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Author Topic: Horizontal Loop and Vertical Coupling  (Read 1101 times)
N8EUI
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Posts: 199




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« on: June 27, 2011, 06:11:45 AM »

Hey there everyone,
I'm erecting a horizontal loop.  One leg of the loop will run about seven feet past my HF9V vertical.  Will there be any coupling of the antennas?

Thank you,
N8EUI
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W8JI
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« Reply #1 on: June 27, 2011, 06:45:37 AM »

Hey there everyone,
I'm erecting a horizontal loop.  One leg of the loop will run about seven feet past my HF9V vertical.  Will there be any coupling of the antennas?

Thank you,
N8EUI

Yes.


The only question is how much, but most likely it will be significant.
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WA3SKN
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« Reply #2 on: June 27, 2011, 12:01:01 PM »

Just try it!  If the is too much, you can just move the wire away.
73s.

-Mike.
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N4JTE
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« Reply #3 on: June 27, 2011, 01:45:00 PM »

I would expect minor effect unless the feedline for the loop is close to, or parallel to, the vertical.
Bob
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W8JI
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« Reply #4 on: June 28, 2011, 04:19:06 AM »

I would expect minor effect unless the feedline for the loop is close to, or parallel to, the vertical.
Bob

Hi Bob,

Fashion a loop out of a paper clip, and have it pass very near a vertical pin, and move it around close to the loop perimeter.

You will see when you look at it in three dimensions the horizontal loop viewed from various angles the loop nearly parallels the vertical pin. This is why, off the ends of a horizontal antenna, radiation has considerable tilt towards vertical. 

When that wire passes by the vertical there can be considerable coupling, unless the vertical is in the center (axis) of the loop or the loop is a fairly large distance away.

This isn't saying he will have a problem, only that there can be a very high level of coupling depending on the exact positioning.

73 Tom
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N8EUI
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« Reply #5 on: June 28, 2011, 06:15:00 AM »

Thank you for your replies.  My vertical is ground mounted halfway between one leg of the square horizontal loop.  I did read a while back that experiments were done that concluded coupling is more severe when a vertical is located near the ends of a loop or dipole.  Am I correct in that assessment?  I guess I'll try my original plan and see what happens.  What's the worse that could happen?  If it doesn't work out, I'll try a different configuration.

Thanks again,
Tom, N8EUI
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W8JI
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« Reply #6 on: June 28, 2011, 02:43:08 PM »

Thank you for your replies.  My vertical is ground mounted halfway between one leg of the square horizontal loop.  I did read a while back that experiments were done that concluded coupling is more severe when a vertical is located near the ends of a loop or dipole.  Am I correct in that assessment?  I guess I'll try my original plan and see what happens.  What's the worse that could happen?  If it doesn't work out, I'll try a different configuration.

Thanks again,
Tom, N8EUI

Hi Tom,

You really will just have to try it.

A dipole has significant vertical tilt to the polarization as we move around to the ends. For minimal coupling from a vertical to a horizontal dipole, the vertical needs to be broadside to and centered on the dipole. That's a given for multiple reasons.

A horizontal loop is more complex. It has four cross-coupling null points near the loop for radiation and magnetic coupling. They are centered on the voltage peaks and in the middle of current maximums for most common shapes.

My only point is they absolutely have coupling when close, even when cross polarized, unless you hit sweet spots. :-) This is all academic if you don't have a problem you notice. Where it might be a worry is if you have both antennas connected to  radios at the same time.

73 Tom
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