On Friday 15 October 2004 22:46, Trefor Roscoe wrote:
> Midge tried to but could not be understood :-)
>
> The signal is of course a wave and there will be harmonics in it. Some
> of these will sum and others cancel out.
Strictly, not harmonics.
In Physics at school we took hold of a long cord and waved an end of it up and
down, at a particular frequency you get a doubling, and the centre of the
cord ceases to move much, that is an antinode.
The classic experiment with two slits and a diffraction pattern has something
to do with the same sort of thing.
The wavelength of the radio particles is pretty short, and the two antennas on
a typical router eg Linksys WRT54G are a suitable distance apart that
hopefully you are at a node distance from one, if you are at an antinode form
the other.
But what with signal paths and reflections and refraction around objects, it
is not surprising if destructive and constructive interference produce dips
and peaks in signal strength in various odd spots.
Changing the radiation pattern from one of the antennas will commonly alter
that... and just boosting the strength may suffice to get contact.
On the receiving antenna, blocking out (attenuating) the half of the world
away from your transmitter's direction also may allow reception to work.
--
Adrian Midgley Open Source software is better
GP, Exeter http://www.defoam.net/
|