When choosing a VHF antenna mount, a balance between size, gain and cost are required. The type of antenna mount depends on the desired distance, physical requirements and cost. An antenna is key to obtaining good VHF coverage. An efficient radio needs to be complemented with a good quality antenna. An important consideration is the height of the antenna mount over the water. The higher the antenna, the greater the range or coverage. The VHF radio travels in a straight line and is called a line of sight. The coverage is affected by the curvature of the earth and any obstacle between the two radii. Two stations that try to communicate with each other cannot do so when both fall below the horizon and cannot be "seen" by one another. Due to the curvature of the earth, VHF communication is usually limited to 40-50 miles at best.

Since height is an important factor in the range, sailboats can obtain a considerably better range by mounting the antenna on top of the mast with the proper antenna. Small boats are often only a few feet from the water and it is not practical to mount a tall antenna.

The range of an antenna can be calculated by the formula:

Range in miles = square root of height above water (in feet) by 1.42.

Consider some of the following antennas. Note that the range is addictive and depends on the antenna height of the other station. A 3-foot VHF antenna mount will produce approximately 2.5 miles of range. However, if the other station also has a 3-foot antenna, you can also see 2.5 miles and the total communication range would be approximately 5 miles.

So far the consideration has been mainly from ship to ship. The communication with a coastal station usually improves a lot since the coastal station, like BoatUS, has its antenna in a very high location. An antenna at 1000 feet has a range of 45 miles without obstacles plus the height of the antenna of the ship.

A VHF antenna mount can be ideal for both transmitting and receiving signals. A marine radio is, by law, limited to 25 watts of transmission power. So, how is the increase in rank by profit? The antenna cannot increase the amount of energy that is fed into it. An antenna manipulates the power and focuses it. In effect, a marine antenna takes the power that goes up in the air and focuses it towards the horizon. Like a balloon, if you crush it, the sides expand.

Another consideration is the coaxial cable and the connectors. All coaxial and connectors have a certain amount of loss. This loss can be found in the specifications of the coaxial cable and is in decibels. Contrary to the effective gain of the antenna, the coaxial cable is measured in a loss in DB normally by 100 feet. Therefore, a piece of 100-foot coaxial cable with a loss of 3db over that cable length would lose half the power placed on the line. 25 watts of power placed on a 100-foot piece of coaxial cable with a loss of 3db per 100 feet would have 12 watts at the antenna output.

However, a typical coaxial cable run is 10 to 20 feet in a boat, so the loss is not a big problem. However, a sailboat could have a much longer run and should consider the type of coaxial cable used.

There is almost always a commitment to get the best rank verses that can be best mounted on a boat. Consider what the majority of your radio requirements will be.