Once We Lived in Nanjing

The next part is the other half.

The other half starts from the back of the radio.

There are two ports on its backside.

"Two sockets! ACC1 and ACC2!"

"Right, turning around they have two sockets, I've told you about this before, we need to use the ACC1 port! Pay attention to that metal nameplate on the back of the radio, it's marked which one is ACC1."

"Right side."

"Correct, the one on the right."

"This is a multi-hole port, this socket has lots of holes... one two three four five six seven eight... eight small holes!"

In order to understand the functions and roles of these eight small holes, Bai Zhen and Wang Ning searched the entire internet again, and it was quite hard to find detailed information on this antique Icom725.

The Icom725 radio has several ports on the back, the most eye-catching being the two centrally located circular ACC ports; these are multi-hole sockets, each with eight spindle-shaped small holes, spread out like a blooming chrysanthemum. They are the opposite of the hand mic socket, where the mic socket contains pins for inputting information, while the ACC sockets contain holes for outputting data, and the holes are easier to deal with, you can just stick thin copper wires into them.

But how to stick it in and which holes to use is the key.

"Um... the SQL OUT of the radio is connected to the PTT of the relay station's transmitter."

"EX SPEAKER is connected to the transmitter's MIC."

"And lastly, GND."

Ban Xia still remembered the advice from BG4MXH.

She then pulled out another slender white wire and straightened it—this kind of connection wire with PCB boards on both ends was only available one per relay station, it's used to connect the transmitter and the receiver.

And the connection wire of the GR3188 relay itself had just been cut by Ban Xia.

That wire was currently plugged into the receiver on one end and into the hand mic socket of the Icom725 on the other.

So, Ban Xia found another same type of connection wire from other relays, and just as decisively cut off one end, revealing three thin red, yellow, and black wires from under the white plastic.

Each of the three thin wires was soldered to a long copper wire.

"Which holes is SQL OUT?"

"Hole 6."

She carefully inserted three copper wires into the backside of the radio.

Now the white connection wire is plugged into the backside of the radio on one end and into the relay's transmitter on the other.

With this, the radio centipede was successfully assembled.

This setup had already been successfully tested nine times yesterday by Wang Ning, Bai Zhen, and the others.

But it's not over yet.

There's another vital component—the antenna.

Regarding the antenna, Wang Ning and Bai Zhen thought long and hard. Frankly, these days, antennas are basically bought, with manufacturers setting the parameters for you, you just install and use.

But in Ban Xia's era, there's no Taobao or JD.com, online shopping is impossible, and the simplest way to get an antenna is to make it yourself.

However, it had been many years since Wang Ning and Bai Zhen, the two old fellows, had made their own antennas. It's not that they lacked the ability, but why bother when there were ready-made ones? Why not be lazy? So they put their swords away and let their horses roam the mountains.

"How do we deal with the antenna? Make it ourselves?" Wang Ning asked.

"Make it ourselves, what else can we do?" Bai Zhen said, "Let's try making one ourselves first to see how it works. If it's good, then we'll teach her."

"What about impedance and standing wave ratio?" Wang Ning asked, "She probably can't measure it."

"Make do with what we have, something close enough should work, it's all roughly the same," Bai Zhen shook his head, "With the electromagnetic environment of her era, anywhere she farts the whole world could hear it."

Theoretically speaking, all conductors can be antennas.

It's just that the effectiveness varies.

So if you want to make antennas you can source materials from anywhere, be it clothes hangers, Jingu Bang, Qiankun Ring, Tightening Spell, purple gold begging bowl, nine-toothed nail rakes, Fangtian halberds, Green Dragon Crescent Blades, as long as you can get your hands on them, there's nothing that can't be made into an antenna.

Wang Ning and Bai Zhen chose to use coaxial cable.

"Coaxial cable! Use coaxial cables, really easy to deal with, there's plenty of them around in the city, TV cables, network cables are all fine."

"Find a 75-7 if possible, a 75-5 will do too!"

Coaxial cable, easier to find than the Green Dragon Crescent Blade and more effective, is often used as a feed line for antennas, and can actually be used as an antenna itself. The structure of a coaxial cable is simple; it has two layers: a metallic core in the center, and outside the core, a dense metallic mesh shielding. Between the core wire and the shielding mesh is an insulating material, and the outermost layer is a rubber sheath.

So the cross-section of a coaxial cable looks like a shooting target, with a solid circle in the center and rings around it.

To turn a coaxial cable into an antenna, the most important step is to remove the metallic shielding.

The shielding acts like a Faraday cage. The reason a coaxial cable has stronger anti-interference capabilities than regular twisted pair cables is because of this mesh shield. It can isolate external interferences and prevent electromagnetic waves generated inside the cable from diffusing outward. So by removing this layer, the radio waves can spread out.

"144MHz, how long should it be kept?" Wang Ning asked.

Bai Zhen eyed the pile of black cables on the floor, pondered for a few seconds, and rapidly did the mental calculations.

"About 0.5 meters."

They measured out 0.5 meters from the end of the coaxial cable with a ruler and made a circular cut with a knife at that point.

This was a grand circumcision surgery for sheaths, with the sheath itself being half a meter long.

They peeled off the 0.5-meter long slender sheath to reveal the inner silver metallic shielding mesh.

Wang Ning and Bai Zhen crouched on the floor, rubbing the metallic shielding mesh with their hands, skilled in their movements, loosening the soft metal threads that made up the mesh and then gradually pulling it back, flipping it like rolling up a sleeve onto the rubber outer sheath of the coaxial cable.

After that, a rudimentary 144MHz antenna was essentially finished.

This coaxial cable served both as feed line and antenna; the stripped part acted as the antenna for radiating waves, while the unstripped part was the feed line for signal transmission.

Just that simple.

Finally, Wang Ning fine-tuned it with an SWR meter.

The two conducted nine experiments with this antenna setup yesterday. The flimsy coaxial cable couldn't stand upright on its own, so Wang Ning tied it to a wooden mop handle, holding the mops high and sticking out of the window, seemingly ready to take off and fly, frightening the passing homeowners in the neighborhood into calling the police.

In 2019's Nanjing City, in the Meihua Villa complex filled with power switches and electric bikes, these two seemingly simple whip antennas still tenaciously supported the banter between Wang Ning and Bai Zhen.

"Old Bai, have you got it ready yet? My back's breaking. I'm telling you, you're compensating me for medical expenses, not a penny less than five hundred."

"Fly down here and I'll give it to you, guaranteed to burn it for you, not a penny less."

"Go to hell, if you dare, come up here. Try it."

"If you dare, come down!"

"Come up here!"

"Come down!"

Ban Xia attached the finished coaxial cable antenna to a stick, and BG4MXH specifically reminded her to use an insulator.

There were two antennas in total, one for the transmitter and one for the receiver. The girl exerted a lot of effort to stretch them out from the attic skylight, standing them up on the roof.

144MHz is in the UV range, more precisely the VHF range, and electromagnetic waves travel within the line of sight, so the higher the antenna is placed, the better.

Ban Xia asked how far it could reach?

Wang Ning shrugged; he couldn't be sure either.

UV waves are conventionally used for short-distance communication, but there are always exceptions to everything. Given the right conditions, UV range can achieve direct-frequency communication over several hundred kilometers.

Bai Zhen said that in the apocalyptic era's Nanjing, devoid of people, the electromagnetic environment would be very quiet, resulting in a very good signal-to-noise ratio for communications.

Wang Ning said that a world with only one person is indeed hassle-free, even the sub-audio for repeaters is unnecessary since there's only you talking.

That evening, the girl charged her handheld radio to full.

Baofeng UV9R waterproof version.

She followed Bai Zhen and Wang Ning's instructions to find a waterproof handheld radio, and on Zhujiang Road, Ban Xia found a total of eighteen well-preserved waterproof handhelds—Motorolas, Yaesus, big brands defeated one after another. In the end, only the widely available hundred-yuan miracle Baofeng UV9R was still functional.

Turn on the Icom725 radio.

Turn on the GR3188 analog relay.

Ban Xia took a deep breath. She had been busy for a whole week for this moment, success or failure hinged on this.

She gently twisted the power knob on top of the handheld, and the LCD lit up.

On a night with a sky full of dazzling stars, the girl left her room, climbed onto the attic, sat on the roof, and began telling BG4MXH about the stars she saw.