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Author Topic: 20M dipole balun question, 1:1 or 4:1 or none?  (Read 3251 times)
WALTERB
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Posts: 550




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« on: June 27, 2011, 04:32:19 PM »

I'm planning on putting a 20m dipole up on a military fiberglass mast for field day and other portable uses. It will be up about 40 Feet.

Which Balun if any should I use?

thanks
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KE3WD
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Posts: 5688




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« Reply #1 on: June 27, 2011, 05:15:31 PM »

Dipole feedpoint impedance is going to be around 72 ohms or so, so I'd go with the 1:1, which would be a match to the 50 ohm radio well enough.


73
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K7KBN
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Posts: 3693




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« Reply #2 on: June 27, 2011, 05:35:19 PM »

Try it without any balun to start out - dipoles have been used for many decades with no balun or choke at the feedpoint and with no problems whatsoever.
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73
Pat K7KBN
CWO4 USNR Ret.
WB6BYU
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Posts: 18516




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« Reply #3 on: June 27, 2011, 07:35:27 PM »

Presuming it is a half wave dipole fed with coax, a 1 : 1 is a better choice than a 4 : 1.

With a folded dipole you'd want the 4 : 1 balun for coax feed.

For multi-band use, feed it with open wire line and put the balun at the tuner (probably a 1 : 1 in that
case, but a 4 : 1 may work about as well.)

Whether to use one or not is up to you - much of the time you won't notice any problems due to lack
of a balun.  But if you have problems with noise pickup on the feedline or RF in the shack, add a balun.
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WALTERB
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Posts: 550




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« Reply #4 on: June 28, 2011, 02:22:54 PM »

ok, thanks to all!
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