When trying to shop for a marine VHF antenna, it is crucial that you look into its gain, size, and cost if you want to find something with good value.
The type of antenna you need to look for would be depending upon the cost, your physical requirements, and desired distance. It is important to find the right kind of marine antenna because it’s your only key to obtaining good VHF coverage.
If you have a top-of-line radio, which is also expensive at the same time, it is of no use and no value if there is no way for you to use it with a good and functioning antenna. You also have to consider the antenna’s height above the water. The higher your antenna gets, the stronger, more powerful range of coverage that it has.
VHF radio signal is known to travel in a straight, linear path. Hence, this kind of signal travel path is sometimes referred to as line-of-sight.
With regard to its coverage, it tends to get affected by the natural curvature of the earth or if there is any kind of obstruction between the 2 radios, it tends to get in the way of the signal. Thus, causing signal interference or disruption.
Efforts made by two stations that are trying to make a connection and communicate with each other will be in vain if one or both of them fall below the horizon.
If that happens, then they can’t “see” each other, thus no connection would be established. Due to the natural curvature of the earth, VHF communications best scenario would be limited to 40-50 miles.
When it comes to the VHF antenna range, height is a major consideration. With regard to sailboats, it is easy to obtain a better range for them and you are likely to achieve this when you mount your antenna at the topmost part of the mast, provided, of course, you are using a proper antenna.
You can calculate the range of the antenna by using the following formula:
Range in Miles = height above the water or its square root x 1.42
Consider taking into account the following antennas. Keep in mind that we consider range as an additive, and would be depending upon the other station’s antenna height. If you have a 3-foot antenna, you can anticipate that it is capable of yielding a 2.5-mile range. But if the station happens to have a minimum of the 3-foot antenna, then it is safe to say that it can yield 2.5 miles with a total communication range of 5 miles.
Ant Height Range
- 3 foot 5 miles
- 5 foot 6.3 miles
- 10 foot 9 miles
- 20 foot 13 miles
Height = Immediate Height Above Water + Antenna Height
As of today, the center of concern is from ship to ship. Communication with a coastal station can be further enhanced and this is possible if you will make the antenna nestled at a very high location.
Installing an antenna at around 1000 feet will probably fetch for it an average range of 45 miles sans any kind of obstacles but inclusive of the ship antenna’s height.
The design of an antenna itself can be taken advantage of to provide gain to the radio since it can work both for transmitting and receiving. By law, a marine radio would be limited to a transmit power of 25 watts. In that case, how can range go to increase by virtue of gain?
The antenna does not have any capability to increase the power being fed into it. What it usually does is manipulate that power and focus it.
The impact of which is that the marine antenna takes on the power that is heading itself straight up in the air. It will then be focused toward the horizon. Similar to a balloon, its natural tendency when you smash its side is to expand.