Hermes-Lite 2






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. 



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Implementation Notes

  • 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 will happen in the future.
  • The Pure Signal concept is not currently supported.


Radio Pane

When a HL2 is started the radio pane is shown in the Receive DSP panel.


Options - opens the configuration window with more TX Options (below).

LNA - LNA gain in 1 dB increments from -12dB to +48dB. As the LNA value is increased the IQ (data)  gain is decreased so signal levels stay roughly stable, only the noise floor changes. This approach reduces the need to adjust the contrast as the LNA gain changes.

Visual - a purely numeric gain applied to the IQ (data) samples after they are received from HL2 and before they are processed any further.

Status - temperatue in degrees Celcius, Gateware version and ADC Overload warning (increase the LNA gain to see the ADC being overloaded).




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.



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).
  • Fiulter board - select the filter 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.

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

If required these settings will be made user-configurable.


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.






Information about the console's transmit support is available here [link].



Build 9 Images

Below are images of the build 9 boards published on the Hermes Lite mailing list by Steve KF7O.

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 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.