Smartphone Xiaomi Redmi 3S, released in 2016, still remains popular among car enthusiasts due to its reliability and low price. However, many owners do not know that this device can be used as FM transmitter for transmitting music or podcasts to a car's standard radio without Bluetooth. This solution is especially relevant for older machines that lack modern connection interfaces.

In this article we will look at how to turn Redmi 3S into a full-fledged transmitter, what applications are suitable for this, and what nuances are important to consider when setting up. We will also consider alternative methods of audio transmission (via AUX, Bluetooth adapters) and typical errors due to which the connection may be interrupted. If you want to listen to music from your phone through your car speakers without spending money on expensive equipment, this guide is for you.

Can Xiaomi Redmi 3S be used as an FM transmitter?

Technically Xiaomi Redmi 3S is not equipped with a hardware FM transmitter, like some specialized devices (for example, Nulaxy KM18 or Anker Roav). However, a smartphone can be made to simulate the operation of the transmitter programmatically - through applications that modulate the audio signal into the radio frequency range. The effectiveness of this method depends on:

  • 📶 Radio sensitivity - cheap models may not pick up a weak signal.
  • 📱 Android versions - on Redmi 3S worth it out of the box MIUI 7/8 based on Android 6.0, which limits the choice of software.
  • 🚗 Interference level — in a city with a large number of radio stations, it is more difficult to find a free frequency.

It is important to understand that software transmitters work only at frequencies 87.5–108.0 MHz, and their signal power is several times lower than that of specialized devices. If your radio does not pick up stations well at the edges of the range, it is better to consider alternative connection methods (more on them in the next section).

📊 How do you usually listen to music in the car?
Via Bluetooth
FM transmitter
AUX cable
USB flash drive
Other

Top 3 applications for transmitter on Redmi 3S

Not all programs from Google Play compatible with Xiaomi Redmi 3S due to the limitations of the iron platform (Qualcomm Snapdragon 430) and Android versions. We tested dozens of options and selected the three most stable:

Application Compatible with Redmi 3S Pros Cons
FM Transmitter (from Simple Design Ltd.) ✅ Works on MIUI 7–9 Simple interface, manual frequency setting, low power consumption. Advertising sometimes interrupts the connection.
FM Radio Transmitter (from Smart Kit 360) ✅ Requires Android 5.0+ Support for playlists, equalizer, broadcast recording. Plugins in the free version, the phone gets hot.
Carcorder (from NLL Apps) ⚠️ Works with lags on MIUI 8 Auto search for free frequency, minimalistic design. No Russian language, rare flights.

To install any of these applications:

  1. Go to Settings → Advanced → Privacy and enable the option "Installation from unknown sources".
  2. Download the APK file from the developer's official website (do not use third-party repositories!).
  3. After installation, launch the application and grant access to microphone (necessary for signal modulation).
⚠️ Attention: When using software transmitters Redmi 3S may overheat. Monitor the temperature of the case - if the phone becomes hot, take a break for 10-15 minutes.

Step-by-step setup of an FM transmitter

To configure audio transmission from Xiaomi Redmi 3S to the radio, follow these steps:

  1. Select a free frequency.

    Turn on the radio on your stereo and find an empty channel (no noise or stations). Usually this 87.6 MHz, 87.8 MHz or 107.8 MHz. In cities, free frequencies are less common - you'll have to experiment.

  2. Launch the transmitter application.

    Open installed software (for example, FM Transmitter) and enter the selected frequency manually. Some applications have an auto-search function - it is better not to use it, as it often makes mistakes.

  3. Set up your audio source.

    In the application settings, specify where the audio will be broadcast from:

    • 🎵 Music - from a standard player or Spotify.
    • 🎙️ Microphone — for voice transmission (for example, for hands-free conversations).
    • 📱 System sounds — notifications, navigator.
  • Check the connection.

    On the radio, tune to the same frequency as in the application. If you hear interference, try changing the channel or turning down the volume on your phone to 70%.

    • ☑️ Checking the functionality of the transmitter

    Done: 0 / 4

    If the sound is interrupted or distorted, try:

    • 🔌 Connect your phone to charge (some applications limit performance when the battery is low).
    • 📴 Disable Wi-Fi and mobile data - they can cause interference.
    • 🔄 Restart the transmitter application.

    Alternative ways to transmit sound to a car

    If the FM transmitter is unstable, consider other connection options Redmi 3S to car audio system:

    1. AUX cable (3.5 mm)

    The most reliable and high-quality way is to connect via AUX input. To do this:

    • 🎧 Buy a cable microUSB → 3.5 mm jack (if your phone does not have a standard audio output).
    • 🔌 Connect one end to the phone, the other to the socket AUX IN on the radio.
    • 🎛️ On your phone, select output to external device.

    Cons: Wires can get in the way, and some cars have the AUX jack hidden in the glove compartment.

    2. Bluetooth adapter for radio

    If the car does not have Bluetooth, but has AUX or USB, you can use an external adapter (for example, TaoTronics TT-BA07 or Mpow BH129). It connects to the power from the cigarette lighter and transmits sound via Bluetooth to the phone, and then outputs it to the speakers via 3.5 mm or FM.

    3. USB flash drive with music

    The most universal, but inconvenient way is to record music on a flash drive and play it through the USB port of the radio. Suitable for older machines where there are no other interfaces. Cons: you need to constantly update playlists, no streaming.

    💡

    If your radio supports Bluetooth, but your phone doesn’t see it, try resetting the network settings to Redmi 3S: go to Settings → Bluetooth, click on the three dots in the upper right corner and select "Clear cache".

    Typical problems and their solutions

    When using Xiaomi Redmi 3S As a transmitter, users face several common problems. Let's look at their causes and solutions:

    Problem Possible reason Solution
    No sound on the radio Incorrect frequency or low signal strength. Try frequencies 87.6 MHz, 88.0 MHz or 107.8 MHz. Increase the volume on your phone to maximum.
    Strong interference A radio station is broadcasting near the selected frequency. Use broadcast scanning applications (for example, Radio Scanner).
    The app crashes Lack of RAM or conflict with MIUI. Close background applications, clear cache in Settings → Applications.
    The phone is heating up High processor load when modulating the signal. Reduce screen brightness, turn off GPS and Wi-Fi.
    ⚠️ Attention: If, after connecting the transmitter, the radio starts to emit a high-frequency squeak, immediately turn off the phone. This is a sign of frequency incompatibility or damage to the smartphone's audio chip.

    On Xiaomi Redmi 3S With MIUI Global firmware 8.5.2.0 and later, audio modulation may not work through some applications due to restrictions in Xiaomi's security policy. In this case, installing custom firmware will help (for example, LineageOS), but this will void the warranty.

    Comparison with hardware FM transmitters

    Software solutions are inferior to specialized devices in a number of parameters. The table below shows the comparison. Xiaomi Redmi 3S with popular hardware transmitters:

    Parameter Xiaomi Redmi 3S (software) Nulaxy KM18 Anker Roav T1
    Signal strength Low (up to 5 m) Medium (up to 10 m) High (up to 15 m)
    Sound quality Average (interference, noise) Good (clean signal) Excellent (A2DP support)
    Autonomy Depends on phone charge Powered by cigarette lighter Powered by cigarette lighter
    Additional features Audio transmission only USB charging port, hands-free Bluetooth 5.0, voice assistant
    Price Free (only phone required) ~1 500 ₽ ~2 500 ₽

    Hardware transmitters are superior in stability and quality, but require additional costs. Redmi 3S as a temporary solution is suitable if:

    • 🚗 You rarely use music in the car.
    • 💰 Budget is limited.
    • 🔧 You are ready to put up with interference and settings.
    💡

    For constant use in the car, it is better to buy a separate FM transmitter - this will eliminate problems with interference, overheating of the phone and an unstable connection.

    Use of software FM transmitters in Russia and most countries not prohibited, but there are a few important points:

    1. Radiation power.

      The smartphone emits a signal power less than 100 nW, which does not require licensing. Hardware transmitters (for example, Nulaxy) are also subject to this restriction.

    2. Interference with other devices.

      If your signal interferes with radios or emergency services (for example, 68 MHz in some regions), this may be considered a violation Federal Law No. 126-FZ "On Communications".

    3. Use on the move.

      It is prohibited to adjust the transmitter while driving Traffic rules clause 2.7 (prohibition on the use of telephone devices without hands-free). All manipulations must be performed in the parking lot.

    Europe and the US have similar regulations, but some countries (such as Germany) restrict the use of FM transmitters in cars prohibited due to the risk of interference with emergency services. Before traveling abroad, check local regulations.

    What happens if you use the transmitter on the emergency frequency?

    In rare cases, a weak smartphone signal can interfere with emergency or police radio equipment. For recording such an incident, a fine of up to 5,000 rubles is provided (Article 13.3 of the Code of Administrative Offenses of the Russian Federation).

    FAQ: Frequently asked questions

    Is it possible to use Redmi 3S as a transmitter without the Internet?

    Yes, transmitter apps work offline. The Internet is only needed to download music (for example, in Yandex Music or Spotify You can save tracks to your phone in advance).

    Why doesn't the radio receive a signal from the phone?

    The reasons may be as follows:

    • Weak signal - try moving the phone closer to the radio.
    • Busy frequency - scan the airwaves for free channels.
    • Radio incompatibility - some older models do not support the range 87.5–87.9 MHz.
    How to improve sound quality when transmitting via FM?

    Some tips:

    • Use audio files in the format MP3 320 kbps or FLAC.
    • Turn off the equalizer on your phone - it may distort the signal.
    • Place the phone in the holder closer to the radio (for example, on the dashboard).
    Is it possible to use the transmitter and navigator at the same time?

    Yes, but the sound of navigation guidance will be transmitted to the radio along with the music. To avoid overlapping sounds, in the navigator settings (for example, in Yandex Navigator) disable music playback through the application.

    Will the transmitter work if the phone is dead?

    No, for software transmitter operation Redmi 3S must be enabled. It is recommended to connect your phone to the cigarette lighter charger to avoid draining the battery while traveling.