Gnuradio/Wav to Waterfall
From charlesreid1
This covers my first foray into signal decoding with SDR and gnuradio.
Recording the Signal
I basically wanted to record a signal from an Amateur Radio WebSDR station, and figure out how to import it into gnuradio for signal analysis. Recording the signal was easy - the web interface actually has a recording capability. So it's as simple as clicking a button.
But these WebSDR recordings were single-channel. Then I found an observatory that provides SDR data that's two channels, and a higher sample rate: http://to117.aai.ee/public_to117/Obs/SDR/HighRPM/Dish/
The Wav File
Okay, now I had a wave file with a recording of a signal. But what information was contained in the recording?
Getting Info about the Wav File
You can use the mediainfo utility to get some info on the wav file:
mediainfo HDSDR_20140505_180828Z_437209kHz_RF.wav General Complete name : HDSDR_20140505_180828Z_437209kHz_RF.wav Format : Wave File size : 311 MiB Duration : 3mn 28s Overall bit rate mode : Constant Overall bit rate : 12.5 Mbps Audio Format : PCM Format settings, Endianness : Little Format settings, Sign : Signed Codec ID : 1 Duration : 3mn 28s Bit rate mode : Constant Bit rate : 12.5 Mbps Channel(s) : 2 channels Sampling rate : 391 KHz Bit depth : 16 bits Stream size : 311 MiB (100%)
Now we'll be able to use gnuradio to feed these two channels of sound data into a radio spectrum visualizer.
Using the Wav File in Gnuradio
You can use the wav file as a source of sound data by using a "Wav File Source" block. Double click on the block, and pick your wav file to associate it with the block.