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Author Topic: MagMount on rented vehicle  (Read 521 times)
KC9EOS
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Posts: 37




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« on: June 30, 2004, 04:47:30 PM »

Looking for your experiences in using a mag mount antenna on a rented vehicle. Is there a way to do this and minimize the chance of scratching the finish? How do rental companies feel about using an antenna? I am aware of the protective boot that Antenex offers. Does something like that affect the ground of the antenna? Any way to do the same thing without buying another mount? Thanks for your thoughts!
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AC5E
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Posts: 3585




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« Reply #1 on: June 30, 2004, 04:56:19 PM »

I have used a couple of layers of thin plastic, sandwich baggies or bread wrappers, for temporary duty. I remove the mag mount and thouroughly clean underneath it, as well as replace the plastic daily.

So far I have not been able to find a scratch on the rent-a-skate, and as long as Avis, Hertz, or Wrent a Wreck does not find a scratch or see the antenna they have no reason to complain.  

73 Pete Allen  AC5E
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N4KZ
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Posts: 599




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« Reply #2 on: June 30, 2004, 04:59:50 PM »

I've used mag mounts on rental cars without incident. But I was sure to mount the antenna only after I left the rental agency and remove the mount before returning the car.

If they don't see the mount, there will be little reason for them to examine the roof or trunk for scratches.

Prolonged use of mag mounts do cause small scratches but I never had any problem after only a day or two with a rental car.

Enjoy!

73, Dave, N4KZ
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WB2WIK
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Posts: 20613




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« Reply #3 on: June 30, 2004, 05:01:48 PM »

I wouldn't care about how the rental car company feels about antennas.  What is important is to minimize damage to the car finish, of course.

I've used mag mounts on rental cars for 25+ years and really never scratched one, at least not noticeably -- but then, my rentals are pretty short-term (like a day to five days) and once the mag mount's slapped on, it stays there until a few minutes before I turn the car in.  Minimizing the number of times you install/remove the mag mount, as well as being careful not to tug on the coax feedline while the mount's installed, really helps minimize any damage.

I use the Larsen NMO mag mount for all VHF-UHF antennas.  It's about the best one I've found, in terms of performance and longetivity, and it does have a thin Teflon (or similar) insulator between the magnet and the car contact surface to help minimize damage.  That material, in the thickness Larsen uses, does not appear to degrade electrical performance for VHF-UHF whips in the slightest; however, it may not be suitable for lower frequency work.

WB2WIK/6
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K6AER
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Posts: 3525




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« Reply #4 on: June 30, 2004, 05:29:35 PM »

Remember always cover road dents on rental cars with mud. When discovered you can blame the car wash. As mentioned before put the mag mount on after leaving the rental yard and remove before ariving for the return.
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KC8VWM
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Posts: 3121




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« Reply #5 on: June 30, 2004, 05:45:19 PM »

Be sure to drive back to the rental car location with your HT blaring an ID at full volume when it is on your favorite repeater frequency.

I am always trying to get the maximum value for my rental car money, so I am always sure to hire the  assistance of the car jockey in the removal of several military grade HF boatanchor rigs that are laying on the italian leather passenger seats.

Although It does take me a while to remove my 20 element EME array off the rental car, I always find that the staff never ignore me, and seem rather attentive when I pull in.



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KZ1X
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Posts: 3228




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« Reply #6 on: June 30, 2004, 06:11:58 PM »

If you use the sqaure Larsen base, it does no damage.

Rental car companies do not care if you use their vehicles as antenna supports.  

Cars were MEANT to have mag-mounts put on them, anyway.  Why do you think most cars are made out of steel?  The first cars were wooden, remember.  Wooden cars made a lousy ground plane (but could be eaten by termites), and by the time commercial radio broadcasting took off in the 1920s, cars were being made of ferrous metal and are still being made that way today.  Take advantage of this.
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N6AJR
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Posts: 9912




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« Reply #7 on: June 30, 2004, 09:27:18 PM »

There is also a little gizmo that is shaped like an upside down U squeezed together. it goes over one of the rear windows, it has an antenna mount on the outside and a cable to your ht on the inside.  you rool down the window, slip this on and roll up the window.  its made for a ht antenna but can be adapted for any small antenna,

so make your own, some thin cable (rg174 is 50 ohm) a piece of metal, bend a flat, drill a hole to put the antenna on, then the narrow upside down u and cut a hole in the middle for the cable to lay in.. no scratches.
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V73NS
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« Reply #8 on: June 30, 2004, 10:17:39 PM »

<<Does something like that affect the ground of the antenna?>>

A mag mount has a ground??
Think about it!
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WB4QNG
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Posts: 362




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« Reply #9 on: June 30, 2004, 10:23:21 PM »

Do it and forget it. If the only damage a rental car is the small scratch it might get from a mag antenna. Then they would be in good shape.
Terry
WB4QNG
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KB1LKR
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Posts: 1898




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« Reply #10 on: July 01, 2004, 09:26:21 AM »

"A mag mount has a ground??"

At DC, no, but in VHF/UHF yes, due to the capacitance from the conductive foil under the magnet to the steel roof.
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KD5JFT
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Posts: 82




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« Reply #11 on: July 01, 2004, 11:32:21 AM »

"There is also a little gizmo that is shaped like an upside down U squeezed together. it goes over one of the rear windows, it has an antenna mount on the outside and a cable to your ht on the inside. you rool down the window, slip this on and roll up the window. its made for a ht antenna but can be adapted for any small antenna, "

I used one of these devices (still do) on my work car.  It scratched the window tint on one vehicle, but has not done so on the others.  When I got my new car, I put some felt on it to minimize the chance of damage.  I found it works OK with my HT; at least much better than the antenna on the HT inside a car.  I have seen them with sma, bnc, so239, and pl259 connectors.  I have not seen one with N or smo connectors.  Good Luck

KD5JFT
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WB2WIK
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Posts: 20613




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« Reply #12 on: July 01, 2004, 12:22:36 PM »

Bear in mind that permanently-installed (through a hole in the vehicle's sheet metal) antennas are safe, and most other installations are not, under some driving conditions.  Mag mounts are intended for *temporary* use, not daily, permanent use.

If you want to try your own "safety" test: Install the mag mount, bring the coax in through the vehicle window, and get ready to operate.  Then, find a long stretch of unoccupied roadway, accelerate to 70 mph, and jam on the brakes hard, simulating an emergency stop.  Your tires should screech.  See what happens to the mag mount.

Now, imagine decelerating forces about fifty times higher than that, simulating a crash.

After I witnessed one mag mount, complete with whip, fly forward at 70 mph or so and go crashing through the rear window of a second vehicle (the one that suddenly stopped, causing the crash that ensued), I decided mag mounts are definitely for occasional, temporary use.

WB2WIK/6
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KD7EVS
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Posts: 84


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« Reply #13 on: July 01, 2004, 04:00:12 PM »

hehe, yeah.   I went storm chasing in a rented vehicle one time.   1/4 wave mag mount and 2w HT in service. I got on a road broadside and as a gust front was approaching. (trying to get south).    well, good thing the coax wasn't very long and the antenna didn't fly very far Wink hihi.   I was doing 60ish and the antenna was holding fine. when the gust hit the antenna flew off sideways! I'd estimate a 65+ mph gust. (recorded wind later at 50+)   one of you pilots that happen to have your flight calc nearby do the total wind component (reverse headwind/crosswind component) with a 60mph headwind and a 65ish crosswind. Smiley

though I'd say if your storm chasing in a rentawreck then the mag mount is the least of their worries.


remember the old addage.   Its almost always easier to get forgivness than permission!  legal note: this however does not apply to putting an antenna on your wife's car!  (is it only availible in black or silver?)


legal note #2: with this post I disavow all knowledge of ever having rented a vehicle, storm chasing in said vehicle (which I never rented) and placing a mag mount on said vehicle (which I never rented and never storm chased in).  


Seven Three
zeb
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K1CJS
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Posts: 6046




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« Reply #14 on: July 01, 2004, 08:52:55 PM »

"<<Does something like that affect the ground of the antenna?>>    
A mag mount has a ground??  Think about it!"

Yes, a magmount does have a 'ground', at least at VHF-UHF frequencies.  Think about this--A window mount antenna for 2 meters works.  Why?--There is glass between the inside and outside mounting plates.  So what 'couples' the antenna to the cable connection?  A capacitive transfer is the answer.  The same applies to a magnetic mount antenna.  The ground is achieved through capacitive coupling.  And a happy "Think about it!" right back to you!  73!
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