CB Antenna Mounting - Grounded?

[JeepMonkey]

So I'm about to mount my antenna this weekend and I'm planning to put it on the swing out tire carrier. My questions are:

1. Does the antenna itself need to be grounded? I believe it does....I could be wrong though.
2. The swing out tire carrier is connected to the bumper via a large hinge pin that is greased.....Will this interfere with the grounding process? I think it will....I could be wrong again though.

I appreciate all opinions and would love to get the facts!

thanks!

 

[RangerRick]

It would be best to mount your CB antenna to the body of the Jeep for ideal grounding. Many CJ/YJ/TJ owners use those behind the tail light brackets Example Here that comes with the antenna and cable: Link (if you get one, get it in stainless if you live in the rust belt), which provide a good body ground for RF. You remove the tail light box and attach the bracket using the three screws holding your tail lamp box to the tub and clamp with a large surface area next to the body providing a good RF ground path. RF grounding is different than electrical ground for wiring. RF needs surface area because RF currents are carried on the surface like skin effect so this is why the body of the Jeep makes the best grounding rather than tire carriers etc. On Cherokees and other metal roof Jeeps, the center of the roof makes the best ground spot on the entire vehicle. Next best would be the hood area or the tail lamp area because our Jeeps frequently have fiberglass, plastic or a vinyl soft top it is harder to get a good spot for RF radio antennas. Even if the back swing-out carrier is electrically grounded on your Jeep, it is not ideal for RF due to it's small surface area. Even if you were to tune your antenna to work there, it will not have as powerful signal as if the antenna were mounted to the body tub itself. Food for thought, there are lots of publications by the ARRL (American Radio Relay League, also good if you have any interest in getting a ham license), Ham radio's premiere international organization you can read about in their "Antenna Handbook" and other papers published in the field of radio that go into great technical detail you probably don't need to know most of. Search "ARRL ANTENNA HANDBOOK" or "HF ANTENNA THEORY" for more information on how antennas work.

RangerRick

 

[JPNinPA]

The swing arm is popular and the hinge is an issue as you pointed out. If you choose the swing arm get a good multi strand ground strap to ground the swing arm or the antenna mounting plate/surface.

The antenna itself does not get grounded. The outer shield of the wire should be grounded at the base of the antenna.


Visit firestick tech docs to understand more. Or ask more questions. Either way there are three -four big steps.
Noise free radio power. Battery is best.
Assemble the antenna properly
Verify continuity and grounds
Tune antenna for lowest SWR reading on ch19.


http://www.firestik.com/Tech_Docs.htm

 

[JeepMonkey]

Thanks for the info! I would've used the "behind the light" mounting bracket if I still had my lights. I've got 4" LED's now. The grounding strap is the conclusion I came up with too. Thanks again!

 

[JPNinPA]

To clarify. If your antenna has a little pigtail DONOT ground it. The outer shield of the cable is to be grounded at the antenna stud on the mounting surface.

The center conductor of the cable connect to the antenna and is not grounded. The antenna terminates in the air or to the tuning tip.

 

[RangerRick]

Id still recommend against a swing-out mounted CB antenna again, due to RF grounding potential. Best use of the swing-out mount antenna tab is for your sand dune flag pole mounting because you will not get a good enough RF ground using braided strap due to the skin effect of RF. Better to mount on the body tub where the entire Jeep is bonded and grounded well enough for RF.

Thanks for the info! I would've used the "behind the light" mounting bracket if I still had my lights. I've got 4" LED's now. The grounding strap is the conclusion I came up with too. Thanks again!

If you have armored corners, weld a tab to the edge of the tub on the armored corner above your tail light area with a hole in it for the 3/8"x24 thread stud mount. This tab should be about 1 1/4" wide with the hole in it and be about 2 1/2" long to keep your antenna base away from the Jeep tub by a couple inches. Your entire corner armor and tub will become your grounding point for the antenna. This is the way you should do it if you have LED flush mount tail lights and cannot use the behind light mount bolt on tab kit. You will get the best grounding at this point and it will be out of the way of trees, bushes and getting stuff from the tail gate area.

Oh and BTW, use quality coax such as RG-8X mini foam or double shielded RG-223/U for minimal losses and flexibility. Never use solid center conductor RG-58 because any flexing of the cable can cause the center conductor to break and the shielding is horrible with high losses @ 27 MHz. When every .10 of a Watt counts, don't skimp on the coax cable.

RR

 

[JeepMonkey]

If you have armored corners, weld a tab to the edge of the tub on the armored corner above your tail light area with a hole in it for the 3/8"x24 thread stud mount. This tab should be about 1 1/4" wide with the hole in it and be about 2 1/2" long to keep your antenna base away from the Jeep tub by a couple inches. Your entire corner armor and tub will become your grounding point for the antenna. This is the way you should do it if you have LED flush mount tail lights and cannot use the behind light mount bolt on tab kit. You will get the best grounding at this point and it will be out of the way of trees, bushes and getting stuff from the tail gate area.
RR

I have diamond plate corners, however, they were painted before I riveted them to the Jeep and I ran a bead of silicone around the edges and across the interior of the corner to protect against rusting. I'm not sure that corner will be a good ground point for anything.

If all else fails I will mount it to the bumper, just below the rear body corner. The only thing that concerns me here is a rumor I once heard about having the base of your antenna mounted at the same height as the top of the tub. Anyone able to debunk that myth?

 

[JeepMonkey]

And the antenna cable is exactly the kind you said not to get......Though it was free when I got the radio so I'll use it for now and upgrade later. I've only had this CB sitting in my garage for about 8yrs....every year I say "this is the year I finally mount my radio and stop using handhelds!"

 

[JPNinPA]

There is little truth to the myth you state. Thinking ideal, the best spot for an antenna is over the center of vehicle with a thick iron roof. This will produce the best radial transmission. A jeep is not built like that, so you have to trade off one thing for another. When you change the position the pattern changes. Truckers take advantage of this and mount antenna on the driver side so they could keep good communication with the oncoming traffic.

Also if anything is close to the load section or enough of the length if the antenna the signal bounces back as returned power. This is one reason for high SWR. High reflected power over time will damage the antenna, cable and radio. Immediate reaction is modern radios recognize high SWR and limit output to not harm the radio so limited transmission will occurs.
Things like too close to the antenna like a high jack, modified roll cage metal roof or within 2 in of hard top will cause issues. However there are many many keepers that have their 3 ft antenna below the roof off the rear tail light mount.

 

[JPNinPA]

2x on the multi stranded mini 8.

Alternative mounts that will require drilling and can transfer the ground connection to the inside of the tub.

 

[Utah_jeepster]

As you can see I have my antenna attached to my swing arm. Just go to your local truck stop and you can find a groung ring and wire for your antenna base. Just ran the wire to the jeep body.

 

[JeepMonkey]

View attachment 19592


As you can see I have my antenna attached to my swing arm. Just go to your local truck stop and you can find a groung ring and wire for your antenna base. Just ran the wire to the jeep body.

Thanks....it looks like your jeep is the same color as mine in that pic....dark red metallic?

 

[RangerRick]

Id still weld a tab to your corner guard above the tail lamp for best results and not mount your antenna low down on the bumper. Bumper mounted antennas on a Jeep are the worst radiating locations possible second only to a hand held unit with a rubber duck inside the passenger compartment FWIW. There is too much metal and too low to the ground cause large radiation efficiency losses due to earth proximity coupling.

RangerRick

 

[Jeepergeo]

Behind the tail light on TJs works great. But, just make sure you use those star washers that dig in so that you get a good ground, or run a dedicated frame to antenna mount ground wire.

Yeah, on the swing arm, a dedicated ground wire would ensure the best and most consistent ground.

 

[JPNinPA]

How did it go? Post a in focus of the antenna mount showing the cable, mount and antenna base. ESP if you run into issues. Also post the SWR readings you settle on.

 

[JeepMonkey]

I haven't had a chance to mount it yet. Hopefully I'll have most of tomorrow to work on it.

 

[Utah_jeepster]

Thanks....it looks like your jeep is the same color as mine in that pic....dark red metallic?

actually mine is called burnt amber.
I have since removed the antenna off the tail light area because it was causing problems with my ORO round tail lights. it flexed enough to break the circuit board inside.

 

[JeepMonkey]

I got everything mounted late last night and hooked up the SWR. Without any tuning I got 1.5 on the meter set to channel 20. I'm going to do a little fine tuning tonight and see what I can come up with. The weather channel worked fine and I heard conversations from the highway a few miles away. I think it should work just fine on the trail with only 20ft between vehicles. thanks for the help!

 

[JPNinPA]

I got everything mounted late last night and hooked up the SWR. Without any tuning I got 1.5 on the meter set to channel 20. I'm going to do a little fine tuning tonight and see what I can come up with. The weather channel worked fine and I heard conversations from the highway a few miles away. I think it should work just fine on the trail with only 20ft between vehicles. thanks for the help!

The 1.5 SWR, was that off of the radio meter or an external?

 

[JeepMonkey]

It was an external. It came with the Uniden 510 I won on this site a few years ago. Is one more accurate then the other (he asked afraid of the responses sure to come) ?