This is a simple handheld radio addon created for the Dimensional Ascension modpack. It is an addon for the Simple Voice Chat mod.
Use the keybind or right click with the radio in your hand to speak over a radio's frequency. The keybind will look for the first radio in your inventory, starting with your hotbar and then going left to right, top to bottom.
If you want an updated or more feature-complete version of a radio mod, check out CodinGlitch's Simple Radio for 1.20.X.