Many users face a situation where their wireless network is unstable, speeds drop, and coverage leaves much to be desired. The first step to solving the problem is signal strength analysis, which is emitted by your router. Understanding how strong the signal is at different points in the room allows you to properly place the equipment or adjust its settings.
However, simply looking at the indicators on the device's body isn't enough, as they often only indicate the presence of a connection, not its quality. To obtain accurate data, specialized software or hardware spectrum analyzers are required. In this article, we'll discuss... How to measure Wi-Fi transmitter power available methods, what the dBm values mean and how to interpret the results to improve the network.
It is worth noting right away that transmit power This is only one side of the coin. The sensitivity of the receiver, whether it's a smartphone, laptop, or IoT device, is equally important. Often, the problem isn't that the router is broadcasting too quietly, but that the client device can't "scream" back. Nevertheless, measuring the signal strength (RSSI) is a basic procedure for any network engineer or advanced user.
Understanding units of measurement and standards
Before we begin taking practical measurements, it's important to understand the terminology. The main indicator you'll see in analysis programs is RSSI (Received Signal Strength Indicator). This is an indicator of the received signal strength, measured in negative decibel milliwatts (dBm). It's important to understand that the closer the value is to zero, the better the signal.
The typical range for WiFi is between -30 dBm (perfect signal, close to the antenna) and -90 dBm (no connection at all). Values below -80 dBm typically indicate an unstable connection with frequent drops. For comfortable use in office and home environments, the target is considered to be -50 to -65 dBm.
⚠️ Attention: Don't confuse the transmitter's radiated power (Tx Power), which is specified by the manufacturer and limited by law (usually up to 100 mW or 20 dBm in the 2.4 GHz band), with the signal level you measure at the client. You're measuring the residual signal power reaching the receiver.
There is also a concept EIRP Effective Isotropic Radiated Power (EIRP) is the equivalent radiated power. It takes into account not only the power of the router's chip but also the antenna gain. EIRP is the legally significant parameter for equipment certification. When you take your own measurements, you indirectly evaluate this parameter at a specific point in space.
Software measurement methods for Windows and macOS
The most accessible way to perform diagnostics is to use a laptop with specialized software installed. Operating systems provide basic tools, but third-party utilities are better for in-depth analysis. On Windows, the built-in command line can display the signal strength as a percentage, which isn't always informative for precise adjustments.
To obtain data in dBm on Windows, it is recommended to use utilities like Acrylic Wi-Fi Home or NetSpotThey scan the airwaves and display detailed information about each available access point. The interface of these programs displays a signal attenuation graph and an exact numerical value of the signal strength.
macOS users are in luck, as the system has a hidden but powerful diagnostic tool. By pressing the key Option and by clicking on the WiFi icon in the menu, you can see more detailed information. However, for creating heat maps and detailed analysis, it's better to use WiFi Explorer or a free utility Wireless Diagnostics, built into the system.
To launch the built-in analyzer on your Mac, open Spotlight (Cmd + Space), enter Wireless Diagnostics and run the program. Don't click "Continue," but select "Proceed" from the top menu. Window → Scan (Window → Scan) This displays the current noise and signal levels in dBm.
Mobile applications for Android and iOS
Your smartphone is the device you use most often when connecting to WiFi, so it's logical to measure the signal on it. This will give you the most realistic picture of connection quality in your locations. Android offers significantly more analysis options thanks to its open file system.
One of the best tools is the app WiFi Analyzer (from VREM Software Development or similar open-source versions). It displays a real-time signal strength graph. You can walk around your apartment, observing how the dBm value changes, and identify "dead zones."
On iOS, the situation is more complicated due to Apple's security restrictions. Standard App Store apps don't have access to accurate real-time signal strength data in graph form. However, there are workarounds. For example, using terminal emulation mode or specialized network engineering apps that require a WiFi connection to the router itself to retrieve data via SNMP or CLI.
Built-in features are also worth mentioning. On Android, the WiFi settings section often includes a "Rate Network" or similar button that shows connection quality. However, for professional transmitter power measurements, it's better to use third-party software that displays raw RSSI data.
- 📱 WiFi Man (Ubiquiti) is a great cross-platform tool available on iOS and Android that shows signal strength and allows you to ping devices.
- 📱 Fing — a popular network auditing application that also displays the signal strength of the current connection.
- 📱 WiFi Monitor — an Android application that provides detailed graphs of signal strength changes over time.
Using the command line and Linux utilities
For system administrators and Linux enthusiasts, the command line remains the king of diagnostics. In Linux distributions that use NetworkManager, you can obtain signal strength information using the utility nmcliThis allows you to quickly assess the situation without a graphical interface.
The command to check looks like this:
nmcli dev wifi listThe output of this command will contain a column SIGNAL, which shows the quality in percentage, but to get accurate dBm it is better to use utilities based on iw. Team iw dev wlan0 link (where wlan0 is the name of your interface) will show the parameter signal: in dBm.
In Windows, you can also get basic information via PowerShell. The command netsh wlan show interfaces will display a detailed report on the current connection, including the "Signal" percentage. While this isn't in dBm, the conversion is simple: 100% is approximately -50 dBm, and 1% is approximately -100 dBm.
⚠️ Attention: Command line interfaces may vary depending on your WiFi adapter drivers and operating system version. If the command returns an error, check the network interface name.
Android Secret Codes
On some Android smartphones (especially Samsung, Xiaomi) you can enter a code #0011# or ##4636##* in the dialer. This will open the service menu, where in the WiFi Status section you can see the exact RSSI value in dBm without installing any apps.
Hardware analyzers and a professional approach
If you need certified measurements or analysis in challenging industrial environments, software methods may not be enough. Professionals use portable spectrum analyzers, such as those from Fluke Networks or EkahauThese devices are expensive, but they provide high accuracy and allow you to see not only WiFi but also sources of interference (microwaves, Bluetooth, cameras).
An alternative to expensive analyzers is using WiFi adapters with an external antenna and monitoring mode. By connecting such an adapter to a laptop, you can "hear" even very weak signals that the built-in card can't detect. This is useful when designing networks for large areas.
There are also USB dongles with Realtek chips, which, when flashed with alternative drivers, can display very detailed statistics. However, for most home use, a high-quality smartphone with a good receiver is sufficient.
| Signal level (dBm) | Quality | Description | Possibilities |
|---|---|---|---|
| -30... -50 | Excellent | Being close to the router | Maximum speed, 4K streaming, VR |
| -50... -60 | Good | Within one room | Stable internet, video calls, games |
| -60... -70 | Average | Adjacent room or floor | Web surfing, mail, speed drop possible |
| -70... -80 | Bad | Far from the source, many walls | Text only, connection may drop |
| -80... -90 | Critical | At the limit of range | The connection is unstable or absent |
Factors affecting measurement accuracy
The figures obtained can vary greatly depending on many factors. Wall materials (concrete, metal, glass) dramatically reduce signal strength. Even the position of a person's body between the router and the receiver can change readings by 3-5 dBm.
Another important factor is airtime congestionIf a dozen neighboring routers are operating on the same channel, the noise floor increases. As a result, the signal-to-noise ratio (SNR) drops, even if the absolute signal strength remains high. Power must be measured in the context of the noise floor.
It is also worth considering the difference between the 2.4 GHz and 5 GHz bandsThe 5 GHz signal attenuates faster when passing through obstacles, but is less susceptible to interference. Therefore, at the same point, the 5 GHz signal strength may be 10-15 dBm lower than 2.4 GHz, but the connection quality will be better.
☑️ Checklist before measuring
Frequently Asked Questions (FAQ)
Is it possible to increase the transmitter power programmatically?
In most civilian routers, power is limited by the driver and country-specific regulations. In advanced firmware versions (OpenWrt, DD-WRT), you can sometimes change the region to a country with less stringent limits (for example, Bolivia), which will formally allow power, but this can lead to equipment overheating or legal issues.
Why does my phone show 100% but the speed is low?
The indicator on a phone often shows the signal strength (RSSI), but it doesn't take into account noise and interference. If the airwaves are clogged with neighbors, the signal may be strong, but the useful channel capacity will be close to zero due to constant packet forwarding.
How to convert signal percentage to dBm?
There's no exact formula, as driver manufacturers use different scaling algorithms. Approximate correspondence: 100% ≈ -50 dBm, 75% ≈ -65 dBm, 50% ≈ -75 dBm, 25% ≈ -85 dBm. For accuracy, always use specialized software.
Does the number of antennas affect signal strength?
The number of antennas affects the radiation pattern and MIMO (multiple input/output) technology, which increases overall throughput and stability, but does not necessarily linearly increase the radiated power at any one point. One well-tuned antenna can provide a better signal in a specific area than four.
Do measuring instruments need to be calibrated?
Calibration is not required for everyday use. The readings may vary by 3-5 dBm between different smartphones, which is considered normal. For professional network audits, calibrated spectrum analyzers are used, which undergo verification.
The influence of weather
Although it may seem counterintuitive, air humidity and atmospheric pressure can affect radio wave propagation, especially outdoors and at frequencies of 5 GHz and above. Indoors, this effect is minimal.