Tips to tune yourself to receive beautiful sound

Nowadays, many enthusiasts are playing with FM reception. Playing with radio does not mean that the sound will be good if the machine is good. It also requires a certain strength of signal input to the receiver and a high-fidelity power amplifier output to achieve it.

We have already mentioned antennas and antenna amplifiers. Many enthusiasts have also bought antennas and equipped them with good high and low frequency amplifiers, but they just can't fulfill their dreams of becoming a fan. Of course, the low frequency amplifier, the power amplifier we are talking about, can be directly heard by the ears, so it is very easy to choose. But the high-frequency amplifier, the antenna amplifier, outputs high-frequency signals, and you can't really listen to the signals with your ears. If you don't have professional testing equipment, it's hard to tell the performance. If you use a receiver to test it, you can only set up the antenna, connect the receiver, and install the amplifier before you can test it. That is to say, you can only test it after you buy everything. If there is no special situation, the receiver can receive a good radio signal, and you will feel very excited and enjoy endless fun immediately; but this antenna is not as ideal as imagined when it is set up to listen to the radio station. Usually, when the amplifier is connected, it will receive a signal that is seriously interfered, and even all the local radio stations are received. The most obvious thing in some small cities and counties is that they receive a station, and the entire FM frequency is the signal of that station. At this time, you will feel too disappointed. No matter how you turn the antenna, it will be the same, and no matter how you adjust the receiver, it will still be the signal of that radio station. Many enthusiasts will never want to play radio again because of this. Once those receiving equipment are put aside, they will become old antiques.

The above situation is summarized based on the voices of FM fans on www.fmsky.net. Maybe your situation is the same as theirs. Here I would like to give a few personal suggestions. In this FM reception, you must avoid being impatient. Whether it is the installation of the antenna, the wiring of the equipment or the debugging of the amplifier, you must be careful. Many fans may think that the term "debugging" is a bit profound and seems very professional when they hear about this amplifier debugging. In fact, there is no need to worry. The debugging of the amplifier means adjusting it to the best state. The main part of the amplifier has been adjusted by the manufacturer. The user mainly adjusts the strength of the input signal. Many fans dare not adjust it randomly. In fact, it is a potentiometer, like the volume switch in our audio. Like the positioner, adjust the input signal strength, because the antenna amplifier is produced with a rated amplification value, most of which are the amplification values ​​of ordinary TV signals. Since the bandwidth of TV broadcasting is much wider than that of FM signals, the harmonics generated by a TV channel are not easy to interfere with other channels, while FM radio is different. It is only within 20MHZ, so when the amplification value is large, the signal harmonics are also amplified. Some local radio stations have strong signals, and after amplification, some self-excited signals are also generated. Adding harmonic signals, they are mixed together, making the entire FM frequency a radio station. Therefore, FM enthusiasts must analyze carefully and cannot be discouraged because they think that the antenna is not good, the location is not good, the amplifier is not good, and the receiver is not good. Here, I suggest that enthusiasts who are interested in FM remote reception should install the antenna and receiver first after buying a receiver, an antenna, and an amplifier, and do not install the amplifier first, because the signal of such an antenna is not amplified. You can observe how many radio stations can be received at your location, how the signal is, and how the antenna is pointed to get the most radio signals. Then it is time to test the condition of your receiver. You can try several machines to see which one is better. Of course, enthusiasts who only have one machine have nothing to try. However, many enthusiasts will tinker with their machines. Think of audio machine tinkering, everyone will use supplements. In fact, all electrical appliances are the same. After replacing the supplements, the situation will be better than before. However, I hope that enthusiasts will not change it immediately. At least listen for a few days, preferably a week or two, to see the phenomenon. Is it that the machine is bad or the radio signal is bad? Don't be impatient. Regarding modifying the machine, I would like to talk about the most common sound interference phenomenon in the tuner of audio equipment. The stereo output of many receivers does not have noise reduction. Enthusiasts will add a noise reduction circuit, such as the familiar LM1894 circuit. Everyone knows that the noise reduction circuit mostly uses the principle of filtering and weakening the high frequency by comparing the two-channel signals, but the encoding and decoding principle of this FM stereo is to pre-emphasize the mixing and then separate and de-emphasize. The high-frequency part of the left and right signals is the most prominent, so the essence of noise reduction is to reduce the stereo separation of the receiver. This is a problem with the chip used in the machine. We cannot solve it, so it is not worth modifying. In fact, many machines use very good chips. But nowadays, receiver circuits often have unexpected situations. The demodulation core is good, but the intermediate frequency amplifier of the front stage uses an ordinary high-frequency tube. Therefore, enthusiasts have to carefully analyze the circuit and modify the machine. For example, replace it with a tube with low noise and higher amplification value, such as 2SC1674. It is best to add a double-stage intermediate amplifier circuit; the front high-frequency amplifier may use a 9018 high-frequency tube. Enthusiasts can replace it with a tube with low noise and higher amplification value, such as C3358. After the replacement, I believe that the noise of the receiver will be relatively smaller and the effect will be better. Finally, the output amplifier stage is solved. Most receivers will use 4558. Usually, enthusiasts will definitely think of replacing it with a top-quality 5532. Here, I hope enthusiasts will pay attention to whether the 5532 you replaced is genuine. If the original 4558 is genuine and the NE5532 you replaced is defective, which one may be worse. This must be replaced reasonably! Capacitors are undoubtedly used by tantalum capacitors. Another important point is that many digital receivers now have serious digital clock leakage. When the stereo indicator light is on, the high-order harmonics of the clock signal have a great interference on the 38KHZ stereo demodulation signal, and the mid-high frequency noise is very harsh. When it is switched to mono, it will become very quiet and good. This situation is due to improper circuit filtering and digital ground design. The solution is to first strengthen the power supply filtering. All power supply capacitors on the circuit should be doubled. It is best to connect a 1000P capacitor to the power supply on the relevant circuit. Since the ground wire of the digital circuit will oscillate when it is bent for a long time, 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 connected to the outer iron shell in a scattered manner. After doing the above, the receiver will have a relatively reduced noise. Note that not all machines are so bad. Don't change a good machine into a bad machine. Be sure to analyze carefully. Our hobby of FM reception is not only to be excited about listening to more radio stations, but also to be able to get a good machine. It is a kind of success! After finishing the receiver, you can install the antenna amplifier. When installing the antenna amplifier, everyone must pay attention to the debugging mentioned above, that is, to adjust the input strength resistance until the signal is the best. For some amplifiers without adjustment, enthusiasts can install them by themselves, using only a 10K potentiometer (the smaller the better) and connecting it in series at the input end.

I hope the above experience can help you restore your radio which has been put aside for a long time. I wish you all success and fulfill your wish! Welcome to contact us for discussion!