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  This time standing in Ma Bu, Lin Hong seemed to have entered a mysterious state, unlike the previous muscle soreness, this time he felt very comfortable.

  Two hours passed quickly, Lin Hong gathered his energy, took a deep breath and felt his mind clearer than ever before, refreshed and invigorated.

  He locked the door and then ran back home to make breakfast.

  Because today is Sunday and he doesn't have school, after finishing breakfast he immediately returned to the scrap collection station.

  This time, he was holding a rectangular brown wooden box with several small circular holes on it.

  It is the "mineral radio" he has been working on recently.

  In fact, this crystal radio had been able to produce sound for a long time, but due to the coil and crystal sensitivity issues, it could only receive a local radio station in Dongling City, and the sound was very unclear, with too much noise, making it impossible to use normally.

  But even so, it really excited Lin Hong for a long time.

  The following days were a process of continuous improvement. For example, the components of the radio were previously scattered and placed randomly, without a dedicated box.

  Later, Lin Hong went to the carton factory to play for a few days. During his free time when no one was paying attention, he used the leftover wood scraps in the factory to personally make this long rectangular box. His father was an employee of the carton factory after all, and he often followed him around, so making a simple box was not a big deal.

  These days, Lin Hong also looked at a lot of information and learned that in order to make the crystal radio receive more stations and clearer sound, it is necessary to have a very good antenna, and the Q value of the coil and variable capacitor should be as high as possible. In addition, the forward voltage drop of the detector should be relatively low, plus highly sensitive and impedance-matched headphones, the reception effect of this radio can even surpass that of professional radios.

  At this moment, the finished product in his hands is the one that has been carefully improved over the past few days. The only unsolved problem lies in the antenna, because a good antenna requires a relatively long metal wire and a large space. Moreover, Lin Hong read in the book that although the antenna is simple, it can easily attract lightning and is very dangerous.

  So, without being sure, Lin Hong temporarily did not dare to take action and make the antenna.

  When Lin Hong arrived at the waste collection station, Old Xu had not returned home yet.

  He carefully observed the antenna made by Old Xu last time in the yard, and found that most of the materials used were iron wires. There are a total of twelve wooden poles in the yard, which are divided into a rectangular shape in one corner of the yard, with several poles standing outside the yard.

  What Lin Hong found strange was that the lengths of these wooden poles were not the same, but were arranged in order from short to tall, and the iron wires on the poles were interwoven to form a long strip-like iron net, which was very spectacular.

  Lin Hong didn't need to guess that these antennas weren't casually wrapped, but were definitely calculated using precise formulas, with every angle having its own rationale.

  There are many books about antennas on Old Xu's bookshelf, but Lin Hong hasn't seen them yet. So now he doesn't quite understand the design of this antenna. It wasn't until much later that Lin Hong found out what kind of antenna it was.

  Finally, Lin Hong found a discharge tube and resistor connected to the ground at the end of the antenna. He knew that this was Old Xu's lightning protection design, which could guide the lightning into the ground safely even if it were struck by lightning from the sky, without damaging the equipment or posing any risk of being struck.

  After observing for a while, Lin Hong came to Old Xu's room and placed his self-made "mineral radio" on the workbench. He then disassembled the antenna from the radio and finally connected it to his own "miner".

  The switch was turned on, and the tongue-shaped earphone on the lid of the wooden box made a "hissing" sound.

  Lin Hong originally wanted to use the horn from a radio as headphones, but later found that it didn't work well. He eventually found this model of tongue-and-groove earphones, type Tian 737, on an old strange hat at a waste collection station and discovered that they worked quite well. Later, he also saw an article in a magazine introducing earphones suitable for the "mining machine", which stated that these earphones had an impedance of 750 ohms, just right for use with the "mining machine".

  Lin Hong kept adjusting the position of the metal pointer on the ore, which was the detector on the "mining machine". The sound in the headphones began to change constantly, and the vague voices of various radio stations gradually appeared.

  "It's indeed like that."

  Lin Hong smiled and nodded, after connecting the antenna given by Old Xu, the reception effect was greatly enhanced. He had just casually adjusted it a few times, and he could already hear several radio stations, one of which was even from the provincial capital, very far away from here.

  He continued to carefully adjust it, and finally, the voice of the "Central People's Broadcasting Station" announcer came through the headphones, with excellent sound quality.

  "Awesome!"

  Lin Hong let out a cheer and jumped up with excitement, his right fist clenched in front of his chest, making a victory gesture.

  This is a radio wave from the capital city of Beijing, more than 1,000 kilometers away. The most crucial point is that he received this broadcast through his own handmade "stone radio".

  After Lin Hong's excitement subsided, his emotions calmed down, and he began to try searching for more radio stations, such as foreign radio stations and his favorite amateur radio stations.

  The final result was disappointing, it couldn't receive foreign radio stations like Old Xu's wireless radio, not even amateur radio stations. Being able to receive radio stations from the capital city was already the limit of this machine.

  He had actually expected this outcome, after all, it was clearly stated in the magazine, he just had a little fantasy in his heart.

  "Crystal radios still have certain limitations." Lin Hong recalled the knowledge he had learned, "Even if the antenna is good, the received wavelength is very limited. It seems that to receive a wider range of frequencies, not only do we need to make a good antenna, but other aspects also need to be improved."

  He is now receiving radio, all of which are long-wave radios with relatively low frequencies. To receive higher frequency bands, such as amateur radio signals, the mineral machine simply cannot meet the requirements and can only be replaced with higher-performance components to receive signals from amateur radio bands.

  But overall, Lin Hong was still quite satisfied. The mineral radio had been successfully made by him, and in the process of making it, some problems he encountered were basically solved by himself, and in the process of solving these problems, he also learned a lot, putting theoretical knowledge from books into practice, which felt very good.

  Next, Lin Hong's plan was to make a better antenna so that he could listen to the radio at home in the evenings. In his reading process, he often came across English words, after all, these technologies were first developed from abroad, whether it was books or magazines, many contents were directly translated, and some basic terms were even written directly in English.

  So, Lin Hong had another plan to learn English by himself. He found that some radio stations would broadcast English teaching programs at night, so he decided that after the crystal radio was made, its important function would be to listen to these English teaching programs. And when it got better in the future and could receive foreign radio stations directly, he would stick to listening to original foreign radio broadcasts.

  At noon when he went back for lunch, Lin Hongshun took the "mining machine" back with him. After finishing his meal, he came back to continue reading books.

  This time he looked at books related to antennas. He checked some information and decided to make a "Yagi antenna" for emergency use first.

  "Yagi antenna", also called "Yagi-Uda antenna", is a directional antenna designed by Japanese antenna experts Yagi Hidetsugu and Uda Shintaro, with the advantages of high gain, strong directivity and simple structure. The materials used in its construction are quite convenient to obtain, which suits Lin Hong's current situation very well.

  All afternoon, Lin Hong was reading a book called "Yagi Antenna Production Tutorial", which detailed the basic principles and production methods of "Yagi antenna".

  Just as he was reading the last part of the book, a loud noise came from outside the courtyard, and it seemed that many people had arrived.

  Lin Hong put the book back in its original place and walked outside to take a look. It turned out that Old Xu had returned, but he wasn't alone - a large group of unfamiliar faces had arrived with him. Lin Hong was certain that these people weren't from Black Rock Village or any nearby villages. Judging by their clothing, they seemed more like city folks.

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