I’ve not been on the radio much over the last few weeks as I’ve had my head down other radio related rabbit holes.
One of the rabbit holes is a Node-Red project to make my online logs a little more interactive. For sometime now my logs have been displayed on my website as nicely formatted, searchable HTML pages however, they don’t really allow the viewer (myself included) to see the global coverage of all the contacts so, I decided to write a Node-Red flow that would do just that.
M0AWS Interactive Log Flow
The flow itself isn’t too complicated and basically consists of reading in the individual ADIF formatted log files, processing the data and then sending the data in the correct format to the map node for display.
I’ve had to write a few functions to handle the processing of the ADIF formatted data but, these aren’t particularly complex and are fairly easy to understand even if like me, you’re not a Javascript programmer.
The flow is working perfectly however, I’m in the process of reworking the format generic payload function to reduce the amount of code and make it more efficient.
M0AWS SSB / CW / FreeDV Interactive Log World Map
M0AWS Interactive Log Map Layers Menu
The flow generates two maps, one for voice / CW /Satellite contacts and the other for WSJT-X FT4/8 contacts. Every pin on the map is colour coded by band with satellite contacts being denoted by a satellite icon.
Each pin / icon on the map is clickable and reveals the data of the QSO being displayed.
In the top right-hand corner of the map there is a drop down layermenu that allows the viewer to filter by band thus reducing the number of icons on the screen at any one time.
Seeing the data presented on a map really brings my logs alive. An example of this is that I had no idea I’d worked so many stations in India on the QO-100 Satellite.
The small icons in the pins show a microphone for SSB/FM/FreeDV contacts and a downwards pointing triangle in a box for CW contacts. Sadly I couldn’t find a Morse key icon in the collection available.
M0AWS filtered view of QO-100 Satellite contacts
I only use FT4/8 for testing new antenna designs however, it’s interesting to see the global coverage accomplished with this weak signal mode.
M0AWS WSJT-X FT4/8 Interactive Log World Map
Once I’ve finished rewriting the format generic payload function I will make the flow available for download here so that others can also create an interactive view of their radio logs.
If you want to have a look at the maps and try them out for yourself, they are available under the Logs menu above.
This Node-Red instance is running in a virtual machine (VM) on a 16GB RAM RaspberryPi 5 that is also running a number of other VMs at the same time so, it’s safe to say it’s not heavy on CPU and will run on the older Pi4 as well.
I’ve recently been trying out the FreeDV RADEv1 digital voice mode on the HF bands with great success. The audio quality is astounding when compared to the normal analog SSB mode. Using only 20w I’ve been surprised how successful I’ve been talking to stations in the UK and Europe as can be seen in my FreeDV Log.
FreeDV has been around for quite a few years with development being funded by an ARDC grant and financial sponsorship from the Software Freedom Conservancy.
“FreeDV is a suite of digital voice modes for HF radio. Our flagship mode is the Radio Autoencoder (RADE). You can run RADE using a free GUI application for Windows, Linux and macOS that allows any SSB radio to be used for high quality digital voice.“
And the most important part:
“All software is open source, released under the (a) GNU Lesser Public License version 2.1 (GUI and legacy FreeDV modes) and two-clause BSD license (RADE).“
FreeDV running under KDE-Plasma on Kubuntu PC
Looking at the digital voice (DV) community in the HAM Radio world, it’s stuffed full with proprietary DV modes from small software houses and black box transceiver manufacturers with no real OpenSource alternatives, until now.
Installing FreeDV is pretty simple regardless of which operating system (O/S) you use. Being a Linux user I grabbed the AppImage from the website and set about reading up on how it works and how it is configured.
I decided to take the two sound card approach since I have 2 USB sound cards connected to my shack Kubuntu Linux PC.
Configuring the audio routing isn’t straight forward as both the receive and transmit audio to/from the radio needs to be routed via the FreeDV app. To make this even more complicated I am using my Hermes Lite 2 SDR transceiver and PiHPSDR software, a complete OpenSource/OpenHardware Amateur Radio Station.
M0AWS FreeDV and PiHPSDR Audio Routing Diagram
Trying to clearly describe the audio routing using words alone would be impossible and very confusing so, I put together the diagram above.
Using two USB sound cards I’ve configured the system such that USB Sound Card 1 (an old Griffin iMic USB sound device) handles just the audio from/to the headphones and microphone. All the audio at this point in the system is analogue.
The second USB sound card, a cheap Plug and Play (PNP) USB audio device from Amazon, handles all the digitised signals from/to FreeDV and PiHPSDR.
Taking this 2 sound card approach keeps confusion to a minimum and separates the analogue and digital components of the audio routing.
So, how does this translate to the FreeDV and PiHPSDR audio settings?
Transmit Audio Chain
FreeDV Transmit Audio Settings
Starting at the beginning of the transmit audio chain, let’s look at the transmit audio settings in FreeDV.
Looking at the FreeDV Transmit audio settings screenshot below we can see that the Input From Microphone to Computer device is set to:
This is the digitised audio output from FreeDV (via USB Sound Card 2) to PiHPSDR and is used as the transmit audio that is sent to the Hermes Lite 2 transceiver.
FreeDV Transmit Audio Settings
PiHPSDR Transmit Audio Setting
To complete the transmit audio path we next need to look at the PiHPSDR transmit audio setting.
PiHPSDR Transmit Audio Settings
As can be seen in the screenshot above, the Local Microphone device in PiHPSDR is set to the Monitor of USB PnP Audio Device Analogue Stereo.
This effectively routes the digitised output audio from FreeDV (Output From Computer to Radio device) to the Input audio of PiHPSDR.
The reason for using the Monitor audio feed is because FreeDV does not recognise the Mic Input in PiHPSDR as a valid output device for FreeDV to use, hence we just need to monitor the FreeDV output device and use it as our input audio device in PiHPSDR.
This completes the transmit audio chain.
Receive Audio Chain
PiHPSDR Receive Audio Setting
Starting at the beginning of the receive audio chain we first look at the PiHPSDR receive audio setting.
PiHPSDR Receive Audio Setting
In the screenshot above we can see that the receive audio output from PiHPSDR is set to USB PnP Audio Device Analogue Stereo (USB Sound Card2). This is the DX station’s digitised audio as received by the Hermes Lite 2.
FreeDV Receive Audio Settings
Next let’s look at the receive audio setting in FreeDV.
FreeDV Receive Audio Settings
The Input To Computer from Radio device is set to the monitor of the USB PnP Audio Output Device:
This is the analogue audio output on the iMic USB Sound card (Sound Card 1) that routes the analogue audio to the headphones and completes the receive audio chain.
Summary
The audio routing required by FreeDV can appear very daunting when first attempting to configure it on the Linux platform but, hopefully the diagram and screenshots above will help in understanding the complete end-to-end audio chain that is required to make this mode work.
PiHPSDR can of course be replaced by your black box radio CODEC entries that will appear in the device lists shown above if you have your radio connected via USB. The config is basically the same but, just uses a different device instead of USB sound card 2 shown in the diagram above.
I hope this article is useful to those wanting to try FreeDV on the Linux platform and I look forward to hearing you on RADEv1.
More soon …
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