That weekend, Bai Zhen and Wang Ning began designing a remote communication system.
Simply put, they wanted to give BG4MSR a mobile phone.
This was important.
Mobile phones offered far greater immediacy and convenience than landlines—it was time to upgrade that girl’s communication method.
“The technical logic is very clear, it’s not difficult to achieve,” Wang Ning sat on the sofa, rubbing his stubbly chin. “Fundamentally, we just need to make a…”
“Repeater,” Bai Zhen sat across from him.
“Yes, we just need one repeater,” Wang Ning nodded.
A repeater was an extremely common and essential infrastructure in amateur radio.
As everyone knew, these days more people played with UV bands than shortwave. For UV bands, you just needed to spend a hundred yuan on Taobao or JD to buy a handheld radio—not much bigger than a phone, compact and portable, with a built-in flashlight that could blind your dog with two presses of a button, unlike shortwave that needed heavy, clunky base stations. But UV bands had pros and cons—UHF and VHF frequencies were much higher than shortwave. Anyone who’d studied high school physics knew that higher frequency meant shorter wavelength; shorter wavelength meant weaker ability to bend around obstacles.
So UV band radio waves propagated line-of-sight—they could only reach places your eyes could see. If there were obstacles in between, the signal would be blocked.
They couldn’t reflect off the ionosphere like shortwave.
But modern cities were full of tall buildings, structures stacked layer upon layer, obstacles everywhere. How could UV band users communicate over long distances?
So people figured—why not put a repeater up high?
This repeater system could be placed on high towers, mountaintops, and even satellites—it needed to be set somewhere high that everyone could see. HAM operators’ UV band handhelds would first send signals to the repeater, which would then relay them onward.
The repeater stood high and saw far, able to transmit signals to distant places. Amateur satellites or the International Space Station in orbits hundreds of kilometers high could even support intercontinental communication.
Such a repeater system was called a relay station.
“A repeater?” Bai Yang was confused, not understanding how to use a repeater for remote control. “How do we do it?”
“Xiao Yang, if you were designing it, how would you let BG4MSR use the IC-725 to contact us from a distance?” Wang Ning asked him back.
Bai Yang paused, thinking for a few seconds.
“Uh… we should establish a radio communication link, letting the young la… BG4MSR transmits signals long-distance to the IC-725, then have the 725 transmit to us.”
“Right, that’s the correct approach,” Wang Ning approved. “But how specifically would we do it?”
“She should have a portable handheld radio as an information transceiver terminal,” Bai Yang thought further. “She uses the handheld to send signals to the IC-725, then the IC-725…”
Here Bai Yang suddenly got stuck.
“Relay.”
He realized that at this point, the 725’s role in the entire link was to relay—the girl’s handheld would transmit signals to the 725, and the 725 would relay signals to Bai Yang.
How could they make the 725 become a relay node?
An old antique like the IC-725 required all functions to be purely manual—you had to physically hold down the microphone button to transmit, and release it to receive. How could this pressing and releasing be controlled remotely?
You weren’t a robot who could run thousands of miles away while leaving one hand in the room just to press buttons.
“The 725 can’t do it alone,” Bai Yang said slowly. “We need a peripheral device that can both transmit and receive radio waves itself and control the 725’s transmission and reception. When information needs to be sent out, it controls the 725 to enter transmit mode; when information needs to be received, it controls the 725 to enter receive mode.”
“You’ve got insight, good insight, Xiao Yang!” Wang Ning smiled. “Just like you thought, we need exactly such a peripheral device.”
“This peripheral is the repeater,” his dad said.
“Exactly, it’s the repeater,” Wang Ning nodded. “Xiao Yang, do you know the structure and working principles of a repeater station? Those pure analog repeater stations… we’d better use pure analog repeaters. Digital or digital-analog hybrids are a bit complex—we’re worried the girl over there won’t be able to handle it, and we’re also worried too precise equipment won’t last long enough. An analog repeater’s structure is so simple you could DIY one yourself with two walkie-talkies.”
“Because a repeater’s basic structure is just two amateur radio stations connected back-to-back,” Old Bai continued, explaining to Bai Yang. “A repeater’s main components are just two base stations plus a duplexer—if you use two separate antennas you can even skip the duplexer. Its operation is very simple: two base stations, one for receiving signals, one for transmitting signals…”
Old Bai pointed at his son.
“For example, you’re a handheld radio, I’m a repeater. When you talk to me, that’s like sending me a signal. My ears are the receiver, my mouth is the transmitter—I’m made up of these two stations. When my ears hear what you say, I use my mouth to relay your words to Old Wang. And when Old Wang talks to me, I can also relay his words to you. Understand?”
Bai Yang nodded thoughtfully.
“I can understand that, but how can it do remote control?”
“The key is here—didn’t you just say we need a peripheral device that can automatically control the 725’s transmission and reception?” Wang Ning said. “As it happens, repeater stations run automatically—they usually operate unmanned.”
“Some repeater stations are set up on mountaintops, some on high towers, some on satellites,” Bai Zhen said. “So most repeater stations work without human operation.”
“This means it has an automatic mechanism for switching between transmit and receive,” Wang Ning picked up an oil marker from the sofa and propped up a small whiteboard on his thigh. “What we need is this mechanism, to use instead of manually operating the 725’s transmit button. Look here, Xiao Yang.”
As he spoke, he drew a rectangular frame on the whiteboard, then drew two flat rectangles inside it, one above and one below.
He wrote “receiver” in the upper rectangle and “transmitter” in the lower one.
Finally, he connected the two rectangles with an arc.
“This is a repeater.”
Wang Ning pointed at the large rectangle with his marker.
“It’s made up of two radio stations.”
Wang Ning pointed at the two small rectangles inside.
“Normally, once the receiver on top receives a signal, it triggers the transmitter below to turn on, which then relays the signal out. But if we take this repeater apart and connect the receiver and transmitter separately to the 725…”
Wang Ning drew another frame next to the repeater.
Then labeled it 725 inside.
He erased the arc, breaking the connection between the two small boxes in the repeater, and connected them separately to the 725 with straight lines.
“Then at this point, when the receiver on top receives a signal, what it triggers won’t be the transmitter anymore, but the 725—understand? The communication link will be like this: BG4MSR uses her handheld to send signals to the receiver, the receiver controls the 725 to enter transmit mode, and the 725 sends the signal through spacetime to our side.”
“What about when we send signals to her?” Bai Yang asked.
“That’s just the reverse of this process!” Wang Ning answered. “We send signals through spacetime to her 725, the 725 receives the signal, triggers the transmitter below to start, and the transmitter sends the signal to BG4MSR’s handheld.”
Finally, he made a grand sweep with his marker, drawing a large circle encompassing everything.
“That’s the basic logic of the entire link!”
Bai Yang stared at the diagram on the whiteboard for a long time. When he looked back at Wang Ning’s balding head, the latter’s forehead seemed to be glowing with the light of wisdom.
“That’s amazing.”
“In this process, the 725’s role is no longer just a radio station,” his dad spoke up. “But a spacetime antenna.”
The technical logic was now sorted out.
Next, they needed to make a plan.
“First, we need to determine the plan’s objectives, and establish what effects we want to achieve,” Wang Ning picked up the oil marker from the sofa and flipped the whiteboard over. He looked up at Old Bai. “The first point is remote control, right?”
“Right, remote control,” Bai Zhen nodded. “We want MSR to be able to communicate normally with this side even when she’s not in front of the 725, not sitting in the chair, but in the next room, outside the house, or even several or dozens of kilometers away—that’s the effect we want to achieve.”
“What are the specific operational requirements?”
“It should ideally achieve the same effect as using a normal handheld radio,” Bai Zhen answered. “She holds the handheld, presses PTT, and can talk.”
“Good, so the requirements are… First, separate person and radio, remote control. Second, simple operation, easy to learn.” Wang Ning nodded, writing them down one by one on the whiteboard.
“There’s… there’s one more,” Bai Yang raised his hand.
“Go ahead, Xiao Yang.”
“Can’t damage or destroy the radio itself,” Bai Yang reminded them.
This point was very important—whatever his dad and Uncle Wang wanted to do, they couldn’t affect the IC-725 radio itself. They still didn’t understand why this radio had the ability for spacetime communication. To everyone, that old IC-725 was a black box, and in this situation, not touching it was the wisest choice.
Previously, Bai Zhen, Wang Ning, and Zhao Bowen had recklessly taken the machine apart once, opening the radio’s case, but fortunately hadn’t caused any effects.
“Good… Third, can’t affect the radio’s normal operation,” Wang Ning wrote it.
Finally, he held up the whiteboard so everyone could see.
The writing was messy but eye-catching.
First, separate person and radio, remote control!
Second, simple operation, is easy to learn!
Third, can’t affect the radio’s normal operation!
These three points would be the framework they must follow as they proceed with the plan. They would strive toward these goals with all their might, upgrading BG4MSR’s communication tools. When the expert team of the Amateur Radio Emergency Command Center for Reversing the Future and Saving the World was operating at full power, the wisdom of the uncles would be unstoppable!