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skin depth decay
Roy Lewallen wrote:
"OK, I give up. I`ve got a dipole in free space. I connect one end of the load resistance to one end of the dipole. What do I connect the other end of the resistor to?" Great question. You connect it to the inobtrusive convenient perfect earth connection immediately present at the end of the terminating resistor. Since this is likely impossible, you merely define you have done the deed and calculate the results. Best regards, Richard Harrison, KB5WZI |
skin depth decay
On Tue, 20 Nov 2007 21:38:55 -0800, Roy Lewallen
wrote: If that's too tough, how about just a dipole a quarter wavelength above ground? Hi Roy, Hmmm, too tough. The math is all pretty ordinary and well within your capacity to examine in your own copy of the book. So I won't belabor others with that. However, as others do not have a copy, they might appreciate some other benchmarks: End Fed Half-Wave 600 Ohms which, of course, suffers the same question; Folded Quarter-Wave Dipole 260 Ohms there, a resistor might comfortable be applied, but I don't know as I have not tried it; yet and all, this is drawn from the same ordinary math; Folded Half-Wave Dipole 500 Ohms same observation as with the Quarter-Wave and falling nearly on twice the rating too - a coincidence of the math no doubt; (But I believe there is a commercial variant of this that is popular with the MARS group exactly for the reasons of not presenting SWR.) Continuous Wire Array 300 Ohms an oddity in the pantheon of styles, yet it too seems suitable to resistive termination for testing "Surge Impedance;" Rhombic Antenna 600 Ohms here's one that is more familiar to all, and with the added bonus that it is typically loaded with a resistor to exactly fulfill the definition of "Surge Impedance" whose ordinary math dovetails with experience. But, Roy, I do recognize the terms "Surge Impedance" maybe a language barrier with you as it certainly qualifies as an archaic term. Reggie loved to carry this water and in spite of differences, his treatments quite often got him results that were good first approximations, and sometimes better. If you really seek closure, I would suggest you could mine your own copy of this reference for errors. As for its practical importance - well, let's just say that this board would support only 2% of the current traffic if it came to that. 73's Richard Clark, KB7QHC |
skin depth decay
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skin depth decay (TDR)
"Cecil Moore" wrote
If there is not a Z0-match to the feedline at the feedpoint, some of the antenna current reflected from the open end of the antenna leaks back into the feedline and makes it's way back to the source. A TDR will register reflections both from the feedpoint and the open ends of the antenna. _________________ Not that this changes the essential point Cecil writes about, but... The waveform transitions of most TDRs have bandwidths far greater than the matched bandwidths of typical antennas, so the antenna system would produce a reflection of the TDR pulse even _with_ a Zo match to the feedline at/near the design frequency of the antenna. For that reason a TDR is a relatively useless means to measure the performance of an antenna, unless the bandwidth of the pulse is contained within the matched bandwidth of the antenna, and that pulse is modulated on an r-f carrier in the spectrum that the antenna is intended to radiate well. The link below leads to an accurate measurement of a broadcast TV transmit antenna system I made some 35 years ago, using this approach. This system used about 1,550 feet of 6-1/8" OD, 75 ohm coaxial transmission line. This measurement might also interest those who think that discrete reflections do not exist inside a transmission line. http://i62.photobucket.com/albums/h8...easurement.gif RF |
skin depth decay
Richard Harrison wrote:
Roy Lewallen wrote: "OK, I give up. I`ve got a dipole in free space. I connect one end of the load resistance to one end of the dipole. What do I connect the other end of the resistor to?" Great question. You connect it to the inobtrusive convenient perfect earth connection immediately present at the end of the terminating resistor. Since this is likely impossible, you merely define you have done the deed and calculate the results. Another way to mentally view the surge impedance is with an infinitely long wire for the dipole. It changes the dipole from a standing-wave antenna into a traveling- wave antenna. The ratio of V to I is constant and equal to the characteristic (surge) impedance of the antenna. Reg claimed the feedpoint (surge) impedance for an infinite dipole would be about 1200 ohms, i.e. ~600 ohms in each direction which roughly agrees with the formula 138*log(4D/d). -- 73, Cecil http://www.w5dxp.com |
skin depth decay
On 20 Nov, 21:54, (Richard Harrison) wrote:
Art wrote: "How many pages soes that book of Bailey`s have?" 595 and each one is valuable. Best regards, Richard Harrison, KB5WZI Just bought it for $1.99 plus shipping on E Bay Art |
skin depth decay
On 20 Nov, 21:48, (Richard Harrison) wrote:
Art wrote: "Oh Richard, you may deny my antenna but that is what I was alluding to. Again it is the LC ratio that must be kept for resonance." I don`t know enough about Art`s antenna to deny it. I do know that resonance depends on the reciprocal of the sq. rt. of the product of LC, not its quotient. Explosive results from an inductor were introduced by Kettering, I believe, through interruption of battery current through an inductor to generate a very high voltage spark to ignite the fuel air mixture within the cylinder of an internal combustion engine for automobiles. Just as I doubt the inclusion of a pendulum in Art`s antenna, I also doubt the presence of an interruptor to discharge either the capacitance or inductance in the resonant antenna. If Art`s antenna is novel, useful, and not completely obvious from prior knowlege, he may profit from it. I wish him all the best. Best regards, Richard Harrison, KB5WZI Richard, You just have to familierise yourself with what ia termed a TANK circuit When you do this all becomes clear.Since it is used in transmitters it may well be included in ARRL publications. On the other hand "Google" the circuit. My guess is that it in the older books of Terman where if you see a chapter on spark transmitters it will appear in there. Another good place to look would be Bailey's book with reference to a flyback transformer. This is a very important area to hone your antenna skills. Side note. I am not interested in profit. Regards Art |
skin depth decay
Art wrote:
"Hust bought it for $1.99 plus shipping!" Outstanding! I`ll wager you enjoy it as much as I do.. Data sheets for many common antennas are very nice. They all have dimensions for 200 MHz but scale for any frequency. Gains are versus a 1/2-wave dipole. Bailey published "TV and Other Receiving Antennas" in 1950 to "to give usable information which in many cases is based on the author`s experience and has not been published before." Bailey lists himself simply as a consulting engineer. Best regards, Richard Harrison, KB5WZI |
skin depth decay
Art wrote:
"I am not interested in profit." Conglomerate I worked for acquired Newport News Shipbuilding and Drydock Company. They had their mission statement on a sign in front of their headquarters. It read something like: "Our goal is to build fine ships, for a profit if possible." That sign had to go immediately. Our company was in business for profit which we expected as a consequence of product, price, and service, even when building nuclear submarines for the U.S. Navy. Profit is good. Profit makes the world turn sanely. Best regards, Richard Harrison, KB5WZI |
skin depth decay
Art wrote:
"How many pages soes that book of Bailey`s have?" 595 and each one is valuable. If I ever get a gob of spare time, I might run my copy through a scanner and give it the same conversion I did a couple of years ago for Laport's "Radio Antenna Engineering". If somebody wants to help out and do some/all of the scanning of their own copy, and send me the files for conversion and processing, it'd be much appreciated - drop me a note. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
skin depth decay
Richard Clark, KB7QHC wrote:
"Heinrich Hertz might have something to discuss with you about his experiments." Anyone should be so honored! Heinrich Rudolph Hertz (1857-1894) was a pioneer experimental investigator of electromagnetic (EM or radio) waves, according to B. Whitfield Griffith in "Radio-Electronic Transmission Fundamentals'. Hertz in 1887, eight years after the death of J.C. Maxwell (the predictor of EM waves) proved Maxwell correct. Hertz did so by generating the first man-made EM waves in his laboratory. I believe the Hertz antennas consisted of loops which did not depend on presence of ground for operation. Hertz was able to create a severe electrical disturbance in one loop and across a gap in the second loop a spark would jump. Hertzian radio waves are said to lie between 10 kHz and 30,000 GHz, and probably include the range of Art`s antenna. A Hertz antenna is said to have its resonant frequency determined by its distributed capacitance which varies according to its physical length. Best regards, Richard Harrison, KB5WZI |
Thanksgiving
Richard Harrison wrote:
Jim Kelley supplied the URL of Lincoln`s Thanksgiving Day proclamation during the American Civil War. It goes back much before Lincoln. If only President Lincoln had known. He could have saved himself the trouble of proclaiming it. Maybe he would have called it Turkey Day instead - like I do. :-) 73 de jk |
skin depth decay
On 21 Nov, 12:31, (Richard Harrison) wrote:
Richard Clark, KB7QHC wrote: "Heinrich Hertz might have something to discuss with you about his experiments." Anyone should be so honored! Heinrich Rudolph Hertz (1857-1894) was a pioneer experimental investigator of electromagnetic (EM or radio) waves, according to B. Whitfield Griffith in "Radio-Electronic Transmission Fundamentals'. Hertz in 1887, eight years after the death of J.C. Maxwell (the predictor of EM waves) proved Maxwell correct. Hertz did so by generating the first man-made EM waves in his laboratory. I believe the Hertz antennas consisted of loops which did not depend on presence of ground for operation. Hertz was able to create a severe electrical disturbance in one loop and across a gap in the second loop a spark would jump. Hertzian radio waves are said to lie between 10 kHz and 30,000 GHz, and probably include the range of Art`s antenna. Yes it does. But it is only half of the story since it basically is missing half of the circuit which the spark was looking for . As you know a requirement is to keep the LC ratio, so basically he had a tesla coil which is the opposite and was looking for the capacitor When you have both of these THEN you have the "circulating" current which creats full radiation.This circulating current is ofcourse in the form of pulses at twice per period where the spark is one of them that is uncontrolled with respect to the frequency of the circuit It is indicative of the time constant involved which is also a requirement of radiation Close but no cigar. A Hertz antenna is said to have its resonant frequency determined by its distributed capacitance which varies according to its physical length. I would argue with that based on the LC ratio for present day radiators but for Hertz it would be correct since his radiator did not have the inductive storage of energy which was dissipated in a spark and not returned to the capacitor. .. Best regards, Richard Harrison, KB5WZI Best regards Art Unwin ...KB9MZ...xg (uk) |
skin depth decay
Richard Harrison wrote:
Cecil, W5DXP wrote: "A TDR will register reflections both from the feedpoint and the open ends of the antennas." Why reflections from the feedpoint if the antenna matches the feedline? A traditional TDR sends a fast rising step or narrow pulse. The condition for no reflection is that the load impedance equal the line impedance over at least the bandwidth of the energy in the step or pulse. Depending on the TDR system, this could be well into the tens of GHz. Even a very broadband antenna doesn't meet this requirement at the feedpoint, so a reflection will occur. Long ago I looked at a small dipole with a TDR system, and I've seen the same result published several times since. What you see resembles a damped square wave, the general square wave shape being due to multiple reflections from the ends and feedpoint, and the damping due to radiation. The top of each "cycle" of the square wave rises, however, because the impedance of the transmission line formed by the two dipole halves increases in impedance from the center to the ends. Roy Lewallen, W7EL |
skin depth decay
Roy Lewallen, W7EL wrote:
"A traditional TDR sends a fast rising step or narrow pulse. The condition for no reflection is that the load impedance equal the line impedance over at least the bandwidth of the energy in the step or pulse." Explanation from the expert makes it crystal clear. Thank you. Best regards, Richard Harrison, KB5WZI |
skin depth decay
On Wed, 21 Nov 2007 14:17:42 -0800 (PST), art
wrote: Yes it does. But it is only half of the story since it basically is missing half of the circuit which the spark was looking for . As you know a requirement is to keep the LC ratio, so basically he had a tesla coil which is the opposite and was looking for the capacitor Hi Arthur, You really should read some history before re-writing it. Hertz' antenna was a single turn of wire (as was the receiver's). If you cannot figure out how Hertz' antenna resonance was achieved (let me drop the shoe here, and say "in the conventional way"), then you are more than 120 years behind in the game. It really has all been done before. Books have been written about it, several movies too, and perhaps a segment on the Discovery Channel. 73's Richard Clark, KB7QHC |
skin depth decay
On 21 Nov, 19:26, Richard Clark wrote:
On Wed, 21 Nov 2007 14:17:42 -0800 (PST), art wrote: Yes it does. But it is only half of the story since it basically is missing half of the circuit which the spark was looking for . As you know a requirement is to keep the LC ratio, so basically he had a tesla coil which is the opposite and was looking for the capacitor Hi Arthur, You really should read some history before re-writing it. Hertz' antenna was a single turn of wire (as was the receiver's). If you cannot figure out how Hertz' antenna resonance was achieved (let me drop the shoe here, and say "in the conventional way"), then you are more than 120 years behind in the game. It really has all been done before. Books have been written about it, several movies too, and perhaps a segment on the Discovery Channel. 73's Richard Clark, KB7QHC For more than a year you have stated "it" has been done before and none of us know what "it" is. Thus your posts have no meaning to anybody and is why they are seen as not worth while persueing. You are so cryptic that you fool yourself as well as wasting other peoples time. is |
skin depth decay
On Wed, 21 Nov 2007 19:57:57 -0800 (PST), art
wrote: For more than a year you have stated "it" has been done before and none of us know what "it" is. US? You got a mouse in your pocket? Is his name Mickey Gauss? 73's Richard Clark, KB7QHC |
skin depth decay
On 26 Nov, 01:33, "Jimmie D" wrote:
"Richard Clark" wrote in message ... On Wed, 21 Nov 2007 19:57:57 -0800 (PST), art wrote: For more than a year you have stated "it" has been done before and none of us know what "it" is. US? You got a mouse in your pocket? Is his name Mickey Gauss? 73's Richard Clark, KB7QHC In a way I can feel Arts's pain. When I was 13 I thought I had discovered a new way of rectifying AC, too bad the bridge rectifier had already been invented. I was crushed. Jimmie. No. That is just Richard playing word games with his "it" just like Clinton with "is" I say I have invented a 160M antenna that is rotatable and directional and without the requirement of a ground plain. It could have been for a different frequency but I chose the worst case scenario. No, you will have to wait for the PTO to print it before you can duplicate it Now Richard with his word games is playing with the word "it". And he knows full well that hams are not using this antenna design at the present time. The day will come when he has to state what "it" is but rest assured it will not be the rotatable 160 M antenna.It took him and David several months to even acknowledge that you can add a time variable to static law. Now they both insinuate that they knew that all along. In a few more months Richard will conjure up something that fits his present posture. Until then it is word games that insinuate but does not actually state thus his befuddled postings that few understand. Art |
skin depth decay
On Mon, 26 Nov 2007 06:27:22 -0800 (PST), art
wrote: I say I have invented a 160M antenna that is rotatable and directional and without the requirement of a ground plain. Hi Arthur, "It" is called a dipole. 'It" has already been done. There have been extrememly long threads here for weeks discussing this design: Rotatable 200M antennas that are half a meter wide! These rotatable and directional designs have been around since the days of Queen Victoria. It could have been for a different frequency but I chose the worst case scenario. Others figured out how to do "it" too. One of the first was some bumpkin called Hertz. You probably haven't read about him in a book unfortunately. 73's Richard Clark, KB7QHC |
skin depth decay
Richard Clark wrote:
"It" is called a dipole. 'It" has already been done. There have been extrememly long threads here for weeks discussing this design: Rotatable 200M antennas that are half a meter wide! According to the following IEEE paper: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf A 75m 6" dia. 4 tpi Texas Bugcatcher coil has a VF of around 0.024 on 1.9 MHz. A self-resonant 160m dipole made from such coil stock would be only about 6 feet long. -- 73, Cecil http://www.w5dxp.com |
skin depth decay
On 26 Nov, 08:55, Cecil Moore wrote:
Richard Clark wrote: "It" is called a dipole. 'It" has already been done. There have been extrememly long threads here for weeks discussing this design: Rotatable 200M antennas that are half a meter wide! According to the following IEEE paper: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf A 75m 6" dia. 4 tpi Texas Bugcatcher coil has a VF of around 0.024 on 1.9 MHz. A self-resonant 160m dipole made from such coil stock would be only about 6 feet long. -- 73, Cecil http://www.w5dxp.com That may be true Cecil but it is a lousy antenna. The conclusion of the article infers that lumped loads can be equated to distributed loads which we all know is an error. One of the requirements for radiation is that the radiators surface is not enclosed. A lumped load does not accomplish that.Usually when Richard posts on a thread it is usually a death knell for any further communication. With you replying to him in some way this thread may stay alive for a while. You will notice that he did not identify "it" that apparently was used before Marconi came along.He also talks of long discussion of this "dipole" of Queen Victoria which as you know is a figment of his imagination.A replacement for it. He is just a childish idiot looking for some sort of recognition who cannot communicate. |
skin depth decay
On Mon, 26 Nov 2007 10:47:36 -0800 (PST), art
wrote: On 26 Nov, 08:55, Cecil Moore wrote: Richard Clark wrote: "It" is called a dipole. 'It" has already been done. he did not identify "it" that apparently was used before Marconi came along.He also talks of long discussion of this "dipole" of Queen Victoria which as you know is a figment of his imagination. Hi Arthur, We can all appreciate how you rejected all things British when you emigrated. Consult history to observe that Hertz (not a British subject) invented the loop antenna during Victoria's reign. Others may be equally ignorant of early RF work, but it was a simple google of "Hertz" and "Queen Victoria" to arrive at: "Marconi was giving wireless reports to the mainland from the Kingstown Regatta, from distances of 5 to 10 miles out to sea. And sending Queen Victoria reports concerning the health of her son, the Prince of Wales, who was recovering from a knee injury as he watched the regatta from the royal yacht." And, as we are all well aware, Hertz did not design, build, and operate his antenna after the reign of Victoria. This is all very elemental stuff. 73's Richard Clark, KB7QHC |
skin depth decay
On 26 Nov, 11:19, Richard Clark wrote:
On Mon, 26 Nov 2007 10:47:36 -0800 (PST), art wrote: On 26 Nov, 08:55, Cecil Moore wrote: Richard Clark wrote: "It" is called a dipole. 'It" has already been done. he did not identify "it" that apparently was used before Marconi came along.He also talks of long discussion of this "dipole" of Queen Victoria which as you know is a figment of his imagination. Hi Arthur, We can all appreciate how you rejected all things British when you emigrated. Consult history to observe that Hertz (not a British subject) invented the loop antenna during Victoria's reign. Others may be equally ignorant of early RF work, but it was a simple google of "Hertz" and "Queen Victoria" to arrive at: "Marconi was giving wireless reports to the mainland from the Kingstown Regatta, from distances of 5 to 10 miles out to sea. And sending Queen Victoria reports concerning the health of her son, the Prince of Wales, who was recovering from a knee injury as he watched the regatta from the royal yacht." And, as we are all well aware, Hertz did not design, build, and operate his antenna after the reign of Victoria. This is all very elemental stuff. 73's Richard Clark, KB7QHC And this is ........"it"? An antenna for........ 160M? The antenna you state that has been talked about at length somewhere on this newsgroup at a yet unknown location? I will have no problem with the PTO since your fiction does not persuede them in any way.From the getgo you have stated that my antenna is pre known when for months you would not acknowledge that a time variable could not be added to static law. A fact that you now readily admit. All elemental stuff that defies description of any sort and which exists only in your twisted mind which you refuse to describe. You have to much faith that "all is known" and a equivalent antenna will pop out of the fog that you generate. End of discussion. You have nothing new to add to keep my attention. I can see now why they tried to lose your patent aplication some years ago. The question arises is the examiner who "found it" is still employed. |
skin depth decay
On Mon, 26 Nov 2007 13:03:46 -0800 (PST), art
wrote: On 26 Nov, 11:19, Richard Clark wrote: On Mon, 26 Nov 2007 10:47:36 -0800 (PST), art wrote: On 26 Nov, 08:55, Cecil Moore wrote: Richard Clark wrote: "It" is called a dipole. 'It" has already been done. he did not identify "it" that apparently was used before Marconi came along.He also talks of long discussion of this "dipole" of Queen Victoria which as you know is a figment of his imagination. Hi Arthur, We can all appreciate how you rejected all things British when you emigrated. Consult history to observe that Hertz (not a British subject) invented the loop antenna during Victoria's reign. Others may be equally ignorant of early RF work, but it was a simple google of "Hertz" and "Queen Victoria" to arrive at: "Marconi was giving wireless reports to the mainland from the Kingstown Regatta, from distances of 5 to 10 miles out to sea. And sending Queen Victoria reports concerning the health of her son, the Prince of Wales, who was recovering from a knee injury as he watched the regatta from the royal yacht." And, as we are all well aware, Hertz did not design, build, and operate his antenna after the reign of Victoria. This is all very elemental stuff. 73's Richard Clark, KB7QHC And this is ........"it"? Hi Arthur, Since you've gone away, the Brits speak a more Americanized form of English that is commonly expressed right here in these postings. "It" being one of those difficult words is not our problem so much as yours. Consult a dictionary you feel comfortable with. An antenna for........ 160M? Hertz, Marconi and the rest would have considered that shortwave and scaled down. The operative word here is "scaled." There is nothing new about an antenna coming in different sizes. The antenna you state that has been talked about at length somewhere on this newsgroup at a yet unknown location? I will admit that your indifference to antenna discussion in other threads contributes to your suffering from the illusion of having something novel - seeing you have such a difficult time describing it here. I will have no problem with the PTO They don't have to sell it to anyone! However, I do appreciate you are still reading my missives. :-) 73's Richard Clark, KB7QHC |
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