wiring a VHF please confirm what I already know

[johnnyandjebus]

Hello

I am wiring in a VHF radio into the boat this weekend, the radio has two wires that I am questioning.
Black/red, no inline fuse.
solid red with an inline fuse(10 amp).

The solid red is the hot wire, and the black/red is ground correct?

The manual does not say but I can't for the life of me come up with a reason for an inline fuse on a ground wire.....

Thanks,
John

[SEMIJim]

Originally Posted by johnnyandjebus

Hello

I am wiring in a VHF radio into the boat this weekend, the radio has two wires that I am questioning.
Black/red, no inline fuse.
solid red with an inline fuse(10 amp).

The solid red is the hot wire, and the black/red is ground correct?

I entered the question above into the Magic Eight Ball and it answered "Definitely"

(I am not making that up. I really did enter that question and it really did give that answer.)

More seriously: I wouldn't even question it, but...

Originally Posted by johnnyandjebus

The manual does not say but I can't for the life of me come up with a reason for an inline fuse on a ground wire.....

See: Previous thread about "positive ground/switched negative," wherein somebody came up with a bilge switch module that had a panel fuse on the negative side. Seriously.

I'm sure it's in the manual. What radio is this? Identifying the equipment in question is always a good idea when asking questions, even if you think the answer obvious.

Jim

[johnnyandjebus]

Hey Jim

Thanks for the reply, I too would normally not question it, but the manual does not state either way. I've been thru it more than once and can't find anything. So all I am left with is logic and logic says why have a fuse inline on a ground wire?


The radio is an Icom IC-M304

John

[fallard]

The original post stated there was an inline fuse on the red wire, which should be the hot (+) side. The black wire goes to the (-) side of your battery bank and is probably grounded. So it looks like you DON'T have a fuse on the "grounded" side. That said, your radio will most likely work better if it is grounded and your manual probably says something to this effect.

To close the circuit, you would have an equal amount of current flowing through the red and black/red wires, so a fuse on either one would break the circuit if the radio malfunctions and generates an unusually high current.

For what it's worth, the original radio in my sailboat, installed by the builder, had inline "littlefuses" on both wires, in addition to its own breaker (on the + side). I just replaced the radio in my powerboat. It came with a single inline fuse on the red wire, which is connected to the battery + side.

Bottom line: Standard practice is to have an inline fuse on the red wire near the radio. It can't hurt to have additional one on the negative side, too.

[tomperanteau]

It's an added safety measure to fuse both lines. If one fuse is a little too heavy and over its rating, then the other will blow. Kinda like two hose clamps on all the through-hull fittings, only not quite as important.

[mitiempo]

I have an Icom IC-M304 I installed last year. I just checked the wires and they are solid red and solid black. But the fuse definitely is in the positive (red) wire.

I also checked the manual and you are correct - they don't say. But I seem to recall a tag on one of the wires stating it was positive.

[SEMIJim]

Originally Posted by tomperanteau

It's an added safety measure to fuse both lines. If one fuse is a little too heavy and over its rating, then the other will blow. Kinda like two hose clamps on all the through-hull fittings, only not quite as important.

Not even remotely important. Just fuse the thing, once, correctly in the first place and be done with it.

Jim

[mitiempo]

I agree. The fuse in the positive will blow if there is a fault thereby interrupting current flow.

[TropicCat]

more importantly, is there RG-6 coax in the boat or RG-58? Big difference between the two performance wise.

[rbarkas]

Originally Posted by TropicCat

more importantly, is there RG-6 coax in the boat or RG-58? Big difference between the two performance wise.

You don't want to use RG-6 cable on a VHF radio. RG-6 is 75 ohm cable for TV use.

Use RG-8 or better yet RG-213 cable for minimum loss. RG58 works ok for short runs but not for a masthead antenna.

If you really want extreme low loss cable look for some LMR-400 but be aware that you need to get connectors that are designed for it. RG8 connectors can be made to fit it but the correct connectors are better.