View Full Version : Question negative level
Tameem
2010-08-19, 06:59 PM
why is rx level is measured in negetive
Stantheman
2010-08-19, 07:15 PM
Tameem, do you mean as in receiver sensitivity, say -100 dBm etc ..??
If so, you should have a look at the following information:-
http://en.wikipedia.org/wiki/DBm
http://en.wikipedia.org/wiki/Decibel
Piscean21
2010-08-19, 07:57 PM
Because log of exponential having negative power is always a negative value say log of 10^-3 =-3.As BTS power is taken in milli Watts,thus levels are negative.
Hope this helps
Philster
2010-08-19, 08:08 PM
RF Power is referenced to 1mw = 0dBm
Hence 0.5mw = -3dBm, and 0.1mW = -10dBm
There are many references available on this site plus many others...
moslyi0891
2010-08-20, 09:25 AM
Watt is very huge unit
Watt was taken a s unit for measuring the transitted power .. and it is huge
so they use milli wat
then to convert from Watt to dBm you have to follow the formulla :
dBm = (10Log10(milliWatts)) so you will have absolutely negative value
Try to calculate any value through this formulla and you will have negative value
plannerguy
2010-08-25, 07:46 PM
Hi
Its due to the path loss which we face during the Transmission ....
we Transmit 43dbm from BTS end will have 3 db loss at jumper and 3 db loss at Antennna coupling so effective power out will be
43-3-3=37db
37 db this when having path loss ie Scattering loss, rayligh fading....etc which will be arounf 100db so power at MS will be +37 -100db=-63db
Regards
Plannerguy
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