Comparison between the RTL‑SDR Blog V3 and RTL‑SDR Blog V4,
Here’s a detailed comparison between the RTL‑SDR Blog V3 and RTL‑SDR Blog V4, along with practical implications (especially for your antenna-wire setup). If you like, I can summarise a “which one to pick” at the end.
Key Differences & Improvements in V4
Here’s what changes in V4 relative to V3, based on the official datasheets and reviews:
| Feature | V3 | V4 | Notes / Impacts |
| Tuner / front-end | R820T / R820T2 / older front-end design (uses direct sampling for HF) (rtl-sdr.com) | Uses R828D tuner, with a triplexed input (HF, VHF, UHF) plus notch filters for common interference bands (rtl-sdr.com) | The triplexing helps isolate bands, reducing inter-modulation and overloading from strong out-of-band signals. |
| HF (below ~30 MHz) reception method | Direct sampling mode (you connect the antenna to the ADC directly, bypassing tuner). But direct sampling has limitations: aliasing, no gain control, easily overloaded by strong signals. (rtl-sdr.com) | Built-in upconverter (28.8 MHz LO) to bring HF into the tuner input, rather than pure direct sampling. (rtl-sdr.com) | This is a big improvement: fewer spurs/aliases, better dynamic range on HF, and ability to control gain. |
| Filtering / front-end isolation | Less separation between bands, more risk of overloading from broadcast stations | Better filtering with triplexers + built-in notch filters (e.g. for AM, FM, DAB) (rtl-sdr.com) | Particularly useful in urban / noisy RF environments, or with long-wire antennas that pick up strong signals |
| Current draw / heat / power design | Higher current draw, more heat (older power supply/layout) | Slightly lower current, reduced heat, improved power supply (less noise) (udxf.nl) | Lower heat is helpful when the dongle is enclosed or mounted near other electronics |
| Bias tee | 4.5 V (software-controlled) | 4.5 V (software-controlled) up to 180 mA (rtl-sdr.com) | Similar, so for powering active antennas or LNAs, both are acceptable (if your antenna setup needs it) |
| Frequency & bandwidth | Covers ~500 kHz up to ~1.7 GHz. Stable bandwidth ~2.4 MHz (peak up to ~3.2 MHz) (rtl-sdr.com) | Range expanded: 500 kHz to 1.766 GHz. Stable bandwidth ~2.56 MHz (up to 3.2 MHz with drops) (rtl-sdr.com) | Slight improvements in bandwidth stability. |
| Driver / software support | Well supported historically | Requires updated drivers / DLLs to support V4; many SDR apps have already been updated (SDR#, SDR-Console V3, SDR++ etc.) (rtl-sdr.com) | You’ll need to ensure your software stack is up to date; otherwise the V4 may not function properly (mis-frequency, no signal, etc.) |
| Cost / supply / chip pricing | Uses R820 series which is more expensive now | V4 uses R828D, which the designers say is cheaper / more available currently (swling.com) | Could make V4 more economical / practical to produce / stock |
| Potential drawbacks of V4 | — | Some users have reported that in specific bands or use cases, V4 might perform worse (depending on conditions) (Reddit) | But overall for most use cases, V4 is expected to be an upgrade |
Practical Impact for a Wire-Antenna Setup (Two Cables Held Aloft, Drop to Computer)
Given your plan — two wires joined in the middle (forming a dipole or long-wire style), elevated by poles, drop to your receiver — here’s how the differences matter:
- Dynamic range / overload
- Long-wire antennas tend to pick up strong signals (AM broadcast, FM, local strong TX) along with weaker HF signals. The better front-end filtering and isolation of V4 help reduce overload / intermodulation and spurious signals.
- In contrast, V3’s direct sampling mode on HF is more susceptible to overload, aliasing, and you may see “ghost” signals mirrored around the Nyquist frequency. (RadioReference.com Forums)
- HF sensitivity and gain control
- With V4’s upconverter, you get gain control into HF bands, which helps in adjusting for weak signals.
- In V3 direct sampling mode, gain control is limited (or absent) and performance suffers under strong local signals. (rtl-sdr.com)
- Spurious / aliasing control
- The V4 approach avoids Nyquist folding / aliasing in the HF region that plagues direct sampling. That means “fake” copies of signals are less of an issue.
- In V3, strong signals outside the band can alias into the band you’re observing. You’ll often need extra filtering (low-pass, high-pass) to reduce this. (RadioReference.com Forums)
- Noise floor, heating, component quality
- V4’s improved power design and lower heat generation can reduce internal noise (especially when the dongle is enclosed somewhat).
- Lower thermal drift helps when you have long runs of cable and possibly operate outdoors.
- Software / calibration
- You’ll need to make sure your SDR software / drivers recognize the V4 correctly and are updated. Otherwise, you might see weird behaviour or nothing at all. (rtl-sdr.com)
- V3 is older and well supported, so the software side is “safer” in the sense that a lot of scripts, projects reference V3.
Which One to Choose (for Your Use Case)
Given your wire-antenna style setup and likely interest in HF/VHF/UHF:
- V4 is generally the better choice: it addresses many weaknesses of V3 in HF performance, filtering, dynamic range, and noise, which are exactly the challenges you’ll face with a long-wire or elevated-antenna system.
- However, V4 demands that your software / drivers are compatible and up to date.
- If you already have a V3 and it “works well enough” in your environment (low interference, strong signals), it may serve you adequately without upgrading.