After selling my SunSDR, I found myself in a familiar spot: needing a radio and staring at a list of options that basically bottoms out at "spend a lot of money." I knew pretty quickly that I still wanted to stay in the SDR world. I have been a computer monitor guy from the start. Give me a waterfall display, clickable tuning, and DSP I can actually adjust, and I am happy. The idea of going back to a traditional rig with a physical VFO knob just did not appeal to me.
So I started looking at what was actually available. The Flex Radio is the obvious choice if you have the budget, but entry-level Flex hardware starts around five thousand dollars, and that is before you add anything else to the station. Apache Labs makes another capable SDR transceiver, but it sits in similar price territory and adds its own learning curve. Then there is the Hermes Lite 2.
The Hermes Lite 2 is an open-source HF SDR transceiver that connects over Ethernet, pairs with open-source software, and can be put together for around $400. That price difference is not subtle. When you can get something functional for four hundred dollars instead of five thousand, the question is not whether to consider it. The question is whether the performance gap is worth the gap in price. Based on what I have seen so far, for a lot of operators the answer is going to be no, that gap is not worth paying for.
This article covers the build, the software setup, and my first impressions after getting it on the air.
Why Open Source Matters Here
Before getting into the physical build, it is worth explaining why I specifically wanted something open source. This is not just a philosophical preference. For the kind of work I do, it has real practical value.
When I do projects that involve automated antenna switching, WSPR logging, or anything that needs to talk to the radio in a controlled way, I need to be able to get inside the software. A closed platform like Flex puts a wall between you and the internals. You can use what they expose through their API, and that is it. If you need something they have not built, you are waiting on them to build it or you are out of luck.
With the Hermes Lite 2 and Thetis, both the radio firmware and the control software are open source. If I need to extend Thetis to support something custom later, I can. If I want to understand exactly how the hardware is handling a particular signal path, the schematics are public. That kind of access changes what is possible with a station, and it is a big part of why the HL2 was attractive to me even before I looked at the price.
Four hundred dollars and full source access beats five thousand dollars and a black box, at least for the way I operate.
What Comes in the Box
The Hermes Lite 2 from Makerfabs arrives as a kit rather than a finished product. That sounds more intimidating than it actually is. The main board is already assembled and tested. You are not populating a bare PCB or touching a soldering iron. What you are doing is more like final integration: fitting the boards into the case, connecting the filter board, and getting the thermal management sorted before buttoning everything up.
The main radio board is a quality build. The PCB work is clean, the components are well placed, and it does not have that cheap feel that some budget RF hardware can carry. When you hold it you can tell someone put actual thought into the design rather than just making the least expensive thing possible.
You will want to order the optional filter board along with the main board. The filter board is not strictly required to get the radio working, but it adds bandpass filtering that makes a real difference in receiver performance. It is inexpensive and worth having from the start rather than adding it later. It slots in alongside the main board, and a short connector bridges the two. More on that in the assembly section.
Beyond the boards, the kit includes the aluminum case, end plates, hardware, and a heat sink shim. That shim is a key piece that deserves a little more attention than a quick mention, which is also covered below.
Building the Hermes Lite 2: Step by Step
The full build takes somewhere between thirty minutes and an hour depending on how careful you are and whether you have done any kit building before. Here is how the process goes from start to finish.
Step 1: Install the Filter Board
The filter board slides into the slot next to the main radio board inside the case. The fit is snug but not forced. Once it is seated, connect the two boards using the included connector. Press it down firmly onto the pins. You will feel it seat. If it is not fully down it can cause problems later, so take a second to make sure the connection is solid before moving on.
Step 2: Handle the Heat Sink Shim
The heat sink shim is a thin piece of metal that sits between the power amplifier on the board and the aluminum case. The case itself acts as the heat sink, so getting good thermal contact between the PA and the case matters. The shim goes on the underside of the board, not on top. There is a pre-drilled hole in the case for the screw that locks it in place, so you do not need to drill anything.
Before you slide everything in for the last time, add a thin layer of thermal paste to both sides of the shim, including the side that contacts the case. This step is easy to skip on the first pass and regret later. The HL2 is not a high-power radio, but running the PA without good thermal contact is still asking for long-term trouble. Do it right the first time.
Step 3: Assemble the Case
The end plates are thin but machined nicely. They attach with small hardware included in the kit. Nothing here requires force or unusual technique. Fit the plates, snug down the screws, and the case is done. The finished unit is compact and reasonably solid feeling for what it is.
Step 4: Connect Power, Ethernet, and Antenna
The HL2 needs three things to operate: DC power, an Ethernet connection to your computer or network, and an antenna. It does not power over Ethernet, so plan for a dedicated power supply. A standard 13.8V ham radio supply works. Plug in the Ethernet, connect an antenna to the SO-239, apply power, and the board should come to life. At that point the hardware side is done and the software side begins.
Setting Up Thetis
Thetis is the SDR software I chose for the HL2, and I want to be upfront that the first time you open it, it can look like a lot. There are panels for audio routing, discovery settings, DSP configuration, transmit parameters, and more. If you have used something like SDR# or HDSDR before, Thetis is a step up in complexity. But complexity is not the same as difficulty once you know what you are looking at.
The single most useful thing I can tell you about Thetis setup is this: read the Thetis Setup guide on the Hermes Lite 2 GitHub wiki before you click anything. The guide walks through each section in order. It covers the discovery process for finding the HL2 on your network, how to configure your audio devices, and the basic settings you need to start receiving. Following that guide in order will get you from a fresh install to copying signals in under an hour.
A few things from the setup process worth noting on their own:
Audio routing is where people most often get stuck. Thetis uses virtual audio cables or your physical sound card to pipe the demodulated audio to your speakers or headphones. If you have never done this before, the concept of virtual audio devices can be confusing. The guide explains it, but expect to spend a few extra minutes here if this is new territory for you.
The discovery process for finding the HL2 on your network is straightforward on most setups. Thetis has a built-in discovery button that scans for compatible hardware. As long as the HL2 and your PC are on the same network segment and your firewall is not blocking things, it usually just works.
Transmit configuration requires a bit more care. You need to set your output power level and make sure the CAT control settings match your operating intentions. Do not skip this step even if you just want to listen at first, because having misconfigured transmit settings when you do go to transmit is not a great situation.
Thetis Features Worth Knowing About
Once Thetis is running and you are receiving signals, the feature set starts to show its value. This is not a stripped-down receiver display. There is real DSP here, and a lot of it works well enough to change how you interact with marginal signals.
Noise Reduction
Thetis includes four different noise reduction modes. They are not all equal. Some work better on certain types of noise and some are more aggressive than others. The better ones can pull a voice signal out of a noise floor in a way that genuinely impresses. It takes some experimenting to find which mode works best for a given situation, but having multiple options is better than having one and hoping for the best.
Spectrum Noise Blanker
The spectrum noise blanker handles impulsive noise like power line interference and other repetitive noise sources. On its own it is useful. In combination with one of the noise reduction modes it can pull a workable signal out of conditions that would otherwise be impossible. That combination is where it starts to feel like a serious tool rather than a checkbox feature.
Adjustable Bandwidth
The receive filter bandwidth is fully adjustable by dragging the filter edges on the waterfall display. You can narrow it down to cut interference from adjacent signals or open it up when conditions are clean and you want more audio fidelity. On SSB this is the kind of control that traditional radios require a separate DSP accessory to match.
SSB Squelch
SSB squelch is something a lot of people do not even think about until they have a radio that offers it. Watching a band without having to listen to constant noise between signals is a quality of life improvement. The Thetis squelch works well enough that I keep it active most of the time.
Click to Tune
With click to tune enabled, you can click directly on a signal in the waterfall to jump to it. This sounds like a small thing until you are scanning a busy band and want to check signals quickly without typing in frequencies. It is one of those SDR features that is hard to give up once you have used it.
Who Should Consider the Hermes Lite 2
The HL2 is not for everyone, and being clear about that is more useful than a blanket recommendation. If you want a radio that is polished out of the box, has slick manufacturer support, and feels like a finished consumer product, the Hermes Lite 2 is probably not your radio. The setup requires some patience, and there will be moments where you are reading a GitHub wiki to figure out why something is not working the way you expect.
But if you are a software person, or someone who runs Linux, or someone who wants to actually understand what their radio is doing rather than just using it, the HL2 is compelling. The combination of open hardware and open software means you are not locked into anything. If Thetis does not do something you need, you can look at the code. If you want to build automation around the radio, the protocol is documented and the community has already built a lot of tooling around it.
For operators who are running WSPR experiments, digital modes, or any kind of computer-integrated operating, the Ethernet interface is also genuinely convenient. There is no USB serial adapter to manage, no driver issues on Windows updates, no cable that only works in the right USB port. It shows up on your network like any other device.
What the HL2 Is Not
The output power of the Hermes Lite 2 is low by traditional HF transceiver standards. The stock board produces around one watt, though there are power amplifier add-ons available that can push it higher. If you need a hundred-watt station for contesting or serious DX, you would need to add an external amplifier. That is an additional cost and an additional piece of equipment to manage.
The HL2 also covers HF. It is not a VHF or UHF radio. If you need a single radio that covers everything from 160 meters up through two meters, this is not it. It does HF well and that is where the focus is.
On the software side, Thetis runs on Windows. If you are a Linux user, there are alternative front ends that work with the HL2 protocol, but Thetis specifically requires Windows. That is worth knowing before you commit to the setup.
None of these are dealbreakers depending on what you need the radio to do. But they are worth being honest about rather than burying in the fine print.
First Impressions on the Air
Getting on the air with the HL2 for the first time, the immediate impression is that the receiver is genuinely capable. The waterfall display in Thetis gives you a clear picture of what is happening across the band, the signals are clean, and the noise floor is reasonable. This does not feel like budget hardware trying to punch above its weight. It feels like a radio that was designed by people who actually use HF and knew what they were building.
The DSP tools are where it gets interesting. Running the spectrum noise blanker alongside one of the noise reduction modes on a noisy evening band is a different experience than just listening to the raw signal. It is not perfect, and it will not rescue a completely buried signal, but it makes marginal conditions noticeably more workable. That kind of capability for four hundred dollars is not something you could get a few years ago.
The click to tune feature is immediately addictive if you are used to SDR operating. You end up scanning the band differently when you can just click on signals instead of tuning past them. It changes how you explore a busy frequency range and makes it much easier to quickly check a signal before deciding whether to stay on it.
For the kind of work I do, including WSPR testing, antenna comparisons, and general HF monitoring, the HL2 fits well. The open-source foundation means I can build on top of it rather than around it, and that is exactly what I was looking for when I sold the SunSDR and started fresh.
Frequently Asked Questions
What is the Hermes Lite 2?
The Hermes Lite 2 is an open-source HF SDR transceiver that connects to your computer via Ethernet. It is designed for amateur radio use and is available from vendors like Makerfabs for roughly $200 to $250 for the board. A complete station including power supply and case can be put together for around $400.
What software works with the Hermes Lite 2?
Thetis is the most actively developed option and the one I am using. It is open source and has a solid feature set including noise reduction, noise blanking, adjustable bandwidth, and click-to-tune. There are other front ends available for Linux users, but Thetis is the best-documented choice for most HL2 setups.
Do I need to solder anything to build the Hermes Lite 2?
No. The main board arrives pre-assembled. The build involves seating the filter board, connecting the two boards with the included connector, fitting the heat sink shim with thermal paste, and assembling the case. No soldering is required for the standard build.
How does it compare to a Flex Radio?
The Flex offers a more polished, all-in-one experience and more integrated manufacturer support. The HL2 is fully open source, costs a fraction of the price, and gives you access to both the hardware design and the software internals. For operators who want to tinker, extend, or automate, the HL2 offers something the Flex cannot match at any price point.
Is Thetis hard to set up?
The initial setup can look overwhelming, but the Thetis Setup guide on GitHub walks through the whole process in order. Most people can get from a fresh install to receiving signals in under an hour by following that guide.
What power output does the Hermes Lite 2 have?
The stock board produces around one watt of RF output. External power amplifier options exist for operators who need more output, but the base radio is a low-power device. For digital modes, WSPR, and weak-signal work it is adequate. For high-power operating you would need to add an amplifier.
Conclusion: Is the Hermes Lite 2 Worth It
The short version is yes, with the appropriate caveats. If you want a plug-and-play radio that works like a traditional HF transceiver and does not require any setup beyond turning a knob, the HL2 is not that. There is a real learning curve on the software side, and the build requires some patience and attention to detail even without soldering.
But if you are the kind of operator who enjoys that part, who likes to understand the tools and build things on top of them rather than just using them, the Hermes Lite 2 is a genuinely capable radio at a price that is hard to argue with. The combination of open hardware, open software, Ethernet connectivity, and real DSP performance puts it in a category by itself at this price point.
The Flex Radio is a better product in a lot of ways. It should be, for the price. But for four hundred dollars and full access to the source code of everything from the firmware up, the HL2 offers something different. Not a compromise on a budget, but a real option with its own legitimate advantages.
For the software-minded ham who wants to do more than just operate and has some interest in what is happening under the hood, the Hermes Lite 2 is worth a serious look. It is sitting on my desk right now and I have no plans to go back to anything else.