How does SDR work?
A typical SDR system has two main parts:
1. The Hardware Front-End:
- This is the physical piece of hardware you connect to your computer (often via USB) or that exists as a card inside it.
- Its main job is to act as an Analog-to-Digital Converter (ADC) for receiving signals. It takes analog radio waves from the antenna, converts them into digital data (1s and 0s), and sends this stream of digital data to the computer.
- For transmitting, it does the reverse, acting as a Digital-to-Analog Converter (DAC), taking digital data from the software and converting it into an analog radio signal to be sent out the antenna.
- Examples: Popular low-cost SDRs like the RTL-SDR dongle, or more advanced units from HackRF, BladeRF, and USRP.
2. The Software Back-End:
- This is the program running on your computer that processes the digital data stream from the hardware.
- The software performs all the traditional radio functions: tuning to a frequency, filtering out unwanted signals, demodulating (decoding) the desired signal (e.g., turning FM into audio), and decoding the information (e.g., turning digital data into text).
- Examples: GNU Radio (the most popular, open-source toolkit), SDR# (SDRSharp), HDSDR, and many others.
