot above ground the gain is -1.62 dBi in the direction of the one radial and - 6 dBi in the opposite direction. How does it rate it with that one radial buried in the ground as in the OP rather than above the ground? I don't have NEC-4 so I can't bury radials. Perhaps Roy will do the honors. Incidentally, the above simulation was done for a 33 ft vertical with 33 ft radials on 40m. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Buck wrote: How does it rate it with that one radial buried in the ground as in the OP rather than above the ground? Should be slightly worse, I would think. MK |
"Cecil Moore" wrote Ed wrote: What characteristics would a 1/2 wave dipole have if one side was near vertical, and the other side buried along the ground? Would it act like a poorly counterpoised groundplane vertical, or something else? Any redeeming qualities? When two radials are 180 degrees apart and elevated, they tend to cancel the radiation from each other. When you bury one radial, you ensure that ~half your RF energy is lost. If you bury that one radial vertically, you do indeed lose half your signal since you have put half of your dipole underground. Ground mounted verticals give up approximately half their power to ground losses. Then they give up approximately another 3 dB to a rotatable dipole. Approximately 10 ohms of the feedpoint impedance for mobile antennas is ground losses. (Please note that everything I said is approximate. :-) -- 73, Cecil http://www.qsl.net/w5dxp Hello Cecil, Is it appropriate to apply the above discussion to two random-wires, end-fed (coax) from a 4:1 Balun were one half of the Balun output is directly connected to ground? I would like to experiment using one or more radials (laid on the surface of ground at first, buried if that helps). for this antenna. Electrically, the antenna is about 1/8 wavelength for some frequencies, and as much as 9/5 wavelength for others. The angle of the wires is about 45 degrees elevation. One wire is about 76' and the other 42'long. I use an ATU for this antenna and it has no trouble loading anything, however only 5-15 mhz is reliable for DX. Due to the antenna's location on the property line, I could only apply radials 180 degrees (along its axis) and of course if permanent, would have their ends bonded to the station/service ground, etc. Thanks for suggestions... Jack Painter Virginia Beach, Virginia |
Jack Painter wrote:
Is it appropriate to apply the above discussion to two random-wires, end-fed (coax) from a 4:1 Balun were one half of the Balun output is directly connected to ground? I'm sorry Jack, I don't understand the question. If the two wires are equal length and the currents are flowing in opposite physical directions, the far fields will tend to cancel. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
"Cecil Moore" wrote in message ... Jack Painter wrote: Is it appropriate to apply the above discussion to two random-wires, end-fed (coax) from a 4:1 Balun were one half of the Balun output is directly connected to ground? I'm sorry Jack, I don't understand the question. If the two wires are equal length and the currents are flowing in opposite physical directions, the far fields will tend to cancel. -- 73, Cecil http://www.qsl.net/w5dxp Sorry Cecil, I'll be more clear: I have a random wire antenna, it has one coax-attachment (feedpoint) from which two different length wires start from a 4:1 Balun on a ground rod, up to a Pine tree about 60' in the air. The shorter 42' wire terminates via insulated connector and non-conductive line to the main 76' wire that continues skyward (about a 45 degree angle) until it terminates at an insulator before the support line finally connects it to the high tree limb. Some folks call this a "fan" arrangement. A Radio Works 4:1 current-type Balun has two output connectors, and both random wires start at one of those connectors. The other connector (normally intended for the other half of a dipole) is shorted to the ground rod the Balun is mounted to. This is a noise-limiting design from an old Fine Tuning "Proceedings" article. My question is, if I added a long radial (on the ground) from that ground rod, all the way under the sloping antenna wires, would there be any benefit in the transmitting pattern? How about two radials, 180 degrees from each other (one under the antenna, the other 180 degrees away from it)? I sounds kind of like creating an 1/2 underground dipole, which you and others well explained is a non-starter. But the antenna also has characteristics similar to an inverted-L, and I believe those can benefit from radials. The antenna has been easy to manually tune via an MFJ-962D, and an MFJ-994 ATU makes quick work of any thing I have loaded it with. Could radials improve this "random wire(s)" antenna, or just soak up more power? Thanks a lot, Jack |
Jack Painter wrote:
My question is, if I added a long radial (on the ground) from that ground rod, all the way under the sloping antenna wires, would there be any benefit in the transmitting pattern? How about two radials, 180 degrees from each other (one under the antenna, the other 180 degrees away from it)? If I understand it correctly, I would guess that radials would help that antenna. Sounds like you are losing half your power in the ground rod. Two radials are better than one and the more radials the better. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
"Cecil Moore" wrote Jack Painter wrote: My question is, if I added a long radial (on the ground) from that ground rod, all the way under the sloping antenna wires, would there be any benefit in the transmitting pattern? How about two radials, 180 degrees from each other (one under the antenna, the other 180 degrees away from it)? If I understand it correctly, I would guess that radials would help that antenna. Sounds like you are losing half your power in the ground rod. Two radials are better than one and the more radials the better. -- 73, Cecil http://www.qsl.net/w5dxp Thanks Cecil. It probably is a power-sink when xmit. The antenna was originally set up as a receive-only antenna, and you should hear the difference in volume when the grounded side of the Balun is off/on the ground rod. Audible increase (for DX purposes, where a couple of S-units is a lot, hi). I'll try the radials, and disconnect the shorting ground, and see if this improves things a little. I never heard anyone mention making a "vee" dipole antenna (from the ground-up), is that a NVIS? Jack |
Jack Painter wrote:
I never heard anyone mention making a "vee" dipole antenna (from the ground-up), is that a NVIS? A balanced-V would not have very much vertically polarized radiation and thus would probably be an NVIS. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
In message , Cecil Moore
writes Jack Painter wrote: I never heard anyone mention making a "vee" dipole antenna (from the ground-up), is that a NVIS? A balanced-V would not have very much vertically polarized radiation and thus would probably be an NVIS. Vee antennas (inverted or not) tend to produce quite a lot of vertically polarised radiation off the ends. Horizontal broadside, of course. Ian. -- |
On Tue, 1 Feb 2005 01:02:21 -0500, "Jack Painter"
wrote: "Cecil Moore" wrote in message ... Jack Painter wrote: Is it appropriate to apply the above discussion to two random-wires, end-fed (coax) from a 4:1 Balun were one half of the Balun output is directly connected to ground? I'm sorry Jack, I don't understand the question. If the two wires are equal length and the currents are flowing in opposite physical directions, the far fields will tend to cancel. -- 73, Cecil http://www.qsl.net/w5dxp Sorry Cecil, I'll be more clear: I have a random wire antenna, it has one coax-attachment (feedpoint) from which two different length wires start from a 4:1 Balun on a ground rod, up to a Pine tree about 60' in the air. The shorter 42' wire terminates via insulated connector and non-conductive line to the main 76' wire that continues skyward (about a 45 degree angle) until it terminates at an insulator before the support line finally connects it to the high tree limb. Some folks call this a "fan" arrangement. A Radio Works 4:1 current-type Balun has two output connectors, and both random wires start at one of those connectors. The other connector (normally intended for the other half of a dipole) is shorted to the ground rod the Balun is mounted to. This is a noise-limiting design from an old Fine Tuning "Proceedings" article. My question is, if I added a long radial (on the ground) from that ground rod, all the way under the sloping antenna wires, would there be any benefit in the transmitting pattern? How about two radials, 180 degrees from each other (one under the antenna, the other 180 degrees away from it)? I sounds kind of like creating an 1/2 underground dipole, which you and others well explained is a non-starter. But the antenna also has characteristics similar to an inverted-L, and I believe those can benefit from radials. The antenna has been easy to manually tune via an MFJ-962D, and an MFJ-994 ATU makes quick work of any thing I have loaded it with. Could radials improve this "random wire(s)" antenna, or just soak up more power? Thanks a lot, Jack Sounds an awful lot like a form of J-Pole antenna. -- 73 for now Buck N4PGW |
On Tue, 1 Feb 2005 11:41:50 -0500, "Jack Painter"
wrote: Thanks Cecil. It probably is a power-sink when xmit. The antenna was originally set up as a receive-only antenna, and you should hear the difference in volume when the grounded side of the Balun is off/on the ground rod. Audible increase (for DX purposes, where a couple of S-units is a lot, hi). I'll try the radials, and disconnect the shorting ground, and see if this improves things a little. I never heard anyone mention making a "vee" dipole antenna (from the ground-up), is that a NVIS? Jack I would think it would be NVIS. A lazy Vee ( horizontal wires) is directional going from the point through the midpoint between the two ends. If it is directional horizontal, it must be directional pointed strait up. -- 73 for now Buck N4PGW |
"Buck" wrote "Jack Painter" wrote: Thanks Cecil. It probably is a power-sink when xmit. The antenna was originally set up as a receive-only antenna, and you should hear the difference in volume when the grounded side of the Balun is off/on the ground rod. Audible increase (for DX purposes, where a couple of S-units is a lot, hi). I'll try the radials, and disconnect the shorting ground, and see if this improves things a little. I never heard anyone mention making a "vee" dipole antenna (from the ground-up), is that a NVIS? Jack I would think it would be NVIS. A lazy Vee ( horizontal wires) is directional going from the point through the midpoint between the two ends. If it is directional horizontal, it must be directional pointed strait up. -- 73 for now Buck N4PGW Adding a single radial under 45 degree random wires did not have a noticeable effect on 2182 performance under the midday sun. 100 miles was it's maximum and barely readable (both ways) from the one station I talked to. Even if I did configure it for NVIS, that would make a totally useless daytime antenna for MF, with all of it's energy being absorbed. The Canadian stations certainly do well, being loud and clear from Halifax, St Johns, Placentia, Labrador, St Anthony, all the way to the Mid-Atlantic. I guess a vertical or high elevation 1/2 wave dipole are the only solutions for daytime success there. Maybe a job for the super-Isotron, hi, hi. But seriously, I might try a much longer wire, something close to 1/2 wave, with a feedpoint-choke but no Balun. 73, Jack Painter Virginia Beach, Virginia |
Ian Jackson wrote:
Cecil Moore writes: A balanced-V would not have very much vertically polarized radiation and thus would probably be an NVIS. Vee antennas (inverted or not) tend to produce quite a lot of vertically polarised radiation off the ends. Horizontal broadside, of course. Ian. Sorry, I left out a couple of words. Should have been "A balanced-V would not have very much vertically polarized low angle radiation and thus would probably be an NVIS." -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote:
Buck wrote: Cecil Moore wrote: EZNEC agrees. With four radials one foot above ground the gain is -0.53 dBi. With one radial one foot above ground the gain is -1.62 dBi in the direction of the one radial and - 6 dBi in the opposite direction. How does it rate it with that one radial buried in the ground as in the OP rather than above the ground? I don't have NEC-4 so I can't bury radials. Perhaps Roy will do the honors. Incidentally, the above simulation was done for a 33 ft vertical with 33 ft radials on 40m. I've been extremely busy lately, but found a few minutes to run this. This is for a 33 foot vertical with 33' ground wires buried 6 inches deep. The model was run with EZNEC/4 using the NEC-4 calculating engine. All are for average ground, and the gains are at the elevation angle where gain is the maximum -- 26 degrees in all cases. With one radial, the gain in the direction of the radial is -5.94 dBi, -6.7 dBi in the opposite direction. It's interesting to see how much difference it makes to have the radial just a foot above the ground, as Cecil modeled, rather than six inches below. When the radial is above the ground, the current distribution looks pretty much the same as the vertical wire's. So it contributes significantly to the pattern. But when buried, the current decays rapidly in an exponential-looking fashion, so it doesn't contribute much to the radiation. With one radial, the gain at right angles to the radial wire is -6.49 dBi. With two radials, the gain in line with the radials is -4.33 dBi, and at right angles essentially the same, -4.58 dBi. With four radials, the gain is -2.95 dBi essentially in all directions. With 8 radials, the gain is -1.79 dBi. This is just about what you get in the favored direction with a single radial elevated one foot. According to NEC-4, anyway. These would be some interesting experiments to do with a real antenna. And, running EZNEC using MININEC-type ground gives the gain you'd get with a perfect radial system -- -0.02 dBi. Roy Lewallen, W7EL |
On Sat, 05 Feb 2005 23:32:55 -0800, Roy Lewallen
wrote: Cecil Moore wrote: Cecil Moore wrote: EZNEC agrees. With four radials one foot above ground the gain is -0.53 dBi. With one radial one foot above ground the gain is -1.62 dBi in the direction of the one radial and - 6 dBi in the opposite direction. snip This is for a 33 foot vertical with 33' ground wires buried 6 inches deep. The model was run with EZNEC/4 using the NEC-4 calculating engine. All are for average ground, and the gains are at the elevation angle where gain is the maximum -- 26 degrees in all cases. With one radial, the gain in the direction of the radial is -5.94 dBi, -6.7 dBi in the opposite direction. It's interesting to see how much difference it makes to have the radial just a foot above the ground, as Cecil modeled, rather than six inches below. When the radial is above the ground, the current distribution looks pretty much the same as the vertical wire's. So it contributes significantly to the pattern. But when buried, the current decays rapidly in an exponential-looking fashion, so it doesn't contribute much to the radiation. With one radial, the gain at right angles to the radial wire is -6.49 dBi. With two radials, the gain in line with the radials is -4.33 dBi, and at right angles essentially the same, -4.58 dBi. With four radials, the gain is -2.95 dBi essentially in all directions. With 8 radials, the gain is -1.79 dBi. This is just about what you get in the favored direction with a single radial elevated one foot. According to NEC-4, anyway. These would be some interesting experiments to do with a real antenna. And, running EZNEC using MININEC-type ground gives the gain you'd get with a perfect radial system -- -0.02 dBi. Roy Lewallen, W7EL If I read this correctly, the more above ground radials (to a point), the better. Until one gets to 8 radials, there is a significant drop in antenna loss. How do the gains/losses change when the radials are disproportionate? i.e., you have been working with essentially a 40 meter vertical with 40 meter radials. What if I were to place a 20 meter vertical (16 foot for example) on that 33 foot radial system vs placing a 20 meter vertical on the same 8 radials 16 foot long? One of the things I would like to have for a multiband vertical is the separate elements using GAP technology or just using a common feed point as seen in some of the handbooks. Thanks for all the info. I have a eznic and the ARRL version, but there is something that isn't registering with me when using it. Sometimes there are things I just can't seem to learn unless someone shows me what i am doing wrong or missing. Buck N4PGW -- 73 for now Buck N4PGW |
Buck wrote:
If I read this correctly, the more above ground radials (to a point), the better. Until one gets to 8 radials, there is a significant drop in antenna loss. Nope, you didn't. My analysis was for buried, not above ground, radials. And the loss increases, rather than drops, as the number increases. This has been well known since at least 1937. How do the gains/losses change when the radials are disproportionate? i.e., you have been working with essentially a 40 meter vertical with 40 meter radials. What if I were to place a 20 meter vertical (16 foot for example) on that 33 foot radial system vs placing a 20 meter vertical on the same 8 radials 16 foot long? There are an infinite number of such questions, each with its own answer. But a little research will show that the difference between 16 and 33 foot radials will make little difference on either 40 or 20 meters. There's been a lot posted on this newsgroup in the past about ground radial systems -- you'll find the answers to many of your questions by using groups.google.com for a search. One of the things I would like to have for a multiband vertical is the separate elements using GAP technology or just using a common feed point as seen in some of the handbooks. You really want to use a lossy piece of coax to load your antenna as the GAP does instead of a more efficient method? Why? Fanned wires with a common feed point will be more efficient. If you bury the radials, you need only one ground system -- 8 or so radials will get you within a couple of dB of a perfect system. Thanks for all the info. I have a eznic and the ARRL version, but there is something that isn't registering with me when using it. Sometimes there are things I just can't seem to learn unless someone shows me what i am doing wrong or missing. I've heard many good comments about the ARRL on-line course in antenna modeling. You might consider it. Roy Lewallen, W7EL |
On Sun, 06 Feb 2005 15:29:04 -0800, Roy Lewallen
wrote: Nope, you didn't. My analysis was for buried, not above ground, radials. And the loss increases, rather than drops, as the number increases. This has been well known since at least 1937. Thanks for the correction. As a Novice I learned that underground radials were better than above ground radials. I couldn't be sure which you were using so I re-iterated it to be sure. How do the gains/losses change when the radials are disproportionate? i.e., you have been working with essentially a 40 meter vertical with 40 meter radials. What if I were to place a 20 meter vertical (16 foot for example) on that 33 foot radial system vs placing a 20 meter vertical on the same 8 radials 16 foot long? you'll find the answers to many of your questions by using groups.google.com for a search. Thanks, I'll do that. You really want to use a lossy piece of coax to load your antenna as the GAP does instead of a more efficient method? Why? Fanned wires with a common feed point will be more efficient. If you bury the radials, you need only one ground system -- 8 or so radials will get you within a couple of dB of a perfect system. I didn't clarify myself, but the gap technology (I should have used lower case) isn't necessarily the same as the GAP brand. I couldn't find the book I have it in, but it is where a wire resonant on a particular frequency brought close to another antenna will match the system and radiate efficiently (I don't know how efficiently.) (this is an oversimplification of what I am describing.) I've heard many good comments about the ARRL on-line course in antenna modeling. You might consider it. I'll look into it. I understand a lot of what I am doing, but something isn't working. I think it is one of those things that someone needs to walk me through one time looking over my shoulder and I'll get through it. Maybe it will just come to me one day. Sometimes these things happen. Thanks again. Buck -- 73 for now Buck N4PGW |
Buck wrote:
. . . I didn't clarify myself, but the gap technology (I should have used lower case) isn't necessarily the same as the GAP brand. I couldn't find the book I have it in, but it is where a wire resonant on a particular frequency brought close to another antenna will match the system and radiate efficiently (I don't know how efficiently.) (this is an oversimplification of what I am describing.) . . . That sounds like the method patented in 1996 by Gary Breed, K9AY (U.S. patent #5,489,914). He allowed the patent to expire rather than renewing it, so it's now in the public domain. See http://patft.uspto.gov/netacgi/nph-P...y+AND+IN/breed (You'll probably have to paste that back together. Or just go to http://www.uspto.gov and look it up by patent number.) Roy Lewallen, W7EL |
Buck wrote: On Sun, 06 Feb 2005 15:29:04 -0800, Roy Lewallen wrote: Nope, you didn't. My analysis was for buried, not above ground, radials. And the loss increases, rather than drops, as the number increases. This has been well known since at least 1937. This has me confused...I must be missing something...I checked the previous posts, but still doesn't make sense to me...Seems the ground losses would decrease as the number of radials increase....Thats what your model showed. I thought anyway.... Thanks for the correction. As a Novice I learned that underground radials were better than above ground radials. I couldn't be sure which you were using so I re-iterated it to be sure. For a given radial, above ground is better than in ground. But it has to be resonant. In that case, you are running a very low ground plane. If it's just one radial, it should radiate as much as the vertical element. In that case, it's more of a perverted dipole, than a ground plane. A true ground plane really needs at least two radials to get a fairly unlopsided omni pattern. Three radials are better. If you use 120 radials on medium ground as a benchmark, any height above ground will reduce the number of radials required to equal the same degree of loss. But once the radials are elevated, they must be tuned. Radials on or in the ground do not need to be resonant. If you ran a vertical, and can only use a very few radials, having them tuned and a bit off the ground is better than the same in the ground. Of course, the YL will probably want to strangle you with one, the first time she trips over one...But some run them around the lower frames of houses, wood fences, etc... One thing....It's not a magic wand to suddenly make low 4 radials a dx buster...At 1/8 wave up, it takes appx 60 radials to equal 120 on the ground. On 40m, thats 16 ft or so... At 2 ft off the ground, you still probably need maybe 90? radials to equal the 120 on the ground. So you have to consider that, when you run 4 radials at 2 ft, and don't brown the food in every direction. It is a bit better than 4 in the ground though, and Roy's model pretty much agreed...I think anyway...:/ MK |
Roy, it is a mistake to consider one element of a radiating system as being distinct from another. Reflectors and directors do not operate independently of the embedded 1/2-wave dipole. And, for example, the universally-made error of treating radiation from the feedline as being independent of that from the antenna is a serious matter. Aggravated by ignoring the choke location if there is one. Similar (greatly prolonged) educational mistakes lead to serious misunderstanding the purpose of the so-called SWR meter - the very last of the meters remaining on the front panels of our commercial black-box transmitters. They will soon go. But what does it matter. It's only a hobby. I still get my pleasures from it. And no doubt so do you. ---- Reg, G4FGQ |
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Buck wrote:
Today I see a lot of antennas preferring above ground radials. Maybe decoupling the radials from ground lowers ground losses? :-) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Mon, 07 Feb 2005 08:40:51 -0600, Cecil Moore
wrote: Buck wrote: Today I see a lot of antennas preferring above ground radials. Maybe decoupling the radials from ground lowers ground losses? :-) There have been a number of changes in technology theory in the last 30 or so years. When I was a Novice, the vertical antenna manufacturers provided information about how to use above-ground radials, but that was typically for a raised antenna such as roof mounting it. IIRC, the above ground Hustler 4BTV and the Taylor antennas both had to be lengthened a little to be resonant in the same place as the ground mount and radials had to be tuned. Reports at that time were that antenna efficiency was best when the antenna was ground mounted and had 8-16 radials buried. However, while not optimum, the minimum ground was to be an 8-foot ground rod at the base of the antenna. Baluns seemed to be a new technology, I don't recall the term "ferrite beads", and RF in the shack wasn't a big issue. One common practice was having a ground rod as close to your rig as possible and making sure the rig, PS, antenna and everything electrical near the rig was grounded to the ground rod. Today the electrical code for homes forbids that due to ground-loops. Some of these changes take some getting used to. It's a strange feeling to realize that what you knew for so long is no longer true. -- 73 for now Buck N4PGW |
Buck wrote:
Some of these changes take some getting used to. It's a strange feeling to realize that what you knew for so long is no longer true. Think about what will be accepted as being true after someone figures out how to demodulate entangled particle beams. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
I don't know what I was thinking -- I obviously wasn't. Of course you're
right. The loss decreases as the number of radials increases. I apolgize for the mistake. Roy Lewallen, W7EL Buck wrote: On 6 Feb 2005 22:38:33 -0800, wrote: And the loss increases, rather than drops, as the number increases. This has been well known since at least 1937. I didn't catch this either. I misunderstood it to be that the number of radials decrease loss. However, I do well remember that the preferred radial of the day when I was first licensed was below ground radials. Today I see a lot of antennas preferring above ground radials. This has me confused...I must be missing something...I checked the previous posts, but still doesn't make sense to me...Seems the ground losses would decrease as the number of radials increase....Thats what your model showed. |
On Mon, 07 Feb 2005 13:17:19 -0800, Roy Lewallen
wrote: I don't know what I was thinking -- I obviously wasn't. Of course you're right. The loss decreases as the number of radials increases. I apolgize for the mistake. Roy Lewallen, W7EL I chalk it up to dislexic fingers, just a type of typo! :) Strangely enough, I didn't read it that way till someone else reported it. -- 73 for now Buck N4PGW |
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