# problem imagening the meaning of phase noise definition -70dbc/hz at 10Khz

#### yefj

Hello,From Wikipedia i have the following definition, but i cant imgine it.
Noise is not deterministic it has a variance and other properties of a random type.

dBc means ratio in amplitude between the carrier and some point
here we have some random thing so how ding /HZ helps us catch soe value from it?

Phase noise (ℒ(f)) is typically expressed in units of dBc/Hz, and it represents the noise power relative to the carrier contained in a 1 Hz bandwidth centered at a certain offsets from the carrier. For example, a certain signal may have a phase noise of −80 dBc/Hz at an offset of 10 kHz and −95 dBc/Hz at an offset of 100 kHz. Phase noise can be measured and expressed as single-sideband or double-sideband values, but as noted earlier, the IEEE has adopted the definition as one-half of the double-sideband PSD.

#### BigBoss

It's Average Noise Power measure in 1Hz Bandwidth.Random does not mean "non measurable".
Random Processes are characterized their "Average Values"

#### guntherleet

##### Newbie level 6
Its measure of PSD, think of regular WGN, its random in time but have PSD = const for all frequencies.