23 GO FURTHER WITH AWARD - WINNING ANTENNAS MARINE VHF, SSB, AM/FM, XM, WIFI & CELLULAR ANTENNAS
YOUR ANTENNA IS YOUR LIFELINE … CHOOSE WISELY!
Which antenna is right for you?
Voted ‘Best Marine Antenna’ by the National Marine Electronics Association (NMEA). Customers rely on Digital Antenna for quality design and ultimate performance. All antennas have soldered connections, are hand-assembled and tuned for maximum gain then finished with a high-gloss urethane coating, resulting in a product that consistently outperforms the competition even in the harshest of marine environments.
What type and length of boat do you have (sailboat, powerboat, yacht, commercial vessel)? Choose an antenna based upon available mounting location. A 4’ or 8’ antenna works well for many applications including a T-top. Larger antennas such as 16’ models must be side-braced approximately 3’ to 4’ from base. Is your antenna for communication, navigation or entertainment? Although antennas look identical, they are very different inside. Each antenna is designed and manufactured for specific frequencies. VHF: 156.8 MHz, Cellular: 800/850 & 1900 MHz, SSB: 2-30MHz, AIS: 159 MHz. The correct antenna must be matched to the equipment’s frequency. What is ‘gain’ in an antenna? Gain is measured in decibels (dB). The illustration to the left shows the radiation pattern of three antennas with different gain. As gain increases, the more directed the RF energy becomes, resulting in reaching a greater distance. Your antenna choice should be based upon your application, taking into consideration the rocking or keeling of your boat. Why does an 18” cellular antenna have 9dB gain and an 8’ VHF antenna have 6dB gain? Due to the physics of the signal’s wavelength, an equivalent 9dB gain antenna for VHF would have to be almost 16’ in length. The wavelength for cellular frequencies is much shorter than VHF. How does line-of-site affect communications? While lower frequencies (SSB) allow for reliable long-range communication, frequencies above 100 MHz do not follow the curvature of the earth and are limited to line-of-site (the antennas must “see” each other). To achieve the longest range, The advanced ground system internal to all Digital Antenna marine antennas allows 4.5dB through 10dB gain antennas to have a greater range in any sea conditions. The figure to the left shows the effect that a ground system has on a vertical antenna. Note that by increasing the ground system efficiency, useful RF power is actually directed closer to the water surface where it is needed. Most well designed 5/8 wavelength 6dB antennas will transmit the same distance in the sky; however, the ground efficiency determines the actual communication range at sea level. the antenna should be placed as high as possible. What makes an antenna reach a greater distance?
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