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On 27 Mar, 09:55, (Richard Harrison) wrote:
Art wrote: "---yet I am not finding any documented proof other than emperical work." As usual, Terman has answers. See page 882 of his 1955 opus: "Effect of Ground on the Directional Pattern of Ungrounded Antennas - Image Antennas." It`s in the book; math, diagrams, tables, as needed to imagine what happens. Best regards, Richard Harrison, KB5WZI Thank you for that I will get right on it. I presume it does give direct relationships between electrical and magnetic vectors relative to the conductor and ground ! |
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Richard Harrison wrote:
Jim Pennino wrote: "Have you ever heard of a helix?" Most would likely enjoy Kraus` story of his invention of the axial-mode helix in his 3rd edition of "Antennas". ' "No," he replied, "I've tried it and it doesn't work."' |
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On 27 mar, 19:47, "art" wrote:
On 27 Mar, 10:20, (Richard Harrison) wrote: Jim Pennino wrote: "Have you ever heard of a helix?" Most would likely enjoy Kraus` story of his invention of the axial-mode helix in his 3rd edition of "Antennas". This is a choice book! Best regards, Richard Harrison, KB5WZI I have his second edition and I find no mention of radiation from the beginning where current is applied onwards. Have you found anything that can contribute other than empirical grounds? You have avoided the question so far Hello Art, Radiation from accelerating charge is fully understood (from theory and verified practically), hence antenna theory. When you take the complete formula for fields (near and far) generated by a short wire segment (hertzian dipole), you can calculate the far and near field (magnitude, orientation, phase, etc) from every construction. The only problem is that you have to know the current distribution in your construction. It is not of interest whether the charge is excited by just a voltage source or EM radiation (like in reflection of waves on conductors and dielectrics). This is done in many FEM programs. Of course in many practical circumstances it is easier to use the "laws" from other people (that are derived from basic theory). One of the results are the Fresnel formulas for reflection. When you know the properties of the soil at the operating frequency, you can calculate the complex surface impedance and hence the complex reflection coefficient. Just mentioning words as "curl", "vector", "Gaussian" etc, doesn't make sense without further information. Best Regards, Wim |
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On 27 Mar, 12:22, "Wimpie" wrote:
On 27 mar, 19:47, "art" wrote: On 27 Mar, 10:20, (Richard Harrison) wrote: Jim Pennino wrote: "Have you ever heard of a helix?" Most would likely enjoy Kraus` story of his invention of the axial-mode helix in his 3rd edition of "Antennas". This is a choice book! Best regards, Richard Harrison, KB5WZI I have his second edition and I find no mention of radiation from the beginning where current is applied onwards. Have you found anything that can contribute other than empirical grounds? You have avoided the question so far Hello Art, Radiation from accelerating charge is fully understood (from theory and verified practically), hence antenna theory. When you take the complete formula for fields (near and far) generated by a short wire segment (hertzian dipole), you can calculate the far and near field (magnitude, orientation, phase, etc) from every construction. The only problem is that you have to know the current distribution in your construction. It is not of interest whether the charge is excited by just a voltage source or EM radiation (like in reflection of waves on conductors and dielectrics). This is done in many FEM programs. Of course in many practical circumstances it is easier to use the "laws" from other people (that are derived from basic theory). One of the results are the Fresnel formulas for reflection. When you know the properties of the soil at the operating frequency, you can calculate the complex surface impedance and hence the complex reflection coefficient. Just mentioning words as "curl", "vector", "Gaussian" etc, doesn't make sense without further information. Best Regards, Wim- Hide quoted text - - Show quoted text - Wim I accept all of what you write . I can get the angle from computor programs based on Maxwell. but the computor program is not enough! I would like to see a mathematical proof of the tip angle required of a vertical to provide a wave front at 90 degrees to the tip angle. I see graphs of tip angles for a long legged "v" in Terman but not for a simple vertical or horizontal radiator. Can you point me to a paper that burrows deeply into this question either over a perfect ground or in free space? Art |
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On 27 Mar 2007 10:51:27 -0700, "art" wrote:
I presume it does give direct relationships between electrical and magnetic vectors relative to the conductor and ground ! Hi Art, As this is all very elementary stuff, of course Terman does. 73's Richard Clark, KB7QHC |
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Art wrote:
"I have his (Kraus`) second edition (Antennas) and I find no mention of radiation from the beginning where current is applied onward." I think I have that edition too. If you review the chapter on "Point Sources" you`ll find: power patterns, a power theorem and its application to isotropic sources, rediation intensity, source with hemispheric power pattern, unidirectional cosine power pattern, etc., etc.. The new, now available 3rd ed. of "Antennas" by Kraus, Marhefka, and a host of others is greatly expanded and improved. It is worth the investment. Being uncertain of what Art really wants, doesn`t stop me from advising him to start by having a look at the famous Sommerfeld formula on page 804 of Terman`s 1955 opus. It predicts 1 kilowatt will produce 186 mv per m at a distance of 1 mile from a short vertical transmitting antenna given a certain ground conductivity and other conditions. Best regards, Richard Harrison, KB5WZI |
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On 27 Mar, 15:12, (Richard Harrison) wrote:
Art wrote: "I have his (Kraus`) second edition (Antennas) and I find no mention of radiation from the beginning where current is applied onward." I think I have that edition too. If you review the chapter on "Point Sources" you`ll find: power patterns, a power theorem and its application to isotropic sources, rediation intensity, source with hemispheric power pattern, unidirectional cosine power pattern, etc., etc.. The new, now available 3rd ed. of "Antennas" by Kraus, Marhefka, and a host of others is greatly expanded and improved. It is worth the investment. Being uncertain of what Art really wants, doesn`t stop me from advising him to start by having a look at the famous Sommerfeld formula on page 804 of Terman`s 1955 opus. It predicts 1 kilowatt will produce 186 mv per m at a distance of 1 mile from a short vertical transmitting antenna given a certain ground conductivity and other conditions. Best regards, Richard Harrison, KB5WZI Richard, I have lots of books but as yet have not found the answer even tho many have posted none appear to really have an answer other than to throw stones. You apparently have found the answer! Could you quote from the books that you are refering to the angle of radiation relative to the radiator, thats it ? If you can't understand that then relay to me the angle of a radiation front relative to a radiator, I'm sure some other people are interested in what you found. Even better, let me know the TOA of a dipole in free space and how much it varies to that of the same dipole over a perfect ground. Use a computor program if you like, anything that sheds light on the matter . The books say that a horizontal "v" antenna should be tipped for max gain, doesn't that raise your interest about the reasoning and mathematics behind this? Jimmie D asked me to state this angle but I have only a expensive computor program that doesn't give the math with the answer. Please read off the angle and the specifics so we all can move on, I don't want a 160 thread postings some thrust upon Walt Art |
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Art wrote:
"Could you quote from the books that you are referring to the angle relative to the radiator, that`s it?" O.K.. but the angle is relative to the horizontal in the statement. Termans 1955 opus on page 804 says the strength of radiation from a short vertical antenna is proportional to the cosine of the elevation angle. That`s right because at zero angle, radiation is maximumm as cosine of zero degrees is 1, and cosine of 90 degrees is zero. Best regards, Richard Harrison, KB5WZI |
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Richard Clark, W7QHC wrote:
"-you know, the basic stuff of propagation." I may be able to respond to a question, but I don`t write books. On the question of ground conductivity and polarization: Soil loss makes vertically polarized waves tilt forward in the direction of their travel as if dragging their feet. It`s not all bad as this tilt makes a horizontal antenna, the Beverage, receive these vertically polarized waves well. Best regards, Richard Harrison, KB5WZI |
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