A Primer on VHF Antennas for Marine Vessel Applications

Finding the right kind of marine VHF antenna to use for your vessel and maybe for other specific needs you have is much easier and seamless if you understand the characteristics that you need to look for in a good antenna. By this measure, you also get more value from your money.

Before anything else, we’ll define first what an antenna is all about. From here, we can move forward. So, what are antennas?

Antennas are qualified devices that are capable of taking in oscillating electric current and radiate the energy out in the form of electromagnetic radiation and vice versa. In simple words, these pieces of equipment are made to help in transforming electric power into radio waves.

Characteristics of Marine VHF Antenna

The whip antenna is, by far, the most commonly used VHF marine antenna by the majority of private shipping vessels today. The proper structure and functioning of an antenna are determined by the following:

  • Frequency of use
  • Efficiency 
  • Directivity
  • Bandwidth
  • Gain
  • Polarization
  • Radiation pattern desired
  • Antenna temperature 

This list is not at all exhaustive but just a few of the involved parameters. It is far too obvious to see that the VHF antennas theory is going beyond the average needs of a mariner in as far as choosing the right kind of antenna for their vessel is concerned. So what we can do here is to neutralize everything down and become a bit simplistic.

Polarization and Radiation Patterns

In general, polarization can be classified into 2 types: Circular and Linear. With respect to the mobile type of communications, what is most commonly found in the linear polarized antenna?

Within those antennas that are linearly polarized, you can have both a horizontally and vertically polarized. When it comes to the linear polarized antenna, it tends to radiate entirely in one plane, the direction of propagation.

Antenna Gain

The best definition we can give for antenna gain is that it is the sum total of directivity and efficiency. For those who are considering themselves as non-technical in the field of antenna theory, antenna gain is the stated power increase made readily available by the antenna itself.

In plain language, this has something to do with the antenna’s relative measure on its ability to center or direct radiofrequency energy in just one particular manner or fashion. This measurement is gauged in dBi (Decibels in connection with the isotropic radiator) or dBd (Decibels in comparison with a dipole radiator). But in the majority of specifications for the VHF marine antenna, it will be stated only as dB gain.

Producing an isotropic radiator is nearly impossible. Nonetheless, the 0dB theoretical antenna is often seen as a starting point in the criteria for antenna design as well as for antenna gain measurement baselines.

Conclusions

Perhaps what you have in mind right this very moment is: I would get myself a 9dB gain antenna because it is going to give me  more reliable and better communications even at longer distances.

The best thing we can advise you in this regard is to slow down first. Higher gain is not always a guarantee that it will always be your best choice.

We need to make some clarifications here. The maximum communication range is not likely to be impacted by the sudden surge in antenna gain. If the antenna on the shipping vessel you are trying to communicate with is not seeing or detecting your own ship’s antenna, communication is not likely to happen. Regardless of what VHF antenna gain you have, it is not going to affect any change to that.