Balun Questions
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I'll preface this by explaining that I'm a digital guy and I've lately
decided I want to get a little better understanding of magnetics and RF... Thus why I'm taking on making my own W3NQN band pass filters and I've also been interested in building a Balun... So I've looked at a few sites describing how to make a 4:1 balun... One such solution is to take 2 100 ohm 1:1 baluns and connect them in parallel on the input side and in series on the output side... I looked at the Elecraft BL1 manual but I didn't see what material the core was... However in another article I saw someone post the recommend getting a FT140-61 and winding 7 to 8 turns on each side to make the two 100 ohm feedlines. So I ran the numbers and 8 turns on a FT140-61 gives you about 100 ohms on 160 meters. Thus two 100 ohm points in parallel gives you 50 ohms in and 200 ohms out. 4:1... Great. However at say 40 meters... Each feedline is 430 ohms. Thus you've got a 215ohm input and a 860 ohm output. This just seems like it would make a mess. Why does it still work? Finally I'll explain my final goal... I've looked at several ways to make a 4:1 which involves using two 1:1's. Then there are methods to take 2 4:1's to make a 6:1 (the feedlines are 125ohm windings to pull this off). My final goal is to try to make a 6:1 and use it to use ladder line once I get through the wall with coax. I always just figured that a 6:1 would be better as it would have a 50 ohm in and a true 300 ohm out. However once you get away from the design frequency the feed impedances go to pot... So is there really much difference in the 6:1 and the 4:1? I've read of many people doing what I'm talking about with a 4:1 and just figured that a 6:1 should provide a better match... Am I thinking right or is the match so terrible anyway that it doesn't so much matter? Is it just that the thing balances the currents on the outputs and I'm just over thinking the matching ability? Appreciated gentlemen. ~Brett (N7MG) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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> So I've looked at a few sites describing how to make a 4:1 balun... One
> such solution is to take 2 100 ohm 1:1 baluns and connect them in > parallel on the input side and in series on the output side... The 100 ohms is the differential impedance, or transmission line impedance, NOT the choking or common mode impedance. > I looked at the Elecraft BL1 manual but I didn't see what material the > core was... However in another article I saw someone post the recommend > getting a FT140-61 and winding 7 to 8 turns on each side to make the two > 100 ohm feedlines. That probably would not be close to enough impedance for lower bands. > So I ran the numbers and 8 turns on a FT140-61 gives you about 100 ohms > on 160 meters. Thus two 100 ohm points in parallel gives you 50 ohms in > and 200 ohms out. 4:1... Great. Not great. Bad news. That impedance should be as high as possible and at least 1000 ohms or more at the low end. The conductor diameter and spacing sets the 100 ohms. NOT the common mode. > However at say 40 meters... Each feedline is 430 ohms. Thus you've got > a 215ohm input and a 860 ohm output. This just seems like it would make > a mess. Why does it still work? Almost anything will work. It all depends on how well. > Finally I'll explain my final goal... I've looked at several ways to > make a 4:1 which involves using two 1:1's. Then there are methods to > take 2 4:1's to make a 6:1 (the feedlines are 125ohm windings to pull > this off). My final goal is to try to make a 6:1 and use it to use > ladder line once I get through the wall with coax. I always just > figured that a 6:1 would be better as it would have a 50 ohm in and a > true 300 ohm out. Why would that be better?? Is your 300 ohm line matched? Most people using balanced lines do not match the lines, so the input impedance ranges from a few dozen ohms to a few thousand ohms depending on frequency and band. Any effort to match the balun to the line is misplaced. Also the higher the balun ratio, the narrower the balun operating range and the less likely it is to handle power. Virtually all tuners have a problem with LOW impedances. With all that in mind, why would anyone want to step down the line impedance arriving at a tuner when it aggravates almost every electrical problem in the system including in the balun? > Is it just that the thing balances the currents on the outputs and I'm > just over thinking the matching ability? Yes, but don't feel bad. Some popular books have real zingers in them when it comes to common mode impedance and balance, and even suggest balun designs that won't work as baluns at all!!! http://www.w8ji.com/balun_single_core_41_analysis.htm 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
Brett, I would recommend the Book "Understanding, Building and Using Baluns and
Ununs by the late Jerry Sevick, avaliable from CQ http://store.cq-amateur-radio.com/Categories.bok?category=Books%3AAntennas&searchpath=1547318&start=10&total=17 With this book, a BS in Physics, 54 years as a ham and 30 years as an EE I finally understood enough to make a balun or an unun. I don't understand them well enough to answer your questions correctly. I read all the stuff I could find on the internet and 50 years of ham magazines before I bought the book and was still too confused to pick a core and build the unun that I needed. If you just want a 4:1 balun and don't want a study course, I would recommend that you buy one. If you really need one that works 160 to 10 buy an expensive one from a good source, the ones that I tested did not have the advertised bandwidth. I did not test the Elecraft balun, but what I have seen of Elecraft engineering would give me confidence to try one. Willis 'Cookie' Cooke K5EWJ ________________________________ From: Brett Howard <[hidden email]> To: elecraft <[hidden email]> Sent: Fri, July 23, 2010 3:53:42 AM Subject: [Elecraft] Balun Questions I'll preface this by explaining that I'm a digital guy and I've lately decided I want to get a little better understanding of magnetics and RF... Thus why I'm taking on making my own W3NQN band pass filters and I've also been interested in building a Balun... So I've looked at a few sites describing how to make a 4:1 balun... One such solution is to take 2 100 ohm 1:1 baluns and connect them in parallel on the input side and in series on the output side... I looked at the Elecraft BL1 manual but I didn't see what material the core was... However in another article I saw someone post the recommend getting a FT140-61 and winding 7 to 8 turns on each side to make the two 100 ohm feedlines. So I ran the numbers and 8 turns on a FT140-61 gives you about 100 ohms on 160 meters. Thus two 100 ohm points in parallel gives you 50 ohms in and 200 ohms out. 4:1... Great. However at say 40 meters... Each feedline is 430 ohms. Thus you've got a 215ohm input and a 860 ohm output. This just seems like it would make a mess. Why does it still work? Finally I'll explain my final goal... I've looked at several ways to make a 4:1 which involves using two 1:1's. Then there are methods to take 2 4:1's to make a 6:1 (the feedlines are 125ohm windings to pull this off). My final goal is to try to make a 6:1 and use it to use ladder line once I get through the wall with coax. I always just figured that a 6:1 would be better as it would have a 50 ohm in and a true 300 ohm out. However once you get away from the design frequency the feed impedances go to pot... So is there really much difference in the 6:1 and the 4:1? I've read of many people doing what I'm talking about with a 4:1 and just figured that a 6:1 should provide a better match... Am I thinking right or is the match so terrible anyway that it doesn't so much matter? Is it just that the thing balances the currents on the outputs and I'm just over thinking the matching ability? Appreciated gentlemen. ~Brett (N7MG) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
I have finally just given up. I no longer try to use the K3 recorder to show the other ham how his signal sounds.....just too darned confusing.
Great Grandmaw Susan If you don't change direction you WILL arrive exactly where you're headed!! Susan Meckley, Skipper W7KFI-mm AFA9SM USSV DHARMA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W8JI
On Fri, 23 Jul 2010 06:34:54 -0400, Tom W8JI wrote:
>The 100 ohms is the differential impedance, or transmission >line impedance Tom is the balun expert around here, but he isn't telling you everything he knows, so I'll float a simple 4:1 balun design that should work quite well up to moderate power levels. As Tom's analysis shows (on his link), there are conditions of use where high power can overheat it. So to respond to your question with a direct answer, for a 4:1 balun, I would build it from two common mode chokes, each choke wound on its own 2.4-inch o.d. #31 toroid. Each choke needs 14 bifilar turns of #14 THHN. As you have noted, the chokes should be wired in parallel on the 50 ohm side and in series on the 200 ohm side. One of the important conditions that makes this work (or not work) is that the common mode impedance must be quite high to prevent the choke from overheating, and to minimize power loss. These chokes provide nearly 5000 ohms common mode impedance from 2-30 MHz. The impedance is predominantly resistive. Bifilar means that you form a transmission line from two equal lengths of the #14 THHN, tightly spaced so that their insulation touches, and either tape them together or hold them together with Ty-wraps, then wind that parallel wire transmission line around the toroid. You'll need 2.5 inches of each wire per turn, plus 5 inches for connections at the ends, then cut off the excess after winding. Sevick said that such a line is pretty close to 100 ohms, and my measurements suggest that he was right. Two of these in series/parallel gives you a pretty good 50:200 balun. What are conditions that can overheat it? Running high power (greater than about 500 watts) AND in a condition that places high common mode voltage on it. You might also get into trouble at somewhat less power with key-down modes like RTTY. High common mode voltage will be present if the antenna is severely unbalanced (for example, an off-center fed antenna), or if the transmission line is close to a half wave (or multiple of half waves). At low power, you'll never run into a situation that will overheat a balun like this, but you could when running high power. There's a tutorial on my website that talks extensively about common mode chokes. It is NOT about baluns, and I don't pretend to be an expert on baluns, but I do know a lot about common mode chokes. :) http://audiosystemsgroup.com/RFI-Ham.pdf 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by ussv dharma
Don't worry about it, Susan. Wayne has on his 'list' to include some
refinements to the KDVR3 to enable us to actually hear what is being transmitted. Until then, my own KDVR3 is on hold. 73 de David G4DMP In a recent message, ussv dharma <[hidden email]> wrote ... > >I have finally just given up. I no longer try to use the K3 recorder >to show the other ham how his signal sounds.....just too darned >confusing. > >Great Grandmaw Susan -- David G4DMP Leeds, England, UK ------ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Brown-10
This sounds really similar to a lot of plans that I've seen... One
other piece that I've noticed on many of these that no one seems to ever mention is that the two 1:1's are usually wound in opposite directions on each half of the core... I'm assuming this helps to reduce the coupling between the two 1:1's? Also I'd be interested to hear people's thoughts on this "improved balun"... Seems to be an attractive solution. It only pictures the schematic here and I kinda picture it as being wound similarly but you wire one of the turns on one of the feeds from "out" side to "in" side. Essentially the ends of the wires would fold back over the core to get to its location... Soon here I should have all sorts of cores and wire and I was planning on trying a few of these and measuring them with the 259B and seeing how they come out. But to go beyond that I'll need some sort of antenna probably to do further testing cause I don't have enough loads nor do I have a 200ohm dummy... ;) I'll be ordering the Sevik book as well... Thanks gentlemen. ~Brett (N7MG) On Fri, Jul 23, 2010 at 9:38 AM, Jim Brown <[hidden email]> wrote: > On Fri, 23 Jul 2010 06:34:54 -0400, Tom W8JI wrote: > >>The 100 ohms is the differential impedance, or transmission >>line impedance > > Tom is the balun expert around here, but he isn't telling you > everything he knows, so I'll float a simple 4:1 balun design > that should work quite well up to moderate power levels. As > Tom's analysis shows (on his link), there are conditions of use > where high power can overheat it. > > So to respond to your question with a direct answer, for a 4:1 > balun, I would build it from two common mode chokes, each choke > wound on its own 2.4-inch o.d. #31 toroid. Each choke needs 14 > bifilar turns of #14 THHN. As you have noted, the chokes should > be wired in parallel on the 50 ohm side and in series on the > 200 ohm side. One of the important conditions that makes this > work (or not work) is that the common mode impedance must be > quite high to prevent the choke from overheating, and to > minimize power loss. These chokes provide nearly 5000 ohms > common mode impedance from 2-30 MHz. The impedance is > predominantly resistive. > > Bifilar means that you form a transmission line from two equal > lengths of the #14 THHN, tightly spaced so that their > insulation touches, and either tape them together or hold them > together with Ty-wraps, then wind that parallel wire > transmission line around the toroid. You'll need 2.5 inches of > each wire per turn, plus 5 inches for connections at the ends, > then cut off the excess after winding. Sevick said that such a > line is pretty close to 100 ohms, and my measurements suggest > that he was right. Two of these in series/parallel gives you a > pretty good 50:200 balun. > > What are conditions that can overheat it? Running high power > (greater than about 500 watts) AND in a condition that places > high common mode voltage on it. You might also get into trouble > at somewhat less power with key-down modes like RTTY. High > common mode voltage will be present if the antenna is severely > unbalanced (for example, an off-center fed antenna), or if the > transmission line is close to a half wave (or multiple of half > waves). At low power, you'll never run into a situation that > will overheat a balun like this, but you could when running > high power. > > There's a tutorial on my website that talks extensively about > common mode chokes. It is NOT about baluns, and I don't pretend > to be an expert on baluns, but I do know a lot about common > mode chokes. :) > > http://audiosystemsgroup.com/RFI-Ham.pdf > > 73, Jim Brown K9YC > > > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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<<
This sounds really similar to a lot of plans that I've seen... One other piece that I've noticed on many of these that no one seems to ever mention is that the two 1:1's are usually wound in opposite directions on each half of the core... I'm assuming this helps to reduce the coupling between the two 1:1's? Also I'd be interested to hear people's thoughts on this "improved balun"... Seems to be an attractive solution. It only pictures the schematic here and I kinda picture it as being wound similarly but you wire one of the turns on one of the feeds from "out" side to "in" side. Essentially the ends of the wires would fold back over the core to get to its location>> If you are talking about two cores in the balun, and each core wound with half turns and then flipped with a transposed winding, everyone who has measured the fancy winding concludes it does nothing overall except move things around. If you are talking about winding two 1:1 baluns on a single common core and using that to make a 4:1 current balun, I can guarantee you that will not be a balun. It will unbalance any balanced load placed on the balun's balanced terminals. Each transmission line transformer has to be on its own independent core. They cannot share a common flux path. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Ok I was referring to a design that was using one core to make a
4:1... I think the caveat that was being used was that they felt they could do this and be safe enough with it still being a balun as long as the load was floating (but I'm not 100% sure thats really the case)... So is a multi aperture core good enough for that or would two toroids be a better idea? ~Brett (N7MG) On Fri, Jul 23, 2010 at 11:00 AM, Tom W8JI <[hidden email]> wrote: > << > This sounds really similar to a lot of plans that I've seen... One > other piece that I've noticed on many of these that no one seems to > ever mention is that the two 1:1's are usually wound in opposite > directions on each half of the core... I'm assuming this helps to > reduce the coupling between the two 1:1's? Also I'd be interested to > hear people's thoughts on this "improved balun"... Seems to be an > attractive solution. It only pictures the schematic here and I kinda > picture it as being wound similarly but you wire one of the turns on > one of the feeds from "out" side to "in" side. Essentially the ends > of the wires would fold back over the core to get to its location>> > > If you are talking about two cores in the balun, and each core wound with > half turns and then flipped with a transposed winding, everyone who has > measured the fancy winding concludes it does nothing overall except move > things around. > > If you are talking about winding two 1:1 baluns on a single common core and > using that to make a 4:1 current balun, I can guarantee you that will not be > a balun. It will unbalance any balanced load placed on the balun's balanced > terminals. Each transmission line transformer has to be on its own > independent core. They cannot share a common flux path. > > 73 Tom > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by David Pratt
You can hear what you're transmitting with the monitor feature. Wait - I think I know what the issue is - I'm guessing that you are not using headphones, so you don't want the monitor on except when playing back a DVR recording. My mistake. I presumed you would be using headphones to get the best results from your K3's receiver. 73, Bob W5OV (always uses headphones) > Don't worry about it, Susan. Wayne has on his 'list' to include some > refinements to the KDVR3 to enable us to actually hear what is being > transmitted. Until then, my own KDVR3 is on hold. > > 73 de David G4DMP > > In a recent message, ussv dharma <[hidden email]> wrote ... >> >>I have finally just given up. I no longer try to use the K3 recorder >>to show the other ham how his signal sounds.....just too darned >>confusing. >> >>Great Grandmaw Susan > -- > David G4DMP > Leeds, England, UK > ------ > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W8JI
I've heard a lot of really great things about balun designs
products... And in looking at their 4:1 for dipoles and yagi's it looks like they are simply doing 2 1:1 baluns on a single core. Looks to me like they are even wrapped in the same direction and paralleled on one side then series on the other end. http://www.balundesigns.com/servlet/the-56/current-balun-4-cln-1-designs/Detail However their more general one: http://www.balundesigns.com/servlet/the-69/4-cln-1-balun/Detail I can't really trace out how its wired up... ~Brett (N7MG) On Fri, Jul 23, 2010 at 11:00 AM, Tom W8JI <[hidden email]> wrote: > << > This sounds really similar to a lot of plans that I've seen... One > other piece that I've noticed on many of these that no one seems to > ever mention is that the two 1:1's are usually wound in opposite > directions on each half of the core... I'm assuming this helps to > reduce the coupling between the two 1:1's? Also I'd be interested to > hear people's thoughts on this "improved balun"... Seems to be an > attractive solution. It only pictures the schematic here and I kinda > picture it as being wound similarly but you wire one of the turns on > one of the feeds from "out" side to "in" side. Essentially the ends > of the wires would fold back over the core to get to its location>> > > If you are talking about two cores in the balun, and each core wound with > half turns and then flipped with a transposed winding, everyone who has > measured the fancy winding concludes it does nothing overall except move > things around. > > If you are talking about winding two 1:1 baluns on a single common core and > using that to make a 4:1 current balun, I can guarantee you that will not be > a balun. It will unbalance any balanced load placed on the balun's balanced > terminals. Each transmission line transformer has to be on its own > independent core. They cannot share a common flux path. > > 73 Tom > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
Brett,
Do you have an old link coupled tuner - like the Johnson Matchbox or a homebrew one with plug-in coils? If you do, hook it up "backwards" with a dummy load on the normal input side. You have just created a tunable "artificial antenna" - tune the Matchbox to produce whatever load impedance you want. 73, Don W3FPR Brett Howard wrote: > But to go beyond that I'll need some sort of > antenna probably to do further testing cause I don't have enough loads > nor do I have a 200ohm dummy... ;) > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Would this work with any tuner? That is, can I take a regular unbalanced tuner and put a dummy load on the input and then use it to create an artificial mismatch for testing?
73, phil, K7PEH P.S. Loss issues would not be important for my thinking of doing this. On Jul 23, 2010, at 11:22 AM, Don Wilhelm <[hidden email]> wrote: > Brett, > > Do you have an old link coupled tuner - like the Johnson Matchbox or a > homebrew one with plug-in coils? > If you do, hook it up "backwards" with a dummy load on the normal input > side. > You have just created a tunable "artificial antenna" - tune the Matchbox > to produce whatever load impedance you want. > > 73, > Don W3FPR > > Brett Howard wrote: > > But to go beyond that I'll need some sort of > > antenna probably to do further testing cause I don't have enough loads > > nor do I have a 200ohm dummy... ;) > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
Ok I was referring to a design that was using one core to make a 4:1... I think the caveat that was being used was that they felt they could do this and be safe enough with it still being a balun as long as the load was floating (but I'm not 100% sure thats really the case)...>>> I can 100% guarantee you that does not balance the load. I know the design comes from a source considered reliable, but it is seriously flawed. If you want a balanced voltage and/or current into a feedline and a real antenna, it cannot happen with that design. It not only does not work in theory, I have dozens of actual measurements to support it does not work in the real world. <<So is a multi aperture core good enough for that or would two toroids be a better idea?>> So long as the multi-aperture core does not have mutual coupling between the individual transmission line cores, it would work. Unfortunately that is not likely either. :-) 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Interesting enough his high power one uses two cores and appears to be
made the same as the "budget" one that is wound on one core... Seems like stacking them on top of one another is going to just couple them and hinder your isolation but maybe I'm wrong there.... http://www.balundesigns.com/servlet/the-78/4-cln-1-dual-core-current/Detail ~Brett (N7MG) On Fri, Jul 23, 2010 at 11:31 AM, Tom W8JI <[hidden email]> wrote: > > Ok I was referring to a design that was using one core to make a > 4:1... I think the caveat that was being used was that they felt they > could do this and be safe enough with it still being a balun as long > as the load was floating (but I'm not 100% sure thats really the > case)...>>> > > I can 100% guarantee you that does not balance the load. I know the design > comes from a source considered reliable, but it is seriously flawed. If you > want a balanced voltage and/or current into a feedline and a real antenna, > it cannot happen with that design. It not only does not work in theory, I > have dozens of actual measurements to support it does not work in the real > world. > > <<So is a multi aperture core good enough for that or would two toroids > be a better idea?>> > > So long as the multi-aperture core does not have mutual coupling between the > individual transmission line cores, it would work. Unfortunately that is not > likely either. :-) > > 73 Tom > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W8JI
I haven't taken, nor at the moment do I have, the time to analyze this, but I'll throw it out.
http://home.earthlink.net/~christrask/Trask4to1Balun.pdf Wes N7WS --- On Fri, 7/23/10, Tom W8JI <[hidden email]> wrote: > > Ok I was referring to a design that was using one core to > make a > 4:1... I think the caveat that was being used was > that they felt they > could do this and be safe enough with it still being a > balun as long > as the load was floating (but I'm not 100% sure thats > really the > case)...>>> > > I can 100% guarantee you that does not balance the load. I > know the design > comes from a source considered reliable, but it is > seriously flawed. If you > want a balanced voltage and/or current into a feedline and > a real antenna, > it cannot happen with that design. It not only does not > work in theory, I > have dozens of actual measurements to support it does not > work in the real > world. > > <<So is a multi aperture core good enough for that or > would two toroids > be a better idea?>> > > So long as the multi-aperture core does not have mutual > coupling between the > individual transmission line cores, it would work. > Unfortunately that is not > likely either. :-) > > 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Sorry if I missed a thread on this, but did Elecraft miss the July 17
proposed ship date for the P3..?? W4CCS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Cookie
Just bought the last copy of this book that Amazon had in stock for
17.95 + 3.99 in shipping. Looks like it will be a very nice reference to have on the shelf... Thanks! ~Brett (N7MG) On Fri, Jul 23, 2010 at 5:21 AM, WILLIS COOKE <[hidden email]> wrote: > Brett, I would recommend the Book "Understanding, Building and Using Baluns > and Ununs by the late Jerry Sevick, avaliable from CQ > http://store.cq-amateur-radio.com/Categories.bok?category=Books%3AAntennas&searchpath=1547318&start=10&total=17 > With this book, a BS in Physics, 54 years as a ham and 30 years as an EE I > finally understood enough to make a balun or an unun. I don't understand > them well enough to answer your questions correctly. I read all the stuff I > could find on the internet and 50 years of ham magazines before I bought the > book and was still too confused to pick a core and build the unun that I > needed. If you just want a 4:1 balun and don't want a study course, I would > recommend that you buy one. If you really need one that works 160 to 10 buy > an expensive one from a good source, the ones that I tested did not have the > advertised bandwidth. I did not test the Elecraft balun, but what I have > seen of Elecraft engineering would give me confidence to try one. > > Willis 'Cookie' Cooke > K5EWJ > > ________________________________ > From: Brett Howard <[hidden email]> > To: elecraft <[hidden email]> > Sent: Fri, July 23, 2010 3:53:42 AM > Subject: [Elecraft] Balun Questions > > I'll preface this by explaining that I'm a digital guy and I've lately > decided I want to get a little better understanding of magnetics and > RF... Thus why I'm taking on making my own W3NQN band pass filters and > I've also been interested in building a Balun... > > So I've looked at a few sites describing how to make a 4:1 balun... One > such solution is to take 2 100 ohm 1:1 baluns and connect them in > parallel on the input side and in series on the output side... > > I looked at the Elecraft BL1 manual but I didn't see what material the > core was... However in another article I saw someone post the recommend > getting a FT140-61 and winding 7 to 8 turns on each side to make the two > 100 ohm feedlines. > > So I ran the numbers and 8 turns on a FT140-61 gives you about 100 ohms > on 160 meters. Thus two 100 ohm points in parallel gives you 50 ohms in > and 200 ohms out. 4:1... Great. > > However at say 40 meters... Each feedline is 430 ohms. Thus you've got > a 215ohm input and a 860 ohm output. This just seems like it would make > a mess. Why does it still work? > > Finally I'll explain my final goal... I've looked at several ways to > make a 4:1 which involves using two 1:1's. Then there are methods to > take 2 4:1's to make a 6:1 (the feedlines are 125ohm windings to pull > this off). My final goal is to try to make a 6:1 and use it to use > ladder line once I get through the wall with coax. I always just > figured that a 6:1 would be better as it would have a 50 ohm in and a > true 300 ohm out. > > However once you get away from the design frequency the feed impedances > go to pot... So is there really much difference in the 6:1 and the 4:1? > I've read of many people doing what I'm talking about with a 4:1 and > just figured that a 6:1 should provide a better match... Am I thinking > right or is the match so terrible anyway that it doesn't so much > matter? > > Is it just that the thing balances the currents on the outputs and I'm > just over thinking the matching ability? > > Appreciated gentlemen. > > ~Brett (N7MG) > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
Brett,
The coupling between the toroids is not as much of a problem as the flux cancellation when an attempt to use one core - that just does not work right. 73, Don W3FPR Brett Howard wrote: > Interesting enough his high power one uses two cores and appears to be > made the same as the "budget" one that is wound on one core... Seems > like stacking them on top of one another is going to just couple them > and hinder your isolation but maybe I'm wrong there.... > > http://www.balundesigns.com/servlet/the-78/4-cln-1-dual-core-current/Detail > > ~Brett (N7MG) > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Brett Howard
On Jul 23, 2010, at 12:41 PM, Brett Howard wrote: > Just bought the last copy of this book that Amazon had in stock for > 17.95 + 3.99 in shipping. Looks like it will be a very nice reference > to have on the shelf... > >> "Understanding, Building and Using Baluns >> and Ununs by the late Jerry Sevick, avaliable from CQ >> http://store.cq-amateur-radio.com/Categories.bok?category=Books%3AAntennas&searchpath=1547318&start=10&total=17 Sevick had also written a series of Balun articles in Communications Quarterly. ARRL bought Communications Quarterly from CQ Communications and merged it into QEX, so Comm Quarterly is no more. But the ARRL has archived all the old issues of Communications Quarterly from 1990 until 1999 into a single CD-ROM, that you can read on older Windows machines and by using "QST Browser" on Mac OS X. For ready built W2FMI Baluns and Ununs, take a look here http://www.cwsbytemark.com/ 73 Chen, W7AY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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