Chapter 59: Pages and Frequencies

05:40. The alarm had not rung. His body clock woke first. Lin Chen opened his eyes. Ceiling. Water stains. Like a dried riverbed. He turned onto his side. His left foot tested the floor. The scab tightened. A stab of pain. He paused. Breathed. Shifted his balance. Stood up. Dressed. Quiet movements. Did not touch the bedframe. Canvas bag. Opened flat. Old tin box. Screwdriver. Multimeter. Electrical tape. Rosin. Solder. Counted them out. Nothing missing. He pulled the zipper shut. Weight evenly balanced. Out the door. The hallway was empty. The motion-sensor light was broken. His footsteps fell on the terrazzo floor. Short echoes. Cold. The air smelled of chalk dust and old wood. He breathed out. White mist scattered. Stride length: thirty centimeters. Do not step on the frost line.

06:15. School library. Side entrance. The iron lock was rusted. The key turned with a scrape. The old librarian opened the door. Cotton coat. Oily cuffs. His glasses were fogged white. “You’re here. Basement. Old periodicals. Move them by bundle. Shelve them. Count them. If the number matches, I pay. Don’t drop them. Don’t get them wet. Lots of dust. Bring your own mask.” Lin Chen nodded. Down the steps. Cement floor. Damp. Mildew. Mixed with the acidic smell of old paper. The light was dim yellow. A forty-watt incandescent bulb. Its filament trembled faintly. Bundles of journals. Tied with hemp rope. Twenty volumes per bundle. Heavy. About fifteen jin. He squatted. Lifted one into his arms. Stood. Shifted his center of gravity to the right. Left foot suspended. No pressure on it. Stride length. Twenty centimeters. Stairs. Narrow. Steps high. He counted. One. Two. Three. Matched breathing to his steps. No panting. Sweat seeped through. Undershirt damp. Cold wind poured in through the vent. Stuck to his back. Ice-cold.

He carried. Shelved. Sorted. By call number. Neat rows. His fingers were numb with cold. The pads chafed raw. Blood seeped out. He ignored it. Kept going. Count. One hundred. Two hundred. Three hundred. Four hundred. Five hundred. Five hundred sixty. The old librarian checked against the list. Nodded. Took out money. Five one-yuan notes. Old, but flat. Handed them over. “Quick hands. Coming again tomorrow?” Lin Chen took the money. Slipped it into his pocket. Touched the account book. “Depends on the time.”

Funds: fifty-one yuan five jiao. Shortfall: twenty-three yuan five jiao.

07:40. Back to the dorm. Cold water. Washed his face. Changed the dressing. Iodine. Cotton swab. The edge of the scab had turned pale. No pus. Wrapped it tight. Put on his shoes. Tied the laces. Canvas bag. Heavy, but steady. Out the door. Hallway. Empty. Footsteps on terrazzo. Short echoes. Cold. Stride length: thirty centimeters. Do not step on the frost line.

07:55. Laboratory. Iron door. Already open. Heating. Not on. Room temperature below freezing. Group A students were already there. Twelve of them. Top three. Advanced group. Lin Chen. Chen Hao. One other. Sat in the front row. Old Li stood before the blackboard. Chalk. Circuit diagram. High frequency. LC resonance. Frequency-selective network. Q factor. Bandwidth. Parasitic capacitance. Shielding.

08:00. Old Li tapped the board. “High-frequency module. Debugging test. Time limit. Two hours. Target. Center frequency: 10.7 MHz. Bandwidth: ±150 kHz. Gain: twenty decibels. Noise: below three decibels. Instruments. Take your own. Parameters. Measure them yourselves. Record everything. If the error exceeds the limit, eliminated. Begin.”

Lin Chen stood. Collected the equipment. Signal generator. Oscilloscope. Spectrum analyzer. Old models. Heavy. Too many knobs. He wired them up. Shielded cable. Coax. Tightened the connectors. No looseness. Ground clip. Bit down hard. The metal was cold. He powered on. Preheat. Five minutes. He waited. His finger traced on the tabletop. Equivalent circuit. Inductance. Distributed capacitance. Parallel resonance. Formula. f = 1 / (2π√LC). Calculation. L needed to be 1.5 μH. C needed to be 150 pF. He took the coil. Wound it. Enameled wire. 0.5 mm. Plastic core. Twenty turns. Tight, without overlap. He measured. Inductance meter reading: 1.48 μH. Close. He fine-tuned the spacing. Loosened half a turn. Reading: 1.50 μH. Stable.

He connected the capacitors. Mica. 120 pF. In parallel with a 30 pF trimmer. Effective value on paper: 150 pF. Add distributed capacitance, about 10 pF. Total: 160 pF. Too high. He removed them. Swapped them. 100 pF plus 50 pF. Adjusted the trimmer. The damping on the screw was stiff. He applied force evenly. Fingertips feeling resistance. Half a turn. Stop. Measured resonance frequency. 10.68 MHz. Error: 0.2%. Qualified.

He connected the transistor. 3DG6. Bias network. Resistor divider. Stable operating point. He measured voltages. Collector: 6 V. Base: 1.2 V. Emitter: 0.6 V. Normal. He fed in a signal. 10.7 MHz. Amplitude: 10 mV. On the oscilloscope. Sine wave. No clipping. No distortion. He adjusted the gain knob. Output: 100 mV. Calculated. Twenty decibels. On target.

Forty minutes in. The scab on his left foot split open. Blood seeped out. The gauze turned wet and sticky. He ignored it. Shifted his weight right. Breathing even. Fingers numb with cold. Knuckles pale. He breathed warm air over them. White mist dispersed. Kept measuring. Noise. Spectrum analyzer. Flat baseline. No spurs. Reading: 2.8 dB. On target.

He recorded it all. Pen on paper. Numbers clear. No erasures.

One hour twenty minutes. Chen Hao handed in his work. Stood. Left. His footsteps were light. Confident. Door opened. Door closed. Wind rushed in. Cold.

Lin Chen did not look up. Kept going. Re-tested. Three sets of data. Recorded. Cross-checked. Formulae. Verification. No mistakes. He checked the wiring. No looseness. No short circuits. Shielding intact. Grounding reliable.

One hour fifty minutes. He put down the pen. Powered off. Removed the leads. Tidied the bench. No clutter left. Wire ends straightened. Instruments returned to place. Knobs back to zero. Probe coiled and secured.

He stood up. Handed in the paper. Flat, uncreased. Passed it over.

Old Li took it. Looked. Three sets of data. Frequency error. 0.1%. 0.2%. 0.15%. Gain stable. Noise within spec. He raised his head and looked at Lin Chen. Dark circles under his eyes. Lips cracked dry. Chilblains purple on his skin. But his hands were steady. No tremor. Rosin and copper rust under his nails.

“How did you do the shielding?”

“Copper foil wrap. Overlapping seams. Single-point ground. Avoid loops.”

“How did you stabilize the bias?”

“Voltage divider resistors. Add emitter negative feedback. Compensate temperature drift.”

Old Li nodded. No praise. No scorn. “Sit. Wait for the result.”

The lab was quiet. Only the faint whir of instrument cooling fans. The smell of rosin thickened in the air.

Two hours. Up. Old Li collected the papers. Checked them. Scored them. Chalk on the blackboard. Ranking list. The handwriting was thick and heavy.

Advanced group. Twelve people. Lin Chen, first. Chen Hao, second. Third through twelfth, in order.

Old Li turned around. “Advanced group, passed. Tomorrow, joint tuning. System-level testing. You will need your own oscilloscope probe. High impedance. Low capacitance. Hard to buy on the market. None in storage. Solve it yourselves. Late arrival means elimination.”

He paused. His gaze swept over Lin Chen. “Lin Chen. Stay. There’s work.”

The students stood. Packed up. Left. Footsteps cluttered together. Door opened. Door closed. Wind poured in. Cold.

Only two people remained in the lab. Old Li walked to Lin Chen’s table. Set down an old spectrum analyzer. Deep scratches on the casing. Dim screen. Loose knobs. Imported model. Manufactured in 1988. Local oscillator out of lock. Mixer aged. IF filter drifting.

“Discarded by the provincial team. Old machine,” Old Li said. “If you can fix it, fix it. Thirty cash for one machine. Paid on the spot. If you can’t, you work for nothing. Bring your own tools. Parts from the storeroom. Time limit: three hours. Start.”

Lin Chen looked at the machine. Reached out. Touched the casing. Cold, but faintly vibrating. Powered test. He did not hesitate. Opened his bag. Took out his tools. Screwdriver. Multimeter. Soldering iron. Rosin. Solder. Electrical tape. Copper foil. Shielded wire.

He disassembled it. The screws were rusted. Hard to turn. He increased pressure. Steady. No slipping. The casing opened. Thick dust. Yellowed circuit board. Oxidized solder joints, blackened. He measured the power supply. Output: fifteen volts. Normal. The local oscillator had lost lock. He checked the crystal oscillator. Aged. Frequency shifted. He removed it. Replaced it with a new one. Bent the leads. Secured it. Heated with the iron. Fed solder. Pulled away. The joint was full, smooth, no burrs.

The mixer had aged. He adjusted the bias trimmer. Knob stiff. He applied force evenly. Did not strip it. The screen lit. Raster stable. No flicker. He tuned the IF filter capacitance. Fine adjustment. Compensated the drift. Waveform clear. No distortion.

Two hours forty minutes. He reassembled the casing. Closed it. Tightened the screws. Powered it on. Tested. Signal input. Spectrum stable. Peak accurate.

He stood and handed the machine over.

Old Li looked at the screen. Nodded. “Good. Thirty. Cash.” He took out the money. The bills were old, but flat. Handed them over.

Lin Chen took them. Slipped them into the inner pocket close to his body. His fingers brushed the edge of the account book. Curled pages. Rough paper scraping his skin.

Old Li said, “Tomorrow. Seven o’clock. Assemble in the lab. Joint system tuning. High-frequency module plus IF demodulation. You need to make your own probe. High impedance. Low capacitance. Can’t buy it on the market. Wind it yourself. Specs: ten megohms. Ten picofarads. Error plus or minus five. If you can’t make it, eliminated.”

“Understood.”

Lin Chen slung the canvas bag over his shoulder. Out the door. Hallway empty. Footsteps on terrazzo. Short echoes. Cold.

He touched his pocket. Thirty yuan. Added to the previous fifty-one yuan five jiao. Total: eighty-one yuan five jiao. Shortfall: zeroed out. Surplus: six yuan five jiao.

No joy. No sorrow. In his mind there were only formulas. Routes. Countermeasures. Time windows. Limits of stamina. Three lines crossing in the dark. Not colliding. Not tangling. Each moving forward on its own.

He walked. Stride length: thirty centimeters. Do not step on the frost line.

Ahead, a new notice had been posted on the bulletin board. White paper. Black print. Provincial competition. Joint-tuning outline issued. System-level testing includes a complete closed-loop signal chain. Hand-drawn schematic and PCB layout required. Submit by tomorrow morning.

He stopped and read. Schematic. PCB layout. High-frequency traces. Impedance matching. Ground partitioning. Shielding. He memorized the required parameters. The route.

He turned and headed back to the dorm. Wind passed through the corridor with a low whistle.

He closed his eyes. In his mind there were no curves. Only solder joints. Temperature. Time. Molten solder. Solidification. Three lines crossing in the dark. Not colliding. Not tangling. Each moving forward on its own.

He opened his eyes. Stride length: thirty centimeters. Do not step on the frost line.

Forward.