digital modes

I have always enjoyed digital modes from home, like many I live in a noisy urban environment. Digital modes offer me a way to make low power QSO into the noise and still get results.

Using the Hermes Lite SDR and JS8 has provided great fun, I tend to stick to 7 MHz as my antenna works well on this band. I have a doublet antenna 10m per leg fed with 300 Ohm into the shack. If you’re looking for a 100w amplifier, this can help under poor conditions.

The first thing to realise about JS8 call is it a chat-based digital mode, you can send free text and its based on the FT8 protocoled. They are not compatible, so you cant use JS8 in the FT8 program, nor would you use the same frequencies.

The first step is to download JS8 and have a look at the readme file, it’s easy to set up like many digital modes it has a familiar interface. Add you QRA locator and call sign, some details on your QTH and your away.

JS8 is designed to be left on, so if you have a low powered computer or Raspberry PI this could provide a useful option. I use a fanless mini I7, as this powers the SDR and allows me to use 4 slice receivers as needed. You don’t need that computing power if you just want to run JS8 and a low power transceiver. I have recently worked a number of people using the new Icom 705, and this type of radio is ideal to be left on 24×7.

You have the option to send heart beat messages, and stations will reply automatically with your signal report.

Suggested Freq – can be auto selected from JS8

Store and relay messages via other call signs who can receive you, so let’s say you want to get a messaged to VK1ABC but he can’t read you. You can look on the screen and see that K1ABC can read you, and they also read VK1ABC so you have the option to send the message via a relay.

You can configure your station to automatically respond to requests to report stations signal, others heart beat messages and store messages in other mail boxes.

Its really good fun, so why not have a play?

The Hermes-Lite is a 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 entirely open source and open hardware, including the tools used for design and fabrication files.

The SDR is controlled over your LAN, and plugs into your router. This can provide both local and remote operation. You can read more online about the project on the Hermes website.

The board comes fully installed, although you do need to follow the instructions on thermal dissipation for the PA. The radio will deliver 5w and is suitable for all modes and works particularly well on digital modes.

The microphone can be plugged into your PC, and then defined as the soundcard on the radio. In this audio clip, you can hear Gerald G4AXP (40w), and M0TAZ (5w) both using Hermes Lite SDR to have a chat on 5 MHz. In this case, I was using a cheap USB headset as I find headphones often help with noisy HF bands.

M0TAZ 5w and G4AXP 40w both using Hermes Lite SDR radios

The example RX filter setup in Spark SDR shown here.

The radio needs to be controlled by software locally installed on your PC, and you have a wide choice. I started with SparkSDR, as this program has a number of really neat features. The ability to have 4+ receivers running decoding digital modes on the fly. You will find SparkSDR have a online forum for questions and support.

Here we will look at the setting to use Spark SDR with WSJT-X, setting up the sound card option, and radio mode set to DIGIU and hamlib.

You can use VAC to feed another digital program

In WSJT-x you need to set the rig to Hamlib NET rigctl and Network Server to your local IP address of the PC using port 51111

Network Server to PC IP address port 51111

Here we see WSJTx configured with SparkSDR and Hermes receiver decoding FT8

Its possible to do FT8 and other digital modes directly in SparkSDR, you dont even need to VAC but its good to have control as we can use this with other programs.

SparkSDR can be integrated with FLdigi using Hamlib

I have been running the Hermes Lite now for a few days. 140 QSO most FT8 or FT4 between 3 to 5w. This reception report is amazing, not worked but nice to know you have potential. ZL4AS

Tag: digital modes

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