Wireless Sniffing And Jamming Of Chronos And Iclicker

January 25, 2011 by Joseph Thibodeau 1 Comment

The ubiquitous presence of wireless devices combined with easy access to powerful RF development platforms makes the everyday world around us a wireless hacker’s playground. Yesterday [Travis Goodspeed] posted an article showing how goodfet.cc can be used to sniff wireless traffic and also to jam a given frequency. We’ve previously covered the work of [Travis] in pulling raw data from the IM-ME spectrum analyzer, which also uses goodfet.cc.

The Texas Instruments Chronos watch dev platform contains a C1110 chip, which among other things can provide accelerometer data from the watch to an interested sniffer. The i>clicker classroom response device (which houses a XE1203F chip) is also wide open to this, yielding juicy info about your classmates’ voting behaviour. There is still some work to be done to improve goodfet.cc, and [Travis] pays in beer–not in advance, mind you.

With products like the Chronos representing a move towards personal-area wireless networks, this sort of security hole might eventually have implications to individual privacy of, for example, biometric data–although how that might be exploited is another topic. Related to this idea is that of sniffable RFID card data. How does the increasing adoption of short-range wireless technologies affects us, both for good and bad? We invite you to share your ideas in the comments.

Radios Without Power Sources

January 25, 2011 by Mike Szczys 37 Comments

[Goodhart] is sharing his process for building a couple different AM radios. It’s surprising how few components he’s using; the first build is just a germanium diode, some wire, and a piezo earpiece. But it strikes us that both of the radios he gives build instructions for have no power source. We’re also amused by the process of selecting the station. His example uses 770 AM, and requires you to take the wire and place it up in a tree with the two ends about 1216 feet apart. We think there’s something a bit off with the math, but with that much conductor to start with there might be enough induced current for you to actually hear something come out the piezo. We don’t think we’ll be trying this anytime soon, but we’d like to hear comments from those of you who do (or already have).

555 Based AM Radio Transmitter

January 10, 2011 by Mike Szczys 33 Comments

Bust out that 555 timer and use it to build your own AM radio transmitter. The circuit that [Rtty21] is using only needs the timer chip, an NPN transistor, three caps, three resistors, and a potentiometer. It generates an amplitude modulation signal around the 600 kHz range which you will be able to pick up with any normal AM radio. From the comments on the article it seems you’ll get around 30-40 feet of range out of the device. We don’t see this as a competitor for the FM spy microphone, but maybe you can use it as a diy baby monitor.

Designing An RF Transceiver

December 9, 2010 by Mike Szczys 15 Comments

[William Dillon] is finishing up his degree. His final project as a student was to design an RF transceiver. He decided to work with the Microchip MRF49XA, which runs around $3 but will cost you $20 if you want it in a ready-to-use module. He didn’t find a lot of info on the Internet about communicating with these chips so he’s shared his design, code, and board files. If you’re ever wanted to delve into RF design this is a good primer. [William] talks about building around the example circuit from the datasheet but also includes a discussion of the calculations he made in working with the 434 MHz band, and an AVR-based library for using his module.

Copper-clad Enclosures

December 8, 2010 by Mike Szczys 29 Comments

Building a great looking box for your projects can be a challenge. [Ken] boils down his process of building enclosures out of copper clad (PDF) circuit board material into an illustrated guide in case you want to try this for yourself. Why would you want to use PC board? The fiberglass substrate makes for a strong and lightweight material. Also, [Ken] is a ham radio operator and the copper coating acts as an electrical shield for delicate components inside.

As you can see above he uses solder to tack the pieces together. There’s some important considerations that go along with this method. First, he cuts the pieces just a bit oversized and then sands them flat and square before assembly. Next, he uses some 20 gauge wire as a shim between a ninety-degree joint and a right angle jig. This shim compensates for the shrinking that occurs as the solder cools, making sure the joint gets pulled to a right angle. He even solders nuts in place so that screws can be used to attach the case cover to the chassis.

Yesterday we saw toner transfer used to make labels on an ABS case. If you make your enclosure out of copper clad, using toner transfer for panel labels will be a snap!

Radar Gun Teardown

November 28, 2010 by Chris Nelson 30 Comments

[Jeri Ellsworth] is at it again, this time she takes apart a hot wheels speed gun and in the process she does a good job of explaining how radar can be used to measure speed. She also demonstrates a way to determine if an object is approaching or receding from the radar gun.

The Doppler shift is one way to remotely measure the speed of an object. It works by measuring the change in frequency of a wave after it strikes an object. Rather than measuring the Doppler shift of the returning wave most radar guns use the phase shift. The reason is that the frequency shift of a relativly slow object (60mph), to a relitivly high frequency signal(10GHz) is small (about 0.893Hz), where the phase shift varies based on the distance of the object. This is all just a stepping stone in her quest to build a crude TSA body scanner.

Barcode Challenge For Radio Operators

November 27, 2010 by Mike Szczys 32 Comments

[Scott Harden] came across a few posts about QR code matrix barcodes coming through on the 40m baud radio band. A few operators had captured the signals and assembled them into the code block seen above but they weren’t able to get a clear enough shot for a smartphone to decode the image. [Scott] took on the challenge and decoded the mysterious message himself. He tried some graphic editing to separate and enhance the color channels in order to up the contrasts of the image. This helped, but still couldn’t be read automatically. In a move similar to those seen in Hackaday’s own barcode challenges he dropped the image into Inkscape so that he could manually clean it up. Once it was overlaid on a grid the job was pretty simple. the left side did require some more image manipulation and precision”squinting” to eliminate interference from the vertical banding, but he managed to get the message. We won’t spoil it here in case you want to take on the challenge yourself. Good luck!