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Suitable ground plane?


IronArcher
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So, I want to rig up a temporary base antenna from one of my mobile antennas.

I have an odd roof over a small front porch.

This roof has concave sides that terminate to a flat beam at the peak.

I have a few sections of drilled steel.

I am planning on mounting an 18-24” diameter section of this drilled steel (maybe 1/16” at best thickness).

I would use an NMO mount attached to the ground plane, then screw the GP to that flat beam at the peak on the roof.

What would be the smallest I could make the ground plane (7” radius?) and does the fact that it is drilled factor into the dimensions needed?

Again, this is a temporary setup, getting too cold to put up my tripod now.

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Good Morning IronArcher.

 

Yes, ground plane radials for a 1/4 wave GRMS antenna need to be around 7”. Larger radials are perfectly acceptable. When using the simple 1/4 GP design, bending the radials downward will improve SWR too as it helps to raise the impedance of the antenna closer to the desired 50 ohms and has the positive effect also of lowering the peak radiation angle of the antenna down closer to the horizon instead of upward angle towards the sky.

 

Here is a link you can refer to:

https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/

 

Good luck on your project.

 

Michael

WRHS965

KE8PLM

 

 

Sent from my iPad using Tapatalk

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As long as the ground plane material is electrically conductive, properly sized, and the antenna mount is properly grounded to the ground plane, drilled or not won’t matter. We’ve made highly effective ground planes out of steel, aluminum, and copper screening, foil tape, chicken wire (and other fence materials), and more.

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Thanks for the link!

Note that this ground plane I’m making is going to be more of a disk made of drilled steel.

I’m not sure if that makes a difference or not.

Makes no difference. The earth is a big ball and makes an excellent ground plane for many antenna. :). If you were using rods for the radials you would need at least three, but more would work even better.

 

I once used a metal trash can lid. It worked just fine.

 

Michael

WRHS965

KE8PLM

 

 

Sent from my iPad using Tapatalk

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