SDR Receivers
RTL-SDR Blog v4, Airspy, SDRplay, KrakenSDR — receive-only software-defined radios from $30 to $1k.
The receive-only end of the SDR landscape — dongles and boxes that let you point a tuner at any frequency from DC to 6 GHz and stream IQ samples to a PC. Cheap RTL-SDRs democratized this around 2012; in 2026 a $30 dongle still does 90% of what most people need.
Pair a receiver with software from SDR Software, drivers from SDR Driver Abstractions, and decoders from Aviation Decoders / Marine AIS / Trunked Public Safety / Weather Satellites. For 433 MHz device snooping see Sub-GHz & RTL_433; for an SDR as a bench instrument see Spectrum & VNA; for the canonical Pi+RTL-SDR ADS-B build see Classic Pi Projects.
RTL-SDR (the $30 default)
- ★ RTL-SDR Blog v4 — R828D tuner + RTL2832U; 500 kHz – 1.766 GHz with HF direct-sampling extension to ~28 MHz; SMA, TCXO, bias-T. The 2026 default; ~$35.
- RTL-SDR Blog v3 — older R820T2 chipset; still works fine; superseded.
- ★ Nooelec NESDR SMArt v5 / SMArt XTR — competing premium RTL-SDR; TCXO, SMA, ESD protection. Excellent build quality; ~$30–$45.
- Generic R820T2 dongles — $10 eBay specials; drift, no TCXO, plastic SMA-via-MCX adapters; OK for first experiments only.
- NooElec NESDR Nano 3 — USB-stick form factor; portable; same RTL2832 core.
RTL-SDR catches everything from FM broadcast through pagers, ADS-B (1090 MHz), AIS (162 MHz), TPMS, weather sensors, NOAA APT, METEOR weather sats, ham bands, and trunked public-safety voice. The tuner is the limit; replace it for premium reception.
Airspy (mid-tier, premium HF and VHF)
- ★ Airspy HF+ Discovery — DC – 31 MHz + 60 – 260 MHz; ~768 kHz IQ; best-in-class HF and VHF SNR for under $200. The "I do shortwave / amateur HF seriously" pick.
- ★ Airspy R2 — 24 MHz – 1.8 GHz; 10 MSPS IQ; better dynamic range than RTL-SDR; ~$170.
- Airspy Mini — same chipset, smaller package; ~$120.
Airspy gear is closed-firmware but well-supported across SDR# / SDRangel / GNU Radio via libairspy.
SDRplay (UK; broad coverage)
- ★ SDRplay RSP1A — 1 kHz – 2 GHz; 14-bit ADC; 10 MHz bandwidth; ~$120. Excellent broadband receiver.
- SDRplay RSPdx / RSPdx-R2 — flagship single-tuner; HF performance optimized; multiple antenna inputs; ~$280.
- SDRplay RSPduo — dual-tuner (run two frequencies simultaneously); ~$320.
- SDRplay RSP1B — newer entry-level update to the RSP1A.
SDRplay's API is closed-source but they ship Linux/Mac/Windows drivers and have first-class SoapySDR + GNU Radio + SDR++ support. Note: SDRuno (their bundled app) is Windows-only and closed.
KrakenSDR (5-channel coherent)
- ★ KrakenSDR — 5 coherent RTL-SDR receivers in one box, all phase-locked. The hobbyist direction-finding standard. ~$500.
- See Direction Finding for what to do with it.
Niche / specialist receivers
- Perseus SDR — 0 – 30 MHz HF receiver; legendary dynamic range; ~$900. Closed firmware, beloved by serious shortwave listeners.
- Elad FDM-S2 / S3 — Italian HF SDR receivers; broadcaster / DXer favorites.
- WinRadio Excalibur — Australian premium HF SDR; expensive.
- Cloudy KiwiSDR — open-hardware 0–30 MHz BeagleBone-based receiver; shareable over the web (most public web SDRs in 2026 are KiwiSDRs). ~$300 for the kit.
- WebSDR.org / KiwiSDR.com — listen to other people's receivers worldwide for free, no hardware needed.
Choosing a receiver
| Use case | Pick |
|---|---|
| First SDR, anything | RTL-SDR Blog v4 |
| HF shortwave / 80–10 m ham | Airspy HF+ Discovery |
| Wide-band general purpose | SDRplay RSP1A or RSPdx |
| Two frequencies at once | SDRplay RSPduo |
| Direction finding / passive radar | KrakenSDR |
| Share an HF receiver online | KiwiSDR |
Antennas matter more than the receiver
- Discone — 25 MHz – 1.3 GHz general purpose; the standard scanner antenna.
- Dipole tuned to your band — cheap to make; outperforms anything broadband on its target band.
- Active loop / mag loop (Wellbrook / MLA-30+ / YouLoop) — for HF in noisy urban environments.
- 1090 MHz ADS-B antenna — cut to length; outdoor mount; cheap and dramatic improvement over rubber duck.
- LNA + filter — bias-T-powered low-noise amp + bandpass filter for ADS-B / NOAA / specific bands. Nooelec and RTL-SDR Blog sell good ones.
- Common-mode choke — kill computer / USB noise.
A $30 RTL-SDR with a $50 outdoor antenna beats a $500 SDR with a stock whip every time.
License / build notes
- RTL-SDR drivers (librtlsdr) — LGPL-3, Osmocom project; all the apps use it.
- Airspy / SDRplay — closed-source firmware; FOSS-friendly host APIs.
- KrakenSDR firmware — partially open; the host DOA software is open-source.
- Most cheap "RTL-SDR" dongles on Amazon are clones; the ones with TCXO and SMA cost only a few dollars more — buy those.
Pick this if…
- First SDR ever: RTL-SDR Blog v4.
- HF / shortwave focused: Airspy HF+ Discovery.
- Broad-spectrum hobby and research: SDRplay RSP1A.
- Direction finding / TDOA experiments: KrakenSDR.
- No hardware budget but you want to listen: KiwiSDR network on the web.
- Pure HF connoisseur with money: Perseus / Elad FDM-S3.