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

The daytime questioning was more detailed than Jiang Ming had anticipated.

Fang Xudong stared at the pulse magnetic saturation design memorandum, asking questions about everything from the cross-sectional area of ​​the iron core to the grain size, and from eddy current loss to temperature drift compensation; Wu Hanzhang, on the other hand, flipped to page thirty-seven of Ivanov's notebook and studied the copper-tungsten alloy melting temperature curve for a long time.

Jiang Ming laid out the three sources he had prepared the night before: the damping correction term came from the equivalent analogy of the melting curve, the temperature compensation coefficient came from the extension of the homework questions in Qian Xuesen's thermodynamics and statistics textbook, and the relationship between grain size and eddy current loss was deduced from the high-temperature section data of Yuanlei No. 1 exhaust furnace.

This explanation wasn't foolproof, but it was enough to shift Fang Xudong's focus from "how do you know?" to "can it be done?"

At 10 p.m., the iron door of Laboratory 502 was locked from the inside.

Old Sun dragged a Soviet medium-wave radio transmitter power box, which he had pulled out from deep inside the warehouse, onto the worktable. The metal casing was rusted black, and two of the four fixing bolts were completely stuck in their holes.

When Jiang Ming used a screwdriver to pry open the back cover from the side, a smell of transformer oil mixed with burnt insulating varnish wafted out.

The wiring inside was a tangled mess, and the aluminum casings of the electrolytic capacitors were covered in white alkaline spots.

"Yuanlei-1 can ignite and emit microwaves, but without a pulse modulator, it's just burning like a light bulb. Sending it to the front lines wouldn't be of any use." Jiang Ming scanned the layout inside the power supply box, his finger stopping on a large glass-cased tube in the upper right corner. "This is a hydrogen-filling thyratron, model ТГИ1 series, rated anode voltage of 15,000 volts, and pulse peak current exceeding 200 amperes."

Old Sun came over to take a look. The thyristor was a size larger than an adult's fist. The glass outer wall was light purple, and there were three pins on the bottom of the tube socket, one of which was obviously blackened and deformed.

"It's burning out." Old Sun said, shining his flashlight inside the pipe. There was no surprise in his tone; he was simply stating a fact.

Jiang Ming pulled the tube off the tube holder and examined the deposited layer on the inside of the glass wall from various angles under the light. After turning it twice, he put it back on the table and drew a cross-sectional diagram on the draft paper with a pencil.

"The oxide layer on the surface of the molybdenum grid of the ignition electrode is too thick, which causes the trigger voltage to rise. However, the hydrogen pressure inside the tube is still within the normal range, and there are no signs of leakage in the glass wall. If part of the oxide layer on the surface of the molybdenum grid can be removed to reduce the work function, this tube can still be used."

Old Sun had already taken out the set of miniature sandpaper strips he had made himself from his toolbox. They were less than three millimeters wide and about four centimeters long, and he usually used them when doing fine-tuning of the grids of electron tubes.

"Put it in through the exhaust pipe?"

"Yes, you enter from the exhaust tailpipe at the top, and use a strip of sandpaper to slide down along the inner wall of the screen. Once you reach the ignition grid, sand it horizontally, only half a millimeter at a time, so as not to break the molybdenum wire."

Old Sun put on his magnifying glasses, used a cork block to stabilize the thyratron in the fixture on the table, held the tube in place with his left hand, and pinched the thin, translucent sandpaper in his right hand, pushing it little by little into the exhaust tailpipe.

Fang Xudong stood diagonally opposite the worktable, his hands in his cotton-padded jacket pockets, watching the process without saying a word.

Without waiting for Lao Sun to finish, Jiang Ming turned around and spread out a grid paper on another table. He began to draw the circuit diagram of the pulse forming network. The pencil tip moved quickly across the paper, marking the capacitance and voltage rating of the three sets of parallel mica capacitors, and writing the number of turns and core cross-sectional area of ​​the charging inductor next to them.

The magnetic saturation correction coefficient obtained from Bogdanov's psychic communication last night has now been converted into a safe boundary value for the maximum magnetic flux density of the iron core. It is written in the box in the lower right corner of the circuit diagram, with the source marked as the equivalent analogy derivation of the copper-tungsten alloy melting temperature curve on page 37 of Ivanov's notebook.

"The core of the pulse transformer is made of stacked silicon steel sheets, and the cross-sectional area cannot be less than four square centimeters. Otherwise, the leading edge of the square wave with a pulse width of two microseconds will collapse due to core saturation." He said to Fang Xudong while drawing. "The eddy current contribution factor mentioned in Bogdanov's domain wall damping correction formula in 1947, when converted to the grain size of the silicon steel sheets we have, means that the maximum working magnetic flux density of the core cannot exceed 1.2 Tesla, leaving a 15% margin."

Fang Xudong walked over to look at the blueprints, his finger pointing to the three sets of capacitors in the charging and discharging network.

"Three sets in parallel? What is the total capacity?"

"Each group consists of three 0.02 microfarad mica capacitors connected in series and then in parallel, with an equivalent total capacitance of approximately 0.02 microfarads. The charging voltage is 12,000 kPa, and the pulse impedance is matched to the on-state voltage drop of the thyristor plus the impedance of the magnetron."

Fang Xudong did the calculations, nodded, and didn't ask any more questions.

Da Liu brought a metal square barrel from the warehouse next door. It was filled with more than half a barrel of transformer oil, which was slightly yellow in color and covered with a layer of fine dust. After filtering it twice with a funnel and gauze, he immersed the entire wound pulse transformer core into the oil, allowing the insulating oil to seep into the gaps between the silicon steel sheets to prevent high-voltage breakdown.

It took Lao Sun nearly forty minutes to finish polishing. When he pulled out the sandpaper strip, the surface was covered with a layer of blackish-gray powder. He turned the tube over and tapped it a few times to let the debris fall out of the exhaust pipe. Then he used a magnifying glass to check the inside again.

"It's been ground clean, the molybdenum wire isn't broken, and the grid shape is still there."

Jiang Ming took the tube and reinstalled it on the modified tube socket. The entire pulse modulator circuit was now connected on the workbench: on the left was a high-voltage rectifier filter, in the middle was a pulse forming line composed of a charging inductor and three sets of mica capacitors, and on the right was a thyristor and a pulse transformer. The secondary output of the transformer was connected to two thick copper wires, which led directly to the anode of the Yuanlei No. 1 magnetron on the adjacent table.

When the circuit was closed for charging for the first time, the high voltage meter pointer slowly climbed to 8,000 volts. Jiang Ming pressed the trigger button, and a blue-purple arc flashed inside the thyristor, but there was no output from the secondary side of the pulse transformer, and only a distorted spike appeared on the oscilloscope screen.

"The trigger timing is incorrect; it discharged before the charging was complete." Jiang Ming adjusted the RC time constant of the trigger delay circuit, increasing the delay from the original 800 microseconds to 1200 microseconds.

When the circuit was closed for the second time, the high voltage meter was triggered when it reached 11,000 volts. The arc flashed again, and this time a pulse with an approximate square wave appeared on the oscilloscope, but there was a noticeable drop at the top, and the amplitude dropped by nearly 15 percent from the peak value to the end.

"The iron core is starting to saturate," Fang Xudong said, pointing to the waveform.

Jiang Ming glanced at the time axis scale of the waveform. The pulse width was already close to two microseconds. The problem was that the cross-sectional area of ​​the iron core was too small, causing the magnetic flux density to exceed the safety boundary. He asked Da Liu to go to the warehouse to find four more silicon steel sheets of the same specification to add to the stack, increasing the cross-sectional area from 3.6 square centimeters to 4.3 square centimeters.

While disassembling the iron core clamp, Lao Sun's hand was cut by the rough edge of the glass shell of the thyristor. Blood immediately seeped from the wound. He glanced at it, pulled a piece of white tape from his pocket, wrapped it around the wound twice, pressed it down, and then continued to tighten the screws.

Fang Xudong looked at Lao Sun's hand wrapped in tape, opened his mouth slightly, but didn't say anything.

After the iron core was thickened and re-oiled, it was charged to 12,000 volts for the third time, and Jiang Ming pressed the trigger.

A stable purple-blue glow illuminated inside the thyristor, the pulse transformer emitted a muffled hum, and a clean square pulse appeared on the oscilloscope screen, with a steep leading edge, a flat top, a pulse width of exactly two microseconds, an amplitude of 12,000 volts, and a clean trailing edge returning to zero.

Jiang Ming adjusted the repetition frequency from single trigger to continuous operation at 1 kilohertz. The square wave pulses lined up in a neat vertical line on the screen, with consistent amplitude and uniform intervals, without any jitter or drift.

"Modemer passed." He wrote the data down in his notebook, and when he closed the pen, his fingers still felt the heat of the solder.

Fang Xudong stared at the oscilloscope for a long time, then turned to Lao Sun and said, "Aren't you going to get that cut on your hand bandaged?"

Old Sun put his hand, which was wrapped in tape, behind his back and chuckled, "It's much lighter than the iron filings flying around in the workshop, it's no problem."

Fang Xudong didn't say anything more. He shifted his gaze back to the square wave pulses on the oscilloscope screen, blinked twice, and then nodded slightly.

A gust of wind picked up in the courtyard outside Workshop No. 1, rattling the corrugated iron roof. Jiang Ming was preparing to conduct a joint ignition test on the modulator and Source Thunder No. 1 when hurried footsteps came from the other end of the corridor. When the crew-cut officer pushed open the iron door, he was holding a folded telegram in his hand, and his expression was not the calm one he usually wore when on duty.

"Urgent telegram from the Northwest, arrived at the confidential office ten minutes ago."

Jiang Ming took the telegram and unfolded it. The first line of text made him stop unbuttoning his clothes.

The frequency interference power in the direction of Mine No. 04 suddenly increased to three times the original level, with the peak estimated to exceed three kilowatts. The coverage frequency band expanded to 4.8 to 5.6 MHz on both sides. The border patrol team has been cut off from all communication for more than seventy-two hours. The encirclement force is in danger of being counter-encircled. The front-line command post requests immediate support.

Old Sun read something from Jiang Ming's expression, put down the screwdriver in his hand, and stood up straight.

Fang Xudong also came over to take a look. After he finished looking at it, he looked up at Jiang Ming. Their eyes met briefly in the green reflection on the oscilloscope screen, but neither of them spoke.

The planned joint ignition test was thus halted.

Jiang Ming turned the trigger power knob back to the zero position, and Lao Sun pulled down the main switch. The neat row of square waves on the oscilloscope screen slowly shrank into a thin dark green line.

The wind was still blowing outside the iron gate, and the crew-cut clerk had already turned around to inform the factory management.

That night, the lights in Lab 502 remained on.

Yuanlei-1 had just completed pulse modulation, but there was no time left to slowly break it in on the test bench.

Before dawn, the telegram sent from the Northwest was delivered to the factory's conference room.