In the M-1 zone, devices which radiate radio frequency energy shall be so operated as not to cause interference with any activity carried on beyond the boundary line of the property on which the device is located. "Radio frequency energy" means electromagnetic energy at any frequency in the radio spectrum between ten (10) kilocycles and three million (3,000,000) megacycles. (Ord. 1000 § 28.30(B), 1955)