1) Extremely high frequency 2) Radio frequency 
(from the article `telecommunications media`) ...Today, civilian radio signals populate the radio spectrum in eight frequency bands, ranging from very low frequency (VLF), starting at 3 ... ...band undergo high penetration losses as they propagate through the exterior walls of buildings. Because of the severe atmospheric attenuation, an...
abbreviation: extremely high frequency (30,000 to 300,000 MHz)
Extremely High Frequency (30 GHz to 300 GHz)