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Feeding a 3 element vetical array

Oct 27th 2015, 21:49

W3NRJ

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I know one should feed the 3 element vertical array with binomial current distribution per the Antenna Handbook guidelines. What if you don't? You would have some pattern in directions which could be to some advantage. Can anyone find the model of a 40 meter version fed with equal lengths of feed line and equal current? I've looked. Thanks !
Jim W3NRJ
Oct 28th 2015, 13:51

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
The demo version of EZNEC can model this--use a perfect ground and use six segments per vertical spaced 1/4 wavelength apart. You can then feed each vertical with a current source and specify whatever current you want in each vertical. With equal currents, you get end fire sidelobes 90 degrees from the main lobes at about -9 dB. Might be more useful to have zero current to the center vertical, then the pattern switches from broadside to end fire.

If you are looking for a simple antenna with a pattern that would fill in the nulls of a switchable broadside/endfire array, you may consider the N4GG array published in the July 2002 QST--the vertical wire at the center of a Bobtail curtain is replaced with a 1:1 balun and fed with 50 ohm coax.

Zack Lau W1VT
ARRL Senior Lab Engineer

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