Mobile antenna types and mounting location

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Mobile antenna types and mounting location


Post by sdnative » Sat Feb 07, 2009 6:31 pm

I have been doing some research on antenna theory, type, and mobile applications. My intention was to drill my roof for a couple of NMO mounts, but I have been trying to decide on the optimum location.

My primary antenna will be the 2m, so it gets the best seat in the house, sort of speak. I wanted to use a quarter wave ground plane type for this one. At 2m, I would need roughly a 40" diameter circle. This would be in the center of my roof, with the sunroof making a tangent to the front on the circle.

Right behind that will be another one used for (cough, cough) a CB. Now I don't have the full ground plane necessary for the 11m CB, but I was reading that a 36"' diameter circle would be sufficient. So I will make this one roughly 20" up from the back edge of the roof.

I have a 60" x 45" piece of metal to play with, so if I put both in line down the center of the roof, they would be spaced 20" apart.

Another option is to use a half wave whip for 2m, which doesn't need a ground plane. I could then mount this in the back and put the CB up front, giving the CB a larger ground plane.

What option would give better performance? Is a quarter wave ground plane equivalent to a half wave whip?

what about 5/8 wave. I believe this would need a ground plane, and has better radiation horizontally as well. (and the 1/2 wave has better than the 1/4 wave).

There are also differences with impedance between a 1/4 and 1/2 wave.

Any thoughts or comments on this before I start drilling? :mrgreen:

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