|
Good for you Cecil. Brevity and to the point is so much better than a
personal monologue about unrelated subjects that one would expect from a drunk . Regards Art. "Cecil Moore" wrote in message ... Richard Harrison wrote: Art, KB9MZ wrote: "The dipole is a very inefficient radiator." I seem to remember Kraus saying 95% efficiency was not unusual as a dipole efficiency. I don't think that's the efficiency that Art is talking about. Art's efficiency seems to be defined as the power delivered to the receiver divided by the power sourced by the transmitter. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Someone sed: "I don't think
there's any structure to this sub-category, other than to require at least one mention of Maxwell in every discussion". ====================== I'm a Folgers man myself! Never did like Starbuck's. 73 de Jack, K9CUN |
Howdy,
I have always heard that what we call "Ohm's Law" is actually Cavendish's Law. But as the story goes, Cavendish didn't write a paper. Is this BS or true? Jack, K9CUN |
Hi Richard, TOP and internal posting...sorry folks.
I think you are learned on this subject and won't quibble about what really happens in the real world. I think you know and I claim that I know. I will, however pick a little bone in regards to the answer which I posted to an email since I also thought would help others at a similar level of understanding or confusion. Oh geeze! here he goes...you had to set him off.. Here's my mantra and why a I am a little miffed by (but actually understand) frequent attempts to correct my explanations. The words we use and the depth to which we go at any given point to describe things, have an effect on the ability of people to absorb the concepts. As an instructor of basics, I have worked very hard, for a long time, to understand and use effective ways to transfer an understanding of electronic principles to students at what might be considered the lower rungs of the technical ladder...the beginners...the hams also. There is what I'll call an "instructor's high" associated with the light bulb going on in a student. It's really cool. I carefully craft my responses to the apparent level of knowledge of the questioner. I do my best to form a coherent story which progresses from simple, where a concept needed to understand more complex concepts is explained first, without adding the unnecessary complications of true, but potentially confusing facts, to the more complex goal I perceive to be the questioner's goal. Once the basic concepts sinks in AND the student is ready for the next level, usually by a response, I then proceed to build. It is the old "speak to your audience" concept. I don't dispute that your explanations are correct. They appear very good, rather complete. I do believe however, that your most assuredly honest and well meaning attempt to be correct, completely correct, actually makes the subject more confusing to the beginner. I believe this because I have been there. In fact, I must, almost every class session, throttle myself from doing just the very same thing. Why? Because when I do, I have succeeded in causing more confusion, resulting in a mental block to learning which requires much more effort at damage control to erase the mental blockage I created with my ignorant desire to be completely correct. Please understand that I am being harsh on *myself* because I have been frustrated by this and work hard to keep it under control. As an Engineer, teaching technician students, one must keep in mind that there is a different state of mind and ability to absorb what to them, appears a very complex subject...but to my arrogant mind is really very simple. After all, piecewise parametric polynomial interpolation looked like an impossible concept, way beyond my comprehension back in 92 when I first saw reference to it. Now, it looks like the simplest thing any high school Algebra student can understand. I'm also at a point in my life that I have seen and done so much in this field (and it all seems so simple) that I wish to return some of it to others, and I wish to do it very effectively. Of course, now you're going to tell me that you also have been teaching for x years and your methods are equally successful...so be it. There needs to me more of us. BTW...what is your line, Richard? Some comments, corrections and whatever stuck my fancy about what you wrote... "Richard Harrison" wrote in message ... Steve Nosko wrote: "Apparently, because of the way the big bang occurred, when we put a voltage across a resistor current flows in a manner that we discovered follows the equation called Ohm`s law." Big bang? Ohm wasn`t around then. He lived 1787 to 1854. Ohm discovered that current in an electrical resistance is proportional to voltage. The concept I was trying to relate in a slightly 'light' manner was: The stuff that happens, happens 'cuz of what we call "physics", "physical laws" or "nature" or sump-in' like that, not because there is an equation making it happen. Resistors don't know Ohm's law and don't conduct current because of Ohm or his discoveries. The equation we call Ohm's law is simply a model of how reality works. Like a model airplane, which helps us understand what a real airplane looks like. Ohms law, and all the other equations, help us understand what real electronics "looks like". Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. A completely valid way to word it, but to a beginner I think the phrase "locked in step " is vague. It would be a good start, but probably needs expansion to explain what it means. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. I wouldn't have worded it that way, but it (resistor is the type of resistance) is a valid model to have in mind. That is, as a way to distinguish it from "a resistance which is not a resistor". This made me think of how I think of it.. and when I use the word "resistance" I think of it as as a resistor, yet an impedance has a real or "resistive" part. That word "resistance" for me conotes a "resistor" where the others conote the other concept. Interesting nomenclature, that's all. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, Well, here's where I'll say that I think this is truly a matter of symantics. Your terminlolgy implies that dissipation = heat. I agree that the most common usage it that "... is dissipated as heat...". However, this next bit: ...is in-phase with current through the resistance, but it does not cause energy loss. I think has a symantics problem. I'm sure you truly understand what happens, but the words "...does not cause energy loss." isn't correct, because the energy IS lost from the circuit. The circuit "can't tell" the difference 'tween the resistor and any other kind of resistive component. It just may or may not be as heat, right? You know what happens and I know what happens, but the OP didn't, so I was starting him down a path that wouldn't paint him into a corner of not being able to understand the other resistive types of things later...if so desired. An example of lossless resistance is the Zo or surge impedance of a transmission line. Again, the power IS lost from the source, no? I think this an important basic understanding. To the sourse, it is gone. Poof! never to be seen again. I think it is a good model to understand and helps go further without Maxwell complicating things. I think you can go pretty far without Maxwell (gee, twice in one paragraph) and still have a good amount of (correct) sixth sense about what is going on in electronics and transmission lines. Zo is ... yet converts no energy to heat in the lossless line. And my model didn't exclude this. I thought I was explicit about that without bringing in more complexity for the OP. "radiation resistance". ...is hardly a loss. Again, as far as the transmitter circuitry is concerned, it is. The following is a well done explanation which goes further and into more detail...with one disagreement. An ohm is the unit of resistance. It is defined at 0-degrees C, of a uniform column of mercury 106.300 cm long and weighing 14.451 grams. One ohm is the resistance which drops one voltt when a current of one amp is passed through it. Reactances are also defined by their volts to amps ratios (ohms). The big difference is that reactance does no work and produces no heat. Opposition to electrical current comes from delay required to store ard retrieve energy to and from fields in and around the reactances. Current lags the applied voltage in an inductance. At time = 0, no current flows into an inductance, but rises exponentially from the instant of initial energization. Current leads the applied voltage into a capacitance. At time = 0, full current flows into a capacitance but voltage across the capacitance is zero and rises exponentially from the instant of initial energization. In an a-c circuit, the current through an inductance lags the voltage by 90-degrees. In a a-c circuit, the current through a capacitance leads the voltage by 90-degrees. Phase shifts are produced by energy storage in reactance. There is no phase shift in a resistance. No electrical energy is stored in a resistor, but its matter does have a thermal capacity. Once its atoms are agitated by heat their inertia is evident in the resistance`s temperature. It takes time to cool. Steve wrote: "Things get all messed up." As old Carson Robinson sang: "Life gets tedious, Don`t it?" Steve gave the formulas for capacitive and inductive reactances. They have always seemed convenient to me. Steve says: "---we call this new kind of (corrupted) resistance "Impedance"." No. Impedance is the general name for opposition to electricity. No. In the context of my writing for someone who has an unserstanding of DC and resistance, reactance it a very confusing factor. It corrupts an otherwise simple world. Getting into Vector Algebra and phasors is a significant step up in mathematics for the beginner not inclined to go the Engineering route. What I'm saying is that although the unified field theory may very well be the absolutely correct explanation of everything in the universe, we don't need to explain it fully in the beginning to help someone understand Gravity's acceleration, F=MA and you can't push a rope. Newton certainly didn't need it. For all I know, F=MA may very well be a special case in quantum mechanics, but I don't need it to calculate accelerations, velocities, etc Resistance is the specialized name for the case in which the impedance alone causes no delay and stores no electrical energy. All electrical impedance is defined by its voltage to current ratio, and is the total opposition (resistance and reactance) a circuit offers to the flow of electricity. For d-c, reactance doesn`t count. For a-c, total opposition consists of the vector (phasor) sum of resistance and reactance in a circuit. Impedance is measured in ohms and its reciprocal is called admittance. The symbol for impedance is Z. The symbol for admittance is Y. Steve also writes: "Poof! BUT converts it into radio frequency energy (RF) also called an electromagnetic field or wave." Yes. A radio wave is r-f energy which has escaped the confines of wires and doesn`t come back. Whenever wires in open space carry high-frequency current, some energy gets away as a radiated field, having a strength that varies inversely with the distance. Best regards, Richard Harrison, KB5WZI |
Steve, I also tried to give back and taught at a junior college for a couple
of years but I found out that talking and communicating were two different things. If what you do succeeds in comunicating then you are doing good where others have failed by resorting to just talking or handing out books. By you "communicating" you encourage independent thought which is so much better than relying just on memory and underlined quotes. If you are winning then keep at it and disregard comments that are without depth. Cheers Art "Steve Nosko" wrote in message ... Hi Richard, TOP and internal posting...sorry folks. I think you are learned on this subject and won't quibble about what really happens in the real world. I think you know and I claim that I know. I will, however pick a little bone in regards to the answer which I posted to an email since I also thought would help others at a similar level of understanding or confusion. Oh geeze! here he goes...you had to set him off.. Here's my mantra and why a I am a little miffed by (but actually understand) frequent attempts to correct my explanations. The words we use and the depth to which we go at any given point to describe things, have an effect on the ability of people to absorb the concepts. As an instructor of basics, I have worked very hard, for a long time, to understand and use effective ways to transfer an understanding of electronic principles to students at what might be considered the lower rungs of the technical ladder...the beginners...the hams also. There is what I'll call an "instructor's high" associated with the light bulb going on in a student. It's really cool. I carefully craft my responses to the apparent level of knowledge of the questioner. I do my best to form a coherent story which progresses from simple, where a concept needed to understand more complex concepts is explained first, without adding the unnecessary complications of true, but potentially confusing facts, to the more complex goal I perceive to be the questioner's goal. Once the basic concepts sinks in AND the student is ready for the next level, usually by a response, I then proceed to build. It is the old "speak to your audience" concept. I don't dispute that your explanations are correct. They appear very good, rather complete. I do believe however, that your most assuredly honest and well meaning attempt to be correct, completely correct, actually makes the subject more confusing to the beginner. I believe this because I have been there. In fact, I must, almost every class session, throttle myself from doing just the very same thing. Why? Because when I do, I have succeeded in causing more confusion, resulting in a mental block to learning which requires much more effort at damage control to erase the mental blockage I created with my ignorant desire to be completely correct. Please understand that I am being harsh on *myself* because I have been frustrated by this and work hard to keep it under control. As an Engineer, teaching technician students, one must keep in mind that there is a different state of mind and ability to absorb what to them, appears a very complex subject...but to my arrogant mind is really very simple. After all, piecewise parametric polynomial interpolation looked like an impossible concept, way beyond my comprehension back in 92 when I first saw reference to it. Now, it looks like the simplest thing any high school Algebra student can understand. I'm also at a point in my life that I have seen and done so much in this field (and it all seems so simple) that I wish to return some of it to others, and I wish to do it very effectively. Of course, now you're going to tell me that you also have been teaching for x years and your methods are equally successful...so be it. There needs to me more of us. BTW...what is your line, Richard? Some comments, corrections and whatever stuck my fancy about what you wrote... "Richard Harrison" wrote in message ... Steve Nosko wrote: "Apparently, because of the way the big bang occurred, when we put a voltage across a resistor current flows in a manner that we discovered follows the equation called Ohm`s law." Big bang? Ohm wasn`t around then. He lived 1787 to 1854. Ohm discovered that current in an electrical resistance is proportional to voltage. The concept I was trying to relate in a slightly 'light' manner was: The stuff that happens, happens 'cuz of what we call "physics", "physical laws" or "nature" or sump-in' like that, not because there is an equation making it happen. Resistors don't know Ohm's law and don't conduct current because of Ohm or his discoveries. The equation we call Ohm's law is simply a model of how reality works. Like a model airplane, which helps us understand what a real airplane looks like. Ohms law, and all the other equations, help us understand what real electronics "looks like". Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. A completely valid way to word it, but to a beginner I think the phrase "locked in step " is vague. It would be a good start, but probably needs expansion to explain what it means. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. I wouldn't have worded it that way, but it (resistor is the type of resistance) is a valid model to have in mind. That is, as a way to distinguish it from "a resistance which is not a resistor". This made me think of how I think of it.. and when I use the word "resistance" I think of it as as a resistor, yet an impedance has a real or "resistive" part. That word "resistance" for me conotes a "resistor" where the others conote the other concept. Interesting nomenclature, that's all. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, Well, here's where I'll say that I think this is truly a matter of symantics. Your terminlolgy implies that dissipation = heat. I agree that the most common usage it that "... is dissipated as heat...". However, this next bit: ...is in-phase with current through the resistance, but it does not cause energy loss. I think has a symantics problem. I'm sure you truly understand what happens, but the words "...does not cause energy loss." isn't correct, because the energy IS lost from the circuit. The circuit "can't tell" the difference 'tween the resistor and any other kind of resistive component. It just may or may not be as heat, right? You know what happens and I know what happens, but the OP didn't, so I was starting him down a path that wouldn't paint him into a corner of not being able to understand the other resistive types of things later...if so desired. An example of lossless resistance is the Zo or surge impedance of a transmission line. Again, the power IS lost from the source, no? I think this an important basic understanding. To the sourse, it is gone. Poof! never to be seen again. I think it is a good model to understand and helps go further without Maxwell complicating things. I think you can go pretty far without Maxwell (gee, twice in one paragraph) and still have a good amount of (correct) sixth sense about what is going on in electronics and transmission lines. Zo is ... yet converts no energy to heat in the lossless line. And my model didn't exclude this. I thought I was explicit about that without bringing in more complexity for the OP. "radiation resistance". ...is hardly a loss. Again, as far as the transmitter circuitry is concerned, it is. The following is a well done explanation which goes further and into more detail...with one disagreement. An ohm is the unit of resistance. It is defined at 0-degrees C, of a uniform column of mercury 106.300 cm long and weighing 14.451 grams. One ohm is the resistance which drops one voltt when a current of one amp is passed through it. Reactances are also defined by their volts to amps ratios (ohms). The big difference is that reactance does no work and produces no heat. Opposition to electrical current comes from delay required to store ard retrieve energy to and from fields in and around the reactances. Current lags the applied voltage in an inductance. At time = 0, no current flows into an inductance, but rises exponentially from the instant of initial energization. Current leads the applied voltage into a capacitance. At time = 0, full current flows into a capacitance but voltage across the capacitance is zero and rises exponentially from the instant of initial energization. In an a-c circuit, the current through an inductance lags the voltage by 90-degrees. In a a-c circuit, the current through a capacitance leads the voltage by 90-degrees. Phase shifts are produced by energy storage in reactance. There is no phase shift in a resistance. No electrical energy is stored in a resistor, but its matter does have a thermal capacity. Once its atoms are agitated by heat their inertia is evident in the resistance`s temperature. It takes time to cool. Steve wrote: "Things get all messed up." As old Carson Robinson sang: "Life gets tedious, Don`t it?" Steve gave the formulas for capacitive and inductive reactances. They have always seemed convenient to me. Steve says: "---we call this new kind of (corrupted) resistance "Impedance"." No. Impedance is the general name for opposition to electricity. No. In the context of my writing for someone who has an unserstanding of DC and resistance, reactance it a very confusing factor. It corrupts an otherwise simple world. Getting into Vector Algebra and phasors is a significant step up in mathematics for the beginner not inclined to go the Engineering route. What I'm saying is that although the unified field theory may very well be the absolutely correct explanation of everything in the universe, we don't need to explain it fully in the beginning to help someone understand Gravity's acceleration, F=MA and you can't push a rope. Newton certainly didn't need it. For all I know, F=MA may very well be a special case in quantum mechanics, but I don't need it to calculate accelerations, velocities, etc Resistance is the specialized name for the case in which the impedance alone causes no delay and stores no electrical energy. All electrical impedance is defined by its voltage to current ratio, and is the total opposition (resistance and reactance) a circuit offers to the flow of electricity. For d-c, reactance doesn`t count. For a-c, total opposition consists of the vector (phasor) sum of resistance and reactance in a circuit. Impedance is measured in ohms and its reciprocal is called admittance. The symbol for impedance is Z. The symbol for admittance is Y. Steve also writes: "Poof! BUT converts it into radio frequency energy (RF) also called an electromagnetic field or wave." Yes. A radio wave is r-f energy which has escaped the confines of wires and doesn`t come back. Whenever wires in open space carry high-frequency current, some energy gets away as a radiated field, having a strength that varies inversely with the distance. Best regards, Richard Harrison, KB5WZI |
Guys, you're off on a tangent!
I believe Efficiency is the ratio of power radiated to power input. If a dipole is 95% efficient it radiates 95 out of 100 watts. If a Yagi is 95% efficient it radiates 95 out of 100 watts. If a Quad is 95% efficient it radiates 95 out of 100 watts. If a vertical is 95% efficient it radiates 95 out of 100 watts. If a Log Periodic is 95% efficient it radiates 95 out of 100 watts. If a 1/10 wavelength antenna made of unobtainium is 95% efficient it radiates 95 out of 100 watts. Don't confuse Gain, Directivity and Efficiency in the discussion. Deacon Dave Richard Harrison wrote: Art, KB9MZ wrote: SNIP In any case, "efficient" is only as compared with similar devices. SNIP: Wrong!! See above Recall that dBd is the norm as an isotropic antenna is only a theoretical creature. Catalogs are filled with antenna characteristics as compared with a 1/2-wave dipole in free space. SNIP: The comparison is generally Gain as dBd, dBi, or dBu [unobtainium]. Not Efficiency!!! It is the standard of comparison. It could hardly be correctly called inefficient. Best regards, Richard Harrison, KB5WZI |
Cecil, defining efficiency as from transmitter to receiver. Isn't
the proper term 'Path Loss' and it's a variable due to propagation variations. So are we comparing my wet noodle to your wet noodle and we wiggle it in the middle. Conclusion: It is not valid to define efficiency based on unknowable and uncontrollable variables.. Deacon Dave Cecil Moore wrote: Richard Harrison wrote: Art, KB9MZ wrote: "The dipole is a very inefficient radiator." I seem to remember Kraus saying 95% efficiency was not unusual as a dipole efficiency. I don't think that's the efficiency that Art is talking about. Art's efficiency seems to be defined as the power delivered to the receiver divided by the power sourced by the transmitter. |
Probably true!
After all Murphy's Law was first postulated by Smith!! DD JDer8745 wrote: Howdy, I have always heard that what we call "Ohm's Law" is actually Cavendish's Law. But as the story goes, Cavendish didn't write a paper. Is this BS or true? Jack, K9CUN |
David
I think you can help me out on this efficiency malarkey. A dipole receives all signals within the dipoles range so its receive capabilities are well beyond the frequency span of choice I would venture to say that when discussing efficiency we should place bandwidth of choice received divided by the total bandwidth that the dipole actually receives and then multiply by 100. To say a dipole is 90 % efficient when some parts of a dipole supply radiation that is many times its other parts of equal lengths supply demands further explanation. Maximum radiation can only come about when the current flow is a maximum regardless of current input and is a constant per unit length and that description does not match a dipole which always require added insertion losses for equipment to overcome its inefficiences. If the dipole exceeds 90% efficiency then why waste effort and energy on interface devices between the antenna and the transformation to say.... audio? Efficiency should always be aimed at the energy needs required over the total energy that has to be supplied to meet required needs. If a truck carries a grain of desired gold buried in a ton of junk would you call the mining operation 100% efficient by ignoring search costs of finding the grain of gold and the removal costs for the junk? I believe the above verifies my initial statement that a dipole can be seen as inefficient. As an engineer I cannot agree with power in versus power out ( radiation) type statements as energy cannot be created or destroyed. Energy supplied by a lump of coal does not lose any energy in its change of state but as far as efficiency is concerned I do not count the energy that escaped in smoke as beneficial and thus quantified as a positive with respect to efficiency Regards Art "Dave Shrader" wrote in message news:_ozZb.356634$I06.3765208@attbi_s01... Guys, you're off on a tangent! I believe Efficiency is the ratio of power radiated to power input. If a dipole is 95% efficient it radiates 95 out of 100 watts. If a Yagi is 95% efficient it radiates 95 out of 100 watts. If a Quad is 95% efficient it radiates 95 out of 100 watts. If a vertical is 95% efficient it radiates 95 out of 100 watts. If a Log Periodic is 95% efficient it radiates 95 out of 100 watts. If a 1/10 wavelength antenna made of unobtainium is 95% efficient it radiates 95 out of 100 watts. Don't confuse Gain, Directivity and Efficiency in the discussion. Deacon Dave Richard Harrison wrote: Art, KB9MZ wrote: SNIP In any case, "efficient" is only as compared with similar devices. SNIP: Wrong!! See above Recall that dBd is the norm as an isotropic antenna is only a theoretical creature. Catalogs are filled with antenna characteristics as compared with a 1/2-wave dipole in free space. SNIP: The comparison is generally Gain as dBd, dBi, or dBu [unobtainium]. Not Efficiency!!! It is the standard of comparison. It could hardly be correctly called inefficient. Best regards, Richard Harrison, KB5WZI |
Typical 'Art Unwin'. Good word count. Zero meaning.
'Doc |
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