Can you mount a cb antenna to plastic?

[76k5blazerr]

My buddy has a 93 fj80 and he's wondering if he can mount a cb antenna to his rear bumper which is plastic. I don't know if this would work because I've never tried it, but I think it would work if he ran a nice thick ground wire from the mount to the frame. Thoughts?

 

[Blue85]

Yes, if you use a metal mounting bracket and achieve a good RF ground to the body it will still work. Using a wide braid works much better than a wire. That ground connection needs to be pretty short, though. I'm not sure I would trust plastic for mechanical strength reasons, though.

 

[diesel4me]

You do need the ground for a "ground plane" in order for most antennas to work right...some designed for fiberglass mounting on boats need no ground plane,but they don't perform quite as well as the usual ones really..

I would think as long as it is grounded good it'll work OK,but I'd check the SWR ratio right away and see if its above 3:1,if so,I wouldn't transmit with it till you can get it lower than that..

 

[Russell]

You'll need a non ground plane type antenna for that. They have a resistor built in to simulate a ground plane. The gain isn't as good but they still work nicely.

 

[76k5blazerr]

So I'm getting mixed answers here... He wants to run a gumdrop stud mount with a spring and a 102 whip off his rear bumper. Would this work with a ground wire or not?

 

[4xcrazy]

ah yes, the 102" stainless whip,, back to the 80's,,,

SO much better quality antennas out there other than the overly intrusive 102" whip.

BTW, I ran an antenna on the drivers side rear bumper, corner on the side, I kept ripping it off on the trails. I didn't think it'd be that vulnerable there, I was wrong.

I now have a nice strong K-40 magnet mount on the roof centered, it also transmits and receives SO MUCH better on the roof, it really sucked on that rear corner.

 

[76k5blazerr]

I love the 102 on my k5, mounted to left rear bumper, looks almost factory on this old truck. Only antenna I would run on a truck from the 70s. It talks 10 miles on a good day.

 

[Russell]

I love the 102 on my k5, mounted to left rear bumper, looks almost factory on this old truck. Only antenna I would run on a truck from the 70s. It talks 10 miles on a good day.

I have a Larsen steel whip on my Tahoe. It's mounted directly above the tail light on the side of the truck. Rx/Tx there is decent, SWRs are good with the whole box side to use as a ground plane. It'd be a lot better for range on the roof but I'd rip it off wayyyy more often than I do where it is just because of all the low lying branches I have scraping across the top of my truck all the time (I swear I have more pin striping on the roof than the quarter panels...).

If the bumper is steel you can definitely give it a try. You'll loose some gain without a big ground plane to act as the other end of the dipole but as long as your SWRs are within spec you should be alright. The non-ground plane antennas are a center loaded dipole, aka the center of the antenna is where the zero line is on the wavelength vs the bottom of the antenna. It then uses the top half of the whip for the positive side and the bottom half for the negative side. A regular ground plane antenna is bottom loaded and uses the whip for the positive side and the bottom half is your metal surface.

 

[sweetk30]

those plastic bumpers on newer stuff are thin and brittle to begin with . and then add in cold temps and BANG / SNAP the cold pops the plastic .

mount it better and as said skip the whip . there is much better stuff .

lots of jeep guys have made nice custom brakets and sell them that bolt on the body in factory spots . I would look in to this also for a mount.

 

[diesel4me]

I ran the 108" stainless whips and springs on my '72 K5,then someone gave me a used "Firestick" antenna only 4' long..once it was adjusted to the lowest SWR I could get, about 1.5 to 1,by simply turning a threaded stud at the top that had a locknut,I found I could reach much further with that antenna than the steel whips would,and no more banging the whip on everything..

I doubt an 8' whip would stay on a plastic bumper long,even if you used metal back up plates..they put a lot of force on the mount,I have had them crack sheet metal after awhile..

 

[Blue85]

SO much better quality antennas out there other than the overly intrusive 102" whip.

It's impossible to make a shorter antenna work as well as a real 1/4-wave. It's also pretty hard to make something more durable than stainless spring steel. However, things aren't always equal because of mounting. Putting a coil-loaded antenna on the center of your roof will probably perform better than the giant whip on the rear bumper. Now if you mounted the giant whip on the center of your roof, it would be the ultimate performance, but I don't know who could live with it on a lifted/off-road truck.

Also, putting the antenna on the back bumper makes the whole thing directional, especially since it will probably end up on the corner to clear the tail/lift-gate. Add a ground "strapped in" ground instead of direct mounting to the sheet metal and it's probably not going to perform that well. Plus, the lowest parts of the whip are the most "radiating" and those are the portions blocked by the vehicle body.

If you do want a mount on the bumper, don't mount to plastic. Build some kind of steel brace underneath that takes the load while just looking like the antenna is mounted to the bumper cover. You would probably still want to ground strap it back to the body of the vehicle, unless it's clear that the bumper structure is welded to the body or frame.

With CB antennas you have to pick your poison and figure out what is the least terrible for the application.