The Elecraft N-GEN is a low cost noise source which is quite suited to many applications, more so if the Excess Noise Ratio (ENR) is known.
ENR is a commonly used property to describe the noise power density of a source, it is calculated as ENR=10*log(Tne-T0)/T0 dB where Tne is the quivalent noise temperature and T0 is 290K.
This article describes a calibration procedure. Note that the calibration is specific to the device and cannot be applied to another N-GEN.
Above is a screenshot of the Spectrum Analyser scan. A text file of the frequency,power pairs is saved for input to a spreadsheet to calculate ENR vs frequency.
ENR=10*log(10^((P-30)/10)/(290*K*B)-1) where P is rx power in dBm, K is Boltzmann's constant and B is measurement bandwidth.
Above is a plot of the measurement data and an interpolated curve.
The N-GEN output is sensitive to voltage, and this one is modified to use a little regulator to supply a constant voltage to the N-GEN from an external source.