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By Ezurio Ltd., A Unit Of Laird Technologies

"How far will it go?" That's normally the first question that a user of short range wireless will ask you. We've grown accustomed to the radio standards that rely on infrastructure, such as mobile phones, FM radio and Television working wherever we are, but for most of us the first experience of a personal area wireless technology can be disappointing. If you've installed a wireless LAN at home you've probably wondered at the discrepancy between the 100 metre range it claims on the box (albeit with a small print caveat) and the difficulty in penetrating more than 5 metres to your bedroom or kitchen.

It's always been said that radio is a black art and range is one of the areas that still seems to live up to that description. Although radio is portrayed as a medium that can effortlessly pass through walls and ceilings, the reality is that every obstacle is likely to diminish the signal, or cause reflections that will generate interference. In both cases, you lose. In most cases, both effects occur and you lose twice. The problem for manufacturers is that none want to sell their product with a real-life worst case figure of 5 metres range displayed on the box, not least when a competitor may be selling an identical or even lower specification product with a claim of 100 metres. So everyone resorts to a white lie.

That small white lie goes back to the first principles that were the starting point of the relevant specification and which try to explain the relationship between the power produced by the radio to its range. In the open field, which is where most radios are characterised, the output power is linked to the total range. The Open Field Measurement is exactly what it says. Radio engineers take their products into large fields and test them where there are no obstructions.

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