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Mounting a very large CB antenna

NeXT

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Joined
Oct 22, 2008
Messages
6,743
Location
Kamloops, BC, Canada
So I got this idea that because I own a car, I should build a CB radio into it instead of have it sit on the dash or shimmed between the seats.

P1033604.jpg


Now that it's installed and all wired up I needed an antenna. Because I had a Geo Tracker with a soft top there is really no spots to properly put an antenna with a magnetic base on it unless it was on the hood. I was talking about this to one of my friends who then went and pulled something out from behind the shed.

P1033603.jpg

This is the nice ballmount and spring that the antenna mounts on (no hardware was included but it's easy enough to buy nuts and rubber washers).

P1033605.jpg

That 8' monster is the antenna itself.
He gave all of the above to me for free and something like this would freaking rock.
The problem now is that it's so large I can't leave it standing straight up all the time (around here it will get you tangled up in power lines) so it needs to be bent over when I'm not out in the woods. Because I can only bend the antenna so far I can only mount it on either the front or the rear of the vehicle. Preferrably I want it near the back but I can't find a place to put it.

>Left< >Back< >Right<

I can't just drill a hole in the side of the car and bolt it in. The body is just too weak for an antenna that size and without some sort of reinforcement the fatigue caused by the antenna waving around from movement, wind or stuff hitting it will eventually cause severe damage.
I ahve been trying for two days now to fgure out where to put it and I just don't ahve any ideas. You got any words of wizdom?
 

barythrin

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Oct 5, 2005
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Texas
Never done anything like it myself but couldn't you install that trailer hitch/ball in you rear bumper and route the cable with your speaker wires to the trunk then somewhere out the back (or under the vehicle but I see obvious problems in the future with that). Just guessing along though. I'd guess if the cable started from your bumper it would only be 3-4 feet above your vehicle. I'd be surprised (although I already am) if your power lines are that low.
 

kvanderlaag

Experienced Member
Joined
Oct 17, 2009
Messages
126
Location
Vancouver, BC, Canada
Bumper would be a good idea - actually, even mounting it to a trailer hitch would be cool - just pull it out of the receptacle when you need to attach a trailer or you don't want to cart it around with you, and have a breakaway wiring connector.

Alternatively, I might look for a telescoping antenna. I know it's not free like this was, but a stationary (even if rotating) 8' antenna is just a little much to be maneuvering.
 

Chuck(G)

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Pacific Northwest, USA
The traditional way was a rear bumper mount and a clip attached to the roof gutter to hold the antenna bent-over. Standard clearance around here is about 14' for power lines and bridge overpasses.

Perhaps you can take a piece of mild steel bar stock and bolt or weld it to your rear frame.
 

Lou - N2MIY

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Albuquerque NM / Potomac MD
Nice 11 meter band installation there. I like that DIN plug on the side of the console.

Usually those whips are 108 inches (1/4 wavelength on 11M). Yours may have been cut down. Be sure to check the SWR when you have it mounted. Being shorter, the match may be better on the upper channels.

As for mounting, through the rear quarter panel might be your best bet, since there is probably no easily accessable steel in the bumper area. But you are right about the thin sheetmetal and the need to spread the stress out. If there are any large flat portions of the panel, big fender washers on either side of the mount would help a lot. In addition, you should also consider reinforcing the back side of the fender from inside the trunk. I am imagining a piece of wood, shaped to match the contour of the body panel inside the trunk glued to the inside steel (say with liquid nails).

Lou
 

MikeS

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Dec 23, 2005
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Toronto ON Canada
LOL!

Believe it or not I have one of those whips in my garage from the distant past when it was mounted on the back of my '67 Chrysler Imperial (the huge, heavy chromed steel bumper probably weighed as much as your whole car ;-)

But the really funny thing is that only yesterday I was wondering how it would look on my Honda Civic, and how I could mount it; I listen to AM a lot and the Civic's antenna was kinda poor even before it got bent and damaged.

As Lou suggests, I'd check the SWR if you're going to transmit with it; chances are that it's not going to be a very good match and your output will be reduced, and although unlikely it could even damage the output stage of the rig.

I *really* want to see a picture of your car with it installed; maybe it'll inspire me.
 

NeXT

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Joined
Oct 22, 2008
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Kamloops, BC, Canada
I can test to see if I can still properly retune the antenna with this radio but it and any more work will have to wait until next week as I got work in the morning. I hope though that I'm not going to find out that it's too short, otherwise I'll have to dige out the old fiberglass one and live with that.

My only real concern regarding mounting to the bumper or to the framing below is that of clearance. One reason I like the tracker over my parents Subaru Ouutback is that it stands a lot higher off the ground. I don't know if I'll beat it up if I put it too low. Also, if anyone cares much, I'm kinda trying to make the installation nice and tidy so it looks good.
If I do man up and just mount it to the side of the car (Still don't know exactly how much in the way of reinforcement will be needed) I won't need a piece of wood. I got a big sheet of thick rubber I can cut to any size I want :).
Apart from power lines, up around here you are not allowed to drive in paved areas with an antenna exceeding 3' above your car. If it's taller you need to have a way to bend it over and secure it.

I *really* want to see a picture of your car with it installed; maybe it'll inspire me.
How is this for additional inspirement? It's currently hanging off my rear view mirror.
 

Chuck(G)

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Pacific Northwest, USA
If it's too short, you can try using a loading coil at the base to bring it into range.

The lever arm on these things when in motion can be fierce (look at the size of the spring on the mount). They worked well enough on the bumper of an old American car, but you're going to come to grief if you don't secure it to the frame of your ride somehow. You might try fitting a hitch adapter and secure it to that.
 

kb2syd

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Mar 7, 2005
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Wantage, NJ
I see that you have what appears to be a "tow tag" on the back right of your Geo. I've bolted a 10m setup to one of these. I used two pieces of 1/4" stock with three holes drilled through. I sanded the surface of the tow tag and of the steel stock and made a sandwich as such
Code:
         V
===========
UUUUUUUU
========
where the flat stock is the ==== and the UUUU is the tow tag. Bolting through the stock and tow tage I had a very secure mount. I then drilled a hole in the longer end of the stock (where the V is) to mount the antenna through.

Make sure your tow tag is attached to the "frame" of your vehicle. Also, make sure you have some way of removing the assembly in case you need to be towed...
Kelly

PS Get your ham license. I operate 440, 2m, 6m, 10m, 15m, 20m and 40m mobile. The antenna stinks but I've worked into Macedonia mobile on 15m.
 

NeXT

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Kamloops, BC, Canada
hmm. That sounds like a very good solution but then I realized that it's then in the path of the back door and I can't do that.
Do they make such coils pre-made or will I have to make one myself?
 

Chuck(G)

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There are pre-made loading coils, but you're not talking a lot of power here. It's certainly possible to make your own. We used to use sections of Air-Dux as base-mounted loading coils, but the stuff is hard to find nowadays. Fortunately, the ARRL has a nice guide on making your own. Or you could devise a center-mounted loading coil--there are commercial versions available.

But I'd check the SWR of the unloaded antenna first. If it's reasonable, best to leave it alone--any loading coil will contribute a small amount of loss.
 

NeXT

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Kamloops, BC, Canada
As a matter of fact, I just got bact from checking that.
There is a built-in SWR meter in the radio and I have an external tester as well so I deced to get reading from both. I drove to the most open area I knew which was a hill a few minutes from me and the results were not what I wanted.
According to here, if the SWR on channel 1 is more than on channel 40, the antenna is too short and must be lengthened which means that if I want to use this antenna it will have to be lengthened.
I think this is turning into way too much trouble than it is worth, and I can't find my shorter and newer fiberglass antenna anywhere....
 

kb2syd

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Wantage, NJ
How did you have it mounted when you checked SWR? Do you have a picture of that?

As for it being in the way of the door if you mount as I suggested, rotate the mount 90 degrees to the right as you're looking at it. Make the longer pice of stock just long enough to get past the edge of the door.
 

salamontagne

Experienced Member
Joined
Feb 27, 2010
Messages
244
Location
Harwinton,CT
wow, nostiliga.....


I used to be into CB back in the day, and used to see setups like this. Thanks for the memories, I'm now remembering drilling a hole in the roof of my plymouth duster for one of those "do-it-yourself" cable-to whip thingy's (no i cant remember the name of it)

I thought i was saveing money by not getting one of those coils.....untill i realised i bent my roof when the whip antenna hit the roof of a parking garage......

Wow......as ive said in another post....i really thought i knew everything back in the day.... :p
 

NeXT

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Kamloops, BC, Canada
As a matter of fact I did photograph how I had it setup for testing.

P1043615.jpg


I put the whole shebang in a vice and insulated it with bits of rubber and then used a very short alligator clip lead to run from the antenna to a chassis jack and then into the car using the usual coaxial cable.
Oh, so you mean let it go off to the side and then come up closer to the tail light? I can do that and I don't think I'll be needing a tow often.
 

Lou - N2MIY

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Albuquerque NM / Potomac MD
The convertable top of your car is not a good ground plane, so don't write this antenna off just yet.

To lengthen the antenna, consider a piece of 3/8"-24 all thread and a 3/8"-24 coupler nut.

Alternatively, get your ham ticket, as Kelly suggests. Then, this short antenna will load up on the 10M band.

Lou
 

NeXT

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Oct 22, 2008
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Kamloops, BC, Canada
For the most part I didn't even think I needed a good ground plane. I just thought that for the most part you just had to prevent it from grounding to the car body.
I also refuse to get a ham license. It's too much of a hassle for me personally and from past experience it's really expensive.

To lengthen the antenna, consider a piece of 3/8"-24 all thread and a 3/8"-24 coupler nut.
if I need an additional sevn inches or so, why not get a coupler nut and a length of threaded rod? I could do coarse tuning by cutting down the rod and the fine tuning by trimming the antenna.
I can do that no problem but I don't have the tools or connections to get a 1/4" slab of steel cut to the size I need for the mount.
 
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