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Author Topic: Building a dipole from 75 ohn coax.  (Read 477 times)
N2TMC
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Posts: 15




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« on: October 31, 2004, 06:13:05 PM »

I have tons of 75 ohm coax. I would like to build a dipole from it fed with the coax back to my tuner. I hate to have this stuff here and not use it.
Any thoughts?

Thanks
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AA4PB
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Posts: 12892




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« Reply #1 on: October 31, 2004, 06:41:00 PM »

You shouldn't have any problem using the 75 ohm coax to feed a dipole. A dipole in free space is 75 ohms. As it gets closer to ground, the feed impedance drops. In practice the feed impedance will probably be somewhere between 50 ohms and 75 ohms so the SWR may not be any worse with 75 ohm coax than with 50 ohm coax. The tuner will match it to the radio's 50 ohm output just fine.

If you also want to use the 75 ohm coax for the dipole element, that should work too. I'd just tie the center conductor and the shield together at each end and treat it as a single wire. The only issue may be supporting the weight as coax is pretty heavy.
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KB7YOU
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Posts: 42


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« Reply #2 on: December 07, 2004, 02:15:58 AM »

Hi George,

You can acutally build an end fed dipole for any band out of nothing but the 75 ohm coax. I've done this several times and it works OK. Do a web search for end fed coax dipole to see some plans. Here is one link I found that has a few good diagrams: http://www.xs4all.nl/~pa0nhc/antenne/cobra80/cobra.htm

Good Luck
73
Chris
KB7YOU
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N8BOA
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Posts: 91




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« Reply #3 on: January 19, 2005, 06:29:09 PM »

I have seen wide band bazookas built from coax should be able to find something on the net or in the arrl
Sean
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