The handheld walkie-talkie Li Yu brought to Luye before has a transmitting power of 5 watts. The effective communication distance of this walkie-talkie in urban areas is about 1 to 3 kilometers, and in the wild it can reach 3 to 5 kilometers.
In Green Field, this number can be doubled again. This is because compared to another cosmic plane, Bratis Continent has a better electromagnetic environment.
Except for some electronic equipment brought by Li Yu and Xiaowa, there is almost no environmental noise here, but even so, China Unicom can only be connected within 15 kilometers at most.
After Clara was kidnapped, Li Yu sent a team of black dog guards headed by Tom to find her. However, after Tom left the green field, the two parties could only rely on traditional manpower or carrier pigeons to communicate messages.
As a result, there is considerable lag, and there is also the risk of being intercepted halfway.
In addition, once Tom starts moving and changes his mailing address, Li Yu will no longer be able to keep in touch with him until the next time he sends a letter.
So Li Yu began to consider establishing a longer distance communication method.
The most intuitive way is of course to increase the transmit power.
For example, if the transmission power is increased from 5 watts to 50 watts, the effective communication distance can be increased by almost five times.
[To be honest, I have been using Yeguoyuedu recently to read and catch up on new books. I can switch sources and read aloud with many sounds. www.yeguoyuedu.com is available for Android and Apple.]
But even so, the longest communication distance is still only 75 kilometers.
In addition, another common approach is to add repeaters.
The function of a repeater is to relay and amplify signals.
This is a bit like a relay race. When you are about to run out of energy, you can hand the baton to a taller and faster person and ask him to help you continue running, so that you can run farther.
However, unless an IP repeater is used to directly connect to the IP network, the communication distance that can be increased by setting up a repeater is still very limited.
In addition, the biggest problem with this method is that the repeater must be set up outside the green field, which will inevitably require additional manpower and energy to maintain the equipment.
Since these two methods are unsatisfactory, are there any other solutions that can meet Li Yu's current needs?
The answer is yes.
That's shortwave radio.
In the movie "The Eternal Wave", the protagonist Li Xia uses a shortwave radio station, which can send telegrams from Shanghai to Yan'an.
This is because shortwave propagates not only through ground waves, but also through sky waves.
The signal can be emitted to the sky through the antenna, reflected back to the ground through the ionosphere, and then reflected from the ground to the sky. After multiple reflections, a ground wave signal that can only travel dozens of kilometers can be propagated to hundreds or even tens of thousands of kilometers away.
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In the early spy wars, most of the shortwave radio stations equipped by intelligence personnel used CW communications and relied on Morse code to transmit intelligence.
Until now, many amateur radio enthusiasts are still obsessed with using this method to transmit information, and they have even been able to reach the world with one watt.
However, Morse code needs to be learned, and the corresponding English letters are more expensive for people on the Bratis continent to learn.
Fortunately, times are developing. In addition to CW, there is also SSB mode, which can directly transmit voice.
Li Yu purchased three Yaesu shortwave radio stations, and then joined a WeChat group full of amateur radio enthusiasts on the recommendation of his boss.
It took about three days to learn the basic usage of the radio with the help of the elders in the group, and then taught Radioo in Green Field.
This resulted in the birth of the first half-baked radio operator on the continent of Bratis.
It's not that Li Yu doesn't want to train Radio to be more professional, it's mainly because he himself is only half a bucket of water.
Fortunately, his opponent was still at least a few hundred years away from understanding this technology. Thinking of this, Li Yu felt much better.
Looking at Redio, there is no such problem at all. Although this kid is better than him, he doesn't know it. After Li Yu taught him for two days, he already looked like Wang Chongyang coming out of seclusion.
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And there is reason for Radiodio's pride. In terms of radio technology, he is indeed the second in the world in this aspect, second only to Li Yu, who is the first in the world.
Even Li Yu couldn't refute this point.
What's more, the Rdio was still intact during the first actual battle. Hearing the call to prayer coming from the radio, Alvo ran outside the house immediately and found Li Yu who was doing maintenance on the tractor in the yard.
Li Yu put down the remaining half bottle of lubricant, wiped his hands, and walked into the house.
"Ah, is it Radio, can you copy it?"
"I am Redio, Lord Prophet. I can copy, I can copy." Redio's voice was trembling with excitement.
Li Yu was also in a good mood, because Radioou's voice sounded very clear, without the clutter interference that the elders in the group complained about.
"You should have arrived at Duolin City by now." Li Yu continued.
"That's right, we are outside the Scaled City now, Lord Prophet." Redio said respectfully.
"Very good, hurry up and enter the city. According to the news from Yanxue City, High Priest Martina and her skitarii should be arriving in a few days."
"Actually, this is why I called you. Regarding entering the city, we have encountered some trouble. In order to prevent the spies of the Skitarii from sneaking into the city to cause trouble, Scaled City no longer allows free entry and exit."
Redio said, "Now only those who hold the pass issued by the Layinmondi family or the Silver Moon Church can pass through the city gate."
"Ha, I thought it was a big deal, this is simple."
The person speaking this time was not Li Yu, but another voice.
Li Yu brought a total of three radio stations this time, one was installed in his residence, one was given to Radioo, and the remaining one was placed in Teacup Castle by Li Yu.
Mainly to facilitate Miss Rabbit to contact him if there is any emergency.
As a result, Li Yu regretted it as soon as the fight was over, because Yin Leya ignored the "urgent matter" qualifier he said.
After getting a new toy, I like to call him on the radio when I have nothing to do.
"Merlin Merlin are you there?"
"Um?"
"I saw a purple sparrow when I went out today. It was so beautiful. I don't know if I can see it again tomorrow."
"…………"
Or "Merlin, Merlin, are you there? The carrot stewed pork I had for lunch, what did you eat?"
There are also statements such as "My ancient spirit has reached level 95, it's awesome!"
Li Yu had no choice but to temporarily shut down the radio station there.
But he obviously underestimated the female lord. The latter didn't know whether it was because she played with electronic pet eggs too much, and now she was able to switch them on and off by analogy.
After Li Yu turned off the radio station, the female lord was able to turn it on secretly.
Moreover, these three radio stations use the same frequency, so the female lord should have heard their conversation just now.