# Estimating signal strength from PCM-encoded signal

I am processing rtl_fm output (in time domain), extracting Manchester encoded bits. I can detect preamble and, therefore, decode the message which follows the preamble. This is how my signal looks like (here I have 2 messages, the rest is noise):

And this one of the messages zoomed in:

Now I want to know how strong was the signal that I've just decoded. I know what is the average amplitude for my symbols: "1" is 2900 and "0" is 1500 (for the amplitude range of -32768 .. 32767). Is it possible to know the signal strength in dB in this case?

• baz is right. you need to know what gains the pre-amp to the ADC have and you need to know the $V_\text{ref}$ of the ADC. and the way to sorta skip over all of that is to measure a few sine waves at different frequencies, both at the input with a scope and with the digital display you have shown in the question. that should give you a pretty good absolute reference. – robert bristow-johnson Jan 24 '16 at 0:23