2026 – Thirteen current SDR Receivers and Transceivers

Thirteen current SDR receivers and transceivers, compared for one thing that matters most to those of us who still copy Morse by ear and chase weak SSB DX: HF CW and SSB receive performance. The grid rates each unit, identifies which ones can put your antenna on the web for visitors, lists supported software, published Sherwood Engineering measurements where they exist, instantaneous bandwidth, and noise-fighting capability — with practical notes for both shortwave listeners and licensed amateurs. Below the grid, a detailed companion write-up expands on every device, with sources footnoted at the end.

Reading the numbers

The Sherwood Engineering receiver table^[1] sorts by third-order dynamic range narrow spaced, and among these thirteen units only the Yaesu FT-710 and the original Microtelecom Perseus have been formally measured by Rob Sherwood, NC0B. Where a unit hasn’t crossed his bench, the grid quotes manufacturer specifications and clearly says so — treat those figures with the usual salt. Manufacturer dynamic-range claims, in particular, often describe wideband ADC headroom rather than the close-in, two-tone figure Sherwood measures, and the two are not comparable. The ratings themselves score HF CW/SSB receive quality only; a 4.5 for a US$169 receiver and a 5.0 for a US$5,300 transceiver say nothing about value, which is a judgement each operator makes against their own bank balance and noise floor.

The transmit-capable radios

Four of the thirteen can put a signal on the air, and they span three orders of magnitude in output power. The FlexRadio FLEX-8600^[2] is the receive champion of the group: dual Spectral Capture Units sampling at 245.76 Msps with 16-bit resolution digitise the entire 30 kHz–54 MHz range twice over, feeding up to four independent slice receivers on two antennas — which is what enables true diversity reception and single-radio SO2R contesting with OTRSP support for loggers like N1MM+. On transmit it delivers 100 W PEP from 160 through 6 metres with an internal tuner, full-duplex cross-band capability, and adaptive predistortion for an unusually clean signal. The catch for anyone hoping to share it: SmartLink remote access is genuinely excellent for the owner and invited operators, but every remote user needs SmartSDR client software and credentials. There is no anonymous browser path.

The FlexRadio Aurora AU-510M^[3] is the most technically interesting transmitter in decades. Rather than a linear amplifier chain, it uses polar modulation: the RF signal is decomposed into amplitude and phase components, each amplified by highly efficient switch-mode stages and recombined at the output.^[4] The result is 500 W PEP on HF (200 W on 6 m) at roughly 80 percent efficiency — against 40 to 60 percent for legacy amplifiers — which means only about 125 W of waste heat at full output and a complete 500 W station weighing 8 kg. The 500 W automatic tuner, the 80–264 VAC auto-sensing supply, and the Maestro touchscreen front panel are all in the same chassis; note it cannot run from 13.8 VDC, and it is rated for ICAS (25–50 percent) duty cycle, though FlexRadio reports testing two hours of continuous transmission. The receive side is a single SCU delivering FLEX-8400-class performance with two slices and two panadapters. The grid’s 4.8 is provisional: the first production batch shipped only in mid-2026, so the score rests on specifications and the proven FLEX-8000 receive architecture rather than independent lab data.

The Yaesu FT-710 AESS is the value proposition of the entire grid, and unlike most of the field its numbers are independently verified. Sherwood’s October 2022 measurements^[5] put third-order dynamic range at 106.5 dB at 2 kHz spacing with the preamp off, RMDR at 115 dB at 2.5 kHz, blocking at 129 dB, and a CW noise floor of −127 dBm — figures essentially identical to the FTdx10 at a lower price, and enough for a top-tier table placement. On transmit it produces 100 W on SSB, CW, and FM (25 W AM) from 160 through 6 metres through an internal tuner, and Sherwood measured composite transmit noise of −124 dBc/Hz at 2.5 kHz offset at full power — a spec that matters to anyone who has suffered a noisy neighbour transmitter on a contest weekend. The AESS acoustic system genuinely improves received audio through the matched external speaker. Its limitation as an SDR is architectural: there is no IQ output, so no wideband recording, skimming, or third-party SDR software — the band scope tops out at a 1 MHz span.

The Hermes-Lite 2^[6] proves what an open-source community can do with a US$1.60 broadband-modem chip. Designed by Steve Haynal, KF7O, around the Analog Devices AD9866 — a 12-bit transceiver-on-a-chip intended for cable modems — it covers 0 to 38.4 MHz receive with up to four simultaneous receiver slices at up to 384 kHz each, and transmits about 5 W PEP from 160 through 10 metres through the companion N2ADR low-pass filter board. Because it speaks the openHPSDR protocol over Ethernet, it inherits a mature software ecosystem: Thetis, SparkSDR, piHPSDR, Quisk, and deskHPSDR all drive it, and Thetis’s NR2 spectral noise reduction is arguably the best noise-reduction algorithm available to amateurs at any price. Five watts barely qualifies as QRP on SSB, so most owners pair it with an external amplifier; as a receive/exciter core for a homebrew station it is unbeatable at the price, and the entire hardware, gateware, and firmware stack is open for modification.

The native web receivers

Two devices in the grid were designed from the outset so that anyone with a browser and the URL can listen — no software, no account, no configuration. The KiwiSDR 2^[7], the second-generation hardware of John Seamons’ (ZL4VO/KF6VO) project, remains unique in that the owner and every guest use exactly the same web interface — there is no separate installed application at all. A standalone network appliance covering 10 kHz to 30 MHz with a 14-bit ADC and integrated GPS receiver, it supports multiple simultaneous guest channels (up to eight depending on configuration), each with independent tuning, mode, and waterfall. Its real moat is the ecosystem built over a decade: a worldwide public directory of hundreds of receivers, a reverse-proxy service for owners behind awkward routers, and an extension suite with no equal — GPS-timestamped TDoA direction finding across the global Kiwi network, DRM and weather-FAX decoding, WSPR and FT8 spotting, SSTV, and CW/RTTY decoders, all running in the browser. The receive performance is honest rather than exceptional, which is why it rates 3.6, but no other product turns an antenna into a public scientific instrument this easily.

The Web-888^[8] takes the KiwiSDR’s software concept and bolts it to considerably stronger hardware inherited from the RX-888: a 16-bit LTC2208 ADC digitising 61.44 MHz of spectrum in real time (1 kHz to 62 MHz, plus a separate 118–145 MHz VHF airband input), a Zynq7010 FPGA with dual ARM cores, a GPS-disciplined 0.5 ppm TCXO, and Gigabit Ethernet. The server software is a modified, open-source fork of the KiwiSDR codebase running on Alpine Linux with a read-only root partition to survive SD-card abuse, and it serves thirteen simultaneous browser channels, every one with its own waterfall — enough to park a guest receiver on every HF band at once. It also runs FT8, FT4, and WSPR skimmers onboard across all bands simultaneously, with CW skimming on the roadmap, and because it speaks the KiwiSDR websocket protocol, tools like kiwiclient and SuperSDR work with it directly. Two practical cautions from the community: use a well-filtered 5 V/2 A supply, and protect the ADC input — a strong local transmitter can destroy a converter chip that costs nearly as much as the whole receiver.^[9]

The dedicated receive-only instruments

The Elad Perseus22^[10] shares the grid’s top rating with the FLEX-8600 for a completely different reason. Its four receive channels — two covering 10 kHz to 70 MHz, two covering 70 to 225 MHz — are sampled synchronously by a 14-bit converter, and each pair supports true diversity processing: with two spaced or orthogonal antennas, the software can steer a spatial null onto a local noise source or interferer, achieving noise reductions conventional DSP cannot touch. Every channel carries its own analog front end with preselection filters, attenuators, and amplifiers, and image rejection is typically better than 70 dB. Bjarne Mjelde’s extended field review^[11] found it two to three decibels more sensitive than the original Perseus, while noting the young software’s rough edges — mouse-only tuning, a mandatory bundled power supply — and the obvious question of paying flagship money for 14 bits and 1.6 MHz of alias-free bandwidth when the same company’s FDM-S3 offers 16 bits and 24 MHz. The answer is diversity: for a DXer with real antenna options and real local noise, nothing else in this grid does what it does.

The Elad FDM-S3^[12] is the recording DXer’s instrument. Its 16-bit converter runs at a variable 98 to 122 MHz sample rate — chosen per band for favourable decimation ratios, a subtle trick that buys measurable sensitivity and dynamic range — and it will stream and record up to 24.576 MHz of contiguous spectrum, meaning an entire evening of the whole shortwave broadcast spectrum can go to disk for later analysis. Coverage runs 9 kHz to 108 MHz with two switchable HF antenna inputs (one with bias-tee power for an active antenna), a three-stage attenuator, a switchable preamp, and eight slots for the same plug-in preselector filter modules used across the ELAD line. The original Microtelecom Perseus^[13], Nico Palermo’s (IV3NWV) 2007 design, is the receiver that proved direct sampling could beat superhets: its 14-bit, 80 Msps converter behind a switched bank of preselection filters measured approximately 99 dB narrow-spaced dynamic range and 125 dB blocking on Sherwood’s bench^[14] — numbers that embarrassed contemporary flagship transceivers — and nearly two decades later the worldwide community of Perseus users still exchanges IQ recordings and runs remote servers on its built-in client/server protocol. The Elad FDM-DUO-R^[15] answers a different question: what if a proper SDR could also just be a radio? Standalone, it is a 9 kHz–54 MHz receiver with a real VFO knob, volume and filter controls, and a display; tethered, it streams 192 kHz IQ to FDM-SW2 or SDR Console. Ten user-populated preselector board slots, a documented CAT protocol, and a mute input for transmitter-proximity use make it an unusually station-friendly monitor receiver.

The Airspy HF+ Discovery^[16] deserves its reputation as the giant-killer. Its polyphase harmonic-rejection mixer architecture — unusual at any price, remarkable at US$169 — delivers a minimum discernible signal in the −141 dBm class and roughly 110 dB of dynamic range in a matchbox-sized enclosure. The trade is bandwidth: 768 kHz maximum, about 660 kHz alias-free, so it sees one band segment at a time and will never skim or record wide spectrum. Within that window, driven by SDR# or SDR Console, its weak-signal CW performance genuinely competes with everything above it in this grid, and behind a SpyServer (for SDR# clients) or OpenWebRX+ (for browser guests) it makes the highest-performance shareable receiver available for under US$200 all-in.

The wideband explorers

The last two entries are honest tools sold, occasionally, with dishonest expectations. The RigExpert Fobos SDR^[17] reads impressively on paper — 100 kHz to 6 GHz, 14-bit sampling, 50 MHz of continuous IQ over USB 3.0, and two phase-coherent HF direct-sampling channels — but independent reviewers, notably Matt of the TechMinds channel, found the front end wanting, with mirror images and overload even at low gain settings, and other early adopters reported similar results.^[18] The block diagram shows almost no preselection ahead of the converter, so its 86 dB claimed HF blocking range is optimistic in real-world band conditions. Where it earns its keep is as a coherent two-channel laboratory source for direction-finding, correlation, and diversity experiments with GNU Radio — a genuinely rare capability at the price. The DXPatrol MK4^[19], from Tony CT1FFU in Portugal, is the most transparent product here: an RTL2832-family receiver behind a proper HF upconverter, band filtering, input protection, and a shielded aluminium case, with independent HF and VHF/UHF antenna inputs. Its own published figures — a −117 dBm noise floor and about 77 dB of blocking range at 14 MHz^[20] — tell you exactly what an 8-bit converter can and cannot do. As a 100 kHz–2 GHz explorer for a beginner, a travel radio driven from an Android phone, or the engine of a casual OpenWebRX station, it is entirely fit for purpose; as a weak-signal HF DX receiver, it is not, and it does not pretend to be.

Sources, credits, and further reading

Particular credit is due to Rob Sherwood, NC0B, whose independent laboratory measurements remain the reference standard the entire industry is judged against; to Bjarne Mjelde, whose Arctic-latitude field reviews are among the most rigorous published anywhere; to Matt of TechMinds for honest hardware reviews; and to the open-source builders whose work underpins half this grid — John Seamons, ZL4VO/KF6VO (KiwiSDR), Steve Haynal, KF7O, and the SofterHardware community (Hermes-Lite 2), Nico Palermo, IV3NWV (Perseus), and the OpenWebRX and OpenWebRX+ maintainers whose software turns nearly any receiver into a public one.

1. Sherwood Engineering, “Receiver Test Data,” sorted by third-order dynamic range narrow spaced — sherweng.com/table.html
2. FlexRadio, FLEX-8600 Signature Series product page — flexradio.com; DX Engineering listing — dxengineering.com/parts/fri-flex-8600
3. FlexRadio, Aurora AU-510M product page — flexradio.com; Aurora series overview — flexradio.com/aurora
4. PileupDX, “FlexRadio Aurora FAQ” (polar modulation, efficiency, duty cycle, AC-only operation) — pileupdx.com/flexradio-aurora-faq
5. Sherwood Engineering, Yaesu FT-710 HF test results, 1 October 2022 (PDF, hosted by N9EWO) — qsl.net/n9ewo/sher_ft710.pdf
6. Hermes-Lite 2 project repository, Steve Haynal KF7O / SofterHardware — github.com/softerhardware/Hermes-Lite2
7. KiwiSDR project — kiwisdr.com; KiwiSDR 2 at DX Engineering (hardware, power-supply guidance) — dxengineering.com/parts/kwi-kiwisdr2
8. Web-888 product and design documentation — rx-888.com/web
9. Elekitsorparts Web-888 listing and community operating notes (supply filtering, ADC protection) — elekitsorparts.com
10. Microtelecom, Perseus22 product page — microtelecom.it/en/perseus-22; OnAllBands new-product spotlight — onallbands.com
11. Bjarne Mjelde, “The Microtelecom Perseus22,” field review v2, July 2024 (PDF) — groups.io/g/IRCA (PDF)
12. ELAD FDM-S3 (TCXO) at DX Engineering (variable sample rate, filter slots, 24 MHz recording) — dxengineering.com/parts/eld-fdms3-tcxo
13. Microtelecom Perseus SDR at DX Engineering — dxengineering.com/parts/mic-fdm-perseus
14. Sherwood Engineering receiver table, Perseus entry (added February 2008); see footnote 1
15. ELAD FDM-DUO-R at DX Engineering (preselector slots, CAT, mute input) — dxengineering.com/parts/eld-fdm-duor-b
16. Airspy, HF+ Discovery product page — airspy.com/airspy-hf-discovery
17. RigExpert, Fobos SDR product page and specifications — rigexpert.com
18. RTL-SDR.com, “TechMinds: A Review of the RigExpert FobosSDR,” September 2024 — rtl-sdr.com
19. DXPatrol, MK4 Ultra Wide-band Coverage SDR Receiver product page — dxpatrol.pt
20. DXPatrol MK4 specification sheet (PDF, hosted by Vibroplex) — vibroplex.com (PDF)