Why is the Height of VHF Radio Antenna Important?

Radio waves, like any other electromagnetic waves, travel in a straight line and often get reflected by a certain obstacle. Therefore, to maintain a smooth transmission of signal, antenna height should be taken into consideration.

Now, why is the height of the VHF radio antenna is important? Because it also consists of radio waves. Moreover, an antenna mounted at a significant height will have a greater frequency range.

While discussing the importance of antenna height, there are several factors to consider. One should also know the placement of the antenna and, not to mention, also learn about the effective height of the antenna.

What is the Height of A VHF Radio Antenna?

Does VHF Antenna Length Matter
VHF Antenna

An antenna’s height determines the range of frequency it can emit throughout a considerable radial distance. As we’ve mentioned before, a greater height is important to eliminate all obstacles and diminish radio signals.

Using a VHF radio range calculator, you can determine a certain value for the antenna height to account for a certain range of communication. Additionally, if you figure out the range all by yourself, here are some formulas to determine it:

For a plane flat surface of signals, the formula for the range is given as:

Range = 1.22 x square root of antenna height

The above unit of the range is given in miles, but for marine applications, nautical miles are used for the unit of range for a smooth communication system and the formula is given:

Range = square root of antenna height

Additionally, while communicating between two antennas, one has to calculate or assume the effective range for efficient transmission or receiving of signals. Hence, the nautical range is slightly modified into:

Range = square root of transmitter’s height + square root of receiver’s height

Why is the Height Of A VHF Radio Antenna Important On A Boat?

While traveling on a boat, a sailor must communicate with other boaters and the control tower for the stranded location (if any circumstances ever arise).

Hence, for effective communication, the radio antenna installed on the boat should have a higher range of frequencies, which we call a VHF antenna. Additionally, a VHF antenna also must have a considerable height.

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Why is there a need for a considerable height for marines? Because while transmitting signals, there can be numerous obstacles like mountains or trees ,which can block the necessary piece of information. Hence, the receiver will receive weak signals from the transmitters.

Hence, maintaining a considerable height of the VHF antenna on a boat or ship is important. Other than that, setting up a perfect elevation angle will also account for perfect radio communication over lakes or seas.

So, attention to all boat owners, make sure to set up your VHF radio antenna at a significant height with a perfect elevation angle for signal transmission and reception.

Does VHF Antenna Length Matter?

To clear up your confusion, the antenna length on the boat matters because the length reflects the performance and strength of the transmission and not to mention; it has to surpass certain obstacles to reach the receivers.

Normally, the length of the antenna should be less than half of the boat size. The standard antenna length used for boats is 3 to 4 feet which is equivalent to 3 dB antenna gain. 

Additionally, if you want to get an antenna with more gain, keep in mind that the length of the antenna is also inversely proportional to the emitted frequency.

So, one has to keep certain parameters in mind while choosing a significant length of the antenna for their boats.

How Does Height Affect Antenna Reception?

For a two-way communication system, the antennas need to receive and transmit similar signals with the same amount of gain and the least amount of noise

When there are too many obstacles along the traveling distance of the radio waves, much signal information might get lost, and a signal with less strength will be received across the transmitter.

Hence, the antenna is kept at the maximum level possible to avoid such interruption in communication, also known as antenna reception.

What Are the Two Main Factors That Affect the Range Of VHF?

The two main factors that affect the range of VHF are as follows:

  • Terrains or Obstacles
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The terrains over a long-distance transmission of radio signals can significantly impact the range of VHF.

As we said earlier, mountains, hills, trees, or other solid obstacles can block the radio waves, thus affecting the transmission efficiency of the antenna and the overall range of the VHF.

  • Atmosphere

Last but not least, several atmospheric conditions such as humidity, rainfall, and foggy weather can contribute to the scattering of the radio waves thus influencing the noise in the transmitter, the range of VHF, and the overall performance of the antenna.

Hence, while setting up an antenna in a fixed location, make sure to clear the radius with no obstacles and also monitor the atmosphere, so it doesn’t affect the VHF’s range to a significant level.

What is the Best Placement of A VHF Aerial?

Hence, to avoid problems such as signal interruption or noise, the best placement of a VHF aerial must be at least 6 to 10 feet above the ground level. 

Furthermore, a radio antenna should be placed inside a minimum radius of 5 meters from any construction or natural obstacles such as trees or mountains.

Is It Effective If Rather Antennas Are Mounted on Higher Grounds?

If one follows the above condition while mounting a VHF radio antenna, then one will notice the received or transmitted signals are having almost the same amount of gain from their original position.

The little fluctuation in the antenna gain results from the system’s transmission loss of the signals that are considered to be negligible. So, it’s highly effective if antennas are mounted on high ground.

Why is the Effective Height of The Antenna Slightly Greater Than the Physical Height?

The effective height of the antenna is slightly greater than the physical height of the antenna. This is because the effective height considers nearby objects that can reflect or refract the radio waves, eventually increasing the range and the effective height.

If objects can reflect or refract waves (other than blocking them), they’ll increase the antenna’s performance in terms of gain and antenna height. But buildings or other objects might contribute to the signal to block rather than strengthen.

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So, how to increase the effective height of the antenna? There Are several ways to establish that, some of them include:

  • Using a reflector around the antenna

A reflector can be used to reflect or refract the waves that are being transmitted, which will increase the effective length, overall frequency range, and performance of the antenna.

  • Add a ground plane

It’s generally installed underneath the antenna and acts as a reflector to increase its effective height.

  • Mount the antenna on a tall structure

As we’ve mentioned before, setting your antenna on a tall monument will help smooth transmission and receiving of signals. Also, it’ll help increase the antenna’s effective height.

  • Using a directional antenna

Directional antennas are also gain antennas that can contribute to the effective length of the antenna as well the signal transmission.


 So, why is the height of the VHF radio antenna important? Because increased height can diminish all the signal interruption resulting from hard terrains such as mountains, hills, trees, and so on.

Apart from the terrain issues, we’ve seen that atmospheric conditions also play a vital role in affecting the range of VHF antennas. Additionally, we’ve also learned that increasing the antenna height is another way to increase the effective length of the antenna to increase its performance.

Now you know all the factors behind the importance of VHF radio antenna height. Next time someone asks you about their necessities, don’t forget to shower them with the knowledge you’ve gathered here today.

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