I started with a ship full of max-level veterans, and I'm just a complete noob.

The wind outside the bunker had been blowing non-stop since evening. First it was sand, then it turned into snow, and then the sand and snow mixed together, hitting the metal ventilation pipes and making a dense rustling sound.

Lu Qinghe turned up the collar of his military overcoat, held it between his chin, and used both hands to remove the front panel of the receiver.

The screws were Soviet-made flathead screws, and the screwdriver would slip if it was even slightly off-center. Her fingers were frozen stiff, and after twisting three screws in a row, blood seeped out from the old crack at the knuckle of her index finger. She bent down, bit the tip of her glove with her teeth, and took off the glove, continuing to twist with her bare hands.

The panel was removed, revealing the circuit cavity inside. The old solder joints were covered with a layer of fine sand. She blew on it twice, and the sand flew up, making her cough and turn her head to the side.

Chen Zhiyuan squatted in the corner, cranking the hand-cranked generator. The belt squeaked on the wheel, producing a grinding sound with each rotation.

"Is the voltage enough?" Lu Qinghe asked without looking up.

"Sixty-five volts, almost there, I'll speed it up a bit more." Chen Zhiyuan's voice was panting, and the speed of the hand cranking increased significantly, turning the belt's sound into a continuous shrill noise.

"That's enough, don't exceed seventy."

The wooden box, sent from Beijing via confidential mail, arrived last night. It was wrapped in three layers of oil paper and a layer of moisture-proof cloth. Inside were two palm-sized metal shielded boxes, with DBM-01 and DBM-02 written on them in pencil.

Along with the wooden box came two pages of wiring instructions, written in Jiang Ming's handwriting. The handwriting was neat but messy, showing that he had written it in a hurry. The last line read, "Local oscillator injection power 10mW, not exceeding 15mW."

Lu Qinghe had spent three hours studying the circuit diagrams and wiring sequence on those two pages. Disconnecting the original single-ended mixer stage of the receiver and inserting a double-balanced mixer at the front end required modifying seven solder joints.

The soldering iron tip was red-hot. She dipped it in rosin, first disconnecting the input terminal of the original mixer tube, then wiping the leads clean from the pads. Next, she threaded the RF leads of the DBM-01 through the pre-drilled vias on the side of the chassis, aligned them with the empty pads, applied solder, and soldered them in place.

She examined each solder joint closely with a magnifying glass to ensure the solder surface was smooth and free of cold solder joints before moving on to the next one.

The external frequency sweeping interference surged in wave after wave. Although the receiver disconnected the mixer stage and did not output audio, the white light on the oscilloscope connected to the antenna end monitoring port had been stretched into a solid line with almost no breaks.

The entire 5.2 to 5.4 MHz band was completely filled, and useful signals were completely drowned out.

Chen Zhiyuan cranked the generator for half an hour until his arm ached so much he could barely lift it, so he switched to his left hand and continued.

"Is it coming soon?"

"The last shielded cable."

Lu Qinghe soldered the last copper wire of the braided shielding layer to the grounding copper post of the chassis, used a multimeter to check the continuity, and found it to be conductive. He then measured the insulation between the shielding layer and the signal line, which was infinite.

She put the front panel back on, only tightening two screws at opposite corners to secure it, ignoring the rest.

The local oscillator was a small crystal oscillator module that was shipped from Beijing in a wooden box. Its frequency was marked as 5.245 MHz. Lu Qinghe connected its output to the LO port of the DBM-01, and connected the intermediate frequency output to the frequency selector amplifier, tuning it to the difference frequency position.

After checking all the connections twice, she took a deep breath and reached out to turn off the power switch.

Nothing happened for the first three seconds; the output meter pointer of the frequency selective amplifier remained at zero.

Then, the white light that was originally stretched into a solid line on the oscilloscope screen suddenly broke in the middle with a slit. The slit widened and the white light retreated to both sides of the screen, revealing a relatively clean dark area in the middle.

The pointer of the frequency selective amplifier jumped up and down, first swaying wildly. Lu Qinghe fine-tuned the fine-tuning capacitor on the side of the local oscillator module, and the pointer stabilized, stopping at a fixed position, swinging left and right in a regular rhythm.

That was the outpost's call signal, short-long-short-long, repeated three times—the standard patrol unit contact code.

Chen Zhiyuan slowed down his hand cranking speed. He heard the sound coming from the speaker of the frequency selective amplifier. Although it still had background noise, the regular ticking was undeniably clear.

"The Beijing solution works!" He loosened the crank of the generator, let his arm hang down and swung it a couple of times, his voice trembling with excitement.

Lu Qinghe did not respond to this statement; her attention was entirely focused on the oscilloscope.

The interference has subsided considerably, but it has not completely disappeared. Residual common-mode components can still be seen fluctuating at the edge of the frequency band. The amplitude is small and does not affect signal recognition, but it indicates that the balance of the bridge circuit is not perfect.

She pulled a blank data record sheet from the bottom of the toolbox, wrote the date and time in the header with a pencil, and then began to record each item.

Ambient temperature: -14 degrees Celsius.

Local oscillator injection power: The actual measured power is about eight milliwatts, which is lower than the optimal value indicated in the instruction manual.

Common-mode residual amplitude: approximately -35 dB, which is 12 dB lower than the theoretical value.

Parasitic component frequencies: concentrated around 5.21 MHz, possibly related to the temperature drift of the local oscillator module.

Receiver sensitivity recovery status: The patrol call signal level is approximately -95 dBmW, and the signal-to-noise ratio is approximately 18 dB, which is barely usable.

She filled in all the data and then stopped writing in the remarks column.

The pencil tip touched the paper, leaving a small dot. She looked at the dot for a few seconds, then wrote a line.

Thank you for the double bridge; the ears of the soldiers at the front have been revived.

After she finished writing, she stared at the line of text for a moment, did not cross it out, folded the data sheet and put it into a confidential envelope.

Chen Zhiyuan has restarted the generator to maintain the voltage for the telegraph machine.

Lu Qinghe sat down in front of the telegraph machine, converted the contents of the data sheet into Morse code word by word, and began to send the message by pressing the key.

The wind and snow outside the bunker continued unabated, with sand and snowflakes whistling through the metal pipe openings, and the telegraph key's click sounding faint and crisp in the desert.

The radio waves pierced through the darkness and snow, traversing thousands of kilometers of Gobi Desert and plains, heading towards Beijing.

But at this very moment, thousands of kilometers away in eastern Beijing, in the corridor outside the 502 research room of the Third Electronics Factory, a tall man wearing a thick woolen overcoat was standing at the door.

The door didn't open, and he didn't knock. He just stood there, staring at the newly hung plaque on the door with his gray-blue eyes that read "502 High-Frequency Microwave Electron Tube Research Laboratory".

Ivanov put his hands in his coat pockets, exhaled a puff of white mist, stood for about ten seconds, and then raised his right hand and tapped three times.