Best examples of building a simple radio transmitter: 3 examples you can actually build

Let’s skip the abstract theory and jump straight into real circuits. When people search for examples of building a simple radio transmitter: 3 examples, what they usually want is:

• A tiny AM transmitter that can play audio on a nearby radio.
• A small FM transmitter that can send voice or music across a room or house.
• A basic digital-style transmitter that can send on–off signals like Morse code.

We’ll walk through those three, then sprinkle in extra variations so you get more than just 3 circuits—you’ll see several real examples of how changing frequency, modulation method, and components gives you very different behavior.

Before you start, a quick but important note: radio transmitters are regulated. In the United States, the Federal Communications Commission (FCC) sets rules for unlicensed low-power transmitters under Part 15 of its regulations. You can read more straight from the source at the FCC’s consumer guide on unlicensed devices: https://www.fcc.gov/general/radio-frequency-safety-0. Always keep your transmit power low and stay within allowed frequency bands.

Example 1: A simple AM transmitter you can hear on a regular radio

The first example of building a simple radio transmitter is an AM (Amplitude Modulation) transmitter that works with an ordinary AM radio. Think of it as a tiny personal “radio station” that only reaches a few feet or maybe a room.

How this AM example works

AM means you keep the radio frequency (the carrier) steady, but you vary its strength with the audio signal. Picture a flashlight that’s turning brighter and dimmer with the music: the beam is the carrier, and the brightness changes carry the sound.

In the most basic examples of AM transmitters, you’ll see:

• An oscillator that sets the carrier frequency (often around 1 MHz, in the AM broadcast band).
• A transistor or simple IC to generate and amplify that carrier.
• A way to inject audio (from a phone, MP3 player, or microphone) so it changes the amplitude.
• A short wire antenna, often just a few feet long.

One common beginner circuit uses a single NPN transistor (like a 2N2222), a tank circuit made of a coil and capacitor, and a small audio transformer or coupling capacitor to feed audio into the transistor’s base.

Parts list for a basic AM transmitter example

You can build a classic low-power AM transmitter with parts like these:

• 1 × NPN transistor (2N2222, 2N3904, or similar)
• 1 × variable capacitor (about 100–365 pF) for tuning
• 1 × coil (around 60–80 turns of enamel wire on a 1-inch form for ~1 MHz)
• A few resistors (1 kΩ, 10 kΩ, etc.)
• 1 × coupling capacitor for audio (0.01–0.1 µF)
• 1 × audio source (phone or MP3 player with volume control)
• 1 × 9 V battery and clip
• 1 × short wire antenna (6–10 feet of hookup wire)

You’ll find many real examples of this style of circuit in older electronics textbooks and hobbyist references. For a more theoretical background on AM, the open course materials from MIT OpenCourseWare (https://ocw.mit.edu) have solid explanations of amplitude modulation in their signals and systems courses.

How to test and use this AM example

Once you’ve wired the circuit on a breadboard or perfboard:

• Turn on the transmitter.
• Tune your AM radio through the band until you hear a quiet carrier (a gentle hiss or tone that appears and disappears as you switch the transmitter on and off).
• Play audio into the circuit and adjust the volume until you hear your music or voice.

This is one of the best examples for beginners because it’s forgiving, it uses common parts, and AM radios are still easy to find.

Variations on the AM transmitter example

To expand beyond this first example of an AM transmitter:

• Swap the audio input for a simple microphone amplifier and transmit live speech.
• Change the coil and capacitor values to move the transmitter to a quieter spot on the AM band.
• Use a 555 timer as the carrier oscillator and modulate its power line or control voltage with audio.

These variations give you several examples of building a simple radio transmitter: 3 examples and more, all based on the same AM foundation.

Example 2: A tiny FM “bug” transmitter for short-range audio

Now let’s move to FM (Frequency Modulation), which is what most modern radio listeners are used to. In FM, the strength of the signal stays almost constant, but the frequency wiggles slightly with the audio. This second example of building a simple radio transmitter is a small FM “bug” that can send your voice to a nearby FM radio.

How this FM transmitter example works

A classic beginner FM transmitter uses:

• A single transistor configured as a high-frequency oscillator.
• A tank circuit (coil + capacitor) tuned to somewhere in the FM band (88–108 MHz).
• A microphone and biasing network that slightly changes the transistor’s operating point, and therefore the oscillator frequency.
• A short antenna wire.

When you speak into the microphone, the small voltage changes cause the oscillator frequency to shift a tiny bit around its center frequency. An FM radio picks up those shifts as sound.

Parts list for a basic FM bug example

For this FM example of a simple radio transmitter, you might use:

• 1 × NPN RF transistor (2N3904 can work; RF-specific transistors like BF494 are even better)
• 1 × electret microphone capsule
• 1 × small variable capacitor (5–20 pF)
• 1 × tiny air-core coil (3–6 turns of 22–24 AWG wire, about 1/4-inch diameter)
• Several resistors and capacitors for biasing and coupling
• 1 × 3 V coin cell or 9 V battery (with proper biasing)
• 1 × antenna wire (about 1–2 feet)

You’ll see examples include very compact “spy bug” designs, but for learning, it’s better to build it larger and more spread out so you can adjust and debug.

Tuning and testing this FM example

FM circuits at 100 MHz are more sensitive to layout than low-frequency AM circuits. Keep your leads short and your coil neat.

To test:

• Power the transmitter and place it a few feet from an FM radio.
• Slowly tune the radio through the band until you hear a strong hiss or tone when you tap the microphone.
• Adjust the variable capacitor or slightly squeeze/stretch the coil to move the frequency.

Again, keep the range short. Under FCC Part 15 in the U.S., unlicensed FM transmitters must be very low power and cover only a small area. The FCC explains unlicensed transmitter rules here: https://www.fcc.gov/general/part-15-radio-frequency-devices.

Modern twists on the FM transmitter example

To bring this into the 2024–2025 era, hobbyists often pair this style of FM transmitter with:

• A small audio mixer circuit so you can combine microphone and music.
• A microcontroller-based audio source, like a Raspberry Pi streaming audio into the FM stage.
• Simple low-pass filters on the antenna side to reduce unwanted harmonics.

You’ll find discussions and updated real examples of low-power FM designs on university ham radio club pages (for example, engineering departments at large universities like MIT or Stanford often host student RF projects on their .edu domains).

This FM circuit is one of the best examples of building a simple radio transmitter: 3 examples often taught in introductory RF labs: basic AM, basic FM, and then a simple digital or keyed transmitter.

Example 3: A keyed RF transmitter for Morse code or simple data

The third of our examples of building a simple radio transmitter: 3 examples focuses on digital-style signaling. Instead of carrying continuous audio, this transmitter turns the carrier on and off to send information—think Morse code or short bursts of data.

You can think of this as the ancestor of what Wi‑Fi, Bluetooth, and other digital radios do (at much higher complexity and speed).

How this keyed transmitter example works

At its heart, this example uses:

• A stable oscillator at a chosen frequency (often in a license-free band, like 433 MHz in some regions or 27 MHz/49 MHz toy bands where allowed).
• A transistor or RF module that generates the carrier.
• A keying method: a pushbutton, a Morse key, or a microcontroller output that turns the carrier on and off.

If you want to stay very beginner-friendly, you can build a low-frequency keyed transmitter in the shortwave region (for example, around 7 MHz) using a crystal oscillator and a transistor amplifier.

Simple crystal-controlled transmitter example

This example of a simple keyed transmitter might use:

• 1 × crystal oscillator module (e.g., 7.040 MHz or another amateur band frequency if you are licensed)
• 1 × NPN transistor as a buffer/amplifier
• A few capacitors and resistors
• A low-pass filter to clean up the output
• A short wire antenna
• A telegraph key or momentary pushbutton

If you’re a licensed amateur radio operator, this can be your first real on-air project. If you’re not, you can still build the exact same circuit and test it into a dummy load (a resistor network that absorbs RF power instead of radiating it) and monitor it with a nearby receiver.

The American Radio Relay League (ARRL) has many real examples of beginner-level transmitters and keying circuits in its educational materials and books. Their education page at https://www.arrl.org/education is a good starting point.

Microcontroller-based keying: 2024–2025 trend

In recent years, one of the best examples of building a simple radio transmitter for students has been to pair a microcontroller (like an Arduino or Raspberry Pi Pico) with a basic RF front end.

Some common patterns:

• Use an Arduino to generate a square-wave carrier (for very low frequencies) and key it for Morse code.
• Use a low-cost RF module (like ASK/OOK 433 MHz modules sold for remote controls) and drive it with microcontroller data.
• Experiment with very low-rate digital modulation, sending text from one microcontroller to another.

These are still examples of building a simple radio transmitter: 3 examples in spirit: you have a carrier, a way to control it, and an antenna. The difference is that a microcontroller takes over the job of keying and timing, opening the door to more advanced experiments like simple telemetry or sensor data links.

More than 3: extra real examples and variations you can explore

While we’ve focused on three main examples—AM audio, FM audio, and keyed/digital—it helps to see how many other examples include only small changes to those designs.

Here are several extra real examples you can explore once you’ve built one or two of the main circuits:

• An AM transmitter that sends temperature data by rapidly switching between two audio tones. A receiver and laptop can decode which tone is present.
• A simple FM transmitter that uses a guitar pickup instead of a microphone, turning your guitar into a wireless instrument for a nearby FM radio.
• A keyed transmitter controlled by a light sensor, where shining a flashlight on the sensor turns the carrier on. This is a fun way to combine optics and RF.
• A low-power AM transmitter that sends a recorded message triggered by a motion sensor—like a talking sign that only reaches a few feet.
• A digital OOK (on–off keying) transmitter built from a cheap RF remote module, controlled by an Arduino sending sensor readings.
• A crystal-controlled transmitter that sweeps through a few frequencies by switching crystals with transistors or relays.

Each one is an example of taking the same core ideas—oscillation, modulation, and radiation—and remixing them into something slightly different.

Safety, legality, and staying out of trouble

Any time you talk about examples of building a simple radio transmitter: 3 examples or more, it’s important to talk about the rules too.

In the U.S., the FCC regulates radio transmitters. Very low-power “Part 15” devices are allowed without a license, but they must meet tight limits on field strength and frequency. Similar rules exist in other countries through agencies like Ofcom in the UK.

A few guidelines:

• Keep power low and range short—think room or house, not neighborhood.
• Avoid transmitting on frequencies used by emergency services, aviation, or licensed services.
• Consider using dummy loads and shielding when you’re just experimenting with circuit behavior.
• If you want to transmit farther or on amateur radio bands, study for a ham radio license. In the U.S., that’s handled by the FCC, and the ARRL provides study resources.

For a more formal introduction to radio frequency exposure and safety, the FCC’s RF safety page (https://www.fcc.gov/general/radio-frequency-safety-0) explains exposure limits and basic safety practices.

Why these are some of the best examples for learning RF

These three circuits—AM audio, FM audio, and keyed/digital—are often considered the best examples of building a simple radio transmitter: 3 examples because they each teach a different piece of the RF puzzle:

• The AM example teaches you how amplitude changes can carry audio and how tank circuits set frequency.
• The FM example shows how tiny shifts in frequency can carry sound and how layout matters at higher frequencies.
• The keyed/digital example connects radio with information theory: on–off patterns become messages.

Taken together, they give you a solid hands-on foundation. From here, you can move toward software-defined radio, spread-spectrum systems, or modern wireless standards with much more confidence, because you’ve seen real examples of the basic building blocks.

FAQ: Common questions about examples of simple radio transmitters

Q: What are some easy examples of building a simple radio transmitter I can try this weekend?
A: The three easiest examples of transmitters to start with are a low-power AM transmitter for a nearby AM radio, a tiny FM bug that can send your voice to an FM radio, and a keyed transmitter for Morse code using a crystal oscillator. All three can be built from common parts and powered from a 9 V battery.

Q: Which example of a simple radio transmitter is best for absolute beginners?
A: The AM transmitter is usually the most forgiving. It runs at lower frequencies where layout is less sensitive, and you can tune it with a standard AM radio. That’s why many teachers use it as the first example of a working RF circuit.

Q: Do I need an amateur radio license to build these examples?
A: You do not need a license to build them and test them into a dummy load or at very low power under Part 15 rules. But if you want to radiate more power or operate on amateur bands, you’ll need a ham license in most countries. The ARRL (https://www.arrl.org) explains licensing and exam preparation.

Q: Are these real examples similar to how commercial radios work today?
A: Conceptually, yes. Commercial systems are far more complex and tightly regulated, but they still use oscillators, modulators, amplifiers, and antennas. These simple circuits are stripped-down real examples of the same core ideas.

Q: Where can I learn more about the theory behind these examples of transmitters?
A: University sites like MIT OpenCourseWare (https://ocw.mit.edu) host free courses on signals, systems, and electromagnetics. The ARRL also publishes beginner-friendly books on radio and electronics that build on the same examples of simple transmitters you’ve seen here.

If you pick even one of these circuits and actually build it, you’ll understand radio in a way that no amount of reading can replace. Start small, keep it legal, and treat these examples of building a simple radio transmitter: 3 examples as your personal launchpad into the world of wireless.