SDR Ham Radio Transceiver 
Hermes Lite 2 (HL2)
for "pure" SSB operation

I learned of a new SDR ham radio transceiver - the Hermes Lite 2 - while listening to a QSO on 40 meters, sometime in early 2023.

I found that it had two very appealing characteristics:

  • Low cost! Last I looked (Sept 26, 2023) it was $340 US plus shipping from reputable The price includes main PCB, N2ADR low-pass filters PCB and enclosure.

  • PureSignal (PS) technology previously only available on xcvrs worth thousands (for example the ANAN radios by Apache Labs)!

These two features alone were enough to get my attention but, as I listened to QSOs in which hams were using Pure Signal, I was hooked! Using a spectrum analyzer, I envied the "brick wall" (no splatter outside the audio band) and "full-bodied" appearance of their SSB signals.

Further listening convinced me that PureSignal produced a much cleaner and "punchy" SSB signal than any audio compression I had ever heard.

SDR ham radio transceiver - Hermes Lite 2 - sitting on top of its peripheral equipment.SDR ham radio transceiver - Hermes Lite 2 - sitting on top of its peripheral equipment.

HL2's PureSignal Technology

Here is a quote from the HL2 wiki page:

"Basically pure signal also known as adaptive predistortion is a method of sampling a transmitted signal and applying a polynomial to produce a driving signal which is distorted by the algorithm so that it corrects the non linearities in the output... the result can be 10 dB or more improvement on higher order products which means less splatter, better speech quality and higher efficiency."


If you want to learn more about PureSignal technology, I invite you to visit :

Acquiring the Hermes Lite 2
Sdr Ham Radio Transceiver

The following are only available from

  • main HL2 PCB fully populated (no soldering)
  • N2ADR low-pass filters PCB (plugs onto main HL2 PCB)
  • enclosure for HL2 + N2ADR

Assembling the PCBs into the enclosure is easy. Here is an excellent YouTube demo video that will show you how to do that:

PowerSDR software for Windows PC is the de facto standard for:

- Openhpsdr protocol 1
- PureSignal support.

By the way, the video mentions that an ethernet cable is connected between the HL2 and an Internet router. Now, I do not have a router in the shack. It's in the next room. My PC is on WiFi. I could have routed an ethernet cable across to the next room but I chose to test the lazy man's solution first. I plugged the ethernet cable from the HL2 directly into a free ethernet port on my PC. It worked! The PowerSDR software on the PC found the HL2 instantly.

Disregard the use of SDR Console software in the video because it does not support (cannot activate) the PureSignal feature of the HL2.

I recommend using PowerSDR on the PC to drive the HL2.

I insist on the use of Hermes Lite 2's PureSignal feature because that's what makes it stand out from the two other very good QRP SDR ham radio transceivers that I own, namely an Elecraft KX2 and an ICOM IC-705.

Hermes Lite 2 (HL2) Setup

I recommend PowerSDR software for the Hermes Lite 2. You can download the OpenHPSDR-PowerSDR mRX PS v3.4.9 MSI installer here.

SDR ham radio transceiver PowerSDR display of the Hermes Lite 2.SDR ham radio transceiver PowerSDR display of the Hermes Lite 2

Here is an excellent tutorial on how to set up PowerSDR for the Hermes Lite 2:

In hindsight, I am certain I would not have configured everything correctly without this video tutorial!

There are other software possibilities to run with the HL2 but I have found that PowerSDR best met my needs which boil down to one thing: being able to use the PureSignal technology available on the HL2!

A short comment on other available software for the Hermes Lite 2 SDR ham radio transceiver. The following do not support PureSignal technology available in the Hermes Lite 2 :
SDR Console

LinHPSDR and PiHPSDR include PureSignal support but only run on Linux O/S.

More software, with support for PureSignal technology, may have become available by the time you read this.

PC Microphone

Again, I used the lazy man's solution first. Instead of investigating all kinds of microphones suitable for SSB radio communications with PC software, I decided to try a Logitech model H110 stereo headset with USB connector that I had once used for another purpose.

Now, of course, the audio response from such a microphone is much too broad for the usual 3 kHz wide SSB signal. After a little investigation, I found that in Windows, I could limit the audio output of the Logitech microphone to below 8 kHz which concentrates the audio spectrum that contains most of the useful human voice energy.

On the air reports confirmed that this simple and economical headset microphone was indeed performing well.


When you feel that 4-5 watts output won't quite cut it, you can always add a linear power amplifier to the output of the HL2.

One word of caution here:

You need to install a relay buffer interface between the HL2 keying relay (EXTR) and the amplifier, to protect the HL2 from the transients that the relays in the amplifier generate when keyed. I use a RBI-1A by for that purpose. It comes with the appropriate prewired cables.


NOTE: MakerFabs has since issued a new IO board (product code HerLitIOB) for the purpose of interfacing with outboard equipment such as a power amplifier. It requires some soldering and writing or downloading firmware, depending on the type of outboard equipment you need to drive with the HL2.

In my honest opinion, the RBI-1A is a much more straightforward solution!

I use a Xiegu XPA125B "100 watt" amplifier with my HL2 SDR ham radio transceiver. I have put the claimed maximum power output between quotes because, according to an ARRL review of this amplifier by VA2PV, it is best to drive it with much less than 5 watts because it starts to generate a prohibitive amount of harmonics above 70-80 watts output.

Therefore, I only drive it with just enough power from the HL2 to reach about 70-80 watts maximum output from the XPA125B which means about 1-2 watts from the HL2, depending on the band.

I monitor the output with a Daiwa CN-901 SWR/PWR meter because the power value displayed by the XPA125B is not too reliable.

Finally, the XPA125B comes with an internal tuner but I prefer to use a wide range external tuner - in this case a MAT TUNER mAT-125E - with my odd length homemade end-fed antenna.

In Short

The Hermer Lite 2 is a very economical SDR ham radio transceiver for the shack capable of outputting very clean and "punchy" QRP SSB using PureSignal technology. The only drawback (for some) is that the PowerSDR/HL2 combination cannot send CW. Sorry.

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73 de VE2DPE
Claude Jollet
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