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'Doc wrote in message . com...
Dr. Slick wrote: "(1)A properly tuned and positioned dipole will be resonant at only one frequency. (2)Double-dips are a bad sign, and the return loss suffers." (1) - Nope, just not true. (2) - Not true either. (see #1) What i meant to say was, a properly tuned simple dipole will be resonant at only one frequency and it's harmonics. My double dips were not harmonically related. With the two 'dips' not being harmonically related, it appears that there is some 'other' reason, the feed line for one, or something near the antenna (a person for instance?). 'Doc raising the height of the dipole above the ground from 3.5 to 6.5 feet was one of the things i did to fix this problem. The other one no one has guessed yet... S. |
"Dr. Slick" wrote in message om... 'Doc wrote in message . com... Dr. Slick wrote: "(1)A properly tuned and positioned dipole will be resonant at only one frequency. (2)Double-dips are a bad sign, and the return loss suffers." (1) - Nope, just not true. (2) - Not true either. (see #1) What i meant to say was, a properly tuned simple dipole will be resonant at only one frequency and it's harmonics. My double dips were not harmonically related. With the two 'dips' not being harmonically related, it appears that there is some 'other' reason, the feed line for one, or something near the antenna (a person for instance?). 'Doc raising the height of the dipole above the ground from 3.5 to 6.5 feet was one of the things i did to fix this problem. The other one no one has guessed yet... S. This sounds like 20 questions. You are not telling us what you have. One would not expect somebody to measure an antenna at a height of 3 feet. A dipole would have an impedance of around 75 Ohms, which would give an SWR into 50 Ohms of around 1.5:1 Are you using 50 Ohm coax and a 50 Ohm meter? Is there a gamma match, or such, to adjust? Is it a dipole or a folded dipole? Is there a balun? Did you buy the antenna or build it (I suspect the intent would be different)? Since you are using an SWR meter, are you putting enough power into it to get out of the nonlinear range? Tam/WB2TT |
Tam, WB2TT wrote:
"One would not expect somebody to measure an antenna at a height of 3 feet." For reception of nearby broadcast stations a wire at 3 feet above the earth is probably fine but the wire would have a low radiation resistance. The radiation resistance of a 1/2-wave dipole versus its height above ground in wavelengths is probably a familiar graph for many. It starts at zero ohms at zero height and rises in an almost straight inclined line to about 99 ohms at nearly 5/8-wavelength. Then, with increased height, the radiation resistance oscillates as a damped wave around 73 ohms. Best regards, Richard Harrison, KB5WZI |
"Tam/WB2TT" wrote in message ...
raising the height of the dipole above the ground from 3.5 to 6.5 feet was one of the things i did to fix this problem. The other one no one has guessed yet... S. This sounds like 20 questions. You are not telling us what you have. One would not expect somebody to measure an antenna at a height of 3 feet. A dipole would have an impedance of around 75 Ohms, which would give an SWR into 50 Ohms of around 1.5:1 Are you using 50 Ohm coax and a 50 Ohm meter? Yes, all 50 Ohms. Is there a gamma match, or such, to adjust? No. But hint: a physical parameter of the dipole was adjusted. Is it a dipole or a folded dipole? Is there a balun? Did you buy the antenna or build it (I suspect the intent would be different)? Since you are using an SWR meter, are you putting enough power into it to get out of the nonlinear range? MFJ-259. Home-made dipole using aluminum tubing. There are only so many physical parameters of a dipole, folks! Just list them and you should hit it! Slick |
"Dr. Slick" wrote in message om... "Tam/WB2TT" wrote in message ... raising the height of the dipole above the ground from 3.5 to 6.5 feet was one of the things i did to fix this problem. The other one no one has guessed yet... S. This sounds like 20 questions. You are not telling us what you have. One would not expect somebody to measure an antenna at a height of 3 feet. A dipole would have an impedance of around 75 Ohms, which would give an SWR into 50 Ohms of around 1.5:1 Are you using 50 Ohm coax and a 50 Ohm meter? Yes, all 50 Ohms. Is there a gamma match, or such, to adjust? No. But hint: a physical parameter of the dipole was adjusted. Is it a dipole or a folded dipole? Is there a balun? Did you buy the antenna or build it (I suspect the intent would be different)? Since you are using an SWR meter, are you putting enough power into it to get out of the nonlinear range? MFJ-259. Home-made dipole using aluminum tubing. There are only so many physical parameters of a dipole, folks! Just list them and you should hit it! Slick Having no adjustments, and presumably no 62 Ohm coax, you must have bent it into a V to get 50 Ohms. If you put a parasitic element on it, it is not a dipole. Tam/WB2TT |
"Tam/WB2TT" wrote in message ...
MFJ-259. Home-made dipole using aluminum tubing. There are only so many physical parameters of a dipole, folks! Just list them and you should hit it! Slick Having no adjustments, and presumably no 62 Ohm coax, you must have bent it into a V to get 50 Ohms. If you put a parasitic element on it, it is not a dipole. I didn't have to do that. It's a straight regular dipole. No parasitic either. s. |
Having no adjustments, and presumably no 62 Ohm coax, you must have bent
it into a V to get 50 Ohms. ================================ Having no record of who said what, or what the discussion was about, someone may be interested in little program INV_VEE which, amongst other things, demonstrates how the feedpoint impedance of an inverted-V dipole varies with the enclosed angle from 0 to 180 degrees for any height above ground. Download INV_VEE from website below. ---- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
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