antenna question

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n6kkk
Posts: 5
Joined: Fri May 16, 2003 9:04 pm

antenna question

Post by n6kkk »

QUESTION : which will get out better figuring all things are the same .
1) rotatable dipole
2) windom
k4kk
Posts: 207
Joined: Tue Dec 30, 2003 12:20 am
Location: The great state of Tennessee

Post by k4kk »

"Getting out" is not the issue. Both can and will perform well.

The Windom was originally a single wire fed antenna and had a lot of issues with radiation (TVI and RFI) and ground currents at the shack. It has been redesigned and is often seen as an OCF (off center fed) antenna with coax or twin-lead connections.

A dipole is essentially a 1/4 wave on each side balanced antenna. It will work well at odd /4 wave lengths. Hence, a 40 meter dipole works well on 15 meters and the 80 meter dipole works well on 10 meters.

The OCF antenna will require a 4:1 current balun to work properly (some even a 6:1 or 9:1). It will be resonant at various points in the amateur bands and is very sharply resonant. That means that the curve is steep and resonance is limited. It can be overcome with a tuner but that's another expense.

The dipole can be fed with either a 1:1 balun or simply fed with a center insulator (even a piece of plexiglass). It will offer a much wider bandwidth ON THE BANDS where it is designed to work (those at odd /4 wavelengths). On other bands, it will require a tuner. A coaxial feed line can be used to feed multiple dipoles at a single feed point (fan dipole) to achieve single antenna resonance on all bands.

You need to determine what your goals and needs are and make a good decision based on those. "Getting out" with a good antenna is not an issue.
ku3x
Posts: 37
Joined: Sat Mar 24, 2012 5:43 pm

OCF / parallel feeders

Post by ku3x »

Never feed an Off Center Fed Antenna with parallel feeders. An OCF is not
a balanced antenna and the parallel feeders WILL RADIATE and this you don't want.
You would be better off using a simple dipole cut for the lowest operating frequency and feeding it with parallel feeders if that is the transmission line you choose to run to the antenna.

Barry, KU3X
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