I have a quick question for the group about the noise floor of a spectrum analyzer, hope that with the collective knowledge and experience somebody can help me out a bit.
We have customer that needed a couple of site surveys done, in order to detect any possible interference sources on 3 segments of 2MHz each (we used the 200KHz/div screen span setting), in the 455-465MHz region. Surveys have already been completed, but the customer is now asking us to redo a few of the site surveys that didn't catch any interference because the noise baseline on the instrument that was used is -110dbm. The customer says he needs it done at a noise floor of -124dbm to make sure the frequencies are really clean. Could anybody clarify how one does lower the noise floor of the analyzer? It was my understanding that the noise floor is a intrinsic characteristic of the instrument itself, and is so to say a measurement limit that cannot be varied without external aids (or maybe with a low-noise LNA?). But if one uses an external amplifier, wouldn't this also raise the site noise floor on the analyzer screen? Or if I am wrong, how could one lower the noise floor of the measurement in order to be able to take measurements at lower levels? Or is the noise floor also a function of the SITE noise level per se? BTW, we used a IFR (Aeroflex) COM-120B during the surveys, coupled with the EasySpan II software to make the screen captures. Thanks. -Alex
