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Author Topic: Inverted L antenna  (Read 780 times)
KB3ILN
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Posts: 33




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« on: December 31, 2007, 11:43:17 PM »

At the present for 40 meters I am using 32 feet of wire taper to fiberglass pole and connected to 15 radials on the ground. I would like to connect a 30+ piece of wire to the top of the antenna I now have and run it to a tree near by. Right now I connect to this wire antenna with coax and run it into my shack. Would adding this extra wire cause me any problems with increased feedpoint impedances. Would I or should I add a balun to the set up? My SWR's are fine now without a tuner.  With a tuner would this work from 10 thru 80 ?

Thanks,
Ed
KB3ILN
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KB5IAV
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« Reply #1 on: January 01, 2008, 06:05:05 PM »

Have you considered one of the autocouplers out there, like the ones by SGC?  That might work a little better than a tuner in the shack, since the antenna is fed with coax.

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WA7NCL
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« Reply #2 on: January 03, 2008, 08:06:44 AM »

Yes, without an impedance matching network at the bottom, the feedpoint impedance will rise and be a poor match to coax.

The previous poster made a good suggestion of using an auto tuner if you want to run a longer wire.

There are certain advantages to lengthening the wire up to a little over a half wave.  At a half wave the wire will be high impedance and you might increase your efficiency due to decrease in ground currents flowing in the radial system.  You will still have losses in the surrounding ground out 1/2 wavelength and beyond.  There is little you can do about that short of massive amounts of radials.

I use the half wave vertical wire system with an LC network at the base of the antenna wire and a very short set of radial wires.  The LC network matches the coax to the high impedance of the halfwave wire.

A commercial antenna that uses this idea of end feeding a half wave is the PAR electronics End-Fedz antenna.  You can look them up on the net.
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NG0K
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Posts: 335




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« Reply #3 on: February 13, 2008, 08:12:25 AM »

If you make an inverted-L from it then the low radiation pattern on 40m goes bye bye and your ability to work DX becomes a little tougher.  

I use an aluminum vertical on 40m.  Then built a 40m coaxial trap and mounted it on the top.  Then I ran wire for 80m.  Like two antennas in one.

You could also run a 65+- foot wire independently and feed with with the same coax.  

73, Doug.
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73, Doug - NG0K
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