loop antenna impedance match

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newman555

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I have built a loop antenna and at 100Mhz(this is where I want to use it) it has an impedance (real part) of only 0.2ohms and since the cable is 50ohms I have to do some impedance matching. I wanted to do it with Pi or L networks but I can't find inductor small enough, so is there any idea how to do this? I would be very grateful for any help. Thanks...
 

zz0468

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newman555 said:
I have built a loop antenna and at 100Mhz(this is where I want to use it) it has an impedance (real part) of only 0.2ohms and since the cable is 50ohms I have to do some impedance matching. I wanted to do it with Pi or L networks but I can't find inductor small enough, so is there any idea how to do this? I would be very grateful for any help. Thanks...
Only .2 ohms!? It sounds like you measured the DC resistance of the loop. What is the actual impedence at 100 MHz?
 

kb2vxa

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There are a lot of loops out there, usually series gamma matched so it would help if you better describe it preferably with a drawing as an attached image file. I don't know why you would want 50 ohms impedance on the FM broadcast band when the input to such a receiver is dual 75 ohms unbalanced and 300 ohms balanced.

Then considering what you're putting yourself through I don't know why you don't just buy an FM antenna and be done with it.
 

newman555

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this is a part of paper i have to write for my university. I have built circular loop with only one turn (it has to be like this), so I can't change anything. Impedance is approximated using formula, but I'm sure it's very low, and it much smaller than 1 wavelength (diameter=0.2m). So is there a way to solve this problem?
 

newman555

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I also used capacitor to tune it to resonate at 100Mhz. So is there a way to match impedance to 50 or 75ohms (it doesn't matter to me which, I intend only to use it to measure field pattern and stuff like that )? Transformer, PI or L networks? Help me out here, I really don't know what works with this problem...Thanks again
 
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