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

Early the next morning, at the Northwest Base's classified laboratory.

Chen Zhiyuan removed tube A01 from the test bench, checked the sealing interface and pin status, and after confirming that there were no abnormalities, put it back into the shockproof box.

This tube has been running continuously for more than twelve hours in the clutter frequency band, and the emission current has never dropped below 270. The dark red light from the cathode has always been uniform.

"Change to tube number two."

Old Zhou took the No. 02 tube out of the shockproof box and installed it on the test bench according to the procedure.

The calibrated spare meter is connected in parallel into the circuit. After preheating at low voltage for thirty minutes, the voltage is gradually increased, with each level maintained for five minutes.

At rated power, the main meter reading is 269 and the standby meter reading is 271, both stable with no fluctuation.

Chen Zhiyuan stared at the watch face and said in a low voice, "Adjust the frequency."

Old Zhou slowly turned the signal generator knob, and the output frequency slid into the noise zone.

The hands on the dial began to show familiar short, sharp tremors, the same rhythm as the one encountered last night with tube A01, with intervals between twenty-eight and thirty-three seconds.

However, the emission current of tube A02 remained almost unchanged.

Chen Zhiyuan stared at it for three minutes, and the pointer of the backup meter remained locked at 271, without even a slight drift of plus or minus one microampere.

Although tube A01 did not collapse while operating in the clutter region, it still exhibited vibrations within a range of plus or minus two microamps.

The No. 02 tube is even more stable.

Old Zhou leaned closer to the watch face and wiped the sand from his eyes with the back of his hand.

"This one is even more stable than the first one. Are you sure these two tubes came from the same batch?"

Chen Zhiyuan opened the copy of Jiang Ming's factory manifest and pointed to the data on it.

"The production volume of A01 is 275, and the production volume of A02 is also 275. The production process is exactly the same."

After he finished speaking, he marked the time on the notepad and continued to stare at the watch face.

Ten minutes, twenty minutes, thirty minutes.

Tube A02 operated stably in the clutter region for half an hour without any signs of attenuation.

Old Zhou leaned against the wall, took out half a crumpled cigarette from his pocket, didn't light it, and just chewed on the cigarette paper with it in his mouth.

"Chen Zhiyuan, I've been working in communications for eleven years, and I've used no fewer than twenty different types of Soviet tubes. I've never seen one that could withstand this kind of interference for half an hour."

"You two are quite something, running for a whole day and night and half an hour, and you're acting like nothing happened."

Chen Zhiyuan didn't respond, but simply looked at the data of Jia-01 and Jia-02 side by side in the notebook.

The two tubes exhibit highly consistent performance in the same clutter frequency band, with a difference in transmission current of no more than two microamps and an attenuation rate of almost zero.

This shows that the technology used in the Third Electronics Factory was not a matter of luck.

If the first one can score, and the second one can score, then it's no coincidence.

He wrote a line at the bottom of the notepad.

"The clutter region behavior of A01 and A02 is consistent, confirming process repeatability."

He paused for a moment after writing this line.

He recalled a sentence at the end of Jiang Ming's plan, enclosed in parentheses, as if it were a casually added note.

If both branches behave in the same way, it means we're on the right track.

Chen Zhiyuan closed his notebook, picked up the telegram paper, and began to write.

That same afternoon, at the Third Electronics Factory in the suburbs of Beijing.

When Jiang Ming saw the telegram forwarded from the Confidential Office in Workshop No. 1, he was sitting next to the testing table organizing the psychic notes from the previous day.

"The No. 02 tube operated in the clutter region for 30 minutes without attenuation, and the transmission current stabilized at 271. The two tubes performed consistently in the same frequency band, confirming the repeatability of the process."

Jiang Ming placed the telegram on the table and wrote a "V" next to it with a pencil.

Both branches held up.

The 1.1% formula, seven-degree self-locking edge, Kovar alloy stepped annealing, and all sintering curves and sealing processes of the Third Electronics Factory are not isolated cases, but rather a repeatable technical system.

This conclusion is more important than any data from a single branch.

Wu Hanzhang walked over from the other end of the workshop, saw the telegram on the table, bent down and glanced at it, said nothing, but patted Jiang Ming's shoulder heavily.

The chief engineer's hands were rough and thick; when he patted my shoulder, they smelled of rust and machine oil.

Jiang Ming folded the telegram and put it in his pocket, then started thinking about his next step.

It's good news that both branches can operate stably in the clutter region.

But the information that Director Wang and Factory Director Zhang showed him yesterday still weighed on his mind.

The pulse interval is 28 to 33 seconds, with an average of 30 seconds, which matches the transmission avoidance method in a certain old shortwave data, only in the opposite direction.

If the purpose of the other side using periodic pulses is not to suppress communications, but to test their ability to locate, then what they really want to know is whether anyone in this area can find them.

In other words, the other party knows that they are sending a signal, and also knows that the signal will be detected sooner or later.

They are not afraid of being discovered, but they are afraid of being identified.

Jiang Ming sat at the tin table and drew a simple diagram on scrap paper with a pencil.

A transmitter radiates a pulse signal outward, and several receiving points are scattered in different locations, each receiving the signal at different times and with different intensities.

If multiple receiving points can simultaneously record the signal arrival time, theoretically the direction of the transmitting source can be determined by cross-location of time differences.

However, if the pulse rhythm has deliberately designed irregular jumps, the automatic gain control at the receiver will produce transient response deviations, and the phase comparison accuracy will also decrease significantly.

Direction finding will become unreliable.

That's their goal.

They don't care about being heard, they only care about not being found.

Jiang Ming put down his pencil and stared at the diagram on the scrap paper for a long time.

Ensuring that the tube can withstand interference and guarantee uninterrupted communication is only the first step.

If the other party changes its interference method or continues to increase the power, the tube cannot withstand the interference indefinitely.

To truly solve the problem, we cannot simply passively defend on the receiving end.

We need to find out where the other person is.

Once the source is found, the problem is solved.

All five of his psychic readings today were focused on this direction.

The first time, he asked the pioneering firefighter what role vacuum tubes played in shortwave direction-finding receivers.

The pioneer's answer was concise and to the point, with only one sentence at its core.

The soul of a direction-finding receiver lies not in the amplifier, but in the mixer stage.

The noise figure and frequency stability of the mixer tube determine the phase comparison accuracy, which in turn determines the angular resolution of the direction finding.

The second time, he asked the pioneer of vacuum and materials interfaces whether the current tube could be used directly in the direction-finding mixer stage.

The other person spoke very quickly and directly denied it.

Your tube is a power tube, not a mixer tube.

Mixer tubes require low noise and high linearity, which are two different things from anti-interference. Don't confuse them.

The third time, he asked the female pioneer of precision instruments what the most critical structural limitation of a simple direction-finding device was.

Her answer was calm and accurate.

The simplest direction finding requires a loop antenna and a receiving front-end that can perform phase comparison.

Accuracy depends on the antenna aperture and the receiver noise floor; the larger the aperture, the more accurate the direction; the lower the noise, the finer the resolution.

The fourth time, he pressed for details, asking if there were any countermeasures if the other party used irregular pulses to interfere with phase judgment.

The fiery pioneer cursed him again, saying that this was in the realm of communication warfare, not in the realm of pipes.

But in the end, the other party still added a sentence.

If the pulse arrival time can be recorded precisely to the millisecond level, and post-event comparison can replace real-time direction finding, then irregular rhythms will not fool you.

The fifth time, he asked a more specific question.

What is the lowest level of accuracy that can be achieved when building a simple loop antenna using existing industrial conditions?

The female pioneer provided a numerical range and several key constraints.

The diameter must be no less than 30 centimeters, the copper tube wall thickness must be no less than 1 millimeter, the shielding gap must be precisely aligned with the front, and the grounding must be a single point.

The accuracy achieved in this way is approximately ±15 degrees, which is sufficient to provide a rough direction in the shortwave band.

±15 degrees.

Not precise enough, but narrows down the search scope sufficiently.

After using up his five spiritual connections, Jiang Ming sat at a tin table with three sheets of scrap paper spread out in front of him, covered with arrows and numbers.

He picked up a clean sheet of paper and began to draw.

A circular ring, 35 centimeters in diameter, is made of bent copper tubing. A 3-millimeter-wide shielding gap is left at the top of the ring, and a coaxial cable is connected to the bottom, leading to the receiver input.

When a loop antenna rotates, the signal strength will reach a zero point. The direction of the zero point is the source of the signal, or its opposite direction.

With a mixer tube of low noise level and a narrowband receiver, you can make the most basic manual direction finding device.

He doesn't need to build radar or guidance systems.

All he needs is a rotating loop antenna and a good tube.

He already has the pipe.

The structure of a loop antenna is not complicated; with Lao Sun's skills, bending a copper ring is not a problem.

The real bottleneck is the mixer tube.

What he's making now is a high-power anti-interference tube, not a low-noise mixer tube.

These are two directions.

But at least the direction is clear.

Jiang Ming folded the sketch and wrote a line of text in the lower right corner.

"To find the source, we can't just resist interference; we must also determine the direction."