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Author Topic: Paint damage with mag mounts  (Read 1231 times)
KE5ATF
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Posts: 31




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« on: February 22, 2007, 12:46:06 AM »

Hello all,

Just need some advice..  What kind of paint/body damage can i expect from long term (couple years) mag mount antenna? Thanks.

KE5ATF
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ONAIR
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Posts: 1735




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« Reply #1 on: February 22, 2007, 02:52:42 AM »

     I use a piece of plastic wrap between the antenna and car body.  Been lucky so far with no marks on the finish.
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KX8N
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Posts: 543




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« Reply #2 on: February 22, 2007, 05:01:53 AM »

I used one for several years with no protection at all, and I didn't have any problem.  Every so often, just be sure to lift it up and clean underneath it.
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W5DXP
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« Reply #3 on: February 22, 2007, 05:37:13 AM »

I once saw a picture of an old van that had a mag mount on top. The only paint left was where the mag mount had been.
--
73, Cecil, w5dxp.com
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K8AC
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Posts: 1465




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« Reply #4 on: February 22, 2007, 05:38:32 AM »

I had one of the large 3 magnet mounts on top of my minivan for about a year.  I used the supplied vinyl adhesive pieces supplied to cover the magnets.  When I removed the mount, I was never able to get the residue from the vinyl protectors out of the paint.  In a climate with fewer intense sunny days, it may not have been so much of a problem.
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N7NBB
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« Reply #5 on: February 22, 2007, 05:44:48 AM »

KX8N said it all.
CLEAN underneath it. Dirt, dust, moisture all work their way under the mount... Vibration helps this to happen. So at least weekly, lift it off and wipe underneath it.  When you take if off, REMEMBER there may be dirt/sand around and under it.  Lift it STRAIGHT UP... Do NOT slide it off, or twist it.  That will only serve to grind the dirt into the finish of the vehicle.
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N0RZT
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Posts: 105




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« Reply #6 on: February 22, 2007, 05:50:08 AM »

I used a magmount from '97 to '04.  By '01 I noticed a little marring, but nothing obvious unless you're looking for it.  By '03, though, there was a donut-shaped spot on the roof that was rubbed down to bare metal.

My thought at the time was that the city I'd moved to in '01 made liberal use of brine on the highways in the winter - the mist on the highways caused enough salt crystalization that I had to use washer fluid on the windshield every couple of minutes and the rear window every five minutes.  I thought that the brine getting under the magmount might have added enough abrasive to rub through the paint.  Then I realized the bare metal wasn't rusting, which suggests to me that the brine wasn't getting under the magmount.

When I used the car as a trade-in in '04, the bare spot didn't seem to have reduced the value much - I still got above the blue book trade-in value for a ten-year-old Escort at its mileage.

If you're going to use the magmount for only a couple of years, you probably don't have much to worry about.  If you're going to use it for any longer, I'd suggest moving it a few inches every year so that it doesn't rub in any one spot for long.

You may also consider other non-permanent (or semi-permanent) mounting options.  The car I drove until I took over my wife's Escort had a gutter mount.  The car I drive now has a trunk-lip mount.

Take care,
Chris
N0RZT/8
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W4XKE
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Posts: 67




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« Reply #7 on: February 22, 2007, 05:54:39 AM »

After about 4 years use on top of my pickup truck, I see some little holes in the paint (down to the primer) about the size of the diameter of a round toothpick.  Since the truck is older now and it’s hard to see the top of it anyway, I guess it’s no big deal.

What is of concern however, the parts inside the base of the MFJ mag-mount antenna are prone to rust.  (Why use steel parts in an antenna that will be exposed to the elements?)  One day I noticed I couldn’t hear much on the truck radio and a quick check indicated a high VSWR on the cable. (The antenna was about a year old at the time.) I peeled the sticker off the bottom of the antenna base and a pile of rusty junk fell out of it.  These are “fair weather” antennae unless you take the bottom apart and liberally coat everything in sight with RTV sealant.  

I don’t know whether Larsen or Diamond uses stainless steel in theirs or not but I hope to find out before I buy another MFJ antenna.   Johnny
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KB4QAA
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« Reply #8 on: February 22, 2007, 08:57:02 AM »

I've used magmounts for years with no problems.  I have used clear packing tape (Duck Tape brand) on the bottom of the mount.   The key is keeping dirt from underneath the mount.  Second always lift the mount straight up.   Periodically clean the mount and surface with a clean cloth.   Keeping a good coat of wax on the car helps too.

The ultimate answer is to bite the bullet, drill a hole and install an NMO mount.

73, bill

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K0CBA
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Posts: 295




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« Reply #9 on: February 22, 2007, 09:22:32 AM »

Not what was asked but a general suggestion for mag-mounts of any size............Keep jar lid(s), like on jars of coffee creamer, and if you remove the mag-mount for any reason, put the lid on the magnet.   It keeps all sorts of little medal bits and other thingies off it plus helps keep the magnet strong.

Obviously, if you have the multi-magnet units, find something else that will fit.

In a pinch, put a thicker plastic bag, like a freezer bag, over the magnet(s) to keep them clean when off vehicle.

CLEAN is the key to paint surface happiness.

 
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W5RB
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Posts: 565




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« Reply #10 on: February 22, 2007, 09:57:19 AM »

Do yourself a favor a spend a little time reading at www.k0bg.com .Then install an antenna securely to your vehicle .You don't say if this is for VHF/UHF or HF , but , either way , I'd drill the holes and do it right .A mag mount is , literally , an accident looking for a place to happen .

Russ , W5RB
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KB1GTX
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Posts: 460




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« Reply #11 on: February 22, 2007, 10:50:17 AM »

The most important step is to use a soft cloth
to remove all dust/dirt from both the car AND
magnet, then put a good amount of old fashion
paste car wax on the spot where the magnet will
go, don't buff it, place the magnet on the wax,
then buff the wax around the magnet.
The wax will seal out ALL water and dirt,
and when you remove the magnet years later
just use a soft cloth and a wax remover.

Dave
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N6AJR
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Posts: 9891




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« Reply #12 on: February 22, 2007, 12:10:49 PM »

instead of a mag mount, either use a clamp on mount like a diamond k400c or use a window mount.  Mfj makes a upside down U shaped piece that you slide over the top of a back window and attach your antenna there. rolling the windo up holdes it in place.

Mag mount antennas have little or no ground, and a trunk lip mount with a good ground cable will make your rig more efficient.

also I worked in emergency service for 28 years and the thought of a pound or two of metal  flying onto the back of my head in an accident will make me only use mag mounts for stationary use. never mobile.  You would be amazed. even a box of tissue in the rear windo can give you a concussion in a high impact accident (if it weigs a pound, it does not mater what it is, the inertia is the same.
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KB1GTX
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Posts: 460




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« Reply #13 on: February 22, 2007, 12:34:34 PM »

"flying onto the back of my head in an accident"

I'm not to sure, BUT would'nt the antenna work
better on the OUTSIDE of the car!

 
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K4III
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Posts: 206


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« Reply #14 on: February 22, 2007, 01:10:48 PM »

Be careful when putting something between the magnet and the vehicle because it reduces the strength between the magnet and the vehicle. Also, when driving at higher speeds, it will cause the antenna/mount to vibrate and you will get holes or abrasion marks on your finish. Remember the mag-police light on Clouseau's car in the Pink Panther? You don't want it to become a flying weapon either!

Secondly, I have not used any brand magnet mount that doesn't have steel in it that rusts in moist, damp or wet climates such as here in Florida. Whether Maxrad, Antennex, MFJ, Larsen, etc... Don't expect them to last more than a few months before rusting either around the steel base, or internally. They are meant for "Temporary use".

Unless using an antenna for a few days or a short trip, purchase a lip mount, glass mount, or simply drill an nmo! If you purchase a NMO mount, I recommend the NMO brass ones and not steel, as they will rust and short here in FL. The UHF types are NOT water-proof. AND remember, a glass mount will not work over heater elements, tinting, near am/fm in-glass antennas, or on special types of glass that have safety ratings to powder instead of producing shards in an accident such as front windshield glass in most newer vehicles! AND don't expect to mount a 50+ inch high-gain antenna on glass, or to an nmo mount on your thin metal roof!!! Unless you want a homemade sunroof!

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