[Photo] FMA9901A FM â€‹â€‹broadcast dedicated antenna

Due to the rich content, good sound quality, wide frequency response and good quality of FM radio, the upper limit of the audio frequency response of FM radio can reach 15000Hz, especially the advent of FM stereo broadcasting, which is more popular among the public, so many audio enthusiasts regard FM radio as An emerging sound source. Although many users are using some top-of-the-line FM tuners, when the signal-to-noise ratio of the received radio station is close to or lower than the receiving sensitivity of the radio, the output audio signal cannot achieve high-fidelity effects, or even receive them. Usually the outdoor field strength is more than 15 decibels stronger than the indoor field, making outdoor antennas have a "congenital advantage" compared to indoor antennas, and the outdoor can be built with a large high-gain multi-unit antenna, so the FM-HiFi system is set up When not only choosing an ideal FM receiver, the antenna is also a non-negligible part.

The FMA9901A receiving antenna introduced in this article is an outdoor antenna specially used for various FM tuners. Since this antenna was launched in 1999, it has been well received by many domestic FM radio listening enthusiasts. The antenna is composed of five major parts: FM broadcast special antenna frame, high gain antenna amplifier, steering motor, 16m coaxial cable, power box and so on.

The FMA9901A FM â€‹â€‹broadcast antenna uses a folded half-wave vibrator type three-unit antenna frame with a reception center frequency of 100MHz, and the vibrator uses a plated 8mm hollow aluminum tube. Figure 1 shows the actual dimensions of the antenna frame for reference.

The amplifier consists of an FM filter circuit, a low-noise amplifier transistor, a rectifier circuit, and a steering control circuit. Figure 2 is the principle diagram of the antenna amplifier. After the signal is received by the antenna, the impedance transformation of 300Î©-75Î© is completed by the impedance converter B1, and the input loops L1, L2, C1, and C2, C3, L3 form a T-shaped low Pass and high-pass filters, so that the entire amplifier pass band is limited to 80MHz-110MHz, in order to filter out VHF signals other than FM, improve the amplifier's anti-interference ability. Because the signal received by the antenna varies in strength, in order not to distort the output level of the amplifier beyond the maximum output level, and the amplifier cannot effectively amplify the weak signal with a very low signal-to-noise ratio, only a low noise NEC3356 (the performance is the same as 3358) microwave tube for signal amplification, output by the high-pass filter composed of C5, C6, L4, L6, C13 constitutes high and low frequency separation circuit, 12V straight (AC) current voltage is added to the antenna amplifier (motor) through L6 ) Due to the role of C13, the 12V direct (AC) current voltage will not enter the FM receiver. The FM signal is coupled into the FM receiver through C13. Because L6 has the effect of blocking high frequencies, the FM signal will not enter the power supply.

The above antenna frame and amplifier only form a high-gain unidirectional reception. In order to achieve all-round high-gain reception, the antenna is also equipped with a steering device, the motor uses a 12V AC permanent magnet synchronous motor, the external speed is 4 rpm, and the torque is greater than 4 Kilograms, the failure rate is less than 2% within 1 year. Due to the low voltage and small current operation, the power of the motor, the power of the amplifier and the frequency modulation signal are all transmitted on the 14-meter 75Î© coaxial line, making the operation very safe and convenient. Press K, the turn indicator D3 lights up, 12V AC power is supplied to the motor through C12, the motor M starts to work, and it will not interfere with the broadcast when rotating.

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FAQ

Q1. What is the MOQ?
XDEC: 2000pcs for one model.
Q2. What is the delivery lead time?
XDEC: 20 days for normal orders, 15 days for urgent orders.
Q3. What are the payment methods?
XDEC: T/T, PayPal, Western Union, Money Gram.
Q4. Can you offer samples for testing?
XDEC: Yes, we offer free samples.
Q5. How soon can you send samples?
XDEC: We can send samples in 3-5 days.

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