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!

Ubertooth Board For Bluetooth Experimentation

November 26, 2010 by Mike Szczys 9 Comments

Ubertooth Zero is the first offering in [Michael Ossman’s] quest for a Bluetooth sniffing and hacking hardware platform. We’ve seen some of his hacks in the past, like the build-in guitar tuner and some pink pager fiddling. The Ubertooth dongle is his original design based around an LPC1758 ARM Cortex-M3 processor paired with a Texas Instruments 595-CC2400-RTB1 to handle the 2.4 GHz RF communications. Looking at the bill of materials shows a very low cost for the components at just under $30 (if you can get your hands on a PCB to mount them on). He’s written firmware as well as host code to help you up start pulling Bluetooth packets out of the air as quickly as possible.

What can you do with this? That’s up to you, but whatever it is you accomplish, we’d like to hear about it.

FM Bug Using Salvaged SMD Parts

October 22, 2010 by Mike Szczys 20 Comments

If you’re a soldering ninja this FM transmitter bug is for you. It’s quite similar to the one we looked at yesterday, but this uses 100% salvaged parts. Two phones donated components; a Nokia 3210 for its voltage-controlled oscillator and a Nokia 1611 for the rest of the parts. The bad news is that mobile technology like cellphones use some of the smallest surface mount packages known to man. That’s where the soldering skill come into play. The good news is that if you’ve been scavenging for discarded phones in order to reuse their LCD screens you already have these parts on hand.

[Thanks George]

Tiny FM Transmitter Bugs Rooms

October 21, 2010 by Mike Szczys 30 Comments

Lucid Science delves into spy-tech once again with this tiny FM transmitter. Their post demonstrates a bit larger version than seen above, using a 9-volt battery and protoboard sized to match which makes for easier soldering. The design uses a microphone, two transistors, enameled wire for the coil, as well as various resistors, capacitors, and a potentiometer. What you end up with is an amazingly clear audio signal that can be picked up with a normal FM radio.

This would make a great project to do with the kids. You can talk about circuit design, practice soldering, and when finished they’ve got an almost miraculous toy to play with. Just be careful what you say around the house, the room might be bugged!