== Circuit Lover's Blog ==

Hello World in SDR

sdr radio

Update 12-Sep-2022

My RTL-SDR order on Amazon was cancelled due to some transit problem. I’m waiting for refund 😕. After I got my refund, I’m hoping to buy RTL-SDR directly from the Website. Since RTL-SDR have only reception capability, I’ve also applied for HackRF as free stuff in Great Scott Gadgets. I hope, I’ll get some positive response.

Original post on 3-Sep-2022

Recently, I got hands-on with an SDR (Software Defined Radio) in my college lab. It was a great experience. I will briefly talk about it here.

First, what is an SDR? It stands for Software Defined Radio. As the wireless innovation forum states that the Software Defined Radio means:

“Radio in which some or all of the physical layer functions are software-defined.”

In simple terms, it is a radio system, which we can have control over it by manipulating the software alone without the need for manual intervention with the hardware part. For example, you can use the SDR as an FM receiver, and also as you can use it to decode data from a weather satellite just by changing the software without the need for hardware modification. Thus it outweighs the traditional radio hardware by reducing the manufacturing cost and offering flexibility over different wireless standards.

The software part of SDR can sit on your computer or any SBCs (Single Board Computer, like Raspberry Pi, etc.) and utilize the general-purpose computing resources for a significant amount of signal processing work. So, a basic SDR system may consist of a personal computer equipped with a sound card or another analog-to-digital converter, preceded by an RF front end, connected to the computer through USB or Ethernet. Look at the picture below for more understanding.

SDR Architecture
Block Diagram of SDR

Next, let’s talk about the software part. The software programs are widely available for SDR with support for most of the available hardware. The most common one is GNU Radio. It is a free & open-source software development toolkit. It can be used with readily-available low-cost external RF hardware to create software-defined radios or without hardware in a simulation-like environment. It is widely used in research, industry, academia, government, and hobbyist environments to support wireless communications research and real-world radio systems.

For starters, you don’t need to type any program, but what you need most is signal processing knowledge. Instead, you can easily pick & place readymade blocks and connect them. Then, run, BOOM 🔥, it will work. It is similar to Matlab’s Simulink tool & Ni’s LabVIEW, but it is Free and Open-Source Software (FOSS). When you hit run, it simply creates a python program. So you can even execute the python code seperately. See the below image for the FM receiver.

FM Receiver in GNU Radio
FM Receiver in GNU Radio
You can also invoke GNU radio through the command line (for advanced users). It also has lots of resources and guided tutorials for all levels of users.

Ok, let’s get over to the part of hello world in SDR. In my college, we have a USRP B200 SDR from Ettus Research (they forgot to buy an antenna, so it is in the showcase 😜 ). But I got my hands on it since it is part of my curriculum. And after I finished installing drivers for the SDR, then checked whether my laptop recognized the SDR. It’s a green flag. So I opened the GNU Radio companion (GUI mode for using blocks, as said earlier).

The GNU radio has better support for Ettus SDRs. I just connected the blocks for the FM receiver and executed it. Then, BOOM 🔥, I know it won’t work because there is no antenna.😆 So I attached a jumper wire to the antenna port (Anything that radiates electromagnetic waves is an antenna). Since the FM signal is strong around my area, a simple wire can receive the signal with affordable noise. I heard my local FM station (93.5 MHz) broadcasting a famous Tamil song by Oscar Winner A.R. Rahman. It has more noise but a decent listening experience. Making an FM receiver is “Hello, World” in SDR, similar to programming. I wanted to dive into the SDR hobby and ordered my first low-cost SDR. Once I get my hands on it, I will experiment a lot and share my findings here. If you are interested in radio, you should try it too.

Today’s Quote Lines

Getting invloved means activity: heads down. hands dirty

- John Mason, Leone Burton and Kaye Stacey 1

  1. Referred it from the book of “i want 2 do project. tell me wat 2 do” by Mr. Shakthi Kannan ↩︎