Noise source response

[eddiesomesan]

Im using a noise source which should go up to 1.5GHz without any problems. But by doing some tests in my frequency of interest, the response of the dongle/software is really strange. Instead of having a flat response, I have a drop of more than 5db/Hz on 100MHz interval and around 1 on 10MHz interval (140 - 150 MHz). Maybe Im do it wrong, but the response should be flat. Also, scanning without anything attached gives a nice (almost) straight line. Please see the attachments for noise source response.