Now many enthusiasts are playing FM reception, because playing radio is not to say that the machine is good, but also a certain strength of signal input to the receiver and high fidelity amplifier output can be achieved.
Antennas and antenna amplifiers, as we mentioned earlier, many enthusiasts have also bought antennas, and also equipped with good high and low frequency amplifiers, but they can't get their wish and realize their own fever dreams. Of course, the low frequency amplifier, the power amplifier we are talking about, can directly hear the sound quality with the ear, and it is very easy to choose. But the high-frequency amplifier-antenna amplifier, which outputs high-frequency signals, can't really listen to the signal with only ears. If you don't have professional test equipment, it is difficult to tell how the performance is. If you use a receiver To try, you can only set up the antenna, connect the receiver, and install the amplifier before you can try it. This means that you can only try it if you buy it all. If you try this way, if there are no special circumstances, the receiver can receive a good radio signal. , You will feel very excited, and you will be able to enjoy endless fun immediately; but this antenna is not ideal for setting up to listen to radio stations. Usually, when you connect the amplifier, you will receive a signal that is seriously interfered with, even if it is all local. A radio station, the most obvious in some small cities and counties, is to receive a station, and the entire FM frequency is the signal of that station. At this time, you will be too disappointed. It is the same as the antenna. How the phone is tuned is still the signal of that radio station. Because of this, many enthusiasts will never want to play radio anymore, and put those receiving equipments into obsolete antiques.
The above situation is summarized based on the opinions of fans on FM fever. Maybe your situation is the same as them. Here I would like to make a few personal suggestions. In this FM reception, you must avoid irritability, whether it is the antenna The installation of the equipment, the wiring of the equipment, and the debugging of the amplifier should be careful. Many fans may feel that the debugging of this amplifier is a bit esoteric and seems to be very professional. In fact, do n’t worry. The debugging of the amplifier is about adjustment. It is in the best state. The debugging manufacturers of the main amplifying parts have been tuned. The user mainly adjusts the strength of its input signal. Many enthusiasts do not dare to tune it. In fact, it is a potentiometer, like the one in our audio. Like the volume potentiometer, adjust the input signal strength, because the production of the antenna amplifier has a rated amplification value, most of which is the amplification value of the ordinary TV signal. Because the bandwidth of the TV broadcast is much wider than the FM signal, a TV channel is generated. The harmonics are not easy to interfere with other channels, and the FM radio is different, only within 20MHZ, so the amplification value is one At the same time, the signal harmonics are also amplified. Some local stations have strong signals. After amplification, they also generate some self-excited signals. In addition, harmonic signals are mixed together so that the entire FM frequency is a radio station. Therefore, FM enthusiasts must analyze carefully. They cannot be considered to have bad antennas, bad status, bad amplifiers, and bad receivers. Here, I am building a hobbyist who is interested in FM remote reception. After buying the receiver, the antenna, and the amplifier, install the antenna and receiver first. Do not install the amplifier first, because such antenna signals are Without amplification, you can observe how many radio stations you can receive, how the signal is, and how the antenna points to the most radio signal. Then just try your receiver. You can try it with a few machines to see which one is better. There is only one machine enthusiast. Of course, you do n’t have to try it, but many good people will use it. If you think about stereo motors, everyone will use supplements. In fact, the electrical appliances are the same. The situation will be better after replacing the supplements. However, I hope that enthusiasts cannot change them immediately. At least for a few days, the best It's a week or two, look at the phenomenon, whether the unit is poor or the radio signal is poor, don't worry. Regarding the motorcycle, I would like to talk about the most common sound interference phenomenon in the tuner in audio equipment. The stereo output of many receivers does not reduce noise. Fans will add a noise reduction circuit, such as the familiar LM1894 circuit. Everyone I know that the noise reduction circuit mostly uses the principle of two-channel signal comparison to filter and weaken the high frequency, but the principle of FM stereo encoding and decoding is just to perform pre-emphasis mixing and then separate and de-emphasis. The high-frequency part of the left and right signals is the most prominent. Therefore, the essence of noise reduction is to reduce the stereo separation of the receiver. This is a problem of the chip used by the machine. We cannot solve it, so it is not worth it. In fact, many machines use a good core. But the current receiver circuit often has unexpected times, the demodulation core is good, but the intermediate frequency amplification of the previous stage uses an ordinary high-frequency tube, so enthusiasts have to carefully analyze the circuit and carry out Machine, like this, replace with a low noise, higher amplification value tube, such as 2SC1674, it is best to add a two-stage intermediate discharge circuit; the first high-level amplifier may be a 9018 high-frequency tube, enthusiasts It can be replaced with a low-noise tube with a higher amplification value, such as a C3358 tube. After replacing it, I believe that the noise of the receiver will be relatively small, and the effect will be better. The last step is to solve the output amplification stage. Most receivers will use 4558. Usually fans will think of replacing a superb 5532. I hope that fans will pay attention to determine whether the 5532 you are replacing is genuine. If the original 4558 is genuine The NE5532 you are currently replacing is a defective product, which one may be worse. This must be replaced reasonably! Needless to say, capacitors will use tantalum capacitors. Another point is also very important. Now the digital clock leakage of many digital receivers is very serious. When the stereo indicator is on, the high-order harmonics of the clock signal have a great interference on the 38KHZ stereo demodulated signal, and the middle and high frequency noise is very harsh. It becomes very quiet when it is mono. This situation is due to the improper design of the circuit's filtering and digital ground. The solution is to strengthen the power supply filter first. All the power capacitors on the circuit must be doubled. The power supply on the related circuit is preferably connected to a 1000P capacitor. Due to the ground of the digital circuit Oscillation will occur when bending for a long time, so the ground wire of the digital circuit should be connected to the power ground wire with the shortest thick wire. The ground wire of the circuit board should be distributedly connected to the outer iron shell. After completing these, the receiver will relatively reduce noise . Note that not all phones are so bad. Never change a beautiful phone to a bad one. Be sure to analyze it carefully. Our hobby of FM reception is not only exciting for listening to more radio stations, but also a good one. Machine is also a joy of success! After the receiver is completed, the antenna amplifier can be installed, and the antenna amplifier should be installed. Everyone must pay attention to the debugging mentioned above, that is, to adjust the input strength resistance, until the signal is best, some amplifiers without adjustment, enthusiasts It can be installed by yourself, use only 10K potentiometer (the smaller the volume, the better), the string is on the input side.
I hope that the above experience will allow you to reproduce the style of the long-standing radio, I wish you all success, as expected! Welcome to contact to discuss together! (E-mail :) Related sites:
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