From the HRO/AR88 to the RTL-SDR dongle and beyond!
by Mike G4GHL
Fifty years ago, every Short Wave Listener or Radio Ham would have a valve-based radio an AR88 or HRO etc, etc in the shack. Should that be studio rather than shack these days? However today you will more than likely find an RTL-SDR dongle or one of its upmarket derivatives in the studio of anyone interested in radio. Hidden away on a remote USB connection on the back of your computer quietly collecting radio signals from DC to a couple of GHz. All this from a package that would easily fit inside a single capacitor in an AR88. In the past we had a lot of fun “modifying” our communication receivers with a soldering iron. No chance of taking a soldering iron to a dongle these days but is there an equivalent route to having fun with your dongle today?
In this talk I want to try and bring the old and the new together. By reviewing the historical development of communications receivers from the early crystal sets to the “modern” superhet I will identify some features of their operation, including non-linearity, frequency multiplication(mixing), signal processing that they have in common with modern SDR radios such as the RTL-SDR dongle.
I will then describe the technological advances have made the RTL-SDR dongle possible and show how the spirit of “modifying” can still live on in the digital age by looking at GNU Radio software that lets you take charge of your digital radio.
Finally, I will go beyond receivers and take a brief look at digital transmitters. I hope that everyone will find something of interest in the talk whether they have been involved with radio for fifty years of fifty minutes!
Thursday 16th October, 7.30 for 8pm at the Premier Suite, Cheltenham Town Football Club, Whaddon Road, GL52 5NA. Visitors and prospective members will be welcomed.