Ban Xia held the small green PCB board in her hands, examining it under the light. It was slightly larger than her thumb, with a thin white wire about ten centimeters long hanging from it. Both ends of the wire were soldered to identical square circuit boards. The board in Ban Xia’s hand had a faded “TX” marked on it, while the one on the other end was marked “RX”. This device was plugged into the repeater, with one end connected to the transmitter and the other to the receiver, linking the two base stations together.
The PCB board was covered with a green solder mask, and beneath the thin protective layer, one could see the methodically arranged traces. This circuit board was small and simple, with neat rows of silver solder pads marked with white English abbreviations.
“Hmm… MIC AUDIO…”
Ban Xia examined carefully.
“PTT.”
“GND.”
“RX AUDIO.”
“COR OUT.”
She didn’t understand what these abbreviations meant, but she could guess they indicated the functions of those pins.
This was the most basic circuit board, so basic it didn’t even have the most fundamental components. It weighed only a few grams in her hand, yet it embodied humanity’s highest wisdom from the Third Industrial Revolution. The concept of integration was born from this tiny plastic piece. PCB boards had replaced complex, bulky physical cables and circuits. People could now print intricate circuits in two dimensions like drawing pictures, laying them flat, miniaturizing designs as complex as cities down to millimeter scale, and building vast information kingdoms.
Before the world’s destruction, just how far had human civilization advanced?
The girl curled her bare toes, rocking her chair with a creaking sound, holding the circuit board high. She squinted one eye, focusing on the small round through-holes on the circuit board. Perhaps she could understand her teacher’s sadness and pain – this magical creation lay before her, yet she couldn’t comprehend it.
This was an ability humans once possessed.
Now lost.
Ban Xia remembered the days when her teacher was still around. She was little then, and her teacher would take her everywhere to scavenge, using the collected scraps to build their fortress piece by piece.
Her teacher was from the old world and knew the pre-apocalyptic world very well. Ban Xia had tried to guess her teacher’s profession, but the latter’s versatile abilities made it impossible to determine what she did before disaster struck. Her teacher was skilled in wilderness survival and an excellent shot – Ban Xia thought she might have been a military personnel. But she also knew how to set up electrical networks and repair complex household appliances, like an electrician. Most surprisingly, her teacher had studied astronomy and aerospace engineering for a very long time (Ban Xia didn’t know what astronomy and aerospace engineering were; these terms came from Bai Yang). Her teacher had collected extensive materials but eventually burned them all.
During those years, her teacher would sit in the room reviewing books and drawing diagrams, telling Ban Xia to go play in the dirt. Occasionally, Ban Xia would sneak into the room and see the walls covered with draft papers.
“Teacher was trying to save the world!” Ban Xia told Bai Yang. “She was looking for a way to drive away this world-ending disaster!”
“But only you two were left in the whole world,” Bai Yang asked. “How could she save it? Could she bring everyone back to life?”
“I don’t know about that, but she must have been looking for a solution,” Ban Xia said. “The teacher was so amazing – she was the only person who survived the disaster! One in several billion – isn’t someone like that destined by heaven to be the world’s savior?”
“There’s also you, young lady. You’re a survivor too.”
“I’m just someone she saved, the kind that holds people back,” Ban Xia said. “Without her, I wouldn’t have survived until now. Without me, she probably would have lived until now.”
“It’s a pity your teacher didn’t leave behind any useful information,” Bai Yang sighed.
“She burned all her materials,” Ban Xia said. “Who could have known this would happen? That I could contact you.”
“If only she had left them for you,” Bai Yang scratched his head. “Then we wouldn’t be so clueless now, not knowing what happened or why.”
“But she didn’t leave them for me. If you had contacted us five or six years earlier, you could have talked to the teacher,” Ban Xia said. “Since we’re crossing time anyway, why couldn’t you push the time back five years? Five years ago, the teacher was still alive. She knew everything.”
“That’s not something I can decide, young lady,” came the leisurely reply from the radio. “We’re already fortunate that heaven granted us this opportunity. How could we be picky? I also wish I could have contacted your teacher.”
“Oh?” The girl raised an eyebrow. “You don’t want to contact me?”
“No… that’s not what I meant,” Bai Yang suddenly stammered. “I meant your teacher would be more useful…”
“I’m not useful?”
“You are useful!” Bai Yang said decisively.
“What use am I?”
“You… you’re humanity’s last hope from ancient times to now, the most important final person in human history, a priceless young lady of incomparable worth, the person with the highest IQ in the world, the best shot, the best archer, the most beautiful, with the best figure!” Bai Yang said in one breath.
Ban Xia’s eyes rolled playfully, her lips curling up slightly into a small arc as she made a soft nasal sound.
“Hmph.”
Thursday.
Wang Ning’s corpulent body was half-hanging out the window, his hands held high gripping two mop handles with two-meter whip antennas attached to them, sweating profusely.
Wearing headphones, he listened carefully for a moment, then shouted toward the residential complex: “I can’t hear anything! Old Bai, have you transmitted yet—?”
“No—!”
Bai Zhen stood far below by the residential area’s lawn, with a folding wooden table set up in front of him. A black digital amateur radio sat on the table. He tilted his head to hold his phone with his neck, one hand gripping a Baofeng UV5R amateur radio transceiver, the other adjusting the digital radio on the table.
“Then hurry the hell up—! I can’t hold this position much longer—!” Wang Ning howled. “My back’s about to break!”
“Okay, okay… right, good, no problem, I’ll give it to you in a minute.”
“Old Bai, have you transmitted yet or not—?”
“No—!”
“Then what the hell are you mumbling about? What are you saying—?”
“Old Zhao’s calling me—!”
“How does he have so much crap to say—!”
“How should I know why he has so much crap to say—!” Bai Zhen first yelled up at the building, then lowered his head back to the phone. “Huh? No, not talking about you, he’s saying his dad talks too much.”
This was their sixth experiment of the day.
The experiment setup was quite extensive, employing the repeater, base station, and spectrum analyzer. Wang Ning and Bai Zhen had preliminarily assembled the remote control system and had been experimenting from nine in the morning until four in the afternoon, continuously adjusting the equipment to achieve optimal performance.
The different pieces of equipment were placed far apart from each other, positioned at locations as distant from each other as possible.
The repeater and second-hand Icom 725 were connected and placed on the desk in Bai Yang’s room – this was because the second-hand Icom 725 shortwave radio needed to use Bai Yang’s DP antenna. The 14MHz dipole antenna was a full twenty meters long, hanging like an enormous clothesline on the roof, impossible to set up temporarily, so they had to use the existing one.
The antennas needed for the repeater were 144MHz whip antennas, two meters in length. In their modification plan, they had abandoned the duplexer, opting instead for the crude but effective solution of using two antennas – one for the transmitter and one for the receiver, each operating independently, both held by Wang Ning outside the window.
To avoid interference, Wang Ning needed to keep the two antennas as far apart as possible, so he currently looked like an Ultraman with both arms raised high outside the window.
To be honest, the pose was a bit alarming as if he might launch into space at any moment.
Meanwhile, Bai Zhen had brought another amateur radio station, an Icom 705 he had borrowed from someone.
Bai Zhen took a folding table downstairs and set it up on the residential area’s lawn, only to be chased away by security.
He moved to a different spot, setting up the table on a small path, placed the Icom 705 amateur digital radio on it, and set up the antenna, only to attract security’s attention again. He spent a long time arguing with the residential security guard.
The new security guard found this middle-aged man suspicious, his equipment suspicious, his credentials suspicious.
Bai Zhen asked, “Don’t you know what HAM is? I’m a HAM.”
The security guard replied, “If you’re a toad, please return to the pond.”
Bai Zhen held the UV5R handheld radio, with the Icom 705 on the table and antenna set up beside him, responsible for testing the remote control system in the command center.
These devices would form the following signal chain:
For receiving tests, Bai Zhen would transmit using the UV5R outside, the signal would be received by the GR3188 repeater, and the repeater’s receiver would transmit the signal to the Icom 725.
For transmission tests, Wang Ning would use the Icom 725 in the room to send signals, the Icom 725 would transmit to the GR3188 repeater, and the repeater’s transmitter would send the signal to Bai Zhen, whose Icom 705 amateur radio would receive it.
If both transmission and reception worked properly, then BG4MSR could replicate an identical system.
Due to severe understaffing, Wang Ning and Bai Zhen had to each do the work of two people. Bai Zhen took the handheld radio downstairs to maintain distance, while Wang Ning wore headphones to monitor signals while supporting the antennas like a human stand.
“Attention, attention, all departments,” Bai Zhen pressed the PTT button on the UV5R. “Reverse the Future Save the World Amateur Radio Emergency Command Center, remote control system sixth experiment, now beginning!”