Sometimes the best builds aren’t anything new, but rather combining two well-developed hacks. Marc was familiar with RTL-SDR, the $30 USB TV tuner come software defined radio, but was surprised no one had yet combined this cheap radio dongle with the ability to transmit radio from a Raspberry Pi. Marc combined these two builds and came up with the cheapest portable radio modem for the Raspberry Pi.
Turning the Raspi into a transmitter isn’t really that hard; it only requires a 20cm wire inserted into a GPIO pin, then toggling this pin at about 100 MHz. This resulting signal can be picked up fifty meters away, and through walls, even.
Marc combined this radio transmitter with minimodem, a program that generates audio modem tones at the required baud rate. Data is encoded in this audio stream, sent over the air, and decoded again with an RTL-SDR dongle.
It’s nothing new, per se, but if you’re looking for a short-range, low-bandwidth wireless connection between a computer and a Raspberry Pi, this is most certainly the easiest and cheapest method.
http://hackaday.com/2013/11/09/transmitting-data-with-a-pi-and-rtl-sdr/
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