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Thread: Mobile antenna mounting locations

  1. #1
    syntrx No Longer Registered

    Default Mobile antenna mounting locations

    I've just bought a 2009 Holden Colorado crew cab pickup, and at the moment I'm planning a VHF and UHF install. The tub has a bar that runs up behind the cab at roof level, that I'm considering mounting my antennas on.

    I plan to go with "no ground" antennas (end fend half wave or similar), with one on each side of the truck, mounted to this bar using angle brackets. Is there going to be a huge performance difference in mounting antennas up on this bar, this compared with popping holes in the roof?



    I need to cover the 2m ham band as well as 157/162MHz business band pair on VHF, and 411-477MHz on UHF (though I rarely use 477MHz, so realistically I'll probably only need 411-439MHz.) I'm thinking of going for a Larsen NMOWB150B on VHF, and a Maxrad BMWU4002S on UHF, mounted to L-brackets screwed to the back of that bar, one antenna on each end of the trunk.


  2. #2
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    Quote Originally Posted by syntrx View Post
    I've just bought a 2009 Holden Colorado crew cab pickup
    I keep forgetting its not a Chevy outside the US, lol. Those are nice little trucks!

  3. #3
    Swailes No Longer Registered

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    If you are not using ground planes, then there should be no difference in performance.

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    Honestly, to cover that much bandwidth on VHF you are going to need at least a 1/2 wave or have terrible SWR on one end of your desired limits. Same thing with UHF. The bad part is you aren't going to get any gain by using such a wideband antenna.

  5. #5
    syntrx No Longer Registered

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    I know. gain's not too much of a problem, the terrain around here is pretty hilly so at 25W I'm limited more by LOS than anything else anyway. I figured I'd keep a 5/8-wave around for when I'm out of town and only need 144MHz.

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    I really recommend a 1/2 wave for VHF over 5/8.

    1. The length difference isn't that much and the end-fed 1/2 wave needs no ground plane. Plus the shorter 1/2 wave won't scrape garage rooftops as badly.
    2. The 1/2 wave is usually made of much stiffer stock that doesn't deform and bend in the wind as you go faster like the 5/8 wave vertical does.
    3. The 1/2 wave doesn't have all the Fresnel and edge diffraction problems with the curvature of the ground plane (the car's body or roof which is not flat).

    This is from years of trying and using both on and off. Also, technically All in all, for 3 very good reasons, the 1/2 wins - the only thing a 5/8 has going for it is SLIGHTLY higher gain, but not worth the extra problems it brings to the table.

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    Have a look at the Sinclabs SVB-1382. It is a 1/2 wave VHF with about 5MHz of bandwidth. NMO mount, but doesn't require a ground plane.

    They also sell an SVB-1482. It is also a 1/2 wave VHF with 26MHz bandwidth, however it does require a ground plane.

    They also sell UHF versions of these.