If you have a VHF Radio in your truck with an antenna for your Garmin, you should keep one of these Radio adapters in your truck.

This is a simple adapter that allows you to connect your Garmin® Astro, or Garmin® Alpha truck antenna to your radio. It's very simple to use and we recommend you keep one of these products in your vehicles glove compartment should you run into a situation that you need to connect your radio.

Garmin Astro, and Garmin Alpha antennas for the 220's 320's and Alpha 100