Antenna question

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TreXTerra

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I have a roof tray on my XTerra.



How horrible of an idea would it be to mount both my CB and Ham antenna to this as a ground plane? The CB would be at the back driver's corner on a stainless metal tab hanging off the back of the tray. The 2M may be at the front-center of the tray on a similar tab.

Would this make an acceptable ground plane?

Currently the CB is on the tire swing (which I know is a horrible spot) and the 2M is on the hood lip just ahead of the driver.
 

Maxterra

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Ground plane wise, great.
Probably a little reflectivity off of the opposing antenna that will affect your radiation pattern, but nothing as bad as say the windshield pillar, which will have effect on SWR.

Interesting to take a magnetic antenna and move it just a few inches closer/further to the windshield post and see the reaction on the SWR reading.
 

Airmapper

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Contributor I

The CB antenna will never be good on an Xterra, to much metal junk on the roof going everywhere. HF is a tricky finicky type of RF and roof racks create the worst environment. That tray is nowhere near large enough to be a proper ground plane for HF, maybe if you had a van roof with nothing at all on it, you might get close. Remember there are two kinds of ground, RF ground plane, and electrical ground. With the layers of metal over metal, this is creating a wild crazy environment for the radio waves to launch from, so even though it's flat, it's still not simple. What makes it even worse, is those racks are insulated from the roof, so it's not bonded at all and RF won't know where to go, and you may only have one electrical ground. It's kind like trying to take off in a plane from a Wal-Mart parking lot.

A mag mount in that tray might be acceptable since it is up a little higher. Height is probably the best reason for a CB antenna there. CB is short range anyway, as long as it's working for casual on the trail comms, I wouldn't spend a lot of effort attempting to optimize it's performance. By all means tune it and do the best you can, but I'm saying if it serves it's purpose and the SWR is acceptable, perhaps that is good enough.

2M isn't picky, it will do pretty well anywhere, I have a 5/8 wave same spot as you on a bracket coming out the hood/ fender gap. Gets out fine, maybe a bit directional but so far quite good. A 2M antenna on top that tray should do fine.

Speaking from personal experience, YMMV, but once you start trying to use the roof for anything, then you realize those antennas are in the way. This is just my humble opinion, but you have a decent setup as is. Both your antennas are out of the way, leaving the roof wide open for whatever. Having my CB antenna on the roof rack for quite a while, it was a constant problem, I try to load a kayak, it's in the way. I need to go in the garage, it's in the way. Go to the drive thru, ker-thump, ker-thump, ker-thump, it's in the way. (They don't give so well when the spring is at roof height....) I got a RTT, it's in the way.

It might seem with the tray you don't intend to put anything large up there, but before you know it, someone will be like, "can you move this for me?" And whatever big item you find fits on the rack, and sticks square over where your antennas are. Or you might change your mind and start wanting to load other things up there. If your darn sure you won't, well then it's a fine place for antennas.

It's all in what you want to do, but far as I'm aware in my limited knowledge of antennas, and I'm still learning, I wouldn't be in a rush to put antennas up there just because it's new mounting territory.
 

TreXTerra

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The only things I plan to put up there are some fuel can for really long trips and eventually a net to contain things that fit inside the tray, like camp chairs. The sides of the tray (hanging off the outside) will carry an awning and high-lift.

The antennas would be mounted on tabs outside the roof tray, and I would probably see about a whip for the CB to keep it from getting smacked around too much and make it easier to just remove it when I need to go in a garage.

Thanks for the help.
 

k9lestat

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I don't storing fuel near you antenna is a good plan. If there is buildup static electricity or the like it spark a fire.

Sent from my QMV7A using Tapatalk
 

TreXTerra

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The cans are metal and would be mounted to the same rack as the antenna, so it would all be grounded together and there shouldn't be any differential charge.
 

Captain Josh

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The cans are metal and would be mounted to the same rack as the antenna, so it would all be grounded together and there shouldn't be any differential charge.
Nice tray! How does it attach? Do the bolts just go through the factory bars?
 

Captain Josh

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I should have known. Hoping to order a bumper / tire-carrier from him very soon... [emoji2]