Comparing RTL-SDR v3 and v4 software defined radios
Here’s what’s inside — i.e. the chips used:
- The tuner chip is R820T2 (sometimes listed as “R860” — manufacturer-side relabelling, but electrically the same).
- The ADC/demodulator + USB interface chip is RTL2832U — this is the core “RTL-SDR” chip that digitizes RF and streams I/Q data over USB.
In short: R820T2 tuner + RTL2832U demodulator/ADC.
Since you’re already familiar with SDR and radio-astronomy, here’s a summary of the key components and differences of vs the earlier — what’s inside them, how they work, and how that affects what you can do.
🔧 Core hardware (common to both V3 & V4)
- Demodulator / ADC chip: RTL2832U — this is the 8-bit ADC + USB interface that converts the received RF (after tuning) to a digital baseband stream for your PC.
- Frequency coverage: both can nominally cover from ~500 kHz up to ~1.7-1.8 GHz (depending on tuner + front end).
- SMA F antenna connector + metal enclosure: allows use of external antennas and provides shielding / better thermal dissipation.
- 1 PPM TCXO (temperature-compensated crystal oscillator): gives reasonably stable frequency (low drift), important for tasks like narrowband reception or radio-astronomy spectral work.
- Software-selectable Bias-T (4.5 V via coax): both V3 and V4 support powering e.g. LNAs or active antennas via the coax.
These components form the “standard SDR stick” core — tuner, ADC/demodulator, oscillator, antenna port, and interface. The rest are improvements aimed at making the stick more stable, more useful across HF→UHF, more robust, and better matched to SDR use (rather than DVB-T).
🆚 Differences & Improvements: V3 vs V4
Here’s where V3 and V4 diverge substantially — and why someone might pick one over the other depending on application (e.g. your radio-astronomy background):
| Feature / Component | V3 | V4 |
| Tuner chip | R820T2 | R828D |
| HF (long-wave / short-wave) support | “Direct sampling” mode via ADC bypass (works ~500 kHz–24/28 MHz), but with aliasing/ Nyquist issues. | Built-in HF “upconverter” (mixer + LO at 28.8 MHz) → HF signals are converted to higher IF for standard tuner + ADC, avoiding aliasing and giving cleaner HF with gain control. |
| Front-end filtering / Band isolation | Standard wideband front-end (less band isolation) | Triplexer splitting antenna input into HF / VHF / UHF + added notch/ band-reject filters for common interference (AM/FM, DAB, etc.) → better isolation and less desensing from strong broadcast signals. |
| Thermal / power / noise performance | Uses improved design vs generic sticks: low-noise LDO regulator, better PCB layout, USB noise choke, ESD protection, metal enclosure with thermal pad. | Further optimized PSU and PCB layout → lower current draw, less heat, improved phase noise, better overall stability under strong signals. |
| HF usability & signal quality | Works for HF but with caveats: aliasing / signal folding across Nyquist, lower performance, possible noise / spur issues. | HF reception cleaner, gain adjustable, less aliasing — makes HF, long-wave, short-wave much more practical. |
| Overall trade-offs | Slightly simpler internally, but HF is “direct-sampled” (dirty), front-end more vulnerable to overload. | More sophisticated front-end + upconverter: cleaner across bands, but added filtering can slightly reduce sensitivity on some VHF/UHF bands (a few dB) vs V3. |
🎯 What this means for applications — especially for radio-astronomy / amateur-radio work
- For HF listening (long-wave, short-wave, ham HF, radio-astronomy below VHF), V4 is substantially more robust and gives cleaner results because of the upconverter + better front-end filtering.
- For general VHF/UHF scanning, air-band, ADS-B, AIS, etc., both V3 and V4 are broadly comparable — but V4’s filtering may slightly reduce sensitivity in some conditions (trade-off for better dynamic range and less overload)
- For situations with strong broadcast signals (FM, AM, DAB, big transmitters), V4’s improved front end makes a noticeable difference — less intermodulation, less desensitization.
- If you want to power an LNA or active antenna via coax, both support Bias-T, which is convenient.
- For frequency-stability-sensitive tasks (satellite work, radio-astronomy spectral lines, narrowband work) the 1 PPM TCXO + better shielding in both helps — but V4 gives a more stable platform overall, especially over varying temperature or when running long sessions.
✅ My view (given your background)
Given that you already use SDR (and even SDRplay + interferometry) and have interest in radio-astronomy: the V4 represents a meaningful step forward over V3 — especially if you want reliable HF / wideband work (long-wave, short-wave, possibly even for line-work or meteor detection). The improved front end and upconverter reduce many of the annoyances you’d get with V3 (aliasing, strong-signal overload, thermal drift), making the V4 more “serious-use ready.”
That said, V3 remains perfectly serviceable — especially if cost, simplicity, or familiarity matter.