How to play songs on the car radio with a mobile phone?

1. The driving computer of the car must support Bluetooth connection. (It must be Bluetooth 2.0 or above, otherwise the mobile phone cannot be paired, and the IOS mobile phone must be Bluetooth 4.0 of the driving computer, otherwise the IOS device cannot be paired with the driving computer Bluetooth. )

2. After the driving computer supports Bluetooth connection, turn on the Bluetooth of the mobile phone to pair with the Bluetooth on the driving computer. After pairing, the driving computer will use the Bluetooth source as the first sound source. (that is, you can hear a series of sounds from your mobile phone, such as songs, phone calls, text messages, etc. ) Generally, on-board computers have Bluetooth pairing function in the setting interface, and some models have one-button pairing function.

3. At this time, turn on the mobile music player and choose your favorite songs to play. If the car does not have the above configuration, you can buy a car MP3, connect a cigarette lighter and play it through the car radio.

Due to the progress of science and technology, there are many radio waves with different frequencies in the sky. If all these radio waves are received, the audio signal will be like a busy city, with many sounds mixed together and nothing can be heard clearly. In order to try to select the desired program, there is a selection circuit after receiving the antenna. Its function is to select the desired signal (radio station) and "filter out" the unwanted signal to avoid interference. This is the "Select Channel" button that we use when listening to the radio. The output of the selection circuit is the high frequency amplitude modulation signal of a selected radio station. It is not possible to directly push the earphone (electroacoustic device) with it, and it must be restored to the original audio signal. This recovery circuit is called demodulation. When the demodulated audio signal is transmitted to the earphone, the broadcast can be received.

The simpl radio is called a direct detector. However, the high-frequency radio signals obtained from the receiving antenna are generally weak and should not be sent directly to the detector. It is better to insert a high-frequency amplifier between the selection circuit and the detector to amplify the high-frequency signal. Even if a high-frequency amplifier is added, the detected output power is usually only a few milliwatts. It's ok to listen with headphones, but the speaker is too small. Therefore, an audio amplifier is added after the detected output to drive the speaker. High amplifier radio is more sensitive and powerful than direct detection radio, but its selectivity is still poor and its tuning is more complicated. To amplify the high-frequency signal received by the antenna by hundreds or even tens of thousands of times, there are usually several stages of high-frequency amplification, and each stage of circuit has a resonant circuit. When the receiving frequency changes, the resonant circuit must be readjusted, and it is difficult to ensure that the selectivity and passband are exactly the same after each adjustment. In order to overcome these shortcomings, almost all radios use superheterodyne circuits at present.

The superheterodyne is characterized in that the carrier frequency of the selected high-frequency signal is changed to a lower fixed intermediate frequency (465KHz), and then amplified by an intermediate frequency amplifier to meet the detection requirements before detection. In superheterodyne receiver, in order to generate frequency conversion, there is an additional sine signal, which is usually called heterodyne signal. Circuits that generate heterodyne signals are customarily called local oscillations. There is an intermediate frequency difference between the local oscillator frequency of the radio and the frequency of the received signal, so the mixer and the selection circuit before the local oscillator adopt a unified tuning line, such as using coaxial double capacitors (PVC) for tuning, so as to keep the difference at a fixed intermediate frequency value. Because the intermediate frequency is fixed and the frequency is lower than the high frequency modulation signal, the gain of the intermediate frequency amplifier can be made larger, the work can be more stable, and the passband characteristics can be made ideal, so that the detector can obtain enough signals, so that the whole machine can output audio signals with better sound quality.