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Author Topic: Balun design further  (Read 280 times)
KA7QOR
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« on: May 03, 2004, 12:27:29 AM »

Thanks for the responses! All of my internet searching has lead me to the last option of buying one of these reference books. Im not willing to make that investment yet. I have been studying a ARRL handbook and I was wondering if 2 baluns together would be efficent, Im happy to learn that this is an option.
Ok, Ive been playing with EZNEC 3.0 demo version and have learned more about antennas in a week than in my 25 years as a ham. Based on my needs, I designed an efficent hf antenna, modeled it first for UHF and then tried 6m. What I have got is two 3/4 wavelength wires center fed in the horizontal plane and bent from the center along the azimuth (horizion). This gives me 10-16dBi for about 200 degrees in the azimuth and 10 degrees elevation. It is very easy to tune with an antenna tuner. At the moment I have a Diamond 1:1 500W balun on the dualband 20/10m version and I use RG142. I have a homebrew ferrite core 1:1 balun on the 6m version and using RG8X. But I would like to find a way to feed these antennas without using an antenna tuner? Also Id like to know the winding details for a hf 1:2 unun on a 1.25 inch ferrite core with about 16AWG magnet wire?
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K0BG
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« Reply #1 on: May 03, 2004, 09:34:34 AM »

Well, the answer is the same as before. Here are two references for you.

First, go to http://www.w8ji.com and read about baluns in general. Tom designed the baluns which DX Engineering sells, and his expertise is unquestionable.

Secondly, log on to http://www.arrl.org and look for the booklet "Building and Using Baluns and Ununs" by Dr. Jerry Sevick. It's $24 if my memory serves correctly. It is a wealth of information, and contains a lot of "how to" material.

There are somethings in life you just have to belly-up and pay for. This is one of them.

Alan, KØBG
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K0IZ
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« Reply #2 on: May 03, 2004, 11:44:29 AM »

If I understand your 3/4 wavelength antenna:  this is in effect a V antenna (installed horizontally) with two 3/4 legs and some angle between.

I currently have a four-leg V antenna with traps, such that on 80 meters each leg is 3/4 wavelength (I use two legs at any one time).  My measured impedance is about 100 ohms for those leg lengths.  So a 1:2 or 1:2.25 balun would work well.  I use the 1:2.25 balun I described in my other note to you.  (this antenna and balun will be in QST, perhaps Sept issue).

Re efficiency of transmission line transformers (for HF), if wound per Jerry's book, you should have 99+% efficiency, assuming you are coupling to a reasonably resonant antenna.  If lots of reactance, should work OK but more iffy.
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AD6JN
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« Reply #3 on: May 07, 2004, 05:42:52 PM »

For 16 Ga the 2.40 inch diameter (size 240) toroid will be easier to wind.  Try mix 67 but mix 61 will work fine on 6 meters.  The Dr. Sevick book will describe how to wind the correct ratio.  Wind the balun using 5 turns, 10 turns and then a maximum number of turns.  Using the MFJ-259 analyzer with the balun terminated with load resistor plot VSWR versus frequency.  Compare the results and use the one that has the flattest curve.

Good luck.  73
Bob AD6JN  
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