Chapter 93: Threshold

There was no sound in the guesthouse at night, only the dull tap of a faucet at the end of the corridor dripping once every dozen seconds or so. Lin Chen leaned against the headboard, his left foot propped on a folded old sweater. As the blood flowed back, the swelling pain turned heavy and blunt, like a sponge soaked full of water pressing hard against his ankle joint. He closed his eyes, but sleep would not come. In his mind he kept running through that set of temperature-drift compensation formulas. T0 equaled fifteen degrees, T equaled nineteen, a difference of four degrees. The aging coefficient of the crystal oscillator had not been factored in; the actual frequency drift might be greater than 0.028 megahertz. He took out a pencil and recalculated on a blank page of his corrections notebook. Introduce the time variable t. The cooling curve approximates exponential decay. The temperature rises fastest in the first fifteen minutes. When he compensated manually, the probe contact point happened to be in the heat-dissipation blind spot on the left side of the chassis. The temperature gradient, layered with contact resistance, caused the baseline noise to rise. If the review only tested the third problem, what would the examiners ask? Not the formula, but the operating logic. He had to prove that the jitter was not a mistake, but a reasonable reading under environmental interference, and that it had been cross-verified by subsequent frequency-band scans.

He stopped writing. His stomach felt hollow with hunger. Seven yuan and three jiao. He opened his ledger. An extra one yuan and five jiao for extending the lodging. Two steamed buns and hot water tomorrow morning, eight jiao. Hard-seat train ticket for the return trip, three yuan and five jiao. One yuan and five jiao left. The account was clear. There was no room to maneuver. He closed the notebook. Sharpened the pencil. The point touched the paper. In the quiet room, the scratch of graphite sounded crisp. He copied out the possible review procedure from memory. Power-on self-test. Parameter setup. Signal capture. Error explanation. He broke every step down to the level of physical actions. Reality had no ifs. The paper had already been handed in. The deduction of points was an established fact. All he could do was patch the holes. Next time. Or, if there even was a next time.

Five in the morning. It was still dark. Lin Chen got up. The instant his left foot touched the floor, a sharp stab of 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 man staring back at him had sunken eye sockets and cracked lips. He straightened his old jacket, tucked the corrections notebook, admission ticket, and that stack of draft pages into the inner pocket. Pulled the zipper all the way up. The coins pressed against his thigh, hard and solid. Downstairs. The guesthouse owner was dozing behind the counter. He settled the bill softly. The owner did not even lift his eyelids, only tore off a receipt and handed it over. He pushed the door open. The fog was thick. Dampness glistened on the concrete. The air smelled of coal smoke and wet earth. He headed toward the exam compound. Controlled stride. Weight shifted to the right. Left foot touching down lightly. The pain was real, but the rhythm could not be thrown off.

At seven-thirty, people had already gathered in the compound. A long line had formed in front of the Academic Affairs Office's glass notice board. Lin Chen stood on the outer edge of the crowd. He did not jostle. Did not crane his neck. He simply waited. At nine sharp, 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, muffled sobs all mixed together. Lin Chen waited three minutes. When the press of people eased a little, he walked up. His eyes scanned from top to bottom. Provincial training-team list. Twenty slots. His name was on the seventeenth line. Lin Chen. Qinghe County. Composite score: 84.6. Cutoff: 85.0. Short by 0.4 points.

He stared at that number. No racing heartbeat. No dizziness. Just confirmation. 0.4 points. Within the tolerance range of the temperature-drift error. He kept reading. A note below said: Candidates with composite scores between 83.0 and 87.0, please report to Laboratory Three at ten-thirty this morning for an on-site review. Those who pass the review will be admitted as replacements. Those who fail will have their listing voided.

He stepped back, giving up the spot. Then turned and headed for the laboratory building. The corridor was long. The wall paint peeled away, exposing the red bricks beneath. He walked very slowly. Every step was a deliberate check of his balance. If the left foot could not bear weight, then the right leg and his core muscles would compensate. The muscles began to ache with fatigue. He ignored it. He kept his eyes only on the room number. Laboratory Three.

The door was open. Inside there was only one HP8591E. Two examiners sat beside it. One wore glasses and a gray jacket, his sideburns gone white. The other was younger, holding a score sheet and a stopwatch. Lin Chen knocked. Entered. Bowed. Reported his admission-ticket number. The examiners nodded and motioned for him to begin.

"Problem Three. Capture an unknown signal. You have twenty minutes. The equipment has already been powered on and preheated," said the examiner in the gray jacket.

Lin Chen stepped forward. Checked the equipment. The power indicator was steady green. The cooling fan was running smoothly. The room thermometer showed 21°C, two degrees higher than yesterday. He put on the anti-static wrist strap. Connected the probe. Powered up. Self-test. The screen lit. He set the scan parameters. Center frequency 14.2 MHz. Span 500 kHz. RBW 100 Hz. VBW 30 Hz. The scan began.

The noise floor on the screen was steady. A sharp peak appeared at 14.23 MHz. Amplitude: -25.1 dBm. He marked it. Took the reading. Stable. No jitter.

"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 look up. His fingers made a minute adjustment on the knob. "Record the initial reading. Switch to adjacent-band scanning. Compare the changes in baseline noise. Confirm that it is not source modulation. Introduce the variable of environmental temperature gradient. Manually compensate for the combined error of contact resistance and crystal temperature drift. Take the final data as the mean of three scans."

"And the formula?" asked the examiner in the gray jacket.

Lin Chen pulled a sheet of draft paper from 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 and looked at it for ten seconds. Then he raised his eyes to Lin Chen. "What if draft paper weren't allowed on site?"

"Mental calculation. Memorize the coefficient. 0.5 ppm per degree Celsius. In the 14-megahertz band, with a temperature difference of four degrees, the drift is 0.028 megahertz. Convert that into amplitude error and add it to the margin for manual calibration. It does not exceed 0.5." Lin Chen's voice was steady, his speaking rate even. It did not sound like recitation. It sounded like he was stating a physical fact.

The examiner set the paper down and ticked the score sheet. The pen tip slid lightly over the page. "Review passed. Composite score corrected to 85.2. Admitted to the team."

Lin Chen nodded. Put away the draft paper. Tidied the cables. Powered down. Stepped back. Bowed. Turned and left.

When he walked out of the laboratory, sunlight had begun to pierce the fog, shining onto the concrete. He leaned against the corridor wall and let out a long breath. At last his left foot could no longer hold him, and it trembled slightly. He sat down. Fished the coins from his pocket. One yuan and five jiao. Last night had already taken lodging and breakfast. The return ticket cost three yuan and five jiao. He was still short by two yuan. The training notice would be issued tomorrow. Room and board would be fully covered. Travel expenses were his own responsibility. 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 "Provincial Competition." Wrote: Admitted to team. Training camp. Cost: 0. Remaining: -2.0. Next step: return trip. Gap: two yuan. Solution: walk to the suburban coach station, save one yuan and five jiao. Change the hard-seat ticket to a slow train, save five jiao. The account balanced.

He closed the notebook, 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 thrust his hands into his pockets. His fingertips touched a stiff piece of paper. It was what he had picked up yesterday at the gate of the exam compound: a copy of the provincial evening paper. The front-page headline read: "State Education Commission Issues Notice: 1992 College Entrance Exam Subjects Adjusted, Pilot Assessment of Basic Computer Applications Added for Science Students." He stopped in his tracks. Pulled out the newspaper. His eyes rested on the words "basic computer applications." The paper was rough. The smell of ink was sharp. He looked at it for a long time, then folded it up and slipped it back into his inner pocket.

The station loudspeaker was calling departure times. He quickened his steps. Left foot down. Painful. But it 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 edge of the envelope was 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 looked up at the sky. The clouds had begun to part, revealing a patch of blue. He stepped forward. Toward the station. Rhythm unchanged. Margin cleared. Next round. To be continued.