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

The white noise was a level higher than before, so Lu Qinghe quickly lowered the headphone gain. The meter pointer still went over the full scale and bounced back and forth on the mechanical stop.

"The power has recovered and is still increasing, reaching 10% higher than when the main oscillator was operating."

The calls between the various units that had just been restored were cut off by noise, the command channel was reduced to broken syllables, and the report from the No. 3 radar base disappeared completely halfway through.

Fang Xudong rushed to the spectrum monitor, scanned a complete frequency band, and picked up a pencil to record the pulse intervals.

"The switching time is 20 seconds, the frequency control is locked again, and there is no restart delay in the power amplifier stage."

He unplugged the listening cable and connected the reference pulse returning from the mine to the external trigger terminal of the oscilloscope. Two sets of synchronization signals with different amplitudes quickly appeared on the screen.

The first set of residual signals is decaying, while the second set has already taken over, with the interval between the two being exactly twenty seconds.

"Cold standby dual local oscillators".

Lu Qinghe turned to look at him.

"What do you mean?"

"Two isolated frequency references were installed in the mine. The main local oscillator was responsible for normal operation, while the backup local oscillator was always disconnected from the output, only maintaining low power and constant temperature."

Fang Xudong pointed to the first set of waveforms on the screen, which was still weakening.

"After the Yuanlei No. 1 burned through the main local oscillator protection stage, the monitoring circuit confirmed the loss of lockout, the mechanical relay cut off the main circuit, and then the cold standby was connected to the sweep frequency controller."

"Twenty seconds is the time for relay switching and backup crystal heating."

"Yes, the backup local oscillator was not connected to the antenna circuit and was not subjected to pulse impact, so it survived."

Fang Xudong picked up the frequency projection paper from the shockproof box during the first ignition and crossed out the local oscillator coupling frequency point that had been circled.

"The main road is now useless. The intermediate frequency architecture and coupling parameters of the backup road have all changed. The spot that Source Thunder No. 1 hit just now only has a broken line connected."

Old Sun walked to the feeder and touched the connector, which was still warm.

"Find a new spot and try the same method again."

"Can't find it."

Fang Xudong spread out the frequency spectrum diagram of the mine shaft, and moved the pencil along the newly appeared frequency hopping trajectory.

"Yuanlei-1 can only operate at a fixed frequency of 2.952 GHz. We were able to deduce the coupling relationship of the main oscillator by using the mixer board we captured."

"The spare local oscillator is hidden in the mine. We have no data what kind of crystal it uses, how many times it has been frequency-doubled, or which port it is connected to."

Old Sun withdrew his hand from the feeder connector.

"Then disassemble the pipes and change the frequency."

"The anode resonant cavity is fixed, and there are no machine tools available on site, so it cannot be modified."

After Fang Xudong finished speaking, he looked at the oscilloscope. The bright band that had just recovered expanded to both sides again, and the new frequency band coverage speed was much higher than that of the main system.

The first ignition at least proves that Yuanlei-1 is capable of crossing the sand dunes.

The second successful breakdown of the main oscillator further proves the effectiveness of the fixed-frequency pulse countermeasure scheme proposed by Jiang Ming.

However, the enemy used a pre-hidden backup system to simultaneously eliminate both breakthroughs.

The Source Thunder One is still intact, the pulse modulator is not damaged, and all equipment readings are within the normal range. The only thing missing is the target port that can be attacked.

Several short calls came through the walkie-talkie. The First Battalion was advancing in the North Gully, and the vanguard had already crossed the first fork in the road.

After the interference was restored, their communication with the rear was interrupted again, and the Second Battalion was also stopped at the mouth of the ditch on the west side, unable to confirm the current position of the First Battalion.

Director Wang's voice squeezed out from the gaps in the noise.

"Mound, report: Has the enemy watchtower been reactivated?"

Lu Qinghe moved the transmission frequency to a location on the edge where interference was weaker.

"Recovery confirmed. The enemy has activated a cold backup frequency reference. The current power is 10 percent higher than before. The original attack frequency is no longer valid."

"Can we play one more time?"

She looked at Jiang Ming.

Jiang Ming took off his military overcoat, opened the lapel, and hung it between the shockproof box and the antenna bracket to block the wind blowing in his face.

Then I took out graph paper and a pencil, and pinned the paper to the side of the box with thumbtacks.

"Give me the new frequency hopping data first."

Lu Qinghe pressed the call button.

"Re-intercepting, will take a few minutes."

I heard the sound of a map ruler hitting the table from Director Wang's end.

"The First and Second Battalions have entered the trench and must rendezvous in forty minutes, otherwise the spies in the mine will seize the central high ground."

"After losing communication, the two teams could not confirm each other's positions, and the artillery dared not fire. The mound had to restore the channel within forty minutes."

After the call ended, Jiang Ming glanced at his watch.

00:21.

There are 39 minutes left until the originally scheduled deadline of 1 a.m.

Inside the mine's listening room, the constant temperature bath for the backup local oscillator had reached its rated temperature, and the three power amplifiers were locked back into sweep frequency control.

The technical supervisor wiped the sweat from his forehead with a handkerchief and threw the charred main oscillator protection board into the iron pan.

The pulse that just fell along the inversion layer has already damaged three diodes and one phase detector. If it had continued for a few more seconds, the main oscillator power supply would have burned out.

The cold backup circuit left in the initial design saved the entire system.

"Backup codebook loading complete, main codebook deactivated."

The operator pushes the main output switch, and the anode current rises to the new scale.

"The transmitter outside is still in the same position, and the frequency hasn't changed."

"They only brought one card."

The technical supervisor locked the new codebook in a metal cabinet.

"Let them take the main oscillator, and switch to full power for the backup system. First, cut off communication between Beigou and Xigou."

The antenna array outside the mine changed its feeding sequence, causing the interference beams to deflect towards the two trenches where the encircling troops were located.

Inside the listening vehicle on the mound, Lu Qinghe placed both hands back on the tuning knobs, first moving the scan start point to 4.8 MHz, and then reducing the scan speed to half of its original value.

"The first one, 4.93 MHz, stays for seven seconds."

Jiang Ming wrote 4.93 at the top of the graph paper.

"The second one, 5.48 MHz, stays for four seconds."

The two points differ by 0.55 MHz, exceeding the normal span of a single step in the old golden ratio sequence.

"The third one, 5.07 MHz, stays for twelve seconds."

Jiang Ming calculated the adjacent differences and converted them into offset ratios relative to the 4.8 MHz base. There were no common factors among the three results.

"The fourth one, 5.39 MHz, stays for five seconds."

Lu Qinghe rotated the matching capacitor, and a piercing whistling sound came from the headphones. She pulled the frequency down by two kilohertz before she could regain the signal center.

"The fifth one, 4.86 MHz, stayed for nine seconds."

The five frequency points are listed in a column.

4.93, 5.48, 5.07, 5.39, 4.86.

The jump directions alternate, with amplitudes ranging from 0.13 to 0.55 MHz, and dwell times varying between four and twelve seconds.

Jiang Ming wrote the old golden ratio step formula next to it, and after substituting it into the first frequency point, the prediction result differed from the second frequency point by 170 kilohertz.

He switched to linear congruent sequences, discretizing the frequency band into eighty 10 kHz channels, but the resulting state transition still could not cover the third frequency point.

The two sets of formulas on the paper were crossed out with horizontal lines.

"It is not a re-seed version of the old codebook."

Fang Xudong also arranged the frequency points on another piece of paper.

"The backup system uses a different frequency hopping logic, and the frequency and dwell time may be controlled by two separate sequences."

"It's also possible to use the noise sample from the previous moment as input."

Before Lu Qinghe reported the sixth frequency, the receiver was already covered by broadband noise, and the knob was swung back and forth twice without being able to re-acquire it.

"It's lost. I didn't catch it on the sixth jump."

Jiang Ming stared at the five sets of numbers on the paper.

Although the golden ratio sequence is complex, its underlying structure is still a fixed irrational number step. As long as enough frequency points are obtained, the seed can be deduced.

The new codebook did not retain this continuity.

The frequency span, dwell time, and jump direction all exhibit a white noise distribution, and no verifiable recursive relationship can be found among the five data points.

Two coughs came from the back slope of the generator, the speed dropped a bit, and the oil pressure gauge needle crossed the yellow area and began to approach the red line.

Old Sun ran over to refuel, and when he came back, his trousers were covered in diesel fuel.

"How much longer can we hold out?"

"Full load lasts 35 minutes, reducing power slightly can extend it by 10 minutes, but now we don't even know where to hit."

Lu Qinghe once again detected the enemy's radio frequency.

"The sixth one, 5.22 MHz, the dwell time is still being calculated."

Jiang Ming wrote down the numbers, breaking the last usable correspondence in the old formula.

Fang Xudong took off his glasses, wiped the sand off the lenses with the corner of his clothes, and put them back on. By then, the mine interference had filled the entire screen.

"They knew the main codebook was exposed, so they even changed the mathematical model of the backup system."

"Cold standby, local oscillator isolation, independent new codebook, all three layers were prepared in advance. The designers of this equipment were prepared to defend against anti-radiation attacks from the very beginning."

"This means he knew someone would hit like that."

Jiang Ming turned the pencil over and used the eraser at the end to erase the last row of the golden ratio sequence.

Only six frequency points and constantly changing dwell times remain on the graph paper.

Two faint flashes of gunfire appeared in the distant ditch, separated by a few seconds, before being obscured by darkness again.

The First Battalion of Beigou and the Second Battalion of Xigou could no longer confirm each other's positions. The mine guards could simply move along the central high ground to separate and deal with the two teams.

Lu Qinghe pressed the earphone and continued searching for the seventh frequency.

Jiang Ming glanced at his watch.

00:22.

There are 38 minutes remaining before the encircling forces must restore communication.