All Keystone Science videos

Signal build

FM Transmitter

Start with the video, then use the science notes and recommended parts below to follow the idea behind the build.

Radio & soundBuildRadio

Watch on YouTube

How it works

What this project is testing.

An FM transmitter turns sound into tiny changes in radio frequency. The wave keeps about the same strength, but its spacing compresses and stretches with the audio.

Read more

This demonstrates why FM is good at rejecting noise: random amplitude bumps matter less when the message lives mostly in frequency changes.

f (t) = f_{c} + Δ f x (t)

The instant-by-instant carrier frequency shifts around f_c in proportion to the audio signal.

Recommended parts

Products used in this project.

Affiliate links may earn Keystone Science a commission. Match ratings, values, sizes, polarity, and safety requirements to your own build before buying.

Amazon Basics 8-Pack 9V Long-Lasting Alkaline Batteries for Smoke Detector, Electronics & Audio, Reliable, 5-Year Shelf Life

batterypower

Amazon Basics 8-Pack 9V Long-Lasting Alkaline Batteries

$12.694.7(242K)

General electronics battery pick; choose AA/AAA variants when the circuit calls for them.

Goupchn Universal P6100 Oscilloscope Clip Probes 100MHz with Accessories Kit 1X 10X 2 Pack

test probes / leadstest equipment

Goupchn Universal P6100 Oscilloscope Clip Probes, 100MHz, 1X/10X, 2 Pack

$13.994.7(126)

BOJACK 3 Values 130 Pcs Solderless Breadboard 4 Pcs 830 Tie Points & 400 Tie Points & 126 Pcs Flexible Breadboard Jumper Wires

breadboardprototyping

BOJACK Solderless Breadboard Kit with 830/400 Tie-Point Boards and Flexible Jumper Wires

$9.994.4(692)

ElectroCookie Large PCB Prototype Board Kit Solderable Breadboards for Electronics Projects Compatible for DIY Arduino Soldering Projects, Gold-Plated (6 Multi-Pack, Blue)

printed circuit board / PCBprototyping

ElectroCookie Large PCB Prototype Board Kit, Solderable Breadboards for Electronics Projects

4.8(111)

EDGELEC 120pcs Breadboard Jumper Wires 20cm Wire Length Optional Dupont Cable Assorted Kit Male to Female Multicolored Ribbon Cables

jumper wires / hookup wirewiring

120pcs Breadboard Jumper Wires, 20cm Dupont Cable Assorted Kit, Male to Female

$6.984.7(4,500)

BOJACK 1000 Pcs 25 Values Resistor Kit 1 Ohm-1M Ohm with 5% 1/4W Carbon Film Resistors Assortment

resistorpassive electronics

BOJACK 1000 Pcs 25-Value 1/4W Carbon Film Resistor Assortment Kit, 1 ohm-1M ohm

$9.994.7(4,500)

BOJACK 24Value 630pcs Aluminum Electrolytic Capacitor Assortment Box Kit Range 0.1uF－1000uF

capacitorpassive electronics

BOJACK 24-Value 630pcs Aluminum Electrolytic Capacitor Assortment Box Kit, 0.1uF-1000uF

$16.994.7(953)

CHANZON 100pcs 5mm LED Diode Lights Assortment 10 Colors x 10pcs Diodes (Clear Transparent Lens) Emitting Lighting Bulb Lamp Assorted Kit Variety Color White Red Yellow Green Blue Orange UV Pink

LEDsemiconductor

100pcs 5mm LED Diode Lights Assortment, 10 Colors

$6.994.5(1,800)

BOJACK 10 Values 250 Pcs A1015 BC327 BC337 C1815 S8050 S8550 2N2222 2N2907 2N3904 2N3906 PNP NPN Power General Purpose Transistors Assortment Kit

transistor / MOSFETsemiconductor

BOJACK 10-Value 250 Pcs PNP/NPN General Purpose Transistor Assortment Kit

$8.994.7(763)

BOJACK 20 Values 200 Pcs Inductor 10 uH to 10 mH 1 W Color Ring Inductor 1 Watt Assortment Kit

inductor / coilpassive electronics

20 Values 200 Pcs Inductor Assortment Kit, 1uH to 4.7mH, 0.5W Color Ring Inductors

$13.994.8(182)

CQRobot Speaker 3 Watt 8 Ohm Compatible with Arduino Motherboard, JST-PH2.0 Interface. It is Ideal for a Variety of Small Electronic Projects.

speakeraudio

CQRobot 3 Watt 8 Ohm Speaker for Arduino and Small Electronics Projects

$7.994.5(457)

Syncwire 3.5mm Nylon Braided Aux Cable (3.3ft/1m,Hi-Fi Sound), Audio Auxiliary Input Adapter Male to Male Cord for Headphones, Car, Home Stereos, Speaker, iPhone, iPad, iPod, Echo & More – Black

audio source / phoneaudio

3.5mm Nylon Braided Aux Cable, Male to Male, 3.3ft

$7.994.6(119K)

Use with an existing phone or audio player.

Panasonic Portable AM/FM Radio, Battery Operated Analog Radio, AC Powered, Silver (RF-2400D)

AM/FM radio receiverradio

Panasonic RF-2400D Portable AM/FM Radio, Battery Operated or AC Powered

$29.994.5(33K)

E-outstanding 1 Pair AM FM Radio Universal Antenna, 62.5cm 24.6" Length 4 Section Telescopic Stainless Steel Replacement Antenna Aerial for Radio TV

antennaradio

E-outstanding 1 Pair AM/FM Radio Universal Telescopic Stainless Steel Replacement Antenna

$7.994.4(2,400)

SUNYIMA 10pcs Mini Monocrystalline Solar Cells Solar System Kit 50mm X 50mm/1.96" X 1.96" 2V 160MA for DIY Charge Solar Panels

solar cell / photovoltaic panelpower

SUNYIMA 10pcs Mini Monocrystalline Solar Cells, 50mm x 50mm, 2V 160mA

$15.994.5(284)

Tegg 18PCS Adjustable Capacitor 5PF 10PF 20PF 30PF 40PF 50PF 60PF 70PF 120PF Trimmer Variable Capacitance Plastic for Arduino

variable capacitorradio

Tegg Adjustable Variable Capacitor Kit for Radio Projects

$9.99

Confirm capacitance range for the exact radio/transmitter circuit. Review requirements and safety guidance before buying.

Project files

Prints, kits, and downloads.

Diagrams, printable files, kits, or companion downloads will appear here when they are ready to use.

Coming soon

Contact

Events, speaking, collaborations, and news.

Send the project name, outlet or audience, timing, location, and the context you want covered.

Email Keystone Science