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Discussion Starter · #1 ·
I recently bought a camper shell for my Tacoma. It has the Yakima bars installed, and I thought this would be a great place to install a CB antenna. I bought a mount that was intended for installation on a semi's side window and installed it on the front Yakima bar.

I attached a 3' Firestik, ran coax loosely from the mount, through the door, and into the cab for testing purposes only. My SWR was off the scale. I realized the the Yakima bars aren't grounded and therefore the mount isn't either, so I ran a fat ground cable from the mount to one of the truck's frame rails. This caused my SWR to fall below 1.5:1. I felt this was good enough, and decided to make the installation more permanent.

Now that I've run the coax along the bed of the truck and up to the radio inside the cab, my SWR is again off the scale. I've checked that there aren't any shorts in the coax and that the mount is properly grounded.

I understand that a fiberglass camper shell makes a poor ground plane, but since the antenna is only about a foot from the cab and four feet from the bed - shouldn't this suffice? How would I properly RF ground the mount? How did I get such a low SWR before I permanently installed the coax?
 

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I think your ground is still bad, maybe up the guage of wire on the ground. or you may also have some sort of power feed over to it that is causing your problem. I would douable check everything again. yes the shell isn't the best place for it but I would think if it was grounded by a wire than you should be good.
 

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Discussion Starter · #3 ·
That's what I thought, too. I actually tried running another 12 awg ground wire, and it didn't do anything. I'm starting to doubt that the problem deals with the actual DC grounding of the mount. I think the antenna doesn't electrically "see" the metal of the cab, but I'm no electrician...
 

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You could try a "NO GROUND" antenna. These come in handy when you have fiberglass or compsite material as a mounting surface.
 

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Make sure you have the mount installed right. I had mine put together wrong and my radio wouldn't tune until I fixed it.
 

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Here is a link to everything you will ever need to know about CB antennas and then some. http://www.firestik.com/Tech_Docs.htm

I suggest you read it or at least thumb through the relevant topics. Your situation will be in there somewhere. Then go buy yourself an SWR meter if you don't already have one.
 

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Discussion Starter · #7 ·
You could try a "NO GROUND" antenna. These come in handy when you have fiberglass or compsite material as a mounting surface.
Yeah, I know, but I was hoping that I wouldn't have to do that. I plan on using the CB for long-distance talk while travelling on the interstate, not so much for trail rides or anything, so I'd like the antenna to be as efficient as possible.

Make sure you have the mount installed right. I had mine put together wrong and my radio wouldn't tune until I fixed it.
Tracking down a problem like that is no fun. I'm pretty sure I have my mount installed properly - its just four screws.
 

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Discussion Starter · #8 ·
Thanks, Dick. I'm going to spend some quality time at that site.
 

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Yeah, I know, but I was hoping that I wouldn't have to do that. I plan on using the CB for long-distance talk while travelling on the interstate, not so much for trail rides or anything, so I'd like the antenna to be as efficient as possible.
Your best bet will be to have your unit and antanna tweaked and peaked my a pro.
 

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I plan on using the CB for long-distance talk while travelling on the interstate, not so much for trail rides or anything, so I'd like the antenna to be as efficient as possible.

Ground is one thing. Ground PLANE is another. Fiberglass doesn't make for a good ground plane....if you put 3 AWG#2 wires, makes no diff.. the antenna is the point of focus that the signal RADIATES off of, along the GROUND PLANE, and off to a receiver in the distance. A capacitively coupled antenna will also work, these are also known as magnet mount antenna's, they find the ground plane of the sheet metal under the antenna through capacitive coupling; not as completely efficient as a through-hole mount, but far better than your fiberglass situation. If you want to get cute, on the inside of the roof of the camper shell, put a nice piece of FLAT sheet metal, and mount the antenna through it, making sure the antenna mount ground is contacting the metal on the inside of or on top of the roof....and also grounded to the vehicle ground. Other than that if you want a really good and efficient antenna setup, you're a gonna have to poke a hole in the perfect ground plane on your truck...it's roof. RF signals are nothing at all like electrical signals, it isn't about this wire connected to that wire, it's about the RF path for the signal to propagate...and for an efficient system, a flat metal surface is what you're looking for....otherwise, you'll get a directional signal...truckers with twin antenna's on the cab mirrors have a directional signal in front and in back of them, sure there's other side-signals coming off the antenna's, but the STRONG signals are fore and aft... GOOD LUCK!
 

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Better than listening to what ever you may get here for advice.
As you will find if you don't want to use the top of your cab they have an antenna for your needs. The only caviet with that type is not to ever change the length of the coax. Others you can but not that type.
 

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Loud and Clear...

I listen to the radio often whenver I drive my 98' Toyota Tacoma to work. What really bothers me is whenever I drive my car into a basement of a tenement or went under a tunnel, I always lost radio signal. I'm really curious of the effectivity of a Toyota Antenna Mast since I really plan to get one soon. Do you think it would suit the purpose? :welder:
 

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I listen to the radio often whenver I drive my 98' Toyota Tacoma to work. What really bothers me is whenever I drive my car into a basement of a tenement or went under a tunnel, I always lost radio signal. I'm really curious of the effectivity of a Toyota Antenna Mast since I really plan to get one soon. Do you think it would suit the purpose? :welder:
:xofftopic :newbie:
Start your own thread!
:bitchslap :flamethro :slap:
 

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Discussion Starter · #14 ·
Thanks, Mr. Tacomi. I knew all along, before I started, that there would be serious ground plane issues. I had all the equipment lying around, though, so I thought it'd be worth a try. I wouldn't have continued with the installation if I hadn't read that really low SWR early in the process. I don't know what caused such a low reading; but I've sure as hell not been able to reproduce those results since.

Thanks!
 

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Thanks, Mr. Tacomi. I knew all along, before I started, that there would be serious ground plane issues. I had all the equipment lying around, though, so I thought it'd be worth a try. I wouldn't have continued with the installation if I hadn't read that really low SWR early in the process. I don't know what caused such a low reading; but I've sure as hell not been able to reproduce those results since.

Thanks!
In Microwave class, the instructor impressed one factor upon us... RF is the Voodoo in electronics... most everything else's behavior can be completely explained... with RF it's more like guidelines. When you had a really low SWR, it could have been the building, a bit of atmosphere, an intermittent short or open... ??? What my experience has taught me is that the 'known' basics will get you 95% of the way there are far as CB... I'm learning 2m/70cm voodoo now... we'll see :D Good Luck!

-Mark
 

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Maybe your instructor just doesn't understand RF very well. That would tend to cast some doubt as to his qualifications to be the instructor. LOL
 

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Discussion Starter · #17 ·
Hey, if you crack the 2m / 70cm voodoo, I'd like to hear it. Despite my obvious lack of understanding of electrical engineering, I'm an official, licensed radio amateur. I guess I've just always had good luck on the other cars that I've installed antennas on.

I've always planned on drilling a hole in the roof for an NMO dual-band antenna. I believe that someone makes an NMO CB antenna, too. Maybe I'll drill two holes.
 

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Maybe your instructor just doesn't understand RF very well. That would tend to cast some doubt as to his qualifications to be the instructor. LOL


Dick... you have no idea how right you are! ...but I did learn a lot from the ass despite his total lack of instructor skills, intolerance for humans, and down right bitter existence. I thoroughly loathed that particular experience..TWICE :eek:
 

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Hey, if you crack the 2m / 70cm voodoo, I'd like to hear it. Despite my obvious lack of understanding of electrical engineering, I'm an official, licensed radio amateur. I guess I've just always had good luck on the other cars that I've installed antennas on.

I've always planned on drilling a hole in the roof for an NMO dual-band antenna. I believe that someone makes an NMO CB antenna, too. Maybe I'll drill two holes.
Got my license some 3 months ago... pretty easily done.

I'm playing with my radio, has this APRS function, tied to my GPS it transmits my position, and finds folks nearby, and puts their position as waypoints on the GPS... pretty neat.

Drill? :eek: ..use an electrical punch...drill small hole, punch to the correct size.. perfect hole with no sheet metal distortions! My Tacoma came with this fancy retracting sunroof that uses the entire underside of the roof :rolleyes: but after the shakedown run where I was constantly putting the antenna's back on the roof, I'm a gonna investigate EVERY permanent mount solution!
 

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Discussion Starter · #20 ·
Punch, you say? We're getting a little off-topic on the thread, but I'm curious to see how well that works.
 
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