III. Wireless LAN

Fitting potatoes to your WiFi Antennae

A Wireless LAN device uses microwaves (most often in the 2.4Ghz band) which are very close to those used by microwave ovens, therefore, you've probably wondered whether you can cook a baked potato on your WiFi base. To address the literally thousands of queries we've had on this subject but also to explain why WiFi has a limited range, and to finally provide a scientific answer to the question of what would happen, we've put together this guide.

How does a microwave heat?

A microwave oven works by water within food absorbing the microwave energy, which causes dielectric heating.  Put simply, as the polarised signal hits the water, molecules in the water align themselves with the signal - like a compass needle reacting to a magnet.  As the signal is oscillating, the polarisation is continuously reversing. This causes the molecules to switch back and forth, re-aligning with the signal as it changes.  This rapid agitation of the molecules causes friction, which generates heat. Therefore, all of the signal power is converted to heat, so you get a nice hot lasagne.   Water is  the necessary dielectric material which is why you will have found that , you cannot heat things such as paper or skipping ropes as the materials do not absorb the waves.

What limits a WiFi signal?

In a perfect but possible scenario, a WiFi signal will give up to 200M of reliable coverage (there are lots of assumptions in that estimate). The reason for this limit is down to physics but more specifically a phenomenon called path loss.  Path loss is the weakening of a signal strength as you travel further away from the source. This loss is caused by various factors, but one of those is the absorption of the signal by moisture (water) in the air. The water in the air turns the signal into heat, so there's less signal power.  The power of a wifi device is relatively tiny, so you're not going to notice it - the effect is tiny.  This explains why in space, where there is no air and no obstructions, a signal can travel millions of miles from a remote probe back to earth.  There are other factors in path loss (such as the expansion of the wave 'sphere') but water in the air is the factor relevant to potatoes.  In our tests, at 5 meters distance, we found that a pair of potatoes caused latency to increase by a factor of 4 and TX throughput to decrease also by a factor of 4.  RX throughput did not vary as much.

Can you cook on a wireless access point?

A WiFi device uses signal strengths thousands of times smaller than a microwave oven (e.g. 1200W vs. 0.5W) and a microwave oven keeps the signal within a very limited space to have a heating effect. It needs sufficient power to heat the food faster than it can dissipate the energy and maintain itself at room temperature.  A WiFi device just can't do that. If you leave your potato on your WiFi base, it will never cook. It will go mouldy and it will dry out, but it won't cook.  

Is WiFi dangerous?

Some people argue that the electromagnetic soup we all walk around the streets in today must be bad for us, though there seems to be little justification for that assertion. According to the World Health Organisation, who have collated many different studies "there is no risk from low level, long-term exposure to Wi-Fi networks".  Another independent study, in the UK, concluded "RF field exposure below guideline levels does not cause symptoms and cannot be detected by people, even by those who consider themselves to be sensitive to RF fields". Some people do indeed claim to be sensitive to EMF,something they call Electromagnetic Hypersensitivity - a condition which has been universally dismissed by the medical community.  Of course, science and scientists cannot prove something doesn't exist - they will only ever cite what they can prove does exist, or that that they cannot find anything to support the existence of something. In France, with a  'better safe than sorry' policy, WiFi is prohibited in pre-school nurseries (do many toddlers use WiFi?).

Occasionally, a new report, or a sensationalist headline claims to have found 'risks' but I'd urge you to read beneath the headlines.  Other people, whilst conceding that there is no currently evidence of risk or harm from RF signals despite countless studies, suggest that it takes decades to see the effects.   We're not scientists - you can read lots of qualified opinions elsewhere, and even more unqualified opinions too! 

Conclusions

Putting a potato on your antenna does not improve your signal; it will substantially reduce it.  Whilst that might be desirable in some circumstances (limited range to a very localised area), a potato is a poor method.  It will dry out and go mouldy quite quickly (hence reducing the effect).   A carrot, is shaped more like an aerial but contains less water and is thinner so would be less effective but last longer.     We were hoping to keep the test potatoes and give them away as a prize (the DrayTato!), but someone ate them. It's what they would have wanted.

Next : Why you might not want that government issued app on your phone...