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

G

gary350

Well-Known Member
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.
 
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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.
 
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?
 
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.
 
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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gary350 said:
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.
Click to expand...
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.
 
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.
 


Oh, this is a receiving antenna. Well then the enameled wire is fine. You can use the smallest ferrite core you have also.
 
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.
 
unclejed613 said:
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.
Click to expand...

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
 
i keep a can of smoke handy at all times......

part number OICU812
i keep it next to my left-handed monkey wrench and my box of compass bearings.

back to the question at hand.... if it ain't broke, don't fix it. use a balun if you have some reason to provide DC isolation, but otherwise, it's not worth it to add a device that will introduce loss into the system.
 
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