HamRadioTweets Gets the Word Out

In times of crisis, or extreme government control, it can be difficult to spread critical information to people who can help. A good example of this was during the Arab Spring in 2011. When your Internet connection is taken away, it can feel as though all is lost. Unless you have a ham radio, that is.

For many people the thought of ham radio conjures up images of old guys twisting knobs listening to static, but it’s actually come a long way in our modern digital age. For example, you can now send tweets via ham radio. This project was actually started in 2011 by [Bruce Sutherland]. The Egyptian government had shut down the country’s Internet access after citizens were posting information about the extreme violence they were facing. [Bruce] wanted a way to help  others get the word out, and he came up with HamRadioTweets. This system allows a user to send tweets via ham radio.

The system actually piggybacks off of a ham radio service called APRS. This service is most often associated with GPS tracking systems, such as those found in nearspace balloons, but it can also be used to send simple text messages over the air. APRS works thanks to the vast network of receiving stations setup all around the world. These stations can receive messages and then re-transmit them, greatly extending the reach of the original transmitter. Some of them are even hooked up to the Internet to get the messages to go distances that would be extremely difficult and unreliable by traditional means.

[Bruce’s] system hooked into the Internet component and watched for messages being sent specifically to “TWITR”. The Python based system would then read these messages and re-transmit them over Twitter. The project died out a while back after Twitter updated their API. Now, it’s been rebuilt on Ruby by [Harold Giddings]. The project website was handed over to [Harold] and he is currently maintaining it. Hopefully you’ll never need to use this software, but if the time comes you will be glad it’s available. You can watch [Harold] bounce an APRS message off of the International Space Station and on to Twitter in the video below. Continue reading “HamRadioTweets Gets the Word Out”

Old-Timey MP3 Player Blends Old Styling With New Technology

No, this isn’t the first commercial MP3 player ever produced. It’s a blend of the old and the new, old time looks with modern electronics. [viscomjim] recently made this MP3 Player from the ground up for the noble reason to give as a Christmas present.

[viscomjim] started by laying out a circuit using a solder-less breadboard to test his circuitry. He’s using PIC microcontroller to control the unit. There is an 20×4 LCD display, two rotary encoders with push buttons, a serial MP3 player module, real time clock and an infrared receiver. A wires-all-over mess wasn’t acceptable for this Christmas gift so [viscomjim] put on his learning cap and tried out Autotrax Dex PCB layout software. This was his first project with the software and everything went well. After the design was done, the board files were sent out to a fab shop. A few weeks later they were delivered. All the parts were wired up and tested and… it worked!

Next up was building a cabinet, this one was built out of wood and stained to give it a feeling of yesteryear. A pair of 4″ car speakers are responsible for sharing the tunes and are powered by a small amplifier and power supply mounted inside the enclosure. The front panel is laser cut clear acrylic and backed with a nicely prepared Photoshop’d parchment paper graphic. And those fancy grill covers, also laser cut acrylic, this time opaque brown in color.

There are only two knobs for control, the left is the volume and the right is the program changer. Push the left knob inward and the unit turns on or off, the right plays and pauses. This MP3 player plays music off the internal SD card on the MP3 module. [viscomjim] also went one step further and implemented some code to work with an Apple remote he had kicking around, hence the IR receiver mentioned above.

If you’d be interested in making something similar, you’re have-way there as [viscomjim] made his schematics available but, unfortunately, not his code. Want to build your own MP3 Player but want something a little smaller? Check this tiny one out.

‘Gibson Girl’ emergency beacon built from a Wind-Up Flashlight

Batteries flat and no cellphone coverage and you need to communicate hundreds of miles?  No problem. [Peter Parker VK3YE] has created a wind-up ham radio transmitter built into a discount store crank-handle flashlight (or torch). No batteries – all power comes from you turning the hand crank. This design was inspired by the ‘Gibson Girl’ emergency beacon transmitter used during Second World War. But what used to be an very large, full body cranking box is now tiny and simple to crank. Let’s take a look at he video and the build details after the break.

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Over-engineering Ding Dong Ditch

One day, [Samy]’s best friend [Matt] mentioned he had a wireless doorbell. Astonishing. Even more amazing is the fact that anyone can buy a software defined radio for $20, a small radio module from eBay for $4, and a GSM breakout board for $40. Connect these pieces together, and you have a device that can ring [Matt]’s doorbell from anywhere on the planet. Yes, it’s the ultimate over-engineered ding dong ditch, and a great example of how far you can take practical jokes if you know which end of a soldering iron to pick up.

Simply knowing [Matt] has a wireless doorbell is not enough; [Samy] needed to know the frequency, the modulation scheme, and what the doorbell was sending. Some of this information can be found by looking up the FCC ID, but [Samy] found a better way. When [Matt] was out of his house, [Samy] simply rang the doorbell a bunch of times while looking at the waterfall plot with an RTL-SDR TV tuner. There are a few common frequencies tiny, cheap remote controls will commonly use – 315 MHz, 433 MHz, and 900 MHz. Eventually, [Samy] found the frequency the doorbell was transmitting at – 433.8 MHz.

After capturing the radio signal from the doorbell, [Samy] looked at the audio waveform in Audacity. It looked like this doorbell used On-Off Keying, or just turning the radio on for a binary ‘1’ and off for a binary ‘0’. In Audacity, everything the doorbell transmits becomes crystal clear, and with a $4 434 MHz transmitter from SparkFun, [Samy] can replicate the output of the doorbell.

For the rest of the build, [Samy] is using a mini GSM cellular breakout board from Adafruit. This module listens for any text message containing the word ‘doorbell’ and sends a signal to an Arduino. The Arduino then sends out the doorbell code with the transmitter. It’s evil, and extraordinarily over-engineered.

Right now, the ding dong ditch project is set up somewhere across the street from [Matt]’s house. The device reportedly works great, and hopefully hasn’t been abused too much. Video below.

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Building a Portable Ham Radio Station

Nowadays, you can get into ham radio on the cheap. A handheld radio can be had for less than $30, and licensing is cheap or free depending on where you live. However, like most hobbies, you tend to invest in better kit over time.

[Günther] just finished up building this portable ham station to meet his own requirements. It runs off 230 VAC, or a backup 12 V car battery for emergency purposes. The Yaesu FT897d transceiver can communicate on HF + 6m, 2m, and 70 cm bands.

This transceiver can be controlled using a Microham USB-3 interface, which provides both CAT control and a soundcard. This pre-built solution is a bit simpler than the DIY option. With the interface in place, the whole rig can be controlled by a laptop running Ubuntu and open-source HAM software.

With the parts chosen, [Günther] picked up a standard 5 U 19″ rack, which is typically used for audio gear. This case has the advantage of being durable, portable, and makes it easy to add shelves and drawers. With an automotive fuse block for power distribution and some power supplies, the portable rig is a fully self-contained HAM station.

HackRF Blue

For anyone getting into the world of Software Defined Radio, the first purchase should be an RTL-SDR TV tuner. With a cheap, $20 USB TV tuner, you can listen to just about anything between 50 and 1750 MHz. You can’t send, the sample rate isn’t that great, but this USB dongle gives you everything you need to begin your explorations of the radio spectrum.

Your second Software Defined Radio purchase is a matter of contention. There are a lot of options out there for expanding a rig, and the HackRF is a serious contender to expand an SDR rig. You get 10 MHz to 6 Gigahertz operating frequency, 20 million samples per second, and the ability to transmit. You have your license, right?

Unfortunately the HackRF is a little expensive and is unavailable everywhere. [Gareth] is leading the charge and producing the HackRF Blue, a cost-reduced version of the HackRF designed by [Michael Ossmann].

The HackRF Blue’s feature set is virtually identical, and the RF performance is basically the same: both the Blue and the HackRF One can get data from 125kHz RFID cards. All software and firmware is interchangeable. If you were waiting on another run of the HackRF, here ‘ya go.

[Gareth] and the HackRF Blue team are doing something rather interesting with their crowdfunding campaign: they’re giving away Blues to underprivileged hackerspaces, with hackerspaces from Togo, Bosnia, Iran, India, and Detroit slated to get a HackRF Blue if the campaign succeeds.

Thanks [Praetorian] and [Brendan] for sending this in.

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Extremely Detailed FMCW Radar Build

A lot of hackers take the “learn by doing” approach: take something apart, figure out how it works, and re-purpose all of the parts. [Henrik], however, has taken the opposite approach. After “some” RF design courses, he decided that he had learned enough to build his own frequency-modulated continuous wave radar system. From the level of detail on this project, we’d say that he’s learned an incredible amount.

[Henrik] was looking to keep costs down and chose to run his radar in the 6 GHz neighborhood. This puts it right in a frequency spectrum (at least in his area) where radar and WiFi overlap each other. This means cheap and readily available parts (antennas etc) and a legal spectrum in which to operate them. His design also includes frequency modulation, which means that it will be able to determine an object’s distance as well as its speed.

There are many other design considerations for a radar system that don’t enter into a normal project. For example, the PCB must have precisely controlled trace widths so that the impedance will exactly match the design. In a DC or low-frequency AC system this isn’t as important as it is in a high-frequency system like this. There is a fascinating amount of information about this impressive project on [Henrik]’s project page if you’re looking to learn a little more about radio or radar.

Too daunting for you? Check out this post on how to take on your first radar project.