Many thanks to SWLing Post contributor, Gary Wise (W4EEY), for the following review of the RTL-SDR dongle:
Based on your blog post on the Version 3 release of the RTL-SDR dongle I had to buy one. I ordered mine from Amazon for $25, and it came in two days. I have an earlier version of this unit that was VHF and above only. What intrigued me about the V3 was the possibility of HF reception in the Direct Sampling mode (without an up converter). So I had to try it.
I used the RTL-SDR Quick start guide at RTL-SDR.com/qsg. While I did not see any mention of Version 3, I hoped that the software that was linked would be adequate. As I am using a Windows 7 laptop, I downloaded the Zadig driver installer, along with copies of SDR# and HDSDR.
Getting the dongle going was pretty straightforward. And right away I was receiving VHF and above signals. The I/O driver defaults to Quadrature demodulation and this was what is used to receive VHF. But what about HF?
It took me awhile to figure out that you select Direct Sampling in the setup screen for the driver. In SDR# software this is found by clicking on the gear wheel icon.
Under sampling mode select Direct Sampling (Q branch).
In HDSDR you select the EXTIO icon.
Here you select the Q Input under Direct Sampling.
Note that with both you must use the Q input.
With the telescoping antennas included with the dongle, I received very few signals (of very poor quality). But I had read that the unit can only receive HF with a substantial antenna, so I moved the laptop to my hamshack.
I use an ELAD antenna distribution amplifier for my HF receive antennas.
It was easy to use a spare output from the ELAD ASA15 to drive the antenna input of the RTL-SDR V3.
Wow, what a difference!
First up was international shortwave. Here’s a shot from my Alinco General Coverage receiver on 9955 kHz this morning using my 260′ beverage antenna (pointed toward Europe). S9 on the Alinco S Meter.
And here’s the same signal on SDR#.
There was a delay in the audio coming from the PC versus from the receiver, but other than that, reception was identical. Audio quality was very good.
I then moved to the 20M Amateur Radio band. USB audio demodulation.
The little dongle worked! It is not what I would call my first choice in receivers, but it will demodulate AM and SSB just fine.
I did not try it on CW as I ran out of time.
I also tried the HDSDR software, which worked equally as well (but I think I prefer SDR# for ease of use).
All in all, if you have or can put up a good antenna for HF, the little $25 dongle is in, my opinion, worth trying out.
73,
Gary
W4EEY
Thank you, Gary, for not only giving a quick evaluation of the RTL-SDR’s HF performance, but for describing how to setup HF reception via SDR# and HDSDR.
Over the years, I’ve gotten probably hundreds of emails from readers who would like to try their hand at SDRs, but were cautious about investing. For many years, a 3rd generation SDR would set you back at least $300-400. At $25 shipped, the RTL-SDR V.3 is an SDR receiver that is accessible to anyone who can afford a fast food meal or a few cups of Starbucks coffee. My how times have changed!
Once I get a few transceiver reviews off of my table, I might do some side-by-side HF comparisons between the RTL-SDR and a few of my other SDRs.
Thanks again, Gary!
After researching the RTL-SDR software defined radio, we’ve determined the easiest way to setup the device on a Windows computer. There are multiple versions of the USB SDR, but this is the straightforward way to get the device working for digital trunking systems. It’s possible to turn a $20 device into a VHF/UHF scanner by following these simplified steps. Note: These instructions do not include steps to decode encrypted radio communications.
RTL-SDR
RTL-SDR is an example of how hacking and tinkering can lead to something positive. The device is a small USB dongle that has been modified from a DVB-T TV tuner to a software defined radio. It was discovered that the modification typically allowed moderate reception of frequencies between 50 MHz to 1.7 GHz. Reception isn’t anywhere near as good as a dedicated receiver/scanner with proper filters and circuitry. However, it’s now possible to turn the device into a VHF/UHF trunking radio scanner by following some simple steps. The RTL-SDR is available from multiple sources for around $20.
Before we continue, there are also many questions about shortwave receive. Even with a required upconverter, the RTL-SDR receive on HF (below 50 MHz) is very weak to deaf. Unless it is demonstrated that a newer version or modification produces significantly better results, buyers can assume that it’s not a very good shortwave receiver.
Using RTL-SDR for Trunking Radio Systems
It’s possible to use the RTL-SDR to track trunked radio systems, particularly in the UHF band, especially 800 MHz. It will properly trunk EDACS and Motorola systems that are not encrypted. Other systems can also be tracked. It’s best to use two USB RTL-SDR dongles, but you can start listening to trunked radio with only one. This is a simplified guide of how to use one dongle to trunk digital radio systems in the UHF band.
Required Software
In order for the RTL-SDR to work, you must follow these steps in order. The device requires special drivers and software that must be configured in order for this to work. You can expect about 15 minutes to half an hour to get up and running. You must have an antenna (the RTL-SDR usually comes with one) in order for this to work. In addition, this guide is for a Windows system only. Linux based systems may differ in setup. Setup typically requires administrator privileges.
These steps are specifically for getting digital unencrypted trunking to work using the RTL-SDR device on a Windows 7/8 64 bit machine only. Be patient because this process isn’t user friendly (because it’s not automatic) and requires specific software and exact configuration.
Step 1
Plug your RTL-SDR USB dongle into your computer. Ignore any information about drivers failing to install.
Step 2
Download the RTL-SDR driver install software here.
With your RTL-SDR device connected to your computer’s USB port you will launch the software “zadig.exe” and select “list all devices” under options. You must select “bulk interface 0” as your device. The driver should be listed as WinUSB (6.xxxx).
Click on “install” or “reinstall” driver. It make take several seconds, be patient.
You cannot continue the process without successfully installing the drivers.
The software will tell you if/when the drivers successfully install. If you successfully install the driver, then close the driver installation software and go on to the next step.
Step 3
Download the latest version of Unitrunker. Install it to your computer.
Run Unitrunker and select the plus sign to add a new receiver. Note: for the remainder of steps your RTL-SDR device must be plugged in and the drivers must be properly installed!
Select “RTL-SDR” as your device. You should now be able to double-click it and see many settings/options for “VCO” and “info.”
Next, copy the configuration settings in the image below. You should have 2 VCO’s set under the “info” tab. The settings should match what you see in the images EXACTLY.
Once you’ve configured it, click the play button, which will start Unitrunker in running mode. The status should switch to “running.”
If you’ve properly setup Unitrunker, you will likely see another window pop up after a few seconds of listening to the control channel. You will see talk groups, which means your software is properly working. In order to decode the digital audio, you must go onto the next step of setting up DSD+.
Step 4
Download DSD+. This is the digital voice decoder software. Install DSD+ by unzipping it to a folder. Remember the folder’s location! Be sure to use the latest version.
You must also download lame_enc.dll, which is a required driver. Download lame_enc.dll and put it into your DSD+ directory.
You have now completed setup for DSD+. Close all DSD+ windows before continuing.
Step 5
You must have an audio piping program to route the digital signal to DSD+. ULTRATechLife recommends VB cable. Download/install it and do not change any of its settings.
You will also need to go to your audio control panel and click on recording devices. Set the VB cable device to be the default recording device.
Step 6
After you correctly setup DSD+ and VB cable, launch Unitrunker. Wait a few seconds for talk groups to appear. You should now see a scrolling list of talk group ID’s.
Next, launch DSD+ to start decoding voice. Launching DSD+ involves going to the directory you installed it in and clicking on DSD+.exe (or DSDplus.exe) to start the program. You should see several windows pop up and you should leave them running for DSD+ to work.
You can start/stop Unitrunker by pressing the Play/Stop buttons.
Critical note: The RTL-SDR device requires some tinkering with the “Correction” setting/field in the “info” settings tab of Unitrunker. We recommend letting the RTL-SDR heat up for 15 minutes and setting the “Correction” value… between: 90.0 – 99.0 (until you hear clearer trunking voice reception). Change this value, until you get it working!
If you hear voice from the trunking system, you’ve successfully setup your RTL-SDR device, congratulations. If this didn’t work for you, you should start from step one. Be sure you follow the steps exactly.
Conclusion
Setting up RTL-SDR requires special software and configuration, which makes it a moderately difficult thing to do. It’s not user friendly and is definitely not something that’s so easy anyone can do it. However, it’s an interesting thing to play with and you can search Google for other ideas on how to use the RTL-SDR device.
It’s also possible to use special software, such as SDR Sharp to manually tune in other frequencies, listen to aircraft, weather band, FM radio, and other amateur radio frequencies in the VHF/UHF bands. Finally, most people will find that only stronger signals can be received with the RTL-SDR. It’s not that great of a receiver, but it does work.
Good luck with your listening and tinkering! We hope you found this article helpful.
About Author:Ben Alonzo is a scientist, tech expert, professor, and director of ULTRATechLife.com. He’s CEO of the media-tech firm Storm Sector, LLC. Ben holds an M.S. in Geoscience, M.S. in Nutrition and Health, and a B.S. in Geoscience. He’s a highly-rated professor that teaches several courses, including earth science, environmental science, oceanography, meteorology, and public health. His diverse background spans numerous fields, network and computer systems, healthcare, weather forecasting, consumer electronics, computer programming, and web development. Ben holds numerous professional licenses and certifications, ranging from information technology to healthcare and emergency medical technician. He’s also a pilot that loves flying. He’s been writing about science and tech for over 10 years. You can see some of his past articles on the Houston Chronicle, eHow, Hearst, and other networks. In his free time, he loves scuba diving, traveling, storm chasing, producing videos and writing guitar music. More about author.
Coming soon: Follow Ben on his new social media: Instagram @realniceben | Twitter @realniceben
What is RTL-SDR?
RTL-SDR is a very cheap software defined radio that uses a DVB-T TV tuner dongle based on the RTL2832U chipset. With the combined efforts of Antti Palosaari, Eric Fry and Osmocom it was found that the signal I/Q data could be accessed directly, which allowed the DVB-T TV tuner to be converted into a wideband software defined radio via a new software driver.
Essentially, this means that a cheap $20 TV tuner USB dongle with the RTL2832U chip can be used as a computer based radio scanner. This sort of scanner capability would have cost hundreds or even thousands just a few years ago. The RTL-SDR is also often referred to as RTL2832U, DVB-T SDR, or the “$20 Software Defined Radio”.
There are many other software defined radios similar to the RTL-SDR, but they all come at a much higher price. The FunCube PRO+ is a good receiver similar to the RTL-SDR, priced at around $190 USD. There is also the soon to be released HackRF (~$300USD) and BladeRF SDRs ($420 and $650), which can both transmit and receive.
What is Software Defined Radio?
Radio components such as modulators, demodulators and amplifiers are traditionally implemented in hardware components. The advent of modern computing allows these traditionally hardware based components to be implemented into software instead. Hence, the software defined radio. This enables easy signal processing and thus cheap wide band scanner radios to be produced.
What are some RTL-SDR Radio Scanner Applications?
The RTL-SDR can be used as a wide band radio scanner. Applications include
Furthermore, with an upconverter or direct sampling mod to receive HF signals the applications are expanded to
Note that not all the applications listed may be legal in your country. Please be responsible.
What is the RTL-SDR frequency range?
This is dependant on the particular tuner variant used in the dongle.
Table Source: Osmocom
As you can see from the table, the Elonics E4000 and Rafael Micro R820T 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 2.4 MS/s, however some people have had luck with 3.2 MS/s working well on USB 3.0.
What is the RTL-SDR’s ADC resolution?
The resolution is 8 bits.
Cpu Requirements For Software Defined Radio DonglesWhat is the RTL-SDR input impedance?
Since these dongles are intended for TV, all dongles will have an input impedance of 75 Ohms. However, the mismatch loss when using 50 Ohm cabling will be very minimal at the frequencies the dongle can cover.
The 75 Ohm impedance for the R820T can be checked on the datasheet which can be downloaded here.
What dongle should I buy?
The cheapest, most common an generally best performing dongle at the moment is the Rafael Micro R820T. It can be bought for about $20 USD.
The Elonics E4000 used to be the most common, but Elonics has closed and ceased chip production, making the E4000 rarer and much more expensive these days.
The R820T also is generally regarded as having better performance and sensitivity for most interesting frequencies. For ADS-B, the R820T is much more sensitive at 1090 MHz. For these reasons, the R820T is currently the recommended dongle, unless you need the greater frequencies the E4000 provides.
Be careful when buying a dongle as certain sellers tend to misrepresent their devices (knowingly or unknowingly) as having compatible tuners, when in fact they may send out a device with an incompatible tuner. Also be wary when buying E4000 dongles from auction sites as there are many dodgy sellers incorrectly advertising R820T dongles as the rare E4000.
See the BUY RTL-SDR page for more information about where to obtain dongles from reputable sources.
I already have a USB TV Tuner, is it Compatible?
An up to date list on compatible and incompatible tuners can be found on this reddit wiki page.
Comparisons with other Wideband Commercial Software Defined RadiosCpu Requirements For Software Defined Radio Dongle Manager
Useful Links
http://sdr.osmocom.org/trac/wiki/rtl-sdr – Official rtl-sdr osmocom website
http://www.reddit.com/r/RTLSDR – Reddit rtl-sdr forum
https://groups.google.com/forum/#!forum/ultra-cheap-sdr – Google groups forum
www.sdrsharp.com – SDRSharp official website
www.rtlsdr.org – RTL-SDR community Wiki
http://www.dxzone.com/ – A good ham related database useful for research
http://www.dangerousprototypes.com – A blog about open source hardware projects that often has SDR related posts.
http://www.hackaday.com – A blog about DIY hardware that also often has SDR related posts.
http://sdrformariners.blogspot.com/ – SDR for mariners. A new blog about marine related RTL-SDR applications.
http://www.EEWeb.com – A large electrical engineering news and community website that sometimes feature SDR related stories.
Cpu Requirements For Software Defined Radio Dongle Download
http://labyrinth13.com/ – Strange Beacons. Radio user who records and makes videos about several interesting signals he finds. Often uses an RTL-SDR. Hitler history in tamil.
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