Original subtitles

hi I'm Sean Regan

I'm technical editor with Make magazine

FM transmitters can be pretty complicated to build

but not this one

it's based on the work of Japanese multimedia artist

Tetsuo Kogawa

and was built and documented for us by

well by me these days

radio is everywhere

and we often take it for granted

but how many of us really understand how it works

building your own transmitter is a great way

to educate yourself about an essential technology

and can also be lots of fun

let's get started

you'll need an afternoon

some soldering skill

and a few simple parts and tools

to complete this project

head over to your local Radio Shack

where you can pick up everything you'll need

including these parts

and these tools

you'll also need an FM radio receiver

to pick up the transmissions from your finished build

we'll start by wiring the mono phone plug

that you'll connect to your MP3 player

or other audio source

first unscrew the threaded housing from the plug

and set it aside

solder a length of red stranded wire

to the center tip contact

and another length of black stranded wire

to the outer shield contact

use pliers to crimp the wires in place

then tighten the housing back on

next we'll form the coil

strip about 10 centimeters of 18 gauge

solid copper wire

and wind 4 turns around the threads of 1/4 20 bolt

turn the coiled wire off the bolt

as if you're unthreading a nut

and clip each lead as shown

bend little feet on the ends of the leads

and adjust them so the coil will stand upright

holding a pair of pliers in each hand

grab the coil's leads

and stretch it evenly along its length

until the feet are 12mm

apart on center

you may need to even out the coil spacing just a bit

with a screwdriver or other tool

now for the circuit board

use a straight edge

a utility knife

and the edge of a table

to score and snap

a 5 by 4 centimeter rectangle

from the copper clad board

and this will be your ground plane

next score and snap 5 small pads

these will be glued to the board

to create mounting points for component leads

which are not connected to the ground plane

we'll start building the circuit by mounting the coil

apply a small drop of glue

to the underside of one of the pads

use tweezers or small pliers to carefully position it

near the center of the ground plane

now glue a second pad to the board as shown

these 2 pads should be 12 millimeters apart

to match the coil

now you can solder the coil across these 2 pads

it's easiest if you pre tin the surface of the pads

and both feet of the coil

before making the connections

begin with a

01 micro fared capacitor

then another pad

the 27 kilo resistor

the 4th pad

the electrolytic capacitor

remember that electrolytic capacitors are polarized

so make sure you've got this one turned the right way

a 10 kilo resistor

and another point 0

one capacitor

and then the final pad

now it's time to add the transistor

bend the leads as shown

and then solder the transistor body in place

connecting the collector to the coil

the base to the resistors

and the emitter to the free pad

now solder one 10 picoferied

ceramic disk capacitor across the transistors

collector and emitter

and a 470 ohm resistor between its emitter and ground

finally solder a second 10 picoferied

ceramic disk capacitor

between the coil and the ground plane as shown

now we just have to add the battery clip

and the phone plug

solder both black wires to the ground plane

the red battery clip lead to the end of the coil

with the resistor

and the red phone plug lead to the negative side of the

electrolytic capacitor

now all that's left to do is power up the circuit

by connecting a 9 volt battery

and an audio source

like an MP3 player

or a smartphone

start playing a song

or other easily recognizable audio track

then turn on your FM radio

and scan through the bands to locate the transmission

if you can't locate your signal at first

try changing the orientation of your receiver's antenna

with respect to the board

and scan for it again

to make your transmitter more portable

you can attach the 9 volt battery

to the back of the circuit board with some Velcro

or double sided tape

depending on your equipment

and the broadcast spectrum in your area

you should be able to receive

transmissions up to 30 feet away

it is possible to

boost that distance by adding an antenna

but remember that in most countries

you are supposed to have a license to operate an FM

transmitter

be considerate of others

and remember that unlicensed broadcasters can get in

legal trouble

if they interfere with normal

public use of the radio spectrum

finally if you build this project

or a project

based on it

or if you just have questions or comments

do let us know on the project home page

thanks for watching