RTL-SDR Releases New V4 USB Dongle

The RTL-SDR dongle is one of the most widely used tools for experimenting with software-defined radio (SDR) applications. It has become extremely poplar due to its low cost (~$30) and ease of use. With the dongle, a user can access the radio spectrum from around 28MHz up to 1.75GHz. As a result, users can scan spectrum for wireless signals, listen to air traffic control, EMS communications, and HAM radio operators, use the device as a police scanner, and even capture data from satellites.

At the heart of the device is an RTL2832U chipset, which was originally designed for DVB-T TV tuning. However, through the combined efforts of a few individuals it was found that the raw I/Q data output from these chips can be accessed directly. This allows the captured wireless signals to be post processed however an individual may want. This can include demodulating signals, performing FFTs, and experimenting with various signal processing functions.

Since its inception, there have been a few different versions of the RTL-SDR dongle. Each has made small improvements to the functionality and performance of the device. The RTL-SDR V4 model also adds minor enhancements to circuitry while changing the tuner chip from the RTL2832U to the R828D. The RTL-SDR V4 is equipped with an integrated up converter that provides better HF reception. Previous versions would use direct sampling for HF reception which would result in Nyquist folding of signals around 14.4MHz. With the up converter, the Nyquist folding is eliminated and the sensitivity is improved in the HF band. Furthermore, the R828D has three RF inputs for HF, VHF, and UHF. In the design a triplexer is used to interface between the antenna and the three inputs, which results in improved isolation and filtering for strong out of band signals. There also exists the possibility to include notch filters in common interference bands, such as broadcast AM, broadcast FM, and DAB bands.

An additional upgrade to the circuitry of the board is a redesigned power supply. The new supply creates an improvement in phase noise on the device and generates less heat in the device.

Improvements in the third iteration of the device are still present in the V4 model as well. This includes the metal black enclosure, a thermal pad for heat management, a 1PPM TCXO, improved ESD protection, and USB noise choking. If using the new device, specific drivers will need to be installed which can be found on GitHub. Utilizing the R828D chip in the design also enables the dongle to be priced cheaper than the previous version.

The original chipsets used in the designs have become supply constrained which in turn has caused the price to increase. However, existing stock of the R828D chip has allowed for a lower cost product. The dongle alone can be purchased for $29.95 while the dongle with an antenna set can be purchased for $39.95. It is also important to note that this is a limited edition design. The tuner chip used is completely out of production, so once the current stock of the part depletes, the RTL-SDR V4 will no longer be available.