|
A: What is impedance (Z)
Unable to resist at least trying to provide the basis for some
understanding, Steve proceeds. Jim, you know who you are... Thank you. Here's a go at a start. 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. The resistor "resists", determines or limits the current. Oh yea, resistors have this characteristic we call resistance measured in "Ohms", just for using in the formulas. Ohms law: I = V/R Say... 12 Volts on a 50 ohm resistor results in 0.24 amps flowing. For the same reason (big bang) this removes power from the circuit, or "dissipates" it. Poof! Gone from the circuit. Resistors happen to turn this power into heat. The value being discoverable by the power formula: P=IxV and the variations P=E^2/R and P=I^2xR It also turns out that ANYTHING else that removes power from a circuit looks just like a resistor to the circuit (obeys Ohm's law), and *ONLY* things that LOOK just like a resistor (behave or conduct current according to Ohm's law) will so remove power from said ckt. IF you didn't catch this, there are things that are not really resistors, yet act just like them as far as a circuit is concerned. Unfortunately, life is fraught with dangers and we have capacitors (C) and inductors (L)(or things which behave just like them or combinations of them). When we get into this realm, the "R" from above, just doesn't do it. Things get all messed up. These things also "resist" current flow. (or determine or limit it). We call this form of resisting "Reactance", use the letter "X" to represent it and it also is measured in "Ohms", just for using in the formulas. Oh yea, we also use the little subscript letter to indicate if it is an inductive (l) or capacitive (c)reactance. Xc ("X" sub c) = 1/(2 x pi x f x C ) Xl ("X" sub L) = 2 x pi x f x L When we want to talk about the effect or either an "L" or a "C" we simply use the term "Reactance" It's like a good substitute for "he/she" (the "wrong one being "they"). Because of (big bang again) the way the current in these (C & L) corruptions, of our purely resistive world, work out to be 90 degrees out of phase with the voltage (we are talking about AC now), we had to find a way to account for them. I won't trouble you with just why now, but we use what is called the "Series Representation". It looks like two numbers with a + or - sign between them and all together we call this new kind of (corrupted) resistance "Impedance". And use the letter "Z" to represent it. It has some Resistance and some Reactance in there and it will have numbers on ohms: In general: It looks like this: Z = R + jX The "R" is the same kind of resistor as above, the "X" is one of the reactances. The "j" helps the mathematicians do the math - like ohms law - but with the reactance accounted for. In "math speak" the "R" is the "real" part and the "X" is the "Imaginary" part of the impedance. Impedance also resists current flow, but with the reactance in there, you can't use Ohm's law like you used to. SO... When I say "Impedance" or use "Z" I am talking about whatever happens to be there. Since I don't know if it is only resistive, called also "Purely resistive", or has some reactance in it, called "reactive", (or if I am just too lazy to figure it out at the time), I use this word or symbol to cover any situation. Finally, since only the "resistive part" of a circuit dissipates any power, we like to remove (somehow) all the reactance (or imaginary part) and somehow make the real part (the resistive part) what we like best (for a given situation). Doing this is the infinitely complex subject called "impedance matching". When we make this happen on an antenna, the remaining "resistive part" sucks power from the circuit (the transmitter circuit) Poof! BUT converts it into radiated radio frequency energy (RF) also called an electromagnetic field or wave. Fortunately for us in this modern day and age, because if it didn't all the receivers that we have would be useless and we would wonder why we built them. Help any??? 73 Steve-- Steve N, K,9;d, c. i My email has no u's. |
Hi-Ho Stevo, Outstanding reply to Jimbo and a bunch of us out here that
do not really "know" all that we "undetstand" about electronics! There, I said it for the bunch! No flames from the huddling masses now! Butch KF5DE Steve Nosko wrote: Unable to resist at least trying to provide the basis for some understanding, Steve proceeds. Jim, you know who you are... snippity-snip |
Steve's info will get you a beginners understanding of circuit theory which is based on a low-frequency, quasi-static simplification of electromagnetic theory. Unfortunately, anything that has any appreciable length, such as a transmission line or an antenna, or a long coil of wire as Yuri and Cecil are arguing about, can't be adequately explained by simple circuit theory; you have to study wave mechanics to get any real idea of what is happening in these situations. That isn't the end of it, though, since in order to understand what is happening when an object radiates, you have to understand Maxwell's equations. In order to understand Maxwell's equations, you'd better know vector calculus. That isn't the end, either, but it's as close as any *normal* human wants to go. Whenever someone who was taught circuit theory tries to apply its vocabulary and concepts to explain all electromagnetic phenomena, that someone is going to run into trouble and come up with a multitude of idiocies for which which he'll find no end of people ready to criticize him. This is the problem: Cecil and Yuri want to explain the current taper through a long solenoidal coil using the vocabulary and concepts of circuit theory rather than the difficult but more precise language of electromagnetic theory. So far they've failed miserably, not least because they don't even seem to have a coherent idea of what they mean by "current flow." I wish them luck, but I hope no one takes any of their ideas seriously. 73, Tom Donaly, KA6RUH Steve wrote, Unable to resist at least trying to provide the basis for some understanding, Steve proceeds. Jim, you know who you are... Thank you. Here's a go at a start. 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. The resistor "resists", determines or limits the current. Oh yea, resistors have this characteristic we call resistance measured in "Ohms", just for using in the formulas. Ohms law: I = V/R Say... 12 Volts on a 50 ohm resistor results in 0.24 amps flowing. For the same reason (big bang) this removes power from the circuit, or "dissipates" it. Poof! Gone from the circuit. Resistors happen to turn this power into heat. The value being discoverable by the power formula: P=IxV and the variations P=E^2/R and P=I^2xR It also turns out that ANYTHING else that removes power from a circuit looks just like a resistor to the circuit (obeys Ohm's law), and *ONLY* things that LOOK just like a resistor (behave or conduct current according to Ohm's law) will so remove power from said ckt. IF you didn't catch this, there are things that are not really resistors, yet act just like them as far as a circuit is concerned. Unfortunately, life is fraught with dangers and we have capacitors (C) and inductors (L)(or things which behave just like them or combinations of them). When we get into this realm, the "R" from above, just doesn't do it. Things get all messed up. These things also "resist" current flow. (or determine or limit it). We call this form of resisting "Reactance", use the letter "X" to represent it and it also is measured in "Ohms", just for using in the formulas. Oh yea, we also use the little subscript letter to indicate if it is an inductive (l) or capacitive (c)reactance. Xc ("X" sub c) = 1/(2 x pi x f x C ) Xl ("X" sub L) = 2 x pi x f x L When we want to talk about the effect or either an "L" or a "C" we simply use the term "Reactance" It's like a good substitute for "he/she" (the "wrong one being "they"). Because of (big bang again) the way the current in these (C & L) corruptions, of our purely resistive world, work out to be 90 degrees out of phase with the voltage (we are talking about AC now), we had to find a way to account for them. I won't trouble you with just why now, but we use what is called the "Series Representation". It looks like two numbers with a + or - sign between them and all together we call this new kind of (corrupted) resistance "Impedance". And use the letter "Z" to represent it. It has some Resistance and some Reactance in there and it will have numbers on ohms: In general: It looks like this: Z = R + jX The "R" is the same kind of resistor as above, the "X" is one of the reactances. The "j" helps the mathematicians do the math - like ohms law - but with the reactance accounted for. In "math speak" the "R" is the "real" part and the "X" is the "Imaginary" part of the impedance. Impedance also resists current flow, but with the reactance in there, you can't use Ohm's law like you used to. SO... When I say "Impedance" or use "Z" I am talking about whatever happens to be there. Since I don't know if it is only resistive, called also "Purely resistive", or has some reactance in it, called "reactive", (or if I am just too lazy to figure it out at the time), I use this word or symbol to cover any situation. Finally, since only the "resistive part" of a circuit dissipates any power, we like to remove (somehow) all the reactance (or imaginary part) and somehow make the real part (the resistive part) what we like best (for a given situation). Doing this is the infinitely complex subject called "impedance matching". When we make this happen on an antenna, the remaining "resistive part" sucks power from the circuit (the transmitter circuit) Poof! BUT converts it into radiated radio frequency energy (RF) also called an electromagnetic field or wave. Fortunately for us in this modern day and age, because if it didn't all the receivers that we have would be useless and we would wonder why we built them. Help any??? 73 Steve-- Steve N, K,9;d, c. i My email has no u's. |
Time out!! You people are taking all this far to seriously. Just throw
an aerial out the window, feed it to your rig via a tuner, and enjoy Amateur radio. Butch Magee KF5DE Tdonaly wrote: Steve's info will get you a beginners understanding of circuit theory which is based on a low-frequency, quasi-static simplification of electromagnetic theory. Unfortunately, anything that has any appreciable length, such as a transmission line or an antenna, or a long coil of wire as Yuri and Cecil are arguing about, can't be adequately explained by simple circuit theory; you have to study wave mechanics to get any real idea of what is happening in these situations. That isn't the end of it, though, since in order to understand what is happening when an object radiates, you have to understand Maxwell's equations. In order to understand Maxwell's equations, you'd better know vector calculus. That isn't the end, either, but it's as close as any *normal* human wants to go. Whenever someone who was taught circuit theory tries to apply its vocabulary and concepts to explain all electromagnetic phenomena, that someone is going to run into trouble and come up with a multitude of idiocies for which which he'll find no end of people ready to criticize him. This is the problem: Cecil and Yuri want to explain the current taper through a long solenoidal coil using the vocabulary and concepts of circuit theory rather than the difficult but more precise language of electromagnetic theory. So far they've failed miserably, not least because they don't even seem to have a coherent idea of what they mean by "current flow." I wish them luck, but I hope no one takes any of their ideas seriously. 73, Tom Donaly, KA6RUH Steve wrote, Unable to resist at least trying to provide the basis for some understanding, Steve proceeds. Jim, you know who you are... Thank you. Here's a go at a start. 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. The resistor "resists", determines or limits the current. Oh yea, resistors have this characteristic we call resistance measured in "Ohms", just for using in the formulas. Ohms law: I = V/R Say... 12 Volts on a 50 ohm resistor results in 0.24 amps flowing. For the same reason (big bang) this removes power from the circuit, or "dissipates" it. Poof! Gone from the circuit. Resistors happen to turn this power into heat. The value being discoverable by the power formula: P=IxV and the variations P=E^2/R and P=I^2xR It also turns out that ANYTHING else that removes power from a circuit looks just like a resistor to the circuit (obeys Ohm's law), and *ONLY* things that LOOK just like a resistor (behave or conduct current according to Ohm's law) will so remove power from said ckt. IF you didn't catch this, there are things that are not really resistors, yet act just like them as far as a circuit is concerned. Unfortunately, life is fraught with dangers and we have capacitors (C) and inductors (L)(or things which behave just like them or combinations of them). When we get into this realm, the "R" from above, just doesn't do it. Things get all messed up. These things also "resist" current flow. (or determine or limit it). We call this form of resisting "Reactance", use the letter "X" to represent it and it also is measured in "Ohms", just for using in the formulas. Oh yea, we also use the little subscript letter to indicate if it is an inductive (l) or capacitive (c)reactance. Xc ("X" sub c) = 1/(2 x pi x f x C ) Xl ("X" sub L) = 2 x pi x f x L When we want to talk about the effect or either an "L" or a "C" we simply use the term "Reactance" It's like a good substitute for "he/she" (the "wrong one being "they"). Because of (big bang again) the way the current in these (C & L) corruptions, of our purely resistive world, work out to be 90 degrees out of phase with the voltage (we are talking about AC now), we had to find a way to account for them. I won't trouble you with just why now, but we use what is called the "Series Representation". It looks like two numbers with a + or - sign between them and all together we call this new kind of (corrupted) resistance "Impedance". And use the letter "Z" to represent it. It has some Resistance and some Reactance in there and it will have numbers on ohms: In general: It looks like this: Z = R + jX The "R" is the same kind of resistor as above, the "X" is one of the reactances. The "j" helps the mathematicians do the math - like ohms law - but with the reactance accounted for. In "math speak" the "R" is the "real" part and the "X" is the "Imaginary" part of the impedance. Impedance also resists current flow, but with the reactance in there, you can't use Ohm's law like you used to. SO... When I say "Impedance" or use "Z" I am talking about whatever happens to be there. Since I don't know if it is only resistive, called also "Purely resistive", or has some reactance in it, called "reactive", (or if I am just too lazy to figure it out at the time), I use this word or symbol to cover any situation. Finally, since only the "resistive part" of a circuit dissipates any power, we like to remove (somehow) all the reactance (or imaginary part) and somehow make the real part (the resistive part) what we like best (for a given situation). Doing this is the infinitely complex subject called "impedance matching". When we make this happen on an antenna, the remaining "resistive part" sucks power from the circuit (the transmitter circuit) Poof! BUT converts it into radiated radio frequency energy (RF) also called an electromagnetic field or wave. Fortunately for us in this modern day and age, because if it didn't all the receivers that we have would be useless and we would wonder why we built them. Help any??? 73 Steve-- Steve N, K,9;d, c. i My email has no u's. |
"Butch" wrote in message ... Time out!! You people are taking all this far to seriously. Just throw an aerial out the window, feed it to your rig via a tuner, and enjoy Amateur radio. Butch Magee KF5DE It just not that simple, Butch. I'm sure you have heard that Ham radio is a hobby that has many facets; construction, public service, contesting, field trips, QRP DX, etc. Some of our members get their kicks merging theory with rag chewing. 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. Ed WB6WSN |
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. Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, current drop is in-phase with the applied volts, or voltage dropped across the resistance is in-phase with current through the resistance, but it does not cause energy loss. An example of lossless resistance is the Zo or surge impedance of a transmission line. Zo is caused by the distributed inductance and capacitance of the line, but current in the line is in-phase with the voltage across the line. Zo is the voltage to current ratio of the waves traveling in either direction on the transmission line. Zo = volts/amps, yet converts no energy to heat in the lossless line. Another example of lossless resistance is "radiation resistance". This is the desired antenna load, so it is hardly a loss. Loss in the wire, earth, and insulators of the antenna are resistive loads which produce heat but don`t help the signal. 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. 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 |
Richard:
Hmmm.... Impedance... let's give it its' proper due! It was the self taught "electrician", and ultimately Fellow of the Royal Society, Oliver Heaviside, FRS [1850 - 1925] who was born in the London slums to a very poor family and who had never attended any school beyond the age of 16 who was the person who coined, defined and first used the terms "impedance", "admittance", and "reactance". Oliver Heaviside also gave us Maxwell's Equations in the form we now know them. Maxwell wrote his equations in the form of 22 separate equations using the arcane method of "quaternions". Heaviside simplified those 22 equations given by Maxwell down to the four simple equations with two auxilliary constituent relations that we now know and love. James Clerk Maxwell was a Cambridge educated mathematician from an affluent and educated family. Oliver Heaviside was a poor kid from the London slums who had to go out to work at age 16 and never saw the inside of a college or university! Heaviside never appeared to receive the citation at the ceremony to which he was invited when he was inducted as a Fellow of the Royal Society after he was duly elected to that lofty title by the greatest Scientists of the day. "Impedance"... thank you Oliver! -- Peter K1PO Indialantic By-the-Sea, FL "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. Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, current drop is in-phase with the applied volts, or voltage dropped across the resistance is in-phase with current through the resistance, but it does not cause energy loss. An example of lossless resistance is the Zo or surge impedance of a transmission line. Zo is caused by the distributed inductance and capacitance of the line, but current in the line is in-phase with the voltage across the line. Zo is the voltage to current ratio of the waves traveling in either direction on the transmission line. Zo = volts/amps, yet converts no energy to heat in the lossless line. Another example of lossless resistance is "radiation resistance". This is the desired antenna load, so it is hardly a loss. Loss in the wire, earth, and insulators of the antenna are resistive loads which produce heat but don`t help the signal. 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. 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 |
I have been convinced that "impedance" is the ratio of force to response in any media. That has worked well for me. Maybe there are readers who can set me straight if I've been wrong. Jerry "Peter O. Brackett" wrote in message hlink.net... Richard: Hmmm.... Impedance... let's give it its' proper due! It was the self taught "electrician", and ultimately Fellow of the Royal Society, Oliver Heaviside, FRS [1850 - 1925] who was born in the London slums to a very poor family and who had never attended any school beyond the age of 16 who was the person who coined, defined and first used the terms "impedance", "admittance", and "reactance". Oliver Heaviside also gave us Maxwell's Equations in the form we now know them. Maxwell wrote his equations in the form of 22 separate equations using the arcane method of "quaternions". Heaviside simplified those 22 equations given by Maxwell down to the four simple equations with two auxilliary constituent relations that we now know and love. James Clerk Maxwell was a Cambridge educated mathematician from an affluent and educated family. Oliver Heaviside was a poor kid from the London slums who had to go out to work at age 16 and never saw the inside of a college or university! Heaviside never appeared to receive the citation at the ceremony to which he was invited when he was inducted as a Fellow of the Royal Society after he was duly elected to that lofty title by the greatest Scientists of the day. "Impedance"... thank you Oliver! -- Peter K1PO Indialantic By-the-Sea, FL "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. Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, current drop is in-phase with the applied volts, or voltage dropped across the resistance is in-phase with current through the resistance, but it does not cause energy loss. An example of lossless resistance is the Zo or surge impedance of a transmission line. Zo is caused by the distributed inductance and capacitance of the line, but current in the line is in-phase with the voltage across the line. Zo is the voltage to current ratio of the waves traveling in either direction on the transmission line. Zo = volts/amps, yet converts no energy to heat in the lossless line. Another example of lossless resistance is "radiation resistance". This is the desired antenna load, so it is hardly a loss. Loss in the wire, earth, and insulators of the antenna are resistive loads which produce heat but don`t help the signal. 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. 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 |
Tom,I agree with much of what you say but the problem goes much deeper
than that, and much of the blame rests with academics taught. Let us look at what is called by some as a 'simple dipole'. The dipole is very inefficient radiator. The only claim that you can place on it is that it is has a low impedance at resonance...Period. There is no calculation available in any of the touted books that maximum gain per unit length is design related to a dipole! The dipole is only a reference that other antennas can be related to even tho it is a very inefficient radiator per unit length. Over time academics have made the dipole as something very efficient about which every advance must be related . That Tom is very incorrect and it is that which is what prevents the emergence of new ideas that push the envelope. If one just spouts what is in present day books then they are just followers that suck up the dipole aproach which thus prevents them from contributing anything that pushes out the envelope. Education can only take you so far and it is dependent on those who have received an education to push the envelope further. If one doesn't do this then they are just quoting things that were told to them or they read in some book and thus are not equiped to pushing the envelope. Until the simple dipole is shead of its illusionary powers by the academics who write the books newcomers can only copy, and not progress. Ofcourse, academics who just memorise can still attack people, those who do not agree with them, in a personal way in the hope that a raucous crowd of peasants will echo the academics trash around the Gillotine. Regards Art (Tdonaly) wrote in message ... Steve's info will get you a beginners understanding of circuit theory which is based on a low-frequency, quasi-static simplification of electromagnetic theory. Unfortunately, anything that has any appreciable length, such as a transmission line or an antenna, or a long coil of wire as Yuri and Cecil are arguing about, can't be adequately explained by simple circuit theory; you have to study wave mechanics to get any real idea of what is happening in these situations. That isn't the end of it, though, since in order to understand what is happening when an object radiates, you have to understand Maxwell's equations. In order to understand Maxwell's equations, you'd better know vector calculus. That isn't the end, either, but it's as close as any *normal* human wants to go. Whenever someone who was taught circuit theory tries to apply its vocabulary and concepts to explain all electromagnetic phenomena, that someone is going to run into trouble and come up with a multitude of idiocies for which which he'll find no end of people ready to criticize him. This is the problem: Cecil and Yuri want to explain the current taper through a long solenoidal coil using the vocabulary and concepts of circuit theory rather than the difficult but more precise language of electromagnetic theory. So far they've failed miserably, not least because they don't even seem to have a coherent idea of what they mean by "current flow." I wish them luck, but I hope no one takes any of their ideas seriously. 73, Tom Donaly, KA6RUH Steve wrote, Unable to resist at least trying to provide the basis for some understanding, Steve proceeds. Snip |
"Butch" wrote in message
... Hi-Ho Stevo, Outstanding reply to Jimbo and a bunch of us out here that do not really "know" all that we "undetstand" about electronics! There, I said it for the bunch! No flames from the huddling masses now! Butch KF5DE Steve Nosko wrote: Unable to resist at least trying to provide the basis for some understanding, Steve proceeds. Jim, you know who you are... snippity-snip Thanks, Butch. That was the intent. Glad it it helps. Please don't huddle and don't be so snippity ( ; - ) -- Steve N, K,9;d, c. i My email has no u's. |
"Tdonaly" wrote in message
... Steve's info will get you a beginners understanding of circuit theory That WAS the intent. which is based on a low-frequency, quasi-static simplification of electromagnetic theory. Yikes! Call it what you like. Unfortunately, anything that has any appreciable length, such as a transmission line or an antenna... wave mechanics to get any real idea of what is happening in these situations. I guess you can call it "wave mechanics" if you like, but it IS true that what happens on a transmission line is waves and this is quite different from simple circuit theory. First you need the circuit theory, though. That isn't the end of it, though, since in order to understand what is happening when an object radiates, you have to understand Maxwell's equations....vector calculus. This I'll disagree with. It's been so long since I studied Maxwell's equations, I can't even spell his name, but I can give a workable explanatin of radiation that the beginner can understand and won't cause trouble for any ham's purposes. Will it violate old Maxwell? I don't know and don't care for my purposes and 90% of the people interested. That isn't the end, either, but it's as close as any *normal* human wants to go. Whew! sure glad I'm *abnormal*. Whenever someone who was taught circuit theory tries to apply its vocabulary and concepts to explain all electromagnetic phenomena, that someone is going to run into trouble and come up with a multitude of idiocies for which which he'll find no end of people ready to criticize him. Whoa... Sure glad I'm not trying to do THAT! This is the problem: Cecil and Yuri want to explain the current taper through a long solenoidal coil using the vocabulary and concepts of circuit theory rather than the difficult but more precise language of electromagnetic theory. Sure glad I don't care and that I didn't tack my post onto theirs thus indicating that I was trying to enter that discussion. 73 Steve-- Steve N, K,9;d, c. i My email has no u's. |
Well, then there's that too..
-- (:-) Steve N, K,9;d, c. i My email has no u's. "Butch" wrote in message ... Time out!! You people are taking all this far to seriously. Just throw an aerial out the window, feed it to your rig via a tuner, and enjoy Amateur radio. Butch Magee KF5DE Tdonaly wrote: Steve's info will get you a beginners understanding ... ...quasi-static. ...electromagnetic theory. ... ...wave mechanics... ...Maxwell's equations.... ...vector calculus. ...any *normal* human... ...multitude of idiocies ...no end of people ready to criticize him. |
Oh yea! that too... I forgot "Maxwell"
-- Steve N, K,9;d, c. i My email has no u's. "Ed Price" wrote in message news:YFmZb.5138$C21.2768@fed1read07... "Butch" wrote in message ... Time out!! You people are taking all this far to seriously. Just throw an aerial out the window, feed it to your rig via a tuner, and enjoy Amateur radio. Butch Magee KF5DE It just not that simple, Butch. I'm sure you have heard that Ham radio is a hobby that has many facets; construction, public service, contesting, field trips, QRP DX, etc. Some of our members get their kicks merging theory with rag chewing. 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. Ed WB6WSN |
Peter, K1PO wrote:
"Oliver heaviside was a poor kid from the London slums who had to go out to work at age 16 and never saw the inside of a college or university." I am aware of Heaviside`s story. He was the idol of one of my professors who frerquently regaled us with heaviside stories, so he became one of my favorites too. Maxwell is not diminished by his advantages. He had the mathematical background he needed to formulate his equations and the moxie to speculate that displacement current generates a magnetic field same as a conduction current does. This is the secret of radiation. Heaviside was able to improve on the calculus, and simplify and reorganize Maxwell`s work. Michael Faraday discovered electromagnetic induction and deserves a lot of credit too. Everybody benefits from the work of others in complicated fields. Faraday lived 1791-1867. Maxwell lived 1831-1879. Heaviside lived 1850-1925. This really was during a golden age for the British. I had the Maxwell`s equations course many decades ago. Strangely enough, it was titled "Ultra High Frequency Techniques". You really had to read the syllabus to know what the course was about. Best regards, Richard Harrison, KB5WZI |
Jerry Martes wrote:
"I have never been convinced that "impedance" is the ratio of force to response in any media." Jerry framed the question very nicely. The logic seems simple. More force is required when resistance to change is higher. When current is very small despite high force, it must be due to high resistance. Resistance proportional to force (volts) and inversely proportional to current (amps) seems perfectly logical to me. R=E/I Best regards, Richard Harrison, KB5WZI |
Art, KB9MZ wrote:
"The dipole is a very inefficient radiator." Kraus, unfortunately, wasn`t one of my books until recently. I don`t have the words memorized or know where they appear as I do with some of Terman. I seem to remember Kraus saying 95% efficiency was not unusual as a dipole efficiency. As there are so many variations, it`s like a baseball statistic, there must be a statistic that fits somewhere. In any case, "efficient" is only as compared with similar devices. 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. It is the standard of comparison. It could hardly be correctly called inefficient. Best regards, Richard Harrison, KB5WZI |
Yep!! Very Good Coffee!!!!!!!!!!!
Steve Nosko wrote: Oh yea! that too... I forgot "Maxwell" |
I just love it when those born in the slums of London even tho they went to
work when they were 16 they had enough smarts to go head to head with the experts. It must be a result of the morning fog from the river where one learns quickly what is real and what is not. Going to work for a living at 16 is not all that bad since it allows you to make personal decisions that can benefit before the onset of age makes it too late. An East Ender Art "Peter O. Brackett" wrote in message hlink.net... Richard: Hmmm.... Impedance... let's give it its' proper due! It was the self taught "electrician", and ultimately Fellow of the Royal Society, Oliver Heaviside, FRS [1850 - 1925] who was born in the London slums to a very poor family and who had never attended any school beyond the age of 16 who was the person who coined, defined and first used the terms "impedance", "admittance", and "reactance". Oliver Heaviside also gave us Maxwell's Equations in the form we now know them. Maxwell wrote his equations in the form of 22 separate equations using the arcane method of "quaternions". Heaviside simplified those 22 equations given by Maxwell down to the four simple equations with two auxilliary constituent relations that we now know and love. James Clerk Maxwell was a Cambridge educated mathematician from an affluent and educated family. Oliver Heaviside was a poor kid from the London slums who had to go out to work at age 16 and never saw the inside of a college or university! Heaviside never appeared to receive the citation at the ceremony to which he was invited when he was inducted as a Fellow of the Royal Society after he was duly elected to that lofty title by the greatest Scientists of the day. "Impedance"... thank you Oliver! -- Peter K1PO Indialantic By-the-Sea, FL "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. Resistance is the type of impedance (opposition to electrical current) in which current is locked in step to the applied voltage. The item called a resistor is the type of resistance that converts electrical energy to heat energy. Not all resistances are resistors. Some resistances don`t convert electrical energy directly into heat. In these non-dissipative resistances, current drop is in-phase with the applied volts, or voltage dropped across the resistance is in-phase with current through the resistance, but it does not cause energy loss. An example of lossless resistance is the Zo or surge impedance of a transmission line. Zo is caused by the distributed inductance and capacitance of the line, but current in the line is in-phase with the voltage across the line. Zo is the voltage to current ratio of the waves traveling in either direction on the transmission line. Zo = volts/amps, yet converts no energy to heat in the lossless line. Another example of lossless resistance is "radiation resistance". This is the desired antenna load, so it is hardly a loss. Loss in the wire, earth, and insulators of the antenna are resistive loads which produce heat but don`t help the signal. 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. 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 |
|
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! =----- |
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 |
Ofcourse it is meaningless to you as you are lacking in independent thought.
Because you are mentally disabled you should not condemn independant thoughts of others"'Doc" I am still amazed that you think that by referring to yourself as a Doctor your statements then carry an aura of authenticity when in actual fact it shows your lack of knowledge wrote in message ... Typical 'Art Unwin'. Good word count. Zero meaning. 'Doc |
Art,
Pssst! As I've explained to you at least six times before, "Doc" is a nick name. It has nothing at all to do with any degree, or profession. I'm sorry you can't understand that. I have never referred to my self as a doctor of anything. You have referred to me as 'Doctor' several times, and each time I've tried to correct that misimpression. Add this time to that list. My thoughts are fairly conventional, but there are a few independent ones that sneak in every once in a while. All in all, I'm boringly average. I'm comfortable with that, not sure I'd even want to change it, too lazy I think. I'm also fairly experienced in recognizing B.S. when I hear it (used to be a government employee, you know). 'Doc (Not to be confused with 'Doctor') |
Art, It's Saturday morning here and I'm just reading my email before my
wife and I run away from home to visit the Grandkids and go out to eat for the DAY. I am a minister and will be busy most of Sunday. I'll try to respond late Sunday or Monday morning. Deacon Dave aunwin wrote: 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 |
Oooooops
I meant mentally challenged, mentally handicapped is politically incorrect Art "'Doc" wrote in message ... Art, Pssst! As I've explained to you at least six times before, "Doc" is a nick name. It has nothing at all to do with any degree, or profession. I'm sorry you can't understand that. I have never referred to my self as a doctor of anything. You have referred to me as 'Doctor' several times, and each time I've tried to correct that misimpression. Add this time to that list. My thoughts are fairly conventional, but there are a few independent ones that sneak in every once in a while. All in all, I'm boringly average. I'm comfortable with that, not sure I'd even want to change it, too lazy I think. I'm also fairly experienced in recognizing B.S. when I hear it (used to be a government employee, you know). 'Doc (Not to be confused with 'Doctor') |
Z
|
teve Nosko wrote:
"BTW--what is your line, Richard?" I apologize for a critical tone in my response to Steve`s posting. An ancient previous discussion of dissipationless resistance in this newsgroup leaves me primed to comment when it appears unappreciated. Dissipationless resistance is the stuff which allows a Class C amplifier exceed 50% efficiency. I won`t say I`ve been teaching X years, as I`ve never had that role. Long ago, I found my patience and temperament unsuited to tutoring. I am a long retired electrical engineer and find entertainment in the newsgroups. Best regards, Richard Harrison, KB5WZI |
"Art Unwin KB9MZ" wrote in message m... Tom,I agree with much of what you say but the problem goes much deeper than that, and much of the blame rests with academics taught. Let us look at what is called by some as a 'simple dipole'. The dipole is very inefficient radiator. The only claim that you can place on it is that it is has a low impedance at resonance...Period. There is no calculation available in any of the touted books that maximum gain per unit length is design related to a dipole! The dipole is only a reference that other antennas can be related to even tho it is a very inefficient radiator per unit length. Over time academics have made the dipole as something very efficient about which every advance must be related . That Tom is very incorrect and it is that which is what prevents the emergence of new ideas that push the envelope. If one just spouts what is in present day books then they are just followers that suck up the dipole aproach which thus prevents them from contributing anything that pushes out the envelope. Education can only take you so far and it is dependent on those who have received an education to push the envelope further. If one doesn't do this then they are just quoting things that were told to them or they read in some book and thus are not equiped to pushing the envelope. Until the simple dipole is shead of its illusionary powers by the academics who write the books newcomers can only copy, and not progress. Ofcourse, academics who just memorise can still attack people, those who do not agree with them, in a personal way in the hope that a raucous crowd of peasants will echo the academics trash around the Gillotine. Regards Art Gain and efficecey have nothing to do with each other Efficency is based on how much of your signal your antenna turns into heat compared to the amount radiated and nothing more. Gain is based of how your antenna shapes the pattern. The fact is a simple dipole will often service more area than high gain antennas. The high gain antenna just uses radiation that would normally go some where you are not interested in to intensifies the signal in an area where you want to communicate. Art this is a fact you really need to understand. Dont feel bad about it though, I believe gain was a very poor word chosen to discribe the effect of an antenna on the shape of its field. Gain typically means to amplify which is something an antenna can not do. This all means that it is possible that a simple dipole is more efficent than a Yagi_Uda antenna with 10 dbd of gain. The dipole may be slighly more effeicent due to less losses coupling to the feed line. Mind you this will be a very small diference in losses when comparing well designed antennas. Unless you are willing to give demonstrative proof of your ideas you should not insult us that that hold dear our beliefs and theories by refering to us as raucous crowd of peasants. I you are unwilling to prove your points you only appear as a fool. Our belefs and theories have been tested over many years and have found to be true as far as they have been tested, your ideas have not been tested by you at all. You assign words new meanings that are not typical of those discussing antennas and expect others to understand you. You ask for critical opinon of your ideaas but become angry when someone disagrees with you. If you really think you have some kind of new break through put your money where yiur mouth is and demonstrate them or go join the free power bunch, they will love and embrace you and take your money.. |
Dave Shrader wrote:
"I believe Efficiency is the ratio of power radiated to power input." Dave has a point. Basic efficiency is output divided by input. Power, work, or energies can be used for the ratio. An example of energy efficiency is in the "all day efficiency" of an electric distribution transformer. The transformer may be energized but supplying little or no energy during many of the 24 hours. While idle, the transformer draws excitation current just as it does when fully loaded. So, the transformer`s 24-hour average efficiency is lower than its efficiency while nearly fully loaded. Best regards, Richard Harrison, KB5WZI |
What allows a class-C amplifier to exceed 50% efficiency is a small
operating angle. Reg, G4FGQ |
"Jimmy" wrote in message . com... "Art Unwin KB9MZ" wrote in message m... Tom,I agree with much of what you say but the problem goes much deeper than that, and much of the blame rests with academics taught. Let us look at what is called by some as a 'simple dipole'. The dipole is very inefficient radiator. The only claim that you can place on it is that it is has a low impedance at resonance...Period. There is no calculation available in any of the touted books that maximum gain per unit length is design related to a dipole! The dipole is only a reference that other antennas can be related to even tho it is a very inefficient radiator per unit length. Over time academics have made the dipole as something very efficient about which every advance must be related . That Tom is very incorrect and it is that which is what prevents the emergence of new ideas that push the envelope. If one just spouts what is in present day books then they are just followers that suck up the dipole aproach which thus prevents them from contributing anything that pushes out the envelope. Education can only take you so far and it is dependent on those who have received an education to push the envelope further. If one doesn't do this then they are just quoting things that were told to them or they read in some book and thus are not equiped to pushing the envelope. Until the simple dipole is shead of its illusionary powers by the academics who write the books newcomers can only copy, and not progress. Ofcourse, academics who just memorise can still attack people, those who do not agree with them, in a personal way in the hope that a raucous crowd of peasants will echo the academics trash around the Gillotine. Regards Art Gain and efficecey have nothing to do with each other Oooooops I have been pushing radiation efficiency per unit length for so long my fingers gave up on me and wrote gain Efficency is based on how much of your signal your antenna turns into heat compared to the amount radiated and nothing more. Gain is based of how your antenna shapes the pattern. The fact is a simple dipole will often service more area than high gain antennas. The high gain antenna just uses radiation that would normally go some where you are not interested in to intensifies the signal in an area where you want to communicate. Art this is a fact you really need to understand. Dont feel bad about it though, I believe gain was a very poor word chosen to discribe the effect of an antenna on the shape of its field. Gain typically means to amplify which is something an antenna can not do. This all means that it is possible that a simple dipole is more efficent than a Yagi_Uda antenna with 10 dbd of gain. The dipole may be slighly more effeicent due to less losses coupling to the feed line. Mind you this will be a very small diference in losses when comparing well designed antennas. Unless you are willing to give demonstrative proof of your ideas you should not insult us that that hold dear our beliefs and theories by refering to us as raucous crowd of peasants. I you are unwilling to prove your points you only appear as a fool. So am a fool.. so what Our belefs and theories have been tested over many years and have found to be true as far as they have been tested, your ideas have not been tested by you at all. Oh not so...I tried to share it with the group many times and always called me a fool so I must be one. As for my ideas being tested ofcourse they have and I laid out the money and did the walk You assign words new meanings that are so if you have trouble by me not using typical word then ask questions, I think for myself not typical of those discussing antennas and expect others to understand you. Geez What started all this,are you a buddy of the doctor or something? I declared a antenna with a patent infact two of them,they did not attract attention but at least I did my thing.And yes I have another one going plus I am hoping to publish it this year. Yes it may bomb out as far as interest goes but I am meeting my own objectives, if amateurs are not willing to explore or go beyond the accepted way of thinking well to them it is a hobby .. If you do try to push the envelope then you will inevitably focus on thing that are not the norm. If you feel I should present them all to you in a take and not give aproach tough I tried that a few times on this group and experts like the Doctor and Shakespeare just wanted to laugh off the thought of any new ideas and more like minds jumped on the bandwaggon for a free laugh. This cruelty has happened many times before with other people...just think of the erudite members that we have lost in just the last two months which really doesn't matter to appliance operators but for me who is interested in the technical side.....well I miss them You ask for critical opinon of your ideaas but become angry when someone disagrees with you. Yes if I feel their attempt was dishonourable, I am English I can't think of running away. If this is the time for me to die then so be it but I will not be cowed. If you really think you have some kind of new break through put your money where yiur mouth is and demonstrate them or go join the free power bunch, they will love and embrace you and take your money..Well go and read my past patents some cost me money and some cost company money now you have an opportunity to do the walk instead of following the Doctor and Shakespeare over a cliff. Now you could turn on Yuri he has the guts to stand up for himself even if it apears that he is alone., Maybe he will be an easy target for you but I doubt it When I said 'peasants' I was refering to the likes of the Doctor and Richard hic Shakespeare who just love to attack people or complain they don't understand or a posting is so meaningless and of course Richard has placed nasty comments about pretty much everybody and he hasn't jumped on me yet ,but ofcourse the Doctor quickly got back on the net to do his thing. I don't know if I have ever responded to you before but if you think the hat was meant for or fitted you then I apologise. I do not intend to be nasty but I do not hesitate to respond in kind Best regards Art |
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