Comparing Software Defined Radios for Radio Astronomy
Here’s a compact, practical comparison of the popular low-to-mid cost SDRs you named (RTL-SDR v3/v4, ADALM-PLUTO, Ettus B210, LimeSDR family) plus a few other often-used SDRs (HackRF, Airspy, SDRplay) produced by ChatGPT 9 September 2025.
Short summary / recommended use
- Cheap general receive / hobby scanning, ADS-B, FM, NOAA etc: RTL-SDR v3 / v4. Low cost, RX only (or RX-only direct sampling on HF). (SparkFun Electronics, HamTactical)
- Low-cost TX + RX (experimental, teaching, prototyping): ADALM-PLUTO (small, USB, 1×Tx/1×Rx, 325 MHz–3.8 GHz). (wiki.analog.com, Mouser Electronics)
- Multi-channel MIMO / higher bandwidth + professional hobbyist: LimeSDR / LimeSDR-USB (2×2 MIMO, wide band, ~61.44 MSPS). (limemicro.com)
- Full-featured, coherent multi-antenna, research grade (but pricier): Ettus USRP B210 (2×2, 70 MHz–6 GHz, USB3, 12-bit ADC). (Ettus Research, digilent.com)
- Tx/Rx wideband hacker board (cheap & popular for experiments): HackRF One (1 MHz–6 GHz, half-duplex, ~20 MSPS). (greatscottgadgets.com, pysdr.org)
- Best in dynamic range & HF performance for receive (no TX): Airspy HF+ / HF+ Discovery and SDRplay RSP series (14-bit RSP1A/RSPdx) — great when strong-signal handling and sensitivity matter. (airspy.com, SDRplay)
Side-by-side (key specs)
(Each line gives the most relevant, practical specs)
- RTL-SDR Blog V3 / NooElec v4 (RTL2832U + R820T2 family)
- Frequency: 500 kHz – 1.7–1.8 GHz (HF via direct sampling / diplexer on V3). ADC: 8-bit. Bandwidth: a few MHz practical. RX only (no native TX). Very low cost (£20–£60 depending on kit). (SparkFun Electronics, RTL-SDR)
- ADALM-PLUTO (Analog Devices “PlutoSDR”)
- Frequency (stock): ~325 MHz – 3.8 GHz (can be extended by firmware hacks). 1×TX + 1×RX, 12-bit ADC/DAC, up to ~61.44 MSPS and ~20 MHz tunable channel BW typical. USB-powered, small, cheap for a transceiver. Good for learning, SDR comms and prototypes. (wiki.analog.com, Mouser Electronics)
- Ettus USRP B210
- Frequency: 70 MHz – 6 GHz. 2×TX / 2×RX coherent MIMO, 12-bit ADC/DAC, up to ~56 MHz instantaneous BW, USB3 interface. Research/higher-end hobbyist (better driver/API UHD + GNU Radio support). (Ettus Research, digilent.com)
- LimeSDR / LimeSDR-USB (LMS7002M)
- Frequency: ~100 kHz – 3.8 GHz. 2×TX / 2×RX, up to ~61.44 MSPS (some silicon notes allow wider), 12-bit sample depth, FPGA onboard, USB3. MIMO capable and widely used for cellular/Wi-Fi experiments. (limemicro.com)
- HackRF One
- Frequency: 1 MHz – 6 GHz. Half-duplex transmit/receive, up to 20 MSPS, 8-bit samples. Low cost for transmit-capable board but limited dynamic range and half-duplex operation. Good for RF experiments and teaching. (greatscottgadgets.com, RTL-SDR)
- Airspy HF+ / Airspy HF+ Discovery
- Receive only. Excellent HF/VHF sensitivity and dynamic range, polyphase preselectors, very good strong-signal handling — targeted at high performance receive (not TX). Useful when HF performance matters. (airspy.com)
- SDRplay RSP1A / RSPdx
- Receive only. 14-bit ADC, continuous coverage from <1 kHz up to ~2 GHz (RSPdx 1 kHz–2 GHz), good dynamic range and software ecosystem (SDRuno). Ideal for multi-band receiving with good SNR. (SDRplay)
Pros / Cons — practical notes
- RTL-SDR (v3/v4)
- Pros: cheapest, huge community, great for learning and receiving many signals.
- Cons: 8-bit ADC, limited dynamic range and selectivity; not suitable for serious HF RX without hacks; no native TX. (SparkFun Electronics, RTL-SDR)
- PLUTO
- Pros: TX+RX, small, inexpensive for a transceiver, decent sampling rates for many comm experiments.
- Cons: single RX/TX channels (no MIMO), stock range limited to 325–3800 MHz (though hackable). Good balance TX/RX vs cost. (wiki.analog.com, Mouser Electronics)
- LimeSDR
- Pros: 2×2 MIMO, wide freq range and good bandwidth, used for LTE/5G/Wi-Fi experiments. FPGA onboard for more advanced processing.
- Cons: more complex to set up; higher price and steeper learning curve. (limemicro.com)
- USRP B210
- Pros: solid drivers (UHD), coherent 2×2 MIMO, research-grade performance and predictable behaviour.
- Cons: more expensive, larger, needs USB3 and a reasonably capable host. (Ettus Research, digilent.com)
- HackRF One
- Pros: affordable TX/RX wideband board, popular for experiments and pentesting (with legal caution).
- Cons: half-duplex, 8-bit ADC (lower dynamic range). (greatscottgadgets.com, RTL-SDR)
- Airspy / SDRplay (receive-focused)
- Pros: excellent RX sensitivity and linearity (Airspy HF+ particularly for HF), 14-bit ADC on SDRplay gives better SNR than cheap 8-bit dongles. Strong software ecosystems.
- Cons: no TX (receive only). Choose these when receiving quality > bandwidth is the priority. (airspy.com, SDRplay)
Which to pick for typical projects
- Listening to VHF/UHF broadcast, ADS-B, NOAA, satellite SO-50 etc: RTL-SDR v3/v4 or Airspy (if you want better sensitivity). (SparkFun Electronics, airspy.com)
- Building small SDR transmitter experiments (FSK, simple LTE experiment, demos): ADALM-PLUTO (single TX) or HackRF (if you need wider frequency coverage and don’t need full duplex). Be mindful of local transmission regulations. (Mouser Electronics, greatscottgadgets.com)
- MIMO work, LTE/5G prototyping, real-time baseband experiments: LimeSDR or Ettus USRP (Lime if budget + USB3, Ettus for robust research support and UHD). (limemicro.com, Ettus Research)
- When HF receive performance (weak signals, contesting, shortwave listening) matters: Airspy HF+ or SDRplay RSPdx / RSP1A. (airspy.com, SDRplay)
Price bands (very approximate, retail)
- RTL-SDR v3/v4: £20–£60 (kits more). (HamTactical, SparkFun Electronics)
- ADALM-PLUTO: ~£80–£140 (varies). (Mouser Electronics)
- HackRF One: ~£250–£350. (RTL-SDR)
- LimeSDR / LimeSDR-USB: ~£250–£400 (depends on board and vendor). (limemicro.com)
- Ettus USRP B210: ~£900+ (often more; Ettus pricing and reseller markups vary). (digilent.com)
- Airspy HF+ / SDRplay RSP1A / RSPdx: £100–£300 depending on model. (airspy.com, SDRplay)
Important practical warnings
- Transmit legally. Many of these devices can transmit — always obey your country’s radio regulations and only transmit on authorised frequencies / with proper licence.
- Host/system requirements. LimeSDR and Ettus devices need USB3 and a decent host CPU for wideband streaming; Check driver / UHD / libiio compatibility for your OS. (digilent.com, limemicro.com)
1. One-Page Printable Comparison Sheet
| SDR Model | Freq. Range | RX / TX | Sample Depth / BW | Channels / MIMO | Price (approx) | Strengths | Drawbacks |
|---|---|---|---|---|---|---|---|
| RTL-SDR v3 / v4 | ~500 kHz – 1.7–1.8 GHz (with HF diplexer on v3) | RX only | 8-bit, few MHz | 1 channel | £20–£60 | Ultra-cheap, huge community, ideal for general scanning and sdrplay etc. | Poor dynamic range, limited HF, no native TX. |
| ADALM-PLUTO | ~325 MHz – 3.8 GHz (firmware‐hackable higher) | RX + TX | 12-bit, ~20 MHz (61 MSPS FIFO) | 1 RX + 1 TX | £80–£140 | Inexpensive transceiver, portable, great for comm prototypes. | Not MIMO, limited native TX power/freq. |
| Ettus USRP B210 | 70 MHz – 6 GHz | RX + TX (2×2 MIMO) | 12-bit, ~56 MHz BW | 2 RX + 2 TX pair, coherent | £900+ | Research-grade, good UHD support, robust multi-antenna. | Expensive, needs USB3 host, higher complexity. |
| LimeSDR / LimeSDR-USB | ~100 kHz – 3.8 GHz | RX + TX (2×2 MIMO) | 12-bit, ~61 MSPS | 2 RX + 2 TX | £250–£400 | Wideband, MIMO capable, FPGA onboard, great for LTE/Wi-Fi experiments. | Steeper learning curve, more setup work. |
| HackRF One | 1 MHz – 6 GHz | RX + TX (half-duplex) | 8-bit, ~20 MSPS | 1 channel, half-duplex | £250–£350 | Affordable TX/RX board, versatile, good for hacking/teaching. | Half-duplex only, low dynamic range. |
| Airspy HF+ / HF+ Discovery | HF/VHF bands (receive-only) | RX only | High performance (≥ 12-bit equiv.) | 1 RX | £100–£200 | Excellent HF sensitivity & dynamic range, strong signal handling. | RX only, more costly than RTL-SDR. |
| SDRplay RSP1A / RSPdx | <1 kHz – ~2 GHz (RSPdx) | RX only | 14-bit, wide continuous coverage | 1 RX | £100–£300 | Superior RX dynamic range, great software support (SDRuno). | RX only, mid-price. |
2. Recommendation for Amateur-Radio-Astronomy Projects
Given your practice as a general medical practitioner and your hobby in radio astronomy, you probably want:
- Excellent weak-signal detection
- Stability & sensitivity in the HF/VHF bands (e.g., 1420 MHz HI-line, solar bursts)
- Maybe multi-channel/MIMO capability for interferometry or beam-forming?
Here’s how the options line up for your use case:
Best focused receiver recommendation:
- SDRplay RSPdx or Airspy HF+ DiscoveryWhy?
- The RSPdx delivers excellent sensitivity and dynamic range from near-DC up to ~2 GHz, with clean, low-noise reception—great for capturing faint radio astronomy signals like the hydrogen line at 1420 MHz. Its 14-bit ADC provides substantially better performance than 8-bit receivers.
- The Airspy HF+ Discovery is particularly optimized for HF signals, with outstanding filtering and strong signal handling if you’re picking up lower-frequency astrophysical emissions or solar burst activity.
- Both are reasonably priced (~£100–£300) and are much more accessible than high-end MIMO gear.
If you want to explore MIMO/interferometry or transmit (e.g., experiments in radar or beaconing):
- LimeSDR-USB (for 2×2 RX/TX, wideband capabilities)
- USRP B210, if budget allows—solid research-grade performance and UHD support.
These two let you run custom digital beam-forming or interferometry experiments, and even transmit—for example, for local “ping” beacon tests. However, be cautious: transmitting astronomy-like signals (outside of passive reception) may have regulatory implications; always check your local Ofcom / licensing rules.
If you want ultra-budget receiver just to get started:
- RTL-SDR v3/v4 is cheap and ubiquitous for getting your feet wet in SDR astronomy—especially if you’re starting with satellites (like NOAA weather images) or VHF hydrogen line scanning. But for serious weak-signal RX work (e.g., HI line), you’ll want something with better dynamic range (like RSPdx or Airspy HF+).
3. Proposed Path Forward
- Primary SDR: Get an SDRplay RSPdx if your main goal is high-quality, all-band reception (especially HF/VHF/UHF).
- Backup/portable: Keep an RTL-SDR v4 on hand for quick setup, fun satellite passes, or backup.
- Advanced option: Add a LimeSDR-USB later if you want to experiment with MIMO or transmit-capable astronomy setups (e.g., radar reflections off the Moon; ensure legal compliance first!).
Perfect — I can merge what you just reminded me of with your radio‑astronomy targets (hydrogen line, meteors, Jupiter, SID, pulsars) and give a project-specific SDR guide with reasons. Here’s a consolidated, targeted overview:
Radio Astronomy SDR Guide by Project
| Project | Recommended SDR(s) | Reason / Notes |
|---|---|---|
| Hydrogen Line (1420 MHz) | SDRplay RSPdx, Airspy HF+ Discovery | Excellent sensitivity & dynamic range; 14-bit ADC on RSPdx gives clean, low-noise reception; HF+ Discovery strong for lower frequencies. Avoid 8-bit RTL-SDR for weak HI signals unless just starting. |
| Meteors (VHF, ~140 MHz) | RTL-SDR v3/v4 (budget), SDRplay RSP1A (better) | Cheap & easy; strong community support for meteor scatter decoding. RSP1A improves SNR and reduces interference. |
| Jupiter Decametric Bursts (~10–30 MHz) | SDRplay RSPdx, Airspy HF+ Discovery | Wide HF coverage, high sensitivity for weak signals, good filtering for strong broadcast interference. RTL-SDR possible with HF up-converter, but performance lower. |
| SID Monitoring (VLF, 3–30 kHz) | SDR‑IQ, SDR‑IP, SDRplay RSPdx | Ultra-fine spectral resolution needed; SDRplay works for passive monitoring; IQ/IP preferred for precise amplitude measurements and interferometry experiments. |
| Pulsars (400–1400 MHz typical) | SDRplay RSPdx (RX), LimeSDR / USRP B210 (advanced, multi-antenna) | Pulsars require sensitive, stable receivers; 14-bit ADC of RSPdx ideal. LimeSDR / USRP B210 enable MIMO interferometry for higher SNR. RTL-SDR can detect bright pulsars as a starting point. |
SDR Selection Notes
- Budget / beginner: RTL-SDR v3/v4. Cheap, huge community, good for initial experiments like meteor scatter or satellite passes.
- Focused receive: SDRplay RSPdx (~£150–£200). All-in-one HF/VHF/UHF coverage with excellent SNR — ideal for HI line, Jupiter bursts, pulsars.
- HF-optimized: Airspy HF+ Discovery (~£120–£200). Outstanding HF sensitivity, strong signal handling, perfect for solar bursts, Jupiter, and other HF targets.
- Advanced / MIMO: LimeSDR, USRP B210. Enables multi-antenna interferometry or experimental transmit; expensive, higher complexity, USB3 needed.
- Transmit / experimental: ADALM-PLUTO, HackRF One. Useful for teaching, prototyping, or controlled experiments; legal restrictions apply.
Practical Tips
- Antenna Matching
- Hydrogen line: half-wave dipole ~52 cm per leg at 1420 MHz.
- Meteors: dipole tuned for 137–150 MHz, inverted-V for more gain.
- Jupiter: long-wire or multi-wire inverted-V, up to 30 MHz.
- SID: loop antenna or large wire loop, very low frequencies.
- Pulsars: dish with feed tuned to target band, or multi-dipole array for MIMO.
- LNA & Filters
- Use low-noise preamp for weak signals.
- Bandpass filters reduce interference and improve SNR.
- Software
- SDRuno (SDRplay), GQRX, GNU Radio.
- Project-specific scripts exist for meteors, Jupiter, pulsars, SID.
Radio Astronomy SDR Cheat Sheet
1. SDR Selection by Project
| Project | Recommended SDR(s) | Key Notes / Why |
|---|---|---|
| Hydrogen Line (1420 MHz) | SDRplay RSPdx, Airspy HF+ Discovery | 14-bit ADC (RSPdx) → low-noise, high dynamic range; best for weak HI signals. HF+ Discovery excellent for HF/VHF. |
| Meteors (~140 MHz) | RTL-SDR v3/v4 (budget), SDRplay RSP1A | Cheap & easy; community scripts for meteor scatter; RSP1A improves SNR. |
| Jupiter Bursts (10–30 MHz) | SDRplay RSPdx, Airspy HF+ Discovery | Wide HF coverage; sensitive to weak bursts; good interference filtering. RTL-SDR + HF up-converter possible, less optimal. |
| SID Monitoring (VLF, 3–30 kHz) | SDR‑IQ, SDR‑IP, SDRplay RSPdx | Ultra-fine spectral resolution; stable amplitude measurements; interferometry possible with multi-channel SDRs. |
| Pulsars (400–1400 MHz) | SDRplay RSPdx (RX), LimeSDR / USRP B210 (advanced) | Sensitive, stable receivers; 14-bit ADC ideal; LimeSDR / USRP enable multi-antenna interferometry. RTL-SDR can detect bright pulsars for beginners. |
2. Antenna Guidelines
| Target | Antenna Type | Notes |
|---|---|---|
| Hydrogen Line | Half-wave dipole ~52 cm per leg | Horizontal dipole or inverted-V; feed with LNA. |
| Meteors | VHF dipole (~137–150 MHz), inverted-V | Multi-wire inverted-V improves gain; centre feed to SDR. |
| Jupiter Bursts | Long-wire or multi-wire inverted-V | Very long dipole (10–30 MHz), elevated for best reception. |
| SID Monitoring | Large loop / wire loop | Very low frequency; LNA helps; ground loop suppression important. |
| Pulsars | Dish or array of dipoles | Dish for target frequency; MIMO arrays for interferometry. |
3. LNA & Filters
- Low-Noise Amplifier (LNA) recommended at antenna feed for weak signals (Hydrogen line, Jupiter, pulsars).
- Bandpass Filters: Reduce interference; select filter according to target frequency.
- HF/ VHF filters: Essential for Jupiter bursts & meteor reflections.
- VLF filters: Needed for SID monitoring to reject mains and other noise.
4. Software Recommendations
| Task | Software |
|---|---|
| General SDR Control | SDRuno (SDRplay), GQRX, SDR# |
| Hydrogen Line / Spectroscopy | GNU Radio blocks, Python scripts (e.g., Radio JOVE tutorials) |
| Meteor Detection | Echoes, Meteor Demodulator, SDR# plugins |
| Jupiter Bursts | SDR# or GNU Radio, spectral waterfall visualization |
| SID Monitoring | SID Monitor software, custom GNU Radio flowgraphs |
| Pulsars | PSRCHIVE, SIGPROC, PRESTO, custom Python pipelines |
5. Practical Tips
- Beginner Setup: RTL-SDR v3/v4 + simple dipole → meteor scatter, satellites, basic HF work.
- Focused Receiver: SDRplay RSPdx → all-in-one high-quality HF/VHF/UHF reception.
- Advanced / Interferometry: LimeSDR / USRP B210 → multi-antenna MIMO experiments.
- Antenna Height & Orientation: Elevate antennas; orientation affects polarization & gain.
- Legal Compliance: Only transmit on authorized frequencies; check local regulations.
This sheet is optimized to fit on one page, so you can print and keep it near your setup for quick reference.