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Author Topic: 2m/70cm antenna options for Saturn wagon.  (Read 1016 times)
KC8SDW
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Posts: 3




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« on: October 23, 2001, 03:49:47 PM »

I just got my ticket a few months ago and am fixing to make my first big equipment investment, a dual band mobile for my car.  I already have a IC-Q7A which is fine for what it is, but I'd like to get into, ah, the watt range.

I've about decided that I want to get a Kenwood G707A, but I'm kind of stumped on how to manage the antenna.   My car is a Saturn station wagon.  The good news is that it's a '93, so I don't mind drilling into it here and there, and experiments with the Icom have yielded no horrible ignition or other noise problems around 144 and 440.
 
The bad news is that it's a Saturn, so the roof is NOT metallic, and it's a wagon, so there's no trunk.  I could stick a mag-mount on the hood (the only groundplane like surface on the car) but it would look silly and probably not perform so well.

What kind of system would people recommend?  I'd like the antenna to be dualband, and to install with minimal fuss.  Recommendations on specific brands and where to buy would be particularly helpful to me.

-Ben
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WB2WIK
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« Reply #1 on: October 26, 2001, 05:28:16 PM »

I don't have any great brand loyalty on this, but have you considered a dual-band "glass mount" antenna?  It may be the only alternative you have.

Antenna Specialists and others make VHF and UHF vertical whips intended specifically for use on non-metallic cars -- these are "ground independent" designs that work just fine when mounted on plastic.  The ASP-861 2m whip from ASP is one example of this, and it works well (I have one).  But I don't think they have dual-band versions.

73 de Steve WB2WIK/6
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N2MDB
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« Reply #2 on: October 29, 2001, 04:14:34 PM »

Another option might be to put a ground plane in the roof...I've never done this but I have heard of hams that put strips of metal going from the antenna mount (drill-through roof, not magmount!) out and glue them to the underside of the roof (you would probably need to drop the entire headliner). Maybe even a thin piece of lightweight metal and just line the entire underside of the plastic roof, turning it into a metal roof for RF purposes?
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KC8PBS
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Posts: 7




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« Reply #3 on: October 29, 2001, 07:58:51 PM »

There is a copper tape with one sticky side that is available in various thickness and width. You can drill a hole of the proper size for an NMO mount in the center of your roof, then stick this tape to the underside of your roof (of course, after you remove your headliner) and roll it out in 4 or 6 directions from the hole. Make sure the tape goes right up to the hole so the NMO mount will make good electrical contact from compression. These pieces of tape will function as ground radials. Put as many in as you want. I suppose you could even solder them to the base of the NMO mount. Once the NMO mount is installed, you can choose a large variety of dual or tri-band antennas. A low priced 2m/440 antenna is the one made by Midland
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KB9YNB
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« Reply #4 on: November 01, 2001, 01:31:01 PM »

Are you sure that the roof is not metal?  I know that Saturn makes it's fenders and doorskins out of plastic, but I can't imagine a plastic roof being strong enough to pass crash tests.  Also, it may be a plastic skin over a metal frame, which may provide enough ground plane to "flatten out" your radiation pattern.

I think a dualbander mounted through the roof even with no ground plane would still be better than a glass mount!

The sticky copper tape sounds like the cheapest idea to me if you're on a plastic roof.

Another idea would be to get a large sheet of thin copper, and stick it to the roof with some sort of adhesive. (I'm sure that 3M makes some kind of sprayon adhesive that would work!!!) Then, drill the mounting hole, install your mount.  Next, cover up the antenna mount and paint the ground plane to match your car.  I know it's a litte extravagant, but I think it would work!

2 things about that:
1. I don't know how well paint will stick to copper
2. If you miss a spot, you'll have that rustic, aged collegiate look as the copper turns green.  I'm not sure if that's a good or a bad thing.

Just some thoughts on the subject.

KB9YNB
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KC8SDW
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« Reply #5 on: November 01, 2001, 11:12:59 PM »

Many thanks so far for all of the suggestions!

Right now I'm thinking of going for a dual band glassmount.  Larsen has a half-wave one that from specs seems to perform tolerably.  Allegedly one loses 0.5dB through the glass.  This doesn't seem too bad for me, since this thing ought to have decent radiation resistance.   More to the point, if I *really* want that half dB back, I can always replace the 14 feet of RG/58U with something a bit less lossy like LM-400.

If the roof of that Saturn is metallic, it's certainly not ferrous; magmounts do not stick to it even vaguely; neither will a strong-enough-to-be-finger-breaking-dangerous magnet I got from an ancient 8 inch mainframe hard disk drive.

The suggestions about making my own ground plane out of copper tape/strips are interesting, and I'll consider them further if I ever try to put a HF antenna on this vehicle ($ and license upgrade of course make this a far future project).  The one thing that concerns me about this technique will be familiar to anyone who ever has driven around with a tarp covering the load of a pickup truck.  Air gets into the darndest places and I can just visualize a square meter of copper and a few meters of whip ripping off the top of my car...

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TEMPSIGN
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Posts: 3




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« Reply #6 on: November 14, 2001, 11:47:47 PM »

Funny that a magmount wont stick to it - I am in a very similar position, just got my ticket and ready to move past the Alinco HT. Unlike you, my 97 Saturn wagon DOES have a metal roof, and the Hustler 5/8 magmount sticks just fine at least up to 75mph. Nonetheless, there may have been some changes.
I looked at the possibility of a trunk-lip type mount on the top of the back hatch, but it counter-rotates inward at the top. However, if you look under the top of said hatch, you may find (as I did on mine) that there is a large flexible tube for wiring running near the centerline. Also, on each side there are plugs that can be popped out, and look to be large enough to run RG8!
Although the magmount works fine on my car, I still want a more permanent solution. I am considering putting roof racks on and mounting a 'tenna on the front rack at the center. Roof racks can actually increase the value of the car if done right, and be useful for all kinds of things. The cable could be run along the rack to the side and down the side to the back, working it's way into the car via the aforementioned plug/tube arangement.
Aside from that, I saw a diagram in my research that indicated that a top-center windshield mount is the second best choice to a center-of-roof mount, and it does get you awfully close to the radio already.
Best of luck, please post how it works out!
wayne
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