Hermes Lite 2

The Hermes-Lite 2 is a 160-10 meter, multi-mode, QRP, software defined HF transceiver. Physically it’s a small (6” x 4 1/8” x 1 5/8”) black box with an Ethernet socket and a few blinking lights. It’s not a standalone transceiver, requiring a host computer running SDR software to function. Since it is open source you can build it on your own or you can you can get an HL2 by participating in a group buy from Makerfabs. The HL2 is $226, the low pass filter board is $53 and the case is $17. All components are mounted. You have to drill a hole in the case for the heat sink and assemble the system.

The HL2 is a well refined product having about two decades of development behind it. Development started by a group of hams in 2005 and in 2008 the open source openHPSDR project gained support from The Tucson Amateur Packet Radio group (TAPR). Both hardware and software were developed together. The initial hardware was a set of boards which plugged into a backplane, like the old S100 bus computers. By 2012 Apache Labs was selling hardware for the first versions. Over time as the software was refined the hardware shrunk to a single board Hermes, then the Hermes Lite and finally the Hermes Lite 2.

You can find info at http://hermeslite.com/ and support in the google group https://groups.google.com/g/hermes-lite. Other spin offs from the openHPSDR development include the Apache labs ANAN line of transceivers.

The main HL2 hardware and firmware development is carried out by Steve Haynal, KF7O. The add on low pass filter board was developed by James Ahlstrom, N2ADR, who also developed and supports Quisk SDR software.

The HL2 is a direct down/up conversion SDR. It communicates with a host computer over ethernet, which provides high speed communication and allows the HL2 to be remotely operated. Audio in and out is produced by the sound card and software running on the host computer attached to the HL2. The software also controls the HL2 and provides display usually including a spectrum and perhaps a waterfall. You can use virtual audio cables to communicate to other software like WSJT-X and fldigi and virtual serial ports for rig control like N1MM+ and Log4OM.

One reason it is inexpensive is that the DSP heavy lifting is done by a Cyclone 4 FPGA, This is a relatively low cost device as it is commonly used in cable modems and churned out by the millions. An AD9866 12 bit ADC is used that runs at 76.8 MHz and DAC that runs at 153.6 MHz and supports up to a 384 kHz swath of bandwidth in receive. Its main board is usually paired with a relay switched low pass filter board to produce clean transmissions.

Like the Flex transceivers, the HL2 supports multiple receiver “slices”. The current FPGA gateware supports up to four receiver slices. The wide receive bandwidth and multiple slices drives the need for a fast Ethernet connection. The HL2 operates in full duplex mode so that you can monitor your transmission through a built in sampling circuit. This opens the way to use predistortion software like PureSignal, also used in Flex and Apache transceivers, to actively predistort your signal to correct for PA distortions and generate excellent quality transmissions.

Multiple software applications support the HL2 including Quisk, SparkSDR, SDR Console, PowerSDR, Thetis, LinHPSDR and PiHPSDR. There are Windows, Linux and Raspberry Pi apps. They generally all support spectrum and waterfall displays, a wide range of filters, AGC, ALC and audio input monitoring. PowerSDR and Thetis both have HL2 specific versions. SDR Console is a beautiful, easy to use application by Simon Brown, the original developer of Ham Radio Deluxe, that supports the HL2 well.

The HL2 has provisions for IO add ons for controlling a fan, AH-4 tuners from Icom and LDG, external power amplifiers and general IO for experimenting General Purpose IO. A popular addition to the system is the Hard Rock 50 amplifier. Another addition is a set of band pass filters for the receiver.

In contrast to the excellent support for SSB transmission, the CW support of the HL2 is minimal. There is a jack on the HL2 for a straight key, but no built in keyer and side tone. Generating a side tone turns out to be more difficult than it might first appear because of latency. The time it takes for the key press to be processed by the HL2, travel trough the Ethernet cable, be processed by the host computer software and activate the sound card is long enough to throw off all but the slowest CW sending. SDR Console does a better job of reducing latency than most, but still has no keyer or CW keyboard.

The solution for me was to install a HL2 companion board that adds a keyer, mic, headphone jack, amp interface, speaker, Icom AH4 ATU interface and power switch. This was developed by Robert Entwhistle WA2T and Takashi JL1UDD. There is no noticeable latency with this approach. There is a smaller range of software available for the HL2 with companion but that fortunately includes Thetis and piHPSDR. Thetis grew out of PowerSDR from the original project and is also used by Apache Labs’ Anan SDR transceivers.

Thetis software is extremely feature rich with good equalizers, a plethora of audio processing options and Pure Signal support. In addition to the usual noise reduction, noise blanker and notch filters there is an AI powered noise reduction function that does a really good job.

Thetis also has some wonderful features for CW, including an APF and "spot " tuning. The Audio Peaking Filter has a narrow peak but not sharp skirts. Signals within the peak are amplified, as opposed to outside attenuated with sharp skirts like a usual filter. It makes the CW pop out with little ringing and other artifacts you'd get with a narrow passband. The "spot" automagically tunes to center the signal in the passband - very handy with APF. There is also keyboard sending with macros.

In addition to the usual SDR panadapter point and click tuning Thetis has the easiest to use tuning I have found. You change the tuning step implicitly by hovering your mouse pointer over a digit in the VFO window and scrolling. The digit you are over will change. You move effortlessly from Mhz to Hz step sizes.

Thetis makes it easy to use virtual com ports and audio cables. It also supports communication by TCP/IP, MIDI and the new TCI protocol.

The Thetis visual interface is highly customizeable, from clean and simple to information packed. Want a "magic eye" tuning aid or classic cross needle meters? You can have it. My favorite is a small window that just shows the spectrum that is filter passband wide. You can see instantly how well you are tuned without having to zoom in the panadapter display. My panadapter background image is a world map with day/night show, shades of Geochron! You can also have spots listed on the panadapter at their frequencies.

For Linux fans you can also run LinHPSDR and piHPSDR on a Raspberry Pi. I loaded piHPSDR on my Pi 5 and I found it similar to Thetis, as you would expect from their common root. The Pi had plenty of processing power to run smoothly.

IMHO the Hermes Lite 2 is an excellent value for a highly capable, full featured HF transceiver. The many years of refinement of the hardware and software by hams for hams has led to a great rig. When I need more power I couple mine to a HARDROCK 50 amp, yet another ham produced piece of solid gear, which is seamlessly controlled by the HL2. The HL2 is my favorite desktop rig