6:1 balun - HomeBrew Forum at eHam.net

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eHam.net Forum : HomeBrew : 6:1 balun

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6:1 balun	Reply
by CT1FKC on December 29, 2002	Mail this to a friend!
does anyone have plans for winding a 6:1 balun with toroids- a T200-2 or similar. I am planing to use one with a Windom antenna for 10 to 40 m.

RE: 6:1 balun	Reply
by WB6BYU on January 2, 2003	Mail this to a friend!
A 4 : 1 balun is much easier to wind and will probably work as well. Otherwise you will need about a 5 : 2 turns ratio on the balun, with a center tap on the high impedance side. You could try 10 turns for the secondary and 4 turns for the primary connected to the coax in a conventional transformer connection (separate windings) or an autotransformer: connect the shield of the coax to the center tap of the secondary (say, 5 turns into a 10 turn winding) and tap the center conductor 1 turn in from the end. (You can then experiment with the tap for the center conductor to find the best match.) Either of these methods may require more than 10 turns on the secondary, depending on the permability of the ferrite core you use, but the turns ratio will remain the same. And I suggest that you plan to adjust the number of turns for best SWR once you get the antenna installed - the input impedance of a Windom is not as constant across the spectrum as some descriptions might imply.

RE: 6:1 balun	Reply
by CT1FKC on January 3, 2003	Mail this to a friend!
the only thing I have tried was to build a conventional 4:1 balun and then moving the coax center conductor along the first inductor to achieve 1:1 SWR. with my antenna analyzer worked fine.I received the idea at this forum I presume, and then I have found the same idea at another web page, wich I'll send you just for curiosity. but since I don't have much space I presume you are correct about having to tune the antenna. 73 and thank's for the reply.

RE: 6:1 balun	Reply
by WB6BYU on January 3, 2003	Mail this to a friend!
I just re-read the original and notice you are considering using a T-200-2 core. This particular core may not have enough permability for the balun to work properly. The -2 material is powdered iron, not ferrite. The iron can handle much more power before saturating, but will need many more turns to have the same inductance. With the increased turns count on the core, there may be more problems with capacitance between the turns. A ferrite core with a permability around 125 to 250 may be a better choice. The required inductance in the secondary would need to have a reactance at least 5 times the load impedance on the lowest band. If the antenna is 300 ohms, this means 1500 ohms on 40m, or roughly 40uH (if I calculated it correctly in my head.) Calculate the number of turns on the core required to get this inductance, and calculate the primary turns at 40% of that.

RE: 6:1 balun	Reply
by CT1FKC on January 3, 2003	Mail this to a friend!
it really seems you have calculated it right. I have seen one or two baluns factory made and I have noticed they use ferrite and not iron cores, as you said before. instead of having a matching circuit I may have a ressonant one.I'll order a ferrite core to test and I'll see what my dip meter tell's me. at this moment I am waiting for good weather, so a few more weeks and I'll take my conclusions on the roof.I'll also try to find some literature about this. most I have is about homebuilding, like " Solid State Design". maybe I find the Perfect Antenna until then.

RE: 6:1 balun	Reply
by ZL2TVL on September 22, 2003	Mail this to a friend!
http://members.fortunecity.com/xe1bef/balun.htm shows a 6:1 balun using 2 ferrite rods, 12 turns tapped at 10th turn for 6:1 perfect for the Windom, regards ZL2TVL

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