AM stands for Amplitude Modulation and it is a technology that is used for communication. It used to be a very popular means of communication and entertainment. Now, very few people listen to the radio. On the top, very few people listen to AM and FM radio stations. Now we all live in a world obsessed with technology and the internet. Almost everyone has a smartphone these days. Communication through mobile is very easy and cheap. So we are moving away to new complex ways of communication. But AM radio is quite an interesting and simple thing. So here we are learning how to make an AM Radio transmitter. This can be a good fun project for kids and also useful in emergencies.
There is another FM (Frequency Modulation) as well. Both of these use different technology to make communication possible. There are many benefits of FM, but simple AM transmitters are very easy to make. This can be made with very less and cheap parts. It is a good DIY project for kids and enthusiasts. We can use the AM voice transmitter to send audio, voice, music, and also receive using a receiver. It all depends upon the size, power, design, and antenna. We can change the design to get more power and range. For now, we are only making a very simple AM transmitter. We are using small and inexpensive parts. It can be made within 1 hour if we have all the parts. So now, let’s start with the building process.
Important Parts for AM Radio Transmitter
First, we need a few things to build a low-power simple AM transmitter. Some of the basic things are copper wire, soldering iron, solder, and electrical tape. Be very careful while working with soldering iron. Keep the working space clear and read instructions carefully. So, these are some of the basic things that you need for the build.
- Power supply: 9V Battery
- Battery Clip
- Circuit Board
- Audio Transformer: 1000 Ohm to 8 Ohm
- 1 MHz Crystal Oscillator
- 1 Microphone (Mic)
- Insulated Wire
- 3.5MM Headphone jack
These parts are very easily available in the electronics market. Check your online stores for these parts. If you want, do try to find parts in the local market. These kinds of things are mostly found in shops that sell parts for TV, radio, and robotic. Ask your local electronic repair shop for more details. Those people have contacts, and they know the shops. We can also extract a mic from an old headset. PC headset has a mic, which works perfectly. You can also use a 3.5 mm jack to get the audio source from music players. People living in the US can easily buy parts from Radio Shack and other sources.
Building Steps
At first, do refer to the schematic diagram in this article for the build. It tells us the way to connect the parts and make the AM voice transmitter. Now let us discuss the connections and schematics in detail.
The audio transformer has two sides of windings. There are two leads on the side with 8-ohm winding. On the other hand, there are three leads on the side with 1000 ohm windings. The central lead is of no use to us. Then we have a 1 MHz oscillator with 4 leads. We only use three of the leads and leave the fourth one. The high impedance winding of the transformer is connected to the mic, as shown in schematics. Then one end of the 8-ohm winding is connected to the positive lead of the battery. Another end of the winding is connected to one lead of the 1 MHz Oscillator. The negative lead of the battery is connected to one lead of the oscillator with the ground. The output lead is made into an antenna using a wire.
We are connecting the 8-ohm side to the oscillator to get the best range. But if your source can’t drive it, connect the mic to the 8-ohm side. And connect your 1000 ohm winding to the oscillator. You can use a 3.5mm audio input jack to feed in audio from another source. A normal AM radio receiver can easily catch the audio emitted by this transmitter. Be careful and don’t make the transmitting antenna bigger than 12 inches. Doing so can cause interference with other signals. It is better to keep this project as small as possible. We recommend extending the antenna only in the case of an emergency. But be careful of the guidelines of your locality and administration.
Testing the Transmitter
Connect the correct wires to the terminals of the 9V battery. Also, connect the 3.5mm jack to the audio source. Take your AM transmitter near to a radio. Adjust the frequency knob to 1000 and try. If your oscillator is connected to another side, try changing frequencies. Try to adjust both volume and frequency in the radio receiver. Connect the ground terminal to the ground for getting better reception. You can also experiment with different antenna lengths. But be careful and study local laws on such transmissions.
Also Read: Steps to make Simple AM Receiver
Use in Emergency
Communication is one of the most important things during an emergency. We do need good food, sanitation, and a place to live during such times. But we first try to contact our loved ones. Most of the time, normal cell phones, the internet go down, and transmitters can be very beneficial. These things remain off-grid from the internet and other cellular connections. Therefore in such a situation a simple AM radio and receiver can be helpful.
These kinds of transmitters are also handy in times of emergency. Disasters don’t come with prior notice. Imagine a situation after a natural disaster where there is no internet, mobile network, landline, or any other digital communication. In such a case, we can use these simple electronics. Solar Flares, Earthquakes, Tornados, Floods can destroy basic communication infrastructure. If society members have receivers and helpful radio transmitters, then it can be beneficial.
Spies have also been using it since World War I as a bug. These days mobile phones have radio support. In this situation, a handy AM radio transmitter can be a lifesaver. If you are a far thinker, then always keep a bag ready for emergencies. For such people, this device is a must. This project is for kids, electronics lovers, and normal people. It is always fun to make things on your own.
Original Published: 2014/08/24
