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Aerial grounding and QRM pick-up: theory & practice
On Sat, 22 Sep 2007 19:18:24 -0700, art wrote:
Richard , I have been reviewing antenna fundamentals as per the engineering handbook by Jasik second edition where it states Equation (1-1) efficiency = power radiated by antenna / power accepted by antenna There is absolutely nothing stated here about "Gain" because radiation is in every direction. An antenna is a passive device, it cannot exhibit gain. Johnson and Jasik sez: "if one has a lossless antenna, the directivity and gain are identical." Equation (1-2): "The total power radiated from the antenna is" the measurement of radiation intensity in watts/sr in every direction from an antenna. Equation (1-4): "Directivity is the measure of the ability of an antenna to concentrate radiated power in a particular direction." which is a sub-portion of the total radiation. We can measure the total power of all radiation (EZNEC provides this); we can measure the power accepted by an antenna (EZNEC provides this); we can measure the power in a particular direction (EZNEC provides this). "The method of computing radiation patterns foir thin linear radiators is basic regardless of length or complexity of shape " There is for EVERY length. "if one assumes that the current from point to point is sinosoidal. "for the case of a thin half-wave radiator which can be assumed to have a sinusoidal current distribution" This statement is NOT about efficiency and it specifically recites what can be said about: 1. radiation patterns; 2. radiation resistance; 3. "gain" (directivity); 4. input Z. We, in this group, quite typically express ALL of these qualities for ANY antenna on the basis of SPECIFIC physical dimensions and frequency. When we do, there is barely a half dB variation in any answer, and often better when all SPECIFIC physical dimensions and frequency are provided by the claim maker. As you often fail to provide this SPECIFIC information, then your claims descend into the category of myth and superstition (you can call it hope and desire). What I am declaring is the tank circuit ala parallel circuit which demands a full wave length antenna is the most efficient because the assumption by mathematicians is incorrect. This is superstition. This Voodoo can be easily tested. The first part of equation (1-1) from the authors you quote demand you supply the SPECIFIC power accepted by an antenna. You also fail to supply the second part of equation (1-1) that states the SPECIFIC power radiated by the antenna. Voodoo = 100% So, to SPECIFIC counter proofs: A half wave antenna in free space: length = 33.43 feet wire diameter = #12 wire frequency = 14.28127 MHz input Z = 72.12 ąj0.00 Ohms Power accepted by antenna = 100W Power radiated by antenna = 100W Efficiency = 100% Absolutely same antenna in free space at its full wavelength frequency: length = 33.43 feet wire diameter = #12 wire frequency = 28.463975 MHz input Z = 4257 ąj0.00 Ohms Power accepted by antenna = 100W Power radiated by antenna = 100W Efficiency = 100% BOTH antennas exhibit radiation patterns IDENTICAL to Johnson and Jasik. BOTH antennas exhibit input Zs IDENTICAL to Johnson and Jasik. BOTH antennas exhibit radiation patterns IDENTICAL to Johnson and Jasik. BOTH antennas exhibit radiation resistances IDENTICAL to Johnson and Jasik. BOTH antennas exhibit radiation gain (directivity) IDENTICAL to Johnson and Jasik. When either of these two are off-center fed the efficiency DOES NOT CHANGE: Power accepted by antenna = 100W Power radiated by antenna = 100W Efficiency = 100% nobody knows how a fractional wavelength antenna really works Total ignorance reveals: Voodoo = 100% Equation (1-1) and (1-2) are for any size antenna. All of this stuff is in the FIRST TWO PAGES OF THE BOOK. On the very first page of "Fundamentals of Antennas" "If the current distribution on a wire is known ... then the radiation pattern and the radiated power can be computed." Marconi could measure current distribution 100 years ago. The authors, of course, give treatments for antennas of all sizes, otherwise the book would only be three pages long. Arthur, stop coloring the pages with your crayons long enough to try reading at least these three pages. :-0 73's Richard Clark, KB7QHC |
Aerial grounding and QRM pick-up: theory & practice
"Richard Clark" wrote ... On Sat, 22 Sep 2007 19:18:24 -0700, art wrote: Richard , I have been reviewing antenna fundamentals as per the engineering handbook by Jasik second edition where it states Equation (1-1) Massive snip of good stuff Arthur, stop coloring the pages with your crayons long enough to try reading at least these three pages. :-0 73's Richard Clark, KB7QHC Richard: I love to watch you tilt at windbags!!!! Mike W5CHR |
Aerial grounding and QRM pick-up: theory & practice
On Sep 23, 11:18 am, art wrote:
In comparing two antennas with similar omni direction radiation field I state that gain in the field is indicative of increased radiadion ... ....yes, but radiation only in limited az/el sectors, at the expense of loss of radiation in the other sectors. The field gain in a particular direction is due to the change in pattern shape, not an increased radiation efficiency of the "better" antenna. For the same input power accepted by different antennas, the total power radiated into the volume of space is the same, no matter what the shapes of their respective radiation envelopes. |
Aerial grounding and QRM pick-up: theory & practice
On 23 Sep, 11:45, "Jimmie D" wrote:
"Walter Maxwell" wrote in message ... On Sat, 22 Sep 2007 19:19:18 -0700, wrote: On Sep 22, 5:40 pm, art wrote: O.K. I may have muddied things. I hold to the fact that a one wavelength dipole will always radiate at a higher efficiency than a 1/2 wave dipole. If it does, I doubt it's enough to measure on the air.. The example I gave as for an instance was a quad versus a 1/2 wave dipole. This is readily seen by any operator empirically. I've never seen it here. For that reason, I hardly use loops. Neither vertically oriented, or horizontal as for NVIS use. I don't see them as worth the extra trouble. Being I tested them on 75m using NVIS paths, a noticable difference in efficiency should have been readily apparent. It wasn't. In fact, I usually has slightly better performance using the dipoles, which I think was due to the bulk of the max current portions of the antenna being higher above ground in general. The loop sagged a bit in areas, and wasn't all that high above ground. The more wire near the ground, the more ground loss in general. Mathematically it is proven that way also even tho both are in accordance to Maxwell's laws. Where is the math? You should find a very slight difference at best.. It's common knowledge that even a short piece of wire 1/10 of a wave long will radiate nearly all the power that is applied to it. You can go lots shorter than that if you want. If even a short piece of wire will radiate nearly all the power applied to it, what is the point on harping about some magical properties of a full wave length of wire? Art, you are starting to bark at the moon I'm afraid... I was going to comment on some of your other posts, but I think I'll spare you the increase in blood pressure. All I can say is that you are starting to wander off in mumbo jumbo land again.. Replacing known science with conjured mumbo jumbo is no way to live. MK Art, it distresses me to read the misleading statements you profess to be true in your posts. There is no difference in the 'efficiencies' between a full-wave and a half-wave dipole. Let's assume the wire size and conductivity of each dipole is such that we can say they both radiate 98 percent of the power delivered to them. Let's also say that the same amount of power is delivered to both dipoles. What now is the difference in the radiation between the two dipoles? The only difference is in the SHAPE of the radiation patterns--the full-wave dipole will have a somewhat narrower lobe in the direction broadside to the dipole than that of the half-wave dipole, therefore deriving slightly more gain IN THAT DIRECTION than that of the half-wave, but with less gain than the half-wave in all other directions. Consequently, the total integrated power in either radiation pattern will be exactly the same!!! If you want to express the mathematics of the conditions I described here according to J.C.Maxwell's equations, you will find that Maxwell's equations fit the conditions EXACTLY. Walt, W2DU If any difference at all exist it is that the full wave antenna would be ever so slightly less efficient due to the ohmic losses of the extra wire. Jimmie- Hide quoted text - - Show quoted text - Give me the proof not a opinion when there are so many . Art KB9MZ |
Aerial grounding and QRM pick-up: theory & practice
On 23 Sep, 12:02, "Dave" wrote:
"Jimmie D" wrote in message ... "Walter Maxwell" wrote in message .. . On Sat, 22 Sep 2007 19:19:18 -0700, wrote: On Sep 22, 5:40 pm, art wrote: O.K. I may have muddied things. I hold to the fact that a one wavelength dipole will always radiate at a higher efficiency than a 1/2 wave dipole. If it does, I doubt it's enough to measure on the air.. The example I gave as for an instance was a quad versus a 1/2 wave dipole. This is readily seen by any operator empirically. I've never seen it here. For that reason, I hardly use loops. Neither vertically oriented, or horizontal as for NVIS use. I don't see them as worth the extra trouble. Being I tested them on 75m using NVIS paths, a noticable difference in efficiency should have been readily apparent. It wasn't. In fact, I usually has slightly better performance using the dipoles, which I think was due to the bulk of the max current portions of the antenna being higher above ground in general. The loop sagged a bit in areas, and wasn't all that high above ground. The more wire near the ground, the more ground loss in general. Mathematically it is proven that way also even tho both are in accordance to Maxwell's laws. Where is the math? You should find a very slight difference at best.. It's common knowledge that even a short piece of wire 1/10 of a wave long will radiate nearly all the power that is applied to it. You can go lots shorter than that if you want. If even a short piece of wire will radiate nearly all the power applied to it, what is the point on harping about some magical properties of a full wave length of wire? Art, you are starting to bark at the moon I'm afraid... I was going to comment on some of your other posts, but I think I'll spare you the increase in blood pressure. All I can say is that you are starting to wander off in mumbo jumbo land again.. Replacing known science with conjured mumbo jumbo is no way to live. MK Art, it distresses me to read the misleading statements you profess to be true in your posts. There is no difference in the 'efficiencies' between a full-wave and a half-wave dipole. Let's assume the wire size and conductivity of each dipole is such that we can say they both radiate 98 percent of the power delivered to them. Let's also say that the same amount of power is delivered to both dipoles. What now is the difference in the radiation between the two dipoles? The only difference is in the SHAPE of the radiation patterns--the full-wave dipole will have a somewhat narrower lobe in the direction broadside to the dipole than that of the half-wave dipole, therefore deriving slightly more gain IN THAT DIRECTION than that of the half-wave, but with less gain than the half-wave in all other directions. Consequently, the total integrated power in either radiation pattern will be exactly the same!!! If you want to express the mathematics of the conditions I described here according to J.C.Maxwell's equations, you will find that Maxwell's equations fit the conditions EXACTLY. Walt, W2DU If any difference at all exist it is that the full wave antenna would be ever so slightly less efficient due to the ohmic losses of the extra wire. Jimmie don't claim that until you have modeled it in full. it "may" What does "may" infere? Is it it 'may' or 'may not' or 'I am not sure' or 'I don't know'? I am not willing to procede with what you say unless you can be more difinitive. What does a house built on sand do? snip ragards Art KB9MZ....XG |
Aerial grounding and QRM pick-up: theory & practice
Jimmie D wrote:
On 23 Sep, 12:02, "Dave" wrote: don't claim that until you have modeled it in full. it "may" Who said "may", not me Jimmie The attributions indicate that Dave said "may". -- 73, Cecil http://www.w5dxp.com |
Aerial grounding and QRM pick-up: theory & practice
I am sorry to read this. I had hoped I had stumbled upon a perpetual motion
machine. "Jimmie D" wrote in message ... [snip] No that is the point. An antenna can radiate no more energy than you put into it. If you do something to increase the field intensity in one direction the field intensity must decrease in other directions. Nothing to debate, it is a proven fact. A fact you will never accept because if you do you will also have to accept the your guassian antenna is just a delusion. It is a real shame that you have chosen a knowledge of antennas to be such an important measuring stick for the value of your existence. |
Aerial grounding and QRM pick-up: theory & practice
John, N9JG wrote:
I am sorry to read this. I had hoped I had stumbled upon a perpetual motion machine. Keep the faith baby! You just might have, he http://www.dailymail.co.uk/pages/liv...page_id=19 65 Regards, JS |
Aerial grounding and QRM pick-up: theory & practice
On Sep 24, 7:16 pm, "Jimmie D" wrote:
"art" wrote in message ups.com... On 23 Sep, 07:29, "Jimmie D" wrote: "art" wrote in message roups.com... On 22 Sep, 07:22, "Richard Fry" wrote: "art" wrote The most efficient radiator is one wave length long where it is considered to be in equilibrium with a parallel electrical cuircuit. For most efficient radiation both the capacitance and the inductance must act as a energy storage such that when the terminals are shorted the energy is released in a burst such that radiation can begin. ... In the case of a fractional wave length radiator the pendulum type radiation is not available for radiation ___________ Note (for one example of many) that in an antenna system consisting of a 1/2-wave, center-fed dipole driven by a matched, balanced transmission line, the dipole itself radiates virtually all of the r-f energy present at the antenna feedpoint. The radiation efficiency of a system as in the above example, but using a full wave dipole is no better than the 1/2-wave version, other things equal. The full wave version just has a different radiation pattern. RF I don't know what your credentials are for you to make such a statement but it is a free world after all! A quad radiator is a wave length radiator with a gain more than a half wave as one sample. Computor programing confirmes more radiation from full wave antennas and mathematics according to Maxwell,s rules substantiate it. I can understand not believing computor programs but I am very interested in any mathematical data that would support your stand which is contrary to the mathematics that I and others support. What you are stating is that an attena in a series cuircit format produces the same radiation as a parallel or tank cuircuit. I am more than eager to read the contrary mathematical proof that is contrary to the mathematics that I hold true. You may have hit on the true explaqnation of radiation which Einstein, Planck and many others went to their grave without solving it Regards Art KB9MZ.....XG I dont know his credentials either but Richard is absolutly correct. Efficency is the ability to radiate the signal and not turn it into infra-red energy and has nothing to do with gain. The Math: Efficiency = (power applied to the antenna system - power turned into heat by the antenna system)/power applied to the antenna system. Doesnt take a computer, doesnt take Maxwell or Einstien to explain. 5th grade math works pretty well in this case. The best thing the OP can do for his existing antenna is install a good ground system and impedance matching networks, antenna tuner. If I were really serious about it I would invest in an antenna analyzer so I would know when my antenna is tuned for optimum match to my radio and log the settings of my tuner. With the ground system and antenna type he has I am sure the ground resistance is soaking up most of his signal. He would surely benifit from improving his ground system. Jimmie- Hide quoted text - - Show quoted text - In comparing two antennas with similar omni direction radiation field I state that gain in the field is indicative of increased radiadion but that is a side issue brought up as often is in this newsgroup in tha absence of a point by point debate. No that is the point. An antenna can radiate no more energy than you put into it. If you do something to increase the field intensity in one direction the field intensity must decrease in other directions. Nothing to debate, it is a proven fact. A fact you will never accept because if you do you will also have to accept the your guassian antenna is just a delusion. If you look at the field of a antenna that isr radiating an equal amount in all direction the volume of the radiation consists of usefull energy in the form of radiation. If another antenna with the same energy input provides a radiation field in all directions that is equal but at a larger radius than the prior antenna field the the latter antenna has gain over the prior antenna. If you compare any fractional ground mounted antenna with a full wave antenna the radius of the field willhave a difference of aprox 3 db and the resistive impedance will have a ratio of two to one.Note that gain is a measure of one radiator level against another and is no way a distorted field of radiation that has been manipulated by an additional near by radiator. A ground plane does nothing more than balancing the circuit provided such that current does not meander back thru the feed line and a ground plane is only necessary for a fractional wavelength circuit to balance the circuit as a whole. It eats up energy that would normally provide radiation in a circuit such as a full wave radiator. Without a good ground plane the impedance to a fractional wave length is difficult and usually not efficient and a lot less than that of a radiator that does have a good ground plane which is around30 ohms resistive which is 1/2 of the resistive impedance of a full wave radiator. As far as the Gaussian antenna it is not an illusion to those with an engineering background. For those without an engineering background to enable them to follow the logic do not have the know how to discredit anything and certainly can not measure the quality of life of those with understanding. If you cannot follow the science of antennas then you are doomed to be a follower, never a leader. and certainly not a judge. I'm gone for a month or so and will not be using this newsgroup during that time. Will be back in the fall Art It is a real shame that you have chosen a knowledge of antennas to be such an important measuring stick for the value of your existence. Jimmie Jimmie |
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