|
Omnidirectional Patterns and dB
Q: I've been told that omnidirectional antennae will increase the range as the dB increases, but that the pattern gets flatter, and I may miss detecting APs. What does this mean?
A:For those of you who are scratching their heads over this, this may help visualize it better. Think of it this way: Omnidirectional antenna patterns are doughnut shaped. As you increase the dB rating, the doughnut's volume doesn't change, it gets flatter. It squishes flat. (yech!)
Here are two views of antenna patterns, a 5dB and a 10dB, using the same theoretical tx/rx point. ( BTW, not to belabor the obvious, but someone will probably point his out if I don't: The diagrams are not to scale with each orther.)
The top diagram shows the patterns from above, while the lower diagram shows the pattern from the side.
The black is the 5dB pattern, the blue is the 10dB pattern, and the red are APs that someone is trying to find.
AP1. Not detected. Within range of 10dB, but below signal area. Out of range for the 5dB.
AP2. Detected by 5db. Within range of of both; but only within the the signal area of 5dB. The 10dB would not have detected it.
AP3. Not detected. Within range of 10dB, but above signal area. Out of the range of the 5dB.
AP4. Detected by 10dB. Barely within range.
AP5. Detected by either 5dB or 10dB.
__________________
Thorn
"I'm The Doctor. I'm a Time Lord. I am from the planet Gallifrey in the constellation Kasterborous. I'm 903 years old and I am the man who is going to save your lives and all 6 billion people on the planet below... You got a problem with that?"
|