Wireless Technology

A Primer on VHF Antennas for Marine Vessel Applications

marine vessel antenna

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.

Who Needs a Good GPS Antenna for Their Car?

Mobile Home Automotive Van Technology

When it comes to external GPS antennas that are naturally equipped with an in-dash navigation receiver, there are a few simple guiding rules to follow during their installation. Topping the list here is that you should not make any attempt to modify or cut the antenna in any way. Second, it is a cardinal rule that they remain perpetually connected to the GPS satellites that are orbiting the earth. This is the reason why you must mount them to your car in such a way that there is not going to be much signal interference.

Most of the time, GPS antennas can be mounted on the topmost part of your dash (above or behind the receiver). Nowadays, it is safe to say that satellite signals are more reliable and stronger than ever and this should be more than enough for these antennas to maintain good reception. It is also helpful in keeping the GPS antenna for the car out of sight.

10 Best GPS Antennas 2019

The vast majority of technicians recommend mounting GPS with antenna either along the rear deck or on the dash itself. Provided that it is not in close range to a 2-way antenna or A-pillars and has a clear path to the sky, it should work okay and good.

Under the following conditions, you will want to mount your antenna on your vehicle’s exteriors:

  • Your car/auto does have a wired rear defroster
  • Your car or auto does have metallic window tint
  • Your car window is a solar reflective type 
  • You radio antenna have a windshield-mounted 

If your GPS for car antenna comes with an attached metal sheet or plate, you must ensure that they have a solid connection and are as level as possible. Normally, there is some kind of adhesive solution used here just so the antenna will remain in place. You will need to route your GPS antenna car wire along with your dashboard rear receiver, or through a door seal or window, whichever is most practical and applicable.

Wired Connections

Receivers equipped with a video screen need to have a couple of additional wire connections that are not necessary for non-touch screen stereos. Let us delve deep into some of them here.

Parking brake wire connection

For safety concerns, if the front of the car is equipped with a video screen you must see to it that it is connected to the parking brake wire. The same thing is also applicable to GPS systems. While the vehicle is in motion, some of these advanced navigation functions will be deactivated.

Say, for instance, you want to search out a particular phone number, or that you want to make some tweaks on the unit’s default settings, the first thing you need to do is to pull over. Foot brake connection may be necessitated but this doesn’t happen very often. 

car GPS antennas
Best GPS antennas

Amplified Against Passive GPS Antennas

There are two classifications for external GPS antennas, they are either amplified or passive antenna. If they only receive GPS signals and transmit this to a GPS navigation device, we qualify them as passive. The active ones come with a powered-up amplifier which helps give a boost to the signal power. 

Compared to a passive antenna, the active type of antenna comes with more installation challenges and a bit more expensive, too. Besides, you can also have it installed at a greater distance from your GPS. Most of the time, a passive antenna must be installed using a coaxial cable that is no more than 3 feet. Active antennas work better with larger vehicles since you can install them further away.