Those are for the DVB-T mode and not the debug mode that outputs raw samples.
For both kinds the tuner error is ~30 -20 PPM, relatively stable once warmed up, and stable from day to day for a given dongle. The RTL2832 ADC differential input impedance is ~3,300 Ohm.
The dynamic range for most dongles is around 45 d B.
It's from either the 1/f noise of the electronics or if it's a Zero-IF tuner (E4000) the LO beating with itself in the mixer.
My favorite way to explore the spectrum is using rtl_power to do very wideband multi-day surveys.
While the sampling bandwidth is only 2.56 MHz the frequency can be re-tuned up to ~40 times a second.
With frequency hopping you can survey very large bandwidths.This resampled output can be up to 3.2 MS/s but 2.56 MS/s is the max recommended to avoid losing samples. The samples themselves are unsigned and you subtract 127 from them to get their actual value.You'll almost certainly notice a stable spike around DC.(Datasheets, general ref: Quadrature Signals: Complex, But Not Complicated by Richard Lyons) This is complex-sampled (I and Q) by the ADC.The Sigma-Delta ADC samples at some high rate but low precision.patchvonbraun is the author and maintainer of the build-gnuradio script that made it easy for me, and multitudes of others, to get started with rtlsdr under GNU Radio. The R820T and R820T2 go from 24-1760 MHz (but with reduced performance above 1500 MHz).