Otaku Engineer in Great Tang Dynasty

"Qing Que, have you tested this thing, how far can the maximum communication distance reach~?"

In Qiquge Workshop, the scientific research base of Assassin Project, I tried this first-generation telephone several times back and forth. Li Zexuan called Li Tai over and asked indifferently.

He really didn't expect the progress of the killer project to be so fast, thinking that at the beginning he thought that Datang wanted to build a "high-end product" such as a telephone, and it would have to wait until next year at the earliest!

"Shanchang, Mr. Mochui and I tested this before. When the distance was one mile away, the sound was inaudible! At first we thought it was due to the loss of electric energy during transmission, but we tried to increase the supply voltage. , It will still be like this! Uh, two other test items were burned out because of too much voltage~!"

Speaking of the last, Li Tai scratched with a look of embarrassment.

Li Zexuan was speechless and said: "In this case, of course, you can't blindly increase the voltage. Some components in the phone have a certain withstand voltage. If you blindly boost the voltage without any basis, it will definitely cause the contents inside. Irreversible damage!"

Li Tai was a little embarrassed and said, "What the mountain leader taught! It's Qingque Menglang~!"

It hasn’t been long since he came into contact with electricity. It’s already very difficult to build a telephone based on the ideas and ideas provided by Li Zexuan. As for the other details, how can he think so thoroughly?

Li Zexuan shook his head and said: "Qingque, you have undertaken such a big project as the killer project for the first time. It is not easy to find a way to solve problems when you encounter problems. Engineering is a science that constantly explores the truth through experiments. Failure is not terrible. What's terrible is that you keep shrinking from being afraid of failure!"

Speaking of this, Li Zexuan turned his head, and then said: "But I still hope that you can pay attention to safety during the experiment! You have increased the voltage before, and it is a small thing to burn things, causing the components to be broken down by high voltage and cause leakage. That’s the big deal! Before you make a decision, you must think carefully and anticipate the consequences in advance!"

This is not an alarmist talk by Li Zexuan. The first generation of telephones made by Li Tai is completely a simple circuit composed of some components connected by wires. It is very rough. After all, this era does not have the advanced integrated circuit technology of modern times. Even Li Zexuan, the raw material for making circuit boards, is now very difficult to get together!

In addition, there are many capacitors, diodes, and transistors in the telephone circuit. Once something is broken down due to excessive voltage, it is completely possible to cause leakage. At that time, the person holding the telephone in his hand is likely to be directly charged. died!

Hearing what Li Zexuan said solemnly, Li Tai's face also became serious. He solemnly bowed his hands and said, "Remember the mountain leader's teachings!"

Li Zexuan nodded with satisfaction. The little fat man in front of him is Li Er’s baby bump. You can arrange for him to do scientific research, but you must not let this little fat man finish his life, otherwise Li Er will definitely not give him good fruit. !

Therefore, Li Tai's safety education must be kept up!

"But Shanchang, why the transmission distance of this telephone is only one mile~? This problem has bothered me and Mr. Mo Chui for a long time~!"

After a pause, Li Tai returned to the subject and asked.

The profession that Li Zexuan learned in the past can be called orthodox engineering, because it includes the most important engineering branches of light, mechanics, electricity, and calculation. Li Zexuan also knows a lot about the knowledge of communication, and he is indulging. After a while, he slowly said:

"Qingque, although I have not disassembled your telephone, I also know that it can be roughly divided into two parts, a transmitter and a receiver. One is responsible for converting sound signals into electrical signals and transmitting them, and the other 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. In actual use, you will encounter many problems, such as the short transmission distance you said before, only one mile! That's because you didn't consider the signal loss and the noise in the line when you made the phone! "

Hearing this, Li Tai asked puzzled: "Shanchang, I know that this current will be lost during transmission, but what do you mean by line noise?"

Li Zexuan thought for a while, and replied: "In short, in the circuit, noise is some electrical signals that we don’t need, but it does exist! Just now we talked through the phone, and you should be able to hear the inside of the phone. In addition to my voice, there are some other "zizi" sounds, which are caused by electrical signal noise!

When the distance between the telephones at both ends becomes longer, there will be more and more noise sources, and the useful signal will be lost. Under the circumstances, you will not hear the other party from one mile away. It's no surprise that the voice of ~! "

In fact, the first-generation telephone that Li Tai is now making is very similar to the first telephone made by Bell. It simply completes the mutual conversion of acoustic and electrical signals, but he does not consider the issues of modulation and noise!

First of all, the frequency of the current signal output by the phone 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 terminal of the phone on the basis of Bell's research. Modulator, by increasing the frequency, to increase the identification of useful signals, and is conducive to long-distance transmission;

Of course, this modulator can't adjust the frequency too high, because in wired transmission, high-frequency signals will have great transmission loss. Generally, only in wireless transmission will the signal be modulated to a very high frequency;

With a modulator, there must be a demodulator. In the improved phone 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 principle of the telephone, Li Zexuan may not be able to finish it even if he tells Li Tai the whole day, because when the concept of frequency domain is involved, he has to mention two super masters-Euler and Fourier , It’s too much trouble to talk about the "famous stunts" of these two people!

Even if Li Zexuan can explain it clearly, Li Tai may not be able to understand it. After all, the concepts of 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 this, let Li Tai slowly explore in practice and frustration! You can’t eat a big fat guy~?

Li Tai squeezed his chin, stood there and thought seriously for a long time, and finally raised his head to look at Li Zexuan and said: "Shanchang, I know what you mean! But...but I still don't know how to reduce the signal. Transmission loss, I don’t know how to get rid of the noise sources you mentioned! Please answer Shan Chang!"

Having said that, Li Tai bowed to Li Zexuan very sincerely.

For him, the "indigenous person" of the Tang Dynasty, the things Li Zexuan said before are too profound! But Li Tai loves challenges by nature. The more profound things he wants to understand, Li Zexuan's words successfully aroused his thirst for knowledge! He wants to seek the truth!

"Ah! Green bird! This question is rather profound. For you now, it’s a bit beyond the outline. The engineering courses involved can only be learned in two or three years. Now even if I tell you, you can only I can hear a little understanding!"

Li Zexuan shook his head, and wisely chose to avoid this question. Li Tai opened his mouth unwillingly. Just when he wanted to speak, Li Zexuan interrupted:

"Okay! Let's not discuss this problem, I will provide you with a feasible solution for a while. Now let's talk about the improvement of the telegraph machine!"

The main purpose of Yanhuang Academy’s second assassin project is to improve the existing telegraph to enable ultra-long-distance wireless communication. This work was actually completed before Li Zexuan left Lantian County and went north to exterminate locusts. At that time, the telegraph that he brought to the north was improved.

Hearing that Li Zexuan said that a feasible solution would be given in a while, Li Tai stopped then, pondering for a moment, he replied:

"Shanchang, the transformation of the telegraph body has basically entered the final stage. Now our telegraph has increased its transmission power by fifteen or six times compared with before, and a detector has been added to the telegraph. In this way, the telegraph The ability of the machine to recognize electromagnetic waves is stronger than before! Next, the students plan to take people to establish telegraph relay stations in Taiyuan and Yunzhou to carry out telegraph receiving and sending relay experiments. Once the two major relay stations are completed, they can be directly in Chang'an. Send a telegram to the hinterland of the grassland!"

Hearing this ~www.ltnovel.com~Li Zexuan took a look at Li Tai with admiration, because Li Tai chose the construction site of the two telegraph relay stations very meaningful. In more than two months, Datang will send troops to the Turks. If the relay station can really be built before the war between the two countries, it is definitely an unparalleled good news for Datang, which means that Tang Jun can be invincible in message transmission by then!

This little fat man deserves to be a royal child, this kind of thinking is definitely not what ordinary people can have!

"Yeah! Qingque, you did a good job! Follow your plan. Now it’s the summer vacation of the academy. It happens to be able to concentrate the strength of all the elites of the academy and help you complete this work together! Strive to complete these two telegrams within three months. The relay station must be built!"

Patting Li Tai on the shoulder, Li Zexuan encouraged the latter.

"Shanchang rest assured, Taiding will go all out!"

Li Tai arched his hands solemnly and answered.

After a while, Li Tai frowned again and said: "Mountain Chang, Taiyuan and Yunzhou are far away from Lantian County, and there is no hydropower station there. It would be unrealistic if the cable is disconnected, so how can the power supply problem of this telegraph relay station be solved? "

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 itself. It may not be long-lasting to rely on battery power alone, but as Li Tai said, there is no hydroelectric power station in those two places, and the other is a distance from Lantian County. The river hydropower station is too far away, and the power supply is indeed a big trouble!

After pondering for a long time, Li Zexuan slowly said: "Then build a small thermal power station in the local area!"

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