The ZM21-VHF marine VHF deck mount antenna is suitable for marine vessel VHF communications within the 156-162MHz frequency range. The ZM21-VHF requries a MM1 white nylon fold-down base or MM2 stainless steel fold-down base. ZCG recommend mounting the ZM21-VHF as high on your vessel or structure as possible to ensure a true omni-directional pattern.FREQUENCY Marine VHF 156-162MHz. Height: 2.2m