Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
Brian, I understand that the VF varies with soil type. One could just compensate by being conservative but who wants to use 30/40% more wire than needed. Why does the ON4UN book ignore VF when doing the example problems? Should I shorten to take into account VF? 73 Doug EI2CN -Original Message- From: k8...@hughes.net [mailto:k8...@hughes.net] Sent: 19 December 2014 00:08 To: Doug Turnbull; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Hello Doug, The 50-60% figure depends on your soil conditions, so may vary quite a bit. With my poor, sandy soil, the Vf is 67.7% with the radials laying on the ground. When I buried them 6, the Vf was 39.8%. Using these shortened radials, there wasn't much improvement going beyond 16 radials. To find out your soil conditions, simply lay a temporary dipole on the ground and use an analyzer to find it's resonance. Then trim to length. Now you have your first two radials! Good luck Brian K8BHZ -Original Message- From: Doug Turnbull Sent: Thursday, December 18, 2014 4:18 PM To: topband@contesting.com Subject: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
Doug you are laying radials on the ground, they if on or under the ground are non resonant. You are essentially trying to produce a cooper shield by way of the radials. Seeing your vertical is about 100ft high just lay 60+ radials of 1/4 wave and you are done. 73 Clive GM3POI -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Doug Turnbull Sent: 19 December 2014 10:29 To: k8...@hughes.net; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. Brian, I understand that the VF varies with soil type. One could just compensate by being conservative but who wants to use 30/40% more wire than needed. Why does the ON4UN book ignore VF when doing the example problems? Should I shorten to take into account VF? 73 Doug EI2CN -Original Message- From: k8...@hughes.net [mailto:k8...@hughes.net] Sent: 19 December 2014 00:08 To: Doug Turnbull; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Hello Doug, The 50-60% figure depends on your soil conditions, so may vary quite a bit. With my poor, sandy soil, the Vf is 67.7% with the radials laying on the ground. When I buried them 6, the Vf was 39.8%. Using these shortened radials, there wasn't much improvement going beyond 16 radials. To find out your soil conditions, simply lay a temporary dipole on the ground and use an analyzer to find it's resonance. Then trim to length. Now you have your first two radials! Good luck Brian K8BHZ -Original Message- From: Doug Turnbull Sent: Thursday, December 18, 2014 4:18 PM To: topband@contesting.com Subject: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
Radials on the ground do not have a magic length. Worrying about resonance for them is not necessary. If you tune a quarter wave wire up in the air - then lay it onto the ground - it couples to the ground and is no longer a distinct single piece of wire. Just make them an easy length to deal with and put as many of them down as you can. Tree N6TR On Fri, Dec 19, 2014 at 2:28 AM, Doug Turnbull turnb...@net1.ie wrote: Brian, I understand that the VF varies with soil type. One could just compensate by being conservative but who wants to use 30/40% more wire than needed. Why does the ON4UN book ignore VF when doing the example problems? Should I shorten to take into account VF? 73 Doug EI2CN -Original Message- From: k8...@hughes.net [mailto:k8...@hughes.net] Sent: 19 December 2014 00:08 To: Doug Turnbull; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Hello Doug, The 50-60% figure depends on your soil conditions, so may vary quite a bit. With my poor, sandy soil, the Vf is 67.7% with the radials laying on the ground. When I buried them 6, the Vf was 39.8%. Using these shortened radials, there wasn't much improvement going beyond 16 radials. To find out your soil conditions, simply lay a temporary dipole on the ground and use an analyzer to find it's resonance. Then trim to length. Now you have your first two radials! Good luck Brian K8BHZ -Original Message- From: Doug Turnbull Sent: Thursday, December 18, 2014 4:18 PM To: topband@contesting.com Subject: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
I can’t agree with this “conventional” thinking. Why does a piece of wire magically lose it’s length just because you lay it on the ground? The electrical length changes because of Vf, and it’s resistance changes because of the lossy ground, but it’s still a piece of wire. I’m going to try to attach a posting I did back in 2006. If it doesn’t work, I will follow with a separate posting. Brian K8BHZ From: Tree Sent: Friday, December 19, 2014 10:07 AM To: Doug Turnbull Cc: k8...@hughes.net ; 160 Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. Radials on the ground do not have a magic length. Worrying about resonance for them is not necessary. If you tune a quarter wave wire up in the air - then lay it onto the ground - it couples to the ground and is no longer a distinct single piece of wire. Just make them an easy length to deal with and put as many of them down as you can. Tree N6TR On Fri, Dec 19, 2014 at 2:28 AM, Doug Turnbull turnb...@net1.ie wrote: Brian, I understand that the VF varies with soil type. One could just compensate by being conservative but who wants to use 30/40% more wire than needed. Why does the ON4UN book ignore VF when doing the example problems? Should I shorten to take into account VF? 73 Doug EI2CN -Original Message- From: k8...@hughes.net [mailto:k8...@hughes.net] Sent: 19 December 2014 00:08 To: Doug Turnbull; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Hello Doug, The 50-60% figure depends on your soil conditions, so may vary quite a bit. With my poor, sandy soil, the Vf is 67.7% with the radials laying on the ground. When I buried them 6, the Vf was 39.8%. Using these shortened radials, there wasn't much improvement going beyond 16 radials. To find out your soil conditions, simply lay a temporary dipole on the ground and use an analyzer to find it's resonance. Then trim to length. Now you have your first two radials! Good luck Brian K8BHZ -Original Message- From: Doug Turnbull Sent: Thursday, December 18, 2014 4:18 PM To: topband@contesting.com Subject: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
An awful lot of our advice depends on unnoticed assumptions based in the commercial BC paradigm. Go to any place where there is a commercial AM BC tower. Figure out a one wavelength radius circle around the tower(s) . Tell me how many trees you see in the circle(s). Tell me whether it is mostly level. Tell me how many above-ground conductors bisect the area. Tell me if it is cluttered by anything other than mandatory buildings, and how large they are. Tell me if the field surface is uniform grass or has a lot of roots that would take the actual ground characteristics completely off a straight line scale of pure ground characteristics. In testing velocity factor for in/on ground RX antennas in the NC counties around Raleigh/Durham, we discovered that in the same back yard a 90 degree reorientation of the test DOG (dipole on ground) could make enormous difference of VF, clearly indicating that trying to actually put down VF compensated 1/4 wave radials could not be done with a single test DOG figure. Also the VF varied wildly with varying height above actual ground. One had to notch through the grass down to the actual surface of the dirt, for the entire length, to get repeatable figures. On top of the grass, and notched down to or just barely into the dirt gave very different answers. Just barely into the dirt was the most consistent, but still varied with moisture content. One needed to AVOID measuring in a dry season, unless that was normal for most of the year. The problem with the typical as many as you can of whatever advice is that the unbalanced from miscellaneous length, environment and density as you go around the compass *induces additional loss*. The commercial BC paradigm is full size, dense and uniform all around. They do not discuss the effects of the miscellany we hams introduce into radial implementation. It is not allowed. The uniformity is real estate bought, cleared, bulldozed, and specifically constructed. 60 plus radials of 1/4 wave advice to a ham is an unexplained advice to create the BC grade uniformity. For many locations, the full size, dense and uniform all around installation of 16 to 32 raised radials will outperform on/in ground radials. This is because the RF fields can be uniform all around in the elevated, and the particulars of the location (as in buried radials in the woods, or back yards with buried iron pipe and electrical feeds) will defeat uniformity in on/in ground radials and add losses due to the actual entire content of the stuff underfoot. Raised anything in the woods does add a significant unavoidable maintenance chore. But remember that all the factual praise of on/in ground radials depends on the *assumed* context of commercial BC uniformity of installation and location. There is a certain level of on/in ground radial miscellany, or even elevated radial miscellany, that will be clearly beaten using an FCP or even as few as four 1/8 wave elevated tuned radials for counterpoise. With these arrangements the current maximum can be moved up the vertical wire, which helps elevate radiation above local clutter for low angles, be it buildings or trees. Radials really need that commercial BC grade uniformity in all its aspects. Or we become lossily counterpoise-limited. 73, Guy K2AV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
What you're missing is that a conductor carrying an *alternating* current, like RF, also has reactance. Reactance is influenced by capacitance and inductance. The earth, being essentially somewhere between a lossy conductor and a lossy dielectric, can influence the electrical properties of the wire. Velocity factor is influenced by properties of the dielectric. Notice how there are feedlines that are the same impedance, and have the same outside diameter but one has a foamed PE dielectric and the other solid (like RG8 and RG213)? The velocity factor is higher in the foamed dielectric. The electrical length of such cables will be different even though the only physical differences are the differing dielectric materials and slightly different gauges of the center conductors. A radial is actually more complex than just a piece of wire on the ground with resistance. It doesn't lose it's length, but the reactive properties of the wire (or any wire for that matter) will change as that wire is either bent, or brought into close proximity with other wires or dielectric materials. Remember that an inductor is also just a piece of wire with resistance, but when that wire is coiled it acts as an inductor more than just a simple piece of wire. There are also the other reasons for resonant length being less important with radials (many in parallel, etc.) when they're on the ground that have been discussed many times in the past. The DC resistance of the radial itself does not change when brought near the ground, but the AC properties of the wire do. -Bill KB8WYP -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of k8...@hughes.net Sent: Friday, December 19, 2014 12:21 PM To: Tree; topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. I can’t agree with this “conventional” thinking. Why does a piece of wire magically lose it’s length just because you lay it on the ground? The electrical length changes because of Vf, and it’s resistance changes because of the lossy ground, but it’s still a piece of wire. I’m going to try to attach a posting I did back in 2006. If it doesn’t work, I will follow with a separate posting. Brian K8BHZ From: Tree Sent: Friday, December 19, 2014 10:07 AM To: Doug Turnbull Cc: k8...@hughes.net ; 160 Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. Radials on the ground do not have a magic length. Worrying about resonance for them is not necessary. If you tune a quarter wave wire up in the air - then lay it onto the ground - it couples to the ground and is no longer a distinct single piece of wire. Just make them an easy length to deal with and put as many of them down as you can. Tree N6TR On Fri, Dec 19, 2014 at 2:28 AM, Doug Turnbull turnb...@net1.ie wrote: Brian, I understand that the VF varies with soil type. One could just compensate by being conservative but who wants to use 30/40% more wire than needed. Why does the ON4UN book ignore VF when doing the example problems? Should I shorten to take into account VF? 73 Doug EI2CN -Original Message- From: k8...@hughes.net [mailto:k8...@hughes.net] Sent: 19 December 2014 00:08 To: Doug Turnbull; Topband@contesting.com Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Hello Doug, The 50-60% figure depends on your soil conditions, so may vary quite a bit. With my poor, sandy soil, the Vf is 67.7% with the radials laying on the ground. When I buried them 6, the Vf was 39.8%. Using these shortened radials, there wasn't much improvement going beyond 16 radials. To find out your soil conditions, simply lay a temporary dipole on the ground and use an analyzer to find it's resonance. Then trim to length. Now you have your first two radials! Good luck Brian K8BHZ -Original Message- From: Doug Turnbull Sent: Thursday, December 18, 2014 4:18 PM To: topband@contesting.com Subject: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations. Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
On 2014-12-19, at 12:21 PM, k8...@hughes.net wrote: I can’t agree with this “conventional” thinking. Why does a piece of wire magically lose it’s length just because you lay it on the ground? The electrical length changes because of Vf, and it’s resistance changes because of the lossy ground, but it’s still a piece of wire. I’m going to try to attach a posting I did back in 2006. If it doesn’t work, I will follow with a separate posting. Brian K8BHZ Hi Brian, The very same reason that it ...magically loses its length when it's incorporated as part of a run of coaxial cable, I guess...! Some parts of Ham radio are STILL black magic---aren't they...? Maybe THAT'S one of the many reasons that we love it so... ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
Hi Doug, As I understand it, the velocity factor of 50% applies for radial wires that are simply laid atop the ground, not buried in any way... But of course, I COULD stand to be corrected..! ~73~ de Eddy VE3CUI - VE3XZ On 2014-12-18, at 4:18 PM, Doug Turnbull wrote: Dear OMs and Yls, I am replacing raised radials for 160M inverted L with ground mounted radials mostly because I could not readily get the raised radials up high enough in my wood and also because of maintenance problems. This inverted L goes up 100 feet at its top before levelling out for the final 32' or so. It should I believe have a strong vertical element. ON4UN's book Low-Band DXing 56th edition is generally excellent but I do find the coverage of ground radials both confusing and somewhat contradictory.This surprises me for what is pretty much considered the bible. On page 9-14 the text states that the velocity factor falls for ground mounted radials to the the order of 50-60%, which means that a radial that is physically 20 meters long is actually a half-wave long electrically! This example is for 80M not 160M.However in the examples found on page 9-15 the velocity factor change is ignored.I understand the velocity factor change and have always accepted this. It generally did not pay to try and cut radials precisely to a given wavelength.I accept the radial length vs. radial number charts but is this an electrical length in free space or a length considerably reduced due to velocity factory change?Example 3 ignores velocity factor correction and from what I can see this correction is ignore in most of the text concerning ground radials. What does one do? Who does one believe. While I am talking about a 160M inverted L; I did reference the SteppIR BigIR vertical manual, page 18.Lengths should be scalable.I find no mention of velocity factor and the shortening effect which is experienced. The recommendations are not very different from those in ON4UNs book. So does this mean one ignores the change in velocity factor? I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. 73 Doug EI2CN _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations.
On Thu,12/18/2014 1:18 PM, Doug Turnbull wrote: I appreciate some guidance with this matter. I would like a radial field which would take me to within 0.5/1 dB of the maximum achievable for reducing near field losses. Some of the best work I've seen published on this topic is by Rudy Severns, N6LF. Look for the 2-part QEX piece he did about 3 years ago. It's on his website and is well worth studying. For my part, I modeled a half-wave 160M dipole parallel to the earth starting at heights of about 5 ft down to a few inches, varied the length so that the antenna was resonant at each height, computed Vf from the result, and plotted it. That work is slides 40 and 41 in http://k9yc.com/160MPacificon.pdf Obviously what happens in the real world will depend on soil conditions. Think about this in the light of Rudy's work -- the standard for broadcast radials has been a half wave length. Taking Vf into account, they would be more like 3/4 wavelength or even longer. Rudy observes that current distribution will depend on the length of the radial, and the boundary condition is that it must be minimum at the end. He notes that if a radial is some length between 0.25 and 0.5 wavelength, the current will peak 0.25 from the far end, and that peak will be greater than the current at the tower base, and because that current is greater, the loss will be greater. He observes that loss will be minimized when the peak current is at the feedpoint. He also observes that loss will be minimized by making the all the radial currents as nearly equal as possible (again, because loss is I squared R), and by sharing that current by more radials (again because loss is I squared R). Rudy further observes that radial current can be unbalanced by variations in soil conditions, including factors like variations in skin depth, and by their electrical length. Like I said, it's REALLY GOOD reading, and it all makes sense. And thanks for the QSO on 10M. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
