Listen to cops, pilots and truckers by turning your phone into the ultimate radio

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What is SDR?

SDR stands for Software Defined Radio. To understand how SDR works, let’s first explain how a radio system works. Just like the AM or FM radio in your car or stereo, you can send transmissions of music, conversations, and data over radio frequencies. When you tune to 95.5MHz on your FM radio, you’re tuning your radio to the 95.5MHz frequency, picking up the channel of your local radio station and its music. The handheld radios you see used by campers or law enforcement work the same way, tuning to a specific radio frequency that their devices are capable of from their internal hardware.

Software Defined Radio works the same way, but uses a computer to process the incoming radio signals instead of internal hardware. This gives access to a far greater range of frequencies, though most SDR systems can also cost hundreds of dollars. However, back in 2012 a group of hackers found a way to use the cheap, readily available RTL2832 DVB-TV adapter as an SDR. This RTL-SDR gives access to monitoring frequencies between 25MHz and 1700MHz, but costs only about $30 to create if you already own an Android device or PC. It’s also easy to get started with, since it only needs a USB adapter and some extra software. Look at the video below for a demonstration of RTL-SDR on Android:

Is this legal?

This is usually legal, but it depends on what you plan to do with your RTL-SDR. Here in the United States, the FCC allows you to listen in to unencrypted frequencies as long as you do not transmit, which isn’t possible with RTL-SDR anyway. It’s also important to check up on your local and state laws, as each area has different rules about how you can use scanners, especially if you plan to listen in to local law enforcement. Several states also restrict usage of scanners in vehicles unless you have an FCC amateur radio license.

It’s best to buy your RTL-SDR adapter from a trusted source to ensure you have ESD protection.

No matter what, do not use RTL-SDR to listen to GSM or cellular telephone frequencies. Although it is possible to reach these frequencies with RTL-SDR, the FCC forbids monitoring such communications, as well as attempting to listen into or decode encrypted frequencies. We know you wouldn’t try to listen in on people talking on their phones, but when in doubt, check the FCC’s spectrum map. The spectrum map includes an explanation of each frequency band and who is authorized to use it.

If you plan to use RTL-SDR as more than just a fun weekend project, we also recommend you consider obtaining a amateur radio license, which will allow you to transmit on certain frequencies. The ARRL website provides plenty of useful information to learn about getting an amateur radio license in the United States. If you’re just looking to get started and see what you can do with an RTL-SDR, then follow this guide to get started with RTL-SDR on Android.

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