As for receiving radio, it is much easier. A crystal radio that does not require power can do the job.

It is much more sensitive than the mineral powder detector used by Popov and Marconi, but the manufacturing process is simpler and it is made directly from natural ores. The most preferred one is the pyrite crystal that is abundant on Xishan Island. This metal oxide is a natural semiconductor.

Of course, in the Taoism Research Institute, this beautiful pyrite crystal is called... the sound-transmitting fairy stone.

When using it, a metal probe is used to contact the ore. By adjusting the position of the probe's contact point on the ore, you can find the contact point with semiconductor effect. Using the semiconductor effect of this point, you can pick up radio waves in the air.

In addition to the crystal detector, the antenna, ground wire, coil and capacitor required to manufacture the crystal radio are all technologies that the research team already possesses.

The only problem that needed to be solved was how to observe the received radio signals. The team's initial design used the principle that electricity generates magnetism, which attracts the tiny metal needle to swing, and the receiver recorded the telegram by observing the swing of the needle.

But in the experiment, it was found that it was not easy to ensure the accuracy of the recording, and it could not be used on a bumpy ship. Wang Zheng made a simple electric bell to solve the problem.

When the signal is received, the electromagnet becomes magnetic and attracts a piece of iron. After disconnection, the iron piece rebounds by its own power and hits a bell, thus converting the electrical signal into an acoustic signal.

Now, the receiver improved by Wang Zheng can not only ring the doorbell, but also record different telegraph code signals on paper tape, greatly improving the accuracy of reception.

~~

"The 762nd experiment of Thousand Mile Sound Transmission begins!" Zhang Jian announced loudly in the laboratory.

When Zhao Hao solemnly pressed the key, he saw continuous blue sparks between the two balls in the spark gap, making him think he was cooking with an electronic ignition stove.

At the same time, the armature of the boost inductor vibrates like an electric bell, producing a transmitting side tone - the beeping sound heard when sending and receiving telegrams. This is to allow the sender to hear the sound of his own transmission at the same time.

Then, a clear electric bell rang in the backyard. It was the receiver that received the signal!

"It really worked!" Soon, Zhao Shizhen, who was guarding the receiver in the backyard, rushed in excitedly and shouted, "Suddenly the doorbell rang, and it scared me!"

"Yes, this is just a small step, but a big step for mankind!" Zhao Hao nodded with a smile and gave several talented disciples a loving hug.

However, it is not time to celebrate yet, because this only verifies the feasibility of short-distance radio transmission and reception, and it is still unknown how effective long-distance transmission and reception will be.

A radio that can only send and receive at short distances is still a scientific toy with no practical application. Only when it has the ability to send and receive at long distances can the radio really play a role!

Then everyone split into two groups, and Xu Guangqi stayed in the Taoist temple to be in charge of sending and receiving.

Zhao Hao, Zhang Jian, Wang Zheng and their party left the Taoist temple with a transmitter and a receiver to test the current communication limits.

Zhao Hao set the first field test one kilometer away from the Taoist temple.

After the guards completed the anti-peeping alert, Wang Zheng led the researchers to open two wooden boxes, one large and one small, and began to assemble them carefully.

The big wooden box contained Xu Guangqi's telegraph machine. Because of the Leyden jar and canned batteries, it was a little difficult to assemble. It took almost a meal to install and debug it. Then a telegram was sent to the Taoist temple. The content was something Zhao Hao asked Zhao Shizhen to come up with on the spur of the moment:

'See the simplicity and embrace the simplicity'.

Two minutes later, the transmitter that had been installed a long time ago suddenly rang a clear bell, and at the same time, the paper tape began to record the transmitted signal.

'—·—·—', the first signal received was this one. In the code compiled by Zhao Hao, this meant the start of transmission.

Then there is another series of signals, which translate into a series of four-digit numbers, such as '1223', '2234', '8961' and so on.

The last signal is '・・・—・' which indicates the end of the transmission.

This Zhao Hao code, which was later shortened to "Zhao Code", was basically derived from Morse Code. However, Morse Code used different electrical signals to form numbers and 26 letters, as well as several punctuation marks. However, "Zhao Code" only needed to use electrical signals to represent ten numbers.

He also ordered people to collect and organize 7,000 Chinese characters, add various numbers, punctuation marks, and phonetic symbols, and compile them into a "Code Book".

Then each character was numbered using scientific numbers, resulting in more than 7,000 different four-digit numbers.

This "four-code method" is the simplest code, which does not require any skills, but relies purely on brute force. But because of this, as long as the sender changes the coding sequence regularly, the opponent will not be able to crack the code even if it intercepts it.

Therefore, the receiver only needs to check the received four-digit number with the code book to translate the message from the Taoist temple:

'Little, private, few, desires'!

It is exactly the next sentence of 'see the simplicity and embrace the simplicity'.

"My uncle is so awesome!" Zhao Shizhen was shocked again.

Zhang Jian, Wang Zheng and others had calm expressions.

"It seems like you all have a plan in mind." Zhao Hao smiled faintly and said, "Have you conducted this experiment many times before?"

"When reporting the results to Master, we have to make sure everything is foolproof." Zhang Jian said with a sheepish smile.

"How far is the farthest distance?" Zhao Hao didn't care about it. If he was so pretentious, wouldn't he be angry all day long?

"Without the master's order, I didn't dare to leave the island." Zhang Jian said hurriedly: "I just tried it on the island."

"Six kilometers?"

"almost."

"Then let's not waste time." Zhao Hao patted Wang Zheng on the shoulder and said, "Leave the island and get on the boat!"

~~

After packing up their belongings, the group got on the car and left the research center. They then went to the pier of the Summer Resort to transfer to Zhao Hao's Science.

The 'Science' that Uncle Wu gave to Zhao Hao had been retired long ago. This one was a new generation 'Science' carefully built for Zhao Hao by Jiangnan Shipyard.

The beautiful streamlined hull painted pure white is the most beautiful ship wherever it sails. The interior decoration of the hull is even more exquisite, the wood used is the finest teak, the hardware and outfitting parts are all gold-plated brass and silver products, and various special shock-proof and seawater-resistant glass. The value of the interior decoration alone is three times higher than that of the hull.

Not to mention the full set of the most advanced and top-level living enjoyment.

However, Mr. Zhao did not want to get on his elastic rosewood bed now. He only wanted to shoot the radio.

The second long-distance test was conducted in the waters near Sanshan Island, 13 kilometers away from the Taoist temple.

This time, Zhang Jian's uncle and nephew finally became nervous, but the result was very gratifying. They didn't even need to set up a special antenna. They could receive the signal just by using a piece of wire on the receiver.

"Great!" Wang Zheng cheered and jumped up on the deck.

Zhao Hao sat on the sofa and asked, saying that he was calm. He was not surprised, because this was an era without electricity. The frequency spectrum was very clean, with almost no interference, so the receiver could easily capture the wireless signal.

"It would probably only take a few watts of radio frequency power to reach all over the world," he thought happily.

Next, the third test was successful at Guajingkou, 30 kilometers away.

The fourth test was carried out in Luzhi, 50 kilometers away, and was also successful.

That concludes the testing for the day.

The next day, the signal began to weaken when it reached Shanghai County, 100 kilometers away. But after attaching an antenna, the signal immediately recovered. When it reached the Jiangnan Shipyard, 150 kilometers away, it was still able to communicate successfully.

"Master, are we going to continue the test?" Zhang Jian asked when he saw that they were about to go out to sea.

"Go on, this is just the beginning?" Zhao Hao said excitedly.

Although the typhoon season has not yet passed, the group has established a comprehensive early warning system. The farthest weather station has been built in Mindanao, so it can closely monitor the typhoon from its source.

With the multiple warnings, the damage caused by typhoons in Luzon and Taiwan each year has been greatly reduced. The northern side has more time to react, and now the Royal Marine and Coast Guard fleets only need to enter the port to avoid the typhoon before it arrives, so the so-called typhoon season has little impact on them.

So the group decided to go out to sea. Although the Science was also capable of sea voyage, for safety reasons, the group switched to Zhao Hao's "Jiangnan".

This giant ship with a displacement of 1,300 tons was built entirely according to battleship standards. Its hull number was 00 and it was Zhao Hao's special ship for ocean voyages.

In the past few years, Zhao Hao has frequently patrolled various overseas administrative regions. If he randomly finds a flagship as his seat and lets the main fleet of the garrison area escort him, it will obviously affect the normal operation of the garrison area and increase security risks.

Therefore, after the group had sufficient ships, the General Staff suggested forming a special guards fleet to solve this problem.

After the proposal was passed, the Guards Fleet consisting of two cruisers, three destroyers, three frigates, and three clippers was established the year before last.

The officers and soldiers of the Guards Fleet are all politically strong, loyal and reliable veterans selected from various war zones and garrison areas. Fleet Commander Mei Ling and Police Commissioner Kang Jia both hold the rank of junior police inspector.

Although the Guards Fleet is under the General Headquarters, it is under the leadership of the Security Department, that is, Gao Wu.

After more than a decade, Gao Wu's title was still the head of the security department, but his team had expanded to more than 30,000 people... and even had a fleet.

Moreover, once the radio station is officially put into use, a special communications department will be set up. It will be deployed in all domestic, overseas administrative regions, and war zones, and security and confidentiality work must be done well. It is impossible to do it without 10,000 people.

A section chief under him can make Zhao Hao's civil and military officials tremble in fear. Hey, what's that man's name?

Oh, I can't remember. Never mind.

So the title of the position is not important. What is important is the distance from the top leader and the amount of actual power.

P.S. Actually, writing about how to make a transmitter is the most exhausting. I was so tired of searching for information and it took so much time. I know many readers don't like to read it, but I have to write about it because it is the last and most important invention in the book. If I can't figure it out, I can't write about it later. If I don't write about it in detail, people will think that I am using cheat codes just to finish the book. Anyway, I'll write it to make the story more solid.

I promise that this is the last time I will write a scientific article in my writing career. There will never be another one.