Need help understanding how to hook up a Mobile radio to the car battery

[Mogley]

Hello everyone. Im planning on purchasing a mobile radio for monitoring my area. Ive watched about 2-3 tutorials on how to install a radio into your car.

All I could get is about you need fuses and wiring to attach it right to the battery. So im alittle confused on what wiring to purchase. Where do i find wiring with fuses built in? Could someone send me a link?

Do i just attach said wiring to the battery by loosening up the correct connections and then just screwing it back together so that the wire is on the correct connections of the battery? Do I have to cut any wires in like hardwired it in to something that's already existing?.

I just need some advice on where to start

thanks, mogley

 

[pitheus]

Are you doing a in dash install of the radio or under dash with bracket, Is it a 2 way radio or just a scanner ?

 

[Mogley]

Are you doing a in dash install of the radio or under dash with bracket, Is it a 2 way radio or just a scanner?

im planning on buying a motorola xpr and or another motorola two way radio.

i plan on putting it on top of the center dash on a 2010 jeep wrangler

 

[mmckenna]

The exact radio and the exact vehicle creates some minor variances, but the standard approach is the same.

Radios want clean DC power, and the best place to get that is off the vehicle battery. Common noob mistake is to tap into existing wiring or think that a cigarette lighter is going to give you suitable clean power.

So, you want a positive wire running from the positive battery terminal. You want a suitable fuse for the wire size installed at the battery connection.
Do not run the negative lead for the radio back to the battery. Pick up a local ground and run the radio negative lead to that. No fuse needed on the negative side.

All wiring should be carefully routed to protect it from damage, abrasion, pinching, etc.
Do not run wiring under carpet where people will put their feet.
Avoid running new radio power wiring along side existing vehicle wiring where possible.
Use suitable size wiring for the current demand and length.
Use a wire suitable for automotive use. Exposure to heat/fuel/oil/chemicals should be considered. SAE has some specs for suitable wiring.
Fuse should be appropriately sized for the wiring, not just the load at the end.
Avoid splicing wherever possible.
Wire loom should be use to protect wiring. Loom should be appropriate for the environment (heat exposure under the hood, etc)
Grommets should be used wherever passing through sheet metal.


Routing of the wiring, firewall passthrough, grounding points, etc. are all vehicle specific, and if you share what vehicle you have, we may be able to assist further.

 

[mmckenna]

Sorry, missed your post about it being a Jeep Wrangler.

Good news is there are a number of posts on how to do radio installs in Jeeps. Do some searches and you'll find good info.

Be careful mounting on the dash:
-Airbag deployment must be considered.
-Heat exposure sitting on the dash like that can be problematic for some radios.
-Mounting needs to be very robust to keep the radio from coming loose in an accident.

 

[Mogley]

Do not run the negative lead for the radio back to the battery. Pick upa local ground and run the radio negative lead to that. No fuse needed on the negative side.

could You elaborate on this more?
are you saying I connect the black wire of my radio to the metal frame somewhere on my jeep? If not could you dumb it down a little bit more please?

 

[pitheus]

Depending on place of purchase the wiring with inline fuse should come with it. You will need to just locate the shortest route to connect it to the battery, usually by feeding the wires under the carpet on whatever side the battery is on and sometimes if you lucky you can find a rubber wire grommet under the dash and snake the radio wires thru it. You can purchase a adapter that will attach to the positive side post or top post of the battery that will allow for accessory add on electronics at at a auto parts store. You can ground to the frame of the vehicle or the car battery. In order for the radio to scan channels the mic holder will need grounding as well which you may accomplish by attaching the mic click to the side of the radio or you may have to run a short wire from the mic bracket to a ground point on the dash metal frame somewhere. The outside antenna cable you will need for reception will need to be dealt with also. That will depend all on the type you purchase. I have my cable routed under the door jams and then under the back seat into the trunk and to a lip mount antenna. It takes a bit of figuring.

 

[mmckenna]

could You elaborate on this more?
are you saying I connect the black wire of my radio to the metal frame somewhere on my jeep? If not could you dumb it down a little bit more please?

Yes. The chassis/body of the vehicle is grounded and acts as the return path to the battery.

Most newer vehicles have a sensor that goes around the negative battery lead (between the battery and the body/chassis) that monitors the current flow in/out of the battery. It's used to adjust the alternator output or otherwise monitor performance. The owners manuals for such vehicles will usually have some info on this. But, the rule is, you never give anything an alternate path back to the battery that bypasses that sensor.

Grounding to the body metal also gives the radio a nice short connection to ground, that can help with some noise mitigation. It saves wire, and makes installation easier.

Every LMR radio I've ever installed comes with instructions on installation that includes connecting the negative to the body and not running back to the negative terminal.

 

[mmckenna]

I'd add:

Consider the wiring job carefully.
The cheap wiring kits that come with most hobby/consumer radios are fine for a single radio.

If you ever plan on adding more than one radio, like a scanner, GMRS, CB, ham radio, etc. think about making your own wiring harness. Running one larger wire is a lot easier than running a bunch of separate circuits. Plus, it looks cleaner and more professional.

On my personal truck, I ran 6 gauge wire from the battery positive terminal to a 60 amp circuit breaker on the firewall. The 6 gauge then runs through a grommet on the firewall to behind the rear seat (crew cab truck). Behind the seat, the 6 gauge terminates on a fuse block that allows me to add up to 4 radios just by connecting and installing a fuse.

Much easier to add/change things without a bunch of extra labor.

 

[ladn]

Im planning on purchasing a mobile radio for monitoring my area. im planning on buying a motorola xpr and or another motorola two way radio.

The question arises (at least in my mind) of why buy a two way radio just for monitoring? True, a two way radio will usually offer superior performance over a scanner, but some of the trade offs include flexibility, cost and ease of programming.

Motorola software can't be described as "user friendly" and if you're trying to monitor a trunked system using NAS, you are potentially opening up a whole big can of worms that's been discussed ad nauseam on RR forums.

 

[vagrant]

@Mogley - Using a scanner would be a significantly better and easier solution for you. You can simply use rechargeable batteries for a handheld. A Uniden SDS100 and or a Whistler TRX1 may take care of your monitoring needs. Alternatively, there are mobile versions as well in the Uniden SDS200 and Whistler TRX2 if you prefer that. You could simply wire those to a vehicle power port (cigarette plug) as their power draw is relatively low.

The next point would be programming the frequencies you wish to monitor. As ladn noted above, Motorola CPS could be problematic for you. The scanners above are not as much of a problem.

 

[slowmover]

Quote

“ . . On my personal truck, I ran 6 gauge wire from the battery positive terminal to a 60 amp circuit breaker on the firewall. The 6 gauge then runs through a grommet on the firewall to behind the rear seat (crew cab truck). Behind the seat, the 6 gauge terminates on a fuse block that allows me to add up to 4 radios just by connecting and installing a fuse.

Much easier to add/change things without a bunch of extra labor. “


On this note:

My approach is the same. Be able to power related devices such that the initial power installation accommodates future needs.

There are quite a few choices as to 12V Distribution. Choosing & “locating” that device is Job One for Mobile Radio, IMO.

Radio location can change.
Radio choice can change need.

While “the radio” seems first, it’s sort of not.

The 12V distribution block described above is illustrative. The radio control panels are elsewhere. The radio main bodies are near that 12V panel.

With my radio choices (pickup or big truck) the radios don’t have detachable controls.

Electricity being what it is — and the expense of doing things first rate — have a look at plenty of installs to see rhe pattern.

It’s enjoyable to, “do it right”.

From, The Amateur Mobile Radio Guide:

Wiring & Grounding

.

 

[WA8ZTZ]

Yes. The chassis/body of the vehicle is grounded and acts as the return path to the battery.

Most newer vehicles have a sensor that goes around the negative battery lead (between the battery and the body/chassis) that monitors the current flow in/out of the battery. It's used to adjust the alternator output or otherwise monitor performance. The owners manuals for such vehicles will usually have some info on this. But, the rule is, you never give anything an alternate path back to the battery that bypasses that sensor.

Grounding to the body metal also gives the radio a nice short connection to ground, that can help with some noise mitigation. It saves wire, and makes installation easier.

Every LMR radio I've ever installed comes with instructions on installation that includes connecting the negative to the body and not running back to the negative terminal.

Good advice.

Always connect the radio negative lead to the chassis/body of the vehicle. Do not run the radio negative lead directly to the battery.

With the radio negative lead connected directly to the battery negative post, if the vehicle battery negative to ground (chassis/body) connection were to become loose or broken or disconnected for some reason, all the return current would flow through the radio via the coax shield and radio mounting tray back to the battery. Even if the radio negative lead was fused, damage could be done before the fuse would blow.

Also, on newer vehicles, many are equipped with a battery management sensor which would be bypassed if the radio negative lead was connected directly to the negative battery post. Bypassing the sensor could cause an inaccurate determination of the battery state of charge and not allow the alternator to properly charge the battery.

 

[tvengr]

Especially with scanners and CB radios, try to route the antenna cable as far away from vehicle computers and computer cables as much as possible to minimize noise pickup. I installed many 110-watt 450 band mobile radios in our news vehicles. When running cables under the dash, keep them away from sharp metal edges and any moving parts such as the steering wheel shaft. accelerator pedal, brake, clutch, and parking brake. I used cable ties to secure the cables in a safe position. Be careful when working under the dash. There are many sharp edges and I have the wounds to prove it. Our radios were trunk mounted with a control head in the passenger compartment. When working in the trunk, I always left my legs handing out. The guys I worked with would love to slam the trunk shut and trap me inside.

 

[03msc]

I'll add...I would advise against putting any radio on top of the dash.

 

[G7RUX]

These are all pretty good bits of advice but one thing I would suggest is that you run the negative lead of the radio back to the battery BUT DO NOT CONNECT TO THE NEGATIVE TERMINAL…connect it to the chassis near the battery. I say this from having had fun with noise picked up in the DC leads getting into the radio and doing it this way allows using a common mode choke on the DC supply at each end.

 

[w2xq]

In addition to mmckenna's suggestions above, I would check your motor vehicle laws about mounting radios (or other objects) on the dash. In some states that action falls under "obstructed vision" laws... subject to a fine.

 

[KK6HRW]

In addition to mmckenna's suggestions above, I would check your motor vehicle laws about mounting radios (or other objects) on the dash. In some states that action falls under "obstructed vision" laws... subject to a fine.

Good advice. Also make sure that the radio on the dashboard is well clear of an airbag zone.