More Information About Software Defined Radios
Steve Cass's article Software-Defined Radio, Part II, is a follow-up to his article, A $40 Software-Defined Radio which describes his experiments using a RTL2832U based USB dongle designed for DVB/DAB reception as a software defined radio.
In Part II he outlines his experiences with the Ham It Up v1.2 – RF Upconverter For Software Defined Radio, which he used to enable reception of HF signals on the RTL2832U dongle. In the article he outlines the antenna and tuning network he used and what he found below 25 MHz.
Cass concludes: “Of course, I couldn’t talk back, as my setup can’t transmit. But there’s still pleasure to be had in extracting these low-power, long-distance voices and messages from the air. The Internet has made international communication trivial, but with radio there’s no gargantuan infrastructure: It’s just you and your little collection of electronics, the other person with his, and the living, crackling planet in between.”
Commercial Software Defined Radio Platforms Compared
The popular website Hackaday.com alerted me to Taylor Killian's SDR Showdown: HackRF vs. bladeRF vs. USRP. Killian compares five SDR boards ranging in price from $300 to $1,100 that offer sample rates from 20 Msps (million samples per second) up to 128 Msps. A major difference between these boards and the RTL2832U-based SDR implementations Steve Cass wrote about is that these sample rates are fast enough to allow demodulation and modulation (all of the boards include a transmitter as well as a receiver) of wideband signals such as TV and in some cases Wi-Fi. Simple size ranges from 8 bits up to 12 bits for the other radios, with a 14 bit option for the USRP B100.
I've been watching the increasing power and falling cost of these powerful devices. They could be useful for recording off-air RF for further analysis and perhaps even setting up a lab test of new transmission technology to see how changing modulation parameters affects performance. The price of these boards and the free open source software tools available make it possible for individuals and small labs to do experiments that would have been impossible using custom electronic circuitry or very expensive test equipment.
Examining the ‘Factories’ Inside Your Electronics Devices
This link is purely for fun.
Take a look at The Imaginary Factories Inside All Our Gadgets created by artist Jing Zhang. The website explains that’s it partially about how stuff works and part about “peeling back the layers” of popular consumer electronic devices to look at the “imaginary [and] whimsical factories within. This isn’t going to teach anyone how to tear down an iPhone or a digital camera, but rather “humanizes” technology by making us think of it more as a tiny factory with equally tiny workers.