When is a radio not a radio? When it's a cake? Well obviously, but it wouldn't be a Wireless Waffle article if it was about cake now would it? Waffles perhaps, but cake?

Anyhow the correct answer is 'When it's a Feynman Radio'. What, I hear you ask, is a Feynman Radio. In order to answer that we have to step back in time to the works of the Maestro James Clerk Maxwell. His Electromagnetic Wave Equation is the mathematical basis of all radio signals, propagation and so forth and desribes how radio waves travel.

Maxwell's equations (in common with many) square numbers before operating on them. One of the key numbers which is in Maxwell's equation is 't' standing for 'time'. The equations describe how Electromagnetic (radio) waves change with time. However, the factor which accounts for time is squared. Now this in itself may not seem important BUT the square of a negative number is the same as the square of a positive one. So, according to Maxwell's equations, a radio wave will look identical whether it has travelled 5 seconds forwards in time or 5 seconds backwards in time! Whoa! Hang on there a minute (or minus a minute). Does this mean that every radio transmitter emits two waves, one which travels forward in time and one which travels backwards? Well that's where Richard Feynman comes in. He argues that not only is this true, but that it is true of all atomic and sub-atomic particles and that for every occurance where something travels forward in time, the same thing happens and travels backwards.

But this is rubbish right? If it were true, we would be bombarded by endless radio signals and light beams from the future. This, argue many people, is evidence that the whole idea of signals travelling backwards in time is just a mathematical theory and not a practical reality. Others argue that the whole notion of 'deja vu' is a perfect illustration of why there must be a way of seeing into the future.

But maybe the fact that we can't hear 'backwards' radio signals is down to something much more straightforward. For example:

* Radio signals travel at the speed of light. Those coming backwards from the future would cross our own path going backwards at the speed of light. We, on the other hand are travelling fowards at the speed of light. Our paths, therefore, cross at twice the speed of light which means the backwards signals would be, to all intents and purposes, invisible.

* Radio signals travelling backwards from the future would be on negative frequencies. As all existing radio receivers only tune to positive frequncies, ie those above 0 MHz, we are unable to receive them. A receiver tuned to minus 900 kHz would presumably receive future radio broadcasts perfectly well.

Here at Wireless Waffle headquarters, significant effort is being put into the development of a negative frequency radio, or an 'oidar' as we like to call it. Using things such as negative impedance converters we are seeking to synthesise a capacitor of several hundred negative picoFarads and an inductor of the appropriate number of negative microHenries such that they resonate at a negative frequency. Using a 'edoid' we hope to rectify any signals recived to feed a set of headphones. A negative antenna (an 'annetna') is proving more difficult, however we believe that a modified slot antenna in which the radiating element is a hole in a plate of metal rather than a traditional antenna which is metal in the middle of a hole (eg free space) may just do the job. Burying the annetna underground may also help but until the whole receiver is functioning it will be difficult to check.

Occasionally Wireless Waffle has been known to produce a few spoof entries (especially around April 1st!) however the Feynman Radio is real (try checking on the web). Our attempts to develop an oidar however may just be a reverse-time echo of something we failed to achieve several years from now.