John's Musings

Yeah, Me Neither

Software Defined Radio

Software Defined Radio - What is it? Most of us think of it as a hardware device and it is but it passes many critical functions off to the host computer and as the name implies most of the magic happens in software. We're going to focus on something called RTL-SDR which is usually a USB device that contains an RTL2832U chip. These are usually TV Tuner devices. But they do much, much more than act as TV Tuners. Much more. There is a list of items a simple $20 USB RTL-SDR can do on this page. This is the most concise list I have seen to date.


The RTL-SDR can be used as a wide band radio scanner. Applications include:

Look at that list. That's insane. All that stuff you can do with this:

Here's the quickest of the quick things you can do with it. Download a program called GQRX. Plug stick into computer (I'm using a Mac). Select the stick in GQRX.

Tune into a local FM radio station. Make sure that MODE is selected to FM Mono or Stereo. You need a faster computer to do stereo.

Now with a proper antenna you can listen to Police, Fire, Aircraft, Ham Radio Operators, CB Radio, Baby Monitors, Cordless Phones, Satellites (not kidding), the International Space Station (so not kidding), Boats, Weather I said.....this is insane.

I have a handheld antenna tuned to about 138 MHz. I can use software (GPredict) to track satellites then when, say a NOAA weather satellite comes overhead I can download and decode the signal which turns into that picture you see on the Weather map on the news every night. YOU CAN DO THIS IN YOUR OWN BACKYARD.

Here's a pic of Tropical Storm Cindy sneaking up on Louisiana.

Here's another thing you can do. Track Aircraft. This is done with a Raspberry Pi and an RTL-SDR. These are the planes flying over my house as I type this. Pretty cool, huh?

Get a load of this. Many cities and their provided services (EMS, Police, Public Works, Fire Dept. etc) have gone to digital trunking radio systems. No longer will your old analog police scanner catch all the conversations unless it can be programmed to follow the trunked radio frequency changes. An RTL-SDR can also do Trunked Radio. Absolutely amazing. A scanner that listens to all city services for $25. That my friends, is a bargain.

Now picture this. The shit has hit the fan. There's no power but you have a generator and can charge a laptop. You have a TV Tuner, FM Radio, Aircraft Tracker, that by God can tell you if terrible weather is inbound. I would say this is much more than a hacker toy. This is a vital piece of survival equipment.

Actually I'm not totally sure you can watch TV on this as it is a PAL receiver and the US uses ATSC. I guess you could get an up converter or you could just buy a US TV tuner USB stick for another $30 or $40. I have a Hauppage 955Q. Most laptops have multiple USB ports. SDR in one, TV Tuner in the other and you are ready for any emergency.

Anyway you NEED one of these. You don't just want one. You really need one of these.

Although I'm not a preparedness guy I wrote an article once for a cool website called It's pretty similar to this page but goes into some more specific details.

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