Product Description RG-59 is a specific type of coaxial cable, often used for low-power video and RF signal connections. The cable has a characteristic impedance of 75 ohms. The 75 ohm impedance matches a dipole antenna in free space. RG (for radio guide) was originally a unit indicator for... Product Description RG-59 is a specific type of coaxial cable, often used for low-power video and RF signal connections. The cable has a characteristic impedance of 75 ohms. The 75 ohm impedance matches a dipole antenna in free space. RG (for radio guide) was originally a unit indicator for bulk radio frequency (RF) cable in the U.S. military’s Joint Electronics Type Designation System. The suffix /U means for general utility use. The number 59 was assigned sequentially. The RG unit indicator is no longer part of the JETDS system (MIL-STD-196E) and cable sold today under the RG-59 label does not necessarily meet military specifications.