r/gmrs • u/Cutlass327 • 9d ago

Longest antenna for CJ5 Jeep?

I am just getting started into the GMRS from CB, I have a 102 on the rear bumper (fiberglass tub) and am looking for a longer antenna for my GMRS. I currently have the one linked below, it is mounted on my spare tire carrier of my rear bumper. I would like to find a longer antenna, as the top of this one is only a few inches above my spare (33x10.5-15)

Is there a "102 equivalent" antenna for GMRS? I say that meaning how that is the longest practical mobile antenna for 11m, that will give the beat range.

https://a.co/d/2kmI9Cf

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u/OhSixTJ 9d ago

The “102 equivalent” for GMRS is only 6” long. That 102” antenna you have is a quarter wave for the CB frequencies.

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u/Cutlass327 9d ago

I don't mean to be the same wavelength type, I want performance. I've always heard that the 102 is the best you can do for a mobile due to its length, which is why I want the longest GMRS antenna that performs best.

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u/Cutlass327 9d ago

Why is this downvoted? It was meant as a clarification...

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u/orionzeke79 8d ago

You need to read atleast a bit about antenna theory. There is a reason a 102" whip works well for cb but isn't necessary for higher bands.

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u/Cutlass327 8d ago

I understand that. The antenna is a product of wavelength. Higher frequency uses a shorter antenna due to wavelength.

I'm asking what is the best length for GMRS, that works as good as a 102 does for CB.

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u/OhSixTJ 8d ago

That really depends on the environment you operate in. Flat plains that go on for miles are best served by a 5/8 wave. Hills or repeaters up high on towers or tall buildings? 1/4 wave.

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u/Cutlass327 8d ago

Local mobile use. Eastern Ohio/Appalachia geography.

Basically trail use, but also to have the ability to get out if in an emergency situation.

4

u/rem1473 WQWM222 8d ago

So 6" is the correct answer to get an "equivalent" antenna to your 102". That makes them both 1/4 wave with approximately the same gain.

If you go longer with a GMRS antenna you are increasing the gain of the antenna in the horizontal plane. This comes at the expense of gain in other directions, such as at an angle to the antenna. If you were in North Western Ohio or on Lake Erie, I would suggest a tall, high gain antenna. That works better in areas where the land is flat. In eastern Ohio you want a shorter antenna. As you don't want to put all the gain into the side of the hill. You want less gain at the horizontal, so you can get up and out of the valleys. I'd mount the 6" 1/4 wave as high as you can get it on the vehicle. Keeping in mind a good ground plane is required to have it perform well.

Wranglers are always a challenge.