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

The next afternoon, when the door to the confidential cubicle was closed again, the wind outside the factory area had not yet stopped.

Jiang Ming placed the measurement record book from last night on the corner of the table, and casually arranged the copper pillar and several cavity parts that he had taken out of the iron box in order.

The B-type tube has been running for over 460 hours, and the data has stabilized for now.

The security department hasn't received any new calls regarding the investigation of the light blue notepads; at the moment, the only thing that can be pushed forward is this seized equipment itself.

Fang Xudong drew an arc with the chalk in his hand on the blackboard. When it landed on the number to the right of the equals sign, he paused for half a second, then took half a step back to re-examine the entire derivation.

The light in the confidential cubicle was yellowish, making the edges of the formulas on the blackboard appear blurry.

Jiang Ming stood to the side, holding yesterday's measurement record book in his hand, his eyes following Fang Xudong's pen tip.

"The cavity depth is 8.2 mm, the suture width is 2.1 mm, and the inner diameter is calculated back to the equivalent diameter of the cavity based on yesterday's measurement of 29.1 mm."

Fang Xudong wrote and read aloud, filling in the data in the parentheses with the chalk.

"The resonant frequency of the cylindrical cavity TM010 mode is equal to 2.405 times the speed of light, divided by pi and multiplied by the equivalent radius."

Jiang Ming didn't interrupt, but simply did the calculations in the blank space of his notebook.

After Fang Xudong finished writing the last step, he circled the result in the lower right corner of the blackboard and turned around.

"2.8 to 3.1 gigahertz, right in the middle of the S-band."

Jiang Ming nodded and turned over the numbers he had calculated in his notebook.

"I substituted the upper and lower limits of the cavity depth into the equations, and the convergence range was about the same, from 2.85 to 3.05."

Fang Xudong raised his hand and used chalk to add a line of text about permanent magnet correction on the side of the blackboard.

"Magnetic fields contribute to the electron cyclotron frequency. The magnetic induction intensity measured yesterday was about 0.15 Tesla, and the cyclotron frequency was about 4.2 gigahertz."

Jiang Ming walked to the blackboard and added a string of numbers below the line Fang Xudong had written.

"However, when the magnetron is working, there is coupling between the electron cyclotron and the cavity resonance. The actual oscillation frequency will be pulled to near the cavity's natural frequency. The magnetic field mainly affects the start-up conditions and efficiency, and the frequency offset does not exceed three to five percent."

Fang Xudong stared at the string of numbers for a few seconds, then pointed to one of the coefficients.

"How did you determine this coupling correction factor?"

"Experience range".

Jiang Ming placed the chalk in the blackboard slot.

"When the cavity Q value is high, the magnetic field frequency pulling effect is weak, the correction amount is small, and the eight cavities are symmetrically distributed, so the Q value will not be too low."

Fang Xudong did not pursue the source of the coefficients further, but simply re-framed the corrected frequency range on the blackboard.

"From 2.92 to 2.98, take the midpoint, 2.95 gigahertz."

Jiang Ming wrote the number into his notebook, and marked the derivation path and the initials of the two people's signatures next to it.

Fang Xudong put down the chalk, wiped the white dust off his work clothes, and turned around. His tone was cautious, as if he had been thinking for a long time before speaking.

"Engineer Jiang, there's something I've never been able to figure out."

Jiang Ming looked up at him.

"The interference signal reported from the front lines has a center frequency of 4.5 MHz and covers broadband shortwave."

Fang Xudong pointed to the 2.95 gigahertz reading on the blackboard.

"This is microwave, in the 3 GHz range, while shortwave is 3 to 30 MHz, a difference of two orders of magnitude."

He stared into Jiang Ming's eyes.

"The magnetron generates microwave energy, so how could it become shortwave interference?"

Jiang Ming didn't reply. He turned around, walked to the iron box, and lifted a corner of the canvas.

They had already disassembled most of the main copper pillar inside the box, and the parts were arranged in order on the worktable.

He bent down and looked around the bottom of the box, his gaze lingering on a corner.

"Look at this."

Fang Xudong walked over.

There was a palm-sized circuit board on the left side of the bottom of the box. It had been pressed down by packaging shavings and was used as a support plate when the two people disassembled the main body.

Jiang Ming took it out and shone a flashlight on its front.

Two small black cylinders are soldered onto the circuit board, with their leads pointing downwards through the board surface. The solder joints are rough but firm.

There is a metal strip about two millimeters wide etched on the side of the plate, with a specific bent shape.

Fang Xudong leaned closer to examine the two black components and gently touched the outer casing with his fingernail.

"A germanium diode?"

"right."

Jiang Ming flipped the circuit board over, and there were several thin copper wires connecting the solder joints on the back.

"Two diodes and a microstrip line—are you familiar with this structure?"

Fang Xudong pushed his glasses up and stared at the bent metal strip for more than ten seconds, his expression changing from doubt to a kind of realization.

"Mixer".

"right."

Jiang Ming put the circuit board back on the workbench and drew a simple diagram in his notebook.

"The magnetron generates 2.95 GHz microwaves. After downconversion by this mixer stage, if the local oscillator is selected to be around 2.9455 GHz, the difference frequency will fall exactly at 4.5 MHz."

He drew an outward-pointing arrow at the end of the diagram.

"In addition to the frequency jitter and modulation noise of the magnetron itself, the output is a broadband noise signal centered at 4.5 MHz."

Fang Xudong stared at the diagram for a long time without saying a word.

Jiang Ming continued to break down the logic.

"Then this shortwave noise signal is connected to the outside antenna and radiated out, covering the front-line communication frequency band. From the outside, it looks like a high-power shortwave jammer, but in reality, its energy source is a microwave magnetron."

"So this is not a simple magnetron."

Fang Xudong's voice was a few decibels deeper than before.

"It's a complete system, including a magnetron with noise modulation, down-conversion mixing, shortwave power amplification, and antenna radiation."

"right."

Jiang Ming closed the notebook.

"The complete engineering chain, from microwave generation to tactical shortwave jamming, has corresponding modules at each step."

The confidential cubicle remained quiet for a while.

Fang Xudong walked back to the blackboard and added a line next to the frequency calculation results: "The downconverter mixer stage needs to be disassembled and tested in detail."

"I'll do some preliminary testing on this board this afternoon, measuring the microstrip line impedance and diode characteristics."

After Fang Xudong finished speaking, he added another sentence.

"Engineer Jiang, if this thing is truly a complete system, then the other party's engineering capabilities are far superior to what we previously estimated. It's not just that they have magnetrons; someone helped them turn magnetrons into weapons."

Jiang Ming did not respond to that sentence.

"Add this section to the report, indicate today's date, have both of you sign it, and the detailed analysis of the test panel can be written after you finish testing it."

He glanced at the clock on the wall.

2:40 PM.

In Workshop 1, the Type B tube test should have run for 468 hours.

He locked the toolbox, gave Fang Xudong some instructions, and went out through the south door of the confidential cubicle, walking across half of the factory area towards Workshop No. 1.

Xiao Zhao sat in front of the testing table, marking a number on a curve paper with a red ink pen.

Upon seeing Jiang Ming enter, he gestured with his chin to indicate the direction of the watch face.

The pointers of the five microammeters remained firmly in their original positions.

"The 470th hour has just passed."

Xiao Zhao pushed the notebook over.

"The pulse system of 0405 is normal, the iron core is at 36 degrees, and the battery pack voltage has not dropped significantly."

When Jiang Ming and his group looked over, the data, which was in sets of eight hours, looked like it had been printed on carbon paper and remained almost unchanged.

"Thirty hours left."

Xiao Zhao wrote these words in red pen on the blank space of the curved paper, pressing the pen harder than usual.

Old Sun walked over from the pulse transformer, holding a flashlight and a small screwdriver in his hand.

"I just checked the terminals, tightened two of them, and there were no loose ones. Da Liu has filled the coolant tank."

Jiang Ming responded and signed his name and the date on the same page of the notebook.

Thirty hours.

He had just sat down to look through the process report when the phone rang in the office next door.

Old Sun raised his eyelids slightly.

Jiang Ming had already stood up and was walking out.

"Jiang Gong."

The flat-topped clerk's voice came through the receiver, speaking slower than usual, as if he was carefully choosing each word.

"explain."

"Today we checked the personnel entry and exit records of the materials allocation department in September. I had someone copy down all the entry and exit records on the third floor."

Jiang Ming leaned against the wall and tapped the top cover of the telephone twice with his fingers.

"At 10:18 a.m. on September 13, there was a signature on the entry and exit logbook in the corridor opposite the collection window on the third floor."

The clerk flipped through the pages to confirm.

"The one who signed the contract was Xu Chongwen's young assistant."

Jiang Ming's fingers, which were tapping on the telephone, froze in mid-air.

"What's that distribution window on the third floor handing out?"

"The internal memo paper used by each department is the kind Liu Shouxin described: light blue background, smooth surface, and thinner than ordinary official document paper."

The officer lowered his voice slightly.

"This person went to the material allocation office without any official reason that day. I checked their unit's travel approval records, and on September 13th, his destination was listed as the East Suburb Chemical Plant."

The sound of pages turning could be heard over the phone.

"Director Wang already knows and asked me to report this urgently."

Jiang Ming stood in the dark office for a while. Outside the window, the streetlights of the factory area cut the shadows of the corrugated iron roofs into long strips and cast them onto the brick wall opposite.

"understood."

He looked at the shadow on the wall.

"We will notify you of any further developments."

When he hung up the receiver, his hand was a little heavier than when he answered the phone.

The distance between Xu Chongwen's assistant, the light blue patterned notepad, and the anonymous note in the union's mailroom is gradually shrinking to a point that can be measured with the naked eye.

Jiang Ming returned to Workshop No. 1. He did not stop when he passed the testing platform. Instead, he sat down on the cot, pulled the toolbox out from under the cot, and confirmed that the latch was still in place.

At the very bottom of the metal box, kraft paper notes and electron microscope photographs were stacked together.

The 2.95 gigahertz that Fang Xudong calculated in the confidential cubicle this afternoon was less than one percent off from the number he had written down in his notes long ago.

The type B tube still needs 30 hours to reach 500 km/h.

According to the procedure, the next steps are acceptance, delivery, and case closure.

Jiang Ming stared at the lock on the toolbox for a while, but still didn't immediately push the box back under the bed.

Xu Chongwen's side has been quiet for too long.

It was so quiet it didn't seem like nothing was wrong; it was more like they were waiting for the right moment.