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Author Topic: Mobile 2m Antenna Mount Quandry  (Read 702 times)
KD0FLE
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Posts: 26




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« on: February 18, 2010, 08:22:27 AM »

I am looking for a solution to my 2m/440 ant.  Have been running a Diamond NR440 AH.  I had it mounted on a Diamond heavy lip mount.  That was broken yesterday when a small limb caught in the coil of the antenna and broke the aluminum mount in two.  I don't want to have to take my 2m antenna off every time I go in the woods.  I do that with my ATAS 120.  Here are some pics of the truck.

http://s94.photobucket.com/albums/l92/bjfergpls/HAM/

My idea is to mount a light and very flexible whip on the front portion of the roof rack.  The front bar of the rack should protect the mount from damage.  It has a large flat steel plate that could allow this.  I realize I might have to bond the rack to the truck, that is no problem.  Is there an antenna out there with a thin flexible whip and perhaps a spring at the base?
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K0BG
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« Reply #1 on: February 18, 2010, 09:23:03 AM »

Buy yourself a standard old 1/4 wave whip, like a Larsen NMOWBQCK, and the matching 90° angle bracket. If you bend it, just straighten it out, and you're back in business. Mounted high on the rack, it will probably out perorm what you used before.
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KD4LLA
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« Reply #2 on: February 18, 2010, 02:44:18 PM »

I use a Comet CP-5NMO with a 1/4 wave whip on my vehicle.  Bought the whip at a local Motorola shop for $8.  It is mounted as high as possible on the door.  Many things will break and bend before that 19" whip gets hit.
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KC7YRA
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« Reply #3 on: February 18, 2010, 07:46:05 PM »

I have outlined my favorite VHF antenna for offroading before, but I will do it again as it has been while.

When I set about designing my radios for my vehicles, I went in with the intention of designing antennas that refused to break.  Even if I rolled my truck, they will work.  I figured that I could go with something very stiff that could shrug off the hits, or something very "floppy" that could just bend out of the way.  I tried the floppy idea by stretching a CB antenna spring out.  It worked great but it would lay down as I traveled down the highway and it was hard to tune up at VHF frequencies.

I eventually came up with a design that I now use on all of my heavy off road vehicles and my 4 wheelers.  I have NEVER had one break and have beat the ever loving crap out of them.  I have even used them as tow point to pull stuck 4 wheelers.

You will need a very strong steel plate as your mount.  Very heavy duty (1/4 inch thick is about right) and secured to the vehicle very well.

Drill a 1/2 inch hole and mount one of these into it

http://www.hamstick.com/275.html <--- standard 3/8x24 CB type mount.

Then find some old 102 inch CB whips for cheap.  Cut them down to 19.5 inches (leave it a little longer to tune once it is installed) and screw them into the mount.  If you are worried about skewering yourself, drill a hole in an old golf ball and glue it onto the end of the antenna.

As you can imagine, this antenna will not break.  It MAY bend, but it takes more than a few tree branches to do it.  I have rolled my 4 wheeler with mine and it is just fine.  If you really get to beating them up, the mounts can sometimes break but you have to sheer it off on a low hanging bridge or something.  They are very broad band as they are so thick and they tune up great on 440 as well.  Plus they are easy to repair on the trail.  Everything can be removed externally and replaced quickly if needed (very rarely though).

And you don't have to worry about them laying over at highway speed Smiley

Give it a shot.  Ugly but it works

Brad
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KD0FLE
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« Reply #4 on: February 19, 2010, 09:09:17 PM »

So far I cant find the Larsen NMOWBQCK.  What about the NMOQ antenna cut for 2m 1/4 wave.  Wouldn't this also work on 70cm as a 3/4 wave? I am running a Kenwood TM D710A and have gotten used to using cross band repeat to extend my HT range on the farm and at work when in the woods by myself.
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K0BG
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« Reply #5 on: February 20, 2010, 06:22:57 AM »

It is a standard Larsen NMO 1/4 wave, in black, with a coax kit. Each of the three parts are usually carried separately. AES and HRO both carry the antenna, but in the three parts listed.

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