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I need a 75 to 75 ohm balun antenna matching transformer.

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  1. 6th February 2010 05:45 PM #1
    gary350 gary350 is offline

    I need a 75 to 75 ohm balun antenna matching transformer.

    I can not find anything but 300 to 75 ohm balun antenna matching transformers at Radio Shack or any other place in town.

    I found instruction how to make a 1 to 1 balun but there are no details on the, number of turns, wire size, or ferrite donut.??????????

    I have several ferrite donuts, small, medium and large. Picture in Amateur Radio Handbook looks like 8 turns of enamel coated copper wire but picture online shows about 20 turns of insulated house wire. I need LOW LOSS for a 16 element collinear array TV antenna for my HDTV.

    I could buy a balun if I could find one at a reasonable price. I don't think $15 plus $10 postage is a good deal.

    My antenna is a 16 element collinear array 75 ohms with a 75 ohm coax cable to the HDTV. Frequency range is 180 to 692 MHz.
    Last edited by gary350; 6th February 2010 at 05:49 PM.
  2. 6th February 2010 07:28 PM #2
    crutschow crutschow is offline
    75-75 ohm baluns are not common since you seldom find a balanced 75 ohm source. What do you need this balun for? Most antennas are 300 ohms balanced.
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    Zapper
    Curmudgeon Elektroniker

    --Inside every little problem is a big problem trying to get out.--
  3. 6th February 2010 08:28 PM #3
    MikeMl MikeMl is offline
    If you are connecting a 75Ω spigot on the antenna, to 75Ω coax, why do you need a balun? Do you want DC isolation; i.e. a two-winding transformer?
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    Mike ML.
  4. 6th February 2010 09:27 PM Thread Starter #4
    gary350 gary350 is offline
    Balun stops some unwanted stuff, static, ghost. etc. I have a 16 element collinear array antenna it is 75 ohms. I am using 75 ohm coax to my HDTV. It is working fine without a balun I just want to try it with a balun to see if it makes it any better.
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  5. 6th February 2010 09:30 PM #5
    kchriste kchriste is offline
    Try 2 back to back 300-75Ω baluns first. They used to be pretty common. Maybe some of your buddies have some laying around.
    You could also try a coaxial balun, but they are relatively narrow bandwidth so it would be to trial on one or two channels only.
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    Last edited by kchriste; 6th February 2010 at 09:41 PM.
  6. 7th February 2010 12:46 AM #6
    crutschow crutschow is offline
    Quote Originally Posted by gary350 View Post
    Balun stops some unwanted stuff, static, ghost. etc. I have a 16 element collinear array antenna it is 75 ohms. I am using 75 ohm coax to my HDTV. It is working fine without a balun I just want to try it with a balun to see if it makes it any better.
    Since HD is digital, if it's working fine then you can't do any better. You said a balun stops static, ghost, etc. (which I don't see how. All it will likely do is reduce the signal amplitude) but you apparently don't have any of that. Seems like a waste of effort.
    0
    Zapper
    Curmudgeon Elektroniker

    --Inside every little problem is a big problem trying to get out.--
  7. 7th February 2010 01:09 AM Thread Starter #7
    gary350 gary350 is offline
    You are right it will reduce the signal a little. I read ferrite type baluns are only 90% efficient. I have a 300 to 75 ohm balun that I tried I can't tell it make any difference signal seems to be the same.

    I made some changes again to my antenna today. I re scanned and now I can receive 8 more stations. One station is channel 7 Knoxville TN that is 120 miles away. That totally freaks me out I can pick up Knoxville it has been coming in pretty good 70% strength all evening. I watched a 2 hour movie on channel 7.2.
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  8. 7th February 2010 01:23 AM #8
    Space Varmint Space Varmint is offline
    Quote Originally Posted by gary350 View Post
    I can not find anything but 300 to 75 ohm balun antenna matching transformers at Radio Shack or any other place in town.

    I found instruction how to make a 1 to 1 balun but there are no details on the, number of turns, wire size, or ferrite donut.??????????

    I have several ferrite donuts, small, medium and large. Picture in Amateur Radio Handbook looks like 8 turns of enamel coated copper wire but picture online shows about 20 turns of insulated house wire. I need LOW LOSS for a 16 element collinear array TV antenna for my HDTV.

    I could buy a balun if I could find one at a reasonable price. I don't think $15 plus $10 postage is a good deal.

    My antenna is a 16 element collinear array 75 ohms with a 75 ohm coax cable to the HDTV. Frequency range is 180 to 692 MHz.

    Oh, this is a receiving antenna. Well then the enameled wire is fine. You can use the smallest ferrite core you have also.
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  9. 7th February 2010 01:48 AM #9
    unclejed613 unclejed613 is offline
    try 3-5 turns of twisted pair on the smallest ferrite donut you have. one wire is the primary, the other wire is the secondary. since it's twisted pair, and it's on a ferrite donut the coupling coefficient is very close to 1.
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  10. 7th February 2010 06:07 AM #10
    Space Varmint Space Varmint is offline
    Quote Originally Posted by unclejed613 View Post
    try 3-5 turns of twisted pair on the smallest ferrite donut you have. one wire is the primary, the other wire is the secondary. since it's twisted pair, and it's on a ferrite donut the coupling coefficient is very close to 1.
    I like your slogan UncleJed. Also don't you have to put the smoke back in to fix it? I know I've had allot of capacitors that went bad when the smoke leaked out
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