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dBi Calculation Question

Guys I am working on my CWNA paper and have hit a little point that I cannot get beyond (although you will probably think this is pretty simple).

It is the calculation for a circuit as below.

RF Circuit

AP--connector (A) -----Cable----Connector (B)----cable---- Connector (C)---Antenna (D)

AP is 100mW and the paper is explaining the calculation as below.

AP Point A Ponit B Point C Point D

100mW -3dB -3dB -3dB +12dBi =100mW /2 /2 /2 (x2x2x2) =100mW /2 /2 /2 x16 =50mW /2 /2 x16 =25mW /2 x16 =200mW

It was my understanding that all dB units (including dBi) are relative units and can be added and subtracted from other dB units - therefore the overall dB should be +3db = doubling the power - hey presto the right answer!

What I cant fathom is the calc shown above - why have they suggested a multiple of x2x2x2 ?

Can someone please explain why......only a little point but bloody annoying when your are learning this stuff for the first time!

Thanks

Reply to
Rob D
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What they are showing is that 100mw/2 = 50mw, 50mw/2=25mw,

25mw/2=12.5mw which is = to -9db

the x2x2x2 means +12dbi would take the 12.5mw x 2= 25mw, 25mw x

2=50mw, 50mw x 2 = 100mw = up 9db, just where it started. plus 3 extra dbi = 200mw

Make since.... you are right in your calculation, there is a +3db gain, started with 100mw,,, now x2 = 200mw

relative

therefore

Reply to
Airhead

suggested

This should probably say x2x2x2x2. Are you getting this from the CWNA study book? Is so what version?

Reply to
Airhead

pretty

below.

bloody

I just checked my CWNA second version and it says x2x2x2x2

Reply to
Airhead

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