FMA9901A FM broadcast special antenna, FM Antenna
Keywords: FM antenna
Due to the rich, the upper limit of the audio frequency response of the frequency of the frequency modulation broadcast, the frequency of the frequency of frequency modulation, the upper limit of the audio frequency response of quality, especially the emergence of FM stereo broadcast, which is more favored, so numerous audio enthusiasts use FM broadcast as An emerging source. Although many users are using some top-level FM tuner, the output audio signal cannot achieve high-fidelity effect when the signal is relared, the reception sensitivity below the radio is lower than the receiving sensitivity of the radio. Usually, the field is strong than the power of the chamber, so that the outdoor antenna has "innate advantages" compared with the indoor antenna, plus outdoor high gain multi-cell antenna, so the FM-HIFI system is formed At the time, it is also necessary to select the ideal frequency modulated receiver, but the antenna is also a portion that is not negligible.
The FMA9901A receiving antenna described in this paper is an outdoor antenna specifically used for various FM tuners. Since the 1999, the antenna has been praised by many FM broadcasts in China. The antenna is composed of five major parts of the FM broadcast dedicated antenna, high gain antenna amplifier, steering motor, 16-meter coaxial, and power box.
The FMA9901A FM broadcast antenna uses a three-cell type antenna, and the receiving center frequency is 100 MHz, and the vibrator is a 8 mm hollow aluminum tube after electroplating treatment. Figure 1 is the actual size of the antenna frame for reference.
The amplifier is composed of an FM filter circuit, a low noise amplifying triode, a rectifier circuit, and a steering control circuit. Figure 2 is the schematic of the antenna amplifier, and the signal is received by the antenna, and the impedance converter B1 is completed by the impedance converter B1, the input loop L1, L2, C1, and C2, C3, L3 constitute a T-type Pass and high pass filters, so that the entire amplifier communication band is limited between 80 MHz-110 MHz to filter out the VHF signal other than the FM, and improve the anti-interference ability of the amplifier. Since the signal received by the antenna is different, in order not to make the output level of the amplifier exceed the maximum output level, in addition, the amplifier cannot be effectively enlarged, so it is only using a low noise. NEC3356 (Performance 3358) Microwave Tube As signal amplification, high pass filter output composed of C5, C6, L4, L6, C13 constitutes a high and low frequency separation circuit, 12V direct (交) stream voltage via L6 plus antenna amplifier (motor Since the action of C13, the 12V direct (lys) stream voltage does not enter the FM receiver, and the frequency modulation signal is coupled into the FM receiver via C13, since L6 has the function of high frequency, the FM signal does not enter the power source.
The above antenna and the amplifier only constitute a high gain unilaterally received, in order to be able to receive all high gain reception, the antenna also sets a steering device, the motor is a 12V AC permanent magnet synchronous motor, the external speed is 4 rpm, the torque is greater than 4 Kg, the failure rate is less than 2% in one year, since the low voltage small current is used, the motor electricity, the amplifier electricity and the frequency modulation signal are transmitted on the 75Ω coaxial line, so that the operation is very safe and convenient, only need Pressing K, the steering indicator D3 lights up, 12V AC power is powered by C12, the motor M starts working, and the broadcast will not interfere when the broadcast is rotated.
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