Each FIA on a map has its own radio frequency as shown on the map below. Class E above 8500ft uses 134.2 while Class G below 8500ft uses 122.4 . *Class G airspace has different rules and procedures depending on your altitude: Below 3000 feet and above 3000 feet clearance from cloud requirements change.

Class E airspace in the United States does not have a single, universal "radio frequency" for all users, as it is controlled airspace that functions as a "fill-in" for the National Airspace System. For IFR (Instrument Flight Rules) aircraft, the frequency used is the designated Air Route Traffic Control Center (ARTCC) or "Center" frequency for that specific sector. For VFR (Visual Flight Rules) pilots, there is no requirement to communicate with ATC while in Class E unless they are requesting "Flight Following" or transitioning near a busy airport. In the context of modern surveillance, Class E is a primary zone for ADS-B Out equipment, which operates on 1090 MHz (for high-altitude aircraft) or 978 MHz (for Universal Access Transceivers). If a pilot is operating at a non-towered airport within Class E, they would use the CTAF (Common Traffic Advisory Frequency), typically found between 122.7 and 123.05 MHz, to broadcast their intentions to other local traffic. Essentially, the frequency depends on your flight plan and specific geographic sector rather than the airspace class alone.