Jim Ahlstrom

PC board image

Hardware Projects

These are my published hardware projects. I use Eagle to design printed circuit boards. I make the simpler boards myself using pre-sensitized photographic PCB material. The image is laser printed to a transparency. I prefer surface mount devices because I do not have to drill the holes. I have more complicated or fine-pitch boards made by a PCB prototype shop, 4pcb.com. Again, I prefer surface mount parts because it is faster to solder them, and the zero lead length makes the RF design more robust.

SSB/CW Transceiver

My SSB and CW transceiver is my current Ham Radio station. It is based on an FPGA surrounded by an Ethernet controller, an ADC and two DAC's. The receiver digitizes the antenna voltage, and the transmitter uses direct digital conversion to RF. There are no analog mixers. This project was published in QEX magazine in the Jan/Feb 2011 issue. An improved version called the HiQSDR is available as a kit or a completed unit. See hiqsdr.org and technologie2000.de.

SSB/CW Exciter

My SSB and CW exciter is also based on an FPGA. The design is entirely digital. The output is generated by a DAC and there are no analog mixers. For SSB, audio data from the PC is sent to the exciter using Ethernet. For CW, the key connects to the hardware, the FPGA provides a shaped carrier at the output frequency, and the PC is only used to provide a sidetone. This project was published in QEX magazine in the May/June 2008 issue.