How do VHF radio waves travel?

How do VHF radio waves travel?

When personnel need a reliable way of conveying messages to one another and onwards to a base of operations, very high frequency (VHF) radio is one of the most effective forms of communication. Due to the way these radio waves travel, VHF is used when there is an unobstructed path between two radios. This is known as line-of-sight (LOS) communication.

Let’s take a closer look at how VHF radio waves travel, and what this means for tactical and military efforts in the field.

Understanding the radio horizon

The VHF frequency band is defined as the frequency range from 30 to 300 megahertz (MHz). This means that the size of antennas used in VHF radio are much smaller and lighter than those in HF radios – a big advantage for manpack radios in the field.

The primary mode of propagation for VHF radio waves is through direct waves. These travel in a straight line, becoming weaker as distance increases.

Transmitting and receiving antennas must be able to ‘see’ each other for communications to be effective, so antenna height is critical in determining range. Because of this, direct waves are sometimes called LOS waves.

Height and LOS range in action

The visible horizon observed at approximately 1.5 meters (5 feet) above a flat surface of ground is less than 4.3 kilometers (2.6 miles) away. This is approximately the maximum LOS range from a manpack radio on the back of a standing soldier to another manpack radio that is lying on the ground.

If the receiving radio is also elevated to the back of a standing soldier, the maximum distance is be doubled. In this case, the LOS distance is 8.6 kilometers (5.3 miles). But, if the second soldier is standing beyond this distance – say at 11.2 kilometers (7 miles) from the transmitting radio – the shadowing effects of the Earth’s curvature prevent the second soldier from receiving the radio wave. In this case, 11.2 kilometers is beyond LOS and not within reach of VHF radios in these positions.

It is clear that the elevation of both the transmitting and receiving antennas is crucially important. For example, if the receiving antenna were mounted on an 8-meter (26-foot) tower, the total LOS distance would be increased to 14.5 kilometers (9 miles).

Of course, if the radiomen were both located on the tops of mountains, the LOS range might be as much as 50 to 100 kilometers (30 to 60 miles).

Many manpack radios have various power settings: Low power settings are often adequate and extend battery life. On the other hand, there are situations where increased power is beneficial. In urban areas where high radio frequency noise is prevalent, higher power increases the signal-to-noise ratio and improves reception.

The physical environment can have a strong impact on VHF radio transmissions.

It is important to note that these signals are affected by ground conditions like geophysical features and electromagnetic conductivity. As such, there may be a number of paths they take between two points of communication.

The distances and measurements mentioned in this article are only intended as a guideline. To learn more about VHF radio and its uses in tactical applications, contact a Barrett Communications representative today.

RELATED ARTICLES

How valuable are smartphones to critical responders

The emergence of smart technology has transformed communication methods all over the world. More Related News/Articles:Increasing communication with smart devices and HF radioFirst responders support Dominica’s rebuilding after…What role does secure radio play in critical communication?6 HF solutions essential for humanitarian agencies

3 ways to expand the transmission range of your VHF radio

There are many reasons why you may need to increase the communications range of your VHF radios in the field. More Related News/Articles:5 ways HF vehicle tracking is vital to humanitarian…How scalable is HF radio?3 questions to answer when setting up a critical…HF Radio assisting disaster relief in Peru

What links line-of-sight to over-the-horizon tactical communications?

Whether trying to connect with other squads in the field or make contact with headquarters thousands of kilometres away, More Related News/Articles:How can a VHF radio setup overcome the radio horizon?How do VHF radio waves travel?What can I expect from a Barrett VHF radio…Tactical HF vs VHF radio – when should I use them

Can HF and VHF radio propagation overcome extreme weather?

Thunderstorms and heavy rain have a palpable effect on communication systems. Internet connectivity is notably disrupted by extreme weather events More Related News/Articles:Why HF radio is essential in flood reliefDoes space weather impact tactical HF communications?How can a VHF radio setup overcome the radio horizon?Does weather affect HF radio signals?

What makes tactical HF radios uniquely fit for purpose?

From remote locations, to areas with compromised conventional communications infrastructure, tactical operators face an uphill battle More Related News/Articles:Why HF radio is vital for humanitarian work in the Pacific3 requirements for rugged and reliable tactical HF radioWhat 3 factors does HF radio offer critical communications?What power supply options will best power my tactical radio

How can you power your VHF radio in the field

The nature of tactical communications in the field means they’re sometimes going to take place in locations with no mains power. More Related News/Articles:How to set up HF radio for critical comms in infrastructure3 ways to expand the transmission range of your VHF radio3 questions to answer when setting up a critical…What power supply options […]

Post by onchada_admin