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Trucks, garage doors, and antennas


Bugkiller
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No, not the title of a bad you tube video.  Noob here, still contemplating how far down the GMRS rabbit hole I want to go.  Next logical step, (to me, as I have HT radios currently) is a mobile unit.  If I do it, well I will go all in and get a 50w unit.  

Now for the tricky part.  I have 7+ inches of clearance between my roof and garage door.  Not much room for an antenna.  Yet, isn’t that the best place to install your mobile antenna, the roof?    But does the low clearance limit the quality of antenna?  If so, is it better to go with another mounting surface to be able to put up a better antenna?

Just wanting to hear from you folks with experience.  I would think this isn’t a unique to me problem.  

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It's hard to say without some sense of what distances you're working with, and what the terrain is like. The standard 1/4 wave for 450-470 is 6",  and with a drilled through should give you the clearance you need.  I'll have to look at how much height the mag mount adds (I want to say 1/2").Alternately, how much height can you get away with from the fender top? (Subtract am inch for mount height, to account for bracket or lip mount) 

Pattern wise, the 1/4 wave will generally be more omnidirectional,where a taller gain antenna  is more of a squashed donut (more gain, more squish).

A 5/8 there would be no problem on the fender or bed rail at around 12", but I think the double 5/8 browning I have might be close again at around 36", though it's sprung so a little rub might be okay, vs if it hit close to the base on a roof mount. The comet 2x4sr is even taller, but it also folds...is folding it to park feasible?

edit: did some measuring; the browning comes in at 34.5", the comet at 39" upright, and about 6.5" folded (just under 6" at the base, but there's a little spiral in the middle, and it doesn't fold quite 90 degrees), and the midland mag mount is ~3/4".  surface mounting a 1/4 wave looks feasible, or the browning on a fender/lip mount if you want the gain...from what i saw, it was under 1.2:1 swr across everything i've used in GMRS and 70cm. the main reason it's not on my truck at the moment is clearance for the work garage (smaller truck, so a ~12" 5/8 wave is just low enough, though i have a 1/4 wave on now).

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You could get a STI extra flexible whip and cut it down to tune.  I was looking for the video where the guy basically sings as his antenna is whipping the garage as a beat. For most of us it is the "song of our people."

 

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I have the Larsen NMO2/70sh with the spring base, it's commercial partner is the NMO150/450/758 (is also on the roof for my scanner) which would be the one tuned better for GMRS. Both get wacked off the parking deck at the hospital often, and even get beat up by the car wash without any issues.

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10 hours ago, gortex2 said:

a 1/4 wave on the roof would be fine. I had 4" in my old garage. got the stico flex whip and never had an issue. Center of roof on an NMO will be good. 

Those StiCo antennas are awesome. I have used both StiCo and the Laird Phantom antennas, for UHF commercial band and GMRS. Not as efficient as a longer whip, but still viable and useful, and better than just a handheld inside of a vehicle. My Laird Phantom antenna was not on the roof though, instead being mounted to the lip of the trunk of my old Pontiac, and many people said I wouldn't get more than a few miles on GMRS. Managed to do pretty well, and could hit local repeaters just fine. Good luck on your install.

Pontiac Beach.jpg

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Midland's 3 dB "ghost" antenna is 3 5/8" tall.  Add about 1" for an NMO mag mount.  It works.  But is only +3 dB.  It comes in a package deal with some of their radios, including a clamp mount suitable for a mirror or roll bar.  I'm installing it this PM on my Acty Attack's "roll bar" this PM. 

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