+++++++++++++++++++ Date: Sat, 12 Jan 2002 21:47:28 -0500 To: "Jonathan Taylor, K1RFD" From: Charles Greene Subject: Re: [Elecraft] Balun for KAT2 Cc: At 08:22 PM 1/12/2002 -0500, Jonathan Taylor, K1RFD wrote: >I just set up an 80m dipole with ladder line (600 ohm), and may soon become >a believer in the open-wire feed. > >When using it with an ATU such as the KAT2, with low power, what is the most >efficient way to convert the KAT2 unbalanced output to the balanced line? > >My first inclination is to build a small toroidal balun inside a box and run >a short length of coax to the rig. But I have also read that this type of >balun can be lossy when working through an impedance (on the balanced side) >far from the design impedance. (Is the coax length critical?) > >Has anyone used the so-called "current baluns" offered by RadioWorks? I have a current balun made by Radio Works, and it works well. Some of the baluns you can make your self from the links on the Elecraft web site don't work so well. I have built some that work as well as the Radio Works ones, but for low power. Try 13 turns #24 magnetic wire biflar wound on a FT114-43 core, then use two cores. Hookup per Tom Hammond's web site: http://home.earthlink.net/~n0ss/download.html The two core current baluns work better than the single core ones. I have found the current baluns work well if you trim your open wire line until you don't have a current node on any band in use where the balun goes. If you use any kind of a balun at a current node (high voltage point), it may destroy the balun, and if it doesn't actually destroy the balun, it won't work well and will have high losses. You can also use a 1:1 balun, made by placing ferrite beads on the transmission line, or by winding some coax in a coil. See ARRL handbook for the design. Check QST ads for a 1:1 balun bead kit. 73, Chas, W1CG ++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "Jonathan Taylor, K1RFD" , Subject: Re: [Elecraft] Balun for KAT2 Date: Sat, 12 Jan 2002 21:54:49 -0500 Jonathan, I may be opening a can of worms here because there are a lot of 'balun believers' out there, but I would start with no balun at all. It WILL work, but there is a possibility that you may get some 'RF in the shack' - should that happen, I would recommend an RF choke on a short section of coax (use big coax for best efficiency). You could use a coil of coax, but even better is the W2DU type of balun (a bunch of ferrite cores over the coax shield) - make your own with 12 to 20 FT-50-43 cores slipped over RG213 coax. You need more cores at lower frequencies because it is the choking inductance that does the job. The baluns made by winding bifilar (or tri-filar) turns on a core can be very lossy when used on a feedline having input impedances far away from the 25 to 300 ohm impedances that these baluns are usually designed for and they are not very happy with reactive loads. 73, Don Wilhelm - Wake Forest, NC W3FPR home page: http://www.qsl.net/w3fpr/ QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net ----- Original Message ----- > I just set up an 80m dipole with ladder line (600 ohm), and may soon become > a believer in the open-wire feed. > > When using it with an ATU such as the KAT2, with low power, what is the most > efficient way to convert the KAT2 unbalanced output to the balanced line? +++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Don Wilhelm" , "Jonathan Taylor, K1RFD" , Subject: RE: [Elecraft] Balun for KAT2 Date: Sat, 12 Jan 2002 20:01:54 -0800 Don wrote: > Jonathan, > I may be opening a can of worms here because there are a lot of 'balun > believers' out there, but I would start with no balun at all. It > WILL work, > but there is a possibility that you may get some 'RF in the > shack' - ... I'll second Don's comments here. As a long-time user of open wire line, I believe that the only way to be SURE you are getting all the benefits of the line is to have balanced feed. If the currents are NOT in balance, the feedline will radiate and pick up r-f. But the fact is, as Don says, having great balance at the rig is not always necessary and trying to ensure balance with a balun can create problems if the balun can't handle the impedance it sees on the line. Baluns are really intended to provide balanced feed to a line with low VSWR. The main reason most of us use balanced line today is so we can run line efficiently with high VSWR, such as in a G5RV or center fed doublet. If the impedances are not too extreme, you can get away with it. But it's hard to tell how much the balun is losing. Sure, running low power will stop the balun core from getting hot. But that's not always because it is working efficiently. It might be because you can put 10 watts into a large core and it'll convert 9.9 watts of it into heat without feeling hot to the touch. However, one clue that a balun has quit working efficiently is that it will usually stop providing a balanced feed as well. If you want to use a balun and wonder if it is ... er... 'balancing' the feed, all you have to do is check. To check the balance, all you have to do is to put two r-f ammeters in your feeders and see if they read the same... Relax, you can buy a nice r-f ammeter for less than a buck. It's called a small flashlight bulb. FIRST, turn the power down to about .2 watts and transmit briefly so the power control circuit has really turned the power down. Next, put two identical bulbs in your balanced line (buy several, the K2's power control system makes it easy to smoke them). Little 1.5 volt bulbs are fine. Transmit and watch the bulbs. Turn up the power so they glow dully. You can actually see a very small difference (10% or so) by eye if you have them glowing dimly. If they look pretty much the same, your balun is probably working. I can't guarantee that it is working near top efficiency, but the likelihood is that it is doing okay. If the bulbs are very much different in brightness, you can be sure the balun is not able to function properly and, at the very least, is not being a balun. It might be making itself into a great dummy load. In any case there is no reason to keep using that particular balun. If you saw a bright flash from both bulbs, then nothing, you forgot to turn down the power on the rig, or you forgot to transmit AFTER tuning down the power and before inserting the bulbs, so the rig hit the bulbs with the full output. IF the feedline presents a very high impedance at the rig, it may take all the output of your rig to produce even the faintest glow. There is a high voltage and very low current in that case, and it's the current that lights the bulbs. At the other extreme, where your feeders present a low impedance to the balun, you may find the bulbs quite bright running only a few hundred milliwatts. However bright or dull, may your bulbs glow evenly... Ron AC7AC K2 #1289 ++++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Jonathan Taylor, K1RFD" , Subject: RE: [Elecraft] Balun for KAT2 Date: Sun, 13 Jan 2002 11:20:20 -0800 After I posted the message about using a couple of small light bulbs for checking the 'balance' at the output of a balun, Chas, W1CG, dropped me a note that said: "I have made some and run some efficiency tests. The 13 T on a FT114-43 core is 97% efficient into a balanced 200 ohm load, and is 90% efficient into a 5:1 SWR. They are small and use high permeability ferrite to get enough inductance to operate at 1.8 mHz with a 5:1 SWR, (110 uhy). A lower loss ferrite or powered iron core would have lower losses. The loss of 3% is 0.13 dB, and the loss of 10% is .45 dB. I use one on a my W3EDP antenna which runs 5:1 SWR on some bands, at 100 watts. The loss of a 1:1 using beads or a coax coil is less lossy." Charles has written about that before, and I hope he doesn't mind my repeating it here because it is good stuff. Just because a balun CAN be inefficient doesn't mean that it IS inefficient. I have successfully used them in many conditions. My warning was only that they CAN be power eaters and that it is not always as obvious that's what's happening. One time I did get a warning when I smelled a funny odor running 10 watts on 40 meters. It was the plastic on a banana plug connector to my feedline melting from the high r-f voltage at that point! The balun - one out of a "300 watt" MFJ tuner - was also hot. Since then I've found that, most often, the balance to the feeders goes to pot when the balun is pushed too hard. That's why I suggested the little light bulb test as one way to get a clue about what is happening. But, as Chas has documented from his tests, you can expect a decent balun to behave very well much (perhaps most) of the time as well. Ron AC7AC K2 # 1289 +++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 To: "Jonathan Taylor, K1RFD" , From: "Steve Lawrence" Date: Sun, 13 Jan 2002 18:08:50 -0500 Jonathan, While I didn't conduct testing to measure losses, I reasoned that a simple W2DU choke type balun would have lower loss over a transformer type balun wound over a toroid. As such, that's what I'm using. I connect out of my K2/KAT2 through a short coax run to a Radio Works choke balun. Then directly to 450 ohm window line to my dipole, cut for 40M. I let the KAT2 match the "mess" unconcerned about the short length of coax, but knowing the choke balun will do the unbalanced-to-balanced conversion by minimizing the current flow on the coax shield. This combination seems to tune OK on 40M on up. This is my "portable" setup. My next experiments will be with the "end fed half wave". Primary goal: reduce weight even further, down to a backpackable weight and size. Another possibility will be a 300 ohm twin-lead dipole -- e.g. QST, Feb '02. After reading W2DU's book "Reflections" I've really changed my view on SWR. Mr. Maxwell clearly demonstrates that SWR alone is not a reliable indication of good antenna match (or performance). In fact, a low SWR may really mean high losses, low efficiency and other undesirable conditions! So, I've begun to look toward improving efficiency -- not minimizing SWR. Why? Well briefly, a 50 ohm dummy load will indicate a 1:1 SWR, yet radiate poorly! All power entering the transmission line is radiated, independent of SWR -- less losses (in coax, ground, etc.). As such, I've looked at elements in my antenna system that are low loss. The W2DU type choke balun is in this class. 73, Steve aa8af +++++++++++++++++ From: "Jonathan Taylor, K1RFD" To: "Charles Greene" Cc: Subject: Re: [Elecraft] Balun for KAT2 Date: Mon, 14 Jan 2002 07:45:11 -0500 Thanks. It sounds like the summary is: Regarding the use of toroidal baluns to connect a balanced transmission line to the (unbalanced) output of the KAT2: 1) Toroidal baluns are commonly used for this purpose. They do exhibit losses with high SWRs, but usually not enough to noticeably affect antenna efficiency. 2) Under high SWR and relatively high power, a toroidal balun can easily overheat. To avoid this, use a beefy toroid, avoid placing it at a current node, and don't use high power . ----- Original Message ----- From: "Charles Greene" To: Cc: "Jonathan Taylor, K1RFD" ; Sent: Monday, January 14, 2002 6:20 AM Subject: RE: [Elecraft] Balun for KAT2 At 11:20 AM 1/13/2002 -0800, Ron D' Eau Claire wrote: Ron and All. I'd just like to emphasize a couple points Ron made. There are two aspects of losses. One is how it affects your antenna system. The losses of a typical balun operated into a SWR of 5:1 or less are insignificant compared to the other losses in your antenna system, so don't worry about that. However, a loss of 3% if you are running a KW is 30 watts, enough to burn up all but the larger baluns. I guess the moral is to use a balun rated for the power you are going to use, and don't operate it at a current node (high voltage point) in an open wire feed line. +++++++++++++++++ Subject: RE: [Elecraft] Balun for KAT2 Date: Thu, 17 Jan 2002 16:44:18 -0500 From: Bill Coleman To: , "Jonathan Taylor, K1RFD" , On 1/13/02 2:20 PM, Ron D' Eau Claire at rondec at easystreet.com wrote: >Chas, W1CG, dropped me a >note that said: > >"I have made some and run some efficiency >tests. The 13 T on a FT114-43 core is 97% efficient into a balanced 200 >ohm load, and is 90% efficient into a 5:1 SWR. They are small and use high >permeability ferrite to get enough inductance to operate at 1.8 mHz with a >5:1 SWR, (110 uhy). A lower loss ferrite or powered iron core would have >lower losses." The simplest way to reduce losses for high-SWR is to add additional cores. This reduces the maximum flux in each core, which reduces losses. Powdered-iron cores aren't suitable for these types of baluns, except perhaps at UHF. They don't have enough permeability to be effective without an excessively large number of turns. Although you are correct, powdered-iron cores can withstand a much higher magnetic flux level than can ferrite cores. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 ++++++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 Date: Thu, 17 Jan 2002 16:46:35 -0500 From: Bill Coleman To: "Don Wilhelm" , "Jonathan Taylor, K1RFD" , On 1/12/02 9:54 PM, Don Wilhelm at w3fpr at peoplepc.com wrote: >I may be opening a can of worms here because there are a lot of 'balun >believers' out there, but I would start with no balun at all. There's a lot of bad infomation about baluns out there. >It WILL work, Yes, it will. >but there is a possibility that you may get some 'RF in the shack' - Which is exactly what any balun is designed to prevent -- RF currents flowing on the outside of the coax. > should >that happen, I would recommend an RF choke on a short section of coax (use >big coax for best efficiency). The size of the coax doesn't matter, but if you coil coax, be sure to respect the minimum radius of the type of coax. >You could use a coil of coax, but even >better is the W2DU type of balun (a bunch of ferrite cores over the coax >shield) - make your own with 12 to 20 FT-50-43 cores slipped over RG213 >coax. You need more cores at lower frequencies because it is the choking >inductance that does the job. Coiled coax, W2DU baluns, or toroidial core current baluns (Guanella or W1JR types), all work on the same principle. So long as there is sufficient choking inductance, they work. There's a few caveats. First, you must have sufficient inductance, but a coiled coax balun can have TOO MANY turns. The distributed capacitance can make the coil resonant on the higher frequencies. Lots of turns tends to move that resonance lower, which is exactly what you don't want. 6-8 turns on a 4-6" form is sufficient for 10-30 MHz. 9-12 turns on the same form works for 3.5-25 MHz. 16 turns for 1.8-7.0 Mhz. Second, the ferrite core baluns have a wider frequency range, but the characteristics of the core come into play. This usually isn't too much of a problem for QRP operating, but QRO operators need to beware they don't heat the cores. Third, the W2DU baluns depend on the size of the coax, type of material and the total length of the beads. The size of the beads isn't really important. Typically, a 7-30 MHz balun can be constructed with about a 12-18 inches of beads. For lower frequencies, you need more inductance -- hence you need to double or triple the length. Bead material is important. Type 43 material has maximum impedance at 200 MHz, so it isn't very appropriate for HF baluns. (However, I have such a balun using FB1024-43 beads on my A3S -- works great) You're better off using type 77 material for an HF balun. You'll end up needing fewer beads. Power handling may be a problem for QRO operators with type 77 beads, but it isn't an issue for QRP. Forth, Guanella and W1JR baluns are just as effective as W2DU baluns, and can be made a lot cheaper. A FT240-77 core cost $9.00 from Amidon, whereas the beads required for a W2DU balun are closer to $18.00. If you buy commercial baluns, however, the W2DU types tend to fit well with your typical dipole installations, and can be lighter. >The baluns made by winding bifilar (or tri-filar) turns on a core can be >very lossy when used on a feedline having input impedances far away from the >25 to 300 ohm impedances that these baluns are usually designed for and they >are not very happy with reactive loads. This is wrong on three points. First, I believe you are talking about voltage-type baluns. These typically use powdered-iron cores instead of ferrite. Such cores have 1/100 of the permeability of ferrite cores. These cores are not suitable for making current baluns. Second, not all toroidial baluns are the voltage-type. The Guanella design uses a bifilar winding for a 1:1 balun. The voltage-type 1:1 requires a trifilar winding. The W1JR consists of a short length of coax (usually a very small diameter type -- often teflon insulated -- RG-142, RG-303, RG-316) wound 3-9 turns on the core. There's no electrical difference between the W2DU, Guanella or W1JR balun. Third, none of the discussed baluns (with the exception of the coaxial coil) performs well in the presence of reactive loads. Such loads can cause core saturation, heating and additional loss, unless accounted for in the design of the balun. However, you are correct that current-type baluns provide better balance to the load than voltage-type, regardless of the reactance present. The ARRL Handbook no longer provides descriptions of voltage-type baluns. Current-type baluns are recommended. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 +++++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 Date: Thu, 17 Jan 2002 16:48:02 -0500 From: Bill Coleman To: On 1/13/02 6:08 PM, Steve Lawrence at Steve.Lawrence at ITWFEG.COM wrote: >While I didn't conduct testing to measure losses, I reasoned that a simple >W2DU choke type balun would have lower loss over a transformer type balun >wound over a toroid. Just because it is wound over a toroid doesn't mean it isn't as efficient. Guanella or W1JR baluns are electrically identical to W2DU baluns, and can be just as efficient if properly designed. >After reading W2DU's book "Reflections" I've really changed my view on >SWR. Mr. Maxwell clearly demonstrates that SWR alone is not a reliable >indication of good antenna match (or performance). In fact, a low SWR may >really mean high losses, low efficiency and other undesirable conditions! >So, I've begun to look toward improving efficiency -- not minimizing SWR. It's all about loss, not SWR. (Although a low SWR can often reduce feedline losses) >Why? Well briefly, a 50 ohm dummy load will indicate a 1:1 SWR, yet >radiate poorly! All power entering the transmission line is radiated, >independent of SWR -- less losses (in coax, ground, etc.). As such, I've >looked at elements in my antenna system that are low loss. The W2DU type >choke balun is in this class. Coiled-coax type choke baluns are probably the lowest loss of the bunch. They are cheap, but their frequency range is somewhat restricted, and they can be bulky and heavy. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 ++++++++++++++++++ Date: Fri, 18 Jan 2002 07:58:00 -0500 To: Bill Coleman From: Charles Greene Subject: Re: [Elecraft] Balun for KAT2 Cc: "Don Wilhelm" , "Jonathan Taylor, K1RFD" , At 04:46 PM 1/17/2002 -0500, Bill Coleman wrote: Some comments below: >On 1/12/02 9:54 PM, Don Wilhelm at w3fpr at peoplepc.com wrote: > > >I may be opening a can of worms here because there are a lot of 'balun > >believers' out there, but I would start with no balun at all. > >There's a lot of bad infomation about baluns out there. > > >It WILL work, > >Yes, it will. > > >but there is a possibility that you may get some 'RF in the shack' - > >Which is exactly what any balun is designed to prevent -- RF currents >flowing on the outside of the coax. > > > should > >that happen, I would recommend an RF choke on a short section of coax (use > >big coax for best efficiency). > >The size of the coax doesn't matter, but if you coil coax, be sure to >respect the minimum radius of the type of coax. > > >You could use a coil of coax, but even > >better is the W2DU type of balun (a bunch of ferrite cores over the coax > >shield) - make your own with 12 to 20 FT-50-43 cores slipped over RG213 > >coax. You need more cores at lower frequencies because it is the choking > >inductance that does the job. > >Coiled coax, W2DU baluns, or toroidial core current baluns (Guanella or >W1JR types), all work on the same principle. So long as there is >sufficient choking inductance, they work. > >There's a few caveats. First, you must have sufficient inductance, but a >coiled coax balun can have TOO MANY turns. The distributed capacitance >can make the coil resonant on the higher frequencies. Lots of turns tends >to move that resonance lower, which is exactly what you don't want. > >6-8 turns on a 4-6" form is sufficient for 10-30 MHz. 9-12 turns on the >same form works for 3.5-25 MHz. 16 turns for 1.8-7.0 Mhz. > >Second, the ferrite core baluns have a wider frequency range, but the >characteristics of the core come into play. This usually isn't too much >of a problem for QRP operating, but QRO operators need to beware they >don't heat the cores. > >Third, the W2DU baluns depend on the size of the coax, type of material >and the total length of the beads. The size of the beads isn't really >important. Typically, a 7-30 MHz balun can be constructed with about a >12-18 inches of beads. For lower frequencies, you need more inductance -- >hence you need to double or triple the length. > >Bead material is important. Type 43 material has maximum impedance at 200 >MHz, so it isn't very appropriate for HF baluns. The 200 MHz pertains to coils, not to baluns; type 43 material works very well on HF baluns. I have some type 43 material current baluns that work well from 700 KHZ through 30 MHz. The balun made with type 43 material is somewhat more lossy than the powdered iron cores ones and the type 77 material even more so, but losses still are reasonable for low power operations. >(However, I have such a >balun using FB1024-43 beads on my A3S -- works great) You're better off >using type 77 material for an HF balun. You'll end up needing fewer >beads. Power handling may be a problem for QRO operators with type 77 >beads, but it isn't an issue for QRP. > >Forth, Guanella and W1JR baluns are just as effective as W2DU baluns, and >can be made a lot cheaper. A FT240-77 core cost $9.00 from Amidon, >whereas the beads required for a W2DU balun are closer to $18.00. If you >buy commercial baluns, however, the W2DU types tend to fit well with your >typical dipole installations, and can be lighter. > > >The baluns made by winding bifilar (or tri-filar) turns on a core can be > >very lossy when used on a feedline having input impedances far away from the > >25 to 300 ohm impedances that these baluns are usually designed for and they > >are not very happy with reactive loads. > >This is wrong on three points. > >First, I believe you are talking about voltage-type baluns. These >typically use powdered-iron cores instead of ferrite. Such cores have >1/100 of the permeability of ferrite cores. These cores are not suitable >for making current baluns. > >Second, not all toroidial baluns are the voltage-type. The Guanella >design uses a bifilar winding for a 1:1 balun. The voltage-type 1:1 >requires a trifilar winding. The W1JR consists of a short length of coax >(usually a very small diameter type -- often teflon insulated -- RG-142, >RG-303, RG-316) wound 3-9 turns on the core. There's no electrical >difference between the W2DU, Guanella or W1JR balun. > >Third, none of the discussed baluns (with the exception of the coaxial >coil) performs well in the presence of reactive loads. Such loads can >cause core saturation, heating and additional loss, unless accounted for >in the design of the balun. Core saturation is a factor in coils, but is not a factor in current baluns if the balanced current is maintained. The currents in the coiled transmission line are equal and opposite, and the net flux is zero. I have done extensive testing of baluns into reactive loads with high SWRs. The loss increases, but the balun will work well into a SWR of 5:1. The losses are primarily dielectric and eddy current losses. I^2 R losses contribute just a small amount to heating. The core stays cool until heated by the wires. The wires get hot as that is where the loss is. Core saturation is another of the misinformations commonly expressed about baluns. Yes, you can cause core saturation, but the other losses will probably destroy the balun first. One phenomena I have noticed during loss testing is the run away condition. If you apply high power to a balun working into a reactive load, the balun wire will get hot. That increases the losses, causing even more heating. That condition continues until the wires in the balun burn up. Another factor to watch out for is excessive voltage in the balun. Many low power baluns use only enamel insulated wire wound on the core. The enamel insulation has a break down voltage of about 500 volts, and worse case with a 5:1 SWR you can get nearly 500 volts in the balun. Most core materials have a varnish insulation which also has a breakdown voltage of about 500 volts. However, the wire can have nick in the insulation where it passes over the core. Type 77 material has no varnish insulation and you need to be careful when using it for a balun including winding a coax like RG-316 around it. A higher power core can be wound with teflon tubing over the wires, or wrap the core in glass tape. I have also successfully used teflon insulated, silver plated stranded wire for baluns. >However, you are correct that current-type baluns provide better balance >to the load than voltage-type, regardless of the reactance present. The >ARRL Handbook no longer provides descriptions of voltage-type baluns. >Current-type baluns are recommended. Sevich devotes an entire chapter in his book "Building and Using Baluns and Ununs." to baluns for antenna tuners and recommends voltage baluns, sorta. He goes to great pains to flatten response of the balun used by McCoy in his original transmatch. However, there are 2 problems with the voltage balun used in the antenna tuner. As the as the frequency is increased, the phase shift in the transmission coiled transmission line is no longer able to sustain a 4:1 ratio and the high frequency performance falls off. The second problem is a result of the first. In an attempt to extend the high frequency range, turns are removed from the balun until at the lower frequency there is barely enough inductance to prevent the primary current from flowing in the balun, decreasing the current to the load and increasing losses. This condition becomes worse when working into a high impedance load. As the load impedance increases, more primary current flows in the balun as the impedance of the balun to choke the primary current doesn't change and becomes a smaller ratio of the total impedance. I made a bunch of voltage baluns, but finally gave up on them. All the baluns I made would cover 160 through 15 or 80 through 10, but not both. BTW the T184 size is a good compact powdered iron core to use if you are into voltage baluns, as it has an inductive index higher than any core smaller than 4 inches. >Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net >Quote: "Not within a thousand years will man ever fly!" > -- Wilbur Wright, 1901 Nice chatting with you. 73, Chas, W1CG ++++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 Date: Fri, 18 Jan 2002 10:38:09 -0500 To: "Charles Greene" From: Bill Coleman Cc: "Don Wilhelm" , "Jonathan Taylor, K1RFD" , On 1/18/02 7:58 AM, Charles Greene at W1CG at QSL.net wrote: >At 04:46 PM 1/17/2002 -0500, Bill Coleman wrote: > >>Bead material is important. Type 43 material has maximum impedance at 200 >>MHz, so it isn't very appropriate for HF baluns. > >The 200 MHz pertains to coils, not to baluns; type 43 material works very >well on HF baluns. I have some type 43 material current baluns that work >well from 700 KHZ through 30 MHz. The balun made with type 43 material is >somewhat more lossy than the powdered iron cores ones and the type 77 >material even more so, but losses still are reasonable for low power >operations. If you read what I wrote, you'd see that I never said that type 43 materials couldn't be used as a balun. In fact, read the parenthetical note that follows: >>(However, I have such a >>balun using FB1024-43 beads on my A3S -- works great) And the important point: >>You're better off >>using type 77 material for an HF balun. You'll end up needing fewer >>beads. Power handling may be a problem for QRO operators with type 77 >>beads, but it isn't an issue for QRP. Type 43 materials work, but you'll have to use more beads to get sufficient inductance. More beads means more cost. Why pay more when you don't have to? >>Third, none of the discussed baluns (with the exception of the coaxial >>coil) performs well in the presence of reactive loads. Such loads can >>cause core saturation, heating and additional loss, unless accounted for >>in the design of the balun. > >Core saturation is a factor in coils, but is not a factor in current baluns >if the balanced current is maintained. The currents in the coiled >transmission line are equal and opposite, and the net flux is zero. Yes, but you also have to deal with the fact that the choke impedance is shunted across half of the antenna impedance to ground through the coax sheild. This causes some current to flow, so there is some flux. If the choke impedance is high enough, this current is small. When you deal with reactive loads, though, things change a bit. >I have >done extensive testing of baluns into reactive loads with high SWRs. The >loss increases, but the balun will work well into a SWR of 5:1. The losses >are primarily dielectric and eddy current losses. I^2 R losses contribute >just a small amount to heating. The core stays cool until heated by the >wires. The wires get hot as that is where the loss is. Core saturation is >another of the misinformations commonly expressed about baluns. Saturation isn't so much the problem as loss tangent. If you cause heating in the core, likely due to eddy current losses, the losses increase as the core gets hotter. The increase in loss leads to more heating, which leads to more loss. Eventually, the core will reach a point where the increase in loss causing enough heating that it will heat right up to the curie temperature, at which point it ceases to act as a permeable core. Do that enough times, and you can destroy the core. W8JI has done a lot of testing. There are some "2 kW" commercial baluns that fail in 5 minutes under his test conditions. > Yes, you >can cause core saturation, but the other losses will probably destroy the >balun first. One phenomena I have noticed during loss testing is the run >away condition. If you apply high power to a balun working into a reactive >load, the balun wire will get hot. That increases the losses, causing even >more heating. That condition continues until the wires in the balun burn >up. This is Loss Tangent, discussed above. Perhaps I should clarify. Eddy current losses are lower when the core is far from saturation. Large cores can deal easily with the heat. As the core gets closer to the saturation point, the losses increase, and the core can't disappate the heat. Most likely, a core in this service reaches the loss tangent point long before it goes into full saturation. > Another factor to watch out for is excessive voltage in the >balun. Many low power baluns use >only enamel insulated wire wound on the core. The enamel insulation has a >break down voltage of about 500 volts, and worse case with a 5:1 SWR you >can get nearly 500 volts in the balun. Most core materials have a varnish >insulation which also has a breakdown voltage of about 500 volts. However, >the wire can have nick in the insulation where it passes over the >core. Type 77 material has no varnish insulation and you need to be >careful when using it for a balun including winding a coax like RG-316 >around it. A higher power core can be wound with teflon tubing over the >wires, or wrap the core in glass tape. I have also successfully used >teflon insulated, silver plated stranded wire for baluns. Voltage-type balun kits using T200-2 cores often came with fiberglass tape and teflon-insulated wire for just this reason. High voltages are less of a concern for current baluns, since you aren't transforming the voltages of the signal. But, with reactive loads, larger voltages (and hence, much higher currents in the antenna half to ground circuit, and thus higher core flux) are present. >>However, you are correct that current-type baluns provide better balance >>to the load than voltage-type, regardless of the reactance present. The >>ARRL Handbook no longer provides descriptions of voltage-type baluns. >>Current-type baluns are recommended. > >Sevich devotes an entire chapter in his book "Building and Using Baluns and >Ununs." to baluns for antenna tuners and recommends voltage baluns, >sorta. He goes to great pains to flatten response of the balun used by >McCoy in his original transmatch. However, there are 2 problems with the >voltage balun used in the antenna tuner. As the as the frequency is >increased, the phase shift in the transmission coiled transmission line is >no longer able to sustain a 4:1 ratio and the high frequency performance >falls off. The second problem is a result of the first. In an attempt to >extend the high frequency range, turns are removed from the balun until at >the lower frequency there is barely enough inductance to prevent the >primary current from flowing in the balun, decreasing the current to the >load and increasing losses. This condition becomes worse when working into >a high impedance load. As the load impedance increases, more primary >current flows in the balun as the impedance of the balun to choke the >primary current doesn't change and becomes a smaller ratio of the total >impedance. I made a bunch of voltage baluns, but finally gave up on >them. All the baluns I made would cover 160 through 15 or 80 through 10, >but not both. BTW the T184 size is a good compact powdered iron core to >use if you are into voltage baluns, as it has an inductive index higher >than any core smaller than 4 inches. Most voltage baluns I've seen use T200-2 cores. In fact, I have at least three 15-year old balun kits using these devices. They are meant as "2 kW" baluns, but would be reasonably efficient in QRP or Low Power service. I think I'll stick to current baluns, and use the balun kits as a source of teflon wire for my FT240-77 Guanella baluns.... Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 +++++++++++++++++++ Date: Fri, 18 Jan 2002 09:41:16 -0600 From: "George, W5YR" To: Bill Coleman Cc: Don Wilhelm , "Jonathan Taylor, K1RFD" , elecraft at mailman.qth.net Subject: Re: [Elecraft] Balun for KAT2 Bill Coleman wrote: > Third, none of the discussed baluns (with the exception of the coaxial > coil) performs well in the presence of reactive loads. Such loads can > cause core saturation, heating and additional loss, unless accounted for > in the design of the balun. Bill, I enjoyed reading your posting re baluns pro and con, but I have a problem with the statement above, *provided* that you are including current or choke baluns in the "discussed baluns" category. As I understand current or choke baluns used with coax - I use three of them to transition from ladder line to coax - they operate solely on the presence of common-mode current on the outer braid of coax. It is their inductive and resistive-loss effects that account for the reduction or elimination of this current. Thus, their effectiveness depends only upon the common-mode impedance of the outer-braid circuit. Differential-mode operation within the line is concealed by skin effect and in not involved in the common-mode operation of the line. This being the case, then, it is the differential-mode operation of the coax which is where the presence of a reactive load would be involved and/or the actual terminating impedance of the load would have an effect. None of the increased differential-mode current or voltage that could result from reactive loads would impact the common-mode impedance environment and thus stress the choke balun. In fact, one of the several major advantages of the W2DU balun, as well as the W1JR, for example, is their freedom from heating and saturation effects due to reactive loads that present impedances outside the design range of the balun. As Roy Lewallen has posted many times, and wrote in his classic article on baluns, the only current that the bead balun, for example, "sees" is the common-mode current, and except under extraordinary circumstances, that current is usually of a magnitude far below that which introduces core loss and heating problems with ferrites. It is true that bead baluns can be damaged at high power levels, especially with the balun placed at the antenna feedpoint where the common-mode current is a maximum. Under these QRO conditions, larger beads are frequently used nearest the antenna connection to deal with the high current level and attendent loss in the beads. So, please point out what I am missing or misinterpreting here. To summarize, it is my understanding that choke or current baluns respond only to common-mode current which is independent of the differential-mode impedance presented by the antenna load. Thus, their design and operation are unaffected by load impedance, even when highly reactive. Only the common-mode circuit impedance is involved in balun operation and design. I read all your postings and always find them informative. Rarely do I find a point, such as this, on which we apparently hold different views. 72/73/oo, George W5YR - the Yellow Rose of Texas ++++++++++++++++ Date: Fri, 18 Jan 2002 10:03:36 -0600 To: elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] Balun for KAT2 Bill Coleman, AA4LR, wrote: >Coiled-coax type choke baluns are probably the lowest loss of the bunch. >They are cheap, but their frequency range is somewhat restricted, and >they can be bulky and heavy. Not to mention that to get the most from the coiled-coax balun, it should be wound in a single-layer solenoid, rather than being 'scramble-wound' as most of us are wont to do. I believe I have an article on a study conducted upon coiled-coax baluns, if anyone would like to see it. If there are enough requests, I may put it up on my web site for a period of time, maybe a month. 73 - Tom Hammond N0SS +++++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 Date: Fri, 18 Jan 2002 11:25:18 -0500 To: "George, W5YR" From: Bill Coleman Cc: "Don Wilhelm" , "Jonathan Taylor, K1RFD" , On 1/18/02 10:41 AM, George, W5YR at w5yr at att.net wrote: >Bill Coleman wrote: > >> Third, none of the discussed baluns (with the exception of the coaxial >> coil) performs well in the presence of reactive loads. Such loads can >> cause core saturation, heating and additional loss, unless accounted for >> in the design of the balun. > >Bill, I enjoyed reading your posting re baluns pro and con, but I have a >problem with the statement above, *provided* that you are including current >or choke baluns in the "discussed baluns" category. Current baluns was all I was talking about. >As I understand current or choke baluns used with coax - I use three of >them to transition from ladder line to coax - they operate solely on the >presence of common-mode current on the outer braid of coax. It is their >inductive and resistive-loss effects that account for the reduction or >elimination of this current. Thus, their effectiveness depends only upon >the common-mode impedance of the outer-braid circuit. Differential-mode >operation within the line is concealed by skin effect and in not involved >in the common-mode operation of the line. Right. It's essentially the same as the W1JR balun, except that W1JR winds the coax on a toroidial core. The only difference is you need fewer turns to get sufficient inductance because of the permeability of the core. >This being the case, then, it is the differential-mode operation of the >coax which is where the presence of a reactive load would be involved >and/or the actual terminating impedance of the load would have an effect. >None of the increased differential-mode current or voltage that could >result from reactive loads would impact the common-mode impedance >environment and thus stress the choke balun. However, you have to account for the fact that the choking impedance (as it true in all current balun designs), is shunted across half of the antenna element to ground (via the coax sheild). This circuit faces potentially half of the antenna voltage (provided the antenna is balanced), and so some current will flow through the choke. With sufficient inductance, this current ought to be small, but if the balun was designed for resistive loads and is suddenly faced with higher voltages due to reactive loads, failures can occur. The coiled-coax balun won't fail easily, which was my point. >In fact, one of the several major advantages of the W2DU balun, as well as >the W1JR, for example, is their freedom from heating and saturation effects >due to reactive loads that present impedances outside the design range of >the balun. There are W2DU-type designs that fail easily due to core heating. You can do the same with the W1JR-type design, too. The old Hy-gain BN86 is a W2DU-type design, no? There's a large track record of failures of this type balun at full rated amatuer power. The basic problem is one of core heating to the loss tangential point, which then proceeds to the Curie temperature. Since the coiled-coax balun has no ferrite core, such failure modes are impossible. >As Roy Lewallen has posted many times, and wrote in his classic article on >baluns, the only current that the bead balun, for example, "sees" is the >common-mode current, and except under extraordinary circumstances, that >current is usually of a magnitude far below that which introduces core loss >and heating problems with ferrites. Isn't roy forgetting that the balun is also shunted across half the antenna element to ground? >It is true that bead baluns can be damaged at high power levels, especially >with the balun placed at the antenna feedpoint where the common-mode >current is a maximum. Under these QRO conditions, larger beads are >frequently used nearest the antenna connection to deal with the high >current level and attendent loss in the beads. If there's no flux in the choke, according to Lewallen, where's the loss in the beads coming from? The main problem with main of these designs is that the beads are often potted and sealed. Since Ferrite doesn't disappate heat well to start with, having it wrapped in a plastic blanket makes the problem worse. Once they start to heat, the heat increases the losses, which can snowball to the Curie point. >So, please point out what I am missing or misinterpreting here. To >summarize, it is my understanding that choke or current baluns respond only >to common-mode current which is independent of the differential-mode >impedance presented by the antenna load. Thus, their design and operation >are unaffected by load impedance, even when highly reactive. Only the >common-mode circuit impedance is involved in balun operation and design. Everything you say is true about the operating of the balun. Except that it also acts as a coil shunted across one antenna element to ground. If we could draw a circuit and separate the inner coax braid carrying the differential currents from the outer braid, we'd end up with three coils. Two are coupled differentially, and have no net flux. The third, however, is from one antenna element to the ground of the coax sheild. When properly designed, there isn't much current involved here. There are unfortunate cases where use exceeds the design. >I read all your postings and always find them informative. Rarely do I find >a point, such as this, on which we apparently hold different views. Thanks! Perhaps we can both learn something here -- I'm always eager to learn something new. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 ++++++++++++++++++ Subject: Re: [Elecraft] Balun for KAT2 Date: Fri, 18 Jan 2002 14:12:28 -0500 To: "Stuart Rohre" , "Bill Coleman" , "Don Wilhelm" , "Jonathan Taylor, K1RFD" , From: Bill Coleman On 1/18/02 2:00 PM, Stuart Rohre at rohre at arlut.utexas.edu wrote: >Bill has a good summary of the detailed balun issues, but the original >discussion downplaying baluns missed the point of using one with the K2 was >to facilitate true balanced feed to a parallel line feeder, typically at >some step up ratio other than 1:1 of the coax chokes or bead baluns. If you have a reactive load (which is typical of a single all-band doublet fed with open wire), then you really don't care. You're not going to get the 4:1 or 9:1 transformation you might hope for with a voltage balun anyway. So, you might as well use a way-over-ratings (to avoid any possibility of core heating) 1:1 balun and let the KAT2 figure out the impedances. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 +++++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "George, W5YR" , "Bill Coleman" Cc: "Jonathan Taylor, K1RFD" , Subject: Re: [Elecraft] Balun for KAT2 Date: Sat, 19 Jan 2002 00:52:16 -0500 Bill and all, It is true that the antenna half the antenna voltage is shunted across the choking impedance to ground. This will be on the side of the antenna that the shield (or its extension through the balun) is connected. In reality, this should be an effective RF choke, and SHOULD have enough inductance to be negligible - otherwise it is not working as a proper balun. I think the real point here is that bad baluns exist and sadly, some have been marketed commercially. A good balun does have that sufficient impedance, and will work just fine - provided it is not used outside its design limits (now if we just knew what those limits were - and we often do not). Here is the big BUT in all this IMHO - if the choking impedance is not adequate, the presence of a balun can upset antenna balance just as much a not having a balun in the first place. And it is all due to placing that RF choke from one side of the antenna to ground and finding out that the choke is too small to do the job properly. I believe the original question did have to do with using a balun to feed 450 ohm line and a multiband antenna, so I pose this retorical question: If you were designing an RF circuit having an impedance of 4000 ohms - would you attempt to put an RF choke of 1000 ohms reactance to ground in that circuit? Certainly not - because it would shunt a bunch of your signal straight to ground. 4000 ohms is not unusual in a multiband doublet antenna situation, and many baluns designed around a 50 ohm environment have much less than 1000 ohms inductive reactance (on the lower bands especially). So without a lot of thought and calculation, one never knows if a particular balun will be a benefit or not. One could address the situation by using a balun with a lot of inductance on the low frequency bands and one with fewer turns (or beads, etc.) on the higher bands, but then we have come to expect all baluns to be broadband (at least 1.8 thru 30 MHz). So again in the old words of Sportin' Life: "It ain't necessarily so!" I prefer to make the solution match the problem and I never presume that same solution will address all problems. If that were true we could fix all the world's problems with just a 'spoonful of sugar'. If one wants to use the balun with very low losses - use the quarter wave line balun (look at baluns for VHF if you need to find a description). It is very effective and has been around for ages, but only works on the band for which it is designed - and at low frequencies, it gets quite long. 73, Don W3FPR ----- Original Message ----- > > However, you have to account for the fact that the choking impedance (as > it true in all current balun designs), is shunted across half of the > antenna element to ground (via the coax sheild). This circuit faces > potentially half of the antenna voltage (provided the antenna is > balanced), and so some current will flow through the choke. > > With sufficient inductance, this current ought to be small, but if the > balun was designed for resistive loads and is suddenly faced with higher > voltages due to reactive loads, failures can occur. +++++++++++++++++ Date: Sat, 19 Jan 2002 05:50:32 -0500 To: "Don Wilhelm" From: Charles Greene Subject: Re: [Elecraft] Balun for KAT2 Cc: "George, W5YR" , "Bill Coleman" , "Jonathan Taylor, K1RFD" , At 12:52 AM 1/19/2002 -0500, Don Wilhelm wrote: Here's a question that occurred to me. With a 1:1 coaxial or a W1JR balun, will that disturb balance of the initially balance transmission line? Take a case where the balun has an impedance of 1000 ohms to ground and the transmission line at point where the balun is inserted also has an impedance of 1000 ohms to ground, you are shunting one side of the transmission line to ground, but the inside is shunted to Zo which is 50 ohms. This would cause a small unbalance it seems. +++++++++++++++++++ Date: Sat, 19 Jan 2002 07:15:20 -0600 To: Charles Greene , elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] Balun for KAT2 I wrote: >>I believe I have an article on a study conducted upon coiled-coax baluns, >>if anyone would like to see it. If there are enough requests, I may put >>it up on my web site for a period of time, maybe a month. Then Charles Greene, W1CG, replied >I'd like to see it. I Apparently a number of othrs would, too. I'll risk my 'good boy' points with Eric and post the entire (only 9K) article here (reply to you, Charles). Enjoy. 73 - Tom N0SS _______________ Ed Gilbert, WA2SRQ eyg at hpnjlc.njd.hp.com ------------------------------------------------------------------------- Having access to a Hewlett-Packard 4193A vector impedance meter at work, I have made measurements on a number of baluns, coaxial and otherwise. For my beams I was particularly interested how many turns and on what diameter are optimum for air core coaxial baluns, and what the effect of bunching the turns was (formless). Using the remote programming capability of the HP4193A along with an instrument controller, I measured the magnitude and phase of each balun's winding impedance at 1 MHz intervals from 1 to 35 MHz. For comparison, I also made measurements on a commercial balun which consists of a number of ferrite beads slipped over a short length of coax. I've appended some of these measurements so you can draw your own conclusions. PVC pipe was used for coil forms. The 4-1/4 inch diameter baluns were wound on thin-walled PVC labeled "4 inch sewer pipe". This material makes an excellent balun form. It's very light weight and easy to work with, and I obtained a 10 foot length at the local Home Depot for about 3 dollars. The 6-5/8 inch diameter forms are 6 inch schedule 40 PVC pipe which is much thicker, heavier, and more expensive. Each test choke was close-wound on a form as a single-layer solenoid using RG-213 and taped to hold the turns in place. The lengths of cable were cut so there was about 2 inches excess at each end. This allowed just enough wire at the ends for connections to the HP4193A's probe tip. After data was collected for each single-layer configuration, the PVC form was removed, the turns were bunched together and taped formless, and another set of measurements was taken. I have only included the "bunched" measurements in the table for one of the baluns, but the trend was the same in each case. When compared to the single-layer version of the same diameter and number of turns, the bunched baluns show a large downward shift in parallel self-resonance frequency and poor choking reactance at the higher frequencies. Interpreting the Measurements ----------------------------- All the baluns start out looking inductive at low frequencies, as indicated by the positive phase angles. As the frequency is increased, a point is reached where the capacitance between the windings forms a parallel resonance with the coil's inductance. Above this frequency, the winding reactance is reduced by this capacitance. The interwinding capacitance increases with the number of turns and the diameter of the turns, so "more is not always better". The effects of a large increase in interwinding capacitance is evident in the measurements on the balun with the bunched turns. This is probably a result of the first and last turns of the coil being much closer together than the single-layer coil. An important requirement of these baluns is that the magnitude of the winding reactance be much greater than the load impedance. In the case of a 50 ohm balanced antenna, the balun's winding impedance is effectively shunted across one half the 50 ohm load impedance, or 25 ohms. A reasonable critera for the balun's winding impedance for negligible common mode current in the shield is that it be at least 20 times this, or 500 ohms. The measurements show, for example, that 6 turns 4-1/4 inches in diameter meet this criteria from 14 to 35 MHz. The measurement data also reveals the power loss these baluns will exhibit. Each of the measurement points can be transformed from the polar format of the table to a parallel equivalent real and reactive shunt impedance. The power dissipated in the balun is then the square of the voltage across it divided by the real parallel equivalent shunt impedance. While this calculation can be made for each measurement point, an approximate number can be taken directly from the tables at the parallel resonance points. At 0 degrees phase angle the magnitude numbers are pure resistive. I didn't record the exact resonance points, but it can be seen from the tables that the four single-layer baluns are all above 15K ohms, while the ferrite bead balun read about 1.4K. These baluns see half the load voltage, so at 1500 watts to a 50 ohm load, the power dissipated in the coaxial baluns will be less than 1.3 watts, and the ferrite bead balun will dissipate about 13.4 watts (neglecting possible core saturation and other non-linear effects). These losses are certainly negligible. At 200 ohms load impedance, the losses are under 5 watts for the coaxial baluns and 53.6 watts for the ferrite beads. Conclusions ----------- - A 1:1 coaxial balun with excellent choking reactance for 10 through 20 meters can be made by winding 6 turns of RG-213 on inexpensive 4 inch PVC sewer pipe. - For 40 or 30 meters, use 12 turns of RG-213 on 4 inch PVC sewer pipe. - Don't bunch the turns together. Wind them as a single layer on a form. Bunching the turns kills the choking effect at higher frequencies. - Don't use too many turns. For example, the HyGain manuals for my 10 and 15 meter yagis both recommend 12 turns 6 inches in diameter. At the very least this is about 3 times as much coax as is needed, and these dimensions actually give less than the desired choking impedance on 10 and 15 meters. Measurements ------------ Magnitude in ohms, phase angle in degrees, as a function of frequency in Hz, for various baluns. ----- ---------- ---------- ---------- ---------- ---------- ---------- 6 Turns 12 Turns 4 Turns 8 Turns 8 Turns Ferrite Freq 4-1/4 in 4-1/4 in 6-5/8 in 6-5/8 in 6-5/8 in beads MHz sngl layer sngl layer sngl layer sngl layer bunched (Aztec) ----- ---------- ---------- ---------- ---------- ---------- ---------- Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase 1.0 26 88.1 65 89.2 26 88.3 74 89.2 94 89.3 416 78.1 2.0 51 88.7 131 89.3 52 88.8 150 89.3 202 89.2 795 56.1 3.0 77 88.9 200 89.4 79 89.1 232 89.3 355 88.9 1046 39.8 4.0 103 89.1 273 89.5 106 89.3 324 89.4 620 88.3 1217 26.6 5.0 131 89.1 356 89.4 136 89.2 436 89.3 1300 86.2 1334 14.7 6.0 160 89.3 451 89.5 167 89.3 576 89.1 8530 59.9 1387 3.6 7.0 190 89.4 561 89.5 201 89.4 759 89.1 2120 -81.9 1404 -5.9 8.0 222 89.4 696 89.6 239 89.4 1033 88.8 1019 -85.7 1369 -15.4 9.0 258 89.4 869 89.5 283 89.4 1514 87.3 681 -86.5 1295 -23.7 10.0 298 89.3 1103 89.3 333 89.2 2300 83.1 518 -86.9 1210 -29.8 11.0 340 89.3 1440 89.1 393 89.2 4700 73.1 418 -87.1 1123 -35.2 12.0 390 89.3 1983 88.7 467 88.9 15840 -5.2 350 -87.2 1043 -39.9 13.0 447 89.2 3010 87.7 556 88.3 4470 -62.6 300 -86.9 954 -42.7 14.0 514 89.3 5850 85.6 675 88.3 2830 -71.6 262 -86.9 901 -45.2 15.0 594 88.9 42000 44.0 834 87.5 1910 -79.9 231 -87.0 847 -48.1 16.0 694 88.8 7210 -81.5 1098 86.9 1375 -84.1 203 -87.2 778 -51.8 17.0 830 88.1 3250 -82.0 1651 81.8 991 -82.4 180 -86.9 684 -54.4 18.0 955 86.0 2720 -76.1 1796 70.3 986 -67.2 164 -84.9 623 -45.9 19.0 1203 85.4 1860 -80.1 3260 44.6 742 -71.0 145 -85.1 568 -51.2 20.0 1419 85.2 1738 -83.8 3710 59.0 1123 -67.7 138 -84.5 654 -34.0 21.0 1955 85.7 1368 -87.2 12940 -31.3 859 -84.3 122 -86.1 696 -49.9 22.0 3010 83.9 1133 -87.8 3620 -77.5 708 -86.1 107 -85.9 631 -54.8 23.0 6380 76.8 955 -88.0 2050 -83.0 613 -86.9 94 -85.5 584 -57.4 24.0 15980 -29.6 807 -86.3 1440 -84.6 535 -86.3 82 -85.0 536 -58.8 25.0 5230 -56.7 754 -82.2 1099 -84.1 466 -84.1 70 -84.3 485 -59.2 26.0 3210 -78.9 682 -86.4 967 -83.4 467 -81.6 60 -82.7 481 -56.2 27.0 2000 -84.4 578 -87.3 809 -86.5 419 -85.5 49 -81.7 463 -60.5 28.0 1426 -85.6 483 -86.5 685 -87.1 364 -86.2 38 -79.6 425 -62.5 29.0 1074 -85.1 383 -84.1 590 -87.3 308 -85.6 28 -75.2 387 -63.8 30.0 840 -83.2 287 -75.0 508 -87.0 244 -82.1 18 -66.3 346 -64.4 31.0 661 -81.7 188 -52.3 442 -85.7 174 -69.9 9 -34.3 305 -64.3 32.0 484 -78.2 258 20.4 385 -83.6 155 -18.0 11 37.2 263 -63.2 33.0 335 -41.4 1162 -13.5 326 -78.2 569 -0.3 21 63.6 212 -58.0 34.0 607 -32.2 839 -45.9 316 -63.4 716 -57.6 32 71.4 183 -40.5 35.0 705 -58.2 564 -56.3 379 -69.5 513 -72.5 46 76.0 235 -29.6 +++++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "Elecraft List" , "Charles Greene" Subject: Re: [Elecraft] Balun for KAT2 Date: Sat, 19 Jan 2002 13:43:45 -0500 Chas, In my prior reply, I missed the first question - 'will that disturb balance of the initially balance(d) transmission line?' I think not - and my reasoning is that the balance of the transmission line is determined by the antenna connected to the balanced line - it doesn't work the other way around. i.e. you cannot force balance into an antenna and feedline system unless it is balanced in the first place. To do otherwise would be like fooling Mother Nature. (herein is the fallacy of trying to force balance with a balun - I believe the balun may actually upset things even more. A balun to decouple the coax outer shield from the antenna is a different situation -that part works just fine). I have always believed (and found to be true) that the balance on an antenna starts at the ends of the antenna where the current (of necessity) will be zero. As one travels back along the antenna elements from each end, somewhere you will encounter a feedline. Well, if the currents at this feedline attachment point are equal and opposite, the feedline will be balanced - and if they are not equal and opposite, there is nothing to be done but either accept the imbalance or change the position of the feedpoint. If you want a bit of verification on this point - check out L.B. Cebik's website www.cebik.com and see what he has to say about obtaining balance with an OCF antenna - both he and I say it just will not happen. 73, Don W3FPR ----- Original Message ----- From: "Charles Greene" > Here's a question that occurred to me. With a 1:1 coaxial or a W1JR balun, > will that disturb balance of the initially balance transmission line? ... +++++++++++++++