Chapter 93: Threshold

Night in the guesthouse had no sound, except for the dull drip of a faucet at the end of the corridor every dozen seconds or so. Lin Chen leaned against the headboard with his left foot resting on a folded old sweater. As the blood flowed back, the swelling pain turned blunt and heavy, like a sponge soaked full of water pressing hard against his ankle. He closed his eyes, but he was not sleepy. In his mind he kept running through that set of temperature-drift compensation formulas. T0 equals fifteen degrees. T equals nineteen. A temperature difference of four degrees. The oscillator’s aging coefficient had not been included; the actual frequency offset might be even greater than 0.028 megahertz. He took out a pencil and worked through it again on a blank space in his corrections notebook. Introduce the time variable t. The heat-dissipation curve approximates exponential decay. The temperature rise is fastest in the first fifteen minutes. When he made the manual compensation, the probe contact point had happened to lie in the cooling blind spot on the left side of the chassis. The temperature gradient, layered on top of contact resistance, had raised the baseline noise. If the review tested only Question Three, what would the examiners ask? Not the formula, but the logic of the operation. He had to prove that the fluctuation had not been a mistake, but a reasonable reading under environmental interference, and that it had already been cross-verified through the subsequent band scan.

He stopped writing. His stomach felt frighteningly empty. Seven yuan three jiao. He opened his ledger. Extension of lodging: an extra one yuan five jiao. Tomorrow morning, two steamed buns and hot water: eight jiao. Hard-seat return ticket: three yuan five jiao. One yuan five jiao left. The accounts were clear. There was no margin. He closed the ledger and sharpened the pencil. The point touched the paper. The soft scratch sounded crisp in the quiet room. He wrote out the likely review procedure from memory. Power-on self-check. Parameter setting. Signal capture. Error explanation. He broke every step down to the level of individual motions. Reality had no ifs. The exam paper had already been handed in. The deduction was an established fact. All he could do was patch the hole. Next time. Or, if there was a next time.

Five in the morning. It was still dark. Lin Chen got up. The moment his left foot touched the floor, the stabbing pain made him suck in a breath. He slowly worked his ankle, confirming the joint’s range of motion. Washed up. Splashed cold water on his face. In the mirror, the person looking back had sunken eye sockets and cracked lips. He straightened his old jacket and tucked the corrections notebook, admission slip, and that stack of draft papers into the inner pocket. He pulled the zipper all the way to the top. The coins pressed against his thigh, hard and solid. He went downstairs. The guesthouse owner was dozing behind the counter. Lin Chen settled the bill in a low voice. The owner did not even lift his eyelids; he only tore off a receipt and handed it over. Lin Chen pushed open the door. The fog was thick. The concrete ground gleamed with damp. The air smelled of coal smoke and wet earth. He headed toward the exam compound. His stride controlled. Center of gravity shifted right. Left foot touching down lightly. The pain was real, but the rhythm could not be allowed to break.

By seven-thirty, people had already gathered in the compound. A long queue had formed in front of the glass notice case by the Academic Affairs Office. Lin Chen stood at the edge of the crowd. He did not jostle. He did not crane his neck. He simply waited. At exactly nine, two teachers came out carrying an official document with a red header. They taped it to the glass. The crowd surged forward at once. The rasp of paper, sharp intakes of breath, the sound of stifled sobbing all mixed together. Lin Chen waited three minutes. When the press of people eased a little, he walked up. His gaze swept from top to bottom. Final interview list for the Provincial Polytechnic Experimental Class in Electronic Information. Twenty spots. His name was on the seventeenth line. Lin Chen. Qinghe County. Composite score: 84.6. Interview cutoff: 85.0. Short by 0.4 points.

He stared at that number. No racing heartbeat. No dizziness. Only confirmation. 0.4 points. Within the tolerance range of the temperature-drift error. He continued reading. A note below said: candidates with composite scores between 83.0 and 87.0, please report to Laboratory Three at 10:30 this morning for an on-site review. Those who pass will be admitted as alternates to the final interview list. Those who do not pass will have their listing voided.

He stepped back, giving up his place, then turned and walked toward the laboratory. The corridor was long. The paint on the walls had peeled away, exposing the red brick beneath. He walked very slowly. At every step he checked his balance. If his left foot could not bear weight, then his right leg and core muscles would compensate. His muscles had begun to ache with fatigue. He ignored it. He kept his eyes fixed only on the room number. Laboratory Three.

The door was open. Inside there was only one HP8591E. Beside it sat two examiners. One wore glasses and a gray jacket; the hair at his temples had gone white. The other was younger and held a scoring sheet and a stopwatch. Lin Chen knocked, entered, bowed, and reported his admission-slip number. The examiners nodded and motioned for him to begin.

“Question Three. Unknown-signal capture. You have twenty minutes. The equipment has already been powered on and preheated,” said the examiner in the gray jacket.

Lin Chen stepped forward and checked the equipment. The power indicator was a steady green. The cooling fan was running smoothly. The screen was already sitting on the test-ready interface. The room thermometer showed 21°C, two degrees higher than yesterday. He put on the antistatic wrist strap, connected the probe, brought up the self-check record first, confirmed that the warm-up time and status were normal, and then set the scanning parameters. Center frequency 14.2 MHz. Span 500 kHz. RBW 100 Hz. VBW 30 Hz. The scan began.

The baseline noise on the screen was stable. A sharp peak appeared at 14.23 MHz. Amplitude -25.1 dBm. He marked it. Took the reading. Stable. No fluctuation.

“There was a north wind in the exam room yesterday. The equipment was by the window,” the younger examiner said suddenly. “Your reading fluctuated at the time. How did you handle it?”

Lin Chen did not raise his head. His fingers made a minute adjustment on the knob. “Record the initial reading. Switch to scanning the adjacent band. Compare the change in baseline noise. Confirm that it is not modulation from the signal source. Introduce the variable of the ambient temperature gradient. Manually compensate for the combined error from contact resistance and crystal temperature drift. Use the average of three scans as the final data.”

“And the formula?” asked the examiner in the gray jacket.

Lin Chen took the draft paper out of his inner pocket and handed it over. On it was the temperature-drift compensation curve he had derived the night before. The T-t relationship. The error-correction term. The examiner took it, looked at it for ten seconds, then raised his eyes to Lin Chen. “What if draft paper were not allowed on site?”

“Mental calculation. Remember the coefficient. 0.5 ppm per degree Celsius. In the 14-megahertz band, with a four-degree temperature difference, the offset is 0.028 megahertz. Convert it into amplitude error and add it into the margin of manual calibration. It does not exceed 0.5.” Lin Chen’s voice was steady. His pace was even. It did not sound recited. It sounded like the statement of a physical fact.

The examiner set the paper down and ticked the scoring sheet. The pen tip passed lightly over the page. “Review passed. Composite score corrected to 85.2. You are entering the final interview list.”

Lin Chen nodded. He put away the draft paper, straightened the cables, powered down the machine, stepped back, bowed, and turned to leave.

When he walked out of the laboratory, sunlight had pierced the fog and fallen across the concrete ground. He leaned against the corridor wall and let out a long breath. At last his left foot could no longer hold him and began to tremble slightly. He sat down and fished the coins from his pocket. One yuan five jiao. Last night’s lodging and breakfast had already been deducted. The return ticket cost three yuan five jiao. He was still short by two yuan. The final interview notice would be issued tomorrow. Whether he went on to the next round or not, he first had to work out the travel fare and the collision with the timing of the first mock exam. He needed to hurry back to the county town. His mother was waiting for news. His younger brother’s medicine could not be interrupted.

He opened the ledger, crossed out “review pending,” and wrote: Review passed. Enter final interview. Cost: to be calculated. Cash on hand: one yuan five jiao. Next step: return trip. Gap: two yuan. Solution: walk to the suburban stop, save one yuan five jiao; switch from the regular hard seat to the slow train, save another five jiao; push the actual fare down to one yuan five jiao. Accounts balanced.

He closed the ledger, got up, and headed for the station. His pace was slow, but his direction was clear. Wind came around the street corner carrying the damp chill of early spring. He slipped his hand into his pocket. His fingertips touched a stiff piece of paper. It was what he had picked up yesterday at the gate of the exam compound: an evening newspaper from the provincial capital. The front-page headline read: “State Education Commission Issues Notice: Pilot Program Adds Basic Computer Application Assessment for Science Students.” He stopped. Pulled out the newspaper. His eyes rested on the words basic computer application. The paper was rough. The smell of ink was sharp. He looked at it for a long time, then folded it and slipped it into his inner pocket.

The station broadcast was sounding. Departure time. He quickened his pace. Left foot down. Painful. But he could still walk. The road ahead was long. But its direction had already changed. He took out the family letter he still had not opened. The edges of the envelope were already worn. He did not tear it open. He only placed it side by side with the newspaper in his inner pocket. Through the cloth, he could feel the thickness of the paper. He raised his head and looked at the sky. The clouds were breaking apart, showing a patch of blue. He stepped forward. Toward the station. Rhythm unchanged. Margin cleared. Next round, to be continued.