Mobile phone problems on Xiaomi smartphones, including the popular Redmi Note 9 Pro, can be a serious obstacle to comfortable communication and stable Internet access. Often users are faced with a situation where the indicator shows the full signal level, but calls are disrupted, and the voice of the interlocutor is distorted or lost. This can be caused by software failures of the MIUI shell, and incorrect network settings that are not always optimized for a particular operator by default.
Device owners often underestimate the importance of having the right access points and modes of radio module configuration. The quality of communication depends on how accurately your smartphone interacts with the operator’s base stations. In this article, we will discuss a comprehensive approach to solving this problem, from basic checks to advanced settings of the engineering menu.
Basic diagnosis and verification SIM-map
Before we get into complex system settings, we need to rule out the physical causes of bad reception. Often the problem lies in the subscriber identification module itself or its contacts. SIM-Cards that you have moved from phone to phone for years may have microcracks or oxidized contacts, leading to an unstable connection to the network. 4G/LTE.
Remove the tray and carefully examine the chip. If scratches or dirt are visible on the surface, gently wipe them with a soft cloth without pile. It is also worth checking whether the card is cut correctly if it is adapted manually - the slightest mismatch in size can lead to poor pinching of the contacts in the Redmi Note 9 Pro slot.
- 📱 Try to rearrange. SIM-card to the second slot, as the first slot often takes priority by standard LTE, But sometimes the second one works more stable in areas of low reception.
- 🔄 Reboot the device after retrieving and re-installing the card so that the communication module re-enters the network registration procedure.
- 📶 Check the work. SIM-cards in another phone to rule out faulty operator or chip damage.
If the problem persists after a physical check, you should pay attention to the software part, in some cases, updating the operator profile helps, which often comes in the background, but may not be installed due to errors.
⚠️ Warning: Never use metal objects to clean your contacts SIM-cards, as static electricity or mechanical damage to tracks can permanently disable the chip.
Configure the preferred type of network
One of the most common causes of intermittent sound and dropped calls is an aggressive switch between 3G and 4G modes. Xiaomi Redmi Note 9 Pro smartphone tries to constantly keep the maximum speed of the Internet, and if the 4G signal becomes slightly weaker, it switches to 3G, which at the time of the conversation causes a connection break or a transition to low sound quality.
To stabilize voice communication, it is advisable to force the network to limit the mode of operation, this is especially true in places where the coverage is not limited. 4G unstable but confidently caught 3G. To change the settings, go to the Settings menu. → SIM-maps and mobile networks → Choose. SIM → Preferred type of network.
Here you can select the option "Only 3G" to check the quality of calls, if this mode becomes stable, then the problem is precisely the jumps between communication standards, but for permanent use it is better to leave the mode "Preferred to 4G", but activate the VoLTE function if it is supported by your carrier.
⚠️ Warning: Forced switching to "Only" mode 2G" can completely disable the ability to use the Internet and voice calls simultaneously, leaving you with only the ability to call and SMS.
It’s important to understand that a smartphone’s radio module consumes more power when you constantly search for the network, and network-type stabilization will not only improve communication quality, but also have a positive impact on the battery life of your device.
Activation and configuration of VoLTE and HD-sound
VoLTE (Voice over LTE) technology allows voice calls to be transmitted over a fourth-generation network, providing high audio quality and faster connection. On Redmi Note 9 Pro devices, this feature is hardware-enabled, but software can be hidden or disabled by default depending on the firmware region.
To enable, go to Settings → SIM-maps and mobile networks, and find the "Use VoLTE" switch, if you don't have one, you can activate it through a hidden menu. Enter the dialer code ##86583##, after which the message "VoLTE Carrier check was disabled" should appear, which means activation of hidden check and the switch appears in the menu.
What if the code doesn't work?
Use of the HD-Sound requires support from the carrier. SIM-The card has the corresponding service connected, and after activation in the status bar, an icon may appear next to the network indicator "HD" or volte".
- 🔊 The sound becomes purer and more natural, the effect of the “robot” or metallic timbre disappears.
- ⚡ Reduced time to establish a connection with the subscriber.
- 🌐 Ability to talk and use high-speed internet at the same time.
Resetting and Correcting APN Access Points
Incorrect settings of access points (APN) They can affect not only the speed of mobile Internet, but also the overall stability of the connection with the operator's gateways. SIM-Redmi Note 9 Pro cards retain old options that conflict with current network settings.
To perform the reset, open the Settings menu → SIM-maps and mobile networks → Choose. SIM → Access points (APN). At the bottom of the screen, click Reset or Restore by Default, which will return factory settings to your operator.
☑️ Checklist of checks APN
In rare cases, you need to manually create a new access point, and the data for this (name, APN, login, password) can be found on the official website of your mobile operator.
| Parameter | Value (example for MTS) | Meaning (example for Beeline) | Value (example for Tele2) |
|---|---|---|---|
| Name (Name) | MTS Internet | Beeline Internet | Tele2 Internet |
| Access Point (APN) | internet.mts.ru | internet.beeline.ru | internet.tele2.ru |
| Type of authorization | PAP or CHAP | PAP or CHAP | PAP or CHAP |
| Type APN | default,supl | default,supl | default,supl |
After making changes, be sure to turn on and off the "Air Message" mode so that the phone re-registers with new settings, an action that often solves problems with the "hang" Internet (E instead of 4G) and improves ping.
Using an engineering menu to amplify the signal
For advanced users who want to get maximum control over the radio module, an engineering menu is available.It allows you to manually adjust the frequency ranges that the Xiaomi Redmi Note 9 Pro uses. This can be useful if you are near the coverage limit of different towers.
You can log in via dialer by dialing ##4636##. Select "Phone Information." You'll see a lot of options here, but we're interested in "Set up your preferred network type."
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Before changing the settings in the engineering menu, write down the initial values on paper or take a screenshot so that in case of deterioration of the connection, everything can be returned as it was.
In the list of available modes, you can choose options that force the use of certain LTE bands (for example, Band 3, Band 7, Band 20), and you can experimentally find out at what frequency in your home or office signal is most stable.
⚠️ Warning: Unthinkingly changing the parameters in the engineering menu can lead to complete loss of communication. Do not turn off the main ranges unless you are sure that your operator has them in the area.
You can also test the radio module by running a “Ping test” or “Connection test” to get objective data on the quality of the communication channel in real time.
Resetting network settings and software updates
If software failures have accumulated in the system, a simple reboot may not be enough, and in such cases, resetting the network settings is an effective solution. It is important to understand that this step will remove stored Wi-Fi passwords and associated Bluetooth devices, but return the network settings to the factory state.
You can reset via Settings → Connection and Sharing → Reset Wi-Fi, Mobile Networks and Bluetooth → Reset. After this procedure, the phone will restart and you will need to re-enter passwords from wireless networks.
Not to forget about system updates. Xiaomi regularly releases security patches and improvements for the MIUI shell, which often contain corrections for modem errors. Check for updates in the Settings → About phone menu.
- 🛠 Reset eliminates configuration file conflicts.
- 🔄 Firmware updates optimize antennas.
- 🚀 Compatibility with new operator communication standards is improved.
Regular maintenance of the smartphone software is the key to its stable operation, and ignoring updates can lead to the fact that the phone will no longer work properly with the upgraded equipment of cell towers.
Influence of protective accessories and body
Often users forget that the physical environment of the smartphone plays a key role in the reception. The antennas in the Redmi Note 9 Pro are located around the perimeter of the body, and some materials can shield the signal, especially cases with metal inserts, magnetic fasteners or a thick layer of metal at the back.
If you take off the cover and check the signal level, if the difference is significant, you should consider replacing the accessory with a more "transparent" accessory for radio waves, for example, made of silicone or thin plastic, and metal bumpers can create a "Faraday cell" effect, blocking GPS and cellular signals.
Also, the way you hold your phone affects the quality of your communication, and if your palm completely covers the bottom or top of the back, it can weaken the signal. In modern smartphones, antennas are spaced to minimize this effect, but in low-coat conditions, the death grip can cause the call to break.
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Metal and thick rubber covers can reduce signal strength by 10-15%, which in border areas is a critical factor in communication loss.