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Marine Radio Antenna Basics


A Marine Radio is only as good as its antenna

Knowledgeable boaters realize that even the most expensive radio will perform poorly with a second rate antenna that saves money up front. A quality antenna is the crux of reliable performance in any marine radio. From the largest seagoing ships to the smallest bass boats, Shakespeare antennas have held up for years under the worst marine conditions, always performing to their maximum design capabilities.

Reliability Begins with Quality Construction

Shakespeare fiberglass antennas are built with precision, beginning with hand-soldered connections, brass and copper elements, strong mechanical joints and superior electronics. The radiator and electrical elements are then encased in an exclusive Shakespeare fiberglass radome.

TIPS ON CHOOSING THE PROPER ANTENNA

Since there are many factors that influence the selection of a proper antenna for a specific application, we encourage consultation with a local dealer. When this is not possible, the following tips should be considered before making a final decision.

Antenna Length

Height is paramount in getting the greatest range, and encourages the choosing of an antenna that can be placed as high as possible on the boat.

Sailboats: As a general rule, sailboats have a 3' - 5' antenna mounted on the masthead. Some racing enthusiasts opt for an 8' antenna mounted on the stern in the event demasting should occur. Either is acceptable. A decision should be made on personal preference.

Powerboats: Most power boats from 16' to 25' in length use a standard 8' antenna, while bigger vessels have the option of larger antennas with more gain. Caution: be sure to allow enough lay down room for clearing low bridges or other limitations. Whichever choice is made, a sturdy mounting arrangement must be used to avoid damage to both boat and antenna.

Gain is a common term used to measure the transmitting distance of any antenna. The short sailboat whip antenna is said to have a 3 dB gain. A longer antenna that is mounted at equivalent height can have higher gain, between 6 and 9 dB. The higher "gain" simply means a more focused area of transmission, or tighter beam, that results in longer transmissions with less wasted power. This is ideal for stable powerboats on calm seas. Sailboats require a lower gain, (3 dB) that transmits a shorter distance but in a wider oval to compensate for heeling angles. The elevation of the masthead mount alone allows for excellent transmission distance.

Mounts

Be sure to pick the mount style that will best support the antenna on a particular boat. When using a two-piece antenna system greater than 10' in length, an upper support clamp is necessary. For antennas of 14' to 18', the upper clamp should be 3' to 5' from the bottom. For antennas of 18' to 23', the upper clamp should be 4' to 8' from the bottom. Positioning the upper clamp too high or too low can significantly increase the potential for structural failure.

Cable

RG-58 cable is sufficient for cable runs up to 20'. For runs over 20', larger and better, low loss RG-8/X, RG-8A/U or RG-213 are preferable. Shakespeare uses low-loss, UV stable RG-8/X throughout its Galaxy antenna line. Today's enhanced cellular services, which operate in the 1800-1900 MHz range, place even more importance on using a high quality coax. That's why Shakespeare developed its exclusive coax cables for dual band cellular antennas.

For optimum performance from your VHF, HF/SSB and cellular communications systems, the cable should be kept as short as possible. Caution: cable supplied with some antennas may not be cut or altered. Be sure to check the instruction sheet before attempting to shorten the cable.

Low Angle Radiation

Shakespeare pioneered low angle techniques in marine antennas in the 1960s and built them into many models. Low angle minimizes fading while maximizing range even during excessive boat roll in turbulent seas. A normal angle shortens the range and wastes power.

antenna gain radiation pattern illustration

A FINAL WORD

The greatest tip to keep in mind is that no matter how much you pay for your radio, its performance will be directly proportional to the quality and performance capabilities of the antenna. Don't compromise... Insist on genuine Shakespeare.



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