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

Chen Zhiyuan pressed the intelligence telegram newspaper into the bottom of his notebook, lingered on the string of numbers for five seconds, and then stood up.

"I'm not going to sleep. I'll take over the machine and start testing as soon as it's light."

Lu Qinghe nodded in response, and the wooden house returned to silence, with only the occasional crackling sound of the kerosene lamp wick.

The three men leaned back in their chairs and closed their eyes to rest. The twelve-times-increase-frequency incline over six hours indicated that the enemy station was wrapping up some operation.

The window of opportunity left for them has been compressed to the extreme.

As dawn broke, the wind subsided, and the snow on the Gobi Desert shimmered dazzlingly white in the sunlight.

Chen Zhiyuan and Lu Qinghe moved the delay line device to the equipment rack next to the receiving antenna and used wire to firmly fix the wooden frame to the crossbeam to prevent wind damage.

The mixer output is connected to the intermediate frequency output port of the Soviet-made shortwave receiver via a short coaxial jumper, thus completing the entire signal link.

Old Zhou set up an oscilloscope he had borrowed from the command post, and after the cathode ray tube had been preheated for ten minutes, a green spot of light appeared.

"Wait for the enemy's position to arrive."

At 10:03 a.m., the first pulse was initiated precisely on time.

A sharp pulse peak appeared on the oscilloscope's time base scan line, and the waveform, about 0.3 seconds wide, occupied most of the screen.

Fifteen seconds later, a second pulse followed immediately, with identical waveform characteristics.

Chen Zhiyuan stared intently at the oscilloscope screen; the output amplitude after delay line processing had indeed decreased.

He used a pencil to mark the positions of the original amplitude reference line and the current residual amplitude on the edge of the screen, and quickly estimated the ratio in his mind.

"It's decreased by about 40%."

Forty percent cancellation means that sixty percent of the interference still remains in the signal, and the false azimuth line will still overwhelm the real data.

Jiang Ming's annotation on the back of the drawing requires that the residual amplitude must be reduced to less than 10% of the original signal, and the current cancellation rate is far from meeting the standard.

Lu Qinghe walked around the back of the equipment rack to the front of the oscilloscope.

"Is there a loose solder joint?"

"You tested the insulation and continuity of each solder joint last night, so it can't be a cold solder joint."

"Then check the cable length."

Chen Zhiyuan took out a steel measuring tape, untied the two sections of cable from the wooden frame, straightened them, and remeasured and compared them.

The error between the main line (7.42 meters) and the secondary line (4.68 meters) is controlled within half a centimeter, and the calculated phase error is less than two degrees, which could not possibly cause such a huge cancellation loss.

Lu Qinghe squatted down next to the secondary cable, the beam of her flashlight slowly moving along the outer sheath of the cable, finally stopping at the spot where the candle wax had been repaired.

She reached out and touched the area wrapped in the cotton strip; the wax layer that had solidified at low temperatures felt hard to the touch.

What is the dielectric constant of this original rubber insulation layer?

Chen Zhiyuan opened the technical specifications of the Soviet-made cables and looked up the Russian parameter table.

"Nominal 3.0".

"Where's the wax?"

Chen Zhiyuan retrieved data from his university physics textbook in his mind: the dielectric constants of beeswax and paraffin are between 2.2 and 2.5.

The dielectric constant of the two-centimeter insulation layer drops from 3.0 to about 2.3, and the increased propagation speed of electromagnetic waves leads to a shortening of the equivalent electrical length.

He squatted on the ground and quickly wrote down the formula with a pencil. The equivalent electrical length deviation caused by the two-centimeter length difference was about 0.8 centimeters.

At the current frequency, a phase shift of 0.8 centimeters corresponds to a phase shift of nearly 15 degrees. The overall phase delay deviation of the sub-line means that the superposition cannot achieve 180-degree cancellation.

The root cause of the problem has been identified, but the precise calculation of the correction amount is beyond Chen Zhiyuan's grasp.

Adjustable capacitors can compensate for phase deviations, but the specific compensation value involves the matching relationship between the capacitor's equivalent reactance in a specific frequency band and the characteristic impedance of the cable.

"Call up."

Old Zhou quickly dialed the main switchboard of the base's communications command post, and was transferred to the administration building of the Third Electronics Factory via a confidential line from the First Ministry of Machine Building in Beijing.

The three-level transfer took twelve minutes, and the duty officer in the administration building spent another five minutes going to Workshop No. 1 to find someone.

When Jiang Ming answered the phone, his voice was hoarse, as if he hadn't woken up yet.

"Comrade Jiang Ming, the delay line is connected, but the phase difference is not aligned. Two centimeters of insulation on the secondary line is damaged and has been repaired with wax. The dielectric constant has changed from 3.0 to about 2.3, and the equivalent electrical length has shrunk by about 0.8 centimeters. The phase deviation is estimated to be 15 degrees, which needs to be compensated on the adjustable capacitor, but I cannot calculate the amount of compensation accurately."

The faint sound of papers turning over could be heard from the other end of the phone.

What is the original characteristic impedance of the secondary cable?

"The technical brochure indicates a strength of fifty-two ohms."

"The range of the adjustable capacitor?"

"From five to thirty-five leather fingers, the moving piece is fully screwed in at thirty-five."

"What setting is the capacitor on the secondary circuit currently at?"

Chen Zhiyuan turned to look at the gestures Old Zhou was making.

"Approximately 12.5 pi, set according to the initial values ​​on the drawings."

There was a nearly two-minute silence on the other end of the phone, with the soft, continuous sound of a pencil scratching on paper.

"When you adjust it to 14.2 picofarads, the 0.8 cm equivalent electrical length shortening corresponds to a phase difference that, under the condition of a 52-ohm characteristic impedance, is equivalent to increasing the capacitive reactance by 1.7 picofarads in series. If you turn the adjustable capacitor from 12.5 to 14.2, the moving plate will be turned in about one-third more turns."

Chen Zhiyuan wrote down 14.2 in his notebook and repeated it to confirm.

"If the wax layer of the repair section softens due to the increased temperature from sunlight during the day, it will cause the dielectric constant to drift. After you finish adjusting it, remember the current position and angle of the moving plate. If the residual signal becomes stronger again in the afternoon, try turning it back one degree."

"clear."

"quick."

The dial tone indicating a line cut echoed in the receiver.

Lu Qinghe took over the adjustment task, and the knob of the adjustable capacitor was stiff to turn in the sub-zero temperature.

She used her fingertips to feel the mechanical resistance of the moving plate, stopping after each small rotation to check the reading on the microammeter.

She rotated through the 12.5 to 14.2 scale in four steps to get into position.

At 10:20, the next group of enemy pulses switched in precisely on time.

After a brief jump, the oscilloscope scan line returned to a steady state, with the residual pulse amplitude suppressed to within one-twelfth of the original reference line.

Lu Qinghe leaned closer to the screen and observed for three seconds. Fifteen seconds later, the residual amplitudes of the second and third groups of pulses were consistent.

Chen Zhiyuan used a pencil to mark the new scale next to the reference line and roughly calculated the proportion.

"Below eight percent".

Old Zhou let out a long sigh and placed the screwdriver he had been clutching tightly on the table.

Chen Zhiyuan dialed back to the Beijing line, which took six minutes to connect to the duty room of the Third Electronics Factory.

"Tell Comrade Jiang Ming, it's done."

Lu Qinghe began adjusting the receiver gain settings, preparing to re-record the azimuth data using the new signal-to-noise ratio.

She reinforced the wooden frame of the delay line with wire and drew alignment lines on the adjustable capacitor knob with white paint to prevent it from shifting in the wind.

When the midday sun shines directly south, all three sets of synchronous azimuth data are collected.

Lu Qinghe laid the 1:5000 military map flat on the wooden table and used a set square and protractor to draw azimuth lines from three directional points.

The three straight lines converge on the map, eventually intersecting within the area she circled with a red pencil.

The center of the circle, with a diameter of less than 800 meters, landed directly beside the low-lying dry riverbed at the eastern entrance of the abandoned camel trail.