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I've been monitoring a signal locally on 159.150mhz (which is allocated for "Civil Defense"). I believe that this frequency is for the local tornado sirens and I would like to be able to decode the transmissions.

Anybody have any ideas on what this signal could be and the steps I could take to decode it?

Here's the signal: Recording 1, Recording 2

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If you can record a waterfall plot of the signal (the easiest way is via a cheap sub $20 RTL-SDR dongles, as @user3431540 mentions), you might have some luck identifying the signal visually via the brilliant Signal Identification Wiki.

Here for example is a waterfall plot for APRS:

APRS waterfall plot

In fact, some software may even allow you to create waterfall plots from recorded sounds, or by placing your computer mic next to the radio speaker.

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The first one sounds like standard 1200bps packet radio (AFSK). The second one sounds similar, but using slightly different frequencies.

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Many affordable USB Software Defined Radios (SDRs) may be able to help you.

https://www.adafruit.com/products/1497

You would likely need a free tool called "Zadig" to get the drivers working. And there are many blogs such as http://www.rtl-sdr.com/ which offer reviews of software tools for decoding various signals.

It wasn't clear from your question what sort of setup you're using to capture the signals, but getting them into the computer would likely be the first step to decoding them.

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