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Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

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  #21 (permalink)  
Old 04-25-2017, 10:58 PM
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Quote:
Originally Posted by mrweather View Post
Where did you put it? The hardtop is entirely plastic (I know I have a 2016 Wrangler Unlimited)
My RV has a fiberglass roof. I glued a sheet of galvanized to it as a ground plane for the mag mount. Good SWR and range.
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Old 04-25-2017, 11:14 PM
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Originally Posted by jwt873 View Post
Mag mounts may scratch, but most scratches can be buffed out... Holes drilled in the body can't.

I've got a 2016 Jeep Wrangler... I installed a mag mount as a temporary measure, but it's worked so well where I put it, that it has kind of become permanent
Static mag mounts scratch the clear coat (which as you said, buffs out). When they fall over, that's when they scratch deeper.

The other issue you run into (say with permanent mag mount installations) is the paint around the mount fades with time…the paint under the mount does not. So at some point that 4" or 6" magnet leaves you something you can't buff out and the only way to fix it its to repaint that panel. For all intents and purposes, filling a 3/4" hole is not difficult…a 5/8" slug in the thickness required and a little spot welding, some TLC rubbing it out and it's as good as new (if the end result is repainting anyway).

Wranglers are easy for NMO by the way…a flat NMO bracket and some sheet metal screws and you get a fender mount who's mounting screws are hidden by the hood when closed. Best part, the bracket runs $4.
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Old 05-20-2017, 4:47 AM
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One could use a rubber boot on the magmount base if they are worried about scratches.

http://radio-accessories.com/gromagn...ubberboot.aspx
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Old 05-20-2017, 5:13 AM
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The science here is being presented as some kind of a revelation - the gain differences are so small as to be irrelevant, and pointless! The only reason for not using a body through mount is drilling a hole in an expensive vehicle, impacting the resale value, the possibility of starting corrosion at the hole, and the frequent issues with routing the cable through interior linings and panels that don't want to come off!

Centre roof with a mag mount means loads of cable flapping around.

On the other hand, mag mounts need regular removing and cleaning because like magnetic vehicle signs, road grit gets under them and gentle scours the paintwork, so leaving them on permanently means a discolouration that might not polish out.

It's just a personal choice.
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Old 05-20-2017, 12:41 PM
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Originally Posted by KT4HX View Post
One could use a rubber boot on the magmount base if they are worried about scratches.

GRO Rubber Boot for Mag Mounts
That's only part of the issue.

The issue not addressed by a "boot" is that dust road grime, etc. get underneath. That can discolor, or get ground into the paint.

But, like I said above, if you've got an older car or are not concerned about the paint, then it really doesn't matter.
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Old 05-20-2017, 12:44 PM
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Default A case in Favor of Mag Mount Antennas

So this is actually one of my co-workers vans. This is the side but please note the rust rings on the side panel.


You're probably asking your self, why would a two-way tech have antennas on the side of his van? Well, the antennas are mounted on the inside of the vehicle…the rust rings are on the outside though. Even then the ferrous particles that bombard your paint on a daily driving basis still ate through the paint.


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Old 05-20-2017, 12:49 PM
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Oh yeah, much better than drilling a hole!
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Old 05-20-2017, 2:54 PM
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On another forum, somebody was trying to sue somebody because dirt had got under the contact point and worn the surface away - and some really technical replies surfaced. Rubber, was frequently suggested as a solution, but also provides a non-porous conduit for moisture - temperature changes 'suck' in moisture and it contains minute particles of grit - and the vibration acts like a rotary sander, which easts through the lacquer applied to the paint on most modern vehicles. So while the idea of the rubber boot appears sensible, it actually does the same as a magnetic vehicle sign, which is well known for destroying paint finishes if left attached for anything other than short periods. Bearing in mind hole plugs can be pretty invisible and nowadays colour coded to match the paint, the through body 'repair' can often be less of a price hit when you sell. Just down to choice isn;t it?
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Old 05-20-2017, 6:44 PM
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"Rubber" is like "wood", it's all the same right?
Like lignum vitae, which is harder than some metal alloys. While balsa can be crushed in one hand.

Folks who live (or drive) alongside RR tracks have a special problem because of iron particles in the air, thrown off when steel wheels roll on steel rails. Folks who live under airport flight patterns get lots of soot, from unburned jet fuel (kerosene) when the aircraft are landing and taking off. All kinds of circumstances are invisible to the average driver--but they exist.

In some markets no one gives a damn about a patched hole or a patched fender. In the *larger* markets where they have a bigger choice of used cars? More likely to compound out some scratches, than to try getting a roof repaired--which involves a major paint job when the 'roof' isn't just a small distinct body panel. That one small plug in a roof mount's hole will probably reduce the value just as much as having a fender torn off the car, in the large markets. People would rather just buy another car, and not worry about leaks. Which no used car business is going to give you a guarantee on.

"...a non-porous conduit for moisture..." Eh, funny phrase. At some level either it IS porous or it ISN'T. If water can get through it at any level, it is porous. Just like Gore-Tex, which is both waterproof and porous. Get into a car with heated seats on a rainy day, wearing a wet Gore-Tex jacket, and you'll quickly find out how porous it can be!
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Old 05-21-2017, 3:30 AM
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You misunderstood - non-porous rubber sitting on top of non-porous paint surface - capilliary action draws outside moisture into the gap.
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Old 05-21-2017, 10:36 AM
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OK. Now that makes more sense. I've long used a piece of clean saran wrap between the magmount and the roof, to ensure there's no grit stuck in there, after a wipe of both. And since it doesn't sit out there when it is not in use (i.e. parked overnight) no worries about significiant capillary actions.

One car wash can do more damage than a lot of magmount.
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