Low-power FM transmitter circuit diagram 1000M range
Posted on Nov 10, 2015 3897
Under: FM Transmitter Circuits
I used the components on hand, comprehensive reference
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Beijing newsletter and other newspapers related to the production of articles made with a long-range FM radio transmitter operating within 88--108MHZ band in his spare time to play music. .png">Circuit principle now, see photos. (1) for the power section, and then be rectified mains step-down regulator, stable 12V DC for RF circuits. RF circuit consists of a high-frequency oscillator, buffer amplifier, the final PA and antenna. High-frequency oscillator for generating a carrier frequency signal, frequency falls within 88--108MHZ and complete the frequency amount of sense to change the transmission frequency. VT1 RF signal output from the transmission pole, to VT2, L2, C22, R4 composed of buffer amplifier power boost, and reduce the impact of the final stage amplifier circuit of the oscillator. Final stage prop narrowband high frequency amplification, RF power is further amplified by the C25 is coupled to the transmitting antenna to the surrounding space radiation. If the connections are sound source output signal amplitude is too large, the need to string into the weak resistance, in order to avoid sound distortion. Available Bonded Copper circuit board production, the wiring should pay attention to the impact of distributed capacitance. FIG Capacitor units marked figures, all to "pF" as a unit, and to the high-frequency ceramic capacitors. VT1 - VT3 UHF NPN silicon tube, such as 9018, B 60, Icm = 50mA.fr = 600MHZ.VT3 power can also be used in the launch tube C2053, BF96S, etc., may be farther away from launch. L1-L3 enameled with 00.8mm on a 04mm screw pen made of tightly wound four laps prolapse. Antenna rod antenna having a length of 1/4 wavelength of the frequency (or 1/2). The transmission frequency is 100MHZ, the antenna length 0.7m (or 1.5m) Production should be step by step installation. RF part of the first load oscillator, buffer amplifier, adjust so that the distance between the turns L1 frequency falls no station at the pointer type multimeter black pen contact with the collector VT2, adjust L2 pointer deflection amplitude maximum, (ie power maximum). If there is the phenomenon of playing table, the table can be wrapped around the pen together until not hit the table so far. Then use the same method of adjusting the L3, so that the final output maximum power. Search the FM radio transmitter at a distance of 10 meters where the transmitted signal, about the estimated transmission frequency, connect the antenna properly adjusted length, can be put into use. When the machine power supply voltage measured 12V (6-15V can actually work within, the higher the voltage, the more distance away), operating current of only 45mA or so, the transmission frequency of about 104MHZ, placing third floor balcony, in the absence of excessive building the barrier at the situation, with the popularity of the machine (chip CXA1019M) received from as high as 1000 meters.