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Author Topic: Highest Gain Mid-VHF Omni Design?  (Read 1192 times)
KC2NLT
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Posts: 92




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« Reply #15 on: November 05, 2017, 12:59:07 PM »

I’ll try both a dipole and a ground plane.

Is the ground plane going to be 1/4 wave while the dipole is half wave or will I get better coverage with a quarter wave dipole and a quarter wave ground plane?
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G8HQP
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Posts: 595




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« Reply #16 on: November 06, 2017, 04:55:58 AM »

Halfwave dipole and quarter-wave ground plane are alternatives. You seem to talk as though they form a combined option.
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K1ZJH
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Posts: 3308




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« Reply #17 on: November 06, 2017, 06:51:32 AM »

The problem with many simple ground planes or j-Poles is that they don't decouple the feed line properly
and that skews the pattern.

One of the best moderately priced antennas I've ever used that works is the old AEA Isopole design
with the dual cones for isolating the feed line.

Someone is making them again, but they aren't cheap.

Pete
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KC2NLT
Member

Posts: 92




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« Reply #18 on: November 06, 2017, 03:49:56 PM »

Halfwave dipole and quarter-wave ground plane are alternatives. You seem to talk as though they form a combined option.

Just thought of experimenting with the two types. I think the quarter wave might give me better coverage. That's where my question was coming from.


The problem with many simple ground planes or j-Poles is that they don't decouple the feed line properly
and that skews the pattern.

One of the best moderately priced antennas I've ever used that works is the old AEA Isopole design
with the dual cones for isolating the feed line.

Someone is making them again, but they aren't cheap.

Pete

Thanks. I'll look into them.
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KC2NLT
Member

Posts: 92




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« Reply #19 on: November 09, 2017, 11:38:56 PM »

I think I found what I was looking for, although the requirement for an infinite ground plane makes this antenna a fixed one.

https://www.mathworks.com/help/antenna/examples/modeling-infinite-ground-plane-in-antennas-and-arrays.html

It seems the gain can be pretty high compared to a dipole.

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G8HQP
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Posts: 595




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« Reply #20 on: November 10, 2017, 03:22:56 AM »

An antenna radiating into half-space may give the false impression of having extra gain.
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