Nmo ground question

[dave3825]

I have a magnetic nmo mount. I know when you install an nmo thru a hole in the roof, the roof acts as a ground plane. With the magnet, there is not a definite ground.

If I ran a wire with an aligator clip from the body ground under the dashboard, to the outer part of the connector, where it meets the scanner, would that use the roof as a ground plane the same way as if it was mounted thru a hole in the center of the roof?


Thanks

 

[mmckenna]

RF grounds and DC grounds are different.
The tiny bit of space between the base of the magnet and the vehicle body is nearly invisible to RF. This "capacitive coupling" provides a pretty good (not perfect) ground connection for your mag mount.

Adding a ground wire won't hurt, but it's not really going to benefit as a ground plane under the antenna. The important part about the antennas ground plane is that it's directly under the antenna. Relying on the ground coming up through several feet of cable isn't going to help.

Where you can get a benefit is grounding the body of the radio (use one of the mounting screws) directly to the vehicle body. This can help reduce noise/interference as it gives stray energy a quick path to ground without relying on a long wire to get there. Long ground wires can sometimes act more like antennas than ground.

As for antenna ground planes, direct connection is going to be best, but I understand that some just don't want to drill holes.

 

[marksmith]

You can always drill the hole and find out for yourself, but I think you would find very little impact.

The is more impact associated with where you stick that magnetic mount and the ground plane that establishes than any ground wire would create.

Simply sticking a magnet mount antenna to a big pizza pan can drat icalls enhance the antenna.

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