Professional mobile wiring help.

Colton25 · Jun 21, 2015

Can someone here point me in the right direction so I can do I a proper mobile wiring install. I'm looking for advice/tutorials/videos on what I need to do to create a professional, reliable, and safe mobile radio wiring install. This will be for potentially 3 radios (future), 2 radios for now. I know that the way I have my radios wired now probably isn't the safest or most reliable way so I want to clean it up. The radios will be between 50 and 100 watts and I will only transmit on one at a time. I need the radios to operate off the ignition, I don't necessarily desire a timer but if it is required that's all the better. My wiring job right now consists of both radios spliced together and tied into an existing open ignition fuse using a fuse tap.

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ke6gcv · Jun 21, 2015

zane018 said:
Can someone here point me in the right direction so I can do I a proper mobile wiring install. I'm looking for advice/tutorials/videos on what I need to do to create a professional, reliable, and safe mobile radio wiring install. This will be for potentially 3 radios (future), 2 radios for now. I know that the way I have my radios wired now probably isn't the safest or most reliable way so I want to clean it up. The radios will be between 50 and 100 watts and I will only transmit on one at a time. I need the radios to operate off the ignition, I don't necessarily desire a timer but if it is required that's all the better. My wiring job right now consists of both radios spliced together and tied into an existing open ignition fuse using a fuse tap.

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I recommend taking a look around in the forums on RR to get ideas. You can try here Pictures Of Your Shack/Mobile Setup - The RadioReference.com Forums or here Radio Equipment Installation Forum - The RadioReference.com Forums. They're chock full of pictures and other information on various installations.

May I inquire: What is the year/make/model you're planning to install radios into? By knowing what your vehicle is, it will help myself and others in giving you suggestions and ideas beyond what the forums can provide. Thanks!

Colton25 · Jun 21, 2015

I guarantee its not like any others haha, it's a Pontiac g6. Like I said the radios are already installed in just looking for guidance on wiring them properly. I've read some say from the battery, some say from a fuse block.

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ka4gfy · Jun 21, 2015

Take a look at K0BG.com. Alan has some great ideas on installing radios. Its primarily about mobile antennas, but he also has sections on wiring and basic installations.

73,
Rich, KA4GFY

Colton25 · Jun 21, 2015

Thanks

ka4gfy said:
Take a look at K0BG.com. Alan has some great ideas on installing radios. Its primarily about mobile antennas, but he also has sections on wiring and basic installations.

73,

Rich, KA4GFY

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SteveC0625 · Jun 21, 2015

Most two-way radios have a main power input plus an ignition sense input. Generally, the +12vdc is connected to the + terminal of the battery with appropriate fusing per manufacturer's spec. The ignition sense line is connected to a run/accessory power source. +12vdc is the main power source; on many radios the fusing there is 15 amps or greater depending the specific radio. Ignition sense is usually fused at 1 to 3 amps max. In many cases, the radio has to be programmed to recognize ignition sense.

Minimum wire size is dependent on current draw and length of run. This is not the place to skimp. Wire that is too small for the power and distance gets hot and is a primary cause of vehicle fires. Again, the manufacturer's installation instructions should specify what's needed. If not, there are lots of wire size charts on the net to guide you.

The ignition control or run/accessory should be reserved for low current applications only. Adding 10 or more amps to a circuit that is controlled through the ignition switch is not a good idea. It's a recipe for blown fuses or worse.

Here's a fair example. My 25 watt Motorola CDM1250 came with a 14 AWG power cable that is 10 feet long. It's fused at 15 amps. If I were to locate the radio a bit further than 10 feet from the battery, I'd swap out the 10 foot cable for a 12 AWG or even 10 AWG cable of the appropriate length. The ignition sense wire can be as small as 18 or 20 AWG as long as the run is less than 10 feet. It's fused at 3 amps but actually draws less than one amp when in use.

You are asking questions which are generally answered in the manufacturer's installation instructions. There are a great number of threads here on RR about this exact topic with all kinds of detailed information about why one should wire main power direct to the battery and how to do it.

Colton25 · Jun 21, 2015

Can I use a RAP power source for the ignition sense cable? This way the radio will stay on when I take the key out of the ignition, and once I open the door the radio will turn off with all the other instruments powered with retained accessory power.

SteveC0625 said:
Most two-way radios have a main power input plus an ignition sense input. Generally, the +12vdc is connected to the + terminal of the battery with appropriate fusing per manufacturer's spec. The ignition sense line is connected to a run/accessory power source. +12vdc is the main power source; on many radios the fusing there is 15 amps or greater depending the specific radio. Ignition sense is usually fused at 1 to 3 amps max. In many cases, the radio has to be programmed to recognize ignition sense.

Minimum wire size is dependent on current draw and length of run. This is not the place to skimp. Wire that is too small for the power and distance gets hot and is a primary cause of vehicle fires. Again, the manufacturer's installation instructions should specify what's needed. If not, there are lots of wire size charts on the net to guide you.

The ignition control or run/accessory should be reserved for low current applications only. Adding 10 or more amps to a circuit that is controlled through the ignition switch is not a good idea. It's a recipe for blown fuses or worse.

Here's a fair example. My 25 watt Motorola CDM1250 came with a 14 AWG power cable that is 10 feet long. It's fused at 15 amps. If I were to locate the radio a bit further than 10 feet from the battery, I'd swap out the 10 foot cable for a 12 AWG or even 10 AWG cable of the appropriate length. The ignition sense wire can be as small as 18 or 20 AWG as long as the run is less than 10 feet. It's fused at 3 amps but actually draws less than one amp when in use.

You are asking questions which are generally answered in the manufacturer's installation instructions. There are a great number of threads here on RR about this exact topic with all kinds of detailed information about why one should wire main power direct to the battery and how to do it.

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SteveC0625 · Jun 21, 2015

zane018 said:
Can I use a RAP power source for the ignition sense cable? This way the radio will stay on when I take the key out of the ignition, and once I open the door the radio will turn off with all the other instruments powered with retained accessory power.

I'm not as familiar with RAP as perhaps I should be. What I do know is that some RAPs are done through a relay and others are straight from the BCM or PCM. What I've read so far suggests that you can do this if your RAP is a relay output. Relay controlled power generally can handle some variations in current draw which makes it ideal for things like low current ignition sense.

Where the RAP is direct from the computer, adding additional current draw (even just a half amp or so) can cause all kinds of issues in the vehicle.

Here's a good example, although not quite what you're working on. My F250 has current to the turn signals and reverse lights controlled though the PCM. Raising or lowering the current draw forces funky things like bulb out fast blink. But, the truck came with the towing setup so all the turn signals, brake lights, reverse lights, etc. are relay controlled out to the trailer connector. This allows me to tap the tow wiring as needed for things like turning on the aftermarket backup camera system automatically without confusing the PCM.

You'll need to do some research on your car or truck to find a relay controlled RAP.

Colton25 · Jun 21, 2015

Ok well they way I understand it the rap allows the power to remain on for 10 minutes after the key is taken out and/or if the door is opened. 10 minutes is ideal for me. I believe the source I'm using now for the radios is a RAP source so I would this if right now it is handling 2 radios it would be able to handle ignition sense. What do you think?

SteveC0625 said:
I'm not as familiar with RAP as perhaps I should be. What I do know is that some RAPs are done through a relay and others are straight from the BCM or PCM. What I've read so far suggests that you can do this if your RAP is a relay output. Relay controlled power generally can handle some variations in current draw which makes it ideal for things like low current ignition sense.

Where the RAP is direct from the computer, adding additional current draw (even just a half amp or so) can cause all kinds of issues in the vehicle.

Here's a good example, although not quite what you're working on. My F250 has current to the turn signals and reverse lights controlled though the PCM. Raising or lowering the current draw forces funky things like bulb out fast blink. But, the truck came with the towing setup so all the turn signals, brake lights, reverse lights, etc. are relay controlled out to the trailer connector. This allows me to tap the tow wiring as needed for things like turning on the aftermarket backup camera system automatically without confusing the PCM.

You'll need to do some research on your car or truck to find a relay controlled RAP.

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ke6gcv · Jun 22, 2015

I take power from the fuse panel under the hood. I follow the leader from the battery's positive terminal to there and connect. I would also use fuse taps on the inside fuse panel for the ignition sense; your car stereo is a perfect example of where to place a fuse tap. I think that may be just enough to not confuse the computer in your car and power down after 10 minutes. I definitely won't recommend tapping all three radios to one fuse.

Now... for Amateur Radio, most mobiles don't have an ignition sense wire. If this is your setup, then I would recommend a timer relay (SOLID STATE ON DELAY TIMER RELAY 12V 15A 0-10 MIN INPOWER - 75538). This is only an example as three radios is more than 15A combined, but you get the idea. That way you're still getting the power for that amount of time and can "walk away" and not worry about draining your battery as power would automatically shut off.

Keep in mind, using this type of relay you're looking at total shutdown of your radio equipment after 10 minutes until you turn your key on. In other words, you walk away from your car for 15 or so minutes and come back to turn on your radios, they may not power up until after you turn the key. Personally, I don't like using timers on my radios. I need them to be available at all times.

sfd119 · Jun 22, 2015

Get a Charge Guard by Havis. You can set the delay for on/off after the ignition...plus it offers Surge Protection, and Low Voltage shutoff.

KG7SPS · Jul 19, 2015

I've always run power to my radios through 30 or 40 heavy duty amp relays.

I place a STDP (on/on) switch to control power to the relay control terminal. The switch has one outer terminal going to an accessory power terminal/wire the other outer terminal to a constant on terminal/wire. The center terminal goes to the relay's control/power-on terminal.

The other two terminals on the relay go the battery and radio. This way you can have the radio go off with the ignition or stay on, with the flip of the switch.

Always use wire the same size as that used on the radio (or large, smaller number) , going to the battery and radio. Fuse both the positive and negative lines close to the battery. I also always run a ground strap from the radio to the automobile frame.

I use the higher rated relays so I can wire more than one device, radio, tablet for APRS position data and a small illuminating led fixed over the radio or control head.

G6GFA · Jul 20, 2015

I work in two way radio and therefore haven't used my amateur license for many years, however i do perform vehicle installations fairly often. We always take the main feed directly from the battery if at all possible as is will be the 'cleanest' supply on the vehicle. Most commercial radio equipment has an ignition sense input as previously mentioned which can usually be fed from the ignition feed to the stereo or the lighter socket if that's ignition switched. If no ignition sense input is available on the radio, the main feed can usually be switched with a suitably rated relay. Be sure to fuse the ignition sense and fuse the main battery leads right at the battery. One thing people often neglect is to fuse the negative feed too. This may sound odd but if the vehicles main battery earth lead goes high resistance or comes loose then the only path from the battery's negative terminal to the vehicle chassis will be through the radios negative power lead and down the braid of the coax. This will likely catch fire or at least cause serious damage when cranking the engine if its not fused.

Project25_MASTR · Aug 5, 2015

G6GFA said:
I work in two way radio and therefore haven't used my amateur license for many years, however i do perform vehicle installations fairly often. We always take the main feed directly from the battery if at all possible as is will be the 'cleanest' supply on the vehicle. Most commercial radio equipment has an ignition sense input as previously mentioned which can usually be fed from the ignition feed to the stereo or the lighter socket if that's ignition switched. If no ignition sense input is available on the radio, the main feed can usually be switched with a suitably rated relay. Be sure to fuse the ignition sense and fuse the main battery leads right at the battery. One thing people often neglect is to fuse the negative feed too. This may sound odd but if the vehicles main battery earth lead goes high resistance or comes loose then the only path from the battery's negative terminal to the vehicle chassis will be through the radios negative power lead and down the braid of the coax. This will likely catch fire or at least cause serious damage when cranking the engine if its not fused.

You'll get two solutions in that situation. One will be either dual fuses or run the negative lead to chassis instead of the negative post (assuming negative ground). Personally, I'd rather omit the negative fuse and run to chassis in the off case the negative fuse pops but the positive fuse does not since most modern radios do not have the antenna ground isolated from negative ground.

As far as RAPs goes, best place I can think of to pull it off a GM vehicle is off of the radio ignition (I believe there is a low amperage fuse for it in the distribution block that can be tapped).

Professional mobile wiring help.

Colton25

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SteveC0625

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