"Qingque, have you ever tested this thing? What is the maximum communication distance?"
In the Qiquge Workshop, the scientific research base of the killer project, after trying this first-generation telephone several times, Li Zexuan called Li Tai over and asked calmly.
He really didn't expect that the killer project would progress so quickly. At the beginning, he thought that Datang would have to wait until next year at the earliest if it wanted to make "high-end goods" like telephones!
"Shan Zhang, Mr. Mo Chui and I have tested this before. When the distance is as far as one mile, the sound cannot be heard clearly! We initially thought it was because of the loss of electric energy during transmission, but we tried to increase the power supply voltage. , it will still be like this! Well, there were two experimental products that were burned out because the voltage was too high~!"
At the end of the sentence, Li Tai scratched You, looking embarrassed.
Li Zexuan was speechless when he heard this: "Of course you can't blindly increase the voltage in this case. Some components in the phone have a certain withstand voltage. If you blindly increase the voltage without any basis, the things inside will definitely cause damage." Irreversible damage!”
Li Tai said with some embarrassment: "The mountain chief taught me a lesson! It's Qingque Menglang~!"
He hadn't been exposed to electricity for very long. It was already very difficult to build a telephone based on the ideas and ideas provided by Li Zexuan. As for other details, how could he be so thorough~
Li Zexuan shook his head and said: "Qingque, it's your first time to take on a big project like the trump card project. It's not easy to find ways to solve problems when you encounter them. Engineering is a science that constantly explores the truth through experiments. Failure is not terrible, what is terrible is that you keep holding back because you are afraid of failure!”
At this point, Li Zexuan changed the topic and continued: "But I still hope you can pay attention to safety during the experiment! You increased the voltage rashly before and burned things out, causing the components to be broken down by high voltage and causing leakage. That’s the big deal! Before making a decision, you must think it over carefully and anticipate the consequences in advance!”
This is not an alarmist statement by Li Zexuan. The first-generation telephone made by Li Tai was a simple circuit composed of some components connected through wires. It was very rough. After all, this era did not have as advanced integrated circuit technology as modern ones, and even Even Li Zexuan is having a hard time getting together the raw materials for making circuit boards!
In addition, there are many capacitors, diodes and transistors in the circuit of the telephone. Once something is broken down due to excessive voltage, it is entirely possible that leakage will occur. At that time, the person holding the telephone in his hand is likely to be directly electrocuted. died!
Hearing Li Zexuan's solemn words, Li Tai's face also became serious. He solemnly raised his hands and said: "Remember the instructions of the mountain chief!"
Li Zexuan nodded happily. The little fat man in front of him was Li Er's treasure. He could arrange for him to do scientific research, but he must not let this little fat man play with his life, otherwise Li Er would definitely not give him good things to eat. !
Therefore, Li Tai’s safety education must be kept up!
"But Chief Shan, why is the transmission distance of this telephone only one mile~? This problem has been bothering Mr. Mo Chui and me for a long time~!"
After a moment of pause, Li Tai returned to the topic and asked.
The major that Li Zexuan studied in his previous life can be called orthodox engineering, because it includes the most important engineering branches of optics, mechanics, electricity, and arithmetic. Li Zexuan also knows a lot about communications, thinking to himself After a moment, he slowly spoke:
"Qingque, although I have never disassembled your telephone, I also know that it can be roughly divided into two parts, the transmitter and the receiver. One is responsible for converting the sound signal into an electrical signal and transmitting it, and the other is It is responsible for converting the received current signal into a sound signal, thus forming a complete loop that can transmit sound over a long distance.
But this is only an ideal model. When it is actually used, it will encounter many problems. For example, the transmission distance you mentioned before is short, only one mile! That's because you didn't take into account signal loss and noise in the line when you made the phone! "
Hearing this, Li Tai asked doubtfully: "Shan Zhang, I know that this current will be lost during the transmission process, but what do you mean by line noise?"
Li Zexuan thought for a while and replied: "To put it simply, in a circuit, noise is some electrical signals that we don't need but do exist! We just talked through the phone, Qingque, you should be able to hear the inside of the phone In addition to my voice, there are some other "sizzling" sounds, which are caused by electrical signal noise!
When the distance between the two ends of the phone becomes longer, there will be more and more noise sources, coupled with the loss of useful signals, you will not be able to hear the other party one mile away. The sound is not surprising~! "
In fact, the first-generation telephone that Li Tai is making is very similar to the first telephone made by Bell. It simply completes the mutual conversion of acoustic and electrical signals, but he did not consider the issues of modulation and noise!
First of all, the frequency of the current signal output by the telephone is very low, and the recognition is also very low. In the low frequency domain, there is a lot of noise. Therefore, in modern society, many people have added the output end of the telephone based on Bell's research. Modulator, by increasing the frequency, increases the recognition of useful signals and facilitates long-distance transmission;
Of course, this modulator cannot adjust the frequency too high, because in wired transmission, high-frequency signals will have huge transmission losses. Generally, only in wireless transmission, the signal will be modulated to a very high frequency;
With a modulator, there must be a demodulator. In improved telephones after Bell, a demodulator will be added to the front end to demodulate the signal. In addition, a filtering system will be introduced to filter out low-frequency spurious noise. …
Regarding the detailed principles of telephones, even if Li Zexuan talked to Li Tai for a whole day, he might not be able to explain them all, because when it comes to the concept of frequency domain, he has to mention two super masters - Euler and Fourier. It’s too troublesome to talk about these two people’s “famous skills”!
Even if Li Zexuan can explain it clearly, Li Tai may not be able to understand it. After all, concepts such as Euler's formula, Fourier transform, and Fourier series have stumped countless college students in modern society!
So Li Zexuan simply put forward two possible reasons. As for the truth behind it, let Li Tai slowly explore it through practice and setbacks! You can't eat a big fat person in one bite, right~
Li Tai held his chin, stood there and thought seriously for a long time, and finally looked up at Li Zexuan and said: "Chief, I roughly understand what you mean! But... But I still don't know how to reduce the signal transmission. Loss, I don’t know how to remove the noise sources you mentioned! Please ask the mountain chief to clarify my doubts!”
Having said this, Li Tai bowed to Li Zexuan very sincerely.
For him, a "native" of the Tang Dynasty, what Li Zexuan said before was too profound! But Li Tai likes challenges by nature. The more profound something is, the more he wants to understand it. What Li Zexuan just said successfully aroused his thirst for knowledge! He wants to find the truth!
"Ahem! Qingque! This question is rather profound. It is a bit out of the ordinary for you now. The engineering courses involved can only be learned in two or three years. Even if I tell you now, you will only learn I can listen to you with a little understanding!"
Li Zexuan shook his head and rationally chose to avoid the question. Li Tai opened his mouth unwillingly. Just as he was about to speak, Li Zexuan interrupted directly:
"Okay! Let's not discuss this problem for now. I will provide you with a feasible solution later. Now let's talk about the improvement of the telegraph machine!"
The main purpose of the second trump card project of Yanhuang Academy is to improve the existing telegraph machine so that it can achieve ultra-long-distance wireless communication. A large part of this work was actually completed before Li Zexuan left Lantian County and went north to fight the locusts. , the telegraph machine he brought north at that time was an improved one.
After hearing Li Zexuan say that he would provide a feasible solution in a while, Li Tai gave up and pondered for a moment before replying:
"Mr. Shan, the transformation work of the telegraph machine has basically entered the final stage. Now the transmission power of our telegraph machine has increased fifteen or six times than before, and a detector has been added inside the telegraph machine. In this way, the telegraph machine The ability of machines to identify electromagnetic waves is stronger than before! Next, the students plan to lead people to establish telegraph relay stations in Taiyuan and Yunzhou to conduct telegram receiving and sending relay experiments. Once these two relay stations are completed, they can be directly deployed in Chang'an Send a telegram to the hinterland of the prairie!”
Hearing this, Li Zexuan glanced at Li Tai with admiration, because the construction locations of the two telegraph relay stations chosen by Li Tai were very meaningful. In more than two months, the Tang Dynasty will send troops to the Turks. If the relay station can really If it is completed before the war between the two countries, it will definitely be unparalleled good news for Datang. This means that the Tang army will be completely invincible in terms of messaging!
This little fat man is worthy of being a royal child, and is definitely not something ordinary people can have!
"Well! Qingque, you did a good job! The follow-up will be according to your plan. It is the summer vacation of the academy, and it is just time to gather the strength of all the elites of the academy to help you complete this work! Try to complete these two telegraphs within three months. Let’s build the relay station!”
Patting Li Tai on the shoulder, Li Zexuan encouraged the latter.
"Don't worry, Chief Shan, Tai Ding will go all out!"
Li Tai solemnly cupped his hands and responded.
After a while, Li Tai frowned again and said: "Chief Shan, Taiyuan and Yunzhou are far away from Lantian County, and there are no hydropower stations there. It is unrealistic to pull the line out, so how to solve the power supply problem of this telegraph relay station? "
Li Zexuan frowned. He really ignored this question!
The reason why a telegraph relay station is called a relay station is that its transmission power must be greater than the transmission power of the telegraph machine itself. It may not be able to last long solely relying on battery power supply, but as Li Tai said, there are no hydropower stations in those two places, and the second is that they are far away from Ba, Lantian County. The river hydropower station is too far away, so power supply is indeed a big problem!
After pondering for a long time, Li Zexuan said slowly: "Then build a small thermal power station locally!"
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