Digital Yacht - Commercial AIS/VHF Antenna - 4' - CX4A. Powerful AIS Tuned commercial VHF Antenna that will give you maximum AIS range. Has an SO239 antenna connector in the base of the Antenna and we recommend using this with low loss 50-ohm coax cable such as RG-213 for best performance (not supplied), particularly on long cable runs.. A very high-quality 3dB AIS tuned GRP antenna which is ideal for professional and superyacht installation.. Specifications:. 3dB AIS tuned GRP antenna. Size - 4ft long. Fit 1.25" commercial grade fixing bases