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Old November 4th 09, 01:45 AM posted to alt.internet.wireless,rec.radio.amateur.antenna
amdx amdx is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 349
Default Matching impedance with coax

Hi all,
I'm trying to get an understanding of the MFJ-1800 wifi antenna.
The antenna has a folded loop as the active element.
Is this considered to have a 300 ohm output impedance?
The folded loop is connected to 2.11 inches of 50 ohm coax
that goes to an N connector. The coax has 4 torroids on it.
It looks like a polyethylene core material. So I used .66 as a VF.
With that I get a .66 wavelength of at 2.437 Ghz for the 2.11" coax.
(yes same .66, that's just the way it worked out)
So I think I'm matching 300 ohms to 50 ohms, but I don't
see how .66 wavelength of 50 ohm coax does that.
Fill in the details please.
Here's a picture of the MFJ.
http://www.gigaparts.com/parts/gpcpa...nal/nw0054.jpg

Thanks, Mike