Problem with drifting noise floor when doing heterodyne signal measurement

[watertreader]

Hi,

I am doing some heterodyne signal measurement. However, I found that the noise floor seems to be fluctuating... ie it is rising up and down ... does anyone have the same problem?

Thanks

 

[cydi]

Drifting noise floor

please explain the setup, so that we can comment...

 

[A.Anand Srinivasan]

Re: Drifting noise floor

is it fluctuating at a single frequency or between different frequencies.... because each noise component has a different kind of variation with frequency and each component of the heterodyne setup may have different type of non linearity which also contributes to the noise....