Installing a CB

[lawrence]

My loving wife bought me a CB radio the other day. I've managed to mount the Cb itself the problem i'm having is thinking of a way to get the wires into the engine bay to get power from the battery. What is the easiest way to get wire there without having to start taking things apart. Or could you wire it into the fuse box. I have no idea how to do this so lots of detail would be needed.

if it makes a defference its a midland 278.

i've put the CB on the dash just above the radio, if that helps.

Many thanks in advance

[leon_81]

i've wired mine into the back of the cigar lighter (as that never gets used)

i just pulled it out, and connected the + and - for the CB and then put the lighter socket back in for neatness

[M&S]

As above, I also used the back of the cigar lighter until I got a second battery installed, now it runs direct from that. Easy to pass the cable down behind the dash/stereo etc to reach it. Just make sure you pop a fuse in the line, they usually come with a 1A glass fuse in-line anway.

Just be aware that, on the D2 at least, this is only powered when the key is in.

[lawrence]

Is there a trick to getting the wire behind the dash, I couldn't see an easy way to do it. That is my biggest problem, I can't see how to hide the wires.

[disco_al]

the easiest way to run the wires is through the vent above the radio, down the back of the dash then out through the grommet that the throttle cabls passes through.

[SeanDisco]

I've wired mine to the plug for the cd head unit, then ran the ariel wire through the hole above the throttle, accross the back of the engine bay and up to the ariel.

[lawrence]

managed to get the wire sorted out. Got it to the battery by going through the hole that the throtle cable comes out. My problem now is that i can't get the SWR meter to read less than 3. The instructions say that this is too high but nothing I try seem to lower it. the ariel is a gutter mount behind the passenger rear door. with the wire run in the headliner and down the door pillar. Has anyone had a simular priblem. I think I am going to have to ring the guy where i got it from to see what he says. I just wanted to see if you had any idea's first.

[MrKev]

What sort of aerial?

[lawrence]

The aerial is a just a normal aerial with a big spring thing attatched to the car with a gutter mount. Sorry for the lack of technical terms. the CB was bought as a package so we only chose the mount and the spring size.

[headhunter]

Have you started reducing the aerial length? It is the usual practice to cut small pieces off it (the straight length) until you have the required reading on the SWR.

Only 2-3mm at a time though!

Hopefully someone with more knowledge than me will be along here to advise further.

John

[MrKev]

A 'springer'

Most have a small grub screw holding the long straight bit to the spring, which you can loosen, then shorten the whip to tune. Once you've found a good spot, you may choose to trim some off, or you may not.

Kev

[leon_81]

if you've got down to 3, you're doing better than i am, mines off the scale and nothing i do seems to help! someone suggested earthing the gutter mount, but that did sod all - i think my CB may be knackered

[lawrence]

I've been recomended by the shop to move the mount more to the frount of the vehicle as the high sides of the roof can effect the signal. I am going to try that tonight and see what I get. One question I have is, can I still use the CB with a SWr reading of 3 or will it cause the cb damage.

[lawrence]

I moved the gutter mount lastnight from just behind the rear door, to right up front next to the snorkel. When I checked the SWR reading it had fallen to 2.5. So i little improvement from 3. Although the mount did break while moving it. I've sent it back and now waiting for a replacement. Is a swr reading of 2.5 okay, what will a lower reading actually do, will it make a difference.

[Biffo]

If you are having difficulty with the SWR, the first thing to do is check that the wiring is right and there's no short. undo the aerial from the CB, and the aerial itself, now use a meter for conductivity, and check between the inner pin of the PL259 and it's outer body (connection plug on the end of the wire that goes onto the CB) you must NOT have any connection between the inner & outer parts.

If that's OK, SWR at ch1, and at ch40, if the REF reading id worse at ch40, the aerial is slightly too long, if it's worst at ch1, then it's too short. when trimming an aerial down, only trim small amounts off especially when getting "near".

a long whip aerial on a gutter mount (I hate gutter mounts!) should get down well below 1.5 / 1.

Don't forget that every time you check the SWR, do it properly, zero on "set" then read the scale on "ref" also DON'T try SWRing a CB when near to buildings, caravans, etc. It could mess up the readings, ideally you need to be in an open space.

You can make faults if you have the coax trapped beteen the door/frame.

[bushwhacker]

Great info Biffo. Will be off good use to me also.

I been told if the swr is slightly high you can still use your cb on short burst conversations.

The cb may overheat if the mike is keyed for too long, avoid this.

Grounding an aerial is not the same as an "electrical earth / ground".

It is radio waves not electric you are working with. Alloy will work ok as a ground.

[Biffo]

Great info Biffo. Will be off good use to me also.

I been told if the swr is slightly high you can still use your cb on short burst conversations.

The cb may overheat if the mike is keyed for too long, avoid this.

Grounding an aerial is not the same as an "electrical earth / ground".

It is radio waves not electric you are working with. Alloy will work ok as a ground.

Yes to a point, CB's are obviously made to withstand a bit of abuse out of range, but how much is down to the manufacturer. really if you can't get below 2, then you need to change the aerial, a simple DV27 or one of it's cousines are easy to use & SWR, and are decent aerials as well.

I have fitted these to mine, & all my mates, we have no problems what-so-ever now. It's one of the DV27 family, but has a spring at the base, should it get hit by branches, it bends out of the way, then returns into position.(I bought it from CB Shack at the services, J20 on the M6) CB shack

In fact, checking through their catalogue, This is the actual aerial

Should you want one of these, they do them just as the whip alone as well as the full job (the coax isn't long enough to go to the rear of a disco anyway) give them a ring and sort things out as separate pieces.(or call in there and buy them)