PHASE III 6018 18'4 VHF ANTENNA 9dB GainCollinear-phased 1/2-wave elements with choking sleeveGood communication over the VHF Marine Band depends on antenna height, quality, and dB Gain. This sophisticated Phase III powerhouse brings all that to your boat, in a rugged, high-strength fiberglass radome for stability in high seas, high winds, and high speed.Silver-plated outer conductor, copper inner conductorStainless steel mounting sleeveType N connector inside mounting sleeve for easy mounting and dismounting for stowageSuggested Mount: Shakespeare Style 409-R or 410-R Mounting KitTwo sections: Base 110 , Tip 110 Max. Power Input: 150 wattsSWR: Less than 1.5:1 at 156.8 MHzBandwidth: 3 MHz within 2.