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Author Topic: 2 antenna mounting options - which is the lesser of two evils?  (Read 8413 times)
W3LK
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Posts: 5644




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« Reply #15 on: September 22, 2011, 11:02:31 AM »



I know it is a 10-year old car and all, but I still talk to her about these kinds of things.  It doesn't matter to me who paid for what, I look at it as me respecting her enough to talk to her about it.  (But we both paid for the car and both pay the insurance on it as we do with our second car).  And if I started getting into a whover paid for it gets to make the decisions debate with her, I would surely lose...   I am a teacher, and she is an RN...    She wins.   Grin Grin Grin



Well, we know who's the boss in this household, don't we? <ggg>

I understand what you are saying, but problems drilling a hole in a 10-year old vehicle??? I haven't had a vehicle in the last 40 years that didn't have holes for antennas of some kind drilled in the roof the weekend after it was brought home.
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W0FM
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« Reply #16 on: September 22, 2011, 12:28:58 PM »

Your concern about getting a quality NMO mount (not a Pacific-rim knock-off) can easily be addressed by going to your local two-way dealer's shop.  A Motorola dealer will for sure have genuine Motorola mounts as well as quality alternatives.  Other dealers will have access to the Motorola mounts or offer good quality NMO mounts from Antennex and Larsen.  If I recall correctly, the Larsen 270NMO antenna is supplied with their good NMO mount in one of their bundled packages.

Or, like someone else said, have the local commercial two-way shop drill the hole for you and run the coax.  Some, depending on insurance requirements, may even let you watch and learn so you'll be more comfortable doing the next one yourself.  Good luck and have fun.

73 de Terry, WØFM
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M6GOM
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« Reply #17 on: September 23, 2011, 04:34:33 AM »

I would assume that an NMO in the same rear position but towards the center would at least do that well? 

What you will find is that it will become directional. You will find that if you are pointing away from the receiving station you are weaker than if you are pointing at it.

I have a friend who has several antennas on his car - an Astravan with a flat back so like a smaller SUV at the rear - no trunk. On his 2m one, it is towards the rear of the car...about 2ft from the back. When he gets to about 5 miles away I can tell when he is changing direction by the increase or decrease in signal strength.
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K0BG
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« Reply #18 on: September 23, 2011, 05:47:02 AM »

Read this: http://www.k0bg.com/images/pdf/mobile_vhf_ant.pdf

Danny Richardson, K6MHE, wrote this article for CQ some years ago. It is on my site by permission. Or, if you want the other companion articles, go to Danny's site.
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KF6CNP
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Posts: 11




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« Reply #19 on: September 23, 2011, 02:28:04 PM »

OKay, well I am sitting here at work and just jumped in with both feet... ordered the antenna and an NMO mount from HRO...

Thanks for entertaining all of my ramblings...  I have had my license for a while, and am finally starting to get into it.

I'll have to let you know how it come out...    Grin
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N6AJR
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« Reply #20 on: September 30, 2011, 09:03:27 AM »

Heck if you are just doing repeater and local simplex work on FM, then most any thing will work.  a couple of hundred mils will heat the repeater and it does all the work.  you could use a HT and a MFJ 310 and a rubber duck and do good, just roll it up in the window with the rubber duck up there and the radio in here. ( see the link below. it also works great on rental cars, wife cars and friends cars, no scratches, no holes) 

if you were doing 2 m tropo or 2m cw or ssb, you would probably have a halo or 2 or a small horizontal beam mounted on your mobile. so yea, a trunk lip mount is OK, and drilling the hole is better, but you may not need it.  another choice is to get another  matching trunk lid from the scrap yard, and drill the hole in that, and mount it, then when you sell the car, put on the original "good" trunk lid with no holes.

http://www.mfjenterprises.com/Product.php?productid=MFJ-310
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W6RMK
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« Reply #21 on: October 02, 2011, 03:27:09 PM »

One thing to look at is how the roof rack actually mounts.  On my VW Passat, there were plastic caps at the fore and aft ends of the side rails that popped off.  Under the cap was a nice 3/8" (approx.. it's metric) bolt which holds the rack onto the roof.  The cool thing is that you can take the bolt out, and put a bracket under it to hold your NMO swivel fitting, and you get a really good ground connection AND there was easy access through a rubber gasket through the roof into the "under headliner" space. 

So, you get good ground, good mechanical connection, looks like it was designed to go there (I had to machine a small notch in the plastic cap to clear the bracket) and leak proof pass through for the coax.

Sure, it was probably an asymmetric pattern, but realistically, anywhere you put the antenna is going to have that sort of problem.  If you put it dead center in the roof, then you can't use the rack.

(I did have a screwdriver HF antenna mounted in the rack for a while.  I built a large aluminum plate that mounted to the rack with u-bolts, and a wire to the rack mounting bolt for the ground plane, etc.)  It worked fairly well, but it was a real pain to work with.  You can't see the antenna, so you don't know where it's tuned. You can't use the rack, it's hard to demount the antenna for going into garages, etc.  I finally went to a front bumper type mount for the antenna, which worked better (longer whip), was visible, and was much easier to work with all around.)
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KQ6Q
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Posts: 967




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« Reply #22 on: October 04, 2011, 12:08:59 PM »

The hood seam mount location can be very desirable if you EVER drive your SUV into a parking garage with 6'6" clearance - which I do every day. If you use some Comet mounting hardware, it has the first couple of feet using tiny coax which gets you past the hood opening. If you're using repeaters, the hood seam will be good enough. The downside is that you can see the antenna flutter in the wind, which can be distracting if you're using an antenna in the 40" range. My solution - i keep the long antenna handy, but drive using a short spike for 2m/440, which gets the job done for me - and if I'm in a situation where I need a better radiating element, I put the long one on the seam mount. Also, keeping the roof uncluttered makes it less hassle when carrying a boat!
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