Cb antenna grounding question

[Robmills72]

I've looked everywhere and it seems like I'm the only person (or moron) that used a plastic tube mount (originally for a kc lamp) to mount my antenna. I've read that it usually cuts out most of the static to ground the antenna or antenna mount. How would do this since I have a plastic mount? Would I just run a little ground hoop from the stud to the frame?

Cheers

Edit: connected a ground strap from the antenna stud to the chassis of the truck and it went from having signal with a decent amount of background noise (but I could still hear truckers on ch 20) to having little background noise but I am not able to hear anybody. Did I ground it wrong? Do I need to buy a metal tube bracket instead of a plastic one or redneck inginuify one?

*i tested everything with the squelch knob on 0 so that is not a problem. Also my antenna has NOT been tuned yet, BUT that does not explain why I can get a signal ungrounded and lose the signal when grounded. Any help is appreciated, I'm just tired of hearing all the white noise (and not being able to hear the white trash LOL)

 

[GrantK]

I've looked everywhere and it seems like I'm the only person (or moron) that used a plastic tube mount (originally for a kc lamp) to mount my antenna. I've read that it usually cuts out most of the static to ground the antenna or antenna mount. How would do this since I have a plastic mount? Would I just run a little ground hoop from the stud to the frame?

Cheers

Edit: connected a ground strap from the antenna stud to the chassis of the truck and it went from having signal with a decent amount of background noise (but I could still hear truckers on ch 20) to having little background noise but I am not able to hear anybody. Did I ground it wrong? Do I need to buy a metal tube bracket instead of a plastic one or redneck inginuify one?

*i tested everything with the squelch knob on 0 so that is not a problem. Also my antenna has NOT been tuned yet, BUT that does not explain why I can get a signal ungrounded and lose the signal when grounded. Any help is appreciated, I'm just tired of hearing all the white noise (and not being able to hear the white trash LOL)

You don't say what type of CB antenna you're using but I'm guessing it has a standard 3/8 stud and that's it. If you grounded the stud and then transmitted you might have fried your radio. The antenna stud is the HOT lead that connects to the center conductor of the coax, that's why grounding it leaves you with no signal.

The shield of the coax is what you want grounded to the body. Ground it to the body as close the the antenna as possible. Keep the shield around the center conductor as close to the antenna as possible so it stays shielded but don't let the two (shield and center conductor) contact each other and don't let the center conductor or antenna stud touch the body (including mounting bolts that touch the stud).

If you didn't already fry your radio, you may see a reduction in engine related static, but not over the air static. You will almost certainly need to adjust your SWR as the new ground will change it. The ground will also improve your transmitted signal and may improve your receive signal (let you talk/hear further).

 

[Robmills72]

You don't say what type of CB antenna you're using but I'm guessing it has a standard 3/8 stud and that's it. If you grounded the stud and then transmitted you might have fried your radio. The antenna stud is the HOT lead that connects to the center conductor of the coax, that's why grounding it leaves you with no signal.

The shield of the coax is what you want grounded to the body. Ground it to the body as close the the antenna as possible. Keep the shield around the center conductor as close to the antenna as possible so it stays shielded but don't let the two (shield and center conductor) contact each other and don't let the center conductor or antenna stud touch the body (including mounting bolts that touch the stud).

If you didn't already fry your radio, you may see a reduction in engine related static, but not over the air static. You will almost certainly need to adjust your SWR as the new ground will change it. The ground will also improve your transmitted signal and may improve your receive signal (let you talk/hear further).

I was worried about frying my radio, it's just a little cheapie uniden, but my buddy has the same one and it works just fine. How would I ground the outer shield? That may be a stupid question but I'm also the idiot that had to by more coax to feed it through the fire wall because I thought I could butt splice it back together lol. I just took off the ground and I'm back in the same hole, signal but lots of white noise (just thankful it didn't fry my radio)

 

[fourwd1]

First off, what you're describing doesn't sound like a proper antenna mount.
Without the proper mount for the antenna you'll have problems.
Second, grounding. An antenna doesn't get grounded in the same sense as the radio does (ie to get -12V). The antenna needs a ground plane, an area of sheet metal that acts as the second half of the antenna. That is why the roof or trunk lid of a vehicle is the best place if you want maximum performance (although not the most popular for various reasons).
If you have an antenna mounted on the front bumper, even with the correct mount
, you're going to pick up engine noise and you don't have much of a ground plane.

 

[GrantK]

I was worried about frying my radio, it's just a little cheapie uniden, but my buddy has the same one and it works just fine. How would I ground the outer shield? That may be a stupid question but I'm also the idiot that had to by more coax to feed it through the fire wall because I thought I could butt splice it back together lol. I just took off the ground and I'm back in the same hole, signal but lots of white noise (just thankful it didn't fry my radio)

You still might have fried the transmit side of the radio, but don't test it until the antenna is squared away or even if it isn't currently fried you might fry it.

You should post some pics of the mount you created 'cause as fourwd1 said, without a proper mount you're system won't every work right. This doesn't mean you can't create a custom mount, just that's it's not as straight forward as mounting a light or winch and if not done right the radio can end up fried.

You've implied that you're in beyond your skill level and if so you might want to go to a CB shop or find someone locally that really knows their stuff when it comes to installing CBs and antennas so they can check everything out. As an example of things to know is that there are 3 types of grounds involved, a power ground (the black wire that goes to the negative side of the battery), a chassis ground (not all radios have one) which will be on the radio and needs to go to a ground point as close to the radio as possible and an antenna ground, also known as a signal or RF ground which is the shield on the coax and needs to go to ground as close to the antenna as possible.

You are right, you can't do a butt joint with coax. Even connecting to the PL259 needs to be done properly.

As to where to ground the coax shield, it needs to be as close to the antenna mount as possible. I'm going to guess that you are mounting the antenna on your ARB bumper (I took a quick look at your build thread). So connect the shield to the bumper. Also, you need a proper antenna spring at the base if you don't already have one.

 

[Robmills72]

You still might have fried the transmit side of the radio, but don't test it until the antenna is squared away or even if it isn't currently fried you might fry it.

You should post some pics of the mount you created 'cause as fourwd1 said, without a proper mount you're system won't every work right. This doesn't mean you can't create a custom mount, just that's it's not as straight forward as mounting a light or winch and if not done right the radio can end up fried.

You've implied that you're in beyond your skill level and if so you might want to go to a CB shop or find someone locally that really knows their stuff when it comes to installing CBs and antennas so they can check everything out. As an example of things to know is that there are 3 types of grounds involved, a power ground (the black wire that goes to the negative side of the battery), a chassis ground (not all radios have one) which will be on the radio and needs to go to a ground point as close to the radio as possible and an antenna ground, also known as a signal or RF ground which is the shield on the coax and needs to go to ground as close to the antenna as possible.

You are right, you can't do a butt joint with coax. Even connecting to the PL259 needs to be done properly.

As to where to ground the coax shield, it needs to be as close to the antenna mount as possible. I'm going to guess that you are mounting the antenna on your ARB bumper (I took a quick look at your build thread). So connect the shield to the bumper. Also, you need a proper antenna spring at the base if you don't already have one.

I got the spring, and yes the antenna is mounted on the bumper with a plastic kc tube mount. In theory would I strip the plastic cover, and sodder to the outer shield and then ground to the bumper.

Moving the antenna is an option but I like having the antenna on the front for various reasons, so if I can make it work I will

 

[GrantK]

If possible I would flip the mount around so the antenna is behind the top of the bull bar on the bumper. This will help protect the antenna and improve it's RF ground plane interaction.

For the ground, solder a ring terminal (from auto parts store or Radio
Shack) to it, then drill and tap a hole to screw the ring terminal to the bumper (maybe the angled support or tube) to fasten the ring terminal to. Remember to keep it close to the antenna. You should use a soldered ring terminal to connect the coax center conductor to the antenna's stud as well.

IMPORTANT: Pick up some silicone sealant and seal the center conductor, shield and where the outer cover of the coax is cut. Also seal the connections to the antenna stud and where you fasten the ground to the bumper. More is better than less in this case.

Don't forget to recheck your SWR!!!

 

[Robmills72]

Alright I'm seeing what I need to do now

Except:

You should use a soldered ring terminal to connect the coax center conductor to the antenna's stud as well.

I had the stud grounded before and it cut out all my signal. Isn't the stud connected to the center wire? Sorry like you said I'm in over my head, and the nearest cb shop is a good little drive away

 

[GrantK]

Alright I'm seeing what I need to do now

Except:

I had the stud grounded before and it cut out all my signal. Isn't the stud connected to the center wire? Sorry like you said I'm in over my head, and the nearest cb shop is a good little drive away

That's exactly what I said.

 

[Robmills72]

That's exactly what I said.

So why would I need to use a hoop to connect the center conductor to the stud, if it is connected by just being plugged in? Sorry if I'm being redundant, I'm definitely more of a visual learner

 

[GrantK]

So why would I need to use a hoop to connect the center conductor to the stud, if it is connected by just being plugged in? Sorry if I'm being redundant, I'm definitely more of a visual learner

How is it plugged in? A stud doesn't have any plugs on it.

 

[fourwd1]

You need to post some clearer, closer pics.

also, I'm going to move this to the proper section.

 

[Robmills72]

How is it plugged in? A stud doesn't have any plugs on it.

Just got the chance to snap a better pic, sorry haven't been with the truck all day

 

[GrantK]

I still don't see a plug but the point of th e ring terminal is to make sure you have a good solid connection between the center conductor and the stud. If what you're using provides that, you should be fine.

 

[fourwd1]

It looks like the coax is connected to the antenna mount using a standard PL-259 connector.
OP, is that correct?

 

[fourwd1]

I just realized what you're talking about now that I can see the new pic on something bigger than my phone. Your plastic bar mount is the problem, it is isolating the "ground" side of the antenna from ground. Basically you need to ground the outer shell of that coax connector, not the spring/nut on top.