SDR radio, first forays

It was happy SDR day. I had squandered $18.00 of joint marital funds and had waited days for my digital equivalent of Ralphie's Little Orphan Annie's secret decoder ring to arrive. I was hoping the message wasn't going end up being something like "Drink Ovaltine." It was the best investment I have made in a long time, although I don't think Katie is as enthused at the cacophony of dronings, squawks, squeaks, beeps and hissing sounds continuously emanating from my office. The paltry funds have let me peer deeply into the mysterious world of radio frequencies which I haven't done since I built a crystal radio as a kid. What fun, but does it really work?

SDR, a $20 AIS receiver and more?

The answer to the title question is yes, and all with a small USB stick that was originally designed to do something else. It's a Software Defined Radio. Mine costs just $18.99 and had free shipping from eBay. The SDR dongle story all by itself is a testimony to very clever work repurposing an inexpensive mass-produced technology that had laid under everyone's nose for years. A DVB-T USB stick that decodes European digital TV signals has now become a radio with substantial RF bandwidth. Software driven radios earliest manifestations started in the 1970's. The SDR version I'm playing with had its first glimmerings in 2010, and today they are widely available for a very small price.

Add to this any of a variety of inexpensive antennas you can build yourself and what you can listen to is almost endless. The frequency range of this small device is 17MHz at the low-end up to 1750MHz. This allows you to listen to FM, but also aviation, CB, marine VHF and AIS, police and emergency frequencies, and even the audio from baby monitors. Add an upconvertor for about $50 and you can add shortwave frequencies into the mix. Want to amplify the signal from the antenna add another $30. We still haven't broken a $100 yet.