When faced with unstable operation of the home network, users often begin to dig into the router settings or analyze the readings of air scanners, where they encounter a mysterious abbreviation dBmFor most, this value remains an incomprehensible figure that constantly changes and seems to affect internet quality. Understanding this parameter is critical for properly diagnosing coverage issues.
In fact, dBm (decibel milliwatt) is a logarithmic unit of signal strength used in radio engineering. It indicates how strong a radio signal is at a specific point in space, whether it's your smartphone, laptop, or smart plug. The closer the value is to zero, the stronger the signal, while large negative numbers indicate poor coverage.
You don't need to be a professional communications engineer to learn how to read these values and use them to improve your network. Once you understand the nuances, you can independently determine the best location for your router and whether it's worth buying an amplifier. In this article, we'll take a detailed look at the physical meaning of these values, the standards for different frequencies, and optimization methods.
⚠️ Please note: Signal values can vary significantly depending on wall materials, the presence of household appliances, and even the weather outside, so measurements should be taken at different times of day.
The physical meaning of the indicator and the logarithmic scale
To understand why dBm If the signal strength is always negative, we need to look at the physics of the process. The unit of measurement, dBm, expresses the ratio of signal strength to a reference value of 1 milliwatt, expressed on a logarithmic scale. Since the Wi-Fi signal strength at the receiver (your phone) is always less than 1 milliwatt, the logarithm of this ratio is negative.
Many users mistakenly believe that -70 dBm is better than -50 dBm, based on simple mathematical logic. However, in the context of wireless networks, the opposite is true: the closer the number is to zero, the better the connection quality. A signal of -30 dBm is practically perfect (it's close to the router), while -90 dBm means a complete loss of connection.
The logarithmic nature of the scale means that a small change in the numbers corresponds to a significant change in actual signal strength. A difference of just 3 dBm doubles or halves the actual signal strength. This explains why moving the router even half a meter can dramatically change page loading speeds.
Understanding this scale is essential when choosing equipment. If you see a router with a stated transmit power of 20 dBm, that doesn't mean it'll punch through three concrete walls. The actual power at the receiver will depend on a number of attenuation factors, which we'll discuss below.
Signal level gradation: from ideal to breakage
For practical use, it's important to know the specific value ranges you might see in your device's interface. Different operating systems and utilities may display this parameter differently, but the physical essence remains the same. Below is a detailed table classifying signal levels.
It's worth noting that threshold values may vary slightly depending on the sensitivity of your device's receiver. Older smartphone models may "drop" the network in areas where modern flagships can still reliably connect. Frequency range also plays a role: 5 GHz attenuates faster than 2.4 GHz.
| Signal level (dBm) | Connection quality | Description of the condition |
|---|---|---|
| -30 ... -50 | Excellent | Ideal conditions, router in the next room, maximum speed. |
| -51 ... -60 | Good | Stable performance, suitable for 4K streaming and online gaming. |
| -61 ... -70 | Average | Normal web surfing, occasional speed drops are possible. |
| -71 ... -80 | Bad | Video may buffer, calls may drop, speed may be slow. |
| -81 ... -90 | Critical | The connection is unstable, a complete break is possible, only basic tasks. |
If your measurements show values in the -75 dBm range or lower, you should definitely consider optimizing your network. Ignoring these indicators will lead to constant internet performance issues. In such cases, simply switching channels may not help; more serious intervention will be required.
Factors Affecting Indoor Signal Attenuation
Why does the signal weaken before reaching the end device? Wi-Fi's main enemy is physical obstacles. Walls, floors, furniture, and even aquariums absorb or reflect radio waves. Materials containing metal or water are especially critical, as they effectively shield the radiation.
Concrete walls with rebar can weaken the signal by 10-15 dBm, which is equivalent to being tens of meters away from the router in an open space. Wooden partitions and drywall are less critical, but still have a noticeable effect. Mirrors and tinted glass act as reflectors, creating interference zones.
In addition to building structures, household appliances also have an impact. Microwave ovens operating at 2.4 GHz create significant interference. Cordless phones, Bluetooth headsets, and even Christmas lights can contribute to the overall noise level, reducing the signal-to-noise ratio.
⚠️ Caution: Avoid placing the router near a microwave oven or behind a TV. The metal TV screen and microwave radiation can completely block the desired signal.
It's also important to consider the installation height of the equipment. The signal from the antennas travels primarily downward and to the sides. Placing the router on the floor or in a cabinet niche is one of the most common mistakes, leading to a loss of up to 30% of potential coverage.
The difference between the 2.4 GHz and 5 GHz bands
Modern routers operate in two main bands, and their dBm values will differ under identical conditions. The 2.4 GHz band offers better penetration but is more susceptible to interference from neighboring networks. The 5 GHz band offers higher speeds, but its signal attenuates more quickly when passing through walls.
At 5 GHz, a signal level of up to -70 dBm is considered acceptable, while at 2.4 GHz, the network can remain operational even at -75 to -80 dBm. This is due to the different wavelengths and signal modulation methods. Therefore, when in a distant room, the phone may automatically switch to 2.4 GHz to maintain the connection.
When analyzing the readings, it's important to pay attention not only to the absolute value but also to stability. If the reading fluctuates between -55 and -75 dBm, this indicates interference or equipment issues. A stable signal of -65 dBm is often better than a fluctuating -50 dBm.
For gaming consoles and video conferencing systems, 5 GHz is preferable, even if the signal is slightly weaker, as this band is typically less crowded. This ensures lower ping and more predictable latency, which is more important than absolute signal strength.
Why is 5 GHz faster, but "shorter"?
High frequency means shorter wavelengths. These waves bend less around obstacles and are absorbed more quickly by materials, but they allow for more data to be transmitted per unit of time thanks to their wide bandwidth.
Diagnostics and measurements: how to obtain accurate data
To get reliable information about your network's status, the built-in indicators on your router aren't enough. You need specialized tools that will show the real picture at every point in your apartment. This will allow you to create a coverage map and identify dead zones.
There are many free smartphone apps that display the RSSI (Received Signal Strength Indicator) value in real time. Using them, you can walk around your apartment and record signal drops in specific areas. This will help you determine where exactly to point your antenna or where to place a repeater.
- 📱 Wi-Fi Analyzer — a classic Android application that displays graphs and accurate dBm values for all channels.
- 🍏 AirPort Utility — a built-in utility for iOS (requires enabling the scanner in settings) that displays RSSI next to the network name.
- 💻 Acrylic Wi-Fi Home — a powerful tool for Windows that allows you to analyze the airwaves and noise levels in detail.
- 🌐 Router web interface — many modern models (Keenetic, ASUS, TP-Link) have built-in speed and coverage testers in the admin panel.
When taking measurements, hold the device in your hand as you normally would while surfing the internet. Avoid covering the top of the smartphone with your hand, where the antennas are typically located, to avoid artificially lowering the readings. Conduct tests at different times to account for the influence of your neighbors' activity.
☑️ Signal measurement algorithm
Signal enhancement methods and network optimization
If your measurements show unsatisfactory results, don't rush into buying new equipment. Often, the problem can be solved with proper adjustments or rearrangement. The first step should always be to optimize the current state of things.
Try reorienting your router's antennas. If the antennas are removable, you can replace them with more powerful ones with a higher gain (e.g., 8-12 dBi). It's also worth experimenting with the channel width: for 2.4 GHz, it's better to use 20 MHz instead of 40 MHz for increased stability.
In cases where the physical layout prevents signal penetration (for example, thick load-bearing walls), the only solution is to expand the network. Mesh systems, which create a single seamless network, or Powerline adapters, which transmit internet through electrical wiring, can be used.
⚠️ Note: Using cheap repeaters often results in a 50% reduction in speed, as they operate in half-duplex mode. It's better to consider mesh systems or a wired access point.
Don't forget about the software. Updating your router's firmware can improve signal processing algorithms and fix bugs. It's also worth checking whether your selected channel is overloaded by neighboring networks and, if necessary, switching to a clearer one.
Frequently Asked Questions (FAQ)
Why does the dBm value constantly fluctuate?
Fluctuations in readings of 3-5 dBm are normal due to multipath signal propagation (reflections from walls and objects). Fluctuations of 10-15 dBm or more may indicate interference from household appliances, neighboring routers operating on the same frequency, or a faulty antenna module in the device.
Can a Wi-Fi booster program really increase dBm?
No, software methods cannot increase the physical transmit power of a router or the sensitivity of a phone's receiver. Such apps only reset network settings or change network priorities, but do not affect radio frequency characteristics.
What dBm value is considered normal for online gaming?
For comfortable gaming without lag or connection drops, a signal level of at least -65 dBm is recommended. Below -70 dBm, the risk of packet loss increases, which is critical for shooters and fighting games.
Does the number of connected devices affect the dBm level?
The number of devices itself doesn't change the signal strength (dBm), but it does increase the load on the router's processor and airtime. This can lead to a perceived "slow" internet speed, even though the signal strength remains the same.