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multi-turn magnetic loops
I've seen several programs that will help you calculate the precise
dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve |
multi-turn magnetic loops
On Thu, 20 Nov 2008 19:47:24 -0800 (PST), Steve
wrote: However, none of these programs are written to cover the case of a two or more-turn loop. Hi Steve, For transmit, there's nothing to "gain" by it. Success generally floods the marketplace and few complain about not finding resources to make a knock-off. 73's Richard Clark, KB7QHC |
multi-turn magnetic loops
On Nov 20, 7:47*pm, Steve wrote:
I've seen several programs that will help you calculate the precise dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve Search for Reg Edwards programs. RJELOOP3 is probably what you want. I'm assuming here that you're talking about loops that are very small compared with a wavelength, which may offer advantages as receiving antennas for low frequencies. Cheers, Tom |
multi-turn magnetic loops
On 21 nov, 04:47, Steve wrote:
I've seen several programs that will help you calculate the precise dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve Hello Steve, You probably did some loop calculations and found that in a transmit case the voltage across the tuning capacitor is very high (and bandwidth is limited). Also for small loops, most input power is lost as heat due to copper resistance. When you make a two turn loop, the radiation resistance will increase with factor 4. So with half the current through the loop, the radiated power is same (as for a single turn loop). When the 2 turns of the loop are relative close together, the inductance increases with factor 4, hence the reactance. The current has been halved, but because of the reactance, the voltage across the tuning capacitance will be 2 times the value for the single turn loop with higher probability on corona effects. An advantage can be an almost 4 times smaller tuning capacitor. One may expect that the loss resistance due to heat of a two-turn inductor will be twice as high (w.r.t. single turn case). This is not true; the loss resistance will be more then twice as high because of proximity effect. The current will not equally distribute along the circumference of the tube/wire. So the efficiency of the loop will be less then twice as high (w.r.t. single turn case). When the turns are far apart (with respect to wire/tube diameter), inductance will not be 4 times higher and proximity effect will be less. You will get better performance than the single turn loop made of same diameter tube/wire. The result will be the same as when you place the two turns in parallel. Inductance will decrease somewhat (hence lower voltage across capacitor), AC resistance also, hence radiation efficiency). There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: 1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). Off course for the receive-only case, a multi turn loop can be helpful as you can use a smaller tuning capacitor. Best regards, Wim PA3DJS www.tetech.nl In case of PM, don't forget to remove abc. |
multi-turn magnetic loops
On Nov 21, 12:32*am, Richard Clark wrote:
On Thu, 20 Nov 2008 19:47:24 -0800 (PST), Steve wrote: However, none of these programs are written to cover the case of a two or more-turn loop. Hi Steve, For transmit, there's nothing to "gain" by it. Success generally floods the marketplace and few complain about not finding resources to make a knock-off. 73's Richard Clark, KB7QHC Yes, I know there's nothing to gain in terms of performance. However, I have very little space to work with. I have a 1 meter diameter loop installed in my (tiny) attic that works very respectably on 10-30 meters. It won't get me onto 40 meters, though, and getting onto 40 is either going to require a much larger diameter single-turn loop, a two- turn loop, or a much more robust capacitor. Trying out a two-turn loop seems like it would be the easiest and least expensive alternative, and I already have the copper tubing I would need. |
multi-turn magnetic loops
On Nov 21, 5:38*am, Wimpie wrote:
On 21 nov, 04:47, Steve wrote: I've seen several programs that will help you calculate the precise dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve Hello Steve, You probably did some loop calculations and found that in a transmit case the voltage across the tuning capacitor is very high (and bandwidth is limited). Also for small loops, most input power is lost as heat due to copper resistance. When you make a two turn loop, the radiation resistance will increase with factor 4. So with half the current through the loop, the radiated power is same (as for a single turn loop). *When the 2 turns of the loop are relative close together, the inductance increases with factor 4, hence the reactance. The current has been halved, but because of the reactance, the voltage across the tuning capacitance will be 2 times the value for the single turn loop with higher probability on corona effects. *An advantage can be an almost 4 times smaller tuning capacitor. One may expect that the loss resistance due to heat of a two-turn inductor will be twice as high (w.r.t. single turn case). This is not true; the loss resistance will be more then twice as high because of proximity effect. The current will not equally distribute along the circumference of the tube/wire. *So the efficiency of the loop will be less then twice as high (w.r.t. single turn case). When the turns are far apart (with respect to wire/tube diameter), inductance will not be 4 times higher and proximity effect will be less. You will get better performance than the single turn loop made of same diameter tube/wire. The result will be the same as when you place the two turns in parallel. Inductance will decrease somewhat (hence lower voltage across capacitor), AC resistance also, hence radiation efficiency). There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: *1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. * The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. *Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). Off course for the receive-only case, a multi turn loop can be helpful as you can use a smaller tuning capacitor. Best regards, Wim PA3DJSwww.tetech.nl In case of PM, don't forget to remove abc. Seems to me you are recommending the "?slinky" ! Is that correct? Art |
multi-turn magnetic loops
Art Unwin wrote:
... Seems to me you are recommending the "?slinky" ! Is that correct? Art I believe, he is speaking of rotating the flat surfaces of the conductor(s) 90 degrees to what a "slinkys'" orientation places them at. In which case, "mondo-capacitive loading to the 'environment'" is also introduced ... while minimizing capacitive loading between turns. Regards, JS |
multi-turn magnetic loops
On Nov 21, 9:52*am, John Smith wrote:
Art Unwin wrote: ... Seems to me you are recommending the "?slinky" ! Is that correct? Art I believe, he is speaking of rotating the flat surfaces of the conductor(s) 90 degrees to what a "slinkys'" orientation places them at. In which case, "mondo-capacitive loading to the 'environment'" is also introduced ... while minimizing capacitive loading between turns. Regards, JS Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel such that you have several wavelengths of wire helix style and no or repetitive points of none reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art |
multi-turn magnetic loops
On Fri, 21 Nov 2008 04:55:35 -0800 (PST), Steve
wrote: On Nov 21, 12:32*am, Richard Clark wrote: On Thu, 20 Nov 2008 19:47:24 -0800 (PST), Steve wrote: However, none of these programs are written to cover the case of a two or more-turn loop. Hi Steve, For transmit, there's nothing to "gain" by it. Success generally floods the marketplace and few complain about not finding resources to make a knock-off. 73's Richard Clark, KB7QHC Yes, I know there's nothing to gain in terms of performance. However, I have very little space to work with. I have a 1 meter diameter loop installed in my (tiny) attic that works very respectably on 10-30 meters. It won't get me onto 40 meters, though, and getting onto 40 is either going to require a much larger diameter single-turn loop, a two- turn loop, or a much more robust capacitor. Trying out a two-turn loop seems like it would be the easiest and least expensive alternative, and I already have the copper tubing I would need. Hi Steve, As offered by another corespondent here, the work of Reg Edwards revealed that a multiturn transmit loop, designed for "efficiency's sake" is never as efficient as a single turn loop. There are, of course, any number of alternative designs if you don't want efficiency. Many of those designs are touted here in this group - usually appended with hitherto unrealized advances the masters were never aware of. Usually, the longer the thread, the poorer the design. You have already recognized the significant variables you would have to attend to to go lower in frequency - it is not for the faint of heart and the Q keeps climbing. 73's Richard Clark, KB7QHC |
multi-turn magnetic loops
On Nov 21, 10:51*am, Art Unwin wrote:
On Nov 21, 9:52*am, John Smith wrote: Art Unwin wrote: ... Seems to me you are recommending the "?slinky" ! Is that correct? Art I believe, he is speaking of rotating the flat surfaces of the conductor(s) 90 degrees to what a "slinkys'" orientation places them at.. In which case, "mondo-capacitive loading to the 'environment'" is also introduced ... while minimizing capacitive loading between turns. Regards, JS Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left *hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel *such that you have several wavelengths of wire helix style and no or repetitive points of none *reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art I forgot to mention that a similar type radiator is shown in Antenna Applications Reference Guide by Johnson and Jasik with slight modification. This design was succeeded by the helix antenna to obtain circular polarization which is now universal with respect to space communications. The beauty of this design is the multiplicity of resonant points and the use of different frequencies. The economy of space is some what altered by the need of multi wavelength of wire because of slow wave.but then it enables axial directivity. There are many hams who are delighted by the slinky performance and they are still sold in huge numbers to the ham community, so it must be performing! Art Unwin |
multi-turn magnetic loops
On Nov 21, 2:00*pm, Art Unwin wrote:
On Nov 21, 10:51*am, Art Unwin wrote: On Nov 21, 9:52*am, John Smith wrote: Art Unwin wrote: ... Seems to me you are recommending the "?slinky" ! Is that correct? Art I believe, he is speaking of rotating the flat surfaces of the conductor(s) 90 degrees to what a "slinkys'" orientation places them at. In which case, "mondo-capacitive loading to the 'environment'" is also introduced ... while minimizing capacitive loading between turns. Regards, JS Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left *hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel *such that you have several wavelengths of wire helix style and no or repetitive points of none *reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art I forgot to mention that a similar type radiator is shown in Antenna Applications Reference Guide by Johnson and Jasik with slight modification. This design was succeeded by the helix antenna to obtain circular polarization which is now universal with respect to space communications. The beauty of this design is the multiplicity of resonant points and the use of different frequencies. *The economy of space is some what altered by the need of multi wavelength of wire because of slow wave.but then it enables axial directivity. There are many hams who are delighted by the slinky performance and they are still sold in huge numbers to the ham community, so it must be performing! Art Unwin- Hide quoted text - - Show quoted text - Art, where did you get the idea a slinky had "axial directivity" at 40M. I hazard a guess that it was from reading about helix antennas. The axial radiation is only true if the diameter of the helix is fairly large, on the order of 1/pi wavelength usually. This would be a huge antenna if designed for the frequency(40M) that the OP was asking. I can see how this misunderstanding led you to your shoebox antenna.design. Gee I hope you arent spending good money filing for a patent on that thing. I understand that can cost a couple of thousand these days. However it would be interesting to see you get it. Jimmie |
multi-turn magnetic loops
On Nov 21, 3:00*pm, JIMMIE wrote:
On Nov 21, 2:00*pm, Art Unwin wrote: On Nov 21, 10:51*am, Art Unwin wrote: On Nov 21, 9:52*am, John Smith wrote: Art Unwin wrote: ... Seems to me you are recommending the "?slinky" ! Is that correct? Art I believe, he is speaking of rotating the flat surfaces of the conductor(s) 90 degrees to what a "slinkys'" orientation places them at. In which case, "mondo-capacitive loading to the 'environment'" is also introduced ... while minimizing capacitive loading between turns. Regards, JS Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left *hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel *such that you have several wavelengths of wire helix style and no or repetitive points of none *reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art I forgot to mention that a similar type radiator is shown in Antenna Applications Reference Guide by Johnson and Jasik with slight modification. This design was succeeded by the helix antenna to obtain circular polarization which is now universal with respect to space communications. The beauty of this design is the multiplicity of resonant points and the use of different frequencies. *The economy of space is some what altered by the need of multi wavelength of wire because of slow wave.but then it enables axial directivity. There are many hams who are delighted by the slinky performance and they are still sold in huge numbers to the ham community, so it must be performing! Art Unwin- Hide quoted text - - Show quoted text - Art, where did you get the idea a slinky had "axial directivity" at 40M. I hazard a guess that it was from reading about helix antennas. The axial radiation is only true if the diameter of the helix is fairly large, on the order of 1/pi wavelength usually. This would be a huge antenna if designed for the frequency(40M) that the OP was asking. I can see how this misunderstanding led you to your shoebox antenna.design. Gee I hope you arent spending good money filing for a patent on that thing. I understand that can cost a couple of thousand these days. However it would be interesting to see you get it. Jimmie Jimmie The diameter of the helix and the pitch of the helix is only a couple of terms that Krauss applied to a helix antenna which is not in equilibrium. He also assumed too much when he assigned more gain to a helix that could be attained by a antenna not in equilibrium which I strongly suspect is the belief he had in the displacement current. Krauss did a lot of pioneering work but the passage of time have pointed to many errors. If a helix winding wire is less than a couple of wavelengths then the radiation will be at right angle to the axis. If the wire length is above two WL preferably 7-10 WL the radiation peak will be axial regardless of the diameter or helix angle as long as the radiator is in a state of equiulibrium. the law that I continually state from the extension of the Gaussian law of statics which I derived. Wind two inductors with a common wire but wound in opposite directions and view with MFJ 259 or alternatively review ARRL publications where they show a fully wound dipole and then start thinking for yourself instead of jumping to unfounded conclusions. I also read that the reason that the EH antenna and the cross field antenna does not work as expected because they were founded in part on the non existant displacement current b ut I have not followed up on that from first principles so it is just a statement Art |
multi-turn magnetic loops
Art Unwin wrote:
... Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel such that you have several wavelengths of wire helix style and no or repetitive points of none reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art Art: The way I "read" him is, he now has a 1m loop, SINGLE TURN (equiv. to resonating a 8-12+ ft. whip on the hf bands?) able to do 10-30m--with WHATEVER "matchbox" he is choosing to run ... he is contemplating on adding a second 1m turn (to add 40m capabilities, apparently) ... are we on the same page? ... and, loops are NEVER omni-directional! Well, other than one constructed to radiate/receive in the plane of the loop and run in a horizontal plane, would, perhaps, do some type of omni-horizontal-polarization?--and a 1m at 10-30m, it ain't such an animal! (well, maybe-kinda-sorta, but I DON'T KNOW! I would have to get hands-on-experience before trusting a ventured reply ... any books I have ever laid hands on are vague on all this ... ) Personally, the only time I have ever used a loop is for AM broadcast radio and direction finding (fox hunts) in the 10 to 2m bands, and, I did NOT want omni capabilities! ... well, there may have been one or two--but so long ago they escape memory ... I never did "like them." Or, in other words, I am NOT a "loop guru" ... :-( Anyway, after all that verbiage, the cut-to-the-chase: "I would think a slinky and what he has are two 'different species'." Regards, JS |
multi-turn magnetic loops
"Art Unwin" wrote in message ... the law that I continually state from the extension of the Gaussian law of statics which I derived. you haven't presented anything that you derived... state the equation. |
multi-turn magnetic loops
On Nov 21, 3:50*pm, John Smith wrote:
Art Unwin wrote: ... Wouldn't that take more room than a slinky per turn? His attic is very small!.I think he would be much better placing the turns as close together as possible to obtain axial directivity. The only mod required to the slinky is to ensure the number of right hand turn loop are equal to the number of left *hand turned loops. Feed could still be at the center and depending on the amount of wire used it would radiate like a dipole or axially. What this does is cancel the lumped loads created in manufacture which Wim suggests is a problem ie the two supposedly lumped loads will cancel *such that you have several wavelengths of wire helix style and no or repetitive points of none *reactive impedances. He could ofcourse place the windings in a vertical direction to obtain an omnidirectional pattern and utilise the available room to a maximum. A lot depends on what frequencies he wishes to use as to what form the radiator becomes. Best regards Art Art: The way I "read" him is, he now has a 1m loop, SINGLE TURN (equiv. to resonating a 8-12+ ft. whip on the hf bands?) able to do 10-30m--with WHATEVER "matchbox" he is choosing to run ... he is contemplating on adding a second 1m turn (to add 40m capabilities, apparently) ... are we on the same page? ... and, loops are NEVER omni-directional! *Well, other than one constructed to radiate/receive in the plane of the loop and run in a horizontal plane, would, perhaps, do some type of omni-horizontal-polarization?--and a 1m at 10-30m, it ain't such an animal! (well, maybe-kinda-sorta, but I DON'T KNOW! *I would have to get hands-on-experience before trusting a ventured reply ... any books I have ever laid hands on are vague on all this ... ) Personally, the only time I have ever used a loop is for AM broadcast radio and direction finding (fox hunts) in the 10 to 2m bands, and, I did NOT want omni capabilities! ... well, there may have been one or two--but so long ago they escape memory ... I never did "like them." Or, in other words, I am NOT a "loop guru" ... :-( Anyway, after all that verbiage, the cut-to-the-chase: *"I would think a slinky and what he has are two 'different species'." Regards, JS I stated Slinky only because I thought that was what Wim was proposing and then went from there If the poster now has a loop without a capacitor that is resonant on 40M then a second loop wound in the opposite direction when added to the other loop. If he is adding a lumped load in the form of a capaciter then all bets are off as Maxwell doesn't entertain lumped loads in his equations. Art |
multi-turn magnetic loops
Art Unwin wrote:
... If the poster now has a loop without a capacitor that is resonant on 40M then a second loop wound in the opposite direction when added to the other loop. If he is adding a lumped load in the form of a capaciter then all bets are off as Maxwell doesn't entertain lumped loads in his equations. Art What? You can't read/think? I don't believe he said anything near that ... indeed, I took for granted he said something almost opposite to what you "intuit" with you, apparent, psychic powers? Did you evoke or invoke all these visions? Regards, JS |
multi-turn magnetic loops
Art Unwin wrote:
... If the poster now has a loop without a capacitor that is resonant on 40M then a second loop wound in the opposite direction when added to the other loop. If he is adding a lumped load in the form of a capaciter then all bets are off as Maxwell doesn't entertain lumped loads in his equations. Art What? You can't read/think? I don't believe he said anything near that ... indeed, I took for granted he said something almost opposite to what you "intuit" with your, apparent, psychic powers? Did you evoke or invoke all these visions? Regards, JS |
multi-turn magnetic loops
On 21 nov, 16:44, Art Unwin wrote:
On Nov 21, 5:38*am, Wimpie wrote: On 21 nov, 04:47, Steve wrote: I've seen several programs that will help you calculate the precise dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve Hello Steve, You probably did some loop calculations and found that in a transmit case the voltage across the tuning capacitor is very high (and bandwidth is limited). Also for small loops, most input power is lost as heat due to copper resistance. When you make a two turn loop, the radiation resistance will increase with factor 4. So with half the current through the loop, the radiated power is same (as for a single turn loop). *When the 2 turns of the loop are relative close together, the inductance increases with factor 4, hence the reactance. The current has been halved, but because of the reactance, the voltage across the tuning capacitance will be 2 times the value for the single turn loop with higher probability on corona effects. *An advantage can be an almost 4 times smaller tuning capacitor. One may expect that the loss resistance due to heat of a two-turn inductor will be twice as high (w.r.t. single turn case). This is not true; the loss resistance will be more then twice as high because of proximity effect. The current will not equally distribute along the circumference of the tube/wire. *So the efficiency of the loop will be less then twice as high (w.r.t. single turn case). When the turns are far apart (with respect to wire/tube diameter), inductance will not be 4 times higher and proximity effect will be less. You will get better performance than the single turn loop made of same diameter tube/wire. The result will be the same as when you place the two turns in parallel. Inductance will decrease somewhat (hence lower voltage across capacitor), AC resistance also, hence radiation efficiency). There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: *1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. * The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. *Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). Off course for the receive-only case, a multi turn loop can be helpful as you can use a smaller tuning capacitor. Best regards, Wim PA3DJSwww.tetech.nl In case of PM, don't forget to remove abc. Seems to me you are recommending the "?slinky" ! Is that correct? Art Sorry Art, I am not talking about a slinky. I am just talking about a multi turn (2 turns) loop where overall wire length is 0.25 lambda so you can assume that current in wire is constant along the length. It must be tuned by external capacitance. Regarding the strip. When you take a 3.14m long 20cm wide thin copper strip and make a loop of it (1m diameter), it will have a better efficiency then when you take 6.28m copper tubing with Dtube=2cm and make a two-turn loop (Dloop=1m, turns 18 cm apart). In the strip case, the current has more circumference to flow (40cm) instead of 6.28cm for the copper tubing. AC resistance of copper tubing will be about 10 times higher. Off course, current in two-turn loop will be half (for same radiated power), but still heat losses will be 10*0.5^2=2.5 times higher (for the two-turn loop). When both loops have good efficiency (so radiation resistance dominates), the strip loop will have better bandwidth as flux path is longer and therefore results in less inductance. I hope this clarifies my posting. Best regards, Wim PA3DJS Please remove abc in case of PM. |
multi-turn magnetic loops
On Nov 21, 4:07*pm, "Dave" wrote:
"Art Unwin" wrote in message ... the law that I continually state from the extension of the Gaussian law of statics which I derived. you haven't presented anything that you derived... state the equation. Oh come on David I do not work for you, do it for yourself as you have a superior background than I do. If you are proficient in mathematics check out the addition of displacement current of Maxwell and review it as just that. a current in circular foirm that DOES generate a displacement magnetic field such that it displaces a charged particle from the surface of the radiator. This eddy current has the units of current which somehow would match the description of the "weak force:". Maybe the other masters needed to include this same addition If your math is up to it why not check that out? You stated previously that you wanted to know where the weak current equation is so, now you can start on a series of removal or added equation to all the formulas supplied to Maxwell by previous masters and determine for yourself,. The correct units are there so that all equations jive with each other sfter manipulating the supplied laws. Stae equation you ask? A radiator can be any shape, size or elevation when providing the maximum radiation as long as it is in equilibrium. I believe that the helix goes along way in supporting that statement which comes from changing a static field to a dynamic field and confirmed by existing antenna programs based ion Maxwell';s work. Ofcourse you can declare antenna computer programs are in error and salvage your credability or place such a statement in the practicable book that you are writing! After all if it is printed in a book it must be right.......right? Art Unwin KB9MZ.......XG....(UK)( |
multi-turn magnetic loops
On Nov 21, 5:10*pm, John Smith wrote:
Art Unwin wrote: * ... If the poster now has a loop without a capacitor that is resonant on 40M then a second loop wound in the opposite direction when added to the other loop. If he is adding a lumped load in the form *of a capaciter then all bets are off as Maxwell doesn't entertain lumped loads in his equations. Art What? *You can't read/think? I don't believe he said anything near that ... indeed, I took for granted he said something almost opposite to what you "intuit" with you, apparent, psychic powers? Did you evoke or invoke all these visions? Regards, JS Maybe I was to quick in replying. Hope I haven't ruined your week end. My car battery went down so I filled it with distilled water and tried to charge it But the meter on the charger is not working/moving so I am not sure if it is charging, Strike the two charger together and get a spark but the weather is below freezing Don't know what to do now. I am confused Maybe the water is frozen |
multi-turn magnetic loops
Wimpie wrote:
. . . There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: 1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). . . . Flat conductors aren't as attractive as they look at first glance. The problem is the same proximity effect mentioned earlier in the posting. Current is distributed evenly around a round conductor (assuming the perimeter is a very small fraction of a wavelength), but not along a flat strip. Because of proximity effect, the current is much more concentrated near the edges than at the middle. The result is that the resistance is considerably higher than for a wire with the same surface area. In figuring an "equivalent diameter" of a thin flat strip in order to get the same L and C properties, the rule is that a strip is equivalent to a wire whose diameter is half the strip width. This means that a strip of width w or total "circumference" 2 * w is equivalent to a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C go. Since the same phenomenon affects the inductance and resistance, this would also be a good working rule for estimating the relative R of a strip or wire. Roy Lewallen, W7EL |
multi-turn magnetic loops
On Nov 21, 5:18*pm, Wimpie wrote:
On 21 nov, 16:44, Art Unwin wrote: On Nov 21, 5:38*am, Wimpie wrote: On 21 nov, 04:47, Steve wrote: I've seen several programs that will help you calculate the precise dimensions of a single-turn loop, given the composition of the radiating element, its thickness, and so on. However, none of these programs are written to cover the case of a two or more-turn loop. Does anyone know of a program that will offer guidance in the construction of a two or more-turn loop? Thanks, Steve Hello Steve, You probably did some loop calculations and found that in a transmit case the voltage across the tuning capacitor is very high (and bandwidth is limited). Also for small loops, most input power is lost as heat due to copper resistance. When you make a two turn loop, the radiation resistance will increase with factor 4. So with half the current through the loop, the radiated power is same (as for a single turn loop). *When the 2 turns of the loop are relative close together, the inductance increases with factor 4, hence the reactance. The current has been halved, but because of the reactance, the voltage across the tuning capacitance will be 2 times the value for the single turn loop with higher probability on corona effects. *An advantage can be an almost 4 times smaller tuning capacitor. One may expect that the loss resistance due to heat of a two-turn inductor will be twice as high (w.r.t. single turn case). This is not true; the loss resistance will be more then twice as high because of proximity effect. The current will not equally distribute along the circumference of the tube/wire. *So the efficiency of the loop will be less then twice as high (w.r.t. single turn case). When the turns are far apart (with respect to wire/tube diameter), inductance will not be 4 times higher and proximity effect will be less. You will get better performance than the single turn loop made of same diameter tube/wire. The result will be the same as when you place the two turns in parallel. Inductance will decrease somewhat (hence lower voltage across capacitor), AC resistance also, hence radiation efficiency). There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: *1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. * The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. *Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). Off course for the receive-only case, a multi turn loop can be helpful as you can use a smaller tuning capacitor. Best regards, Wim PA3DJSwww.tetech.nl In case of PM, don't forget to remove abc. Seems to me you are recommending the "?slinky" ! Is that correct? Art Sorry Art, I am not talking about a slinky. I am just talking about a multi turn (2 turns) loop where overall wire length is 0.25 lambda so you can assume that current in wire is constant along the length. It must be tuned by external capacitance. Regarding the strip. When you take a 3.14m long 20cm wide thin copper strip and make a loop of it (1m diameter), it will have a better efficiency then when you take 6.28m *copper tubing with Dtube=2cm and make a two-turn loop (Dloop=1m, turns 18 cm apart). In the strip case, the current has more circumference to flow (40cm) instead of 6.28cm for the copper tubing. *AC resistance of copper tubing will be about 10 times higher. Off course, current in two-turn loop will be half (for same radiated power), but still heat losses will be 10*0.5^2=2.5 times higher (for the two-turn loop). When both loops have good efficiency (so radiation resistance dominates), the strip loop will have better bandwidth as flux path is longer and therefore results in less inductance. I hope this clarifies my posting. Best regards, Wim PA3DJS Please remove abc in case of PM. I think I am missing something Wim. A slinky has a strip winding that is edge wound which provides the largest disparity between the inside radius and the outside radius. On one of the top transmitters the inductance winding is such that the inner radius is close to the outside radius. Naturally the different pitch of the windings is very different as is the inter coil capacitance. As Roy stated charges accumulate on sharp edges which I see as correct but I cannot see how that alteres the diference all that much as the same clearance is required So in the final analysis for less inductance which form is which., the longer inductance or the shorter inductance on the assumption that the number of turns are similara nd I can acceptt your word for it? I referred to a slinky purely to emphasize the importance of reverse windings so that lumped loadings applied are cancelled. Actually the modern slinky is not contra wound for some reason but I assume that is for the novelty movement reasons for children and not because of radiation reasons. The slinky patent is now defunct if that matters and iI am assuming that the fed would be centre fed. Thank you so much for responding Best regards Art |
multi-turn magnetic loops
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multi-turn magnetic loops
On Fri, 21 Nov 2008 18:24:20 -0800, Roy Lewallen
wrote: Flat conductors aren't as attractive as they look at first glance. The problem is the same proximity effect mentioned earlier in the posting. Current is distributed evenly around a round conductor (assuming the perimeter is a very small fraction of a wavelength), but not along a flat strip. Because of proximity effect, the current is much more concentrated near the edges than at the middle. The result is that the resistance is considerably higher than for a wire with the same surface area. In figuring an "equivalent diameter" of a thin flat strip in order to get the same L and C properties, the rule is that a strip is equivalent to a wire whose diameter is half the strip width. This means that a strip of width w or total "circumference" 2 * w is equivalent to a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C go. Since the same phenomenon affects the inductance and resistance, this would also be a good working rule for estimating the relative R of a strip or wire. Roy Lewallen, W7EL Thanks. I think you just explained the cause of a problem I fought in about 1980. I had "designed" a 930MHz yagi antenna for a utility telemetry system. In order to cut system costs, I decided to build the antenna from stamped 0.062" aluminum. My initial dimensions were stolen from a Scala yagi which used approximately 0.500" diameter round rods for elements. I reasoned that to obtain the same bandwidth, I would need to use the same circumference as the rod. That made the initial prototypes elements 0.8" wide. After some tweaking, the antenna tuned to the correct center frequency, but the 2:1 VSWR bandwidth was much less than the original Scala antenna. So, I increased the width of the stamped elements (with aluminum duct tape) until the bandwidth improved. I landed at 1.25" or 2.5 times the width of the rod elements, somewhat larger than the recommended 2.0 times the rod diameter. However, when I added a coined stiffener groove to the stamped "boom" and elements, the bandwidth increased again, to much more than necessary. After the usual all night cut-n-try session, I landed on 2.0 times the width of the rod elements, with the coined stiffeners, which apparently increased the effective diameter of the elements. Coining the "boom" also wrecked all the element tuning since it increases their effective end to end length by the depth of the coining. I had a hell of a time dealing with the sheet metal vendor, trying to control the stiffener dimensions. It seems that aluminum stretches when coined, often in a rather unpredictable manner. I eventually gave up and went to 0.125" sheet aluminum and no stiffeners. Unfortunately, only a handful of prototypes were made and shipped, so I have no clue as to how well (or badly) they worked in the field. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
multi-turn magnetic loops
On 22 nov, 03:24, Roy Lewallen wrote:
Wimpie wrote: . . . There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: *1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. * The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. *Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). . . . Flat conductors aren't as attractive as they look at first glance. The problem is the same proximity effect mentioned earlier in the posting. Current is distributed evenly around a round conductor (assuming the perimeter is a very small fraction of a wavelength), but not along a flat strip. Because of proximity effect, the current is much more concentrated near the edges than at the middle. The result is that the resistance is considerably higher than for a wire with the same surface area. In figuring an "equivalent diameter" of a thin flat strip in order to get the same L and C properties, the rule is that a strip is equivalent to a wire whose diameter is half the strip width. This means that a strip of width w or total "circumference" 2 * w is equivalent to a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C go. Since the same phenomenon affects the inductance and resistance, this would also be a good working rule for estimating the relative R of a strip or wire. Roy Lewallen, W7EL Hello Roy, You are right regarding non-uniformity, losses in the flat strip are higher then based on the uniform current distribution (because of non- uniformity). But this does not declassify loop antennas out of strip material. Based on a uniform current distribution (20cm wide strip versus two- turn loop from tube with D=2cm) one would expect heat loss reduction of 3.2. In my posting on Art's comment a mentioned heat loss reduction w.r.t. the 2-turn loop of factor 2.5 (to account for non-uniformity). A strip (not near to other constructions) has effective diameter of half the width to have same characteristic impedance (as you mentioned). So a strip with physical circumference of 40cm (width = 20cm) has an effective circumference of 40*0.785=31.4cm. You need to have tube with D=10cm to have same effective circumference. I agree with you that this effective circumference is also a good starting point for calculation of AC loss resistance. When Dloop is no longer large with respect to Dtube, current in the tube tends to take the shortest path, hence reducing effective diameter (and loop area) of the loop. In case of the strip, effective diameter (hence area) does not reduce. Radiation resistance is proportional to A^2 (for electrically small loops), hence Dloop^4. 10% reduction on loop diameter, gives 34% reduction of radiation resistance. In my opinion, advantage of a strip is still significant with respect to a tube as long as you use a strip with width 2*(tube diameter). Best regards, Wim PA3DJS www.tetech.nl you can use PM, but please remove abc. |
multi-turn magnetic loops
"Art Unwin" wrote in message ... On Nov 21, 4:07 pm, "Dave" wrote: "Art Unwin" wrote in message ... the law that I continually state from the extension of the Gaussian law of statics which I derived. you haven't presented anything that you derived... state the equation. Oh come on David I do not work for you, do it for yourself as you have superior background than I do. finally he got something right! If you are proficient in mathematics check out the addition of displacement current of Maxwell and review it as just that. it works fine for me as is... no weak force, no magic levitating neutrinos, just a displacement current. a current in circular foirm that DOES generate a displacement magnetic field such that it displaces a charged particle from the surface of the radiator. bull! This eddy current has the units of current which somehow would match the description of the "weak force:". eddy currents don't require weak force, nor displacement currents, they are perfectly well described by existing magnetic field and conduction equations. You stated previously that you wanted to know where the weak current equation is so, now you can start on a series not me, i know where the weak 'force' is, and it has nothing to do with electrical currents even though it is sometimes refered to as the electro-weak force. that is a throwback to a VERY short time after the big bang when the forces were merged, right now, unless you are experimenting with a supercollider you can ignore the weak force as far as electric fields are concerned. Stae equation you ask? handwaving bs snipped yes, state your equation that you 'derived'. Ofcourse you can declare antenna computer programs are in error and salvage your credability or place such a statement in the practicable book that you are writing! After all if it is printed in a book it must be right.......right? but the computer programs that exist today, and DON'T use the weak force in anyway are perfectly in tune with maxwell's equations. and my book doesn't mention them at all, so don't hold your breath for that. |
multi-turn magnetic loops
On Nov 22, 9:32*am, "Dave" wrote:
"Art Unwin" wrote in message ... On Nov 21, 4:07 pm, "Dave" wrote: "Art Unwin" wrote in message .... the law that I continually state from the extension of the Gaussian law of statics which I derived. you haven't presented anything that you derived... state the equation. Oh come on David I do not work for you, do it for yourself as you have superior background than I do. finally he got something right! If you are proficient in mathematics check out the addition of displacement current of Maxwell and review it as just that. it works fine for me as is... no weak force, no magic levitating neutrinos, just a displacement current. a current in circular foirm that DOES generate a displacement magnetic field such that it displaces a charged particle from the surface of the radiator. bull! This eddy current has the units of current which somehow would match the description of the "weak force:". eddy currents don't require weak force, nor displacement currents, they are perfectly well described by existing magnetic field and conduction equations. You stated previously that you wanted to know where the weak current equation is so, now you can start on a series not me, i know where the weak 'force' is, and it has nothing to do with electrical currents even though it is sometimes refered to as the electro-weak force. *that is a throwback to a VERY short time after the big bang when the forces were merged, right now, unless you are experimenting with a supercollider you can ignore the weak force as far as electric fields are concerned. Stae equation you ask? handwaving bs snipped yes, state your equation that you 'derived'. Ofcourse you can declare antenna computer programs are in error and salvage your credability or place such a statement in the practicable book that you are writing! After all if it is printed in a book it must be right.......right? but the computer programs that exist today, and DON'T use the weak force in anyway are perfectly in tune with maxwell's equations. *and my book doesn't mention them at all, so don't hold your breath for that. You must be older than I thought, you never are going to change. Before you fade away this last bit that you are now supporting regarding the weak force. Can you account for every action that reside in Maxwells laws including his addition? Can you state that without doubt that eddy currents do not exist during radiation? Or more importantly, that Maxwell's laws also omit the presence of the eddy current? Are you still of the opinion that radiation is a wave which implies a string of connected energies instead of individual particle ejection? Then pray tell me how exactly does the transmition of communication eminate from a radiator and do a reverse action in the transportation of intelligence? And then comes the biggy, How does the Universe exist without being in equilibrium a term you resist with abandon. Your knee jerk reactions to me are starting to be absurd but as you are unemployed you do not need now to answer to anybody regarding the thoughts of an old man or concern yourself of the possibility of being fired. Art |
multi-turn magnetic loops
"Art Unwin" wrote in message ... this last bit that you are now supporting regarding the weak force. Can you account for every action that reside in Maxwells laws including his addition? yes Can you state that without doubt that eddy currents do not exist during radiation? Or more importantly, that Maxwell's laws also omit the presence of the eddy current? where did you ever get this idea. eddy current are currents in a conductor caused by exposure to an electromagnetic field. of course they are covered by maxwell's equations. you just have to use the proper boundry conditions and permeability/conductivity of the conductor to account for them. i have written software that modeled eddy currents from fields set up by power transformers, every equation was out of a standard text book. Are you still of the opinion that radiation is a wave which implies a string of connected energies instead of individual particle ejection? yes, particle ejection, your magical levitating diamagnetic neutrino theory, is not necessary for electromagnetic propagation. Then pray tell me how exactly does the transmition of communication eminate from a radiator and do a reverse action in the transportation of intelligence? energy my dear man, energy is conveyed by the electromagnetic waves and hence can carry intelligence... as opposed to what goes on between your ears, which must be quite a vaccuum. And then comes the biggy, How does the Universe exist without being in equilibrium a term you resist with abandon. i abandoned equilibrium long ago. it is neither necessary nor desirable for any possible use of electromagnetic propagation that i want to make use of. if everything were in equilibrium the universe would be dead, it takes energy moving from here to there to make everything work. without flowing energy, hence non-equilibrium, nothing would exist... much like the space between your ears, maybe that is the problem, you brain has reached equilibrium with the outside world, hence nothing can flow in... though that doesn't explain the outpouring of bafflegab. Your knee jerk reactions to me are starting to be absurd but as you are unemployed you do not need now to answer to anybody regarding the thoughts of an old man or concern yourself of the possibility of being fired. my reactions to your are pure humor. i love the pure illogic of your writings, reminds me of some old science fiction stuff by writers who didn't care if their proposals made any physical sense in this universe. perhaps that would be a good line of work for you art, you could write science fiction in the 'alternate universe' genre. maybe there you could come up with a story line that would make use of your distorted physics. and no, i am gainfully employed, someone has to contribute to the welfare system so you can collect your checks. |
multi-turn magnetic loops
On Nov 22, 11:59*am, "Dave" wrote:
"Art Unwin" wrote in message ... this last bit that you are now supporting regarding the weak force. Can you account for every action that reside in Maxwells laws including his addition? yes Can you state that without doubt that eddy currents do not exist during radiation? Or more importantly, that Maxwell's laws also omit the presence of the eddy current? where did you ever get this idea. *eddy current are currents in a conductor caused by exposure to an electromagnetic field. *of course they are covered by maxwell's equations. *you just have to use the proper boundry conditions and permeability/conductivity of the conductor to account for them. *i have written software that modeled eddy currents from fields set up by power transformers, every equation was out of a standard text book. Are you still of the opinion that radiation is a wave which implies a string of connected energies instead of individual particle ejection? yes, particle ejection, your magical levitating diamagnetic neutrino theory, is not necessary for electromagnetic propagation. Then pray tell me how exactly does the transmition of communication eminate from a radiator and do a reverse action *in the transportation of intelligence? energy my dear man, energy is conveyed by the electromagnetic waves and hence can carry intelligence... as opposed to what goes on between your ears, which must be quite a vaccuum. And then comes the biggy, How does the Universe exist without being in equilibrium a term you resist with abandon. i abandoned equilibrium long ago. *it is neither necessary nor desirable for any possible use of electromagnetic propagation that i want to make use of. if everything were in equilibrium the universe would be dead, it takes energy moving from here to there to make everything work. *without flowing energy, hence non-equilibrium, nothing would exist... much like the space between your ears, maybe that is the problem, you brain has reached equilibrium with the outside world, hence nothing can flow in... though that doesn't explain the outpouring of bafflegab. Your knee jerk reactions to me are starting to be absurd but as you are unemployed you do not need now to answer to anybody regarding the thoughts of an old man or concern yourself of the possibility of being fired. my reactions to your are pure humor. *i love the pure illogic of your writings, reminds me of some old science fiction stuff by writers who didn't care if their proposals made any physical sense in this universe. *perhaps that would be a good line of work for you art, you could write science fiction in the 'alternate universe' genre. *maybe there you could come up with a story line that would make use of your distorted physics. *and no, i am gainfully employed, someone has to contribute to the welfare system so you can collect your checks. Well your background on this subject is far superior to mine so you have the last word and I must wander off to ponder my silly ideas. It was several years ago that I brought up the subject of pulses with respect to the tank circuit and the propersition that current flows thru the center of a radiator that was not in equilibrium. When you banish the idea of equilibrium I have nothing left to support what I say such that I have now reached the Rubicon which requires me to succumb to the teachings of books and abolishion of all personal thought and reasoning. Fortinately I am retired and thus cannot be fired or put to death on account of my personal thoughts so in my own little world I can still continue in what I am doing except with regard to sharing or suggesting change which on this group is a impenatrational barrier. It was fun for a while but as I stated you have the last word. Now await my next posting on a different subject! Regards Art |
multi-turn magnetic loops
"Steve" wrote in message ... On Nov 21, 12:32 am, Richard Clark wrote: On Thu, 20 Nov 2008 19:47:24 -0800 (PST), Steve wrote: However, none of these programs are written to cover the case of a two or more-turn loop. Hi Steve, For transmit, there's nothing to "gain" by it. Success generally floods the marketplace and few complain about not finding resources to make a knock-off. 73's Richard Clark, KB7QHC Yes, I know there's nothing to gain in terms of performance. However, I have very little space to work with. I have a 1 meter diameter loop installed in my (tiny) attic that works very respectably on 10-30 meters. It won't get me onto 40 meters, though, and getting onto 40 is either going to require a much larger diameter single-turn loop, a two- turn loop, or a much more robust capacitor. Trying out a two-turn loop seems like it would be the easiest and least expensive alternative, and I already have the copper tubing I would need. Two 1m dia turns will cover 40 with the same variable capacitor, I think that is all you wanted to know!!! Experiment ... Lee ... G6ZSG ... |
Loop efficiency, was multi-turn magnetic loops
Steve wrote:
Yes, I know there's nothing to gain in terms of performance. However, I have very little space to work with. I have a 1 meter diameter loop installed in my (tiny) attic that works very respectably on 10-30 meters. It won't get me onto 40 meters, though, and getting onto 40 is either going to require a much larger diameter single-turn loop, a two- turn loop, or a much more robust capacitor. Trying out a two-turn loop seems like it would be the easiest and least expensive alternative, and I already have the copper tubing I would need. I separated this out from the noise floor...... When I was dealing with a loop, I wanted to extend the frequency downwards - it's a pretty big loop, but trying to hit 75 meters was a goal, I had some exchanges with Reg, and he pretty much told me to put a extra capacitor across the terminals so I could tune it to the lower frequency. That was a smack the forehead moment for me. And Oh yes, tuning will be sooooooo tight. But the cap will probably be better than an extra loop. You'll just have to figure out how to switch it in and out of the circuit. - 73 de Mike N3LI - |
Loop efficiency, was multi-turn magnetic loops
On Mon, 24 Nov 2008 16:56:45 -0500, Michael Coslo
wrote: But the cap will probably be better than an extra loop. You'll just have to figure out how to switch it in and out of the circuit. Hi Mike, More the achievement would be finding the capacitor that could carry the current. Did you follow through with this frequency extension of your loop? 73's Richard Clark, KB7QHC |
coils?multi-turn magnetic loops
In article ,
Roy Lewallen wrote: Wimpie wrote: . . . There is an "however". When you make a single turn loop from flat strip that has the same width as the length of your two-turn loop, you will notice: 1. reduced AC resistance (because of the significantly larger circumference of the flat strip with respect to a thin round tube, 2. inductance will decrease (H field lines have to take a longer path around the wide strip), 3. radiation resistance will not change with respect to a single turn loop from wire/tube. This results in higher efficiency and increased bandwidth. The overall result will be better then for your two-turn loop. I think that is the reason why most programs are for single turn loops. So for the transmit case, given fixed diameter of your loop, the larger the copper surface (=length*circumference), the better the efficiency. Best thing to enhance conductor surface is to use very wide flat strip (high wind load), or multiple wires (with some spacing in between) in parallel (limited wind load). . . . Flat conductors aren't as attractive as they look at first glance. The problem is the same proximity effect mentioned earlier in the posting. Current is distributed evenly around a round conductor (assuming the perimeter is a very small fraction of a wavelength), but not along a flat strip. Because of proximity effect, the current is much more concentrated near the edges than at the middle. The result is that the resistance is considerably higher than for a wire with the same surface area. In figuring an "equivalent diameter" of a thin flat strip in order to get the same L and C properties, the rule is that a strip is equivalent to a wire whose diameter is half the strip width. This means that a strip of width w or total "circumference" 2 * w is equivalent to a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C go. Since the same phenomenon affects the inductance and resistance, this would also be a good working rule for estimating the relative R of a strip or wire. Roy Lewallen, W7EL does this rule also hold true for example i've opened some tuners and linear amps, often, i see straps instead of wire going to the larger coils and switches, even some switch box's have straps from relays to connectors etc would wire have been 'better' and or avoid the proximity effect?? |
coils?multi-turn magnetic loops
ml wrote:
does this rule also hold true for example i've opened some tuners and linear amps, often, i see straps instead of wire going to the larger coils and switches, even some switch box's have straps from relays to connectors etc would wire have been 'better' and or avoid the proximity effect?? Proximity effect isn't a factor unless conductors are very close together -- I suggest you review the previous postings which explain it. As far as "better", the answer is that it probably doesn't matter, since either a wire or strap can usually be pretty easily made large enough to make loss negligible in those applications. Roy Lewallen, W7EL |
coils?multi-turn magnetic loops
Roy Lewallen wrote:
ml wrote: does this rule also hold true for example i've opened some tuners and linear amps, often, i see straps instead of wire going to the larger coils and switches, even some switch box's have straps from relays to connectors etc would wire have been 'better' and or avoid the proximity effect?? Proximity effect isn't a factor unless conductors are very close together -- I suggest you review the previous postings which explain it. As far as "better", the answer is that it probably doesn't matter, since either a wire or strap can usually be pretty easily made large enough to make loss negligible in those applications. Roy Lewallen, W7EL Proximity effect is when you are too close to a directional microphone and the bass is accentuated. I think you mean mutual coupling. |
coils?multi-turn magnetic loops
On Nov 25, 5:53*am, Dave wrote:
Roy Lewallen wrote: ml wrote: does this *rule also hold true * for example i've opened some *tuners and linear amps, *often, i see *straps *instead of wire going to the * larger coils and switches, *even some switch box's * *have *straps * from relays *to connectors *etc * *would wire *have been 'better' * and *or *avoid * the *proximity *effect?? Proximity effect isn't a factor unless conductors are very close together -- I suggest you review the previous postings which explain it.. As far as "better", the answer is that it probably doesn't matter, since either a wire or strap can usually be pretty easily made large enough to make loss negligible in those applications. Roy Lewallen, W7EL Proximity effect is when you are too close to a directional microphone and the bass is accentuated. *I think you mean mutual coupling. Wrong one of the several meanings, Dave. See fourth entry under http://en.wikipedia.org/wiki/Proximity_effect. ;-) |
coils?multi-turn magnetic loops
K7ITM wrote:
On Nov 25, 5:53 am, Dave wrote: Roy Lewallen wrote: ml wrote: does this rule also hold true for example i've opened some tuners and linear amps, often, i see straps instead of wire going to the larger coils and switches, even some switch box's have straps from relays to connectors etc would wire have been 'better' and or avoid the proximity effect?? Proximity effect isn't a factor unless conductors are very close together -- I suggest you review the previous postings which explain it. As far as "better", the answer is that it probably doesn't matter, since either a wire or strap can usually be pretty easily made large enough to make loss negligible in those applications. Roy Lewallen, W7EL Proximity effect is when you are too close to a directional microphone and the bass is accentuated. I think you mean mutual coupling. Wrong one of the several meanings, Dave. See fourth entry under http://en.wikipedia.org/wiki/Proximity_effect. ;-) Thanks. Seems to be the realm of the esoteric however. |
coils?multi-turn magnetic loops
On Wed, 26 Nov 2008 13:52:08 +0000, Dave wrote:
Proximity effect isn't a factor unless conductors are very close Thanks. Seems to be the realm of the esoteric however. Esoteric? As an issue of loss, it is probably more common than conductor shape, and is (unlike most of the scribblings here to this group) decidedly on-topic and focused. 73's Richard Clark, KB7QHC |
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