Homemade simple remote control TV antenna ----- Remote Control Antenna

500M FM FM transmit circuit, 500M FM Transmitter Keywords: 500M FM FM transmit circuit 500MFM FM transmit circuit This article describes the small power frequency frequency frequency transmit circuit, due to the use of dedicated transmit tubes, the degree of adjustment, does not produce amplitude modulation, distortion, far delivery distance, stable operation. The circuit is simple and easy, as long as the welding is incorrect, the circuit principle is shown in Figure 1. In the circuit, a high-frequency oscillator, a high-frequency oscillator that is formed in the range of 88 to 108 MHz, and the audio signal picked up by the elective microphone is enlarged by T1, and the amplified low frequency signal is again. High frequency carrier is modulated. If the host microphone M is turned off, the music signal can be transmitted well when the output is connected to the player output. It should be noted that the radio frequency emission dedicated tube T2 is required, and its model is FF501, using a standard T0-92 package (like a 9000 series triode), the shape and pin arrangement are shown in Fig. 2, and the ICM is 45 mA, ft is greater than 1. 3GHz, VCEO is 13V. The advantages of the dedicated tube are good consistency. The radio frequency output power is large, and the circuit is easy to adjust. The FF501 can operate at a higher frequency band, and the reader can attempt to use the transmit tube for high frequency emission experiments of other circuits. The L2 in the circuit uses the ∮ 1.0mm enameled wire in the bull of 5 ∮ 5.1mm to 0.8cm, C3 ~ C8 available high-frequency porcelain card, the antenna is best used with a rod of 1.2 meters. And stand vertically. The antenna must have a good back to power. The working current of the circuit is about 25 ± 5 mA. If the emission frequency is not in the range of 88 to 108 MHz, the length of the resonant coil L2 can be appropriately adjusted. After the circuit is adjusted, it is received by the FM segment to the radius, and the effective transmission radius can reach 500m.

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