Two  months ago we featured a transceiver based on the Microchip MRF49XA, and a lot of feedback was sent to [hpux735] requesting that some brains be added onto the system. [hpux735] decided that if he was going to do it, might as well go the distance and make a make a native USB transceiver.

The prototype model is designed for use with the Atmel AT90USBKey, and uses the LUFA USB framework. The protocol and packet format was revised, and a Hamming Code implementation was built using look-up tables to give error control. Finally once the prototype was ready to go [hpux735] created some awesome little PCB’s that contain the AVR, radio, antenna hookups, and blinky lights (no project is complete without blinky lights) are all ready to go when you are.

This project has come quite a long way, covers 3 blog pages, uses a fair bit of ribbon cable, but you just got to love when a plan comes together.

[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.

[Trax] sent in his writeup on this RF modem with built in 250mW amplifier. The original power of the RF transceiver was around 10mW, his final results after testing were nearly 250mW. He was able to to easily transmit data over 1000 meters using his test setup. He states that he was actually able to achieve this without an antenna on the receiving side. That’s pretty impressive performance. It’s also worth noting that he soldered all of the components in place using a home clothing iron and some soldering paste. That must have been fairly tedious.

Reader [Mike Y] responded to our “What are you working on?” post  with his stereo FM transmitter project. If you’ve ever used an FM transmitter for your portable audio, you know that even the best consumer level ones can be difficult to make sound decent.

He obtained an NS73M FM Transmitter module from Niigata Seimitsu Company, but it required a controller to handle pre-emphasis, modulation level, frequency, and power level. He decided on an Arduino which would also control his LCD.

His results were quite good, with decent range and superb audio quality. His total cost thus far is $35, but he still needs to put it in an enclosure. You can find complete schematics as well as source code and helpful tips on his site.  You may also want to check out the regulations on broadcasting(pdf) as well.