Hermes-Lite 2

Introduction

The Hermes-Lite is an outstanding low-cost direct down/up conversion software defined amateur radio HF transceiver based on a broadband modem chip and the Hermes SDR project.  It is highly recommended.

Links

Purchasing

There are various options:

Implementation Notes

 

  • Connect your antenna to the ANT TX/RX port, RF1 is low power TX only.
  • Use a good, stable 12 volt power supply.
  • Use a CAT 6 or CAT 7 ethernet cable, these have better shielding.
  • Do NOT use Wi-Fi - this increases UDP packet loss.
  • The LEDs show the status of the HL2 [ link ].
  • The full spectrum bandscope view, 0-38.4MHz is not yet supported.
  • Although HL2 supports up to four simultaneous band 'slices' only one is currently supported in SDRConsole. Support for four map happen in the future.
  • The Pure Signal concept is not currently supported.

 


Gateware Versions

The code which runs inside the HL2 is referred to as Gateware. Here's the status as of 2020-06-01:


  • ✓ 70 and 71p1 work well
  • ✗ 71p2 does not work when sending CW from a keyer connected directly to the HL2..
  • ✓ 71p3 works well, CW problem in 71p2 is fixed.


Download folders:



August 7th, 2023 - currently testing a 'Load Gateware' option in SDR Console.


For each link above you need the rbf file, use SparkSDR to load gateware. In SparkSDR right-click on the Hermes-Lite 2 entry, if you have other Hermes / Hermes variants on the network then you see an entry for each radio, so be careful and select the correct entry!


  • Close SDR Console.
  • Start SparkSDR.
  • Right-click on the entry for the Hermes-Lite2 (below).
  • Select the new RBF file to be loaded.
  • Click Program ., loading new gateware only takes about five seconds.
  • Close SparkSDR,
  • Start SDR Console.
  • When you start the HL2 the new gateware will be loaded and ready for use. The gateware version is shown at the bottom of the Radio panel (below).


Options

The options are shown in the Receive DSP panel.
  • RX Gain - there is only one adjustable gain stage in the HL2, the low noise amplifier. 
  • CW Hang - increase this value to reduce 'relay chatter' - relays switching between dots and dashes.
  • OP Power - the output power from the AD9866 which is the heart of the HL2. There are 16 levels of output. See also the Drive option in the transmit DSP.
Status
  • Temperature is important - keep your electronics cool! Cooler is always better.
  • The gateware major.minor version is show together with the number of receiver slices supported.
  • The TX FIFO shows how status of the internal transmit buffers, ideally this is in the middle of the progress bar.

Transmit

Meters

When the HL2 is started the Meter window in the Transmit DSP panel is shown as below.
  • Power and IPA calibration will be supported in a future release of SDC Console.
  • ALC is measured in the modulation components of SDR Console, it is not a traditional hardware-feedback ALC.

Options

The transmit options are shown below.
  • Enable onboard power amplifier - much be selected if the 5 watt PA is to be used.
  • Disable external PTT in low power mode - this is the Q5 switch control - see schematic.
  • Mute RX - in transmit you do not want to receive the same data, so the IQ (data) samples are muted while in transmit and for a few milliseconds after transmit ends (Post).
  • Filter board - select the filter option.
CW Sidetone
To generate sidetone as CW is sent you must enable the CW Sidetone option below, then select the settings as desired. When you start sending extra padding is added before the the sidetone, this ensures there are no crackles in the output which are the result of sample underflow in the output device. Normally only a few milliseconds may be required. As you increase the padding the sidetone latency increases, so use as little padding as necessary.

Don't forget - an external USB soundcard will add more latency, as will using speakers rather than headphone. The speed of sound is 343 m/s, so if your speakers are 2 metres away then that's a latency of almost 7 ms!

So for minimum latency use headphones connected to a soundcard on your computer.

Output Pins

The output pin selection is fully configurable for each band. The default setting is for the N2ADR PA board as it is the most common option.

N2ADR Filter Board

When setting the low-pass filter (LPF) the higher of the transmit and receive frequencies is used. When setting the high-pass filter the lower of the transmit and receive frequencies is used.

If required these settings will be made user-configurable.
Filter OC Mask Frequency
LPF x01 <= 2 MHz
x02 <= 4 MHz
x04 <= 7.3 MHz
x08 <= 14.35 MHz
x10 <= 21.45 MHz
x20 <= 30 MHz
HPF x40 >= 3 MHz

Two-Tone test

The output from the HL2 transmitter is very clean as the two-tone image below shows. The signal was received with an ANAN 10e SDR, the two tones are 700 Hz and 1900 Hz.

Optional RX Input

Note from Steve, November 4th 2019: There is no switching or software control of the optional RX input. If you look at the HL2 schematic on the "RF Frontend" page, you can see that it is just a parallel input from the TR switch. 


The main purpose is for more controlled feedback of TX signal to the RX during TX for Pure Signal. You could also use it as an always connected RX input to a different antenna. You can solder coax directly to RF3 on the HL2 and then run the connector to the back panel. There are also a uFL footprint RF4 and RF5 for a removable connection. See https://www.adafruit.com/product/1661. These provides direct connection to the ADC pre and post LPF. You can run a cable to one of these and remove B81 to disconnect the RX from the TR switch. You either have to disconnect the RX from the TR switch, keep the TR switch always in TX, or remove the TR switch if you want full duplex with the optional RX inputs.