Chapter 91: Cold Start

Daylight had not yet broken. The motion-sensor light in the corridor was off. Lin Chen opened his eyes. He did not get up at once. First he flexed his toes. Under the dressing on his left foot, the skin had a faint sticky pull to it. The edge really had gotten damp. Sweat mixed with iodine. He slowly bent and straightened his ankle. The pain stayed within an acceptable threshold. His gait plan was still valid. He threw back the thin blanket, sat up, put on his shoes. When he tightened the laces, he deliberately left half a finger's width of slack to keep pressure off the wound.

At six sharp, he turned on the tap. Cold water washed over his face. He wrung out the towel, folded it, put it back where it belonged. Backpack check. Admission ticket. ID card. Black fountain pen. Spare refills. Eraser. Scratch paper. Everything in place. He touched his pocket. Seven yuan and three jiao. The bills were flat, the coins icy. He would not need to spend them. Drinking water would be provided at the exam site. Lunch was a standardized boxed meal. The cost had already been included in the registration fee. He only needed to maintain minimum expenditure. The margin had to be kept for any sudden trouble in the afternoon.

He went out. Locked the door. Turned the key twice. Checked. The stairwell echoed. On the third step, his footfall landed. Weight first on the right foot. The left only touched lightly, then shifted across. The rhythm was steady, like some kind of mechanical transmission. The provincial capital's morning held a mist. The streetlamps were dim yellow. White smoke rose from the coal stove at the breakfast stall. The scorched fragrance of fried dough sticks mixed with the sweetness of soy milk and drifted over. He stopped and glanced at the price board. Fried dough sticks, two mao. Soy milk, one mao five. He swallowed. His stomach contracted slightly. Then he turned away. His energy reserves were enough to carry him through the practical exam. He did not need extra calories. Only alertness.

At seven twenty, the gate of the test center opened. The sound of the iron grilles being pulled apart was harsh. Candidates streamed in one after another. Most wore washed-out Dacron shirts or old jackets. Their expressions differed. Some murmured formulas under their breath. Some sat with eyes closed. Some checked their tool kits again and again. Lin Chen moved with the crowd. He did not talk. He did not look around. His eyes locked only on the main building ahead. The steps were high. He adjusted his breathing. One step. Two steps. Shift the weight. When his left foot came down, the heel touched first, cushioning, then rolled to the ball of the foot. The pain was absorbed by muscle memory. He climbed the steps and entered the hall.

The notice board was already ringed with people. A distribution map of the practical exam rooms was posted behind the glass. Exam Room Three. Third floor, east side. He memorized the room number and headed for the stairs. The wooden steps had been worn hollow by countless soles. The handrail was smooth with age and touch. He braced himself against the wall, avoided the crowd. The corridor on the third floor was long. The fluorescent tubes buzzed overhead. The air smelled of dust and old paper. The exam room door stood open. A proctor checked IDs at the entrance. He handed over his admission ticket. The man stamped it and let him pass.

Inside, the room was arranged in tiers. Twenty workstations. Each one had fixed equipment on it. An HP8591E spectrum analyzer in the center. A signal generator on the right. An oscilloscope on the left. A multimeter hanging from a rack. A set of attenuators assembled in a metal box. Cables coiled neatly. He went to his place. Station Seven. The desktop was scored with scratches. Rust ringed the screw holes. He set down his backpack, pulled out the chair, sat. His left foot rested flat. His right leg was slightly bent, keeping him ready to rise at any moment.

At seven forty-five, the proctor read out the rules. His voice was dry. Cold start. Fifteen minutes of warm-up. During that time, no one was to touch the calibration knobs. No powered testing. Violators would be disqualified. There were three practical questions in all. The first was baseline frequency calibration. The second, attenuator linearity testing. The third, unknown-signal capture and parameter back-calculation. Total score: one hundred. Manual calibration counted for forty points. An error greater than 0.5 dB meant an automatic deduction. He read it through twice. Lin Chen nodded. His gaze swept over the equipment. The HP8591E's power switch was at the lower right, red plastic, its edges worn. He reached out. His fingertips hovered. He did not touch it. He waited.

At eight o'clock sharp, the whistle blew. Power on. He pressed the switch. A relay inside the machine clicked. The fan began to turn. A low-frequency hum rose from the bottom of the chassis. The vents breathed out a faintly warm current of air. The screen lit up. Green points flickered. The self-test program ran. The progress bar crawled upward. Fifteen minutes. He leaned back in the chair and closed his eyes. In his mind he replayed Plan C. Segmented approximation. If the knob's damping was heavy, each turn should be no more than five degrees. Pause for three seconds. Observe the waveform change. If the scale was blurred, switch the oscilloscope to X-Y mode. Use the Lissajous figure to infer the phase difference, then convert it into a dB value. Every step had already been broken down. Muscle memory was standing by.

His left foot began to swell. Under the dressing, the skin burned. He shifted his posture slightly, moving all his weight onto the right foot. He lifted the heel of the left foot, supporting himself only on the ball. The pain was dispersed. He opened his eyes and looked at the screen. The self-test was complete. The main interface appeared. Frequency range: 9 kHz to 22 GHz. Resolution bandwidth adjustable. Reference level: 0 dBm. He reached out and gripped the calibration knob. The metal surface was cold. The damping was moderate, but heavier than expected. He turned it one click. The baseline on the screen jumped. 0.1 dB. He let go and waited for it to stabilize. Three seconds. The waveform settled. He continued. Second click. 0.2 dB. Pause. Third click. 0.3 dB. He slowed his pace. His fingertips felt the internal gear teeth engaging. There was a slight slack in it. He used that slack for fine adjustment. Fourth click. 0.4 dB. Fifth click. 0.45 dB. He stopped. His breathing slowed. The oscilloscope probe was already connected. Trigger mode set to auto. The sine wave on the screen was clear. He switched to measurement mode and read the peak-to-peak value. Converted it. 0.47 dB. Within tolerance.

Eight minutes had passed. He continued. Sixth click. The knob's resistance suddenly increased. A faint metallic scrape. He stopped. Did not force it. Used segmented approximation. Back half a click, then forward a quarter. The waveform on the screen transitioned smoothly. 0.49 dB. He wrote down the data. On the scratch paper he noted: damping peak near 0.5 dB. Compensation margin must be reserved. He looked up at the proctor. The man was making his rounds. His gaze swept across Lin Chen's station without pausing. Lin Chen lowered his head and continued. Seventh click. 0.48 dB. Eighth click. 0.46 dB. He stopped. Calibration complete. The manual section, worth forty points, was secured.

The whistle sounded again. First question over. On to the second. Attenuator linearity test. He opened the metal box and took out the standard attenuator set. The metal casing was heavy. The connectors were oxidized. He wiped them and inserted them into the spectrum analyzer's RF input. His movements were steady, unhurried. His left foot still hovered. The muscles in his calf were beginning to ache. He took a deep breath and treated the pain as background noise. Do not interfere with it. Do not amplify it. Just execute.

The signal generator output a 10 MHz reference signal at an amplitude of -10 dBm. He set the attenuator to 0 dB and read the spectrum analyzer display. -10.02 dBm. Error: 0.02. Pass. 10 dB. -20.05 dBm. Error: 0.05. Pass. 20 dB. -30.11 dBm. Error: 0.11. Close to the critical line. He checked the cable. A connector was loose. He tightened it and measured again. -30.04 dBm. Error: 0.04. Recovered. He continued. 30 dB. 40 dB. 50 dB. Each setting recorded. Each setting cross-checked. The data on the scratch paper grew denser and denser, like a net, trapping every variable.

Third question. Unknown-signal capture. He switched frequency bands. Scanned. The noise floor on the screen rose and fell. Then, suddenly, a sharp peak appeared. Frequency: 14.23 MHz. Amplitude: -25 dBm. He marked it, set the center frequency, narrowed the RBW. The waveform became clear. Sine. No modulation. He read the parameters. Recorded them. Worked backward. Calculated. The pen tip moved across the paper with a dry rustle, weaving together with the machine's hum. Time passed in silence.

At nine forty, the whistle for handing in papers sounded. He set down his pen. Checked the scratch paper. Complete data. Closed logic loop. He stood. His left foot touched the floor. The pain was sharp, but he straightened fully. His gait did not break. He packed up the equipment, put everything back in place. Cables coiled up. Attenuators back in the box. The workstation returned to its original state. He slung on his backpack and walked toward the door. The proctor collected the papers, stamped them, let him out.

In the corridor, some people sighed. Some quietly compared answers. Lin Chen did not look back. He went down the stairs. Shift the weight. One step. Two steps. Sunlight fell through the high windows and onto the stair treads. Dust floated in the shafts of light. He walked out of the building. The wind was cold. He touched his pocket. Seven yuan and three jiao. Still there. He lifted his head and looked at the sky. The clouds were thick, but there was light at the edges. He set off toward the hostel. His rhythm did not change. The margin had been used up. The next round awaited.