Tiny FM transmitter bugs rooms

Lucid Science delves into spy-tech once again with this tiny FM transmitter. Their post demonstrates a bit larger version than seen above, using a 9-volt battery and protoboard sized to match which makes for easier soldering. The design uses a microphone, two transistors, enameled wire for the coil, as well as various resistors, capacitors, and a potentiometer. What you end up with is an amazingly clear audio signal that can be picked up with a normal FM radio.

This would make a great project to do with the kids. You can talk about circuit design, practice soldering, and when finished they’ve got an almost miraculous toy to play with. Just be careful what you say around the house, the room might be bugged!

A simple FM transmitter

Here is a low component count FM transmitter. It sacrifices some features, like the ability to adjust the frequency, for simplicity’s sake. The build method is fairly common with amateur radio but we don’t see it around here too much. Each component gets a 5mm-by-5mm copper clad pad which is super glued to the ground plate as an insulator. There’s even a pictorial example of this method if you need some help with visualization.

One of the schematics included in the article shows how to incorporate a condenser microphone into the unit. We guess that makes it pretty easy to add an FM ‘bug’ to your arsenal of covert listening devices. Just make sure to check your local laws before building and using this. We’re not sure what the FCC would think of it here in America so we’re hoping some well-informed readers will educate us with a comment.

[Thanks Bart]

Small and simple FM radio

[gpsKlaus] built this little FM radio (translated) based on the AR1010 IC. That chip is controlled via I2C by an ATtiny45 microcontroller. His tuning implementation relies on presetting 16 stations in the firmware and selecting them with the white potentiometer.

The FM chip came on a breakout board from SparkFun. Not bad at around $15 as it includes the crystal, some caps and a few resistors, and you don’t have to try and solder to the fine pitched pads on that minuscule package. We’re a little unsure of the features included in the part as the datasheet is lacking in detail and the reference datasheet that SparkFun includes in the description is obviously for a much more full-featured chip. Still, this would be a fun thing to play around with if you’ve grown tired of blinking LEDs.

If you don’t want to let an integrated circuit do all the heavy lifting try this post for a guide on building your own radio tuner.

1953 Radio includes tubes, AM, FM, and MP3

This vintage radio can play AM, FM, and MP3, all with a classic sound. Inside you’ll find a new AM radio tube-amp, providing the functionality you’d expect from the device. The rest of it comes from a conglomeration of parts; an FM receiver board from another radio and an MP3 player with remote control and USB connector. The classic sound we mentioned above comes from an AM modulator. That’s right, the auxiliary audio boards aren’t connected directly, but are broadcast on the AM band so that your latest MC Lars album has the same sound quality as the traffic report.

Check out this similar project from last year that adds RDS to a vintage radio.

Arduino balloon tracking

The Ferret is a high-altitude balloon tracking hardware package. Created by [Adam Greig] and [Jon Sowman], it uses an Arduino to gather NMEA data from a GPS unit, format the data into a string, and transmit that string on narrow-band FM. The project, built in one afternoon, is a tribute to the prototyping simplicity the Arduino provides.

The unit was powered by four AA batteries, using the Arduino’s on board voltage regulator. This provided a bit of heat which helps in the frigid reaches of the upper atmosphere. The bundle above was put in a project box and attached to the outside of the balloon’s payload, then covered with foam for warmth and moisture resistance. This tracking is a lot less complicated than some of the photography setups we’ve seen for balloons. It’s also more versatile because it broadcasts the GPS data so that many people can track it, rather than just logging its location.

New from SparkFun


SparkFun is rolling out interesting things to play with every week. They’ve added a NanoMuscle actuator that uses a shape memory alloy to lift nearly 70 times its own weight. Their LilyPad collection has expanded to include small momentary switches and a thermistor type temperature sensor. Lastly, they’ve got an FM receiver module. It just needs an antenna and uses I2C or SPI for control.