Antenna farm on a super yacht. Photo By Glenn Hayes
Antenna farm on a super yacht. Photo By Glenn Hayes

Choosing a VHF Antenna

Selecting a VHF antenna is not just a matter of picking the cheapest or best looking antenna at the local marine store. Performance can vary drastically and by acquiring a basic knowledge of how it works you can improve your VHF reception and transmission and end up with the best antenna for your application. There are many sizes and types of VHF antennas on the market offered by a handful of manufacturers. Prices range from less than $50 to hundreds of dollars. Selecting the right one is not as difficult as one might think if you take how they work and the components they are made of into account.

The first factor to recognize is all VHF transmissions and receptions are line-of-site. In other words, wherever the top of the antenna can see is where it can transmit to. Unlike Single Side Band radios, or other radio frequencies whose transmissions can follow the curvature of the earth, a VHF transmission radiates out and along a more horizontal path. As a result the higher the antenna is placed, the more effective the range. Studying your vessel and seeing the highest point that you can effectively and safely mount your antenna should help you increase your transmission rage. If you are on deck with a handheld VHF with a stubby antenna you will not get the same range as talking through a fixed mount radio with an eight-foot antenna mounted to a hard top. Likewise a sailing vessel with a three-foot antenna mounted to a mast top should be able to have increased range over the powerboat with the eight-foot antenna.

The dB rating of the antenna also plays a factor in its effectiveness. Also known as antenna gain the dB rating put simply will indicate how focused the energy is coming out of the antenna. A higher rating will indicate a more concentrated energy transmission, while a lower rating will indicate a more radiated pattern. Think of dB as a spotlight or a floodlight. A higher dB is the spotlight and the lower dB is the floodlight. For example, the three-foot whip antenna on the sailboat mast will transmit with a 3 dB gain while the eight-foot antenna on the powerboat transmits at a 6 dB gain. As the height of the antenna increases so does the dB gain. One would think that a more concentrated energy pattern would be better for longer range communications but it is important to remember that as the boat pitches and rolls that concentrated signal may be directed up into the sky or down into the water. We have all heard this happen on the VHF when we only hear every other word of a choppy transmission. Because of this, sailboats, for example, should usually go with a 3dB antenna for the best compromise between height and gain.

Internal and external components of antennas also play a factor in their effectiveness and the quality of transmission and reception. The internal elements inside the antenna have a direct correlation as to how well the antenna can transmit and receive. Cheaper antennas may have nothing more than a fixed length of stripped-down coaxial cable held in place with foam inserts, while better quality antennas have a single brass radiator or twin brass and copper radiators (rods that run the length of the antenna). The ferrule or base of the antenna that attaches to the mount is also an important consideration. Nylon or plastic ferrules are not as strong or long-lasting as stainless ones and will get brittle and break over time when stressed. The type of coaxial cable that is attached to the antenna and runs to the VHF is also important to consider. RG8X is thought to be a premium cable with positive characteristics and is generally a better cable than RG58 cable found on less expensive antennas. The PL259 connector that goes on the end of the cable attaching it to the radio is also an important feature. It is critical that this connector is soldered or attached correctly, thus creating a good connection between the radio and antenna. Many times radio transmission issues end up being a poor connection at this point, so be aware and make a good connection.

One feature of better quality antennas that doesn’t affect the ability of the antenna to perform but is a nice feature to consider is a high quality urethane coating. We have all grabbed an old antenna at some point that did not have this feature and were probably picking out fiberglass shards from our hands.

It is important to remember that you may own the latest and greatest VHF offered today but if your antenna or any of its components are not of a decent quality or the right type for your application you will not be happy, so do your homework and don’t go for the cheapest antenna on the shelf.

 

Glenn Hayes is a freelance photographer and writer living in West Central Florida. Specializing in marine and location photography his work covers commercial, editorial and fine art work. www.HayesStudios.com

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