Reference level switching-error vs IF-gain uncertainity

Hello All,

I need to understand noise floor concept in Spectrum Analyzer. My spectrum analyzer has a
Noise Figure = DANL of system [dBm/Hz] - Thermal Noise (-174 [dBm/Hz]) with a DANL of -152dbm/Hz

so a nf=22db

As I change the vertical scale and reference level of the spectrum analyzer, its noise floor is dropping also; and its written as dbm. When I put vertical level at 150db and reference level to -50dbm; its noise floor is down to -160dbm. However, it confuses me if that's just a graphic bug; or real noise floor.

1- Termination with 50-ohm ends up with the referenced levels of floor when observed with Span=1khz and RBW=1hz

2-When I connect DUT onto it, with low reference level everything on screen gets weird; but when I choose high reference level; then floor gets higher.


I read about the function of reference level in some places; but it's not clear in my mind.

Any comments are welcome.

Kind Regards,

ktr

Check the attenuation. The default attenuation is automatic, if the reference level is higher, attenuation will bet set to higher automatically.