SDR (Software Defined Radio)

Software defined radio (aka SDR), is a way of automating tuning into Audio/Digital radio receptions.

I am using a very simple (un-nervingly sensitive) USB dongle type RTL-SDR.COM

(cost inclusive antenna & mount was < £25).

This is able to tune through a huge spectrum of frequencies 0hz!! > 2.5Ghz

On a basic level it will tune into music radio ever where is the fun in that......

Also covers all the Radio Amateur bands , Dab radio and also Dab TV....etcetera

I am currently using a neat software package called SDR# (SDR Sharp), below gives an idea for what control you have over the RF goodness. (right view image for closer look).

The above Gui is tuned into the FM Broadcast band spectrum analyzer style, the colour frequency bands beneath it shows a running time graph of the signal levels, its useful when you are searching/tuning into data signals which just blip their short data packets sporadically (make it easier to home in on the signal).

I have been experimenting with tracking aircraft and can recommend RTL1090 by for simple quick data.

If you want a more portable system, its possible to connect the  SDR dongle to an Android device (via OTG connector/cable) .

So far my best recommendation is Avare ADB ,  when running, the receiver picks up the Planes Transponder data, giving various metric's of the flight.


Below you can see the airspace in my locality , this was just a quick test with buildings all around, as you can see it will detect aircraft up to 80kms.

(luckily for me Zurich, Friedrichshaven and Altenrhein airports are all within range .. \ü/ .. ).

Its also possible to pick up the International Space Station and also Weather Satellites, however that will take a bit longer for me to achieve.

The advantage of the RF SDF dongle is that its portable, i.e. no need for internet connections, un-tethers you from the Sky-Net . (some 4G bands are in range of this device, however 5G bands might be safe for a bit at least).

I have already a space for it in my "Zombie Apocalypse" rucksack, buy one today before they are outlawed (thats a serious prediction by me ;-)

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GroG's picture

Amazing post Gareth !I

Amazing post Gareth !

I better start stocking my cache in preperation against the zombie horde.

I found this list -

Quality and price are a consideration - although often become subjective, but frequency range might be one of the most important attributes ?

The  #1 top one has 1Mhz - 6 Ghz  which seems impressive - and is solidly opensource :)

#4 looks interesting and comes from seeedstudio - but is only 10khz to 30Mhz

oof ... $319 for the first one  ...   too expensive for me ..

2nd best choice .. Get what Gareth got ! :D

Done !

Gareth's picture

Nice list ;-) ... indeed some heavy prices

From that list I am tempted to get the :-

NooElec NESDR Nano 3 OTG  ($30 odd)

(number 9), looks the best space saving zombie phone attachment package there :-

Gareth's picture

Application notes for tracking flights... and spotting aircraft.

I had the "HUD's Up" and found out that the Swansea Wales Airshow was taking place..... using and an online wide angle Live webcam feed strategically looking down the flight path.... and Bingo... a Lancaster Bomber :-

Gareth's picture

Red Arrows --- flying under the radar

The Red Arrows are a Royal Airforce team of 9 aircraft - they did not appear on or the , they must have forgotten to turn on thier Transponders.... Gahhh (that would be a Zombie fleet if I ever did see).

Apollo formation


Concord formation


Goose formation