Where to ground?

[Brasso]

I'm installing a Kenwood TM-281 in a truck and I'm wondering where the best place is to run the negative wire. To the battery or to the frame?

Thoughts? Does it make a difference?

Any recommendations on what type/brand of filter I should use on the positive wire, if any?

Thanks.

 

[robertmac]

Every post on here say to run the wire to the battery. Search these threads and you will see. Most also say to have fuse on both pos. and neg. wires. And use largest wire possible. Can't help with filter as have never used one.

 

[W2JGA]

It's just an FM 144 rig and a filter shouldn't be needed unless you hear alternator noise on the output speaker or your transmit audio has alternator noise.

 

[jim202]

Every post on here say to run the wire to the battery. Search these threads and you will see. Most also say to have fuse on both pos. and neg. wires. And use largest wire possible. Can't help with filter as have never used one.

I have to disagree with your comment that every posts says go to the battery negative post. It all depends on where your coming from and who taught you mobile installations as who you want to believe. The common practice with commercial public safety radio installs is to use the frame ground / body ground of the vehicle. The off shore radio supporters say go to the battery as that's what the jap track radios all do.

Then there is the argument that if the battery ground to the frame goes bad, the starter current will come back to the radio through the coax cable and blow the radio. You will hear all sorts of stories.

I have been in this commercial radio field for well over 45 years now and have never seen a fire truck, dump truck or big tractor trailer rig blow up a radio because of a bad battery ground cable. If that cable starts to go bad, you will have issues starting the vehicle and the clock in the dash radio will start jumping to 12:00 if the battery voltage goes low. You need that cable to supply the current from the battery to the starter motor. If it goes bad, the starter won't work. You have lost the battery connection. No battery connection, no voltage.

Do as you feel best. Believe what you want to. The stories run the entire gauntlet.

 

[N4KVE]

I always connect both radio wires to the battery when I can, but on my last car, I connected the ground wire to the shock tower. Just depends on each car. My current car came from the factory with both wires connected to the battery. I haven't noticed a difference between the 2, but when I connect the ground to the chassis, I install an extra wire from the - terminal on the battery to the chassis.

 

[Brasso]

I went ahead and ran it to the battery.

Thanks everyone.

 

[WA0CBW]

Depends on the Make and year of your vehicle. Newer vehicles insert a current sensing device in the battery to ground wire for a computer to monitor and make decisions about the vehicles current demand. This raises the battery a few milli-volts above ground. Connecting the negative lead of a radio to the battery bypasses the sensing device and can cause the computer to make wrong decisions about the current demands. A good place to connect the negative lead of the radio would be where the battery to chassis wire connects to the chassis.
BB

 

[AK9R]

Allen Applegate K0BG is the guru when it comes to amateur radio mobile radio installation. Most of his stuff is geared towards HF mobile, though his web page is good reading for anyone installing a mobile radio.

Wiring & Grounding

 

[ke6gcv]

When I used to do client installations, I would find the nearest common grounding post under the dashboard and use that. Otherwise, I would go through the engine firewall and attach to a common ground there. And yes, I would attach a fuse to the ground, too. As far as positive connection goes, I always trace the red line from the battery to the fuse block under the hood and attach there.

 

[Brasso]

So I attached the negative lead to where the batteries negative is grounded to the frame and connected it there.

The positive lead is attached directly to the positive terminal on the battery. I guess my question now is, "is this OK"? The positive terminal looks like an airport hub. It has terminal posts all over it. I attached to the center terminal that looks to have two fuses on either side of it. Is this ok or should I connect somewhere else?

 

[WA0CBW]

A couple of things......Be sure each connection to the battery terminal post is fused. It might be better to install a positive terminal distribution bus and make all other connections to this bus. Think of your cars electrical system as you would the electrical system in your house. You have a main breaker (fuse) and then you have a breaker for each circuit. I would put a main fuse in the line from the battery to the distribution bus and a fuse in each device connected to that bus. You can find a distribution bus that has a place for a fuse for 2 to 14 circuits.
BB

 

[Brasso]

The radio came with a fuse already in line for both leads.

 

[DisasterGuy]

As was mentioned early in this thread, you will not find and commercial / public safety grade manufacturer that I am aware of (including Motorola and Harris) recommending taking the negative to the battery or fusing it. Those two items only tend to raise their head in the amateur radio world. In fact Harris only provides a 3 or 4' long negative on their power cables specifically directing that it be as short as possible to the frame. Likewise, GM SSV/PPV packages provide a high current positive for the driver's side rear and a stud to the body for ground. Believe what you will but working on radios costing thousands of dollars and that people's lives depend on for a living, I will stick with what the big players (radio and vehicle manufacturers) recommend.

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[N4KVE]

Funny, on my Impala PPV, I do have that high current + terminal, & ground stud in the trunk for a trunk mounted radio, but for a front mount radio, under the passenger carpet there are 4 wires. +, -, ign trigger when the key is set to run, & another when the key is in acc. But I don't know if the - wire is connected to the chassis ground, or - battery terminal. But it was sure nice to not have to find a place to route wires through the firewall. LOL.

 

[DisasterGuy]

Not sure about the Impala. Was speaking mainly to the Tahoe / Suburban chassis

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[ke6gcv]

Don't want to get off topic here, but PPVs as a whole should have common locations for power that are installed by the manufacturer (Ford, GM, Chrysler, etc.). If not, I'd question the agency as to where the power points are.