passive reflectors

[Brad Hards]

On Tue, 11 Jun 2002 10:59, Chris Hill wrote:
> Hi Drake,
>
> The main typo was about signal drop versus distance.
>
> The correct statement is:
>
> Every time you double the distance, you lose 6dB.
>
> There are a few assumptions behind this, but it doesn't get any better than
> that statement... only worse.
Not quite complete, especially in complex structures.
Loss comes down to two parts
- large scale fading (the so called "free space loss"), described above, and 
the number vary according to how you're calculating it - don't mix comms and 
radar people :) 
- small scale fading. If you've had a commercial radio receiver in a tin shed, 
then you know that moving the radio just a little bit can make the signal 
either disappear, or boom in. You can see this effect on the signal strength 
sometimes - just moving a few centimetres can make all the difference. This 
is really important in most houses, especially for people who have metal foil 
in the roof (or a metal roof). The physics is easy, but the result in a 
complex structure is a almost always a "suckit-n-see" approach. Sometimes 
small scale fading can help you (when you get a couple of reflected waves 
adding to signal power) - rare though.
-- 
http://conf.linux.org.au. 22-25Jan2003. Perth, Australia. Birds in Black.