High gain antenna @ coaxial cable (about 20 meter / 60 feet) The optional 6 db External Antenna for the Engenius 1X or 4X long-range Industrial Cordless Phone System makes effective outdoor cordless phone operation a viable resource for industrial parks, farms, construction sites, auto dealers or other demanding campus environments. The ULTRA-AK20 includes 60 feet (20 meters) of coaxial cable and can be used with any SN-920 ULTRA base unit. The rubber antenna on the base unit is replaced by the external antenna coaxial connector. Installation of the EnGenius ULTRA-AK by an professional radio antenna installer is recommended. NOTE: One antenna is required for each base unit installed. Tech Note: While there is a 6db gain in the antenna, the 60' Coax cable has a 3db loss, resulting in 3db gain at the antenna. The range of the SN-920 is extended, with proper installation, due to height and positioning. However, the 30' cable kit is rated at a 0db loss which results in maintaining the 6db gain at the antenna, thus providing the maximum output and range. When using either of the cable kits do not leave excess cable coiled up (stretch it out) as this will also cause loss in performance.