Countercurrent 1982

Chapter 7
After buying everything, Duan Yun took the bus back to the factory.

No one was at home, so Duan Yun put the package of components under the bed, took out the multimeter and enameled wire he just bought, and prepared to modify the radio at home.

Retrofitting this 'original' radio was a piece of cake for Duan Yun.

He found a used scrapbook by his sister's bed, and Duan Yun drew a circuit diagram on it with a pencil according to the components of the radio.

Speaking of which, Duan Yun has basically used CAD software in his previous life since college, but his technique of hand-drawn circuit diagrams has not fallen behind at all.

Repairing and modifying the radio's shortwave reception sensitivity is not a high technology, but Duan Yun has another idea.

For the average electrician, there are two ways to improve the shortwave sensitivity of the radio:
One is to increase the working current of the inverter tube.However, increasing the working current is very limited. This method not only cannot improve the selectivity, but also makes the noise of the inverter tube larger.

The second is to connect a 465KHz series resonant element in parallel between the short-band oscillation coil tap and the ground.Although this method can improve the selectivity of the radio, there is often no place for post-adding components on the circuit board.

However, these two methods have limited improvement in the sensitivity of the radio, and the effect is not obvious.

Duan Yun thought for a moment before thinking of a feasible modification plan.

He first removed the three IF transformers on the radio and opened the casing to reveal the internal structure wrapped with enameled wires.

After Duan Yun quickly calculated the number of turns needed to replace the enameled wire, he replaced the original 0.8 wire diameter enameled wire with the newly purchased 1.0 wire diameter enameled wire.

This is a delicate job, but fortunately, Duan Yun is a person with strong hands-on ability. When he first came into practice with radio at the university, he was the leader in his class.

It took half an hour for Duan Yuncai to rewind the coil of the transformer. In addition, according to his own ideas, he added a few capacitors and resistors to the input and output circuits of the radio with a soldering iron.

The bulk resistors that Duan Yun bought are not marked, so they can only test one by one, and then pick out the components that can be used.

After more than ten minutes, Duan Yun's modified radio was finally completed.

Compared with electricians who can usually modify radios these years, Duan Yun's level is obviously much higher. Generally, electricians can only amplify short-wave signals by increasing the working current of the inverter, but they will also increase the noise, resulting in a very good listening effect. Poor, and the radio modified by Duan Yun not only greatly improves the short-wave receiving sensitivity, but also greatly improves the selectivity, and has an obvious advantage, that is, there is no noise at the radio station. This improvement is the reason why the parallel resistance used by Duan Yun is smaller. .Channel selection is also convenient, the original weak and unstable radio signals become easy to receive, and the phenomenon of mixing stations is greatly improved.

After a simple test, Duan Yun was very satisfied with the result of his modification, and immediately packed the multimeter and electric soldering iron and put it back under the bed.

"Brother, you didn't go to work today?"

Just when Duan Yun was about to close the back cover of the radio, with the sound of the door lock, her younger sister Duan Fang appeared at the door with her schoolbag on her back.

"There's no work in the workshop today." Duan Yun said casually, and then said to Duan Fang with a smile: "Just in time, I fixed the radio for you, how about the signal?"

"You really know how to repair a radio?" Duan Fang was dubious, but she still took the radio from her brother.

"Bah." When Duan Fang just turned on the radio, she didn't hear the familiar noise, and her brows suddenly wrinkled.

But soon, something surprised her.

The AM signal of the radio is obviously much clearer than before, there is no noise in the process of searching for channels, and it also receives channels that have never been listened to before.

What surprised Duan Fang the most was that for the first time in the daytime, she heard a lot of foreign language channels on shortwave clearly.

Among Duan Fang's classmates, there are many wealthy dual-career children at home. The small radios they use are all new on the market, but none of them can receive so many and so clear foreign broadcast signals during the day!
"How?" Duan Yun asked with a smile.

"Brother, how did you do it?" Duan Fang's face was full of joy, she held the little radio in her arms and said to Duan Yun, "Did you go to the city today to repair it?"

"It's said that your brother and I modified it myself." Duan Yun pouted and continued: "Remember what you told me before, bring the radio when you go to the cram school on Saturdays and Sundays, and help me and your classmates do it. Advertise it, modify it for five yuan, and if the business is good, I will buy you delicious food!"

"Five dollars!" Duan Fang was surprised when she heard the words, and then said, "This...is this a bit too expensive?"

"It's not expensive, and the materials for refitting are not expensive?" Duan Yun smiled, and then said: "You think that other people's families are as poor as ours, and they can spend more than 100 to buy the best radio on the market. Spending five yuan is not a big deal at all, so how about I give you one yuan for every business you get me? Excluding the cost of materials, your brother and I can’t actually earn a few yuan... "

Duan Yun knew that his younger sister was naturally eloquent and articulate. As long as this girl is willing to promote the school hard, there will be business, so she simply used dividends to 'bribe' her. Anyway, this is not a matter of speculating and committing a crime, and it will not affect it. to her study life.

"One dollar per unit?" Duan Fang's eyes lit up when she heard the words.

The biggest pocket money Duan Fang got since she was a child was when she was in elementary school and organized a spring outing on June [-]. At that time, she clearly remembered that her mother gave her two yuan, which included the money for lunch.

Today, a single business is worth one dollar, which is definitely a huge income that Duan Fang can't even imagine!
"Your brother, my words always count!" Duan Yun raised his brows.

"Success!" Duan Fang readily agreed.

"We make money in the future, let's eat meat every day!"

"I still eat meat every day, brag! In our factory, the factory manager's family dare not say that he eats meat every day." Duan Fang said this, but she was very happy and said: "I'll go to cook first, Brother, wait."

After finishing speaking, Duan Fang flung two small braids to prepare to wash and cook.

My mother worked overtime in the sewing club at noon and didn't come back, and there were only two siblings for lunch.

My sister's cooking skills are not good, and she can cook not many dishes. In fact, there are not many dishes to cook at home.

Many girls in this era basically learned to cook very early, which is also a compulsory course before marriage.

Duan Yun, who had been served by his fiancee Xiaozao in his previous life, was a little bit unbearable when he saw that there were basically no oily meals, but now the family is under these conditions, and with his mother's salary, he can maintain enough food and clothing. Not bad.

This also made Duan Yun secretly determined to make money as soon as possible, and make a lot of money!

(End of this chapter)