ADS-B operates on two frequencies: 1090 ES or 978 UAT. Going 1090-ES means your looking to replace your Mode C transponder for an ADS-B (Mode S) capable one that will interface to your GPS/WAAS navigator or have built-in GPS in the transponder. If you choose to go 978 UAT, there are many options that allow you to keep your current transponder while adding a data-link ADS-B solution; these options rely heavily on the state of your transponder. It is recommended to consult with us before deciding if UAT is the solution for you.