The Cable-Modem Chip That Became a Ham Radio

In 2012, a single-board ham SDR transceiver cost around nine hundred dollars and put out half a watt. Today its direct descendant costs $269 and puts out five watts. This is the story of how that happened — and of the small green board that made it possible.

The Hermes-Lite 2 is one of the most interesting radios in amateur radio, and one of the most misunderstood. It is a full HF transceiver, entirely open source down to the fabrication files, and it exists because one engineer noticed that the chip inside a cable modem was, if you looked at it correctly, most of a software-defined radio.

You will also see it written as the Hermes-Lite 2+. That is a different thing than most people assume, and we will get to exactly what it is — and what it is not.

Where it came from

To understand the Hermes-Lite, you have to start with the thing it is lite compared to.

openHPSDR and the board stack

The openHPSDR project — High Performance Software Defined Radio — grew up around TAPR, the amateur radio research organisation that has been publishing open hardware for decades. Its early architecture was a backplane full of cards, each doing one job: Mercury for receive, Penelope for transmit, Metis for the Ethernet interface, all plugged into an Atlas backplane.

It worked, and it performed superbly. It was also a stack of expensive boards.

In 2009 the project decided to collapse that stack onto one board. The receive and transmit logic went into a single FPGA that year; the Ethernet interface was folded in during 2010. The result was named Hermes, and by mid-2012 you could buy one from TAPR.

Hermes was a genuinely impressive piece of engineering: a direct-sampling receiver and direct-up-conversion transmitter covering roughly 0 to 55 MHz, gigabit Ethernet, and an RF-quiet switching supply so it could run from a single 13.8 V line.

It also cost $895 for TAPR members and $940 for everyone else, and its transmitter produced 500 milliwatts. Half a watt. If you wanted to actually work anyone, you added an amplifier on top of that price.

The observation that changed the price

In 2014, Steve Haynal, KF7O, started a project based on a simple and slightly subversive observation.

Analog Devices made a part called the AD9866. It is described in its own datasheet as a broadband modem mixed-signal front end — which is to say, it was designed to sit inside cable modems and similar consumer broadband gear. It is a mass-produced commodity component, and it is cheap for exactly that reason.

It also happens to contain, in one package, very nearly everything an HF software-defined radio needs: a low-noise amplifier, a 12-bit analogue-to-digital converter, and a 12-bit digital-to-analogue converter, all fast enough to work directly at high frequency.

This is the whole trick. A cable modem front end and a direct-sampling HF transceiver need the same thing: convert a wide chunk of radio spectrum straight to numbers, and convert numbers straight back to radio. The cable industry ordered that part by the million. Amateur radio got to buy it at cable-industry prices.

The Hermes-Lite project put an FPGA between that chip and an Ethernet jack, and spoke the openHPSDR protocol that Hermes already used — which meant it inherited, on day one, all the software the openHPSDR community had spent years writing.

Hermes-Lite 1.x — the experimenter era

Hermes-Lite 1.x, 2015. The radio is the small board in the middle; the thing on the left is the Arrow BeMicro SDK FPGA card it could not run without. Photo: James Ahlstrom, N2ADR.

The first generation was not a product. It was a bare board that could not run on its own: it needed a companion FPGA card — an Arrow BeMicro SDK, CV or CVA9 — plugged into it to do the digital heavy lifting. You bought board sets from Tindie, sourced the FPGA card separately, and built the thing yourself.

Roughly 100 Hermes-Lite 1.x units were built by experimenters around the world from 2014 onward. The BeMicro cards have since become hard to find, and version 1 is retired — the project's own repository is now marked deprecated and points at its successor.

But it proved the point. The cable modem chip worked.

Hermes-Lite 2

The Hermes-Lite 2.0 board. FPGA, ethernet, AD9866 front end, 5 W amplifier and band filtering, all on one board - no companion card. Photo: Makerfabs, who produce it for the project.

Version 2 is what happens when a proof of concept grows up. The FPGA, the Ethernet interface and the AD9866 all moved onto one board, with a 5 W power amplifier and band-selectable low-pass filtering included. No companion card, no stack.

Over 500 Hermes-Lite 2.0 units have been built. It is entirely open source and open hardware — not just the schematics, but the fabrication files and the tools used to design them.

The specifications that actually matter

Two of those numbers deserve a moment. Twelve bits is modest — a Flex-class radio uses a far deeper converter, and the Hermes-Lite does not pretend otherwise. And 76.8 MHz is the real ADC clock; you will occasionally see other figures quoted around the internet, but the project's own FAQ is unambiguous.

What you get for twelve bits is a radio that costs less than a decent handheld.

The receive chain. The radio's whole job is to turn radio waves into numbers and put them on a wire.

Transmit is the same road walked backwards. Your computer builds the signal; the radio makes it RF and amplifies it to five watts.

What is on the back, and what is not

The board itself gives you a DC barrel jack, an RJ45, an antenna connector with an internal transmit/receive relay, a secondary low-power RF output, and a 3.5 mm KEY jack — tip grounds for CW keying, ring grounds for PTT, and the state of both is sent up to the PC so your software can react.

There are also expansion headers: an ATU interface, a DB-9 serial connector for band selection, an optoisolator connection, and a TX feedback input for PureSignal predistortion.

What there is not is any audio hardware. No microphone jack. No headphone jack. No speaker. No local sidetone.

The part people get wrong

The Hermes-Lite 2 is not a standalone radio, and it was never trying to be.

It has no knobs, no display, and no audio path of its own. It digitises radio spectrum, pushes the samples out over Ethernet, and a computer does everything else — demodulation, filtering, noise reduction, the user interface, and the audio. Transmit runs the same way in reverse.

This is not a shortcoming that someone forgot to fix. It is the openHPSDR architecture working as designed, and it buys you something real: because the radio is a network device rather than a USB peripheral, it can sit at the antenna, in the shed, or at a remote site, and you can operate it from anywhere you can reach it on the network.

The seam. Everything to the right of the ethernet jack is your computer — which is why the radio can sit at the antenna, and why it does nothing without a host.

The trade is equally real. No computer, no radio. Budget for the host as part of the station.

The software you get for free

Speaking the openHPSDR protocol means the Hermes-Lite 2 inherited a mature software ecosystem instead of having to grow one. Here is that ecosystem in order of first release, which also happens to be the clearest way to see how deep the lineage runs — the oldest entry predates the Hermes-Lite by eleven years, and the newest is still being written.

• 2003 — PowerSDR · Windows · Legacy. Born with FlexRadio's SDR-1000 and released as open source, then carried into openHPSDR (as mRX PS) by Bill Tracey, KD5TFD and Doug Wigley, W5WC. Still the reference for protocol 1 and supports PureSignal — but its last release was March 2018, and Thetis is its successor.
• 2008 — Quisk · Windows, Linux, Raspberry Pi · Actively maintained. Open source, written and still looked after by James Ahlstrom, N2ADR — who also designed the popular add-on filter board.
• 2010 — SDR Console · Windows · Actively developed. A mature, polished package from Simon Brown, G4ELI. Free to use.
• 2016 — piHPSDR · Linux, Raspberry Pi · Actively developed. Started by John Melton, G0ORX/N6LYT and carried forward largely by DL1YCF. CAT and FLDIGI integration.
• 2018 — SparkSDR · Windows, Mac, Linux, Raspberry Pi · Supported. Written by Alan Hopper, M0NNB. Free, easy to install, strong at multi-band skimming — and one of the few that treats the Hermes-Lite as its primary radio rather than an afterthought.
• 2018 — linHPSDR · Linux · Maintained, quieter. Also from G0ORX. Low-latency CW and PureSignal support.
• 2019 — Thetis · Windows · Active again, after being archived. PowerSDR's designated successor, led by W5WC and then Richard Samphire, MW0LGE. Worth knowing the recent history: Richie archived the project on 2 April 2026, explaining that the codebase still rests on .NET Framework 4.8 and on SharpDX for rendering — and SharpDX is itself an archived project — so multiple-receiver work would need a display-engine rewrite. He then reopened it on 2 July 2026 for a substantial remote-operation push: a permission and state system, Opus audio, and remote web and Windows clients. What matters for Hermes-Lite owners is that Reid, MI0BOT's dedicated HL2 build kept shipping straight through it all — releases in February, April, May and June 2026. For most HL2+ owners this is still the one.
• 2026 — AetherSDR · Linux, macOS, Windows · In development — Hermes-Lite support is being written right now. Built as a FlexRadio client, but HL2 receive support was merged in late July 2026, along with WSJT-X over TCI. Not an announced feature yet, and open items remain. More on this below.

CW Skimmer, hl2_tcp, OpenWebRX and GNU Radio also talk to it. For a radio at this price, that list is extraordinary — and it is the single strongest argument for the Hermes-Lite over a cheaper one-off design. Nothing else at $269 arrives with twenty years of software already written for it.

A note on OpenHPSDR Zeus. Zeus is a modern browser-style console that supports the Hermes-Lite 2, and it is worth understanding before you install it. Zeus ships as two halves under two licences: the station engine — transport, DSP, transmit control — is GPL 2.0 or later with full source published, while the interface and its Link launcher are proprietary. The project is open that the engine is GPL because it builds on Thetis, WDSP, piHPSDR and DeskHPSDR, and that the interface is original work.

Two practical points. From version 1.0, Zeus is delivered through Link, which requires you to sign in with your QRZ callsign and reauthorize at least once every 24 hours. It runs everything locally and works offline within that window, but for multi-day portable operating, Field Day on batteries, or a remote site without reliable internet, that is a constraint worth planning around — and one none of the other software on this page imposes.

The licensing split has been contested within the openHPSDR community, with strong opinions on both sides. We are not going to referee that. We will note only that on a radio whose entire appeal is being open all the way down to its fabrication files, “which half is open” is a fair question to ask before you download.

So what is the “+”?

The front panel that gives the "+" its name. PHONES, MIC and KEY on the right are what the companion board adds. Photo: Robert, WA2T.

Here is the first thing to be clear about: there is no such product as a “Hermes-Lite 2+” from the Hermes-Lite project. It is not a model, a revision, or an official tier.

A Hermes-Lite 2+ is a standard Hermes-Lite 2 with a third-party companion board added — the AK4951 Companion Board, sold by Robert, WA2T of WA2T Designs. Fit the board, load the matching gateware, and the project's own front panel calls it an HL2+.

Where the companion board came from

The origin story here is worth telling, because it is open source working exactly as intended.

The design did not start with WA2T. It started with Takashi, JI1UDD, who built an AK4951 codec board and custom gateware for the Hermes-Lite 2. Robert, WA2T, took that work as a starting point, redesigned the board for production, and put it into the hands of people who did not want to fabricate their own. In his own words on the project mailing list:

I designed the board using something that Takashi, JI1UDD originally did for the Hermes Lite 2 SDR as a starting point.

Look closely at the silkscreen on the board itself and you will see both callsigns: JI1UDD/WA2T. The gateware you load is still derived from Takashi's. That credit surviving all the way onto the copper is a small thing, and a good one.

The AK4951 Companion Board (V4.0 shown; V4.1 is current). The silkscreen reads JI1UDD/WA2T - Takashi's original design and Robert's production version, credited together on the copper. Photo: Robert, WA2T.

What it actually adds

The AK4951 is an audio codec. What the companion board really does is give the radio local audio hardware, plus a hardware CW keyer and a couple of accessory control interfaces.

The current hardware is version 4.1. The kit ships pre-assembled and tested and includes the board, new HL2+ end plates for the 40 mm case, a DB-9 ribbon cable with mounting hardware, a mounting bracket, a power switch with a two-wire harness and header. You supply a speaker, a few M3 screws and washers, and — if you want PureSignal — an SMA bulkhead pigtail.

It is not quite plug-and-play. Installation requires you to remove ferrite bead FB28 from the underside of the Hermes-Lite 2 board before fitting the companion board, drill an M3 hole in the case side for the mounting bracket, and flash new gateware to the FPGA. None of that is difficult, but all of it involves a soldering iron and a drill, so plan for it.

The myth worth putting down

Once you learn that the “+” adds a microphone jack and headphones, the obvious conclusion is that it turns the Hermes-Lite 2 into a standalone radio you can operate without a computer.

It does not. Steve Haynal, KF7O — the project's designer and lead — has answered this directly on the mailing list, and there is no gentler way to put it than he did:

The AK4951 companion board is just an expensive ethernet sound card. All microphone data is sent to the host software for modulation. All demodulated data goes from the HL2 to the host software for demodulation and then back to the HL2 if you have a AK4951 companion card.

Audio into that MIC jack is digitised, sent over Ethernet to the PC, modulated there, and sent back. The radio still cannot demodulate or modulate anything by itself. A host running SDR software is required, with or without the companion board.

On a stock Hermes-Lite 2 your audio never touches the radio at all.

With the companion board fitted, the jacks move to the radio — but the audio still round-trips to the PC. The local keyer and sidetone are the exception.

What the “+” genuinely fixes is where your ears and your fist connect. You plug headphones and a microphone into the radio instead of into the computer, and the CW keyer and sidetone are generated in hardware rather than at the far end of a network round trip. For CW operators especially, that last point is the entire reason the board exists — a sidetone that lags your keying by a variable amount is genuinely unpleasant to use.

It is a real improvement to the operating experience. It is not independence from the computer.

What it costs, and how you get one

What arrives: the companion board, new front and rear end plates, a DB-9 ribbon cable, power switch and harness, and a mounting bracket. You add a speaker and a few screws. Photo: Robert, WA2T.

The most important sentence on WA2T's site is this one, in capitals:

HL2 and HL2+ are not available assembled/turn-key. You must buy the parts and build.

Neither the base radio nor the “+” version arrives as a finished transceiver. This is a build, and the project is explicit that it is aimed at builders and experimenters rather than at people who want to unbox a radio and get on the air.

Prices as published in July 2026 — check before ordering, they drift.

• Hermes-Lite 2 core board — $269 from Makerfabs, who produce it for the project.
• N2ADR filter board — $52.80. James Ahlstrom's add-on filter board.
• IO board — $52.80.
• Enclosure — $16.90.
• AK4951 Companion Board kit — ordered directly from Robert, WA2T. Contact him for current pricing; kits have been in stock and shipping.
• Rack-mount end plates — $20 including US shipping for the first set, $15 for each additional set up to three, or $15 if added to a companion board order. The plates measure 122 mm by 41 mm and need a user-supplied 1U blank with the cutout made.

You will also need a host computer, a 12 V supply capable of 2 A, and an antenna. And if you want to work more than the quietest DX with five watts, an amplifier — which is precisely why the companion board bothers to include Hardrock-50 control.

The honest limitations

A radio you cannot criticise is a radio you do not understand. In no particular order:

• Twelve bits is twelve bits. This is a QRP-class direct-sampling receiver at a QRP-class price, not a contest-grade front end. On a crowded band next to a strong local signal, you will find its limits.
• Five watts. It is a QRP radio. That is a feature if you want it and a wall if you do not.
• No 6 m. The original Hermes covered it. The Lite does not.
• You must build it. No turn-key option exists for either version.
• The “+” needs surgery. Removing FB28 and drilling the case are not reversible in an afternoon.
• The computer is mandatory, and its performance and audio configuration become part of your radio's performance.
• Support is a community, not a company. Makerfabs tests boards before shipping and says plainly that it does not provide usage help — questions go to the project's group, where the answers are genuinely good but come from volunteers.

Where it goes from here

The companion-board ecosystem has kept growing, and it is worth knowing that the AK4951 board is not the only option. Takashi, JI1UDD, also published HL2-PA30, a 30 W amplifier and filter companion board designed to stack with the Hermes-Lite 2 and the AK4951 board inside a taller Makerfabs enclosure. Other builders have combined codec, power control and filtering onto single stacked boards of their own.

That is the real point of open hardware, and the reason this radio is worth a club's attention even if you never buy one. The schematics are public. The gateware is public. The fabrication files are public. When somebody wants a feature, they can add it — and when they do, the credit tends to stay on the board.

A cable modem chip, a repurposing idea, and twelve years of people building on each other's work. That is a $269 HF transceiver with ten times the transmit power of the $900 board it descends from.

Visit the Hermes-Lite project →

Links

• hermeslite.com — the project's home page.
• Hermes-Lite 2 wiki — FAQ, hardware, gateware, protocol and software documentation.
• GitHub — all open source hardware, gateware and software.
• hermeslite2plus.com — Robert WA2T's AK4951 Companion Board, installation guides and ordering.
• Makerfabs — where the boards are produced and sold.
• Hermes-Lite Google Group — the project's discussion list.
• HL2-PA30 — Takashi JI1UDD's 30 W amplifier and filter companion board.

One more thing, and it is a good one

The newest entry in that table ties this article to the last one we published. AetherSDR — the free, open-source SDR client we wrote about in SDR Without a Radio — was built as a client for FlexRadio hardware. It is now growing native Hermes-Lite support, and that work is happening as we write this.

In the last two weeks of July 2026 the project merged Hermes-Lite 2 receive support, vendored a new DSP library for it, got WSJT-X working over TCI through a Hermes-Lite, and fixed reconnection handling. It is not finished — transmit and some signal-path details are still open, and the project has not announced it as a feature yet. Watch it rather than rely on it.

But the direction is worth noticing. A $269 open-source transceiver driven by a free open-source cockpit that runs natively on Linux, macOS and Windows is a genuinely new proposition, and neither half of it asks you for a licence fee.

We will write that up properly when it lands, with the radio on the bench and the software driving it.

This article is a researched explainer rather than a bench review: every specification is taken from the Hermes-Lite project's own documentation, WA2T Designs' published material, or the project mailing list, and specifications and prices are as published in July 2026. Photographs are credited to their owners in the captions. If you are running a Hermes-Lite, come and tell us how you are getting on with it — we would rather publish your experience than our reading.