Airband

These are reserved for navigational aids such as VOR beacons, and precision approach systems such as ILS localizers.

Some channels between 123.100 and 135.950 are available in the US to other users such as government agencies, commercial company advisory, search and rescue, military aircraft, glider and ballooning air-to-ground, flight test and national aviation authority use.

A typical transmission range of an aircraft flying at cruise altitude (35,000 ft (10,668 m)), is about 200 mi (322 km) in good weather conditions.

Military aircraft also use a dedicated UHF-AM band from 225.0 to 399.95 MHz for air-to-air and air-to-ground, including air traffic control communication.

[13] Eurocontrol's "8.33kHz Voice Channel Implementation Guidelines" document provides recommendations regarding institutional provisions, flight planning, operational procedures, aircraft retrofit, safety, frequency management and State’s management aspects for the deployment of 8.33kHz channel spacing communications.

Even if both transmissions are received with identical signal strength, a heterodyne will be heard where no such indication of blockage would be evident in an FM system.

[17] Alternative analog modulation schemes are under discussion, such as the "CLIMAX"[18] multi-carrier system and offset carrier techniques to permit more efficient utilization of spectrum.

A switch to digital radios has been contemplated, as this would greatly increase capacity by reducing the bandwidth required to transmit speech.

Other benefits from digital coding of voice transmissions include decreased susceptibility to electrical interference and jamming.

The change-over to digital radio has yet to happen, partly because the mobility of aircraft necessitates complete international cooperation to move to a new system and also the time implementation for subsequent changeover.