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 Post subject: Easy On / Easy Off crossbar CB antenna mount for your roof
PostPosted: Tue Mar 24, 2009 12:15 am 
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A while ago I said that I was going to fab up a crossbar CB antenna mount that could be easily installed and removed for trail rides. Someone mentioned that if I did I should do a write up on it.
Here you go:

(No comments about how dirty my Liberty is :oops:)

Note: unless you are running a non-ground plane system, you will need to run a ground wire from the antenna stud, through the cross bar and ground it to the body somewhere.

First things first; you will need the following materials:

1 – Four foot long by 1” square length of aluminum tubing
2 – ¾” PVC conduit straps
1 – multi-mount CB antenna mount
18 feet of coax cable
4 – ¼”-20 X 2” hex head bolts (I chose to use stainless)
4 - ¼” split lock washers (I used stainless) (I think internal tooth washers would work well also)
4 - ¼”-20 wing nuts (I used stainless again). I chose wing nuts because they hit the conduit strap when you tighten the hex bolt from the top of the cross bar; thereby necessitating only one end wrench or socket wrench to install it.
4 - #8 X ¾” sheet metal screws (sharps work best; they have a pan head and don’t require pilot holes to be drilled)

You will obviously need a CB as well for this. I use a Midland model 75-822. It has all power of a “box” unit but all the controls are built into the mic. You can also run I with the “duck” antenna and batteries (although the range drops below a mile in this configuration, it is still great for spotting or giving trail instructions to a group that is gathered close by). I get about a 5 - 10 mile range with this current set up and so far it seems trail worthy (time will tell). Here’s a link if anyone is interested.
http://www.amazon.com/MIDLAND-75-822-Channel-Way-Radio/dp/B00000K2YR


On with the build!

Start by finding the center of the bar and marking it.

Image


Next measure the distance between the side rails on the roof rack. Then find where the rails would be in relation to the bar by dividing the total distance between the rails in half and measuring that distance from the center point in the bar. This should be the same distance from each end; so that once attached, the bar will be centered on the Jeep and the antenna will be centered on the bar (I’m a bit OCD when it comes to stuff like this).

These side marks are the centers for the conduit straps. The PVC straps are not precision made so just use them as a template to mark where you will drill your holes for the mounting bolts. Before you drill the holes, rest the bar on your rails to make sure that the holes will be in the right place.

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If you have access to a drill press, use it. I don’t so I marked the holes on both sides of the cross bar and drilled 8 holes so that everything would line up nicely.

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(The screws shown in the pic below were used for alignment purposes only. I used hex head bolts to actually fasten it to the rail)
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Next I had to bend the antenna mount (the piece on the right in the pic) on a 90° angle so that it would wrap two sides of the bar. This part could be easily fabricated out of a scrap piece of steel plate. I just had this on hand already.

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Use the sharps to attach the antenna mount to the bar.

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Mount the antenna stud.

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Then mount the spring to the antenna mount (I waited to mount the antenna until I was sure everything was going to fit right because the cross bar is much easier to handle without it on there).

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Time for a “field fitment”.

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After pulling it outside (the lifted Jeep with the antenna mounted won’t fit in the garage without hitting the ceiling) I mounted the antenna and coax onto the bar and mounted it on the Jeep. It’s a tight fit for the coax fitting. I may get a 90° connector for it because there is not room for you to put to coax on after the crossbar is mounted.

I marked the top of my rails after determining the point where I would get the best ground plane and then tried it out. It worked great

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I run the coax across the roof,

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Across the lift gate gasket

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Along the wall on the driver’s side

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Under the back seat where I coil the excess cable and put it under the mat,

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And up to the driver’s seat.

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This build cost less than $20 and took about 2 hours to make. I had a lot of the hardware around the house. The ¾” PVC conduit straps fit the roof rails on the Liberty perfectly. I will see how strong they are over time. They are cheap so I have and extra set in my tool bag in case of failure. If there are problems with them, I will just use galvinized steel ones. They just don't fit as well.

Overall I am pretty happy with the way that it turned out. I am still looking for some square end caps for 1 inch tubing. I know I have seen them somewhere, but I don’t remember where it was now.

I hope someone finds this informative and perhaps useful.

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'06 Stone White, CRD Limited
CRD Frankenlift II, Rock Lizard Rear Bumper, Mann Provent, GDE FT-ECO Tune, "Euro Torque Converter, Transgo 545RFE-H2 Shift Kit, 245/75 MT/R's on Moabs, Full Mopar Skids, Front Tow Hooks, CAT 2 Fuel filter and bleeder valve mod, Fumoto valve, Wahlbro Lift Pump, Custom 2 1/2" Exhaust


Last edited by mrkake on Tue Mar 24, 2009 2:30 am, edited 2 times in total.

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 Post subject:
PostPosted: Tue Mar 24, 2009 12:41 am 
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Perfect write up. Nicely done.

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PostPosted: Tue Mar 24, 2009 1:32 am 
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I like it! Could even throw a WQD on it for if you wanted to snatch the antenna off real quick without removing the cross bar, i've really enjoyed that mount

hows your grounding and swr doing with it?

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03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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 Post subject:
PostPosted: Tue Mar 24, 2009 2:26 am 
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JeepinJarhead03 wrote:
I like it! Could even throw a WQD on it for if you wanted to snatch the antenna off real quick without removing the cross bar, i've really enjoyed that mount

hows your grounding and swr doing with it?


Thanks!

The ground isn't good. I was hoping that the aluminum would ground it sufficiently, but I have realized that the roof rails don't contact the body in any way. I thought that there was a metal framework inside the plastic covers but there must not be. I am going to have to run a ground wire to it. I am going to run it from one of the rails mounting bolts and run the wire inside the rail to where the cross bar sits. I will just put a spade connector on it and then run one from the antenna stud through the cross bar and out a hole with the matching connector on it. My SWR readings were pretty high, so I just used a wire with an alligator clip and grounded it to the body and they dropped significantly. I am still above 2.0 though so I need to tune the antenna as well.

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'06 Stone White, CRD Limited
CRD Frankenlift II, Rock Lizard Rear Bumper, Mann Provent, GDE FT-ECO Tune, "Euro Torque Converter, Transgo 545RFE-H2 Shift Kit, 245/75 MT/R's on Moabs, Full Mopar Skids, Front Tow Hooks, CAT 2 Fuel filter and bleeder valve mod, Fumoto valve, Wahlbro Lift Pump, Custom 2 1/2" Exhaust


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PostPosted: Tue Mar 24, 2009 8:33 am 
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Looks great!
The ony problem is that I have run my coax that way thru the back glass flipper... and I got 2-3 inches of water in the back after the first rainstorm.
Just food for thought.


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PostPosted: Tue Mar 24, 2009 12:32 pm 
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doesn't the nylon go between the coax stud and the mount instead of between the antenna coupler and the mount?

it wouldn't supprise me if I've been doing it wrong for 15-20 years :lol:

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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PostPosted: Tue Mar 24, 2009 3:44 pm 
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riptricket wrote:
Looks great!
The ony problem is that I have run my coax that way thru the back glass flipper... and I got 2-3 inches of water in the back after the first rainstorm.
Just food for thought.


Yea, I read your post about it, but I don't have much need to worry about rain in Vegas :D :shock: . We get about 6 inches of rain fall a year and that takes place in about 1 storms. I don't go off road around here if it's going to rain. There are flash floods every where. People die every year because they underestimate what Mother Nature is capable of throwing at them. Also, the remove-ability is the key factor here. I rarely off road more than once a month and that's the only time I use my CB. The rest of the time it will be hanging on my garage wall.

Thanks for the "heads up" though. If I lived in wetter climates I would definitely have to take that into consideration. What about running it over the gasket from the bottom? The window would work like flashing in that scenario.

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'06 Stone White, CRD Limited
CRD Frankenlift II, Rock Lizard Rear Bumper, Mann Provent, GDE FT-ECO Tune, "Euro Torque Converter, Transgo 545RFE-H2 Shift Kit, 245/75 MT/R's on Moabs, Full Mopar Skids, Front Tow Hooks, CAT 2 Fuel filter and bleeder valve mod, Fumoto valve, Wahlbro Lift Pump, Custom 2 1/2" Exhaust


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PostPosted: Tue Mar 24, 2009 3:49 pm 
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JeepinJarhead03 wrote:
doesn't the nylon go between the coax stud and the mount instead of between the antenna coupler and the mount?

it wouldn't supprise me if I've been doing it wrong for 15-20 years :lol:


It said on the mount's package that the nylon washer went between the antenna stud and the mount and the coax stud screws up against the mount. I'll be the first to admit that I don't have much experience with this stuff and I do want to get the best reception that I can so any suggestions are appreciated.

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'06 Stone White, CRD Limited
CRD Frankenlift II, Rock Lizard Rear Bumper, Mann Provent, GDE FT-ECO Tune, "Euro Torque Converter, Transgo 545RFE-H2 Shift Kit, 245/75 MT/R's on Moabs, Full Mopar Skids, Front Tow Hooks, CAT 2 Fuel filter and bleeder valve mod, Fumoto valve, Wahlbro Lift Pump, Custom 2 1/2" Exhaust


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PostPosted: Tue Mar 24, 2009 5:55 pm 
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tom or one of the ham fellas will chime in and shake their finger at one of us, and it'll probably be me for doin it wrong even though I get great results :lol:

for some reason it always made sense to me to protect the coax exit signal from grounding with the mount while grounding the antenna

I don't know :oops: I'll pm tom or somebody and ask, doesn't take 5 minutes to fix it if I had a "Slow" moment

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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PostPosted: Tue Mar 24, 2009 10:52 pm 
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I messasged tom and cdiekhans

apparently you've got it right! which is good for you!!

apparently I've got it wrong and either have been doing it wrong for years, Or... had a big brain fart at some point when mounting that antenna :P

I guess ill go disasemble and do tha dang thang :lol:

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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PostPosted: Wed Mar 25, 2009 12:23 am 
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JeepinJarhead03 wrote:
I messasged tom and cdiekhans

apparently you've got it right! which is good for you!!

apparently I've got it wrong and either have been doing it wrong for years, Or... had a big brain fart at some point when mounting that antenna :P

I guess ill go disasemble and do tha dang thang :lol:


It's good to know that it's assembled right. But now I am wondering; do I need to ground the antenna or the mount and coax? I am assuming it's the mount to protect the radio, but I'm feeling a little confused right now.

_________________
'06 Stone White, CRD Limited
CRD Frankenlift II, Rock Lizard Rear Bumper, Mann Provent, GDE FT-ECO Tune, "Euro Torque Converter, Transgo 545RFE-H2 Shift Kit, 245/75 MT/R's on Moabs, Full Mopar Skids, Front Tow Hooks, CAT 2 Fuel filter and bleeder valve mod, Fumoto valve, Wahlbro Lift Pump, Custom 2 1/2" Exhaust


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PostPosted: Wed Mar 25, 2009 1:19 am 
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Astatic shows their mounts with the nylon between the antenna and the mount, I had it backwards, I don't know how long i've been runnin it backwards either ... lol

i have been getting interference from like.. flashing caution lights and stuff

with my antenna's built in ground strap connected witht he nylon where it's SUPPOSED to be .. my SWR pegged

iwth the strap disconnected the SWR needed to be adjusted but was acceptable, I'll try a different ground location, it's possible the ground strap was feeding back through the mount causing the spiked SWR

i was getting some chatter so i was getting RX with the strap disconnected
the only thing thats keeping me from just cutting off or tieing up the strap is the Severe lack of static when I turned the squelch all the way back, if it is indeed RX'ing properly with the squelch back like that, then oh my friggin gawd.. i'm not sure how I delt with having to have my squelch at 60% to cut out the interference since the radios been in

I'll go to the river in new bern tomorrow and try a few ground locations and set the SWR and see how it does


It's pretty wierd, Cdiekhan had his nylon on the wrong side and couldnt TX over 20 feet

I'm not aware that i've really had any TX issues but it may have been using the ground strap as a jumper

I'm with you on the confused state..

like i told Cdiekhan, 'some assembly required' sucks :lol:

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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PostPosted: Thu Mar 26, 2009 12:30 am 
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I realized today what I had done, when I modified one of my old mounts i was using it upside down (intentionally) which made me think the nylon went on the bottom

So I ended up spending about 3 hours today tweaking my antenna again and trying to get my swr perfect like I wanted it

regrounded my antenna somewhere else away from the mount because I think the antenna ground was feeding through the mount, i opened the back door and pulled the top weather stripping back and pulled 2 screws out of the weather stripping lip and slid an connector behind it and put the screws back in and added disconnectable electrical connectors at the base of the antenna

I got a much better response using the built in antenna ground rather than using a ground strap on the mount itself

I ended up having to take out the tuneable tip and it's still too long, i tried 3 different coax studs and 4 different antenna couplers, I'm getting about 1.3 on ch 1 and 1.6 to 1.7 on ch40



If you do get a leak in the back glass and want to run the coax in a semi permanent manner, I ran mine through the back glass and solved the leak, i opened the glass and pulled the weather stripping and used a pair of wirecutters to notch the seat of the weather stripping and ran the coax behind the weather stripping instead of infront of it, i then fed the coax through the groove where the rear defrost line is on the passenger side, and used my fingers and pushed it behind the edge of the side moulding down to the plastic moulding that the rear swing door closes against, took that moulding up, and shoved my hand under the carpet while holding the coax and pushed it out between the back seats and ran it to the front

once i knew i had plenty of coax length i used black RTV gasket maker and sealed around the coax and the notch i made in the seat of the weatherstripping, after about 3 cured coats and using a gloved finger to rake it and push it against the back of the coax and stripping the leak was solved

have you had a chance to check the swr and what not on yours yet? how is it?

you typically ground the mount, some antennas have a ground strap built into them that you can use to create a better ground

i actually got worse SWR by grounding both the antenna and the mount, which I thought was a bit odd

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632


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PostPosted: Thu Mar 26, 2009 2:15 am 
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I'm impressed, very nice. Thanks for the write up.

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2007 Jeep Liberty
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Full factory Skids
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4 Hella 700FF's on Rack
2 KC daylighters on bumper
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I want to leave this world like i came into it.... screaming, naked and covered in someone else's blood.

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