Take A Break From Arduinos, And Build A Radio Transmitter | Hackaday

When you start watching [learnelectronic’s] a two-part series of articles,

, You may disagree with some of his historical lessons. After all, the origin of broadcasting is a controversial topic. Fortunately, you don't need to know who invented the radio to enjoy it.

The first transmitter uses a fixed oscillator to which AM modulation is applied. Of course, these oscillators are usually not optimized for this service, but they work normally. In the second part, he lowers the frequency to 1 MHz, and then can listen to that frequency on a standard AM radio, and then add an amplifier so that any audio source can modulate the oscillator. The noise is loud, but the sound is obviously there.

This is of course impractical, but it combines

This can be a great weekend project for kids who want to hang up electronics. The idea that some simple parts can send and receive audio is very powerful. If you are ready to design a better product for graduation, we have

.

Scrape the bottom of the bucket.

I must agree... A simple transistor oscillator will have better waveforms, fewer harmonics and higher transmit frequencies. Square waves are wrong for making transmitters, because your energy will be spread over various frequencies that you don’t need or don’t need. These fixed oscillators also have a partial decoupling function, so modulating Vcc is not an excellent way to obtain information through them.

The decoupling capacitor may be 0.1uF ceramic inside the tank. For a 10kHz signal, the impedance of the capacitor cap is 160 ohms. The driver circuit only needs to have a lower impedance to achieve brute force.

It should also be noted that the averaging amplifier will be unstable when driving such a high capacitive load without causing stability issues. However, for OP's target group, the topic is a bit advanced.

I'm afraid I must agree. I couldn't see it in the first few minutes. Talking about the "tank circuit", whether it is RC or LC, there is no other explanation. It shows a graph of a sine wave with axes labeled "palmpalm" and "time". I can't imagine how a person new to broadcasting can gain any useful knowledge from it.

Clark's second law: The only way to find the limit of possibility is to risk exceeding the limit and entering the impossible.

This video is clearly the first step. I might suggest to use a resistor, which should enter a capacitor-isolated parallel diode from the output, and a DC bias current with audio modulation. The high-side modulated RF output of the diode.

Go on. This is the beginning of a hobby and even a career. A very good reference is the ARRL manual.

Electronics should be interesting and discoverable, and I can see it with your enthusiasm. Keep going, and good luck. 73.

Projects designed for children are great, but bands that have the government heavily discuss licensing and approval will weaken their enthusiasm.

Have power limits been specified for such projects? Make sure you minimize interference and reduce the chances of local authorities chasing you?

Keep the power as low as possible to avoid interruptions. However, for unlicensed transmitters, the maximum power of the FCC is 1 watt. look here:

Applies to type approved equipment or equipment with a declaration of conformity similar to that used in Europe. This thing is just an illegal sender.

Just declare it as an experimental clock generator and see if it is below the EMC limit (probably). With this feature, you will not disturb anyone unless you are a HAM operator next door.

Well, you can link to the rules, but obviously you haven't read them yet. For different frequency ranges, the limits are different, but this is not all. At most frequencies, the limit is for the maximum field strength at a given distance from the antenna, so this depends on the power delivered to the antenna and the antenna's gain. Part 15 is very complicated, but it is everyone's responsibility to manufacture the transmitter and intend to operate it without a license to understand any part of the applicable regulations.

It is great to see many learning, experimenting, monitoring, listening, receiving and transmitting. Learnelectronics has some other great videos.

The fourth step of learning from my place of teaching is the last lesson I know... after watching/listening, reading/solving problems, and application/experiment.

We absolutely need to conduct more interception and surveillance on ships, from underground to space...especially if you have not signed a non-disclosure agreement related to signal pollution.

After all, the origin of broadcasting is a controversial topic. Fortunately, you don't need to know who invented the radio to enjoy it. "

Yes, to be sure, I think getting me into the field of broadcasting is a very controversial topic. Wow!

Then, I started to study amateur radio, electronics and RF engineering again, and was amazed at how controversial the topic of RF alone was after the Bachelor of Science degree (such as ionizing radiation and non-ionizing radiation, and considering high and low energy material effect states) …, RF specific effects, thermal effects, non-thermal effects, etc.), and then the history of radio and other physical theories.

Based on the point of view of scientists, the early "practical" and "non-practical" views are interesting.

Novelty magic shop tricks... Most people may not believe what can still be done today, such as "This is impractical", or is still magic as this beautiful young lady said (from 2:49 to 3:12 watch):

I like that this video also records the controversy of the radio reception function:

(Watch at least the first video between 30 and 33 seconds).

The first thing I built about 50 years ago was an AM transmitter. Even if it uses an old carbon fiber phone microphone and uses an AC128 coil to rotate 100 times on a ferrite, it can easily get 100m clear audio. The rod on the tuning cap of the old radio is 365pf hollow. This is not a small joke, but has it ever worked? Everyone said it sounds like a closed radio station, and then we found FM stereo, luckily there is an IC BA ****? This makes spy bugs a reality, they are all built on 9v batteries, they are cheap, with the right antenna, if we are tired of venturing into 27MHz pirate radio, mainly in the United States and Australia, it relies on There is something called "skip". The signal bounce of the ionosphere will fade in and out, but all of us are full of fun and meet new people. We have learned that many of us have converted our rigs into American citizen bands. We Envious of our Yankees teammates’ output power is 5 watts, and in New Zealand, its legal output speed is 1/2 watts, so even under the right conditions it can still work, almost as if not in another country, we All have pirate names, such as SawDoctor, Bones, Frogsticker, and mine is of course Silverdragon. To commemorate any contact we will exchange QSL cards. Do I still have it? A 100-page folder filled with cards from all over the world. I got cards from almost all states in the United States. Usually, radio inspectors will look around for pirates. I have a huge 27MHz ground plane antenna on my roof. How difficult is this? As I grew older, I transitioned to HAM Radio, but for some reason, it was not that interesting, but it was fine there.

In the United States, many CBers don't care about the legal limit of 5W, but run amplifiers to several kilowatts of power (often without proper output filtering). No wonder you hear them all the way to your country! (Just kidding, I understand how skip works.)

The US Federal Regulatory Commission (FCC) seems to have given up tracking and prosecuting all perpetrators, but it is definitely the worst offender. This may be a tricky issue for both ham and CBers. I have never encountered any trouble, whether it's ham or Cber.

What I want to say is that I prefer CB radio when I was 17 years old, but now in my 40s, I prefer ham radio.

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