Radio Hacks

1451 Articles

Listening In On Weather Balloons With RTL SDR

January 12, 2013 by 34 Comments

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Every day, twice a day, over 800 weather balloons are launched around the world at exactly the same time. The data transmitted from these radiosondes is received by government agencies and shared with climatologists and meteorologist to develop climate models and predect the weather. Near [Carl]’s native Auckland, a weather balloon is launched twice a day, and since they transmit at 403 MHz, he decided to use a USB TV tuner to receive data directly from an atmospheric probe.

The hardware portion of this project consisted of building a high gain antenna designed for 162 MHz. Even though the radiosonde transmits at 403 MHz, [Carl] was easily able to receive on his out-of-band antenna.

For the software, [Carl] used SDRSharp and SondeMonitor, allowing him to convert the coded transmissions from a weather balloon into pressure, temperature, humidity, and GPS data.

Pictures From Weather Satellites With A USB TV Tuner

January 4, 2013 by 40 Comments

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Several times a day, a NOAA weather satellite passes over your head, beaming down pictures of weather systems and cloud formations. These transmissions aren’t encrypted, and given the requisite hardware it’s possible for you to download these images from space as [Lovro] shows us in a tutorial video.

To get these near real-time satellite pictures, [Lovro] used one of those USB TV tuners we’ve grown so fond of. A somewhat specialized antenna is required to receive the right hand polarized transmissions from NOAA weather satellites, but with a few bits of wood and wire, [Lovro] made a helical antenna to listen in on the weather satellites transmitting around 137 MHz. After gathering a whole bunch of data from the satellites with SDRsharp, [Lovro] used an image decoder to turn an audio file into a picture taken from space just hours ago.

This isn’t the first time we’ve seen images from a NOAA weather satellite downloaded with a software defined radio; last year [hpux735] did just that with a somewhat inexpensive Softrock SDR. [Lovro]’s use of a USB TV tuner to receive the transmission from NOAA satellites is a lot easier on the pocketbook, though, with the largest expense being an investment in time to build a helical antenna.

Arduino Using A Straight Key For Morse Code Assistance

January 3, 2013 by 28 Comments

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For those unfamiliar with Ham Radio, there are lots of fancy tools these days to make it easier for the radio operator. But enthusiasts still like to get back to basics, and one way to do this is to participate in Straight Key Night. This is when you pull out your traditional Morse code keyer and have a chat with others around the world. The most recent event was on New Year’s Eve. The only drag is that it sometimes takes a while to find another Ham who’s listening, and this can mean repetitively keying the letters QC SKN for long periods of time (QC invites listeners to respond, and SKN is to inform them you’re participating in Straight Key Night). Sure, a programmable keyer will do this for you, but that is against the spirit of the event. [Mike Herr] found a grey area by mechanically interfacing an Arduino with a straight key.

You can see the straight key being pressed by a hobby servo in the image above. The servo is driven by the Arduino, which will transmit the series of letters automatically. As you can see in the video after the break, once [Mike] hears back from a fellow operator he switches to a huge wooden straight key for the rest of the conversation.

Continue reading “Arduino Using A Straight Key For Morse Code Assistance” →

Open Source Software Defined Radio Transceiver

December 21, 2012 by 30 Comments

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As the year draws to a close, we must look back and look at the advances in amateur radio this year. The RTL-SDR tuner hack, a USB TV Tuner to create a software defined radio receiver, is one of the greatest hacks of the last 12 months and a great justification for 2012 being the year of software defined radio receivers. 2013 is shaping up to have even more advances in the state of software defined radio. This time we’ll be transmitting as well, possibly with [AE9RB]’s Peaberry SDR transceiver.

The Peaberry SDR transceiver is a kit to both transmit and receive on every HAM band between 160 meters (1.8 MHz) to 17 meters (18 MHz). It does this through a USB interface and a 48kHz, 24-bit interface that is (or will shortly be) compatible with all the major SDR interfaces.

While the Peaberry SDR requires an amateur radio license to operate, we can’t wait to see what else will be coming to the software defined radio scene in the next year.

Thanks [Zach] for sending this one in.

Build A $360 Synthetic Aperture Radar With MIT’s OpenCourseware

December 18, 2012 by 38 Comments

A few profs from MIT’s Lincoln Lab are giving those poor MIT undergrads something to do over winter break: they’re teaching a three-week course on building a laptop-powered radar system capable of radar ranging, doppler, and synthetic aperture imaging. Interestingly, the radar system that teams will build for the class has a BOM totaling $360, and they’re also putting the entire class online if you’d like to follow along and build your own.

From the lecture notes from the course, the radio system is made out of an off-the-shelf  LNA, oscillator, and  splitter. By connecting two coffee can ‘cantennas’, it’s possible to record a .WAV file from the signal coming from the radar and use MATLAB to turn that audio signal into a doppler radar.

It’s a very ambitious project that goes deep down the rabbit hole of RF and analog design. One of the lecturers made a YouTube demo of the radar in ranging mode; you can check that out after the break.

Continue reading “Build A $360 Synthetic Aperture Radar With MIT’s OpenCourseware” →

Electronically Controlled NFC Tag

December 17, 2012 by 20 Comments

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[Per] is replacing his car stereo with a Nexus 7 tablet. It’s a great modification to add GPS, navigation, and a good music player, but [Per] wanted to pause his tunes and tell the tablet to go to sleep with an NFC tag. This means building a an NFC tag he can turn on and off, an interesting problem to say the least.

The easiest way to do this is with a CMOS switch, but a chip like a 74HC4066 is overkill for a project this simple. What [Per] needed was a single CMOS switch, something he found and fabbed a board for.

Now, with a press of a button, [Per] can activate his NFC tag and pause the music in his new stereo. Check out the video of this electronically controllable tag after the break.

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Transmit FM Using Raspberry Pi And No Additional Hardware

December 10, 2012 by 75 Comments

Now here’s a project that actually hacks the Rapsberry Pi rather than just using it as an embedded computer. [Londons Explorer] figured out how to turn the RPi into an FM transmitter. For now it’s done entirely in the user space, but we’re sure it could be improved if someone wanted to drill down further into the hardware. For those wanting to give it a try he’s rolled everything into a simple python package.

The technique requires nothing additional except a 20cm wire to serve as an antenna. The trick is to map GPIO pin number 4 to a position in memory. The clock generator is then used to toggle this pin at 100 MHz, which is the frequency to which your radio should be tuned. A fractional divider adjusts the frequency based on the sound file being transmitted.

The proof of concept for this was able to reliably transmit at a distance of about fifty meters through several walls. The problem is that this technique is limited in the amount of data which can be sent. Right now it’s only about 6-bit audio. But descending deeper through the abstraction layers to put DMA (Direct Memory Access) to use may be able to improve upon this.

[Thanks Owen via Reddit]