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high earth resistance
On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen
wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. 73's Richard Clark, KB7QHC |
high earth resistance
On Mon, 09 Apr 2007 08:21:36 -0700, dansawyeror
wrote: What coupling does this imply? Is it direct as is contact or is it a field coupling as capacitive or inductive? Hi Dan, Yes to all three. The question is: what would insulation or corrosion due to buried radials? Not much, practically; unless the wire is extremely thin, and the currents are large. Loss is in the earth. You can, of course, build a very crummy radial system if you try hard. For instance, using expensive piano wire in place of cheap house wiring. 73's Richard Clark, KB7QHC |
high earth resistance
Richard Clark wrote:
On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. Which page? Roy Lewallen, W7EL |
high earth resistance
On Mon, 09 Apr 2007 09:08:09 -0700, Roy Lewallen
wrote: Richard Clark wrote: On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. Which page? Hi Roy, It is distributed through the discussion. Pg. 757 (at the top of the page introduces): "These losses are due to conduction of earth currents through a high resistance earth..." "Where there are radial ground wires present, the earth current consists of two components, part of which flows in the earth itself and the remainder of which flows in the buried wires." "...all the various components differ in phase." This establishes the relationship and distinction in the various currents. It is the current in the earth that is the topic of discussion here. That current is out of phase with respect to the currents (at the same radial distance) found in the buried wires. No wires, no phase issue. No phase issue, and earth currents would be radial. Now, to distinguish this from circumferential is not to say this is absolute (it does not follow an arc of constant radius). This is extended to coverage at the bottom of page 758: "The actual earth current and the current flowing in the radial wires are given...." [formula shown in the original] "From (8) [that formula] we see that the earth current proper leads the current in the wires by 90 electrical degrees." At a radius, the earth phase and the wire phase exhibit a potential difference which results in conduction that is not strictly radial (the term circumferential through the combination of vectors might be replaced with spiral, or diagonal). The earth's resistance comes into play at page 760: "When the earth is of good conductivity [a paradox ensues], the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." and hence the advice for replacing dirt with sand OR providing more closely spaced radials, closer in. "Thus the regions of high current density are subjected to still more current with higher losses in these regions." 73's Richard Clark, KB7QHC |
high earth resistance
Richard,
I disagree with your conclusion that currents flow circumferentially. It does not say so in the paper, and I don't believe it can be inferred from what is said in the paper. If you were to draw a diagram showing the currents produced by the phase shift between earth and radial currents, you'd find that the net current resulting from this phase shift is purely radial, not circumferential. If the currents flow circumferentially, do they flow clockwise or counterclockwise, and at what magnitude relative to the radial currents? Surely there's some reference which shows this calculation which you could direct me to or, if not, you could show how the calculation is done and what the result is. Roy Lewallen, W7EL Richard Clark wrote: On Mon, 09 Apr 2007 09:08:09 -0700, Roy Lewallen wrote: Richard Clark wrote: On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. Which page? Hi Roy, It is distributed through the discussion. Pg. 757 (at the top of the page introduces): "These losses are due to conduction of earth currents through a high resistance earth..." "Where there are radial ground wires present, the earth current consists of two components, part of which flows in the earth itself and the remainder of which flows in the buried wires." "...all the various components differ in phase." This establishes the relationship and distinction in the various currents. It is the current in the earth that is the topic of discussion here. That current is out of phase with respect to the currents (at the same radial distance) found in the buried wires. No wires, no phase issue. No phase issue, and earth currents would be radial. Now, to distinguish this from circumferential is not to say this is absolute (it does not follow an arc of constant radius). This is extended to coverage at the bottom of page 758: "The actual earth current and the current flowing in the radial wires are given...." [formula shown in the original] "From (8) [that formula] we see that the earth current proper leads the current in the wires by 90 electrical degrees." At a radius, the earth phase and the wire phase exhibit a potential difference which results in conduction that is not strictly radial (the term circumferential through the combination of vectors might be replaced with spiral, or diagonal). The earth's resistance comes into play at page 760: "When the earth is of good conductivity [a paradox ensues], the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." and hence the advice for replacing dirt with sand OR providing more closely spaced radials, closer in. "Thus the regions of high current density are subjected to still more current with higher losses in these regions." 73's Richard Clark, KB7QHC |
high earth resistance
On Mon, 09 Apr 2007 12:12:32 -0700, Roy Lewallen
wrote: I disagree with your conclusion that currents flow circumferentially. It does not say so in the paper, and I don't believe it can be inferred from what is said in the paper. Hi Roy, To insist that the paper be complete where the reader has the competence to understand what is implied; well, that goes beyond standard practice. Further, the implication is hardly momentous when the force of the writing is in demonstrating (not finding) a solution to loss. Their style is clearly descriptive, not pedantic. One very simple observation drawn directly from the text at page 760: "When the earth is of good conductivity, the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." How is it THIS current is traveling radially, the same direction as the wires, both leaving the wire (an orthogonal aspect) and yet moving in the same direction. This is a contradiction to the geometry of the description if we are to abide by your rejection of my "interpretation." Their (not my) statement, supported by their other text, hardly makes sense otherwise. Current only flows along a potential gradient and the phase shift between (by their own distinctions) wire and ground constitutes such a gradient. It is a vastly more speculative "interpretation" to suggest the current leaves the wire to travel in the same direction and the authors definitely don't say that, do they? Common sense would dictate a fairer interpretation that conforms to phases and the distinctions (separation of currents) they drew from them. 73's Richard Clark, KB7QHC |
high earth resistance
So, does the current go clockwise or counterclockwise? How much goes
that way compared to the radial component? Where can I find a quantitative or explicit statement of your interpretation? Roy Lewallen, W7EL Richard Clark wrote: On Mon, 09 Apr 2007 12:12:32 -0700, Roy Lewallen wrote: I disagree with your conclusion that currents flow circumferentially. It does not say so in the paper, and I don't believe it can be inferred from what is said in the paper. Hi Roy, To insist that the paper be complete where the reader has the competence to understand what is implied; well, that goes beyond standard practice. Further, the implication is hardly momentous when the force of the writing is in demonstrating (not finding) a solution to loss. Their style is clearly descriptive, not pedantic. One very simple observation drawn directly from the text at page 760: "When the earth is of good conductivity, the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." How is it THIS current is traveling radially, the same direction as the wires, both leaving the wire (an orthogonal aspect) and yet moving in the same direction. This is a contradiction to the geometry of the description if we are to abide by your rejection of my "interpretation." Their (not my) statement, supported by their other text, hardly makes sense otherwise. Current only flows along a potential gradient and the phase shift between (by their own distinctions) wire and ground constitutes such a gradient. It is a vastly more speculative "interpretation" to suggest the current leaves the wire to travel in the same direction and the authors definitely don't say that, do they? Common sense would dictate a fairer interpretation that conforms to phases and the distinctions (separation of currents) they drew from them. 73's Richard Clark, KB7QHC |
high earth resistance
Severns' article "Verticals, Ground Systems and Some History",
July 2000, p. 39, quotes the following: "As indicated in Figure 1, the tangential component of the H field (H(phi)) induces horizontal currents (Ih) flowing radially and the normal component of the E field (Ez) induces vertically flowing currents (Iv). The paper is available for download from www.arrl.org. Frank "Roy Lewallen" wrote in message ... Richard, I disagree with your conclusion that currents flow circumferentially. It does not say so in the paper, and I don't believe it can be inferred from what is said in the paper. If you were to draw a diagram showing the currents produced by the phase shift between earth and radial currents, you'd find that the net current resulting from this phase shift is purely radial, not circumferential. If the currents flow circumferentially, do they flow clockwise or counterclockwise, and at what magnitude relative to the radial currents? Surely there's some reference which shows this calculation which you could direct me to or, if not, you could show how the calculation is done and what the result is. Roy Lewallen, W7EL Richard Clark wrote: On Mon, 09 Apr 2007 09:08:09 -0700, Roy Lewallen wrote: Richard Clark wrote: On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. Which page? Hi Roy, It is distributed through the discussion. Pg. 757 (at the top of the page introduces): "These losses are due to conduction of earth currents through a high resistance earth..." "Where there are radial ground wires present, the earth current consists of two components, part of which flows in the earth itself and the remainder of which flows in the buried wires." "...all the various components differ in phase." This establishes the relationship and distinction in the various currents. It is the current in the earth that is the topic of discussion here. That current is out of phase with respect to the currents (at the same radial distance) found in the buried wires. No wires, no phase issue. No phase issue, and earth currents would be radial. Now, to distinguish this from circumferential is not to say this is absolute (it does not follow an arc of constant radius). This is extended to coverage at the bottom of page 758: "The actual earth current and the current flowing in the radial wires are given...." [formula shown in the original] "From (8) [that formula] we see that the earth current proper leads the current in the wires by 90 electrical degrees." At a radius, the earth phase and the wire phase exhibit a potential difference which results in conduction that is not strictly radial (the term circumferential through the combination of vectors might be replaced with spiral, or diagonal). The earth's resistance comes into play at page 760: "When the earth is of good conductivity [a paradox ensues], the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." and hence the advice for replacing dirt with sand OR providing more closely spaced radials, closer in. "Thus the regions of high current density are subjected to still more current with higher losses in these regions." 73's Richard Clark, KB7QHC |
high earth resistance
The article is in QST.
"Frank's" wrote in message news:6qxSh.56971$__3.40608@edtnps90... Severns' article "Verticals, Ground Systems and Some History", July 2000, p. 39, quotes the following: "As indicated in Figure 1, the tangential component of the H field (H(phi)) induces horizontal currents (Ih) flowing radially and the normal component of the E field (Ez) induces vertically flowing currents (Iv). The paper is available for download from www.arrl.org. Frank "Roy Lewallen" wrote in message ... Richard, I disagree with your conclusion that currents flow circumferentially. It does not say so in the paper, and I don't believe it can be inferred from what is said in the paper. If you were to draw a diagram showing the currents produced by the phase shift between earth and radial currents, you'd find that the net current resulting from this phase shift is purely radial, not circumferential. If the currents flow circumferentially, do they flow clockwise or counterclockwise, and at what magnitude relative to the radial currents? Surely there's some reference which shows this calculation which you could direct me to or, if not, you could show how the calculation is done and what the result is. Roy Lewallen, W7EL Richard Clark wrote: On Mon, 09 Apr 2007 09:08:09 -0700, Roy Lewallen wrote: Richard Clark wrote: On Sun, 08 Apr 2007 23:56:37 -0700, Roy Lewallen wrote: Indeed it is. Can you point me to a reference where I can get a more detailed explanation of this circumferential current and its cause? Hi Roy, Brown, Lewis and Epstein. Which page? Hi Roy, It is distributed through the discussion. Pg. 757 (at the top of the page introduces): "These losses are due to conduction of earth currents through a high resistance earth..." "Where there are radial ground wires present, the earth current consists of two components, part of which flows in the earth itself and the remainder of which flows in the buried wires." "...all the various components differ in phase." This establishes the relationship and distinction in the various currents. It is the current in the earth that is the topic of discussion here. That current is out of phase with respect to the currents (at the same radial distance) found in the buried wires. No wires, no phase issue. No phase issue, and earth currents would be radial. Now, to distinguish this from circumferential is not to say this is absolute (it does not follow an arc of constant radius). This is extended to coverage at the bottom of page 758: "The actual earth current and the current flowing in the radial wires are given...." [formula shown in the original] "From (8) [that formula] we see that the earth current proper leads the current in the wires by 90 electrical degrees." At a radius, the earth phase and the wire phase exhibit a potential difference which results in conduction that is not strictly radial (the term circumferential through the combination of vectors might be replaced with spiral, or diagonal). The earth's resistance comes into play at page 760: "When the earth is of good conductivity [a paradox ensues], the current leaves the wires and enters the earth closer to the antenna than it does when the earth is a poor conductor." and hence the advice for replacing dirt with sand OR providing more closely spaced radials, closer in. "Thus the regions of high current density are subjected to still more current with higher losses in these regions." 73's Richard Clark, KB7QHC |
high earth resistance
Owen Duffy wrote in
: dansawyeror wrote in : ... I think a summary is that at 3970KHz, the feedpoint Z looks like about 45 +j0 and you reckon the radiation resistance should be around 4+j0, suggesting the earth system contributes around 40 ohms of resistance. Observations at a single frequency provide a limited view of what might be happening. Dan, I asked your for the details of your antenna and measurements, and how you did your calculations, but I am still left wondering how you have what appears to be a purely resistive feedpoint impedance and a radiation resistance of 4 ohms. The second implies a short vertical, and if that is the case, the first implies some form of loading... but you didn't mention loading of any kind. Loading, if you have used it, may introduce an equivalent series resistance at the feedpoint. Once again, a dansawyer problems leaves us guessing to fill in the missing dots before attempting to joint them up to make a picture. Often, solving a problem is about being able to draw the picture, once the picture is draw, the answer becomes trivial. Owen |
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