One of the reasons securities use walkie-talkies is that they can communicate with other people inside the building without needing mobile signals. So, it allows for 24/hrs communication. But, you might wonder how walkie-talkies work through walls since their frequencies travel straight. Or do they bounce off walls instead?
Yes, walkie-talkies can work through walls, but not all types can. For example, UHF walkie-talkies can work through walls due to their short wavelength. But VHF walkie-talkies won’t communicate through thick walls.
Electromagnetic Wave Propagation
Propagation refers to how waves travel or move. Propagation for two-way radios refers to the way electromagnetic waves travel. There are three propagation methods:
- Skywave propagation
- Ground wave propagation
- Free space wave propagation.
Skywave or skip propagation is a method of electromagnetic wave propagation. Their propagation frequency ranges from 3 to 30MHz. Frequencies in this bandwidth are called High Frequencies (HF).
High frequencies are short waves. The ionosphere, an electrically charged upper atmosphere layer, doesn’t absorb them. Instead, they refract back down toward the earth. The waves bounce off the ionosphere and come back down toward the ground.
Skywaves don’t follow the curvature of the earth. Instead, they reach the ionosphere, facilitating communication beyond the horizon. The distance between transmission and reception is the skip distance. Usually, for skywaves, the higher the frequency, the longer the skip distance.
International shortwave broadcasting stations and government time stations use high-frequency bands. Weather stations, amateur radio, and citizen band services also operate in high-frequency bands.
Unlike skywaves, ground waves follow the curvature of the earth. Ground wave propagation is parallel to the earth’s surface. When long wavelengths propagate through ground waves, they diffract around obstacles. It allows them to follow the earth’s contour.
Ground wave propagation covers the area between the earth’s surface and the ionosphere. Therefore, it is most suitable for short-distance communication, especially during the day.
Low and medium frequencies below 3MHz travel through ground waves. It includes Extremely Low Frequency (ELF) and Super Low Frequency (SLF). Ultra Low Frequency (ULF), Very Low Frequency (VLF), and Medium Frequency (MF) are also below 3MHz.
They use low frequencies for submarine and mine communication. Amateur radios and AM broadcasts also operate in low to medium frequency bands (3 Hz to 2MHz).
Free Space Waves
Line of sight communication uses free space wave propagation or tropospheric wave propagation. Space wave propagation occurs when frequency waves travel in a straight line. This straight line travels within the troposphere layer of the earth’s atmosphere.
Space wave propagation allows direct communication between the transmitter and receiver. Refraction and diffraction don’t affect space waves. Instead, they depend on their line of sight, so they travel in a straight line.
Free space propagation assumes that electromagnetic waves travel in an ideal environment. Such an environment is free of obstacles, but this is usually untrue.
Signals traveling in a straight line might encounter obstructions like trees, hills, and walls. The earth’s curve can also affect free space propagation. Thus, the transmission tower must be high enough to prevent the waves from touching the earth’s curve.
High frequencies above 30 MHz travel through space waves. They use these high frequencies for FM radio and two-way radio communication. Satellite communication and broadcast television also operate in these frequency bands.
What Electromagnetic Wave Propagation Do Walkie-talkie Frequencies Use?
Walkie-talkies operate in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands. These bands consist of high frequencies greater than 30 MHz.
Because walkie-talkie’s frequencies are very high, the ionosphere weakly reflects them. Thus, they can’t travel through skywave propagation. They also can’t travel through ground wave propagation since they don’t follow the earth’s shape.
Instead, UHF and VHF frequencies follow line-of-sight. They travel through free space wave propagation in a straight line. Ideally, these waves should only travel from the transmitter to the receiver without obstacles.
The reason is that the waves must be within the line of sight to communicate, which means two walkie-talkies must be within the line of sight to talk. But you can still see each other to speak. Generally, walkie-talkies can transmit over a distance of several miles.
Obstructions like buildings, trees, and mountains can affect the range of communication. But, sometimes, frequencies can find their way around some obstacles. In this case, frequencies can still travel in a straight line.
If the earth were flat, line-of-sight propagation would have been easy. But the earth’s curvature makes it difficult for electromagnetic waves to travel. Thus, to communicate effectively, walkie-talkies must be in a range close enough to be in the line of sight.
This range differs depending on the power output of the walkie-talkie. It also depends on weather conditions and the presence of solid obstructions.
Line of sight is critical to two-way radio communication. But, some radio frequencies can travel through barriers, like walls and steel. For example, the Ultra High-Frequency band (UHF) can better travel through obstacles than the Very High-Frequency band (VHF).
The jargon behind this is the difference in the wavelengths of both frequency bands. But before we look at wavelengths, let’s see what UHF and VHF frequency bands are.
VHF and UHF Frequency Bands
VHF frequencies range from 30 to 300 MHz (Megahertz). Most walkie-talkies can operate in the 136 to 174 MHz frequency band. VHF radios consume less power and have lower frequencies than UHF radios.
Because they have longer wavelengths (10m – 1m), they can reach a more extended range of roughly 160km (100 miles). Using VHF walkie-talkies outside is advisable where there’s no obstruction.
But this estimated range is almost impossible to reach because of obstructions. As a result, the walkie-talkie range will be less than the ideal VHF range of 100 miles. This rule also applies to UHF walkie-talkies.
On the other hand, UHF frequencies range from 300 to 3000 MHz (3 GHz). And UHF walkie-talkies usually operate in the 400 to 512 MHz frequency band. Unlike VHF frequencies, UHF bands operate at higher frequencies.
UHF transceivers have higher frequencies. Thus, they consume more power than their VHF counterparts. Also, UHF wavelengths are shorter, typically 1m to 10 cm. They can only cover a short distance of roughly 60km (37 miles).
How Does Wavelength Affect How Frequencies Travel?
Wavelength is the distance between two corresponding or identical crests. The crest is the highest point of a wave. You can also measure the wavelength using the trough, the lowest part of the wavelength.
Thus, the wavelength is also the distance between two corresponding or identical troughs. Wavelength is usually in meters, centimeters, or milliliters.
In other words, the wavelength is the distance over which the wave’s shape repeats. You get the wavelength when you measure the distance between two identical waves. Typically, the wavelength is inversely proportional to the frequency.
What this means is that lower frequencies (VHF) have longer wavelengths. On the other hand, higher frequencies (UHF) have shorter wavelengths. The lower the frequency, the longer the wavelength. Similarly, the higher the frequency, the shorter the wavelength.
What Walkie-talkie’s Frequency Band Can Work Through Walls?
Short waves can travel through thick walls. Their high frequencies allow them to penetrate walls. They can also easily navigate their way around obstacles.
Because UHF walkie-talkie frequencies have shorter wavelengths, they have more penetrative power. This feature allows them to pass through thick walls better than VHF frequencies. Thus, it’s better to use UHF transceivers indoors. You can use them in office spaces, hotels, schools, and apartments.
VHF transceivers do better in open spaces with little to no obstruction. If the wave can travel freely, it can travel long distances outdoors. But UHF walkie-talkies will do better than VHF walkie-talkies in a built-up environment.
Frequently Asked Questions
Can All Walkie-talkies Work Through Walls?
Not all walkie-talkies can work through walls. Two-way radios operate in different frequency bands and have different wavelengths.
Ultra High Frequency (UHF) can work through walls because their wavelengths are short. But, Very High Frequency (VHF) waves hardly travel through walls because their wavelengths are long.
Do Walkie-talkies Only Work Through The Line-of-sight?
Walkie-talkie frequencies only travel through line-of-sight. However, UHF frequencies can pass through concrete walls and find their way around solid obstructions. In an ideal environment, frequencies travel from the transmitter to the receiver in a straight line.
Which Walkie-talkie Is Best For Use In Buildings?
It’s more convenient to use UHF walkie-talkies inside a building. Although they have a shorter range, they can penetrate concrete walls and bypass steel obstacles. On the other hand, VHF walkie-talkies can cover longer distances but are not suitable options for indoor use.
Your walkie-talkie frequency band will determine the best scenario of use. UHF frequencies have shorter wavelengths that allow them to penetrate or bypass thick walls. VHF frequencies have longer wavelengths for a more extended signal range but can’t pass through walls.
Hence, UHF walkie-talkies can work through the walls of your apartment or office. But it would be best to use VHF walkie-talkies outdoors, in open spaces. They work best where there’s little to no obstruction.