Radio Hook Up

[maique]

i have a 74 dm positve ground my question is (dont wanna sound dumb but here goes) how do you hook up a radio and cb is there a special adapter or somethig

[Superdog]

You used to be able to get + ground AM radios,and the older CB's you could just reverse the wires,can't do that with the newer ones.I had an inverter in my '76 F model,but it went bad,found it was cheaper just to convert truck to - ground.

[maique]

when switching to negative ground do you have to rewire the whole truck or just the starter and alternator

[ThaddeusW]

You can hook up a newer CB and radio BUT you cannot let the metal case of the CB or radio touch any metal part of the truck. Hook the red positive wire to the chassis and the black negative to the electrical system.

[maique]

kewl thanks ThaddeusW

[HK Trucking]

If you isolate the AM/FM radio from vehicle ground, you've got to keep the antenna isolated from the vehicle ground also.

If the antenna is mounted to metal, it will ground back to the radio thru the coax cable, and fireworks will result.

Isolating the antenna from ground does reduce FM reception somewhat.

[other dog]

That's all I ever did,on the F-model and my mixer now,just hooked them up backwards-ground the red wire,hook the black to a hot wire. Seems unnatural,but they worked fine.

[HK Trucking]

That's all I ever did,on the F-model and my mixer now,just hooked them up backwards-ground the red wire,hook the black to a hot wire. Seems unnatural,but they worked fine.

CB radios pose no problem because they are not "chassis grounded", that is why they have a red (+) wire and a black (-) wire. The outside case of the radio is not "hot", or "grounded".

What I was referring to was AM - FM car radios when used on a positive ground system by hooking up the truck's "hot" (-) wire to the radio case, and hooking a wire from the radio input lead to the truck's "ground" (+).

In that scenario, the radio's outside case MUST not be allowed to touch any metal part of the truck, or a dead short circuit will result.

In addition, as I stated previously, if the AM - FM antenna is mounted on a metal part of the truck which is grounded, then it will ground back to the AM - FM radio thru the "armor" portion of the co ax cable, causing a dead short also.

Either the antenna must be insulated from ground at it's mounting point, or else you can strip off a small section of insulation from the co ax, and remove a short section of that outside braided wire that's just under the insulation, which will prevent it from grounding back to the radio from the antenna. After removing the section of braided wire, wrap the "modified" area of the co ax securely with electrical tape.

I've done it that way back in the 70's, and although there was a decrease in the FM reception after isolating the antenna from ground, that was certainly preferable to a dead short.

[other dog]

Oh yeah,I should have said that's for a cb-I never put in an am-fm or anything else electrical.I did find out on the mixer that LED lights have to be wired backwards too,where a regular marker light doesn't.

[maique]

hey thanks guys for all the info hey nice mixer truck