Software-defined radio

Posted July 2, 2008 at 10:16 am by admin in General.

Outside my job as project manager, one of the things I enjoy spending my spare time on is amateur radio (also known as ham radio). Because not everyone is familiar with amateur radio, here follows a short introduction.

In the Netherlands there are about 14,000 active hams. Hams come from all strata of society. Film stars, doctors, students, politicians, lorry drivers, in the world of radio amateurism you meet them all. Hams have in common rudimentary knowledge of radio technology and demonstrable knowledge of key concepts and rules through their obtained license. A license allows radio amateurs to connect with other amateurs through one of many designated amateur radio bands. This can be done through speech or data (Morse, telefax, packet, etc.) or picture. The bridged distance between hams can range from a few hundred meters to some ten thousands of kilometres. Established connections are of an experimental nature and are not permanent. Radio amateurism came soon after the first radio connection was established in 1901 by Guglielmo Marconi, and ever since there have been amateur radio operators.

Most wireless technology we find nowadays in everyday devices (remote control, mobile phone, WiFi, GPS, etc.) have their origin in radio amateur experiments. Hams play a key role in for example emergency situations when all other, regular communication networks fail. When that occurs, hams lead emergency services lead emergency services to the right location (speaking of the perfect back-up). This has often happened during the disastrous floods in Zeeland in 1953, but also during the Asian tsunami in 2004, and the terrorist attacks on 9/11 2001 in America.

Hams used to make their own equipment from any electronic parts they could get their hands on. Since the sixties of the last century, hams could also purchase turnkey radios, ready for use. Late eighties, these factory built radios contained gradually more and more computer technology. In the beginning just the frequency tuner (PLL) was computer controlled, later on the computer took over an increasing number of features such as control, sound filtering, etc. Many hams viewed this with suspicion. It was believed the soul of “self-built”, and with that the experimental nature of this hobby, was lost.

But as often is the case in most fields where computer technology enters, developments are unstoppable. Computers become ever more strong and compact, and it is now possible, with only a few electronic components linked to a computer, to simulate a complete radio (transmitting and receiving) by means of a computer programme. This is also known as software-defined radio (SDR).

The advantages require little discussion: a single set-up (1 computer with 1 ham) brings already countless advantages. After all, the computer can execute certain functions increasingly better as it is faster and more powerful. If this computer is connected to the internet and all visitors of a certain site can all listen to this ‘computer-radio’ (Web SDR) simultaneously, a world of new opportunities opens up.

One of the solutions hams have developed themselves, is being able to use the world’s oldest (government donated) single dish radio telescope (Dwingeloo Telescoop) in Drenthe simultaneously by multiple radio amateurs via internet. This enables hams to now listen to radio signals coming from space.

Thus, all radio amateurs (for or against growing computer impact on their hobby) must admit more and more possibilities arise.

Jim Nijkamp
Project Manager