RTL-SDR

What is RTL-SDR?

RTL-SDR is essentially a very affordable way to get started with radio scanning and software-defined radio (SDR) without needing a lot of specialized equipment
RTL-SDR: A small USB device that you plug into your computer
-Originally designed to receive digital television broadcasts on computers
-Some clever people figured out that with the right software, these devices can be used to pick up a wide range of radio frequencies

What Can It Do?

-Can receive live radio signals from different sources like commercial FM, amateur radio bands, air traffic control, and even satellites
-Works with a computer and special software to let you tune into different frequencies
-Can think of it like a radio that you can tune to any station, but instead of just music, you can hear all sorts of communications

It’s Receive-Only

The RTL-SDR can only receive signals; it cannot send out any signals (it’s not a transmitter)

Why Is It Special?

-Extremely cheap compared to other radio equipment that can do similar things
-There’s a big community of people who use RTL-SDR, so there’s lots of free software and advice available
-Before devices like RTL-SDR, you’d have to spend a lot of money to get into radio scanning or SDR

Uses

Hobbyists use it to explore the airwaves around them, listening to anything from marine and aircraft communications to weather satellites
It’s a learning tool for those interested in radio technology or pursuing a hobby in amateur radio

Getting Started

To begin, you’ll need the RTL-SDR dongle, an antenna, and a computer
You install software on your computer that works with the dongle to tune into and decode radio signals
Some popular software includes SDR#, Gqrx, and CubicSDR

Alternatives

-While RTL-SDR is a great low-cost option, there are other more advanced SDRs like Airspy and SDRPlay that offer better performance but at a higher cost
-If you want to both receive and transmit, you might look into something like the HackRF, which is more expensive

What is Software Defined Radio?

-Past: If you wanted to work with radio signals, you needed a bunch of physical knobs and parts that would handle different tasks
For example, you needed one part to change the radio station (tuner), another part to make sense of the incoming radio waves (demodulator), and yet another to send out your own signals (modulator)
-Present: We have powerful computers and special pieces of technology that can turn radio waves into a digital form that computers can understand
Because of this, we can use software on our computers to do all those tasks that used to require separate hardware parts
-SDR means that instead of needing a lot of expensive equipment to work with radio signals, we can do it cheaply with software
This software can process a lot of different radio signals, which makes it possible to create affordable devices that can pick up a wide range of radio frequencies — like the RTL-SDR

What are some RTL-SDR Radio Scanner Applications?

RTL-SDR is a small gadget that lets you use your computer to pick up a wide range of radio signals
-Police and emergency services radios
-Conversations between pilots and air traffic controllers
-Signals from aircraft that show where they are, kind of like a radar
-Short text messages sent between airplanes
-Different channels of walkie-talkies
-Digital voice messages that aren’t secret or encoded
-Locations of ships on the sea
-Messages sent to pagers
-Signals from wireless phones(Cordless phones that you might use around your house) and baby monitors(Monitor in the baby’s room sends out a signal to the receiver that the parent carries around) in your home
-Data from weather balloons that check on the weather
-Information from your own high-flying balloons
-Temperature readings and electricity use sent wirelessly
-Amateur (ham) radio broadcasts (People who enjoy communicating with others using radio signals)
-Special amateur radio signals that share location and information
-Regular TV channels
-Signals from cell phones
-Using your Android phone as a handy radio to pick up different signals
-GPS signals to find out location information
-Checking what frequencies are being used nearby
-Pictures sent from weather satellites
-Listening to satellites in space or the International Space Station
-Studying space and the natural radio signals from our galaxy
-Watching for meteors using the radio signals they reflect
-Listening to regular FM radio stations and their digital information
-Digital and HD radio broadcasts
-Connecting to a regular radio to see a wider range of signals
-Data from taxis
-Generating random numbers for computer security
-Checking how well radio signals are working
-Figuring out what unknown signals are
-Finding where a signal is coming from
-Looking for devices that are causing interference
-Testing how well antennas and radio filters work
-Listening to signals from satellites far away in space
-Catching pictures from satellites that stay in one place in the sky

And if you have a special accessory or a newer version of the RTL-SDR(with an upconverter or V3/V4 RTL-SDR dongle to receive HF signals the applications are expanded to):
-Listen to amateur radio operators talking on different modes
-Decode digital ham radio signals
-Pick up images sent over the radio from ships
-Listen to international radio stations
-Find radar signals and other interesting or unusual broadcasts
-Important to know that some of these activities might not be allowed where you live, so you should check the rules and be careful to use the RTL-SDR responsibly

What is the RTL-SDR frequency range?

RTL-SDR: Small device that lets your computer pick up a wide variety of radio signals, but not all RTL-SDR dongles are the same
Different models can pick up different ranges of frequencies, which is like being able to tune into different stations on your radio
-Tuner: The part inside the dongle that decides what frequencies (or radio stations) you can listen to
Think of it as the knob on an old radio that you turn to find different stations, but in this case, it’s all done inside the dongle
-Frequency Range: The limits of what radio signals the dongle can pick up
Example: Some can pick up very low frequencies (like a bass in music), and some can pick up very high frequencies (like a whistle)
-Different Models: The table lists different models of tuners that are used in RTL-SDR dongles, and each one has a different range of frequencies it can pick up
| Tuner | Frequency range | |————————|—————————————————–| | Elonics E4000 | 52 – 2200 MHz with a gap from 1100 MHz to 1250 MHz (varies) | | Rafael Micro R820T/2/R860 | 24 – 1766 MHz (Can be improved to ~13 - 1864 MHz with experimental drivers) | | Rafael Micro R828D | RTL-SDR Blog V4 Model: 24 - 1766 MHz. Other models may have a cutoff around 1 GHz. | | Fitipower FC0013 | 22 – 1100 MHz | | Fitipower FC0012 | 22 – 948.6 MHz | | FCI FC2580 | 146 – 308 MHz and 438 – 924 MHz (gap in between) |

Table Source: Osmocom Elonics E4000: This one has a wide range but misses some frequencies in the middle
Rafael Micro R820T/2/R860: Another common tuner that can pick up a lot of frequencies, and with some special software, it can do even more
Rafael Micro R828D (RTL-SDR Blog V4): Specific version that has a good range of frequencies it can handle
Fitipower FC0013 & FC0012: Can pick up a variety of frequencies but not as many as the first two
FCI FC2580: Has two separate ranges with a gap in the middle where it can’t pick up signals
-The Elonics E4000 and Rafael Micro R820T/2/R860 and R828D dongles have the greatest frequency range

What is the RTL-SDRs sample rate?

The maximum sample rate is 3.2 MS/s (mega samples per second)
However, the RTL-SDR is unstable at this rate and may drop samples
The maximum sample rate that does not drop samples is 2.56 MS/s, however some people have had luck with 2.8MS/s and 3.2 MS/s working well on some USB 3.0 ports
Footnote:
-sample rate: How quickly a camera takes pictures
The RTL-SDR can ‘take pictures’ of radio waves up to 3.2 million times per second
But when it tries to go that fast, sometimes it misses some ‘pictures’ (this is what they mean by ‘dropping samples’)
Dropped samples are okay if you are just visualizing the spectrum, but will cause problems if you want to demodulate/decode signals
-Most of the time, it works well if it ‘takes pictures’ a bit slower, at 2.56 million times per second
Some people have found that if they use a really good USB port on their computer, like the faster USB 3.0 kind, the RTL-SDR can handle taking ‘pictures’ at the fastest speed without missing any

What is the RTL-SDR’s ADC resolution?

The native resolution is 8 bits, but the Effective Number of Bits (ENOB) is estimated at ~7. Decimation in software may raise this value
Native resolution 8 bits:
The system, device, or sensor originally works with a precision of 8 bits. In digital terms, this refers to the number of bits used to represent data. With 8 bits, you can have 256 different values(from 0 to 255)
Effective Number of Bits (ENOB) is estimated at ~7:
ENOB:
Measure of the quality of an analog-to-digital converter(ADC)
Even though the system is designed to work at an 8-bit resolution, in reality, its performance is closer to that of a 7-bit system
This suggests that the actual precision or quality of the digital signal is slightly less than what 8 bits would ideally offer, effectively giving us around 128 different values (from 0 to 127) with a bit more accuracy
Decimation:
Process used in digital signal processing where you reduce the rate of your data or signal
This can help improve the ENOB because it can reduce noise and increase resolution under certain conditions
So, by applying decimation through software, it’s possible to make the system’s performance better, getting it closer to, or possibly exceeding, the original 8-bit resolution in terms of effective quality

What is the RTL-SDR input impedance?

-Dongles (small devices that plug into a computer and let it receive TV signals) are made to work best with a specific kind of electrical resistance, called “impedance,” which is measured in Ohms
-Most of these TV dongles are designed to match with a 75 Ohms impedance, which is a standard for TV signals
However, the exact 75 Ohms match might not be perfect across all the different TV frequencies they can pick up
-When you use cables designed for 50 Ohms (another common standard, but more for radio or other types of signals) with these 75 Ohm dongles, it’s not a big problem. The loss of signal quality, because of this mismatch, is very small—less than 0.177 dB, which is barely noticeable -Newer dongles, especially those with SMA connectors (a type of connector used for attaching antennas), are designed to work with 50 Ohms. This means they are matched to the same standard as the 50 Ohm cables, making them a better fit for those types of connections without any mismatch

What are the minimum PC requirements?

-For most radio software that has a graphical interface (meaning software you interact with through windows, icons, and menus on your screen), you will need a computer with at least two processing units, called a dual-core processor. This is because the software needs a certain level of computing power to work smoothly
-However, if you’re using simpler, text-based software (where you type commands instead of clicking on icons) or specific software that decodes ADS-B signals (used in airplane tracking), you might not need such a powerful computer. These types of programs can run on less advanced hardware
-Devices like the Raspberry Pi 3, which is a small and affordable computer, or Android smartphones and tablets, are capable of running many of these radio applications. This means you don’t always need a big or expensive computer to get started with software-defined radio activities
-If you’re looking to get into software-defined radio (SDR), we suggest buying either the “RTL-SDR Blog V3” or “RTL-SDR Blog V4” dongle
These cost around $30 USD and are based on the R860 and R8282D chips, respectively. They’re good quality and affordable
-The Elonics E4000 dongle was once very popular, but since Elonics has stopped making the chip, it’s become hard to find and much more expensive. Some people think the E4000 is better because it costs more, but that’s not true. The higher price is just because it’s rare now
-The R820T2 chip, used in our recommended dongles, actually performs better for most radio frequencies people are interested in, especially for tracking airplanes with ADS-B signals at 1090 MHz. It’s more sensitive than the E4000
-Be cautious when buying dongles. Some sellers might claim they are selling a dongle with a specific chip, but you might end up with something different. This is especially true for E4000 dongles sold on auction sites, where some sellers might mislabel other dongles as E4000 due to its rarity
-Trustworthy dongles, like our “RTL-SDR Blog V3” and “RTL-SDR Blog V4”, on the RTL-SDR store page
Models are recommended for anyone interested in using their dongle for SDR activities, as they come with several improvements suited for SDR users

Difference between the R820T/2 and R860?

Nno difference
The R860 is just a name change for Rafael Micro’s accounting purposes as presumably they wish to better track to which customers their chips are going

I already have a USB TV Tuner, is it Compatible?

-If your USB TV tuner has a chip called RTL2832U inside it, then it’s likely to work with the software or purpose you have in mind
If it doesn’t have this chip, then unfortunately, it won’t work
-List on a Reddit page that shows which TV tuners work and which don’t, but keep in mind that this list might not be completely up to date

What is RTL-SDR Blog?

-RTL-SDR Blog, began as a hobby project
The people behind it wanted a place to share their guides on how to use RTL-SDR, which is a type of device that lets you listen to various radio signals. They also wanted to gather all information related to RTL-SDR in one place. Over time, they created lots of tutorials, wrote a book to help others learn about RTL-SDR, and set up a website to help identify different types of radio signals
-A few years back, they decided to make their own version of the RTL-SDR device
Wanted it to be better than the ones already available, with features that radio enthusiasts would appreciate
They kept improving their device, and now they have two versions, called V3 and V4, that offer even better performance for people interested in software-defined radio

Comparisons with other common Wideband Commercial Software Defined Radios

| SDR | Tune Low (MHz) | Tune Max (MHz) | RX Bandwidth (MHz) | ADC Resolution (Bits) | Transmit? | Price ($USD) | |—————–|—————-|—————-|——————–|———————–|———–|————–| | RTL-SDR | 24 | 1766 | 3.2 / 2.56 Stable | 8 | No | ~30 | | (R820T/R860/R828D) | | | | | | | | Funcube Pro+ | 0.15 | 260 | 0.192 | 16 | No | ~200 | | | 410 | 2050 | | | | | | Airspy | 24 | 1800 | 10 | 12 | No | 199 | | SDRPlay | 0.1 | 2000 | 8 | 12 | No | 149 | | HackRF | 30 | 6000 | 20 | 8 | Yes | 299 | | BladeRF | 300 | 3800 | 40 | 12 | Yes | 400 & 650 | | USRP 1 | DC | 6000 | 64 | 12 | Yes | 700 |

-The Airspy or SDRPlay are good choices to consider as a step up from the basic RTL-SDR if you’re looking to pick up a variety of signals
But if you’re mostly interested in catching signals that don’t vary much in frequency, the Funcube Dongle Pro+ could be a good option
-Comprehensive list of different software-defined radios:
Roundup on the RTL-SDR website

RTL-SDR dongle from the website RTL-SDR.COM
Software-defined radio (SDR) receiver that you can use with a computer to receive radio signals from various frequencies
Versatile tool for hobbyists and professionals alike to explore radio frequencies, including but not limited to FM and AM broadcasts, emergency services, satellite communications, and many other signals
-Version 3(V3) of their product line, and it’s capable of receiving DVB-T, DAB, and FM signals
Mentions some of the chipsets it uses, like the RTL2832U and R820T2, which are responsible for the digital processing and tuning of radio signals, respectively
-TCXO-0.5PPM: The type of oscillator used in the device, which has a very low error margin (0.5 parts per million), making it very stable and precise
-Bias-T HF: Supports direct high-frequency sampling and can provide power over the antenna connector (Bias-T) for devices like low noise amplifiers

Reference:
https://www.rtl-sdr.com/about-rtl-sdr/