In this video I re-engineer a 40MHz garage door opener and build a small one for my Harley. I use SDR radio and Audacity to do the hacking and an AD9850 DDS and an Arduino to create a clone. The principle shown here can also be used for openers or key fobs operating on other frequencies.

At this point it’s pretty well-known that you can tack a long wire to the Raspberry Pi’s GPIO, install some software, and you’ve got yourself the worlds easiest pirate FM radio station. We say that it’s a “pirate” station because, despite being ridiculously easy to do, broadcasting on these frequencies without a license is illegal. Even if you had a license, the Raspberry Pi with a dangling bit of wire will be spewing out all kinds of unintentional noise, making it a no-go for any legitimate purposes.

In an effort to address that issue, [Naich] has written up a couple posts on his blog which not only discuss why the Pi is such a poor transmitter, but shows how you can build a filter to help improve the situation.

[Naich] then goes on to show how you can build a DIY filter “hat” for the Pi that not only cuts down a lot of the undesirable chatter, but even boosts the intended signal a bit.

Taming the PiFM Transmitter (Part 2)
http://naich.net/wordpress/index.php/taming-the-pifm-transmitter-part-2/

Is this Raspberry-Pi-based device the world’s smallest DVB (Digital Video Broadcasting) transmitter?

Lime Microsystems is one company that evangelizes an open-source philosophy and provides full details of its wireless chips. As a result, the open-source community has embraced the software defined radio (SDR) boards from Lime and is creating some exciting applications, which greatly extend the functionality of the device through the use of a natively enabled app store.

This digital TV transmitter, which is based on a combination of a LimeSDR Mini and a Raspberry Pi Zero, provides a perfect example.

This setup processes the camera output into a DVB2 compliant transport stream and onwards to the SDR, while the receiver features a decoder and display chain to drive an HDMI output (it also includes a spectrum analyzer). The demo uses RF tuned to 1.2GHz, which sits within the 10MHz to 3.5GHz range of the Mini. Designers can download the app to provide a DVB (Digital Video Broadcasting) video link and customize it to their exact requirements.

The open-source community is busy creating a wide variety of wireless applications using LimeSDR products, and then making these applications available for “app enabled” products. In addition to the video example discussed above, there are already designs for narrow and wideband FM transceivers, a spectrum analyzer using a UDOO X86 single board computer, a GSM base station using a Raspberry Pi and — with the addition of a Lime frequency range extender — the LimeSDR transmits and receives LTE signals at 10GHz.

In this tutorial, we will be showing you the basics of how to setup a Raspberry Pi Pirate Radio utilizing the FM Transmitter software and a piece of wire.
Basically, this piece of software allows you to broadcast a FM signal through your GPIO 4 pin. This means you can setup your own little radio station, however please be noted that the sound quality and range will be quite poor due to the signal been limited to mono and that most wires aren’t the best antennas.