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Antenna Placement

Feb 8th 2018, 18:12

KB0PDK

Joined: May 14th 2012, 20:53
Total Topics: 0
Total Posts: 0
Can anyone give me a definitive answer to placement of ones antenna. As I read NEC and books it seems that all antennas are place over bare earth. For us that live in confined quarters and need to place our antennas on the roof of our dwellings can any one tell me if NEC programs regarding height is equal on a meter to meter basis if place over bare ground or a roof.

Thanks for the help;
Feb 9th 2018, 15:42

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
NEC can model different ground characteristics, if you know the dielectric constant and conductivity of the material the antenna is placed over. The advanced amateur may be able devise clever ways of measuring these parameters.

In practice, the ideal place to put a vertical antenna is as close to the ocean as possible. Similarly, I've had great results siting dipoles over steeply sloping ground, to tilt the angle of radiation in the desired direction.
A metal roof is typically a desired place to put a a vertical. But, concrete is a lossy dielectric that may contribute to poor antenna performance if it is necessary to locate an antenna close to a building.

While the three dimensional finite element simulators that are needed to model complex grounds are beyond the means of most hams, modeling highly simple models with NEC may provide sufficient guidance to choosing the best option. And there is always cut and try optimization using web services like the Reverse Beacon Network to see what produces the strongest signals at remote stations around the world.

Zak W1VT

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