Trefor Roscoe wrote:
> David Evans wrote:
>> On Thu, 11 Mar 2004 15:50:58 -0000, Robert Treharne Jones
>> <[log in to unmask]> wrote:
>>
>>> Has anyone else tried that trick they showed on Top Gear a few weeks
>>> ago where, if you're too far from your car and the remote
>>> lock/unlock doesn't work you fire the key at your head instead,
>>
>> Surely your body is acting as a antenna. The same thing happens with
>> receiving if you touch the aerial socket on a TV or hold the
>> telescopic aerial of a radio.
>>
>> David
Thinking about this over the weekend I remembered an experiment from Physics
where we had a lens of wax and used it to shape a radio transmission at
1.5cm wavelength to produce a beam. If the wavelength of these transmissions
are similar, usually the screw holding the package together is the aerial,
so assume a 1/4 wave dipole and look at the screw one finds that a very
close fit. Then the part of your head that is solid ( brain ) is an
approximation to a thick convex lens, it will act as a wave modulator
(shaper) to bend radiation that would have travelled substantially up or
down to travel more in a horizontal plane, The experiment is to find the
range at which this just works and then lie down in the street ith your feet
pointing at the car and see if it still works. The second test is to see if
the maximum achieveable range with this technique is when the key, head and
car are in alignment in that order. If the first test lying the car fails to
open and the second test is true then there is some support for this
hypothesis. Sorry cannot test it as my car does not have such a gadget!
- -
Alistair
|