Radio Hacks

1461 Articles

Building A Better Software Defined Radio (and Transmitting As Well)

October 24, 2012 by 39 Comments

By now most Hackaday readers should be familiar with this year’s latest advance in software defined radio. With a simple USB TV tuner dongle, it’s possible to receive FM broadcasts, GPS data from satellites, and even telemetry from aircraft flying overhead. There is one limitation to this setup, though: it’s receive only. Hacker extraordinaire [Michael Ossmann] is looking to make a better software defined radio called the HackRF.

The HackRF is an incredibly ambitious project – able to receive just about anything between 100 MHz and 6 GHz (this includes everything from the top of the FM radio band to cordless phones, cell phones, WiFi, and basically any radio technology that has been commercialized in the last 15 years), the HackRF is also able to transmit. Yes, with the HackRF it’s possible to build your own software-defined WiFi module, or just broadcast bogus GPS information.

Compared to the $20 TV tuner SDR dongles we’ve played around with, the HackRF isn’t exactly cheap. [Mossmann] figures he’ll be able to sell the device for about $300. A fair bit of change, but much, much less than professional, commercial SDR solutions.

A very cool advance in the state of SDR, but reason dictates we must suggest that everyone who wants a HackRF to start studying for their amateur radio exam now. Being a licensed radio operator won’t stop you from any sort of malicious intent, but with at least with licensing comes with the possibility of knowing what evil you’re doing.

You can check out the wiki for the HackRF over on the gits along with the current hardware design

Super Serious Garage Door Opener

October 24, 2012 by 18 Comments

Tired of cheap plastic garage door openers? [Yetifrisstlama]’s is probably the most serious garage door opener that we’ve seen. The case is an old emergency stop switch, which has plenty of space for the circuitry and features a big red button.

This build log starts with details on reverse engineering the original door opener’s protocol. It’s an amplitude-shift keying (ASK) signal that sends a 10 bit code to authenticate. The main components inside are a PIC16LF819 microcontroller, a MAX7057 ASK/FSK transmitter, and some RF circuitry needed to filter the signal. There’s a mix of through hole and surface mount components mounted on a prototyping board, requiring some crafty soldering.

[Yetifrisstlama] says that the next step is to add a power amplifier to increase the range. The code and project files are also provided for anyone interested in working with ASK. While the hack looks awesome, it might make bystanders think you’re doing something more sinister than opening a garage door.

APRS IGate Built Using A Raspberry Pi

October 19, 2012 by 28 Comments

The hardware seen above is used to bridge a local RF radio network to the APRS-IS network. The APRS-IS is an Internet Service that uses a web connection to communicate between APRS networks in different parts of the world. The Raspberry Pi is perfect for this application because of its ability to connect to a network, and its native use of Linux.

On the software side the majority of the work is done by a Python script. It is responsible for setting up and monitoring a connection with an APRS-IS server. To connect to the handheld radio unit a USB sound card was used. The Multimon package is used to send and receive audio packets through this hardware.

[Sunny] has a few upgrades planned for the system. The device needs to report its location to the APRS-IS server and the plan is to add functionality that will look of the WiFi AP’s location automatically. It may also be possible to get rid of the radio all together and use a DVB dongle as a software defined radio.

27 MHz Transmitter/receiver Pair Made With 555 Timers

October 18, 2012 by 33 Comments

Get your feet wet with radio frequency transmitters and receivers by working your way through this pair of tutorials. [Chris] built the hardware around a couple of 555 timers so you don’t need to worry about any microcontroller programming. He started by building the transmitter and finished by constructing a receiver.

Apparently the 27 MHz band is okay to work with in most countries as long as your hardware stays below a certain power threshold. The carrier frequency is generated by the transmitter with the help of a 27.145 MHz crystal. The signal is picked up by the receiver which uses a hand-wrapped inductor made using an AL=25 Toroid Core. We’d say these are the parts that will be the hardest to find without putting in an order from a distributor. But the rest of the build just uses a couple 555 timer chips and passive components, all of which will be easy to find. The video after the break shows the project used to receive a Morse-code-style message entered with a push button. It would be fun to interface this with your microcontroller of choice and implement your own one-way error correction scheme.

Still More Software Defined Radio Fun On The Mac

October 12, 2012 by 9 Comments

Even though the world of software defined radio started out as a Linux-only endeavor, several recent software releases have put the ball fully into the court of OS X users. [hpux735]’s new Cocoa Radio release provides a (nearly) fully functional software defined radio for anyone with a USB TV tuner and a mac.

Earlier this week, we saw (and tested)  [Elias]‘ port of gqrx and were reasonably impressed. [hpux735]’s app does the same job and also provides the source so you can compile it yourself.

Previously, [hpux735] ported the osmocom driver for these RTL2832U-based USB TV tuner dongles to the Mac and wrote a small Cocoa driver. The new Cocoa Radio software uses this driver and adds all the features you’d expect from a software radio package; in the title pic for this post, you can see a top 40 radio station near my house and their insipid hatred of dynamic range.

[hpux735] posted a few videos of his development process. You can check those out after the break.

Continue reading “Still More Software Defined Radio Fun On The Mac” →

OS X Port Of Gqrx Is The Easiest Way To Get Into Software Defined Radio

October 8, 2012 by 18 Comments

Many have tried to put together an easy package for running software defined radio packages on the Mac. Not many have succeeded the way [Elias]’ port of the gqrx SDR package has. It’s simply the easiest way to get a software defined radio up and running on the mac.

gqrx is a front end for the very popular GNU Radio software defined radio toolkit. Originally designed for the FUNcube SDR dongle, gqrx can also be made to work with one of the many, many USB TV tuners that have come out of China this past year for use as a software radio.

[Elias]’ port of gqrx isn’t the first app to put software defined radio on the Mac, but it certainly is the easiest. Simply by downloading [Elias] disk image, plugging in a TV tuner dongle, and starting the app, I was able to have a software radio receiver on my MacBook Air in less than a minute.

Everything required by GNU Radio and gqrx is already included, making this the easiest way to get SDR on a Mac. Very awesome work from [Elias], and we thank him.

Communicating With A Beam Of Light

September 22, 2012 by 39 Comments

Last weekend, ARRL, the national association of amateur radio, held a contest called, “10 GHz and up” with the goal of communicating via radio or microwaves over long distances. [KA7OEI] and a few friends decided to capitalize on the “and up” portion of the ’10 GHz and up” contest by setting up a full-duplex voice link over a distance of 95 miles. They used the 478 THz band, also known as red LEDs and laser pointers.

With [Ka7OEI]’s friends [Ron] and [Elaine] perched atop a 5700 foot-high mountain near Park City, Utah, [Gordon], [Gary] and [KA7OEI] trudged up a hill about 10 miles north of Salt Lake City. With the help of a pair of 500,000 candlepower spotlights, the two teams found each other and began pointing increasingly higher power LEDs at each other.

The teams started off with 3 Watt red LEDs before moving up to 30 Watt LEDs and a photodetector at each end. Even though the teams weren’t working with a true line-of-sight – refraction of the atmosphere allowed them to transmit this far – they were able to transmit tone-modulated Morse and even full-duplex voice.

Not bad for a transmission that bends the FCC’s “275 GHz and up” amateur band to its breaking point.