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Al's picture

Thanks Fraser glad you find the software useful, in fact I'm surprised at how many people do!

The reason I use dB/√Hz is really to reinforce the fact that this software uses Power Spectral Density analysis to transform the received bandwidth from the time domain (i.e. amplitude vs. time) to the frequency domain (amplitude vs. frequency), as many programs use a standard FFT instead.  PSD has a few advantages especially when it comes to stitching frequency ranges together.

The square root can be ignored as the analysis is scaled to 1Hz, basically meaning that the value is the power of a particular frequency per unit frequency.

On top of this the dBm unit is the ratio of power referenced to 1mW (decibels are just a ratio, not a unit) and the gain of dongles is not created equal (even sometimes between identical dongles).
Because of this I decided to use ratios (the decibel) rather than an absolute unit (dBm) because of the variation in tuners.

To sum-up: treat dB/√Hz as just decibels (e.g. a signal which is 6dB lower than another is about half the power); don't worry about it as an absolute value.