In the A-D zone, devices which radiate radio frequency energy shall be so operated as not to cause interference with aircraft, electronic navigation and communication equipment, or any activity carried on beyond the boundary line of the property on which the device is located. "Radio frequency energy" is electromagnetic energy at any frequency in the radio spectrum between ten (10) kilocycles and three million (3,000,000) megacycles. (Ord. 1000 § 31.54(B), 1955)