Re: [Elecraft] More Balanced Current Measurements - Voltage Balun
I had previously posted some RF Current data using an MFJ-835 Balanced RF Current meter. I measured the amount of current flowing in each side of my ladder line I'm pretty sure that unit doesn't actually indicate balance. I'm pretty sure it only indicates equal currents by sampling scalar currents in each conductor. I'll look into that, but everything in the manual seems to indicate it is a scalar measurement of current in each conductor. Anyway the important point is that it is possible to have equal currents in each conductor and have perfect UNbalance. To measure balance we have to measure phase, not just scalar currents. We also have to either measure current balance at two points some large fraction of a wave apart (like 1/8th or 1/4 wave), or measure BOTH voltage and current balance at one point. and compared the Johnson Matchbox, the internal KAT3 antenna tuner with the Elecraft BL2 balun in both the 4-to-1 and 1-to-1 positions, and a direct connection from the KAT3 to the ladder line with no balun. Tonight, I came across a 4-to-1 voltage balun left over from the days of the Ultimate Transmatch (QST July, 1970 - wow! - that is a long time ago but seems like yesterday). There are only a few cases where we might be better off using a 4:1 balun rather than a 1:1 balun to transform random impedances to a tuner. Those cases would be where the antenna system (at the balun connection point) presents a reasonable impedance to the balun, the balun is designed for that frequency and impedance, and the antenna system balance presented to the balun is pretty good. It would be even rarer to need or want a voltage balun. I can't think of many of any cases where I would want to use a balanced voltage source to feed a simple antenna. As a matter of fact I virtually never use a 4:1 unless I'm matching a folded dipole to coax. Anyway, I put the voltage balun in line and repeated the measurements. Here are my conclusions based on my results: 1) Without the MFJ 835 current meter, I would have been happy with any of the configurations. All of them had a perfect 1-to-1 SWR when matched. All of them resulted in good QSOs. 2) The Johnson Matchbox has the best balance and least loss on all bands. 3) A balun on the output of an unbalanced tuner is a compromise and there is loss there. 4) The BL2 has good balance on all bands 160m to 6m but gets very hot on some bands indicating loss. I have received reports that the Johnson MB is several S units better than the balun on some bands. 5) The voltage balun works pretty well on 160m, 80m, and 40m but is poor on 30m and higher. It is useless on 6m. 6) The direct connection had very poor balance on some bands. So, IMHO, a balanced tuner is the best matching device for a balanced antenna fed with ladder line. We must find a way to convince Elecraft to offer a balanced version of the KAT3. As a general rule it is far less expensive to build a good 1:1 balun to use on the output of a unbalanced tuner than it is to build a balanced tuner. This is especially true if the load is not perfectly balanced, or on higher frequencies. When I built high power tuners for a 25 kW AM SW BC station, I looked at all options and used 1:1 baluns on the matching system output. It was several thousands of dollars cheaper than using a balanced network and worked just as well. I'd encourage them to build a good 1:1 balun, or perhaps two...one for lower bands and one for higher bands. The expense of a balanced tuner generally just isn't worth it, and a 4:1 is almost never needed. I'll look at that balance indicator if I can get my hands on one. It might not be, but from the manual it sounds like it is a scalar device that does not consider phase. 73 Tom ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] More Balanced Current Measurements - Voltage Balun
Heat means LOST POWER. Virtually all baluns like the BL2 use Fair-Rite #61 (or something quite similar). Download http://audiosystemsgroup.com/RFI-Ham.pdf and study Fig 6, the loss characteristics of Fair-Rite #61. The loss begins to rise above 10 MHz, and it isn't pretty above about 20 MHz. The figure referred to is using the material as part of an RFI suppression choke where you want attenuation at RF frequencies. I think you'll find that when the Type 61 material is used as a transformer, it will have very low loss if designed properly. See Sevick's book on baluns and ununs. But I think that even a well-designed transformer will have maybe 1-2% loss. At 100 watts, that is 1-2 watts which will cause the transformer to heat up. Just dissipate 1-watt in a resistor with your DC power supply and feel the heat. Phil - AD5X ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] More Balanced Current Measurements - Voltage Balun
Phil, Phil, A current balun *is* a choke, not a transformer. That is true for both the 1:1 and 4:1 baluns. OTOH, a voltage balun is a transformer, but I am not sure why anyone would want to use one except for special applications. 73, Don W3FPR Phil Debbie Salas wrote: The figure referred to is using the material as part of an RFI suppression choke where you want attenuation at RF frequencies. I think you'll find that when the Type 61 material is used as a transformer, it will have very low loss if designed properly. See Sevick's book on baluns and ununs. But I think that even a well-designed transformer will have maybe 1-2% loss. At 100 watts, that is 1-2 watts which will cause the transformer to heat up. Just dissipate 1-watt in a resistor with your DC power supply and feel the heat. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] More Balanced Current Measurements - Voltage Balun
The figure referred to is using the material as part of an RFI suppression choke where you want attenuation at RF frequencies. I think you'll find that when the Type 61 material is used as a transformer, it will have very low loss if designed properly. Even 73 materials can have low loss if the transformer has high enough impedance compared to the load impedance and it is a true transmission line transformer, but materials with a lower loss tangent are generally better if the transformer has enough impedance across each winding. I think that even a well-designed transformer will have maybe 1-2% loss. At 100 watts, that is 1-2 watts which will cause the transformer to heat up. Just dissipate 1-watt in a resistor with your DC power supply and feel the heat. It's all about the surface area and the dissipation. Many even wrongly call heat saturation, when it is almost always nothing more than dissipation from the resistive part of the impedance and the voltage across (or current through) that resistance. As a matter of fact most baluns and transformers operating at more than a few watts heat long before they come close to saturating. For example the balun in the ATR30 tuner overheats to the point where it reaches the core temperature limit at just 100 watts of dissipation for about one minute. The heat is not caused by saturation unless you are running a 30 kW pulse transmitter with low duty cycle into a particular load. Heat is almost always caused by resistive losses, and the balun will typically handle 2-3 kW of CW without undue heating. 50 watts of loss out of 2 kW will make it get VERY warm, but it is insignificant loss and not saturation. Put heat it into perspective of the applied power and the area dissipating heat. Think of how hot a 7 watt light bulb gets and the surface area of the bulb. Now think of a standard 100 watt bulb, or a standard 40 watt florescent lamp. All of them mostly make heat from the applied power. It is a surface area and power dissipation problem so we have to use common sense by comparing it to similar size things. A final thought. The worse way in the world to determine balun efficiency is with a signal report. First, there is a time problem on skywave. By the time we change baluns or tuners propagation can change. Second, either locally or on skywave any change in balance can change antenna patterns. Groundwave is particularly USELESS with a horizontally polarized antenna. I know of at least three tests where people compared tuner or balun configurations on groundwave using horizontally polarized antennas. The results of those tests are meaningless, because a change in feeder unbalance would significantly affect ground wave field strength. This is because only the vertical component can propagate over any distance along the earth, or does well near the earth's surface. The worse system for balance will produce the strongest local signal when using horizontally polarized antennas at HF. We have to be careful what we conclude or assume. Even when we are careful and use good methods, there can be mistakes or things we miss. 73 Tom ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] More Balanced Current Measurements - Voltage Balun
On Thu, 14 Aug 2008 06:37:15 -0500, Phil Debbie Salas wrote: Heat means LOST POWER. Virtually all baluns like the BL2 use Fair-Rite #61 (or something quite similar). Download http://audiosystemsgroup.com/RFI-Ham.pdf and study Fig 6, the loss characteristics of Fair-Rite #61. The loss begins to rise above 10 MHz, and it isn't pretty above about 20 MHz. The figure referred to is using the material as part of an RFI suppression choke where you want attenuation at RF frequencies. NO! The figure shows the FUNDAMENTAL PROPERTIES OF THE MATERIAL as published on the data sheet by the manufacturer, Fair-Rite. See the text of the tutorial for a discussion of what those data mean. I think you'll find that when the Type 61 material is used as a transformer, it will have very low loss if designed properly. That can be a big if. It depends on frequency, the parts used, the windings, and the impedances. And as Tom observes, it's not easy to measure with instrumentation commonly available to hams. 73, Jim Brown K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] More Balanced Current Measurements - Voltage Balun - Remote Tuner
YES! PLEASE, Please...a remote version of one of the 100W Elecraft antenna tuners is greatly needed. Even more so than a 500 - 1000 W amp. I get a chuckle every time I read that someone worked rare DX with their K3/100 and KAT3 combo using 100 ft of 50 ohm coax out to a multiband vertical o r dipole. 73, Henry - K4TMC K2/100 #3137 and K3/100 #98 ** Looking for a car that's sporty, fun and fits in your budget? Read reviews on AOL Autos. (http://autos.aol.com/cars-Volkswagen-Jetta-2009/expert-review?ncid=aolaut00030 7 ) ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] More Balanced Current Measurements - Voltage Balun
I had previously posted some RF Current data using an MFJ-835 Balanced RF Current meter. I measured the amount of current flowing in each side of my ladder line and compared the Johnson Matchbox, the internal KAT3 antenna tuner with the Elecraft BL2 balun in both the 4-to-1 and 1-to-1 positions, and a direct connection from the KAT3 to the ladder line with no balun. Tonight, I came across a 4-to-1 voltage balun left over from the days of the Ultimate Transmatch (QST July, 1970 - wow! - that is a long time ago but seems like yesterday). Anyway, I put the voltage balun in line and repeated the measurements. Here are my conclusions based on my results: 1) Without the MFJ 835 current meter, I would have been happy with any of the configurations. All of them had a perfect 1-to-1 SWR when matched. All of them resulted in good QSOs. 2) The Johnson Matchbox has the best balance and least loss on all bands. 3) A balun on the output of an unbalanced tuner is a compromise and there is loss there. 4) The BL2 has good balance on all bands 160m to 6m but gets very hot on some bands indicating loss. I have received reports that the Johnson MB is several S units better than the balun on some bands. 5) The voltage balun works pretty well on 160m, 80m, and 40m but is poor on 30m and higher. It is useless on 6m. 6) The direct connection had very poor balance on some bands. So, IMHO, a balanced tuner is the best matching device for a balanced antenna fed with ladder line. We must find a way to convince Elecraft to offer a balanced version of the KAT3. Maybe something along the lines of Zack Lau's QRP Balanced Transmatch on the ARRL website (in the TIS section. The balun is on the input side and operates near the design impedances). If you want to peek at the data itself, it's on my website. The link is on QRZ.COM. The sum column is an indication of the total current in both sides. The higher the number, the better. The difference column is an indication of balance. The smaller the number, the better. 73, John W2XS -- View this message in context: http://n2.nabble.com/More-Balanced-Current-Measurements---Voltage-Balun-tp723337p723337.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] More Balanced Current Measurements - Voltage Balun
So, IMHO, a balanced tuner is the best matching device for a balanced antenna fed with ladder line. We must find a way to convince Elecraft to offer a balanced version of the KAT3. Better yet, we must convince them to make the balanced tuner in a remote configuration so it can be outside in the elements with 50 ohm coax between it and the K3. My BL2 also gets mighty hot on some bands at 100W when feeding ladderline. Of course the line length can be adjusted, but an external automatic balanced tuner would be MUCH nicer! (hint, hint) ... Craig AC0DS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] More Balanced Current Measurements - Voltage Balun
On Wed, 13 Aug 2008 21:32:46 -0600, Craig D. Smith wrote: My BL2 also gets mighty hot on some bands at 100W when feeding ladderline. Heat means LOST POWER. Virtually all baluns like the BL2 use Fair-Rite #61 (or something quite similar). Download http://audiosystemsgroup.com/RFI-Ham.pdf and study Fig 6, the loss characteristics of Fair-Rite #61. The loss begins to rise above 10 MHz, and it isn't pretty above about 20 MHz. 73, Jim Brown K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
