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NMO 2 / 440 on plastic roof. Ground plane ??

Apr 8th 2021, 15:26


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I plan to mount a 2 / 440 FM radio in a backhoe that I just bought.

A plastic roof sits on top of a steel ROPS cage that forms the sides and top of the cab.

If I mount a 5/8 wave antenna on top, it's going to need a ground plane.

1. Is the ROPS cage enough of a ground plane for the antenna if the 3 inch square steel bars makes a rectangle about 2 x 3 feet with the antenna on the plastic in the middle?

2. How close does the ground plane have to be? Could I mount the NMO on an L shaped bracket, and assume that the backhoe arm and frame of the tractor, four feet below, is enough ground plane?

Or should I get a deep NMO, mount it in the center of the plastic roof, and put some sort of a hardware cloth mesh screen under the plastic roof?

Finally, do I need hardware cloth, or can I use 4, 19 inch pieces of wire to act as ground radials like with a 5/8 base antenna?

Jun 29th 2021, 13:26


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Hummm, my ROPS has a nice aluminum roof; no problems. :-)

However, either the hardware cloth or the 4 pieces of wire will work; been doing that for plastic roof cars. Also used thin aluminum sheet glued in place (works really well).

If you connected the "ground" side of the antenna base to the steel bar frame well enough, that would do it as well. Copper braid soldered point to point, maybe to more than one frame member.

Good Luck!

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