# When to use raw signal strength, vs. when to filter first

I am collecting I/Q samples from an RTL SDR dongle.

I notice the rtl_power utility provided for Linux filters and does other processing, before reporting signal strength.

I just want to keep track of how strong a frequency range is (eg. a 25k bin, as passed to rtl_power).

Can I just square the I and Q and add them, or do I need to do the filtering and other processing that rtl_power does, first? What's appropriate in what situations?

• well "what is appropriate in what situations?" is kind of a big question, considering there's an infinite amount of different situations. Maybe you could explain for what purpose you want to measure signal strength? – Marcus Müller Jul 6 '16 at 7:58
• @MarcusMüller - I would like to find peaks ("activity") in a user-defined frequency band – horse hair Jul 6 '16 at 15:59