[hpsdr] Janus Lives!!

[Alberto I2PHD]

Gerald Youngblood wrote:
> 
> There appears to be one problem with the measurements though.  The noise
> floor in the screen shots cannot be accurately calibrated since the 500 Hz
> RMS noise measures -159 dBm.  If you subtract 26 dB for the 500 Hz
> bandwidth, you get a noise floor of -185 dBm/rt Hz.  This is below kTB of
> -174 dBm/rt Hz.  That would equate to a negative NF (-11dB).  I would be
> interested in seeing the 500 Hz bandwidth shot after calibration with the
> radio attached.
> 
> 73,
> Gerald

Hmmm, IMHO those are not -159 dBm at a bandwidth of 500 Hz.... the bandwidth that must be considered is that 
corresponding to the bin width of the FFT that has been used to compute the spectrum.
The 500 Hz are the bandwidth of the audio filter, which has nothing to do with the FFT bin size.

73  Alberto  I2PHD

 1151947369.0