SDRplay RSPdx Review 2026: 14-Bit ADC, 3 Antenna Ports, 1 kHz–2 GHz
The RSPdx costs five times the RTL-SDR V4 and earns it for HF work. On VHF/UHF — police, airband, P25 — the practical difference is smaller than the price gap suggests. Whether the upgrade makes sense depends almost entirely on what frequencies matter to you.
Quick Verdict
Buy the RSPdx if:
- You want serious HF performance (shortwave, amateur bands below 30 MHz)
- You need multiple antenna inputs without moving cables
- Strong nearby signals are causing blocking or intermodulation on your current dongle
- You're ready to invest in SDR as a long-term hobby
Stick with RTL-SDR V4 if:
- Your use is mainly VHF/UHF — police, fire, airband, NOAA weather
- You're a beginner still learning the software
- Budget is a constraint — the V4 does 90% of the work for 20% of the price
- P25 trunking is your main goal (you need two receivers regardless)
Spec Comparison: RSPdx vs RSP1A vs RTL-SDR V4
Three receivers, three price points. The table below covers the specs that actually matter for real-world use — not the marketing copy.
| Spec | SDRplay RSPdx | SDRplay RSP1A | RTL-SDR V4 |
|---|---|---|---|
| ADC bits | 14-bit | 14-bit | 8-bit |
| Effective dynamic range | ~78 dBc | ~72 dBc | ~42 dBc |
| Frequency range | 1 kHz – 2 GHz | 1 kHz – 2 GHz | ~500 kHz – 1.75 GHz |
| Max IF bandwidth | 10 MHz | 10 MHz | 2.4 MHz |
| Antenna ports | 3 (A/B/C) | 1 | 1 |
| HDR mode | Yes (Port A) | No | No |
| OS support | Win / Mac / Linux | Win / Mac / Linux | All platforms |
| Price | $200-240 | $109-129 | $37.95 |
Why the 14-Bit ADC Actually Matters
The RTL-SDR V4 uses an 8-bit analog-to-digital converter. The RSPdx uses a 14-bit ADC — 12-bit effective in practice. Those extra bits translate directly into dynamic range: roughly 36 dB more than the RTL-SDR's 8-bit converter.
In real terms: the RSPdx can receive weak signals while a much stronger signal is simultaneously present in the same band, without the stronger signal causing the weaker one to disappear. RTL-SDR dongles are prone to a phenomenon called blocking — a nearby strong transmitter desensitizes the tuner and weaker signals on adjacent frequencies vanish from the waterfall entirely.
When dynamic range matters most
On VHF/UHF (150–870 MHz) for police and fire scanning, strong-signal blocking is rarely a problem unless you're very close to a repeater or broadcast tower. On HF — shortwave, ham bands below 30 MHz, medium wave — strong broadcast stations share spectrum with weak signals constantly. That's where the RSPdx's dynamic range advantage is most visible and most practically useful.
If you're primarily scanning VHF/UHF police and fire frequencies, the RTL-SDR V4's 8-bit ADC is usually adequate. The V4's improved filtering over older dongles handles most FM overload scenarios. The RSPdx's ADC advantage matters most when you're doing HF work.
Three Antenna Ports: What They're Actually For
The RSPdx has three SMA antenna inputs labeled A, B, and C. You switch between them in software — no cable swapping required.
HF/VHF Optimized (<200 MHz)
Optimized for frequencies below 200 MHz. This is also the only port that supports HDR mode. For serious HF listening — shortwave, amateur bands, medium wave — you want a dedicated antenna on Port A and you want to use it.
Broadband
General broadband reception. Works across the full 1 kHz–2 GHz range. Run your discone or wideband antenna here for VHF/UHF scanning while keeping a dedicated HF wire on Port A.
Broadband
Second broadband port, identical characteristics to Port B. Useful for a third antenna — a dedicated airband antenna or an ADS-B antenna — without needing a switch box.
The practical value here is real but narrow. If you run a single wideband antenna for everything, the three ports provide no advantage. The benefit is for operators who want different antennas for different frequency ranges — a longwire for HF, a discone for VHF/UHF — without physically disconnecting and reconnecting cables. You switch in SDRuno with one click.
HDR Mode: What It Does and When to Use It
HDR (High Dynamic Range) mode is available exclusively on Port A. When enabled, it bypasses part of the normal ADC signal path and reduces the effect of strong out-of-band signals on weak in-band signals.
The difference is most obvious on 40 meters (7 MHz) and 80 meters (3.5 MHz) in the evening hours when international shortwave broadcast stations are running high power on nearby frequencies. Without HDR, a 500 kW broadcast transmitter a few hundred kHz away can mask weak amateur SSB signals. With HDR enabled, those weak signals often reappear on the waterfall.
HDR is not a cure-all
HDR mode helps with strong signals in adjacent bands. It doesn't improve sensitivity on its own, and it's not a substitute for a good antenna or a quiet RF environment. On a noisy urban HF band, antenna quality and location will matter more than HDR. In a quieter RF environment where the limiting factor is adjacent-channel interference from strong broadcasters, HDR makes a real difference.
Software: SDRuno, SDR++, and the Plugin Ecosystem
SDRuno (Windows)
SDRplay's own software is polished and well-integrated with the RSPdx's features. Antenna port switching, HDR mode, gain control, and IF bandwidth selection all surface clearly in the UI. SDRuno handles FM stereo, AM, SSB, CW, and digital decoding plugins. The interface has a steeper learning curve than SDR# but gives you more direct control over the RSPdx's hardware.
The limitation: SDRuno is Windows-only. If you're on Mac or Linux, you're using a different application.
SDR++ and CubicSDR (Mac / Linux / Windows)
Both SDR++ and CubicSDR support the RSPdx through the SDRplay API and plugin. Install the SDRplay API (available from sdrplay.com) first, then the front-end application. Feature coverage is good — you can switch antenna ports, adjust gain, and access most hardware settings. HDR mode may require dropping to the SDRplay API control panel depending on the software version.
The SDRplay plugin ecosystem is smaller than the RTL-SDR's, which has decades of community development behind it. All major use cases are covered — there are working plugins for P25, DMR, ADS-B, APRS, and weather satellites. Niche decoders that exist as RTL-SDR plugins may not have RSPdx equivalents.
SDRTrunk (P25 / DMR Trunking)
SDRTrunk supports the RSPdx for P25 and DMR trunking. Setup is similar to the RTL-SDR workflow. The RSPdx's wider IF bandwidth (10 MHz vs 2.4 MHz) doesn't change how many channels SDRTrunk can follow simultaneously — that's still one voice channel per receiver.
Performance on VHF/UHF: Police, Fire, and Airband
For VHF/UHF scanning — the primary use case for most readers of this site — the RSPdx performs well but doesn't dramatically outperform a well-set-up RTL-SDR V4. Sensitivity is comparable. The improved dynamic range helps if you're near a strong VHF/UHF repeater that would otherwise block adjacent frequencies, but most home setups don't hit that scenario.
P25 digital voice decoding quality is equivalent. Trunking behavior through SDRTrunk works the same way. ADS-B at 1090 MHz is solid but no better than a V4 with a dedicated ADS-B LNA.
The honest answer: if police and fire scanning is your primary use, the RSPdx is more receiver than you need. The RTL-SDR V4 handles VHF/UHF scanning fine.
Performance on HF: Where the RSPdx Earns Its Price
Below 30 MHz, the RSPdx genuinely earns its price premium. Shortwave broadcasts, amateur SSB and CW, WSPR beacons, medium wave stations — all benefit from the 14-bit ADC and the HDR mode when adjacent-channel interference is the limiting factor.
With a decent outdoor HF antenna (a 40-meter dipole or an end-fed halfwave), the RSPdx pulls in signals the RTL-SDR V4 loses in the noise. The dynamic range improvement is the dominant factor — the RSPdx can resolve weak signals that the V4 would bury under stronger adjacent-channel signals.
That said: antenna quality matters more than receiver quality for HF. An RSPdx connected to a poor indoor antenna will underperform a V4 connected to a well-positioned outdoor wire. If you haven't sorted antenna and location first, starting there will give you more improvement per dollar than upgrading the receiver.
If HF performance matters but you don't need the three antenna ports, the RSP1A provides the same 14-bit ADC at $80–90 less. You lose HDR mode and the port flexibility, but for a single-antenna HF setup it's the better value.
Frequently Asked Questions
Is the RSPdx worth it for police scanner use?
Not usually. The RTL-SDR V4 handles VHF/UHF scanning — police, fire, airband, P25 — just fine at a fraction of the price. The RSPdx's advantages are most pronounced on HF below 30 MHz, where the 14-bit ADC and HDR mode genuinely matter. For scanning in the 150–870 MHz range, the practical performance difference over a well-set-up RTL-SDR V4 is small.
Can I use the RSPdx on Mac or Linux?
Yes. SDRuno — SDRplay's own software — is Windows-only, but the RSPdx works on Mac and Linux through SDR++ or CubicSDR with the SDRplay plugin installed. The plugin is free and actively maintained. Most SDR++ features work identically across platforms, so Mac and Linux users aren't missing much beyond SDRuno's polished UI.
What's the difference between the RSP1A and the RSPdx?
Both use a 14-bit ADC and cover 1 kHz to 2 GHz. The RSPdx adds three antenna ports (A, B, C) versus the RSP1A's one, and HDR mode on Port A for high-dynamic-range HF reception. If you only need one antenna connection and don't do serious HF work near strong broadcast stations, the RSP1A saves $80–90 for almost identical performance on VHF/UHF.
Does the RSPdx replace two RTL-SDR dongles for P25 trunking?
No. For P25 Phase II trunked systems you need simultaneous reception on two frequencies — a control channel and a voice channel. The RSPdx is a single receiver, just like each RTL-SDR dongle. To track a Phase II system, you still want two receivers. The RSPdx's wide bandwidth doesn't change this requirement.
What software works with the RSPdx?
On Windows: SDRuno (SDRplay's own software), SDR++, HDSDR with the EXTIO DLL, and SDRangel. On Mac and Linux: SDR++ with the SDRplay API and plugin, CubicSDR with the SDRplay plugin. SDRTrunk supports the RSPdx for P25/DMR trunking on all platforms. The SDRplay API must be installed first; download it from sdrplay.com before installing any front-end software.
Is the RSPdx good for ADS-B?
Adequate, but overkill. A single RTL-SDR V4 with a dedicated ADS-B LNA handles 1090 MHz fine and is a proven setup for aircraft tracking with dump1090 or PiAware. The RSPdx will receive ADS-B without issue, but you won't gain meaningful range over a well-configured RTL-SDR. If ADS-B is your primary use, save the money and use a purpose-built setup.