Software Defined Radio (SDR) - My First Design

This is a quick blog post about using my NooElec SDR for the first time.

Back last year I was luckily chosen to roadtest three Molex Antennas Molex 2.4GHz / 5GHz Antenna Kit - Review  and that re-kindled my interest in RF work at home. Wanted to have a 'play around' I bought myself a low-cost SDR for fun and it arrived today. It cost me just over £20 (UK) and plugs into the USB port of my computer plus it has a SMA connector for the antenna. I actually made a misjudgment and bought the basic unit before realising I didn't really have the bits to make a decent antenna but I have many plans to address that.

I initially ran this on my Linux machine - having downloaded the drivers and installed rtl-sdr and another package called Gqrx. That all ran really well and with a basic wire antenna I was able to tune to local FM radio stations and hear the music etc.

I then tried using the SDR with my Windows 10 laptop and installed the software described on the NooElec website called CubeSDR. That too was fun and I was able to scan the airwaves - looking at the signals in the frequency domain. The Digital Audio Broadcast (DAB) band looked particularly regimented - as shown below:

That was all fun but the SDR was being configured using the software and I had also read an article that mentioned I could make my own designs using the GNU Radio software.

I downloaded and installed that from their website and was met with a very interesting window....it then dawned on me how great this software was. I was going to be able to draw out the various block parts of my receiver to do exactly as I wanted. As a newbie I was going to struggle and so followed a useful online article https://www.instructables.com/id/RTL-SDR-FM-radio-receiver-with-GNU-Radio-Companion/  and, after some tweaks, I ended up with this:

And even using an out-of-band antenna (the Molex 433MHz from my kit) I was able to demodulate and hear a local radio station on my PC's speakers

All I can say is, I'm now hooked. I need a decent outside antenna (or two ) and a few connectors /cable length.

Browsing around at what I can pick up threw up some interesting links; apparently I can even receive the meteorological photos from an orbiting weather satellite. This needs a bespoke antenna but the design looks quite simple.

Rod