RTL-SDR V4, Better Than V3? (Review)

    • by Burkhard Kainka
    • Reading time: 3 min

    RTL-SDR V4 sticks are the latest in a series known for their capability to receive a broad range of HF signals, extending beyond 1,000 MHz. This review delves into the RTL-SDR V4, highlighting its advancements over earlier versions.

    Preferred Software

    The preferred software for the RTL-SDR V4 is SDR-Sharp. After installation, it typically displays a frequency in the FM band, where numerous strong stations are available for initial testing. Reception is generally smooth, delivering clear sound quality. Users might also explore signals in the 2-meter band, the 70-cm band using narrowband FM, listen to AM aviation communications, or track radio thermometer signals.

    RTL-SDR V4 Dipole Antenna Kit
    Dipole Antenna Kit for the RTL-SDR V4.

    RTL-SDR V4 Dipole Antenna Kit

    RTL-SDR V4 comes with a versatile dipole antenna kit, ideal for those without existing antenna setups. The kit includes 14 cm short and 1 m long telescopic antennas, which can be combined to form a dipole. A suction cup holder facilitates window mounting. The connection cable features a ferrite core with a dual turn of the antenna cable, functioning as a common-mode choke to balance the dipole connection and reduce interference from the PC to the antenna.

    Antenna on window
    The antenna can be mounted on a window.

    The included tripod is particularly useful for the longer antenna rods, allowing optimal dipole adjustment for frequencies up to a 4 m wavelength.

    Shortwave Reception

    My interest largely lies in longer wavelengths, particularly the shortwave range. Previous SDR sticks had a definitive lower frequency limit, which I initially overcame using a ring mixer and quartz oscillator to upconvert shortwave signals. However, this setup was imperfect, often overwhelmed by RF noise from the device and PC, obscuring real antenna signals among numerous phantom signals.

    Use of Direct Sampling

    The RTL-SDR V3 introduced a feature for the lower frequency ranges, bypassing the first mixer and allowing the antenna signal to be processed directly by the AD converter. In SDR-Sharp, this requires setting Direct Sampling (Q-Branch) for lower frequencies, while Quadrature Sampling remains suitable for higher frequencies. Despite these adjustments, V3 still struggled with phantom signals and intermodulation products when connected to long antennas, particularly evident when receiving AM stations in the 40m amateur radio band during peak times.

    40m band with RTL-SDR V3
    The 40m Band with the RTL-SDR V3 showing phantom signals.

    Improvements with RTL-SDR V4

    The latest iteration, RTL-SDR V4, includes an HF upconverter utilizing the SA612 mixer. This addition aims to address overload issues and improve signal clarity. The new version also features design tweaks to minimize interference, promising a cleaner reception up to 1 GHz.

    RTL-SDR V4 inside
    Inside the RTL-SDR V4.

    Initial tests with FM signals yielded excellent results, with the device offering various settings to fine-tune the reception and manage interference effectively. This improvement extends to higher frequencies, notably enhancing clarity and reducing unwanted noise and signals.

    Comprehensive Shortwave Tests with V4

    Testing on shortwave bands demonstrated significant advancements. The RTL-SDR V4 automatically enables the upconverter when necessary, allowing seamless tuning from 0 to 1,000 MHz. An initial scan of the 19m broadcast band clearly received a station from Turkey without interference, a notable improvement over previous versions.

    AM 19m band
    Clear reception of AM stations in the 19-meter band.

    Overall, the RTL-SDR V4 marks a substantial improvement in the quality and clarity of SDR reception across a broad spectrum of frequencies, validating its effectiveness and versatility in handling various signals and conditions.



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