Once We Lived in Nanjing

Spectrum analyzers are not unfamiliar devices. They come in different sizes, with the larger ones as bulky and heavy as the old oscilloscopes in college physics labs, and the smaller ones as portable and handy as a Nintendo handheld console. The function of a spectrum analyzer is to detect radio signals, accurately capturing the invisible and intangible electromagnetic waves in the air and displaying them on an oscilloscope.

A peak appears at the 14MHz mark on the horizontal axis if there's a wave at 14MHz.

A peak appears at the 144MHz mark on the horizontal axis if there's a wave at 144MHz.

The number of peaks corresponds to the number of waves; two waves yield two peaks, and a stronger wave produces a higher peak.

Soon, someone from the committee brought over the spectrum analyzer. There was a "thud thud" knocking at the door, and Wang Ning hurried over to open it. Standing outside was a disheveled young man, drenched in sweat, wearing a blue short-sleeved shirt and black shorts. This was the unlucky guy summoned by his unscrupulous boss to help in the middle of the night, carrying a spectrum analyzer wrapped in wires.

Being a recent graduate and new to the workplace, he hadn't learned how to refuse work that wasn't his responsibility.

If he had the thick skin of Bai Zhen, he would have responded to the call with "Ah, sorry Brother Wang, I'm busy... ah... ah..."

Complete with heavy breathing sounds.

Even the most unscrupulous boss would retreat at this point.

Old Wang might even show some concern, telling the young man to take care of his health and not to get too engrossed in whatever he was busy with.

"Brother Wang, I've brought you the spectrum analyzer," the young man panted, having climbed up eight flights of stairs with such a large device. "It was tough. Is this the one?"

"Oh thank you so much! Yes, yes, that's the one. Zhu, you've been a huge help," Wang Ning quickly took over the spectrum analyzer. "You must be exhausted. Sit down and have some water."

"No need, no need, thanks Brother Wang," Zhu waved his hand. "If there's nothing else, I'll head back first, see you later, Brother Wang."

"See you tomorrow!"

The young man turned and swiftly went downstairs.

Wang Ning placed the white spectrum analyzer on the living room's dining table. The device was even larger than the Icom725 shortwave radio in the room, with a white engineering plastic casing, a built-in handle, and a control panel on the left half with a liquid crystal display, and on the right half, neatly arranged English and number buttons.

"What is this thing?" Mum came out from the kitchen and casually untied her apron. "Did you guys get another radio?"

"Spectrum analyzer," Wang Ning answered. "Agilent. It costs tens of thousands of dollars."

"Did the committee provide this?" Mum asked. "Do you know how to use this thing?"

"I'm an expert," Wang Ning patted his chest. "Do you know when I first used a spectrum analyzer? I first operated one back in..."

"When was that?" Zhao Bowen asked.

"Twenty years ago," Wang Ning said.

"Then you're quite experienced," Zhao Bowen said, "Director Wang."

"Right? Back then I used the old Hewlett-Packard spectrum analyzer to help China Unicom tune pager stations," Wang Ning said. "Testing the phase difference between the two antennas of the pager station, you know? There were phase differences between the two antennas, so we needed to sync them up using this device. That was during the pager era."

"When was the last time you used a spectrum analyzer?" Dad asked.

"The last time was the first time."

"Are you really from the committee? You haven't touched a spectrum analyzer in twenty years?" Dad asked. "Why would the committee employ a good-for-nothing like you? Why should the State feed a parasite like you?"

"Roll on, I only said I've never personally operated it, but what's wrong with directing others to operate it?" Wang Ning said. "Aren't the elderly allowed to slack off a bit?"

He plugged in the power for the spectrum analyzer and turned it on; the LCD screen lit up.

Using a spectrum analyzer is more convenient than a radio transmitter, with one important feature being that it's not picky about the power supply—it can run on a standard 220-volt household AC outlet.

Unlike a radio that can only use direct current, those who play with ham radios also need to have a car battery on hand at home.

The screen shows a grid coordinate system, with the X-axis representing signal frequency and the Y-axis representing radiation intensity. A jagged yellow line fluctuates unevenly across the grid, signifying background noise. Background noise is akin to the rustling sound when a radio receives no signal or the snowy dots on a TV screen without signal. It may originate from humans, nature, or even cosmic microwave background radiation. Apart from the sawtooth-like noise floor, there are also several pronounced peaks.

These peaks are signals captured by the spectrum analyzer. They could be broadcasts, walkie-talkies, or signals from other stations. In modern society, wireless waves permeate everywhere, and in theory, the spectrum analyzer's sweeping capability can search all nearby electromagnetic wave frequencies.

Wang Ning began to set the basic parameters of the spectrum analyzer.

He pressed the "AMPLITUDE" button on the right side of the control panel, which refers to "amplitude," or essentially the signal and radiation intensity, setting the Y-axis parameters.

Wang Ning set the Y-axis unit to dBμV.

Next, he set the X-axis parameters—the spectrum analyzer's monitoring range covers the full band and can pick up a bunch of unwanted chaotic signals. However, Wang Ning needed to monitor the Icom725 operated by Bai Yang, which was tuned to a frequency of 14 megahertz, so Wang Ning needed to narrow the monitoring range.

He pressed the "FREQUENCY CHANNEL" button on the upper left of the button area on the control panel. This term means "channel," and by pressing it, one can set the X-axis parameters, i.e., the spectrum analyzer's frequency monitoring range.

"Xiao Yang—!" Wang Ning asked, "It's 14 megahertz, right?"

"Right!"

Wang Ning narrowed the spectrum analyzer's monitoring range to 5 megahertz to 50 megahertz.

"Xiao Yang! Press the PTT and give it a try!"

Upon hearing this, Bai Yang pressed the handheld microphone.

The Icom725 transceiver on the table transmitted a signal.

Bai Yang didn't speak, so the radio transmitted an unmodulated carrier signal, merely a meaningless electromagnetic radiation.

The response was immediate, and the waveform on the spectrum analyzer in the living room swiftly climbed, forming a small peak right at the 14 megahertz position, undoubtedly the signal from Bai Yang's radio.

"Look, this is Xiao Yang's signal," Wang Ning pointed at the peak on the screen, "Although it's a bit weak, it's quite clear. Around the frequency of 14.255 megahertz, we'll proceed like this. Once Xiao Yang connects with BG4MSR, we'll try to catch the other party's signal. If we can catch it, we're good to go; we have plenty of ways to locate the signal source."

"What if we can't catch it?" Bai Zhen asked, "When you were listening before, you didn't hear that girl's voice, right?"

Wang Ning pondered for a moment.

"It's highly unlikely we won't catch it. A signal that Agilent is able to receive, there's no reason we can't. In case, I mean if by chance we can't—"

"That would imply what?" Bai Zhen asked.

"That would imply the spectrum analyzer is broken," Wang Ning said, "Then we'll have Zhao Bowen come over and switch to another spectrum analyzer."

"What if we still can't receive the signal after switching to a different spectrum analyzer?"

"Then we'll have Zhao Bowen switch to another one again," Wang Ning said.

"And if after changing all the spectrum analyzers we still can't receive the signal?"

"Then we'll switch to another Zhao Bowen."

·

·

·

(Author's idle talk: This book is a theater essay column work, so the length will not exceed five hundred thousand words.

However, I estimate the word count of this book to be around four hundred thousand, which regular readers should already be accustomed to.)