![]() Lyzhin R, Radiokonstruktor 2003, November. The choke has 50 turns of 32.38 AWG enameled wire. The RF choke L2 is wound on a ferrite toroidal core of 7 mm in diameter. This design uses the same ferrite rod antenna as the previous one. Note, the diode D1 is connected into bias circuit of the transistor T2, such configuration increases the sensitivity of the detector because of a DC current passing through the diode D1. The amplified RF voltage goes from the first stage through the capacitor C3 to the envelope detector with the diode D1, and the audio signal goes from the envelope detector to the audio amplifier based on the transistor T2. The RF choke L2 is connected in collector circuit of transistor T1. The resonant tank connected to the RF amplifier (transistor T1) in the same way as it connected in the previous circuit (fig. The output of this receiver is connected to stereo headphones with the summary impedance not less than 32 Ω, so the quality of the sound is better. It works with the lower power supply of 1.5 Volts. The second circuit of the radio receiver is shown in figure 2. The adjustment of the circuit is quite simple - match the value of R1 to get the sound in headphones as loud as possible. The coil L1 has 90 turns of 26.32 AWG enameled copper wire, tapped at the 10th turn. Here we have tried to enhance the design such that the amplitude becomes considerably magnified in order to turn OFF the transistor completely during the oscillations. The coil L1 is wound in one layer on a ferrite rod of 8 mm in diameter (permeability μ e=400), with the length of about 70 mm. How the One Transistor FM Radio Receiver Works As mentioned above, the circuit is basically a single transistor superregenerative RF oscillator with a constant amplitude. This receiver works with headphones, the summary resistance of LS1 must be not less than 1500 Ω. This stage not only amplifies the signal, but also demodulates the AM radio signals. The amplified signal voltage from the collector T1 goes to the base of the transistor T2. The transistor T1 amplifies the RF signal. This coil and the variable capacitor C1 are resonant tank elements of the ferrite rod antenna that receive RF signals of radio stations. The bias voltage at the base of the transistor T1 is set by the resistor R1, the bias current goes through the coil L1, its resistance for DC is almost zero. Both transistor stages are connected without an inter-stage coupling capacitor. The circuit diagram shown in figure 1 is quite unusual. An AM receiver detects amplitude fluctuations in the radio waves at a specific frequency.Here are two simple circuits of radio receivers for Middle Wave band, working with headphones.A radio receiver comprises a Radio Frequency (RF) area, an RF-to-IF converter (mixer), an Intermediate Frequency (IF) area, a Demodulator, and an Audio speaker. The radio receiver uses to optimize for that frequency. All stations have set a fixed carrier frequency for sufficient selectivity.įor the modulator to work with any radio signal, we convert the carrier frequency of any radio signal to Intermediate Frequency (IF). By tuning to the channel, you are tuning the nearby oscillator and RF tune-able channel at the equivalent time. RF-to-IF receivers incorporate an oscillator with a variable frequency (differs from RF carrier frequency). There are two stages of AM receiver which are RF and IF (filtering and amplification). Inductor coil is equivalent to 80 turns of 26 s.w.g enameled copper wire twisted on a toilet paper roll. And afterward, the signal identifies by the OA91 diode and amplify by the BC547 transistor. ![]() It gets the signals through the antenna which is a receiving wire. The 80 turns inductor and 365pF variable capacitor structure a loop circuit. The schematic that appeared above is a basic AM receiver circuit that utilizes just a single transistor and some different segments. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |