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

Chen Zhiyuan temporarily stopped pushing the frequency.

He fixed the knob in its current position, picked up a pencil, and drew a vertical bar on the recording paper.

He drew a line for each jump of the clutter.

Ten minutes later, nineteen vertical bars were laid out on the paper, with intervals ranging from twenty-eight to thirty-three seconds, generally fluctuating around thirty seconds.

The tube's own emission current remained stable, and the microammeter remained at 272 during the fluctuation interval, indicating that the interference was still at the peripheral coupling level and had not penetrated the anti-interference circuit.

"Old Zhou, how does the old pipe react when it encounters this kind of noise?"

Old Zhou stood up, walked to the testing table, glanced at the dial, and then looked at the vertical bar on the recording paper.

"When old tubes are pushed to this frequency band, the transmission current will drop precipitously to below 150 within three minutes, and they will be basically unusable after five minutes."

As he spoke, he reached out and pressed down.

"It collapsed completely, like a deflated balloon."

Chen Zhiyuan drew a horizontal line on the record sheet and marked it: "Stable for ten minutes, no decay".

Pipe No. 01 stopped.

In a frequency band where old pipes would collapse in three minutes, this pipe, transported from Beijing by rail over thousands of kilometers, ran for ten minutes without losing current.

Chen Zhiyuan remained calm, closed his notebook, tucked it under his arm, and turned to sit down next to the telegraph machine in the communications room.

"Send a telegram back to Beijing, reporting the data from those ten minutes exactly as it was."

On the same day, at the Third Electronics Factory in the suburbs of Beijing, in a single dormitory.

Jiang Ming sat on the iron-framed bed, his back against the wall, with a piece of letter paper spread out on his knees.

He was looking at the psychic notes he had compiled yesterday, which contained the method for establishing a signal baseline before anti-interference testing.

Xiucai Juan communicates with spirits five times a day, each time for thirty minutes, and he has already used three of them for technical purposes.

He wanted to try something different for the remaining two times.

Historical fragment search is a new feature of Xiucai Scroll.

The footage of the telegraph machine retreating northward on a rainy night that he had seen last time had been weighing on his mind.

The system labels it as "horizontal extension and peripheral connection of the network," which can only be used as background reference and cannot be taken as actual evidence.

But when Director Wang showed him the telegram about escalating noise last time, there was a meaning in his eyes that Jiang Ming couldn't quite put his finger on.

It was as if they knew more, but couldn't say it outright.

The intensity increased by 40%, the frequency interval shortened, and the number of jumping frequency points increased.

This change doesn't resemble a random noise source; it's more like a deliberate signaling process.

Jiang Ming closed his eyes, his consciousness sinking into the study space of the Tongtianlu.

[Historical Fragments of the "Connections to Heaven: Scholar's Scroll"]

He chose a peripheral path related to the underground radio front.

The image appeared intermittently, like an old film projector that had a stuck tape.

A gray roof appeared before my eyes; it was the sloping tiled roof commonly seen in Shanghai's alleyways.

A makeshift copper wire antenna was strung up, going from the chimney to the clothesline of the building next door.

A man sat in the attic with a homemade shortwave transmitter in front of him, his fingers pressing the telegraph key at a rapid pace.

In the distance outside the window, a truck with a rotating antenna is moving slowly.

That's a direction-finding vehicle.

The person sending the message suddenly stopped, waited a few seconds, and then started again with a completely different rhythm.

The pulse intervals first become dense and then sparse, and then jump to irregular alternation of long and short pulses.

The direction-finding vehicle stopped at the entrance of the alley. The antenna rotated twice but failed to lock onto the target. It had to move again and drive in the opposite direction.

The image gradually blurred and then disappeared.

[System Prompt: Historical fragments originate from horizontal extensions and peripheral connections within a broader context; they are provided for background reference only and should not be used as factual evidence.]

Jiang Ming opened his eyes and quickly wrote a few words on the back of the letter: Change the rhythm to shake the track, make the pulse interval jump irregularly, and create direction finding misjudgment.

The ironclad rule was there; he couldn't tell anyone about the fragments.

However, the direction given by the fragments can be expressed in another way.

If the regular clutter from the Northwest is pulses with fixed intervals, then its design purpose goes far beyond suppressing communications.

Rhythmic pulses can induce the automatic gain control of the receiving device to produce periodic responses, leading the operator to misinterpret it as a device malfunction.

Even more dangerously, the enemy could use this rhythm to deliberately create phase confusion in the direction-finding equipment, thereby concealing their true position.

Jiang Ming picked up his pen and wrote the telegram draft on a new sheet of paper.

"It is recommended to record the pulse intervals and repetition periods of the clutter ahead, and pay close attention to the temporal structure in addition to the intensity curve. If the interference presents as short pulses with a fixed rhythm rather than continuous noise, special attention should be paid to its interval pattern, as it may have characteristics that induce misjudgment in direction finding."

He folded the paper and put it in his pocket, intending to deliver it to the confidential office that afternoon to send a secret telegram.

He used the remaining two channeling sessions on two different questions.

One is the different stress mechanisms caused to the cathode of the electron tube by short-wave pulse interference and continuous noise interference.

Another is the transient response characteristics of automatic gain control when the receiver is exposed to periodic pulses.

After listening, the fiery pioneer scolded him again, saying that his question spanned three disciplines and that he should have gone to someone who worked in communications, not someone who worked in pipes.

Despite the criticism, he still offered a crucial assessment.

The transient current surge caused by a short pulse to the cathode is far greater than that of continuous noise of the same average power.

If the pulse rising edge is steep enough, it may cause local overload of the cathode, which will shorten its lifespan in the long run.

Jiang Ming added this line to the telegram draft as well.

"If it is confirmed to be pulse interference, it is recommended to reduce the tube's operating power by 10% to leave a margin and avoid damage to the cathode from pulse transient overload."

At 3 p.m., the telegram was sent from the confidential office of the Third Electronics Factory.

That very night, a reply arrived from the Northwest.

"Record the pulse intervals as instructed. Actual test results: The noise is indeed not continuous, but rather presents as periodic short pulses. The width is approximately 0.3 seconds, and the repetition interval is between 28 and 33 seconds, averaging about 30 seconds. The tube's operating power has been reduced by 10%, and the emission current of tube A01 is currently stable. A copy of the recording paper is attached; it will be sent back in a confidential bag tomorrow."

After reading the reply, Jiang Ming felt even more on edge.

Periodic short pulses mean that this is not ordinary noise, but a rhythmic signal.

This was sent by a person, and the other party knew how to hide themselves.

He folded the telegram and was about to leave the confidential room when Director Wang was already standing at the door.

"Little Jiang, come with me."

In Director Zhang's office, the curtains were drawn tightly shut.

Director Wang copied the pulse data sent back by Chen Zhiyuan onto a piece of paper and placed it in the center of the table.

Director Zhang sat opposite him, his face expressionless, but the water in his teacup remained untouched.

"Xiao Jiang, how did you come up with the idea of ​​having the front end record the pulse interval?"

Director Wang spoke in a calm tone, as if asking what was served in the cafeteria that day.

Jiang Ming had already prepared his answer.

"There is a section in Mr. Qian's lecture notes that talks about the basics of signal modulation and spectrum analysis."

"It mentions that the essential difference between periodic signals and random noise lies in whether there is a recognizable repeating structure."

"I was thinking that since we've been looking at clutter based on intensity, let's change our perspective and look at it from the time structure. Maybe we can discover something new."

Director Wang nodded and did not pursue the matter further.

He turned the sheet of paper with the data onto Jiang Ming and pointed to the numbers on it.

"The repetition interval is 28 to 33 seconds, with an average of 30 seconds."

At this point, he looked at Director Zhang.

Factory Director Zhang took out an even older piece of paper from the drawer.

The paper is yellowed, and there are scorch marks on the edges.

"This is a record from an old shortwave archive."

Factory Director Zhang placed the two sheets of paper side by side on the table.

"The original data contains a method of evading transmission, the core feature of which is that the pulse interval randomly jumps between 25 and 35 seconds, with an average period of about 30 seconds."

Jiang Ming looked at the numbers on the two pieces of paper.

The degree of agreement between the measured data and the old data in Northwest China is so high that it can be seen almost without calculation.

"But the direction is the opposite."

Director Wang lowered his voice even further.

"In older records, this kind of rhythm was used to evade tracking. The rhythm that's appearing in Northwest China now is something that's been infiltrated from the outside, with the aim of interfering with other people's direction finding."

Jiang Ming did not inquire about the origin of the old document.

He knew that some things shouldn't be asked.

But he knew very well that the similarity between this old shortwave technique and the noise from the Northwest meant that the other party was not just making a spur-of-the-moment move.

The other party has something, and it's a complete system.

"Little Jiang."

Factory Director Zhang put the old paper back into the drawer and locked it.

"Your pipe held up, that's good news."

"But the other side won't stop."

Jiang Ming nodded and stated his judgment.

"If the other side uses this rhythmic pulse jamming, its purpose is probably not just to suppress our communications, but to test our direction-finding capabilities."

"They want to confirm whether we can locate their launch source."

Director Wang and Factory Director Zhang exchanged a glance.

The office was quiet for a few seconds, with only the sound of footsteps of the duty officer changing shifts coming from the corridor outside the door.

"Go back and rest."

When Director Zhang spoke, his tone was gentler than usual.

"You've accomplished what you asked for regarding the pipes."

"Someone is taking care of what happens next."