Which Wi-Fi signal is the strongest: dBm, dBi, and coverage analysis

Many users face a paradoxical situation: all the Wi-Fi bars on their smartphone screen are lit, but videos load with difficulty, and the speed drops to a crawl. This happens because visual indicators often mask the actual quality of the radio channel, and the concept of "power" in wireless networks has a double meaning. Some refer to transmitter strength, others to receiver sensitivity, and this confusion in units of measurement leads to incorrect conclusions when setting up equipment.

In the professional community of communications engineers, the primary benchmark is signal strength, measured in dBm (decibel milliwatts). This metric determines how stable a connection will be over a distance. The perfect signal The value is considered to be as close as possible to zero, although in reality it is practically impossible to achieve such indicators due to physical limitations and safety regulations.

In this article, we'll explore what dBm values ​​are considered excellent, why negative numbers are intimidating for beginners, and how the antenna's physical power in dBi affects the resulting internet speed in a distant room. Understanding these nuances will help you properly configure your router or choose the right repeater.

The Physics of the Process: What is dBm and Why is it Negative?

Unit of measurement dBm It represents the logarithmic ratio of signal power to one milliwatt. The unique feature of this scale is that it represents signal attenuation relative to a reference value. Since a Wi-Fi router's radiated power typically amounts to tens or hundreds of milliwatts, and only a small portion of the energy reaches the receiver, the resulting value is always negative.

The closer the number is to zero, the stronger the signal. For example, a value of -30 dBm would indicate proximity to the radiation source, practically touching the antenna. Conversely, a value of -90 dBm indicates critical attenuation, where the device is at the hearing limit of the base station. Logarithmic scale means that a change in the reading of just 3 dBm doubles or halves the actual signal strength.

⚠️ Attention: Don't confuse a negative sign with data loss. The minus sign before the number is simply a mathematical property of the power ratio logarithm, not an indication of hardware failure.

For the average user, it's important to remember a simple rule: ignore the minus sign when comparing. The number 50 is less than the number 30, but in the world of Wi-Fi, a -50 dBm signal is much stronger and better than -30 dBm. Signal attenuation occurs nonlinearly, and every lost decibel at high frequencies can mean a significant drop in data transfer speed.

Signal level chart: from ideal to disconnected

To understand what constitutes a strong signal, it's necessary to look at specific numerical values. Engineers divide the entire spectrum into several zones, each of which characterizes connection quality. Below is a table demonstrating the relationship between signal strength in dBm and network performance.

As can be seen from the table, the most powerful signal The range is between -30 and -50 dBm. However, aiming for -30 dBm in a residential apartment is pointless, as it requires being located a meter away from the router. For comfortable operation in all rooms of the house, the optimal target value is no worse than -65 dBm.

If your smartphone shows readings below -75 dBm, you should consider relocating your router or installing a booster. In areas with a good signal, most modern Wi-Fi 5 and Wi-Fi 6 standards can still provide decent speeds, but the connection's reliability is minimal. Any interference, such as turning on a microwave or a neighbor's router, can disrupt the channel.

Transmitter power vs. antenna gain

Users often wonder: what's more important for a strong signal—the router itself or its antennas? This is where the difference between transmitter power (measured in mW or dBm) and antenna gain (measured in dBi) comes into play. These parameters are interconnected, but they serve different functions.

Transmitter power is the "voice power" of your router. Safety standards limit this power (usually to 100 mW or 20 dBm in the 2.4 GHz band) to prevent equipment from causing harmful interference and harming health. Increased power Using software to control the transmitter is often prohibited by law and can lead to overheating of the chip.

Antenna gain, measured in dBi, indicates how effectively an antenna focuses radiated energy in a specific direction. An antenna doesn't create energy from the air; it redistributes it. A high-gain antenna (e.g., 8-12 dBi) transforms spherical radiation into a flatter "pancake," allowing for further signal penetration but reducing coverage above and below.

• 📡 Omnidirectional antennas (2-5 dBi) - ideal for apartments where you need to cover the space around the router in all directions.
• 🎯 Directional antennas (10+ dBi) - used to transmit a signal to a specific remote point, for example, to a neighboring house or the far corner of an office.
• ⚖️ Compromise of form — the higher the antenna gain, the narrower the radiation pattern becomes, creating "blind spots" in the immediate vicinity.

The myth of "homemade antennas"

Many people try to boost the signal by attaching foil or a can to the standard antenna. This does change the radiation pattern, making the signal more focused in one direction, but you lose coverage in other directions and can disrupt the signal matching, which ultimately reduces the overall efficiency of the system.

The influence of the 2.4 GHz and 5 GHz frequency bands on power

When choosing the "strongest" signal, frequency range can't be ignored. Modern equipment operates in two main bands: 2.4 GHz and 5 GHz. The physical properties of radio waves dictate different use cases and attenuation rates.

Range 2.4 GHz has better penetration. Waves of this frequency bend around obstacles and pass through walls more easily, maintaining a higher signal level (lower dBm) over a distance. However, this range is highly noisy: microwaves, Bluetooth devices, and neighbors' routers operate in this range, creating a high level of noise.

Range 5 GHz It provides much higher speeds, but waves of this frequency have a harder time penetrating solid obstacles. The 5 GHz signal attenuates faster when passing through concrete walls. Therefore, even if the router is powerful, in the next room, through two walls, the 5 GHz signal level can drop to a critical -80 dBm, while 2.4 GHz will remain at -60 dBm.

⚠️ Attention: When measuring signal strength, always check which frequency (2.4 or 5 GHz) the device is connected to. Directly comparing "power" between bands is incorrect due to the different receiver sensitivities and the physics of wave propagation.

For maximum performance in the same room as your router, always choose a 5 GHz network. However, if you need coverage throughout your entire home and a stable connection through multiple walls is important, the good old 2.4 GHz will be more powerful and reliable, despite its lower speeds.

How to measure the actual signal level in dBm

The bars on a smartphone screen are a subjective assessment by the manufacturer, which often doesn't reflect reality. To obtain accurate data and understand your actual signal strength, you need to use specialized tools. Operating systems offer different options for this.

On devices with Android You can use the built-in engineering menus or third-party apps. The easiest way is to go to the Wi-Fi settings, find the properties of the current network, and look at the "Signal Strength" parameter. Apps like WiFi Analyzer or WiFiman, which plot graphs and show the exact numerical value.

For users iOS (iPhone/iPad) Accessing raw data is more difficult due to the closed system. However, there is a life hack: if you hold down the Option on your Mac keyboard and click on the Wi-Fi icon in the menu bar, an extended menu will open where in the field RSSI (Received Signal Strength Indicator) will display the exact signal level in dBm. For Windows, the equivalent is a command in the command line.

netsh wlan show interfaces

In the output of this command you need to find the line "Signal", which will be shown as a percentage, but for accuracy it is better to use third-party utilities like Acrylic Wi-Fi Home, which output data in dBm.

Factors that reduce signal strength indoors

Even the most powerful router is powerless against the physics of building materials. The concept of "strong signal" is relative: in an open field, a router will penetrate 300 meters, but in a concrete building, it'll barely reach 30. Understanding what exactly "eats" your dBm will help you place your equipment correctly.

Wi-Fi's main enemies are water and metal. Concrete walls with rebar almost completely block the signal. Mirrors, aquariums, heating pipes, and even tree foliage outside the window (since plants are made of water) cause significant signal loss. Signal attenuation can reach 10-20 dBm when passing through one load-bearing wall.

Interference is also worth considering. If ten routers are operating on the same channel in an apartment building, they create a "noise carpet." Your receiver sees a strong signal but can't make out useful information due to the interference. In this case, the signal strength (RSSI) may technically be high, but the connection quality (SNR – signal-to-noise ratio) will be low.

• 🧱 Wall materials: Drywall is almost transparent to Wi-Fi, brick is moderately attenuating, and concrete and metal are critically attenuating.
• 📺 Household appliances: Microwave ovens generate powerful interference in the 2.4 GHz range when operating.
• 🪞 Reflective surfaces: Large mirrored cabinets can create echoes that destabilize the connection.

FAQ: Frequently Asked Questions

What dBm value is considered normal for stable operation?

The normal range for stable operation is considered to be between -50 and -65 dBm. Within these limits, all modern speed standards are supported, video calls are uninterrupted, and games run without lag. Values ​​below -75 dBm are considered borderline.

Is it possible to increase the router signal strength programmatically?

Theoretically, it's possible by changing the region or transmit power settings in advanced firmware (such as OpenWrt). However, this often leads to violations of legal regulations and device overheating. It's more effective to purchase an antenna with a higher gain (dBi).

Why is the signal on 5 GHz weaker than on 2.4 GHz?

This is a physical property of radio waves: the higher the frequency, the shorter the wavelength and the less well it bends around obstacles. A 5 GHz signal attenuates faster in walls and air, so its range is always shorter than that of 2.4 GHz at the same transmitter power.

Does the number of antennas affect signal strength?

Not directly. The number of antennas in modern routers (MIMO) is needed to increase throughput and stability, not to increase transmit power. One high-quality antenna can perform better than three cheap ones.