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  • Author Author: 14rhb
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Software Defined Radio (SDR) - My First Design

14rhb

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

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  • I've played a bit with it... Its fun stuff... With the right antennas and equipment you can get weather sat images. There are many interesting things that are being transmited in air waves. For instance airaplanes and ships transmit their position, you can track them with an SDR. Remote controlled garage door signals can be easily captured and and replied. Then you have the HAM and other bands where you can hear people talking.  If you know a bit of modulation you can wit your own demodulator too!

  • in reply to neuromodulator

    I did find someone talking (seemed a bit one sided, unless they use different channels to transmit and receive) and I think it was probably a ham radio band as he mentioned 'modulation' and 'bands' - it seemed really odd coming from my laptop speakers. I should have noted the frequency as I could have looked it up.

     

    The aircraft and ship position data sounds really interesting, thank you - just the sort of thing I'd like to try and tune to and decode.

     

    Rod

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  • in reply to neuromodulator

    I did find someone talking (seemed a bit one sided, unless they use different channels to transmit and receive) and I think it was probably a ham radio band as he mentioned 'modulation' and 'bands' - it seemed really odd coming from my laptop speakers. I should have noted the frequency as I could have looked it up.

     

    The aircraft and ship position data sounds really interesting, thank you - just the sort of thing I'd like to try and tune to and decode.

     

    Rod

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  • in reply to 14rhb

    Ship tracking: https://en.wikipedia.org/wiki/Automatic_identification_system
    Airplanes: https://en.wikipedia.org/wiki/Automatic_dependent_surveillance_–_broadcast

    Try rtl_power to scan a wide spectrum of frequencies, you could generate something like this:



    You can use the SDR as a radar to... you can detect meteorites for instance and even compute their speed (through doppler), check this page: Rtl Power: Basic scripting.

    Need inspiration on what do do with an SDR? Check this:
















  • in reply to neuromodulator

    Wow, the meteorite detector would be so cool. I'll have to push that up the list of things to do.

     

    Rod