Cobra cb

[I HATE PONIES]

Just got done installing my new cb radio. I kept the antenna inside for ease of installation and for protection. It is a flexable 4' with a 9' cable made by Diesel and costs about $20.00. You will need 10' or more to make it out the rear door from under the seat. I don't know how well it's going to work but it looks pretty good so i will try for a while at least.

The radio is a Cobra 75 wx st. I got it on Ebay for around $100.00. It fits under the back of the front passenger seat very well. I was even able to get power from the under seat fuse box. The antenna cable was run to the rear under the trim and carpet. If you are creative you will not have to remove any trim pieces.

Installation was easy and took around an hour to complete. Here are some pics.atriot:

 

[jhmover]

I just put one in my D1last week, I put the antenna on the rear tire carrier, box under the seat, mounted the mic on the two blank switches next to the cruise control switch so I can see it, no CD changer but the wires are there so I used them for power.

 

[scottjal]

You put the antenna inside the truck?

 

[KevinNY]

You will be moving that antenna, your SWR reading will be crap inside the truck. Plus you mounted it on plastic, it has no ground. The best spot for an antenna is the center of the roof, 2nd best is mounted on a brushbar. Less than 1/3 of an antenna should be within 12" of the body to get good readings.

 

[I HATE PONIES]

You will be moving that antenna, your SWR reading will be crap inside the truck. Plus you mounted it on plastic, it has no ground. The best spot for an antenna is the center of the roof, 2nd best is mounted on a brushbar. Less than 1/3 of an antenna should be within 12" of the body to get good readings.

So far not working so good. I didn't realize the antenna has to be grounded. Can I leave it inside and just run a grounding wire to it?

It has aluminum brackets and the cb guy said it would ground through the cb. I will try to ground it with a seperate wire.

It wont pick up my handheld from 4 feet away so something is wrong.

Is the problem being inside the truck or just not being grounded?

 

[flyfisher11]

The antenna needs to be outside and well grounded. The best place on a disco is on the front bumper. Actually up top is but for wheelin' you'll snap it off. So the best compromise is about a third way in on your front bumper. This will keep it away from the truck enough to get a good signal and also keep it from getting snapped off from trees etc..

Cheers,

Mike

 

[I HATE PONIES]

How did you guys get to the outside with the big connector? I can put it anywhere but the front bumper. I think it would look stupid there. Is there any reason to have it higher vs dryer apart from the ground?

 

[BaldEagle]

i have mine on my spare tire mount and i get reception thats perfect for me. i only use it on the trails. i think my range is around a mile or a little more. not impressive but for what i use it for its fine. it will not work inside the truck. you'll have to move it. the higher the better. if you put it on the front bumper, just disconnect it when you won't be using it (i.e. most of the time) to get it out the back door you have to drill a hole big enough for the connector

 

[I HATE PONIES]

Hate to beat a dead horse but why does it have to be outside the truck? My handheld works just fine inside the truck with a lesser antenna. I'm not going for super range just want to talk to the people I'm wheeling with.

 

[BaldEagle]

Hate to beat a dead horse but why does it have to be outside the truck? My handheld works just fine inside the truck with a lesser antenna. I'm not going for super range just want to talk to the people I'm wheeling with.

it has to do with line of sight. when its inside the roof of your car is shielding it. before i bought mine i did alot of reading up on them since i didnt know much about them either. do some google-ing and you should learn alot. that being said, i just bought a pair of midland 25 mile frs/gms handhelds and i like them alot better. most people use those now.

 

[flyfisher11]

How did you guys get to the outside with the big connector? I can put it anywhere but the front bumper. I think it would look stupid there. Is there any reason to have it higher vs dryer apart from the ground?

I see. It's about looks over function. You won't get a better place than up there for function. As a matter of fact TJM comes stock with the mount up there and ARB has the bolt on adapter. I have RTE and can drill a mount or weld one on. If you don't like the looks you can always remove it until you hit the trail.

Cheers,

Mike

pics courtesy of RTE note antenna placement

EDIT: I forgot you had that tucked up (not a misprint I mean tucked by the way you created the bumper to follow the lines of the truck and give you maximum approach angle) custom bumper. For some reason I was thinking you had RTE. I'd say in your case the tire carrier would be best JMO.

 

[SGaynor]

Hate to beat a dead horse but why does it have to be outside the truck? My handheld works just fine inside the truck with a lesser antenna. I'm not going for super range just want to talk to the people I'm wheeling with.

Go here: http://www.firestik.com/

and read their Tech and FAQ sections. It'll answer most of your questions. They also have a list of items to purchase to wire up a Disco.

EE had a write up on installing a Firestik antenna on the spare tire mount, but I can't seem to find the link right now. (The link on the firestik website doesn't seem to be working either). - Damn I just re-found that article a few weeks ago...

No matter what antenna you install, it's got to be outside, with the top above the closest part of the body (in front - the hood; in rear the roof), and you'll need to tune it with a SWR meter for best performance.

 

[KevinNY]

There is a sufficiently large hole to pass the connector forward in the firewall under the edge of the carpet behind the brake pedal.

 

[I HATE PONIES]

Thanks for the help. I grounded the antenna to the chassis last night and it was able to recieve but it would not transmit. I could hear truckers from miles away but my handheld wouldn't work at 6'. I tried moving it outside tonight with similar results. I think tomorrow ill drill the bumper up front and try it there. The thing that kills me is that the instructions say not to mount the antenna to aluminum but the damn bracket it came with is aluminum.

 

[lagged]

The antenna needs a ground plane not a ground. The body of the car will be a fine ground plane. If you just want to use the CB on the trail it doesn't really matter what you do with the antenna. I would use a cell phone style antenna that shoots through the window just to get it out of the cabin.

If you ground the antenna you are just going to send some engine noise into it. Follow the directions that came with your antenna for ground or not. My firestik made a point about it not being grounded, but you do need a ground plane.

 

[Captainruss]

It may also have trouble transmitting until you get it properly tuned. Definitely get it outside the vehicle and then get it tuned at your local truckstop.

 

[apg]

So far not working so good. I didn't realize the antenna has to be grounded. Can I leave it inside and just run a grounding wire to it?....

Is the problem being inside the truck or just not being grounded?

It's not so much the ground as it is the ground plane. For maximum efficiency radiating in all directions, the antenna needs to be mounted near the center of mass - and high up. For a Series Rover with the separate "sun-sheet" or tropical roof, that was a near perfect ground plane. The radiation - direction of maximum signal strength - will be skewed towards the center of mass. Put something off the front right brush bar, and you'll be able to communicate best with someone to your left rear. I can't imagine that any antenna mounted *inside* the vehicle could "get out" at all....

Additionally, the antenna needs to be matched to the wavelength, with antenna length = wavelength being the best. Many vehicles had 1/4 wave whips - about 109" long, but many times that is impractical. Antenna vendors get around this with coils - typically a base "loaded" mount. Buy an SWR (standing wave ratio) meter if the unit doesn't have one built-in. They are inexpensive.

Cheers