- February, 2021
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Hey, did you hear about SDR? Do you know how it can be used or what does it stand for…?
Here, we can reveal you some information about radio signals so you can check and test out by yourself too… We won’t go deeply too much into the terminology, so if you come across with some questions, we shall leave that up to you to do a research with few links left behind.
“The SDR or Software Defined Radio represents a radio communication system which uses software for the modulation and demodulation of radio signals. The SDR performs significant amounts of signal processing in a general-purpose computer, or a reconfigurable piece of digital electronics. The goal of this design is to produce a radio that can receive and-or transmit a new form of radio protocol just by running new software…” 
So, let’s quickly observer the general diagram of signal the processing of the SDR Architecture. The image below illustrates what kind of process received signal passthroughs and processes by the hardware components.
The Diagram of the SDR Architecture 
In order to receive the RF signals you would need an antenna connected to some input of the RF hardware device. This hardware device represents a group of embbeed chipsets that listen for a various RF specter of signals and passthrough it to the other components that do the processing, filtering, decoding, converting, amplifying… them. [Have a peek on the components that are being used on the hardware device: superheterodyne receivers use a variable-frequency oscillator, mixer, low-noise amplifier, analog-to-digital converter and filter …] As final result, you get a human readable data. (video, audio, text….. – data)
So now that we have shortly peek to SDR architecture, we can continue on with the next part…
What is the RTL-SDR? [ hey, now we know what SDR stands for…]
In order to catch/listen the RF signals, you would need a PC/laptop or compatible mobile device. [You might already have it on the PC as TV/FM card slot or some portable USB tuner if not don’t worry].
Let’s go back to our story…
Recently we have discover a blog page that has been making some of this hardware device that comes up with useful open source applications that have a goal to process various band of RF signals controlled by user it self.
As for the starting point, we can point you to the RTL-SDR to look further.
Welcome to the world of RF the RTL-SDR.COM.
What is the RTL-SDR …?
“The origins of RTL-SDR stem from mass produced DVB-T TV tuner dongles that were based on the RTL2832U chipset. With the combined efforts of Antti Palosaari, Eric Fry and Osmocom (in particular Steve Markgraf) it was found that the raw I/Q data on the RTL2832U chipset could be accessed directly, which allowed the DVB-T TV tuner to be converted into a wideband software defined radio via a custom software driver developed by Steve Markgraf…..”
On the RTL-SDR you can find a lot information about various receivers. The device can be used as a computer based radio scanner for receiving live radio signals in your area (no internet required). Depending on the particular model it can receive frequencies from 500 kHz up to 1.75 GHz. 
And now we come to the interesting part. What can you listen….?
Here is the short list:
• Listening to FM radio, and decoding RDS information.
• Listening to DAB broadcast radio.
• Watching analogue broadcast TV.
• Using rtl-sdr on your Android device as a portable radio scanner.
• Receiving GPS signals and decoding them.
• Using rtl-sdr as a spectrum analyzer.
• Receiving NOAA weather satellite images.
• Listening to satellites and the ISS.
• Tracking and receiving meteorological agency launched weather balloon data.
• … and much more….
We hope that you find this article internsting, so we encoruge you to continue exploring if you love playing with the system and signal anlayzing…
1) https://en.wikipedia.org/wiki/Software-defined_radio – Software Define Radio
2) https://www.rtl-sdr.com/about-rtl-sdr/ – RTL-SDR.COM
Author: Nenad Todorović, Android Software Engineer at enjoy.ing