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Another antenna mounting option for GMRS/Amateur, etc.

Radio Guy

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I already had three antenna mounts on my Mojave, two NMO trunk lip mounts on the front hood and a custom mount in the bed that will take everything from a 3" 900MHz NMO whip to a heavy 160-10M HF screwdriver. But I wanted more and have been looking at the upper bed rail below the rear window for some time. Since the entire upper part of the JT is mostly non metallic, it should provide a reasonable omni directional pattern.

I picked up a flat NMO bracket from Laird in black, although they are available from other mfrs a bit cheaper. https://www.ebay.com/itm/223128247145?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649

I then drilled the top bed rail and used #8-32 stainless screws with Keps nuts which have a built in star washer that will bite through the paint for a good ground. I was a little worried about the lack of ground plane but a quick test with a mag mount in that location proved its not bad. The final testing with various antennas shows the ground plane is just barely adequate for VHF like 2M amateur and MURS but great for UHF and above. I have not tested for CB yet and and will update when I have data. I have several multiband antennas from COMPACtenna and they are known for good operation under poor ground plane conditions and they all work great at VHF on this new mount.

I also drilled through the bed rail to the side and below the mount to provide a path to hide the coax and it drops down behind the bed and up into a hole in the floor just in front of the rear seats and close to the doors. There is a plastic capped cable entry point on either side of the truck and I have quite a few cables through them on both sides now. The mount protrudes a little from the bed rail but not as far as the trail rails, so I don't expect anything in the bed to ever touch the antenna. This location is stealthy depending on your antenna size and you will never snag the antenna on bushes or trees when on the trail.

Here are a few pics of the mount, one with an inexpensive 6" UHF whip that works great on UHF amateur and GMRS and a tri-band from COMPACtenna. The 9" tall tri-band works really well and allows me to plug in any VHF/UHF/800/900MHz radio with a great match. Oops, looks like I forgot to clean the paw prints off the rear window again.

Jeep Gladiator Another antenna mounting option for GMRS/Amateur, etc. 1643149170940
Jeep Gladiator Another antenna mounting option for GMRS/Amateur, etc. 1643149188244
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rubicon4wheeler

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I'm glad I found this post. I'm looking to do pretty much the exact same thing since I know that there are very few good mounting points on a Jeep for any sort of decent ground plane. I have a Comet CA-2X4SRNMO that I use for 70cm, 2m, and GMRS and I keep going back and forth between your hood lip mount by the hinges or this forward bed rail mount.

Do you have a recommendation? A preference between these two mounting points? I don't like the hood/cowl location as much since it puts the antenna right in my line of sight, but at least I can fold the antenna down when not using it or when needing to clear trees. The bed rail by the hardtop seems ideal if the antenna can get a halfway decent ground plane.

Thanks!
 
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Radio Guy

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I'm glad I found this post. I'm looking to do pretty much the exact same thing since I know that there are very few good mounting points on a Jeep for any sort of decent ground plane. I have a Comet CA-2X4SRNMO that I use for 70cm, 2m, and GMRS and I keep going back and forth between your hood lip mount by the hinges or this forward bed rail mount.

Do you have a recommendation? A preference between these two mounting points? I don't like the hood/cowl location as much since it puts the antenna right in my line of sight, but at least I can fold the antenna down when not using it or when needing to clear trees. The bed rail by the hardtop seems ideal if the antenna can get a halfway decent ground plane.

Thanks!
The hood is a better location for tuning the antenna and all around performance. The rear bed rail will not work with all antennas due to the compromised ground plane and a UHF/GMRS or the COMPACtenna are proven to work ok. CB is out of the question without some huge effort in antenna matching.
 

rubicon4wheeler

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The hood is a better location for tuning the antenna and all around performance. The rear bed rail will not work with all antennas due to the compromised ground plane and a UHF/GMRS or the COMPACtenna are proven to work ok. CB is out of the question without some huge effort in antenna matching.
Thanks for the advice. I'm no longer interested in CB; although my JK has had CB, ham, and GMRS/FRS for the last decade, I really never used CB in it anymore. If the bed rail returned decent performance (body tub and bed floor providing adequate ground plane) then I'd prefer to mount my Comet 2m/70cm/GMRS NMO antenna there, but if you found it to be marginal at best without a no-ground-plane antenna, then I guess I'll go ahead with the hood location.

It appears that you're using the Midland MXTA27 NMO lip mount antenna bracket? Is that what you would recommend, or are the fancier brackets like the Diamond K400S-NMO better for a 40-inch antenna mounted in a high-wind location?

Your guidance is appreciated.
KK6AUH
 
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Radio Guy

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Thanks for the advice. I'm no longer interested in CB; although my JK has had CB, ham, and GMRS/FRS for the last decade, I really never used CB in it anymore. If the bed rail returned decent performance (body tub and bed floor providing adequate ground plane) then I'd prefer to mount my Comet 2m/70cm/GMRS NMO antenna there, but if you found it to be marginal at best without a no-ground-plane antenna, then I guess I'll go ahead with the hood location.

It appears that you're using the Midland MXTA27 NMO lip mount antenna bracket? Is that what you would recommend, or are the fancier brackets like the Diamond K400S-NMO better for a 40-inch antenna mounted in a high-wind location?

Your guidance is appreciated.
KK6AUH
I'm using a Laird trunk lip mount like this but found some new in package on eBay for $20 each.
https://www.ebay.com/itm/372423892527?hash=item56b6319e2f:g:GukAAOSwRJ9ghy58
The Laird is very good quality commercial stainless steel mount and so is Larsen and a few others. I suspect Midland is similar to Tram/Browning but probably ok.
 

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rubicon4wheeler

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How close must the antenna be to its ground plane for the ground plane to actually be effective? A pickup bed rail mounting location is too far above the bed floor and body tub to be able to bounce its TX?
 
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Radio Guy

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How close must the antenna be to its ground plane for the ground plane to actually be effective? A pickup bed rail mounting location is too far above the bed floor and body tub to be able to bounce its TX?
The further you get the antenna feedpoint away from the ground plane the more problems you will have with matching and overall performance. The bracket that holds my antenna out away from the bed rail is about as far as I would want to get away from the flat top bed rail. The ideal place would be to drill the top of the bed rail and put the mount in the middle of that but I don't want to cut that big of a hole there so I used a bracket.
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