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

When Jiang Ming returned to his dormitory, most of the lights in the corridor were already off.

Beside the iron-framed bed, a few pages of psychic notes lay open on the pillow, the corners of the paper rustling softly in the cold wind blowing through the window cracks.

He pressed the telegram down next to his notebook, his gaze fixed on the last question.

The bitterness that had arisen in the confidential room during the day had now subsided, leaving only a clear line.

Lu Qinghe sees the scene firsthand, and the solutions he proposes must also be applicable to the scene.

He sat on the edge of the bed, spread the telegram on his lap, and pressed the tip of his pencil against a blank space to break down the problem.

First, the false orientation caused by reflections from the mountain is difficult to distinguish using single-point orientation measurement.

Second, if two direction finding points are simultaneously affected by reflection after they intersect, the intersection point will still deviate.

Third, the Northwest lacked sophisticated instruments, so the communication team had to rely solely on notebooks and pencils.

After writing down the three questions, he closed his eyes and let his consciousness sink into the study space of Tongtianlu.

In his first psychic encounter, he found the pioneers of vacuum tubes and radar.

"How can we distinguish between direct sunlight and reflected light, which can cause false orientations due to reflections from the mountain?"

Pioneer immediately berated him, saying that this was the most basic multipath problem in the radar field, and that he, a pipe engineer, was asking this question—had he lost his mind?

After the rant, the other party still provided crucial guidance.

"There is a time difference between reflected and direct signals. Shortwave travels at a fixed speed in the air. If the signal hits the mountain first and then bounces back, the path is longer than that of a direct signal. As long as the energy exceeds this time difference, we can distinguish which is real and which is fake."

How big is the time difference?

"It depends on the extra distance in the reflection path. The mountain is 300 meters away from the receiving point, which adds 600 meters to the round trip path, resulting in a time difference of about two microseconds."

"Two microseconds."

Jiang Ming repeated the number in his mind.

The manual recording equipment of 1955 could not distinguish a time difference of two microseconds.

The pioneer seemed to see through his predicament.

"Don't expect to measure the time difference; you don't have the equipment. Think of it another way: the intensity of a reflected signal is definitely weaker than that of a direct beam because a mountain isn't a mirror, and scattering will absorb a lot of energy. If you measure the signal intensity of the same pulse at different points, the point where you receive the strongest signal and the direction that is most stable is more likely to be the direction of the direct beam."

During his second psychic encounter, he found a female pioneer in precision instruments and vacuum systems.

"In two-point intersection direction finding, both points are affected by reflection interference. How can we rule out false intersections?"

Her answer was calm and direct.

"Add a third point. When using three points for orientation, if the three azimuth lines intersect in the same area, accidental reflections can be largely ruled out. If only two lines intersect at one point, and the third line deviates significantly, it means that the deviated line is being reflected, and it should be discarded."

Is there any particular significance to the location of the third spot?

"Keep the third point away from any known reflector. If you know the mountain is to the east, place the third point to the west on open terrain so that it receives as few direct signals as possible. This way, the azimuth of the third point will be the cleanest and can be used as a calibration reference."

During his third psychic encounter, he returned to his fellow physics students in the Materials Interface and asked a seemingly unrelated question.

How much do surface humidity and mineral composition affect reflectivity when shortwave signals propagate across the ground?

The younger students answered very quickly.

"Dry sandy and gravelly surfaces have low reflectivity, causing signals to attenuate after penetration. Moist clay or iron-bearing ore surfaces have high reflectivity. If there are dried-up riverbeds or exposed ore areas in Northwest China, those are natural reflective surfaces, making them more dangerous than pure sandy deserts."

Jiang Ming remembered this.

The terrain of Northwest China is not only mountainous, but also includes dry river valleys and mineral belts.

On the topographic map drawn by Lu Qinghe, those shaded areas may not all be differences in elevation, but may also include surface reflective hotspots.

During his fourth psychic encounter, he used the historical fragment search function to search for historical events related to early shortwave direction finding.

The image was blurry and brief.

In a simple communications room, hand-drawn maps were pasted on the walls, and several people in gray military uniforms were gathered around a rotating antenna.

One of them used a pencil to draw intersecting lines on the map, with the signal strength numbers for different times marked next to them.

The methods they used were very primitive.

The intensity changes of the same signal at different times are plotted as curves. The direction in which the intensity remains stable is direct radiation, and the direction in which the intensity fluctuates with time is reflection or scattering.

A system notification appears.

The historical fragments are derived from the horizontal extension and peripheral connections of the context, and are provided for background reference only.

During the fifth psychic encounter, Jiang Ming combined the information from the previous four encounters and asked the female pioneer one last question.

"How can these methods be written into operational procedures that can be implemented in Northwest China, without any sophisticated instruments, relying solely on manual recording and pencils?"

She provided a framework.

"Each time a pulse occurs, the azimuth and signal strength are recorded simultaneously at three points. Recording is done continuously for ten minutes to see which direction has the most stable intensity. The stable direction is the direct direction or the direction closest to the direct direction. Unstable directions are discarded. The most stable azimuth line is retained at each of the three points, and the intersection of these lines gives the target area."

Five psychic sessions have been used up.

Jiang Ming opened his eyes and spent half an hour in the dim light condensing all the information into six key operational points.

He removed the formulas and complex diagrams, keeping only the execution instructions that the communication group could easily follow.

The first rule is to select three direction finding points, with a distance of no less than 800 meters between them. The third point must be far away from known mountains and areas with exposed ore.

Secondly, each time an abnormal pulse occurs, the azimuth angle of the loop antenna null point is recorded simultaneously at three points, accurate to the degree.

Article 3: Each recording lasts for ten minutes, and the signal strength level is marked for each pulse, divided into three levels: strong, medium, and weak.

Article 4: After the ten-minute recording period ends, discard azimuth data with intensity fluctuations exceeding one level, and retain only azimuth lines with stable intensity.

Fifthly, the intersection of three stable azimuth lines represents the most likely direction of direct sunlight. If only two lines intersect, and the third line deviates too much, then the third line is discarded.

Article 6. Repeat the above process for three consecutive days at different time periods. If the intersection area remains stable, the target direction is confirmed.

After daybreak, Jiang Ming rushed to Workshop No. 1 and handed the six items to Xiao Zhao.

"Please compress this into a telegram format, with each message not exceeding twenty characters. Add a sentence at the beginning: 'Thank you for the feedback. The single-point solution is insufficient; we are adopting a combination of two or more points, as supplemented below.'"

After reading the six items, Xiao Zhao opened his mouth slightly and then pushed up his glasses.

"Jiang, are you teaching them how to locate enemy radio stations?"

"I'm just saying the optimal operating environment for the tube when it works with the antenna in a direction-finding receiver."

Jiang Ming remained unfazed.

Xiao Zhao glanced at him, then lowered his head and began to copy.

The telegram was sent at noon that day.

Two days later, at the Northwest Base.

Lu Qinghe stood in front of the long table in the communications room, holding the reply telegram from Beijing in his hand, reading it from beginning to end, and then flipping back to the end.

Chen Zhiyuan sat opposite her, observing her expression.

"He admitted that individual points were not enough."

Lu Qinghe put down the telegram, her voice completely flat and even.

"Moreover, these six additional points are not just empty talk."

She pointed to the fourth one with her fingertip.

"He eliminated azimuth data with intensity fluctuations exceeding one level. This shows that he knew reflected signals were unstable, while direct signals were stable. I spent forty days in the south summarizing this criterion, while he figured it out sitting in Beijing."

Chen Zhiyuan did not take credit for Jiang Ming, but only said one sentence.

"He's always been like this; he can listen to what others say, and he can also think deeply about it himself."

Lu Qinghe didn't reply, but folded the telegram and tucked it into her notebook.

"I'll go choose where to put the third spot this afternoon."

She turned and walked towards the door.

"Chen Zhiyuan, you're in charge of the tubes and receiver; the equipment is your responsibility. The terrain and antenna are mine."

"OK."

That afternoon, Lu Qinghe left the base with a young technician carrying a canvas bag and walked two kilometers west.

She chose a dry ditch mouth.

The area is open on three sides, with only a low earthen embankment on the south side to block the wind. The view is clear, and it is far away from the mountains to the east and the mineral belt to the north.

She squatted on the ground, dug a shallow pit in the frozen soil with a shovel, drove in three iron nails to fix the antenna bracket base, and checked it three times with a level.

It was already dark when we got back to base.

She ran into Chen Zhiyuan at the entrance of the communications room.

The latter was coming out of there, holding the notebook from tube number A01.

"The coaxial cables for the two old sites in the north and south and the new site in the west are all connected. We can test them tonight."

Lu Qinghe nodded, went into the communications room, and marked the coordinates and azimuth baselines of the three points on the topographic map.

At 11:42 p.m., the abnormal pulse reappeared.

The duty officers at the three locations simultaneously recorded the azimuth and signal strength.

North Point reports 317 degrees, moderate to strong.

South Point reports 322 degrees, moderate to strong.

The newly established third point in the west reports 341 degrees, strong.

The recording ended ten minutes later.

Lu Qinghe plotted the three sets of data on the topographic map.

The azimuth lines of the north and south points intersect in a vast, open Gobi desert to the northeast, almost identical to the false azimuth determined last month.

However, the azimuth line of the third point to the west does not pass through that Gobi Desert.

It points northeast of east, deviating by nearly twenty degrees from the previous two lines, and plunges directly into another area.

The three lines do not intersect at the same point.