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Old 02-08-2014, 04:21 PM   #1
Piz
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CB Antenna Mounting Questions

Hello all! First post here after creeping around for awhile. Got a hold of my first Jeep a few months back and it has been all love.

I'm working on a clean CB install. Currently have the Uniden 520 with a 3 ft. Firestik antenna and the Firestik 3-way mounting kit.

The radio is directly powered by the battery and I am running the coaxial cable underneath my slush mats, through the swing gate vent, and on to the 3-way mount secured by the spare tire mount.

Here are some pictures (a bit snowy, so I tried adding nifty arrows and text):





In the first one, you can see the set up. I have the black bolt from the spare tire mount securing both the spare tire mount and the 3-way antenna mount.

The second one has a bunch going on:
-Does the 3-way antenna mount need to be sanded on one side or the other? I've read about people sanding down the powder coating, but I'm not sure if this mount requires that. How do I know?
-I need to ground the antenna to get it working/find the right SWR. Will running a ground through the black bolt (bottom-right arrow) be sufficient? Should the ground be between the black bolt and the tire mount, the tire mount and 3-way antenna mount, or the 3-way antenna mount and the swing gate? Any suggestions for where to complete the ground (I've read it should be as short as possible)?
-Finally, will my antenna/coax/CB be effected by leaving the metal exposed to the elements? Should everything be wrapped in electrical tape?

I know I'm throwing a lot at you guys and I appreciate any help you can offer. Thanks!

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Old 02-08-2014, 05:28 PM   #2
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Welcome I'm no expert but while setting up my CB and learned that you really NEED a voltammeter to determine if it is properly grounded. That is the only technical way to know. The ground wire should "bolt" to metal/steel [the frame or exposed roll bar]. I do not believe the door tailgate is properly grounded because it "swings" on hinges.

Technically "shaving" the paint "should" ground better for the mount but the final ground cable needs to be grounded to solid metal. [I hope that makes sense]. The Jeep tire carrier is "plastic" with bolts to a "metal?" / "steel" .

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As the above picture shows.

Once you created a proper ground and the voltammeter confirms this , then use the SWR to "tune" the firestick and moving the top tip up or down.

Then you can say its technically properly configured

WARNING: Technically everything "will" work if it is NOT grounded properly and not SWR. BUT, you can damage stuff and have crappy reception hence negating the purchase of an expensive cb and firestick

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Old 02-09-2014, 03:45 AM   #3
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I had to run a ground from the tire mount, through the tailgate and into the rear cargo area in order to get my SWR readings down into the 1.2 to 1.4 range. The tailgate hinges have some type of bushing that won't allow for a good "bond" to the frame.
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Old 02-09-2014, 08:11 AM   #4
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Measuring SWR
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Old 02-09-2014, 08:21 AM   #5
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Thank you all for the fast responses.

Seg, great information, but even some of that is over my head and confusing. If you're well-read on this, mind taking a look at my questions and seeing if you know the specifics for my scenario?

47, I'll likely ground it to where you suggested. I'm only curious if that ground is too long. Everything I read says it needs to be as short as possible.

Jaxs, thank you. I'll grab a voltmeter one of the next couple days.

Quote:
-Does the 3-way antenna mount need to be sanded on one side or the other? I've read about people sanding down the powder coating, but I'm not sure if this mount requires that. How do I know?
Am I shaving from the antenna mount or from the tire mount? I now know where the ground wire will end, but not where it needs to start. Jaxs mentioned metal/steel, so would starting the wire in between the swing gate and the antenna mount be the best option? (But the hinges on the swing gate ruins the ground, so where the heck do I start this thing?)

Quote:
-Finally, will my antenna/coax/CB be effected by leaving the metal exposed to the elements? Should everything be wrapped in electrical tape?
Once I get the ground and situated, can I leave everything exposed or should it be covered up? I've seen both online so it seems like a personal preference.
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Old 02-09-2014, 10:03 AM   #6
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Here's how I ran my bonding strap.
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Old 02-10-2014, 09:34 AM   #7
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OK cool! Looks good.

So, specifically...what/where should be sanded down and where do I begin the ground?

Also..wondering if I need to wrap it all up in electrical tape or if it doesn't matter that the antenna connections are exposed.


Thanks again!
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Old 02-11-2014, 02:36 AM   #8
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You don't need to wrap tape around the mount. You'll need to clean up at least one of the antenna mount holes for a good bond to the tailgate. As you can see from my 2nd picture, I started the bonding wire from the mount bolt and run the wire all the way through the tailgate into the rear cargo area and attached it to that strap tiedown. Use 20 gauge wire and make sure you leave enough slack for when you open the tailgate.
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Old 02-12-2014, 06:18 PM   #9
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OK--cool! Thanks.

Excuse my newbie-ness, but I'm still hung up on where to start the ground only because I have the antenna mount pinned between the spare tire mount (non-metal) and the chassis. Yours looks nice and easy because you have the antenna mount OUTSIDE of everything.

Do you see the predicament? How can I get this to work?
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Old 02-12-2014, 07:43 PM   #10
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You could just clean off the powder coat so you havea good ground from the mount to the spare tire mount. That way you have no extra wires and clean install.
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Old 02-12-2014, 08:48 PM   #11
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So if I scratch off powder coating on the non-metal spare tire mount, that'll work as a ground itself without any grounding wires?

😄
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Old 02-12-2014, 08:48 PM   #12
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Is it obvious I have no idea what I'm doing
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Old 02-15-2014, 10:34 AM   #13
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Looking to complete this today if anyone can assist.

Also, once I get it working, I'm going to create the ultimate noob guide to wiring a CB radio & antenna.
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Old 02-15-2014, 10:43 AM   #14
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Quote:
Originally Posted by Piz View Post
So if I scratch off powder coating on the non-metal spare tire mount, that'll work as a ground itself without any grounding wires?

��
I installed mine and my buddy installed his yesterday and while the install of the radio and antennas were fast the tuning took hours. We tried everything and had troubles getting the swr dialed in. We both have Firestick firefly antennas and this is what finally worked and man did it work.. SWR down to under 1 on all channels. We tried grounding like the above photo to the tie down bolt did not get under 2 no matter how the fire stick was adjusted. We tried every possible adjustment from min to max. finally did this and bang both instantly under 1 with the min adjustment on the fire fly ie screwed all the way in.
ran the jumper to the top torx screw on the door hinge stopper and to the top side of the antenna above the nylon washer. Tried under and it did not work. had to be on top.
Need to come up with a way to hold my antenna down as it does not fit in the garage and coming in knocks the cap off. have it removed with a rubber plug in the threads until I actually need it.



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Old 02-15-2014, 12:48 PM   #15
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PLEASE Do Not transmit on your radio until you remove this wire. What it looks like you have done by what you have said and the pictures you posted is ground your antenna.

Let me clarify grounding the antenna, you have essentially grounded the center pin of your coax rather than grounding a tuning stub that is manufactured into some antenna designs such as the Wilson Silver Load series. This is a very bad thing to do and will result, without a miracle, in severe damage to your radio.

Grounding the tuning stub that is manufactured into an antenna is perfectly safe, they are engineered to be a certain electrical length and load to the antenna system so as to look "invisible" to the radio and give your radio a better load closer to the 50 ohm impedance that it is looking for to be happy and live a long life. You might have gotten very very lucky and hit that perfect length on your first try. If you did I bow to your luck.

I would take your trucks to a CB shop that is respected in your area and have them check out your setup, or while a little more expensive probably better, find a two way radio shop and see if they will take a look at your setup and help you out with your tuning.

Again I would not transmit on your radios until you double check your systems as from what I see you have grounded your antenna and could severely damage your radios. 18 years of working in the two way radio field and designing countless radio systems for public safety groups is giving you this suggestion to double check what you are doing.

Lunatic Fridge

Quote:
Originally Posted by jadmt View Post
I installed mine and my buddy installed his yesterday and while the install of the radio and antennas were fast the tuning took hours. We tried everything and had troubles getting the swr dialed in. We both have Firestick firefly antennas and this is what finally worked and man did it work.. SWR down to under 1 on all channels. We tried grounding like the above photo to the tie down bolt did not get under 2 no matter how the fire stick was adjusted. We tried every possible adjustment from min to max. finally did this and bang both instantly under 1 with the min adjustment on the fire fly ie screwed all the way in.
ran the jumper to the top torx screw on the door hinge stopper and to the top side of the antenna above the nylon washer. Tried under and it did not work. had to be on top.
Need to come up with a way to hold my antenna down as it does not fit in the garage and coming in knocks the cap off. have it removed with a rubber plug in the threads until I actually need it.



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Old 02-15-2014, 01:17 PM   #16
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Quote:
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So if I scratch off powder coating on the non-metal spare tire mount, that'll work as a ground itself without any grounding wires?

��
Where you would want to take the paint or powder coating off at is on the bracket that your antenna mount is on. I do not use painted or powder coated antenna brackets personally. But they are fine if that is what you want to use.

What you will want to do is on the bracket where the mounting stud for the antenna passes thru the bracket you will clean off the paint or powder coating on the bottom side of the bracket so that the mounting stud makes good contact with the metal of the outer ring of the bottom piece of the antenna stud. Here is a picture of the mounting stud I am talking about taken apart. The outer silver ring on the base portion on the right is what you want to make good contact with the mount that you are using.



Then you want to clean off the paint on the mounting bracket around the mounting bolt that you are going to run your ground strap from to the body of the vehicle. Then at the vehicle end of the grounding strap (I would go to the tub rather than to the rear hatch for this location. There are a number of bolts just inside the rear hatch door that you can use) clean off the paint and attach the ground strap there.

For the ground strap, minimum that I would use for a CB installation is 12ga fine stranded wire. The more strands in the wire the better. RF travels along the surface of the wire so the size I am recommending is not based on its current handling or wattage of the radio that you are using to transmit with but more for its RF properties. When I ground things I use a 1 inch wide braided strap. But I am usually grounding antenna mounts that see a lot more power legally and a lot more frequency range than what you are doing.

Once you do that and get the rest of your stuff installed get it tuned up so you dont damage your radio. If you do not have an SWR meter find someone locally that does or a CB shop in your area to get it done.

I'll try to be around if you have more questions but my access to internet for the next 5 days is going to be a bit spotty.

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Old 02-15-2014, 02:15 PM   #17
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Quote:
Originally Posted by Lunatic_Fridge View Post
PLEASE Do Not transmit on your radio until you remove this wire. What it looks like you have done by what you have said and the pictures you posted is ground your antenna.

Let me clarify grounding the antenna, you have essentially grounded the center pin of your coax rather than grounding a tuning stub that is manufactured into some antenna designs such as the Wilson Silver Load series. This is a very bad thing to do and will result, without a miracle, in severe damage to your radio.

Grounding the tuning stub that is manufactured into an antenna is perfectly safe, they are engineered to be a certain electrical length and load to the antenna system so as to look "invisible" to the radio and give your radio a better load closer to the 50 ohm impedance that it is looking for to be happy and live a long life. You might have gotten very very lucky and hit that perfect length on your first try. If you did I bow to your luck.

I would take your trucks to a CB shop that is respected in your area and have them check out your setup, or while a little more expensive probably better, find a two way radio shop and see if they will take a look at your setup and help you out with your tuning.

Again I would not transmit on your radios until you double check your systems as from what I see you have grounded your antenna and could severely damage your radios. 18 years of working in the two way radio field and designing countless radio systems for public safety groups is giving you this suggestion to double check what you are doing.

Lunatic Fridge
thanks I wonder if mods can delete so some one does not get messed up. thanks jeff
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Old 02-15-2014, 03:05 PM   #18
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I removed the jumper and was able to get both 1 and 40 to 1.7's middle channels are lower and 20 is 1.1. It started off after removing the jumper that 1 was around 3 and 40 was around 1. As I adjusted the antenna screw (on fire fly) I got 1 and 40 nearly the same at 1.7. Does this make sense that the middle channels would be lower? thanks
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Old 02-15-2014, 05:00 PM   #19
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I removed the jumper and was able to get both 1 and 40 to 1.7's middle channels are lower and 20 is 1.1. It started off after removing the jumper that 1 was around 3 and 40 was around 1. As I adjusted the antenna screw (on fire fly) I got 1 and 40 nearly the same at 1.7. Does this make sense that the middle channels would be lower? thanks
1.7 is plenty good. Anything under 2 at ch 1 and 40 with a dip around ch 20 will give you an ok working radio system but wont cause any harm to the radio itself. Anything over 2 and its time to start looking for the causes and get things back to happy.

Why the middle is lower than the edges is due to the bandwidth of the antenna. All antennas are tuned to a resonant frequency. In your case ch 20 which is 1.1 to 1. All antennas will have based on their design a given bandwidth, this is all the engineering that goes into the antennas and if it is built with tuning stubs and multiple electrical wavelengths in a configuration they can provide either a very narrow bandwidth or some have a very wide bandwidth. Bandwidth is usually defined as the usable frequency range of the antenna based on a certain match limit. Like your Ch1 and Ch40 being at 2.0 to 1. So it could be said that your antenna has a 2.0 to one bandwidth of 440KHz (Kilo Hertz). I am sure if I were to put my antenna analyzer on it we would find that it is actually a bandwidth of 500KHz but your radio can not legally go beyond Ch 1 and 40 which is a spread of 440KHz. 500 KHz is pretty common for CB antennas and general 1/4 wave whip antenna designs.

Now, this bandwidth is tested and stated based on a perfect world setting. So it does not guarantee anything for a match. Just tells you what you could expect to see if you had everything exactly like the manufacture did in their test labs and all that good jazz. So dont go look up your antenna and think you are getting jipped or anything if it happens to say a 1.5 to 1 bandwidth is XYZ or something like that.

If you want to know lots more about how your antenna works search around on the internet for Amateur Radio Vertical HF Antenna Design and Theory. That should get you all kinds of info.

Glad you got things going with your Radios.

Lunatic Fridge

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