Wireless signal strength db
When measuring cell signal strength dBm is also used, after all, it is a radio signal, and though of a different frequency from WiFi its strength can be measured in the same way, because the signal strength is independent of its frequency. For example, 20dBm is the increase of 20 decibels which are 2 bels, so it is a 102, or in other words a hundredfold increase. Thus converting decibels to bels is a useful quick hand way to calculate the gain or loss of power, by calculating 10 to the power of bels. 20dBm signal is a tenfold higher power than 10dBm, 30dBm is tenfold higher than 20dBm, and so on. For example, a 10dBm signal is ten times stronger than 1 milliwatt, which is 10 milliwatts. With each 10dBm increase signal strength increases 10 times, and with 10dBm decrease signal strength decreases 10 times. Decibel is one-tenth of a bel, this is very handy to understand when trying to figure out what some number like -20dBm means.ĭecibel-milliwatts describe the numerical factor by which signal power is higher or lower than 1 milliwatt signal. For signal strength dBm is used because it offers a handy level of granularity of measurement. Otherwise, let me try to explain it with a bit more words. If you have math knowledge about logarithms, the simplest explanation is that decibel is the base-10 logarithm.
In technical documentation of WiFi repeaters, you will find gain expressed as a positive value, because it is a measure of amplification of the signal strength. That’s why when measuring in dB signal strength you will see negative values, it is a measure of the factor of decrease compared to the reference value of 1 milliwatt. WiFi signal when the router’s antenna emits starts losing its power as it travels to your device.
The physical nature of radio wave signals is that their power decreases with the distance they travel from emitter to receiver. WHY SIGNAL STRENGTH MEASURED IN dB IS ALWAYS NEGATIVE? The absolute measurement in watts or milliwatts would be meaningless and would require measuring signal power at two points. When diagnosing the quality of the WiFi signal strength dBm measurement shows how much the signal’s power decreases. This is the most important thing to understand because for signal strength dBm is very useful to understand the signal strength loss or gain when using a device such as a WiFi booster like RangeXTD. WHY SIGNAL STRENGTH IS MEASURED IN dB?įor signal strength dBm is a very useful unit of measurement because the power of radio signals changes logarithmically with the change of distance between transmitter and receiver. With decibel-milliwatts signal, power is not directly expressed, but the ratio between the strength of 1 milliwatt signal and the measured one. Instead, it describes a ratio between two values. But what a signal strength dBm measurement then actually describes? Because the dB scale is logarithmic, it is used to easily describe both very large and very small values.Ī decibel is a dimensionless unit, which means that it does not have a physical dimension associated with them. In short, dBm or decibel-milliwatt is a unit used to describe signal power level in decibels in relation to 1 milliwatt of energy. So, here’s an in-depth explanation of what it is and what it has to do with the signal strength. Very often you will find in various documents related to WiFi documents various positive or negative values expressed in dBm. WiFi uses radio signals for transferring data wirelessly between computers and other devices. You probably have asked yourself why when measuring signal strength dBm is the unit of choice? Or why is dBm signal strength always expressed as a negative number? Or what is dBm to begin with?