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#1
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Google search for "balanced-balanced " or "Richard Measures" (author of
article). I built one, it worked great. |
#2
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On Sun, 24 Jul 2005 11:32:37 -0700, "greg knapp 5"
wrote: I have decided to erect an 80 meter dipole at 70 feet fed with 450 or 600 ohm open wire, for use on ALL HF bands between 80 and 10 meters. Power output will be 1000W CW and 1200W PEP. (1) Which is the better setup and why: a Ten Tec 238B unbalanced tuner with a DX Engineering 1:1 balun on antenna side of tuner OR a Palstar BT1500BAL balanced tuner? (2) Also, if I later decide to erect an inverted L for 160/80, can I use a balanced tuner with a DX Engineering 1:1 balun put on antenna side of tuner, but reversed in direction (converting unbalanced to balanced), or need I get a different tuner? (3) In a perfect world, I'd buy both tuners (one for balanced and one for unbalanced), but I can't afford it. Also, if I go with the unbalanced tuner, will the balun waste a ton of RF in heat and loss? (4) I made a similar post on the Ten Tec List, and received lots of advice on point designs, but not the COMPARISON data I was looking for that will help me make the final decision to go with a balanced tuner vs an unbalanced (with balun) tuner. (5) I have plenty of room, would it make any difference if I put a 160 meter dipole instead? Thanks & 73, Greg, N6GK Have not seen any published tests comparing balanced vs. unbalanced tuners, so any comparisons will probably be theoretical in nature. Also, instread of the dx engineering balun, you might look at a w2du-style balun -- see his article at http://www.w2du.com/Reflection2.html bob k5qwg |
#3
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I read the article you cited, looked at the QST article on the 238A (noting
the size of the 3.5 Kv peak capacitor), and looked at the Palstar webpage at the "inside" shot of the Palstar BT1500BAL (huge capacitor by comparison, rated at 4.5 KV; but noted it had a ferrite input balun) and also read W8JI's comparison of balun loss that showed the difference between the various baluns...with the DX Engineering, coiled coax (20 ft "scrambled"), and 60-foot "solenoid", coming out the lowest loss, and with the DXE one being the lowest...but that was at a LOW SWR! If I had a low SWR on all bands why would I need a tuner? I know it will be pretty high SWR on some bands, so what then? I guess that is what MY REAL QUESTION boils down to...although I like the "single resonant" L-type Ten Tec 238 unbalanced tuner (and it would work great with my future inverted L), it needs a balun to match it to the open wire feed. Will the balun, at HIGH SWRs, just burn up my watts in heat and smoke? Versus, a balanced tuner (Johnson, Palstar), which doesn't need a balun (just a small one at input, which is at low SWR and negligible loss), and does not overheat. So what I am wrestling with is which configuration AND WHY: (1) 238B to DXE 1:1 current balun to open wire versus (2) Palstar BT1500BAL to open wire. As I see it from all the answers I've received, there are people with strong opinions on both sides, that have just given me their conclusion: do x or do y. But what I am still missing is WHY do x or y, and how they bounce off one another. FOR INSTANCE, WHICH COMBO, (1) OR (2) WILL GIVE THE LOWEST LOSS WHEN FEEDING A BALANCED ANTENNA AT AN 8:1 SWR? HOW MUCH LOWER...LOSS 100 WATTS FOR ONE AND 125 FOR THE OTHER? That is what I don't understand yet. One gentleman did address my question of whether I could feed an Inverted L (like on 160) with a balanced tuner if I used a balun to change the unbalanced feed from the antenna to a balanced feed connected the output of the balanced tuner, saying don't, but why not? Does this mean that a balanced tuner can NEVER be used for UNbalanced loads through use of a balun? Another gentleman pointed out that most people just go unbalanced and don't worry about the heat/loss in the balun...or change the length of the feed line slightly (per Cecil's method) until you get a "happy" length the balun can handle, and then buy the most rugged balun you can get to handle the mismatches. CONCLUSIONS SO FAR: As I see it, the 238B has versatility in that it can do both balanced and unbalanced (with a good external balun instead of its internal voltage balun), but the external balun will heat up and could even fail at 1200 watts to a feed line feeding some mismatched frequencies. But I could lengthen/shorten the balanced feed line to adjust it I guess, looking for its happy spot! On the other hand, the PALSTAR will work great with unbalanced lines (no lossy balun), even at high SWR, but it doesn't do unbalanced lines (although one person mentioned the capacitor might be too small for some situations--but I compared it and it seems to be larger and higher rated (4.5 KV) than the Ten Tec). From your comments I gather that almost any tuner or tuner-balun combo will do great at LOW SWR...but I don't need a tuner for those situations. It's when the SWR gets up higher, like 8:1 or 16:1 that I am concerned about with 1200 watts. In ARRL tests, the Palstar handled that OK, but no such tests for a 238B handling balanced lines (only unbalanced lines a few years back in QST). And what about the DXE, which W8JI tests highly rated, but (if I read the tests right) the tests were done at approx. 1.5 to 1 SWR...no where near the 8 to 1 that I am envisioning. Some of you have said the balun will heat up or even burn up (although I understand the DXE is supposed to be rugged enough to only heat up), but doesn't that rob me of all my power--heat is not a good thing! And, if both will work, to some degree (barring the burnout of the balun), is the 238B the way to go because I can ALSO do unbalanced lines for other antennas? I guess if I never wanted to have any unbalanced antennas in the future, I'd go the balanced tuner and be done with it. But if the loss through the 238B and DXE Tuner Balun would not be substantially greater than the Balanced Tuner, but will permit me to match unbalanced lines too for future antennas, then that sure seems the way to go (and adjust the feed line length to best match). What do you all think? And thanks for you many replies that have brought me this far so far! 73, Greg N6GK Greg, N6GK "Bob Miller" wrote in message ... On Sun, 24 Jul 2005 11:32:37 -0700, "greg knapp 5" wrote: I have decided to erect an 80 meter dipole at 70 feet fed with 450 or 600 ohm open wire, for use on ALL HF bands between 80 and 10 meters. Power output will be 1000W CW and 1200W PEP. (1) Which is the better setup and why: a Ten Tec 238B unbalanced tuner with a DX Engineering 1:1 balun on antenna side of tuner OR a Palstar BT1500BAL balanced tuner? (2) Also, if I later decide to erect an inverted L for 160/80, can I use a balanced tuner with a DX Engineering 1:1 balun put on antenna side of tuner, but reversed in direction (converting unbalanced to balanced), or need I get a different tuner? (3) In a perfect world, I'd buy both tuners (one for balanced and one for unbalanced), but I can't afford it. Also, if I go with the unbalanced tuner, will the balun waste a ton of RF in heat and loss? (4) I made a similar post on the Ten Tec List, and received lots of advice on point designs, but not the COMPARISON data I was looking for that will help me make the final decision to go with a balanced tuner vs an unbalanced (with balun) tuner. (5) I have plenty of room, would it make any difference if I put a 160 meter dipole instead? Thanks & 73, Greg, N6GK Have not seen any published tests comparing balanced vs. unbalanced tuners, so any comparisons will probably be theoretical in nature. Also, instread of the dx engineering balun, you might look at a w2du-style balun -- see his article at http://www.w2du.com/Reflection2.html bob k5qwg |
#4
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I guess if I never wanted to have any unbalanced antennas in the future, I'd go the balanced tuner and be done with it. But if the loss through the 238B and DXE Tuner Balun would not be substantially greater than the Balanced Tuner, but will permit me to match unbalanced lines too for future antennas, then that sure seems the way to go (and adjust the feed line length to best match). What do you all think? And thanks for you many replies that have brought me this far so far! My suggestions: Buy a used Johnson Matchbox for much less than the Palstar. Even the "low power" Johnson will take a KW. Or if you have the $, get the Palstar. Use it with a center-fed/ladder line dipole. Re the inverted L: you are making it much too hard! Just put up a 160/80 inverted-L and feed it directly with coax. There is no need for a tuner for this antenna (unless maybe you want to cover both CW and SSB on 80). A separate 80m element can just be paralleled to the 160 wire, like a "fan dipole". Put down lots of radials. To match the lower impedance on 160, just use a hairpin coil at the feedpoint. Tor N4OGW |
#5
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On Sun, 24 Jul 2005 17:54:58 -0700, "greg knapp 5"
wrote: I guess that is what MY REAL QUESTION boils down to...although I like the "single resonant" L-type Ten Tec 238 unbalanced tuner (and it would work great with my future inverted L), it needs a balun to match it to the open wire feed. Will the balun, at HIGH SWRs, just burn up my watts in heat and smoke? My MFJ 989C matches an 80 meter dipole with ladderline on all bands between 80 and 10. There is no smoke, no heat. With this antenna, I use the standard balun built into the tuner. Other times, I've used external chokes, either coiled coax or w2du type baluns. I'd recommend a standard unbalanced T-circuit type tuner, for as much money as you can afford. It'll do fine for a whole range of feeds, balanced or otherwise. bob k5qwg |
#6
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Interesting article. I also read W8JI's article on baluns that discusses
this type of balun too. Very interesting. Current balun definitely seems the ONLY way to go! "Bob Miller" wrote in message ... On Sun, 24 Jul 2005 11:32:37 -0700, "greg knapp 5" wrote: I have decided to erect an 80 meter dipole at 70 feet fed with 450 or 600 ohm open wire, for use on ALL HF bands between 80 and 10 meters. Power output will be 1000W CW and 1200W PEP. (1) Which is the better setup and why: a Ten Tec 238B unbalanced tuner with a DX Engineering 1:1 balun on antenna side of tuner OR a Palstar BT1500BAL balanced tuner? (2) Also, if I later decide to erect an inverted L for 160/80, can I use a balanced tuner with a DX Engineering 1:1 balun put on antenna side of tuner, but reversed in direction (converting unbalanced to balanced), or need I get a different tuner? (3) In a perfect world, I'd buy both tuners (one for balanced and one for unbalanced), but I can't afford it. Also, if I go with the unbalanced tuner, will the balun waste a ton of RF in heat and loss? (4) I made a similar post on the Ten Tec List, and received lots of advice on point designs, but not the COMPARISON data I was looking for that will help me make the final decision to go with a balanced tuner vs an unbalanced (with balun) tuner. (5) I have plenty of room, would it make any difference if I put a 160 meter dipole instead? Thanks & 73, Greg, N6GK Have not seen any published tests comparing balanced vs. unbalanced tuners, so any comparisons will probably be theoretical in nature. Also, instread of the dx engineering balun, you might look at a w2du-style balun -- see his article at http://www.w2du.com/Reflection2.html bob k5qwg |
#7
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On Sun, 24 Jul 2005 11:32:37 -0700, "greg knapp 5"
wrote: I have decided to erect an 80 meter dipole at 70 feet fed with 450 or 600 ohm open wire, for use on ALL HF bands between 80 and 10 meters. Power output will be 1000W CW and 1200W PEP. Is the radiation pattern on all of these bands acceptable/useful? (1) Which is the better setup and why: a Ten Tec 238B unbalanced tuner with a DX Engineering 1:1 balun on antenna side of tuner OR a Palstar BT1500BAL balanced tuner? Study this before deciding: http://eznec.com/misc/ibalun.txt Considering the capacitor in the Palstar isn't a balanced design, the capacitive coupling from it to ground is asymetrical, so I would not call it a balanced tuner. Also, I don't see anything that looks like a 1500 W balun in there. Ten Tec says, "Because there are only two variable components, there is only one setting of each which will provide a perfect match to a given load impedance. This unique setting automatically provides the lowest Q network possible. Low Q means low circulating currents, hence low loss, and it also provides the widest frequency bandwidth of operation before retuning is necessary (very useful if you're moving up and down the SSB portion of the band, for example)..." They are correct when they say that there is only one setting for a match, but the L-network Q is set by the load and source Z and is likewise fixed and totally out of the control of the operator. This may or may not give the largest operating BW and/or lowest loss. For example, take a load Z of 5 -j10 at 7 MHz. With capacitor Q =1000 and inductor Q = 250 (good luck with a roller inductor), an L-network of C = 1364 pF and L =0.568 uH will give SWR = 1.02. The network loss will be 0.1 dB. Using the same load Z and component Q, a high-pass-Tee network of Cin = 1438 pF, L = 0.36 uH and Cout = 3912 pF will give SWR = 1.01 The network loss will be 0.07 dB. More parts, lower loss. So much for conventional wisdom. Now this is a pretty wild load Z, but with certain antenna feedpoint Z and transmission line lengths and Zo, it's possible. Admittedly, the differences in insertion loss are negligble but they are different in the -wrong- direction, thus proving the point. Of course, try and find a tuner with capacitors of this high a value. Also, there are some impedances that cannot be matched with either configuration of a low-pass (series inductor) L-network. The same can be said for any other topology, but you should be aware of this. (2) Also, if I later decide to erect an inverted L for 160/80, can I use a balanced tuner with a DX Engineering 1:1 balun put on antenna side of tuner, but reversed in direction (converting unbalanced to balanced), or need I get a different tuner? I wouldn't do this. (3) In a perfect world, I'd buy both tuners (one for balanced and one for unbalanced), but I can't afford it. Also, if I go with the unbalanced tuner, will the balun waste a ton of RF in heat and loss? Maybe. In my opinion balun loss is no different from line attenuation. Line attenuation is magnified by SWR and I see no reason why balun loss wouldn't be too, particularly since most baluns are constructed from a transmission line. (4) I made a similar post on the Ten Tec List, and received lots of advice on point designs, but not the COMPARISON data I was looking for that will help me make the final decision to go with a balanced tuner vs an unbalanced (with balun) tuner. (5) I have plenty of room, would it make any difference if I put a 160 meter dipole instead? If you have plenty of room, why limit yourself to one compromise antenna? |
#8
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To answer your post:
Yes, I have looked carefully at the theoretical radiation pattern, and it is acceptable for now due to a number of constraints I am working against that do not permit something different. My goal is to have a strong signal from my QTH out to about 700 miles on 80/75 (for a net for which I am net control), and a decent signal on the rest of the HF bands. I am not so concerned about the peaks and valleys in the radiation patter on the higher HF bands as after 45 years of hamming, my #1 priority is no longer chasing DX pileups or contesting big time...I'd rather spend my time meeting new hams and getting to know them (they are really very interesting people!)...not just "599 CA" or "599 #683 about 600 times in two days. The gain peaks will give me plenty of people to talk with. I do not forsee having the ability to put up my beam and regular tower up again for various reasons (mainly too much hassel, time, and expense with my poor health), so basically all I have available is one 70 foot high mast (last 30 feet of which are Radio Shack 10 foot sections) in the back sheep pasture, that will have a low angle on the higher bands due to its height that might help make up for no multi-element gain. I do have two multi-band verticals, but the local noise is pretty bad...so hoping going horizontal and perhaps an ANC-1 will provide better receive. 73, Greg, N6GK "Wes Stewart" wrote in message ... On Sun, 24 Jul 2005 11:32:37 -0700, "greg knapp 5" wrote: I have decided to erect an 80 meter dipole at 70 feet fed with 450 or 600 ohm open wire, for use on ALL HF bands between 80 and 10 meters. Power output will be 1000W CW and 1200W PEP. Is the radiation pattern on all of these bands acceptable/useful? (1) Which is the better setup and why: a Ten Tec 238B unbalanced tuner with a DX Engineering 1:1 balun on antenna side of tuner OR a Palstar BT1500BAL balanced tuner? Study this before deciding: http://eznec.com/misc/ibalun.txt Considering the capacitor in the Palstar isn't a balanced design, the capacitive coupling from it to ground is asymetrical, so I would not call it a balanced tuner. Also, I don't see anything that looks like a 1500 W balun in there. Ten Tec says, "Because there are only two variable components, there is only one setting of each which will provide a perfect match to a given load impedance. This unique setting automatically provides the lowest Q network possible. Low Q means low circulating currents, hence low loss, and it also provides the widest frequency bandwidth of operation before retuning is necessary (very useful if you're moving up and down the SSB portion of the band, for example)..." They are correct when they say that there is only one setting for a match, but the L-network Q is set by the load and source Z and is likewise fixed and totally out of the control of the operator. This may or may not give the largest operating BW and/or lowest loss. For example, take a load Z of 5 -j10 at 7 MHz. With capacitor Q =1000 and inductor Q = 250 (good luck with a roller inductor), an L-network of C = 1364 pF and L =0.568 uH will give SWR = 1.02. The network loss will be 0.1 dB. Using the same load Z and component Q, a high-pass-Tee network of Cin = 1438 pF, L = 0.36 uH and Cout = 3912 pF will give SWR = 1.01 The network loss will be 0.07 dB. More parts, lower loss. So much for conventional wisdom. Now this is a pretty wild load Z, but with certain antenna feedpoint Z and transmission line lengths and Zo, it's possible. Admittedly, the differences in insertion loss are negligble but they are different in the -wrong- direction, thus proving the point. Of course, try and find a tuner with capacitors of this high a value. Also, there are some impedances that cannot be matched with either configuration of a low-pass (series inductor) L-network. The same can be said for any other topology, but you should be aware of this. (2) Also, if I later decide to erect an inverted L for 160/80, can I use a balanced tuner with a DX Engineering 1:1 balun put on antenna side of tuner, but reversed in direction (converting unbalanced to balanced), or need I get a different tuner? I wouldn't do this. (3) In a perfect world, I'd buy both tuners (one for balanced and one for unbalanced), but I can't afford it. Also, if I go with the unbalanced tuner, will the balun waste a ton of RF in heat and loss? Maybe. In my opinion balun loss is no different from line attenuation. Line attenuation is magnified by SWR and I see no reason why balun loss wouldn't be too, particularly since most baluns are constructed from a transmission line. (4) I made a similar post on the Ten Tec List, and received lots of advice on point designs, but not the COMPARISON data I was looking for that will help me make the final decision to go with a balanced tuner vs an unbalanced (with balun) tuner. (5) I have plenty of room, would it make any difference if I put a 160 meter dipole instead? If you have plenty of room, why limit yourself to one compromise antenna? |
#9
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Just a note:
With a link-coupled tuner you can use either a balanced line (ladder line, tv twin-lead) fed antenna or a coax fed antenna. It handles either equally well. Used Johnson Matchboxes are still fairly common on ebay in the $100 price range. I use mine for all bands 80-10. If you want to roll your own link coupled tuner see: http://www.amfone.net/ECSound/K1JJ13.htm |
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