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Questions on Inverted L antenna
K9RZZ,
.. AHaaaaa :o) We have a difference of 'opinion' and a matter of perspectives ;-) .. I would agree with you that it could be called a "Bent" Random Wire Antenna: If the Lay of the Wire Antenna Element was in the Horizontal Plane [Flat]. - Across-and-Out View - - Top-Down Perspective - - - Only Horizontal Polarized .. However, in this instance the Lay of the Wire Antenna Element is both in the Horizontal Plane and the Vertical Plane. - Bottom-Up View - - Side Perspective - - - Both Horizontal and Vertical Polarized .. Then Again - Going back to the 'original' 45 Foot Horizontal Wire Antenna with a 22 Foot Vertical Ground Wire; that is fed with a Matching Transformer. It could be 'viewed' as an Off-Center-Fed Dipole with One Side Terminated. .. NOW - If the 'original' 45 Foot Horizontal Wire Antenna with a 22 Foot Vertical Ground Wire is Modified with the addition of a Vertical Down-Leg at the End of the Horizontal Wire; and still is Fed with a Matching Transformer at the Top Near Corner. It could be 'view' as directive array of Two Vertical Elements; on the Far-End a Driven Vertical Element and on the Near-End a Vertical Reflector Element. .. for any piece of wire being used as an antenna . . . - there are no rights or wrongs - - its all a matter of perspective - - - what works - works ! |
JP,
When All Is Said and Done {Written}. .. For the casual Shortwave Radio Listener; the Inverted "L" Antenna is easy to visualize and conceive of building. .. READ - The 'simple' Answer (in most cases) is the Low Noise Inverted "L" Antenna http://groups.yahoo.com/group/Shortw...a/message/1785 .. When properly laid-out, arranged and constructed; the Inverted "L" Antenna provides a relatively 'low noise' "Omni-Directional" Shortwave Listener's (SWL) Antenna. .. READ - The Inverted "L" Antenna - It's 'basic' Lay-Out and Structure {Why It Works} http://groups.yahoo.com/group/Shortw...a/message/1969 .. For the 'non-technical' Shortwave Listener the Inverted "L" Antenna meets the "KISAP" Test and that is good. KISAP = Keep-It-Simple And Practical [.] TIP - For those who do not wish to go through the process of building their own Inverted "L" Antenna; they can buy a pre-build Random {LongWire} Wire Antenna and configure it as an Inverted "L" Antenna - Two come to mind: READ - Par EF-SWL End-Fed Shortwave Antenna configured as an Inverted "L" Antenna http://groups.yahoo.com/group/Shortw...a/message/1562 http://groups.yahoo.com/group/Shortw...a/message/1711 http://groups.yahoo.com/group/Shortw...a/message/1717 READ - High-Z Shortwave Longwire Antenna with Matching Transformer (MLB) and SO-239 Connector http://groups.yahoo.com/group/Shortw...a/message/1659 http://groups.yahoo.com/group/Shortw...a/message/1709 .. I applaud your level of technical expertise and the mastery of the subject of Antennas. But for many casual Shortwave Listeners; it is a burden of knowledge that they do not wish to acquire; just to simply Listen and Enjoy their Radios a little better. READ - Inverted "L' Antenna Reading List http://groups.yahoo.com/group/Shortw...na/message/374 .. When All Is Said and Done {Written} .. . . What Works - WORKS ! .. .. iane ~ RHF .. All are WELCOME and "Invited to Join" the Shortwave Listener (SWL) Antenna eGroup on YAHOO ! http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ .. Some Say: On A Clear Day You Can See Forever. http://groups.yahoo.com/group/Shortw...na/message/502 .. I BELIEVE: On A Clear Night . . . You Can Hear Forever and Beyond, The BEYOND ! With a Shortwave Listener SWL Antenna of your own making. "If You Build It {SWL Antenna} You Will Hear Them !" |
In article d4yId.20312$B95.14800@lakeread02,
"Jack Painter" wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I agree with all that you wrote except for that last sentence. Every location is a different situation and so generalizations can be made about antenna type, radials or ground performance but there are no absolutes here. What is better in one place will not necessarily be better in another. Likely yes, but not necessarily. Some locations may be far better off with a counterpoise of some type rather than depending on RF ground return through the radio and mains supply, which is all that is left if that one ground rod the BALUN is connected to is not up to the job. As one example if you have good ground conductivity then that one rod might be all you need but if ground conductivity is poor then a radial or radials will make an improvement. You can always lay wires on the ground and see if they help. If they do then you can go through the trouble to make them perminent. Any type of single element antenna (unbalanced) requires a good RF ground to be effective. The RF ground is the other half of the antenna. -- Telamon Ventura, California |
"Telamon" wrote "Jack Painter" wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I agree with all that you wrote except for that last sentence. Every location is a different situation and so generalizations can be made about antenna type, radials or ground performance but there are no absolutes here. What is better in one place will not necessarily be better in another. Likely yes, but not necessarily. Some locations may be far better off with a counterpoise of some type rather than depending on RF ground return through the radio and mains supply, which is all that is left if that one ground rod the BALUN is connected to is not up to the job. As one example if you have good ground conductivity then that one rod might be all you need but if ground conductivity is poor then a radial or radials will make an improvement. You can always lay wires on the ground and see if they help. If they do then you can go through the trouble to make them perminent. Any type of single element antenna (unbalanced) requires a good RF ground to be effective. The RF ground is the other half of the antenna. I agree with that. While only some "incomplete" (unbalanced wire) antennas can radiate without a good RF ground, all antennas can receive with no RF ground at all. But some receivers can benefit from better ground than the AC-grounded case of the radio provides. Noise limiting is one reason we do try to improve both the DC and RF ground capabilities of the coax-shield to improve this possibility, agreed. Jack Painter Virginia Beach, Virginia |
Jack Painter wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I think you've missed the point. A so called 'low noise' inverted-L is intended to reduce noise on the feed line to the receiver which comes from domestic sources like appliances in the home. This is not the same as the noise being received by the antenna wire itself. When the feed line is part of the vertical section of the antenna, like the typical inverted-L or random wire, it can pick up noise from the domestic environment. The solution is to use a coax feed line which connects to a balun near the ground. The vertical section of the antenna comes down to the balun. This allows for a short RF ground from the coax shield to earth which decouples the noise on the shield. |
"starman" wrote Jack Painter wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I think you've missed the point. A so called 'low noise' inverted-L is intended to reduce noise on the feed line to the receiver which comes from domestic sources like appliances in the home. This is not the same as the noise being received by the antenna wire itself. When the feed line is part of the vertical section of the antenna, like the typical inverted-L or random wire, it can pick up noise from the domestic environment. The solution is to use a coax feed line which connects to a balun near the ground. The vertical section of the antenna comes down to the balun. This allows for a short RF ground from the coax shield to earth which decouples the noise on the shield. Well I didn't mean to miss the point, and I'm afraid you're far off base in suggesting that an inverted-L radiates part of the feedline or that feedline (coax-shield) noise has anything to do with an antenna configuration. The use of coax minimizes feedline noise, and shield-grounding the coax further reduces noise from either being brought into the shack or carried to the antenna from the shack. In an inverted-L, either a Balun or a choke is always used to prevent inadvertent feedline radiation. The vertical portion of the end-fed inverted-L is where the feedline ends and the antenna begins. The real noise-limiting design of any beverage-style or inverted-L wire antenna is to ground one half of the Balun output. This is whether the coax shield is grounded earlier or not. That does affect signals picked up on the antenna wire itself, although experts are not agreed as to whether there is a measurable improvement in signal to noise ratio as a result of this. As Telemon mentioned, having a counterpoise or good RF ground could make a difference there. In my particular case, there is a marked improvement in signal strength and possibly some reduction in noise when the connection from ground rod to Balun is made. I also transmit through this antenna with pretty good results. The original concept of grounding one-half of a current-type wire-fed Balun for noise limiting came from an 1980's issue of Fine Tuning's PROCEEDINGS. I was borrowing the issue from a friend and cannot remember the original author of this but I don't believe it was the venerable John Doty to which it is lately accredited. Jack Painter Virginia Beach, Virginia |
Jack Painter wrote:
"starman" wrote Jack Painter wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I think you've missed the point. A so called 'low noise' inverted-L is intended to reduce noise on the feed line to the receiver which comes from domestic sources like appliances in the home. This is not the same as the noise being received by the antenna wire itself. When the feed line is part of the vertical section of the antenna, like the typical inverted-L or random wire, it can pick up noise from the domestic environment. The solution is to use a coax feed line which connects to a balun near the ground. The vertical section of the antenna comes down to the balun. This allows for a short RF ground from the coax shield to earth which decouples the noise on the shield. Well I didn't mean to miss the point, and I'm afraid you're far off base in suggesting that an inverted-L radiates part of the feedline or that feedline (coax-shield) noise has anything to do with an antenna configuration. The use of coax minimizes feedline noise, and shield-grounding the coax further reduces noise from either being brought into the shack or carried to the antenna from the shack. In an inverted-L, either a Balun or a choke is always used to prevent inadvertent feedline radiation. The vertical portion of the end-fed inverted-L is where the feedline ends and the antenna begins. The real noise-limiting design of any beverage-style or inverted-L wire antenna is to ground one half of the Balun output. This is whether the coax shield is grounded earlier or not. That does affect signals picked up on the antenna wire itself, although experts are not agreed as to whether there is a measurable improvement in signal to noise ratio as a result of this. As Telemon mentioned, having a counterpoise or good RF ground could make a difference there. In my particular case, there is a marked improvement in signal strength and possibly some reduction in noise when the connection from ground rod to Balun is made. I also transmit through this antenna with pretty good results. The original concept of grounding one-half of a current-type wire-fed Balun for noise limiting came from an 1980's issue of Fine Tuning's PROCEEDINGS. I was borrowing the issue from a friend and cannot remember the original author of this but I don't believe it was the venerable John Doty to which it is lately accredited. If the coax shield of an inverted-L does not have a good RF ground, which requires a short ground wire to earth, the domestic noise on the shield can couple to the center conductor of the coax where it connects to the antenna. The noise will then become part of the antenna signal to the radio. That's the point I think you missed. |
"starman" wrote Jack Painter wrote: "starman" wrote Jack Painter wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I think you've missed the point. A so called 'low noise' inverted-L is intended to reduce noise on the feed line to the receiver which comes from domestic sources like appliances in the home. This is not the same as the noise being received by the antenna wire itself. When the feed line is part of the vertical section of the antenna, like the typical inverted-L or random wire, it can pick up noise from the domestic environment. The solution is to use a coax feed line which connects to a balun near the ground. The vertical section of the antenna comes down to the balun. This allows for a short RF ground from the coax shield to earth which decouples the noise on the shield. Well I didn't mean to miss the point, and I'm afraid you're far off base in suggesting that an inverted-L radiates part of the feedline or that feedline (coax-shield) noise has anything to do with an antenna configuration. The use of coax minimizes feedline noise, and shield-grounding the coax further reduces noise from either being brought into the shack or carried to the antenna from the shack. In an inverted-L, either a Balun or a choke is always used to prevent inadvertent feedline radiation. The vertical portion of the end-fed inverted-L is where the feedline ends and the antenna begins. The real noise-limiting design of any beverage-style or inverted-L wire antenna is to ground one half of the Balun output. This is whether the coax shield is grounded earlier or not. That does affect signals picked up on the antenna wire itself, although experts are not agreed as to whether there is a measurable improvement in signal to noise ratio as a result of this. As Telemon mentioned, having a counterpoise or good RF ground could make a difference there. In my particular case, there is a marked improvement in signal strength and possibly some reduction in noise when the connection from ground rod to Balun is made. I also transmit through this antenna with pretty good results. The original concept of grounding one-half of a current-type wire-fed Balun for noise limiting came from an 1980's issue of Fine Tuning's PROCEEDINGS. I was borrowing the issue from a friend and cannot remember the original author of this but I don't believe it was the venerable John Doty to which it is lately accredited. If the coax shield of an inverted-L does not have a good RF ground, which requires a short ground wire to earth, the domestic noise on the shield can couple to the center conductor of the coax where it connects to the antenna. The noise will then become part of the antenna signal to the radio. That's the point I think you missed. OK I didn't restate the obvious, agreed. The best place to terminate the antenna and mount the Balun is *at* the ground rod, which means the connection is about 4 inches long. Ty-wrap the Balun to the protruding ground rod. After applying coax-seal to the wire-wrapped and then soldered connections, cut the bottom and slit one side of a plastic beverage bottle to just fit over the Balun and tape the bottle shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes part of the background, and weather-proofed for years of service. Some designs advise terminating the vertical drop of the inverted-L about 6 feet above ground. That's more important for a center fed or off-center fed (dipole type) antenna than the end-fed wires. Users should have no problems terminating the inverted-L at ground level, and sink a good ground rod (with buried radials if you desire) at that same point. Jack Painter Virginia Beach, Virginia |
Jack Painter wrote:
"starman" wrote Jack Painter wrote: "starman" wrote Jack Painter wrote: "starman" wrote A low noise inverted-L will have the vertical downlead at the far end of the horizontal section with the balun located at the lower end of the single wire downlead, near the ground. Then you can run coax back to the house from the balun. The near end of the horizontal section shouldn't be too close to the house where it might pick up noise. The 'low noise inverted-L' (paragraph above) can make a big difference in lowering the noise that the antenna picks up from local sources. There is not one ounce of truth to an "Inverted-L" being ANY quieter than a 45 degree random wire, and especially a horizontal-dipole, which is generally quieter than any antenna with a vertical component. Most interference is vertically polarized, and the verticals, random-wires, slopers, or inverted-L antenna designs all pick up more vertically polarized "noise" than a horizontally polarized antenna. Adding a vertical or even a 45 degree sloped component to an antenna DOES make it less directional than a horizontal, and that is all it does. Any noise-limiting realized from these designs comes strictly from the grounded-Balun and not the design, configuration or dimensions of the antenna. Shield-grounding (for static and lightning protection) at the feedpoint will achieve 99% of the noise-limiting benefit that a grounded Balun does. The missing 1% is an equal loss of signal and noise through the Balun. All RF noise (but not all energy has RF components) is coupled right across the Balun windings, their function of electrically decoupling is true of some DC energy, but not RF energy, which is rather efficiently coupled across the Balun by design. The same application of a grounded-Balun works equally well on both the random (straight) wire antennas and inverted-L antenna btw. Both the random wire and inverted-L benefit from (require in most cases) a counterpoise ground or radials to provide effective transmitting. Neither a counterpoise nor radials affect reception from the either the random wire or inverted-L, however. I think you've missed the point. A so called 'low noise' inverted-L is intended to reduce noise on the feed line to the receiver which comes from domestic sources like appliances in the home. This is not the same as the noise being received by the antenna wire itself. When the feed line is part of the vertical section of the antenna, like the typical inverted-L or random wire, it can pick up noise from the domestic environment. The solution is to use a coax feed line which connects to a balun near the ground. The vertical section of the antenna comes down to the balun. This allows for a short RF ground from the coax shield to earth which decouples the noise on the shield. Well I didn't mean to miss the point, and I'm afraid you're far off base in suggesting that an inverted-L radiates part of the feedline or that feedline (coax-shield) noise has anything to do with an antenna configuration. The use of coax minimizes feedline noise, and shield-grounding the coax further reduces noise from either being brought into the shack or carried to the antenna from the shack. In an inverted-L, either a Balun or a choke is always used to prevent inadvertent feedline radiation. The vertical portion of the end-fed inverted-L is where the feedline ends and the antenna begins. The real noise-limiting design of any beverage-style or inverted-L wire antenna is to ground one half of the Balun output. This is whether the coax shield is grounded earlier or not. That does affect signals picked up on the antenna wire itself, although experts are not agreed as to whether there is a measurable improvement in signal to noise ratio as a result of this. As Telemon mentioned, having a counterpoise or good RF ground could make a difference there. In my particular case, there is a marked improvement in signal strength and possibly some reduction in noise when the connection from ground rod to Balun is made. I also transmit through this antenna with pretty good results. The original concept of grounding one-half of a current-type wire-fed Balun for noise limiting came from an 1980's issue of Fine Tuning's PROCEEDINGS. I was borrowing the issue from a friend and cannot remember the original author of this but I don't believe it was the venerable John Doty to which it is lately accredited. If the coax shield of an inverted-L does not have a good RF ground, which requires a short ground wire to earth, the domestic noise on the shield can couple to the center conductor of the coax where it connects to the antenna. The noise will then become part of the antenna signal to the radio. That's the point I think you missed. OK I didn't restate the obvious, agreed. The best place to terminate the antenna and mount the Balun is *at* the ground rod, which means the connection is about 4 inches long. Ty-wrap the Balun to the protruding ground rod. After applying coax-seal to the wire-wrapped and then soldered connections, cut the bottom and slit one side of a plastic beverage bottle to just fit over the Balun and tape the bottle shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes part of the background, and weather-proofed for years of service. Some designs advise terminating the vertical drop of the inverted-L about 6 feet above ground. That's more important for a center fed or off-center fed (dipole type) antenna than the end-fed wires. Users should have no problems terminating the inverted-L at ground level, and sink a good ground rod (with buried radials if you desire) at that same point. I mounted my balun in a plastic electrical junction box with a cover gasket, the kind used with plastic conduit. The ground wire to the rod is about 2-feet long. |
JP,
If IIRC the one Radial that helps the most, is the one that lays directly under the Horizontal Out-Arm of the Inverted "L" Antenna. This is why I suggest that 'if' possible to Flip Starting Point (Back-to-Front) with the Vertical Up-Leg of the Inverted "L" Antenna and have the Coax Cable Feed-in-Line lay directly under the Horizontal Arm of the Inverted "L" Antenna. READ - Flipping the Inverted "L" Antenna 'Back-to-Front' = Better Performance http://groups.yahoo.com/group/Shortw...a/message/2013 http://groups-beta.google.com/group/...79890656d94af1 Maybe some one could use some software amd 'model' a Shortwave Listener's (SWLs) Inverted "L" Antenna with a single Ground Radial directly under the Horizontal Out-Arm. # 1 The 'small' SWL (V1:H2) Inverted "L" Antenna using a 15 Foot Vertical Up-Leg and 30 Foot Horizontal Out-Arm Plus 30 Foot Ground Radial directly under the Horizontal Out-Arm section of the Antenna. .. # 2 The 'medium' SWL (V1:H2.5) Inverted "L" Antenna using a 20 Foot Vertical Up-Leg and 50 Foot Horizontal Out-Arm Plus 50 Foot Ground Radial directly under the Horizontal Out-Arm section of the Antenna. # 3 The 'large' SWL (V1:H3) Inverted "L" Antenna using a 25 Foot Vertical Up-Leg and 75 Foot Horizontal Out-Arm Plus 75 Foot Ground Radial directly under the Horizontal Out-Arm section of the Antenna. Test Results should be provided for these Shortwave Bands : @ 60M Band ~ 5 MHz @ 49M Band ~ 6 MHz @ 31M Band ~ 9.7 MHz @ 25M Band ~ 11.8 MHz @ 22M Band ~ 13.7 MHz @ 19M Band ~ 15.5 MHz iane ~ RHF |
Jack Painter wrote:
"starman" wrote Jack Painter wrote: The best place to terminate the antenna and mount the Balun is *at* the ground rod, which means the connection is about 4 inches long. Ty-wrap the Balun to the protruding ground rod. After applying coax-seal to the wire-wrapped and then soldered connections, cut the bottom and slit one side of a plastic beverage bottle to just fit over the Balun and tape the bottle shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes part of the background, and weather-proofed for years of service. Some designs advise terminating the vertical drop of the inverted-L about 6 feet above ground. That's more important for a center fed or off-center fed (dipole type) antenna than the end-fed wires. Users should have no problems terminating the inverted-L at ground level, and sink a good ground rod (with buried radials if you desire) at that same point. I mounted my balun in a plastic electrical junction box with a cover gasket, the kind used with plastic conduit. The ground wire to the rod is about 2-feet long. Something I intend to experiment with, is running two radials from the Balun/ground/feedpoint; one under the entire length of the antenna and the other 180 degrees away from the feedpoint. Since this antenna was deliberately located as far from the house as possible (on the property line), I could not run radials in a 360 degree fashion. But I think if radials will help at all, two of them (at 0 and 180 degrees) would show results. Ever try this? The antenna is for 2182 thru 16000 khz marine. Jack I've never tried ground radials but it's worth a try. Would you still run a short ground wire too? ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
"starman" wrote Jack Painter wrote: "starman" wrote Jack Painter wrote: The best place to terminate the antenna and mount the Balun is *at* the ground rod, which means the connection is about 4 inches long. Ty-wrap the Balun to the protruding ground rod. After applying coax-seal to the wire-wrapped and then soldered connections, cut the bottom and slit one side of a plastic beverage bottle to just fit over the Balun and tape the bottle shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes part of the background, and weather-proofed for years of service. Some designs advise terminating the vertical drop of the inverted-L about 6 feet above ground. That's more important for a center fed or off-center fed (dipole type) antenna than the end-fed wires. Users should have no problems terminating the inverted-L at ground level, and sink a good ground rod (with buried radials if you desire) at that same point. I mounted my balun in a plastic electrical junction box with a cover gasket, the kind used with plastic conduit. The ground wire to the rod is about 2-feet long. Something I intend to experiment with, is running two radials from the Balun/ground/feedpoint; one under the entire length of the antenna and the other 180 degrees away from the feedpoint. Since this antenna was deliberately located as far from the house as possible (on the property line), I could not run radials in a 360 degree fashion. But I think if radials will help at all, two of them (at 0 and 180 degrees) would show results. Ever try this? The antenna is for 2182 thru 16000 khz marine. Jack I've never tried ground radials but it's worth a try. Would you still run a short ground wire too? Per above, my 4:1 Balun/coax-feedpoint is already attached/connected directly to a ground rod, not just near one. The radials will both be part of common ground already, their tie-point at the same ground rod that the feedpoint and Balun are attached to. Radials are normally shallow-buried, both for protection and to minimize pickup of yet more noise. It's a lot of work to bury long radials, so I will first just lay them out along the surface, then experiment with various coastal stations to determine if there is any gain from the radials. Due to the lightning protection design at my station, any new ground radials also have to be bonded to the station ground and AC service entry ground, the entire system is common-bonded. Because it's winter time and small likelihood of lightning (we had a nearby strike during a snowstorm 2 weeks ago!) I will wait to add the bonding conductors until after the antenna is tested for any possible xmit/receive improvements. Those bonding connectors will have to run 90 degrees from the end of each of the two new radials, and they may also alter the radiation pattern of the antenna. I'll let you know how that works out. Jack |
In article , starman
wrote: Jack Painter wrote: "starman" wrote Jack Painter wrote: The best place to terminate the antenna and mount the Balun is *at* the ground rod, which means the connection is about 4 inches long. Ty-wrap the Balun to the protruding ground rod. After applying coax-seal to the wire-wrapped and then soldered connections, cut the bottom and slit one side of a plastic beverage bottle to just fit over the Balun and tape the bottle shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes part of the background, and weather-proofed for years of service. Some designs advise terminating the vertical drop of the inverted-L about 6 feet above ground. That's more important for a center fed or off-center fed (dipole type) antenna than the end-fed wires. Users should have no problems terminating the inverted-L at ground level, and sink a good ground rod (with buried radials if you desire) at that same point. I mounted my balun in a plastic electrical junction box with a cover gasket, the kind used with plastic conduit. The ground wire to the rod is about 2-feet long. Something I intend to experiment with, is running two radials from the Balun/ground/feedpoint; one under the entire length of the antenna and the other 180 degrees away from the feedpoint. Since this antenna was deliberately located as far from the house as possible (on the property line), I could not run radials in a 360 degree fashion. But I think if radials will help at all, two of them (at 0 and 180 degrees) would show results. Ever try this? The antenna is for 2182 thru 16000 khz marine. Jack I've never tried ground radials but it's worth a try. Would you still run a short ground wire too? If a ground wire is not short it will not behave as if it is connected to ground period. The problem is that a wire has inductance. The value of inductance is based on the diameter of the wire or cross sectional area for other shapes over its length. The smaller the cross sectional area is or the longer the wire the is the higher the inductance of that wire. The inductance of the wire will become a greater problem at higher frequencies and less of a problem the lower in frequency you want to operate on because the reactance of the wire always increases with frequency. Since you want the wire to behave as a ground connection you have to calculate its self inductance and then its inductive reactance at the highest frequency you want it to behave as a ground connection. If you don't want to calculate it then make it as short as practical. If the connection turns out to be more than a few inches in length then use three inch minimum width copper tape instead of wire. -- Telamon Ventura, California |
Telamon wrote:
In article , starman wrote: I've never tried ground radials but it's worth a try. Would you still run a short ground wire too? If a ground wire is not short it will not behave as if it is connected to ground period. The problem is that a wire has inductance. The value of inductance is based on the diameter of the wire or cross sectional area for other shapes over its length. The smaller the cross sectional area is or the longer the wire the is the higher the inductance of that wire. The inductance of the wire will become a greater problem at higher frequencies and less of a problem the lower in frequency you want to operate on because the reactance of the wire always increases with frequency. Since you want the wire to behave as a ground connection you have to calculate its self inductance and then its inductive reactance at the highest frequency you want it to behave as a ground connection. If you don't want to calculate it then make it as short as practical. If the connection turns out to be more than a few inches in length then use three inch minimum width copper tape instead of wire. Given all the talk about grounding systems on this group in the past, I think most of us here know that a good RF ground wire must be short to avoid introducing too much inductance into the grounding system. I asked the question because I wanted to know more about the relationship between a good (short) RF ground wire and a ground radial system. Does one work better than the other or should both be used together? Where's John Doty when we need him? :-) ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
jimg wrote:
it's always important to keep the ground wire length well below 1/4 wavelength of the max freq your interested in. Assuming it's short enough to prevent distributed effects, the self inductance of a straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about 1Kohm...thats a fair amount of impedance and is why you pick up all that noise..... so what's the ground radial system do? in short, it provides the counter-poise to the wire strung in the sky. the antenna-ground system create the differential signal which is applied to your receiver's rf amp...the better the ground poise, the more 'sensitive' your antenna...is this some kind of linear relationship? like double the ground system and double the antenna sensitivity...nope , not that simple and there's not enuf room here to make all the variables clear...but the better the grounding system, the better your antenna will "work"...some ppl have a good enough conduction under the soil that a simple 10' ground rod intersects this "layer" and the dx cpmes rolling in...other ppl have rods sunk in the earth and buried in wild patterns all over the yard to get the same effect..... so the simple answer(s) is: your ground wire length influences noise (what we call common-field) pick-up so shorter is better; the ground radial system improves the signal strength at the receiver input...and i hate simple answers to a very complicated system... Telamon wrote: In article , starman wrote: I've never tried ground radials but it's worth a try. Would you still run a short ground wire too? If a ground wire is not short it will not behave as if it is connected to ground period. The problem is that a wire has inductance. The value of inductance is based on the diameter of the wire or cross sectional area for other shapes over its length. The smaller the cross sectional area is or the longer the wire the is the higher the inductance of that wire. The inductance of the wire will become a greater problem at higher frequencies and less of a problem the lower in frequency you want to operate on because the reactance of the wire always increases with frequency. Since you want the wire to behave as a ground connection you have to calculate its self inductance and then its inductive reactance at the highest frequency you want it to behave as a ground connection. If you don't want to calculate it then make it as short as practical. If the connection turns out to be more than a few inches in length then use three inch minimum width copper tape instead of wire. Given all the talk about grounding systems on this group in the past, I think most of us here know that a good RF ground wire must be short to avoid introducing too much inductance into the grounding system. I asked the question because I wanted to know more about the relationship between a good (short) RF ground wire and a ground radial system. Does one work better than the other or should both be used together? Where's John Doty when we need him? :-) ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- jimg Oregon USA |
"jimg" wrote it's always important to keep the ground wire length well below 1/4 wavelength of the max freq your interested in. Assuming it's short enough to prevent distributed effects, the self inductance of a straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about 1Kohm...thats a fair amount of impedance and is why you pick up all that noise..... so what's the ground radial system do? in short, it provides the counter-poise to the wire strung in the sky. the antenna-ground system create the differential signal which is applied to your receiver's rf amp...the better the ground poise, the more 'sensitive' your antenna...is this some kind of linear relationship? like double the ground system and double the antenna sensitivity...nope , not that simple and there's not enuf room here to make all the variables clear...but the better the grounding system, the better your antenna will "work"...some ppl have a good enough conduction under the soil that a simple 10' ground rod intersects this "layer" and the dx cpmes rolling in...other ppl have rods sunk in the earth and buried in wild patterns all over the yard to get the same effect..... so the simple answer(s) is: your ground wire length influences noise (what we call common-field) pick-up so shorter is better; the ground radial system improves the signal strength at the receiver input...and i hate simple answers to a very complicated system... Well put. It's good to keep it simple! Some re-emphasis: RF GROUND is at the transmitter-side, where avoidance of 1/4 wave length prevents monster impedance that is not felt as ground at all. A short path to multiple ground rods connected in parallel completely avoids this 1/4 wave effect no matter what frequency you xmit on. XMTR RF GROUND has no effect on receiving at all, *if * the static grounding and radials (below) are used. STATIC/LIGHTNING GROUND is grounding the coax-shield at several points, beginning right outside the shack, at the base of a wire antenna or tower, mid-point, and top of tower. RADIALS are for reflecting transmitted energy from the antenna that would otherwise be lost (absorbed) by the earth. They have a much smaller but measurable benefit to the receiving aspect of any antenna. They can be above ground (right under an elevated vertical, where very short lengths work), along the surface of the ground on a ground-based vertical, or buried in a large pattern around a vertical, center-fed inverted-L, or in some cases, random wires or inverted-L's. A 1/2 wave horizontal dipole is a "complete" antenna and has no benefit from radials, but it must be elevated sufficiently to avoid ground losses. The coax-shield of feedline to a dipole should still be grounded per above para. -- WARNING: That ground screw on the back of your receiver set could get you in more trouble than it's worth. First, the receiver-case is already grounded via your home's electrical system. Noise and static on the coax-shield should be shorted to ground outside from coax-shield grounding. If you connect your receiver to a separate outside ground, you have major lightning issues if you leave that receiver-ground connected during storms. This is true even if *everything* else is disconnected. If any tree or structure within up to several hundred feet of your property is struck by lightning, your ground system will be a sink for some of that energy, and draw it right into the radio via ground connections. Of course the antennas would add to this problem, but most people remember to disconnect them before a storm. Putting disconnected antenna feedlines in a mason-jar is an embarrassing practice that I got away with for about ten years, and I'm sure many hobbyists play the same odds. Better than nothing (which is the glass-jar trick) would be to short the antennas to an RF-ground, if you have one. If you decide that a separate receiver-ground is important, you should consider what you will do with that "hot-wire" before lightning occurs anywhere in a wide-area around your property. Jack Painter Virginia Beach, Virginia |
jimg wrote:
jimg wrote: it's always important to keep the ground wire length well below 1/4 wavelength of the max freq your interested in. Assuming it's short enough to prevent distributed effects, the self inductance of a straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about 1Kohm...thats a fair amount of impedance and is why you pick up all that noise..... so what's the ground radial system do? in short, it provides the counter-poise to the wire strung in the sky. the antenna-ground system create the differential signal which is applied to your receiver's rf amp...the better the ground poise, the more 'sensitive' your antenna...is this some kind of linear relationship? like double the ground system and double the antenna sensitivity...nope , not that simple and there's not enuf room here to make all the variables clear...but the better the grounding system, the better your antenna will "work"...some ppl have a good enough conduction under the soil that a simple 10' ground rod intersects this "layer" and the dx cpmes rolling in...other ppl have rods sunk in the earth and buried in wild patterns all over the yard to get the same effect..... so the simple answer(s) is: your ground wire length influences noise (what we call common-field) pick-up so shorter is better; the ground radial system improves the signal strength at the receiver input...and i hate simple answers to a very complicated system... That's a good start. The radials make the signal stronger and a good RF ground makes it quieter. Both add to the intelligibility of the signal. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
JP,
.. Mason-Jar ? Great Balls of Lightning ! ;-} .. I have used old metal Film Canisters each mounted to the stations Ground Buss; one per PL-259 Plug. .. Also a small tall Tin Can mounted to the stations Ground Buss with two to Four PL-259 Plugs jammed it to it. .. Now I use an Alpha-Delta Antenna Switch with a "Disconnected-and-Grounded" Center Position when things are not in use. http://www.universal-radio.com/catalog/switch/2415.html http://www.universal-radio.com/catalog/switch/1864.html http://www.universal-radio.com/catalog/switch/2811.html .. iane ~ RHF |
"RHF" wrote JP, . Mason-Jar ? Great Balls of Lightning ! ;-} . I have used old metal Film Canisters each mounted to the stations Ground Buss; one per PL-259 Plug. . Also a small tall Tin Can mounted to the stations Ground Buss with two to Four PL-259 Plugs jammed it to it. . Now I use an Alpha-Delta Antenna Switch with a "Disconnected-and-Grounded" Center Position when things are not in use. http://www.universal-radio.com/catalog/switch/2415.html http://www.universal-radio.com/catalog/switch/1864.html http://www.universal-radio.com/catalog/switch/2811.html . iane ~ RHF I thought you would get a kick out of the mason-jar trick! Live and learn. What are your Alpha-Delta Antenna Switches "grounded" to when in the center position? Where are they mounted? Some of you will remember I operate a USCG Auxiliary communications station, and when on duty, do not secure for wx. That required a complete lightning protection system which cost about $4500 in electrical design, labor and materials (surge suppression), plus another several hundred in materials (external ground system and bonding) which I installed. That does not include the standby power (generator) btw. I researched the grounding, bonding and surge suppression issues for over two years before embarking on that plan. Also studied the damages that occurred to stations (amateur, broadcast and government) who had lightning protection systems, and those that did not. I still follow every published story of lightning damage to US communication stations, and have a current library of (US) NEC and NFPA codes. My system's baptism by fire came the same afternoon the contractors were cleaning up to leave in July 2004. Over 1,000 strikes in a 10 mile area, about 300 in my immediate area, and perhaps a dozen almost on top of me. Trees in my yard and on both sides of my HF antennas were struck, and the power spiked relentlessly, eventually calling for the generator due to electrical noise and high voltages. Dozens of electrical storms later, the system continues to perform as expected. When I give advice to SWL hobbyists about lightning safety, it's because I went through years of worry and learning curves of what works, what doesn't, and the safest ways to operate (or isolate) from various stages of hobby listening, to nearly full-time service for the USCG. Although the antenna systems have changed somewhat from the schematics on the website, the basic system is described at http://members.cox.net/pc-usa/station/ground0.htm This is the time btw, to commence any plans some of you may have had to install or upgrade lightning protection systems, not in the Spring or Summer when thunderstorms can occur without warning! O.K. Steve in Detroit you will have to wait until the ground thaws, lol. Jack Painter Virginia Beach, Virginia |
JP,
.. I have an Aluminum Sheet that covers a 1'x2' board that is mount on the wall. This is the Shack's Ground and the Alpha-Delta Antenna Switch is mounted on this metal sheet. .. ~ RHF |
"RHF" wrote JP, . I have an Aluminum Sheet that covers a 1'x2' board that is mount on the wall. This is the Shack's Ground and the Alpha-Delta Antenna Switch is mounted on this metal sheet. . ~ RHF . Good job. Jack |
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