The handheld walkie-talkie that Li Yu brought to Lvye before has a transmission power of 5 watts, and the effective communication distance of this walkie-talkie in urban areas is about 1 to 3 kilometers, and it can reach 3 to 5 kilometers in the field.

In Greenfield, this number can be doubled again, because compared to another cosmic plane, the Brattis continent has a better electromagnetic environment.

Except for some electronic devices brought by Li Yu and Xiaowa, there is almost no ambient noise here, but even so, it can be connected within 15 kilometers at most.

After Clara was kidnapped, in order to find her, Li Yu sent a team of Black Dog Guards led by Tom, but after Tom left the green field, the two sides could only rely on traditional manpower or carrier pigeons.

In this way, there is a considerable lag, not to mention, there is also a risk of being intercepted halfway.

In addition, once Tom started to move, he changed his mailing address, and Li Yu could no longer keep in touch with him until his next delivery.

So Li Yu began to think about establishing a longer distance communication method.

The most intuitive way to do this, of course, is to increase the transmit power.

For example, if the transmit power is increased from 5 watts to 50 watts, the effective communication distance can also be increased by almost five times.

But even so, the maximum communication distance is still only 75 kilometers.

In addition to this, it is also common to add repeaters.

The role of the repeater is to relay and amplify the signal.

It's a bit like a relay race, where when you run out of energy, you can give the baton to a taller and faster person and ask them to help you keep running, so you can run farther.

However, unless an IP repeater is used to connect directly to the IP network, the communication distance that can be increased even by setting up a repeater is still very limited.

In addition, the biggest problem with this method is that the repeater station is set up outside of the green field, which inevitably requires additional manpower and energy to maintain the equipment.

Since neither approach is satisfactory, is there any other solution 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 the propagation path of short waves is not only ground waves, but also sky waves.

The signal can be transmitted to the sky through the antenna, reflected back to the ground through the ionosphere, and then reflected to the sky from the ground.

In the early days of espionage warfare, most of the shortwave radios staffed by intelligence personnel used CW communications, relying on Morse code to transmit intelligence.

Until now, there are still many amateur radio enthusiasts who are obsessed with using this method to transmit information, and even have been able to reach 1 watt around the world.

However, Morse code needs to be learned, and the corresponding English alphabet is more expensive for people on the continent of Brattis to learn.

Fortunately, the times are developing, and in addition to CW, there is now an SSB mode that can transmit voice directly.

Li Yu bought three Yaesu shortwave radios, and then joined a WeChat group full of amateur radio enthusiasts on the recommendation of his boss.

With the help of the group bosses, it took about three days to learn the basic usage of the radio station, and then taught ROE Visual in Greenfield.

As a result, the first half-hung radio operator was born on the continent of Brattis.

It's not that Li Yu doesn't want to train Reio to be more professional, but the main thing is that he himself is half a bucket of water.

Fortunately, the opponent is at least a few hundred years away from understanding this technology, and thinking about it like this, Li Yu feels much better.

Looking at Reio again, there is no trouble in this regard at all, although this kid is better than him, but he doesn't know it, Li Yu taught him for two days, and he already has the posture of Wang Chongyang out of the customs.

And there is a reason for Roe Visual to be proud, in terms of radio technology, he is indeed the second in the world in this plane, second only to Li Yu and the first in the world.

Even Li Yu can't refute this.

What's more, the first actual combat Reodio did not drop the chain, hearing the prayer sound on the radio, Alvo ran outside the house as soon as possible and found Li Yu who was doing maintenance for the tractor in the yard.

Li Yu put down the remaining half bottle of lube, wiped his hands, and walked into the house.

"Ah, is it Reo, can you copy it?"

"I'm Roe Visual, Lord Prophet, and I can copy it, I can copy it." Redeo's voice trembled with excitement.

Li Yu was also in a good mood, because Redion's voice sounded clear, and there was no clutter interference that the group bosses complained about.

"You should have arrived in Scaly City by now." Li Yu continued.

"That's right, we're just outside of Scales now, Lord Prophet." Roe Visual said respectfully.

"Very good, hurry up and enter the city, according to the news from Rock Snow City, in a few days, High Priest Martina and her cathars should also arrive."

"Actually, that's why I'm calling you, we're in a bit of trouble about going into town. In order to prevent Cathar spies from infiltrating the city and causing trouble, Multiscale City is no longer allowed to enter and exit freely. ”

"Nowadays, only those with a pass issued by the House of Raimundi or the Silvermoon Church are allowed to pass through the gates. ”

"Ha, I thought it was a big deal, this is simple."

This time the person who spoke was not Li Yu, but another voice.

Li Yu brought a total of three radio stations this time, one was set up in his residence, one was handed over to ROE Visual and one left, and Li Yu put it in the teacup castle.

The main thing is to make it easier for Miss Rabbit to contact him if she has any urgent matters.

As a result, Li Yu regretted it as soon as he got it, because Ilea ignored the constraints of what he said was "urgent".

After having a new toy, I love to call him on the radio when I have nothing to do.

"Is Merlin here?"

"Huh?"

"I went out today and saw a purple sparrow, it's so beautiful, I don't know if I'll see it tomorrow."

“…………”

Or, "Merlin Merlin, are you there, my carrot stew at noon, what do you eat?" ”

And "My Ancient Spirit has reached level 95, awesome!" and so on.

As a last resort, Li Yu could only temporarily shut down the radio station over there.

But he obviously underestimated the female lord, and the latter didn't know if it was because the electronic pet eggs were too much to play, and now that the touch was bypassed, they would actually turn on and off.

After Li Yu turned off the radio, the female lord could still secretly turn it on.

Moreover, the three radio stations were using the same frequency, so the female lord's side should have heard their conversation just now.

I couldn't help but interject.

(End of chapter)