Marine VHF Antenna

Antennas can be of many different types. The type of antenna to get may depend on the distance through which the transmission is expected to take place. It is important for boats and ships to have some form of communication with land or with other vessels, and thus the use of antennas are crucial to enable such communications. Marine antennas are those that are used to signal for help or for other activities when out at the sea.

An antenna is a device that transforms radio signals in the air into electricity. Usually in the form of a long pole, an antenna can also transmit electronic signal in the air. The distance through which transmission takes place depends on the amount of power running through the antenna. It also depends on the type of antenna, or the specific function that it is designed to provide. For example, the antennas installed by NASA are extremely powerful and can receive signals even from the Mars Rover.

Selecting the right antenna is necessary for a marine radio to function at its best. Two important criteria to consider when buying antenna are the antenna length and its gain. VHF (Very High Frequency) radio waves travel in straight lnies, called the line-in-sight. The other antenna which is expected to send or receive the signal should be visible. Thus for marine antenna, it is necessary for the antenna to be considerably higher than the water level in order to achieve maximum coverage. It is important to calculate the range in miles required when at sea, which can be done by calculating the square root of the heigt above water (in feet) times 1.43. Mounting an antenna in the sailboat or ship’s mast is a good measure to ensure maximum exposure.

The ‘gain’ of an antenna is the ‘perceived’ increase in energy that the antenna controls and focuses in certain directions. The measure of the gain is expressed in decibels, or dB. A 9dB antenna boosts the signal power eightfold while a 6dB antenna increases power sixfold. The most common antenna for sailboats and masthead applications is a 3dB aantenna that doubles the signal power. Because of the radio pattern in a 3dB antenna, there is a portion of signal that is always looking at the horizon, thus making it effective for use in boats. Standing Wave Ratio (SWR) is another measure to be considered when buying antennas. SWR is a measure of the lost transmission power in the antenna. A 1:1 ratio is ideal for any antenna system, but is not obtainable in real life situations.

Other important criteria to consider are the susceptibility of the antenna to UV degradation; resistance to attacks or strikes by sea birds; low weight and sturdy mount constructions. There are three kinds of mounting for antennas. These are rail mounting, surface mounting and mast mounting, amongst which mast mounting is more sutiable for sailboats. Using good quality connectors and coaxible cables are aslo important in order to get the best out of the antenna.
However, a combination of antennas should be used to detect signals of various frequencies effectively.

Amongst the number of VHF marine antennas available in the market, the most sought after and popular ones are those made by the brand called Shakespeare. Metz VHF antenna is also popular when it comes to marine VHF antennas. The U.S Navy and Coast gaurds rely on Shakespeare and Metz antennas for its antenna engineering technology. The prices of these antennas vary from $20 all the way to $170, depending on the length and gain factors, and a number of other determinants.

A good antenna is required for the radio to work properly at a distance, and therefore investing in antennas is as important as is buying an effective VHF radio system. It should be noted, however, that the necessity of correct cables and well made connections are important as well to achieve a good radio signal system.

This Marine VHF Antenna Review is Written/Updated on Sep 4th, 2010 and filed under Consumer Electronics. Both comments and pings are currently closed.

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