Which is the best placement of a VHF aerial?

Antenna placement:

Your VHF antenna attached to the AIS device needs to be as high as possible and as far away as possible from other vertical metal objects. Vertical metal objects include other vertical antennas, sailboat masts, radar masts, stays, bimini frames and any other lengths of metal parallel to the antenna.

Where do you mount a VHF antenna?

For instance the VHF radios have highly magnetic components and can drastically deviate your compass. For best performance, mount your antenna at the highest point on your boat. T-tops make excellent places to mount antennas.

Does a VHF antenna need to be vertical?

No matter how tempting it might be to angle your boat's VHF antenna for aesthetic purposes (like matching the angle of fishing rods), don't do it. Sure, it looks sleeker to have them angled, but they're designed to be positioned upright for a reason.

How high should my VHF antenna be?

A 3- to 4-foot antenna that's 3 dB is generally recommended for boats under 24 feet. Larger vessels can opt for 12- to 18-foot, 7 to 8 dB antennas. “As a general rule, antenna height should be less than half the length of the boat,” Catoe says.

How can I improve my VHF antenna reception?

9 Best VHF Marine Antennas 2020

Does VHF antenna length matter?

The length of your antenna determines how good it is at handling certain frequencies; according to experts, there's a sweet spot that gives you the best signal. If you use an antenna that's too long or too short, your signal might cut in and out at times.

Why is the height of a VHF radio antenna important?

Nothing affects the performance of your VHF radio more than antenna height. This because VHF waves travel in a straight line and become weaker over greater distances. For communications to be effective, the receiving antenna must be able to “see” the waves coming from the transmitting antenna.

How far will VHF transmit?

A typical VHF station operates at about 100,000 watts and has a coverage radius range of about 60 miles.

Is longer antenna better?

So the answer is yes, size does matter, but bigger isn't always better. It all depends on what your transmitting and receiving frequencies are. Theoretically, a longer antenna will have a greater range, but it is far more important for optimal radio performance that the length of the antenna matches the frequency.

How high should my antenna be?

In general, the higher you place your antenna, the better. It would be best to have your antenna placed 30 feet above ground level to give you the clearest over-the-air connection with a tower. For those looking for that height, outdoor antennas are usually a good place to start.

How far apart should VHF antennas be?

NMEA recommends 6 feet of vertical and horizontal separation between the VHF and AIS antennas. Most manufacturers recommend more.

How close can I mount two VHF antennas?

The easy answer is that you should maintain a minimum mounting distance of at least 1/4 wavelength apart for the lowest frequency antenna within the same horizontal plane. For VHF antennas, that translates to roughly 19 inches. This is the rule we use when installing omni antennas on a the trunk of a vehicle.

How far should antennas be apart?

Antenna Positioning: Distance Between Antenna

For effective diversity performance, AB antennas should not be positioned less than ¼ wavelength apart, and ideally, they would be placed ½ to one full wavelength apart.

How long should your antenna be?

Ideally, the antenna length should be equivalent to the wavelength of a signal. However, this is often not practical given the very long wavelength of LPWAN signals. As a rule of thumb, antenna size of ½ or ¼ wavelength will produce good results.

Does antenna thickness matter?

Thicker wire increases the "bandwidth" of the antenna, aka the "range" of frequencies it can receive.

How does change in the length of antenna affect reading distance?

The obtained results show that attenuation drops with antenna heights in general but some heights give better results and attenuation fluctuation increases with frequency i.e the higher the frequency the higher the attenuation.

What affects VHF range?

There are other factors that affect the range of a two-way radio too such as weather, exact frequency used, and obstructions. The radio's power output has a factor too. Another important factor in the distance a two-way radio will communicate is its power output. This power output is measured in watts.

Is VHF line-of-sight?

VHF radio waves propagate mainly by line-of-sight, so they are blocked by hills and mountains, although due to refraction they can travel somewhat beyond the visual horizon out to about 160 km (100 miles).

Does VHF work on land?

Marine VHF radios, whether fixed or handheld, may not be used on land, period. It's the law. Once a VHF radio goes ashore, it cannot be used for marine band transmission (without a Coast Station License).

What negatively affects VHF radio communications?

Below we will discuss a few of the most common factors found to affect VHF communications: Transmitter Power, Intervening Topographical Features, and what can be considered to be the most important factor affecting VHF range, antenna height.

Why do some boats have 2 VHF antennas?

The advantages of the dual antenna

Not only does the installation of a second antenna give better readability to the AIS signal, but it can also serve as an emergency antenna for VHF. Just allow enough length behind the unit to disconnect the antenna from the AIS and connect it to the VHF.

How far offshore does VHF work?

If you are planning an offshore voyage, you need to know VHF radios and cellular telephones are limited in range, usually no more than 15 to 25 miles from shore.