Mobile Installs

Installing a GMRS mobile radio in your vehicle gives you significantly more range and power than a handheld — typically 15-50W versus 2-5W. A proper installation makes the difference between a radio that works reliably and one that causes problems.

Mounting the radio

GMRS mobile radios are compact enough to fit in most vehicles. Common mounting locations:

• Under the dash: out of the way but still accessible. Use a mounting bracket attached to existing bolts or a sturdy surface. Keep it away from the driver's legs
• Center console: convenient for reaching controls. Ram mounts and similar systems work well for this
• Under a seat: completely hidden, with just the microphone visible. Some radios have detachable face plates that can be remotely mounted

Power wiring

This is the most important part of the installation. A mobile radio drawing 10+ amps on transmit needs a direct, heavy-gauge connection to the battery.

• Use the power cable that came with the radio — it's sized for the correct current
• Run the positive wire through the firewall using an existing grommet or rubber pass-through. Don't drill through the firewall if you can avoid it
• Install an inline fuse holder on the positive lead, as close to the battery as practical
• Connect the negative lead to the battery negative terminal or a solid chassis ground point
• Keep power wires away from spark plug wires, ignition components, and the alternator

Antenna options

• Magnetic mount (mag-mount): sits on the roof with a magnetic base. No drilling required. Good for temporary or rental vehicles. The magnet provides the ground plane. Remove it when going through car washes
• NMO mount: a permanent mount that requires drilling a 3/4" hole in the roof. Best performance because it provides the best ground plane connection. Professional-looking and weatherproof once installed
• Lip mount / trunk mount: clamps to the edge of the trunk or hatch. No drilling, but the ground plane is compromised. Performance falls between mag-mount and NMO

Routing the coax

Run the antenna cable from the roof down through the door jamb or a rear corner, then under trim panels to the radio. Avoid sharp bends, pinch points, and areas where the cable could be damaged by moving parts. Use cable ties to secure the run and keep it tidy.

Grounding considerations

In a vehicle, the metal body acts as your ground plane and antenna counterpoise. For best performance, make sure the antenna mount has a solid electrical connection to the vehicle body. Mag-mounts achieve this through the magnetic base. NMO mounts achieve it through direct metal-to-metal contact with the roof. If you're getting excessive noise on receive, check that your power supply ground is solid and consider adding a ground strap between the radio chassis and a nearby body bolt.

For more on antenna selection, see Antenna Basics.