The SHF band has been selected for Airfield Surface Movement Indicator (ASMI) radars in preference to the EHF band because:
the EHF band causes unacceptable radiation hazards to personnel.
the attenuation caused by precipitation is greater in the EHF band and reduces the radars effective range and usefulness.
the EHF band is not suitable for the provision of the very narrow beams needed for an ASMI radar.
target discrimination using the SHF band is better.