SDR – M0AWS Amateur Radio

14 December 202515 December 2025

FreeDV audio routing with PiHPSDR and Hermes Lite 2

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.

So what is FreeDV?

To quote the FreeDV website:

“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:

alsa_input.usb-Griffin_Technology_Inc_iMic_USB_audio_system-00.analog-stereo

This is the microphone connection on the iMic USB device (USB Sound Card 1) and is the analogue transmit audio input to FreeDV.

The Output From Computer to Radio device is set to:

alsa_output.usb-0c76_USB_PnP_Audio_Device-00.analog-stereo

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.

PiHPSDR Transmit Audio Setting

To complete the transmit audio path we next need to look at the PiHPSDR transmit audio setting.

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.

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.

The Input To Computer from Radio device is set to the monitor of the
USB PnP Audio Output Device:

alsa_output_usb_0c76_USB_PnP_Audio_Device-00.analog-stereo.monitor

This effectively routes the digitised audio output from the PiHPSDR receiver to the digitised audio input of FreeDV.

Once again we have to use the monitor of the USB PnP Audio Output device as FreeDV does not recognise the PiHPSDR output as a valid input device.

Next, the Output From Computer To Speaker/Headphones device is set to:

alsa_output.usb-Griffin_Technology_Inc_iMic_USB_audio_system-00.analog-stereo

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 …

29 June 20257 February 2026

Rescuing a Bricked Pluto+

I’ve not written an article on the blog for a while now mainly because I’ve not had anything interesting to write about.

Today that changed, as I had a fun little project to dive into.

Steve, M0XVT sent me his Pluto+ SDR transceiver after his rather unsuccessful attempt at updating the firmware. Long story short, he somehow managed to brick the Pluto+ rendering it completely useless.

Not having a Pluto+ myself I’ve never actually played with one before and so this was new and exciting. I have, however played with Steve’s LibreSDR which is a later iteration of the Pluto+ and so, I had an idea of what I was getting into.

Firstly, how do you know when you have bricked your Pluto+?

Fortunately the Pluto+ device is actually quite clever and will inform you when it is bricked. The first sign you will notice is that you can no longer connect to the device using a USB connection to the data socket. The second sign is that when you take the top off the case you’ll notice that the blue LED is off and the green LED is on constantly. These are both classic signs that the device is bricked and needs rescuing

So, how do we rescue a bricked Pluto+?

Firstly, disconnect all cables and power to the device, it needs to be in a powered down state. Next remove the top of the case completely.

Unlike the LibreSDR the Pluto+ doesn’t boot from SD card so, we have to tell it that we want to boot it from an SD card. This is done by shorting the 3v3 and SD-H pins together using a jumper as shown in the photo below. (Black Jumper)

Pluto+ 3v3 and SD-H pins shorted together by black jumper

I believe that the v1 version of the Pluto+ has 1.8v instead of 3.3v, if this is the case on your device just short the SD-H pin to the 1v8 pin instead.

Next we need to make sure that the URST pin is connected to the MIO46 pin as shown by the green jumper in the image above. I put the jumper into this position as I am going to be using firmware that has ethernet support built in. If you want to load the official firmware then you will need to connect the URST pin to the MIO52 pin instead.

Next we need to load the new firmware onto an appropriate SD card. I’m using the F5OEO firmware that has ethernet support with DHCP built in. You can get the firmware from this Github link.

Whilst the firmware is downloading, insert your SD card into your PC and format it using a FAT32 filesystem.

Once the firmware has downloaded, unzip the file and save the contents of the zip file to a directory. Using your favourite file manager or in the case of a Linux junkie like me, the command line, copy the contents of the sdimg folder into the root of the SD card.

Note: That’s copy of the contents of the sdimg folder, not the folder itself.

Make sure to eject your SD card safely before removing it from your PC to ensure you don’t corrupt the contents.

Insert the SD card into the Pluto+ (it’s still powered down at this point with the top off).

Plug the USB A end of the USB cable into your PC but, do not plug the micro USB end into the Pluto+ just yet!

Now this is the tricky part, you need to hold down the DFU Button on the Pluto+ PCB (It’s behind the professor image on the PCB) whilst inserting the micro-USB plug into the DATA port of the Pluto+.

Once you see that the green and blue LED lights come on permanently, let go of the DFU Button and let the Pluto+ boot from the SD card. A short while afterwards the green LED should start flashing, this means your Pluto+ is alive again and has booted from the SD card.

At this point it’s important not to unplug the USB cable and not to remove the SD card from the device, we’re only half way there!

After a little more time the Pluto+ will appear in your file manager as a drive called PlutoSDR, navigate to this drive using your favourite file manager.

At the same time, open another window in your file manager and navigate to the folder where you saved the files from the Zip file. In this directory you will see the following two files:

boot.frm
pluto.frm

Copy these two files from the directory where you saved them into the root of the PlutoSDR drive.

Once this is complete, eject the PlutoSDR drive safely.

The green LED will now start blinking, don’t do anything, just leave everything as it is and the device will now create a new boot image on it’s own built in storage.

This process will take about 5mins so, go grab a cold beer, glass of wine or anything else that takes your fancy, sit back and relax.

Eventually the green LED will stop flashing, wait another minute or so for the process to fully complete.

If the PlutoSDR drive has reappeared in your file manager, safely remove the drive from your file manager and unplug the micro USB connector from the Pluto+ powering it down.

It’s now important to remove the 3v3 to SD-H jumper as we no longer need to boot from SD card.

You can now refit the top cover and the 4 screws and put the case back together. Connect an ethernet cable and micro USB cable to the DATA port and wait.

After about 10-15 seconds the green LED should flash and your Pluto+ is now no longer bricked and ready for use once more.

You can SSH to your Pluto+ using the normal Linux SSH command logging in as root with a password of analog.

If you have PiHPSDR installed and compiled with the SOAPYSDR library and modules (See my article on how to do this easily) you can now start it and connect to your Pluto+ device as normal.

Steve's rescued Pluto+ receiving a signal from my AllStarLink node in PiHPSDR — Steve’s rescued Pluto+ receiving a signal on the 70cm band

This same procedure can be used on Linux, Mac, Windows and RaspberryPi, it is not platform dependent.

If you want your Pluto+ to always boot from the SD card, you can leave the 3v3 pin connected to the SD-H pin permanently.

More soon ….

17 April 202517 April 2025

Updates to my install-pihpsdr.sh script

Over the last few weeks I’ve been working on my install-pihpsdr script to build a version of the DL1YCF PiHPSDR fork that will work with the Adalm Pluo, Pluto+ and LibreSDR transceivers.

Since I don’t own any of these devices, Steve M0XVT has loaned me his Adalm Pluto and LibreSDR devices to test with.

Initially neither of the devices would work with the PiHPSDR build that my script was creating. After some investigation I found this was due to the fact that the developer build script was only building the SOAPYSDR library, it wasn’t building the modules for each device type.

This was easily fixed by adding some extra code that would build the necessary SOAPYSDR modules so that the devices were discovered on the local LAN.

Since I had the devices to hand I took the opportunity to test the updated build script on a number of Linux Distro’s that I have to hand.

PiHPSDR running on Linuxmint 22.1 Cinnamon Edition using the LibreSDR transceiver

I tested the updated build script on Kubuntu 22.04LTS, Linuxmint 22.1 Cinnamon Edition and RaspberryPi 4/5 running the latest RaspberryPi OS 64bit version.

These all worked great with the transceivers and will now make a great platform for QO-100 stations that use either the Adalm Pluto, Pluto+ or LibreSDR devices.

Of course this build of PiHPSDR will also work with the Hermes Lite 2 and RadioBerry devices that I use most of the time in my own radio shack.

The updated PiHPSDR install script can be downloaded from my original blog article on the subject that is located here: https://m0aws .co.uk/?p=3686

The updated build script will most likely work on most Debian based Linux distro’s and build a working version of PiHPSDR. If you find a distro where you have problems please email me and let me know the details and I’ll happily look at the issue and try to resolve it.

Thanks to Steve for the loan of his precious SDR transceivers, I had a lot of fun with them!

More soon …

9 March 202521 June 2025

Hermes Lite 2 Audio

I often get unsolicited good audio reports whilst using my Hermes Lite 2 (HL2) on the HF bands with people asking what settings I am using so, I thought it was time I put together an article on the subject.

I use the DL1YCF enhanced fork of PiHPSDR to drive my HL2, a great OpenSource SDR software package that supports many SDR radios including some very high end, expensive models.

PiHPSDR is extremely configurable via it’s well laid out menu system. It’s possible to change the settings on almost everything which, when combined with really good hardware like the HL2 gives the operator the ability to create an extremely high spec transceiver at a fraction of the price of the typical black box commercial offerings.

Starting at the beginning of the transmit audio chain the first settings to be changed are in the Transmit (TX) menu.

Using my Sennheiser headset I found I needed to set the Radio Mic setting to Mic Boost. This increases the audio level so that it drives the radio properly. It’s important to make sure that boosting the audio doesn’t cause distortion though.

Next I set the TX Filter Low to 150Hz. This ensures I don’t have that nasty bass sound that you hear often on the HF bands today.

The TX Filter High is set to 2700Hz. This gives me a transmit filter width of 2550Hz which is well within the 2700Hz standard for the HF bands.

I also set the compression level to +10dB to increase the average talk power of the audio.

Next in the transmit audio chain is the TX Equalisation. The PiHPSDR software has a very good software defined Parametric EQ menu that provides all the audio tailoring capabilities any HAM operator will ever need.

Having watched many videos by the great Bob Heil, K9EID (SK) I understand that all the articulation in the voice is around the 2500hz range. Today on the HF bands you often hear bass heavy audio that sounds muddy and horrible. This is exactly the type of audio I don’t want to have so, to this end I have adjusted my EQ settings such that the articulation is accentuated to increase clarity and give a little pep to my rather dull sounding voice.

Since the transmit filter width is set from 150Hz to 2700Hz there’s really no point in making EQ adjustments outside of this range. As show above I have made the following changes to the transmit EQ settings in PiHPSDR:

Frequency	Gain
150hz	+6dB
500Hz	+5dB
1500Hz	+6dB
2500Hz	+6dB

The final part of the audio setup is the Mic Gain, I keep this set at 5. This keeps the audio nice and tidy with no IMD.

My HL2 TX Drive is set so that it puts out a maximum of 500mW, this is enough to drive my Xiegu XPA125B amplifier to 100W.

With these settings I find that the Sennheiser headset, PiHPSDR software and the Hermes Lite 2 combination gives me a great signal on all the HF bands.

I hope this helps all those who have asked how my audio is setup and have been so impressed by this great little radio.

More soon …

10 December 202413 May 2025

Using the DL1YCF version of PiHPSDR with the RadioBerry

(This information is also for the Hermes Lite 2, Adalm Pluto, Pluto+ and LibreSDR)

During my RadioBerry build I started out using the version of PiHPSDR that was created just for the RadioBerry. The problem with this is that it is hard coded for a very small screen making it hard to use on a big screen since the user cannot resize the window dynamically.

I decided to look for a forked version of the PiHPSDR software that had the ability to change the window size to suit all use cases. During my search I stumbled across the DL1YCF fork of the source code that has some enhancements, one of which is the ability to change the display size.

In no time at all I had the source code downloaded and compiled only to find that it didn’t work with the RadioBerry. After some investigation I found that this was due to the fact that the RadioBerry software has compiled into it code that is used to access the GPIO pins on the RaspberryPi so that it can communicate with the RadioBerry HAT. This is fine except that the DL1YCF version of PiHPSDR also has code in it to use the GPIO pins. This of course causes a conflict and the net result is that nothing works.

Reading through the source code and Makefile I found that all I needed to do was to compile a version of PiHPSDR without GPIO support. This would then remove the conflict and allow the RadioBerry software to operate correctly.

To this end I put together a download/compile/install script for the DL1YCF version of PiHPSDR that will work on a RaspberryPi with a RadioBerry HAT and give the ability to resize the window to fit any size screen.

The script also works on a Linux Desktop PC running Ubuntu/Kubuntu/Linuxmint/Debian operating systems. (It will most likely work on other distro’s too but, these are all I have to hand currently). You can of course also use this software with a Hermes Lite 2 transceiver.

DL1YCF PiHPSDR running on RaspberryPi 4 with RadioBerry HAT on a large monitor

To install this enhanced version of PiHPSDR on your RaspberryPi/Desktop PC with GPIO support disabled, download the installation script below, unzip it and run it in a terminal on your RaspberryPi/Desktop PC in your home directory. (/home/<your-username>).

The script will download the latest source code from the DL1YCF github, disable the GPIO code and then compile and install it to your computer. If installing on a RaspberryPi it will create an icon on the desktop for you to use to start the software.

If installing on a PC then you will need to create your own desktop icon as the one created only works on a RaspberryPi. You can of course just start the software from the command line in a terminal. (My preferred method).

If you have a RaspberryPi 5 then I highly recommend that you run this version of PiHPSDR on it as it has a lot more computing power and handles using dual receive with ease. It will run on a Pi4 but, you will load the CPU more as it’s not as powerful as the later model Pi5.

The script will ask if you want to compile in SOAPYSDR support so that PiHPSDR will work with RTL-SDR, Adalm-Pluto, Pluto+ and LibreSDR. Enter Y to compile in support or N if you don’t need it.

install-pihpsdr-v22-update Download

I hope this proves useful to all the RadioBerry, Hermes Lite 2 and Pluto users out there who want to use PiHPSDR on a big screen.

More soon …

10 December 202415 April 2025

RadioBerry Software Install

For the last week or so I’ve been playing with a RadioBerry HAT for my RaspberryPi computer. The RadioBerry is a cut down version of the Hermes Lite 2 with just 20mW output power and separate TX and RX antenna ports. It’s a really neat little package that sits on top of a RaspberryPi4/5 and creates a neat little HF transceiver.

I initially started with the RadioBerry HAT on my Pi5 but, I soon realised that the software really doesn’t work well at all on the Pi5. I’m not 100% sure as to why but, for some reason it holds one core at 100% continuously. It seems that the RadioBerry software is single threaded. The end result is that on the Pi5 you cannot use a sample rate above 9600 before the IQ stream starts to stutter.

By contrast, installing the RadioBerry software onto a Pi4 it performs perfectly upto the maximum sample rate of 384000 without any stuttering. I’ll need to spend some time going through the source code to try and determine why it doesn’t work correctly on a Pi5.

Whilst going through the source I discovered that the developer has put some code in that collects data from the running computer and sends it to the developer’s website. Some of this data is then made public via his website, http://www.pa3gsb.nl/radioberry/api/read.php

One of the things displayed on the website is the Mac address of the RaspberryPi on which the RadioBerry is running. This is a security risk and should never be done!

The most annoying thing is that this is done without authorisation. The installation doesn’t state that it’s going to collect data every time you start your RaspberryPi computer nor does it offer the ability to opt out. It also doesn’t inform the user that it’s going to pass the data on to a third party. In some cases it even collects HAM Radio Callsign and location data and displays it on a public website, a clear breach of the UK/European Data Protection Law.

Finding spyware in open source software is really poor and something most open source developers would never consider doing.

To this end I have disabled the spyware in the version of the RadioBerry software that I am using and am making it available to everyone else to use via this blog.

So, to install the RadioBerry software you just need to download the installation script and run it in a terminal on your RaspberryPi computer.

The script will download the modified source code, compile it and install it on your RaspberryPi ready for you to use.

RadioBerry installation Script Download

I encourage everyone that downloads the script and the source code to take a look at it and ensure you are happy with it. It’s important to know what you are running on your computer and what it does.

You can find the spyware code in the register.c file (It’s all commented out with “//” marks). The function now doesn’t pass any data at all to the public website.

I hope some of my readers who are experimenting with the RadioBerry transceiver find this useful.

I will soon be publishing an article on an enhanced version of PiHPSDR from DL1YCF to use with the the RadioBerry to complete the project.

Important Update:

There is an issue with the RadioBerry code that renders it useless if you use a kernel later than the version shown below:

Linux Radioberry 6.6.51+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.6.51-1+rpt3 (2024-10-08) aarch64 GNU/Linux

Updating the O/S Kernel to any version later than the version shown above will stop the RadioBerry software from working. Recompiling of the code also fails due to the Kernel update and at the time of writing this cannot be fixed without a code rewrite by the original developer.

I also recommend that once you have built a working RadioBerry on a RaspberryPi 4 you should disable the automatic updates of the O/S to stop the system from failing in the future.

You can disable the automatic updates by entering the following commands into a terminal:

sudo systemctl disable apt-daily.service
sudo systemctl disable apt-daily.timer

sudo systemctl disable apt-daily-upgrade.timer
sudo systemctl disable apt-daily-upgrade.service

You can check the version of the kernel you have installed using the following command in a terminal:

uname -a

Hopefully this will help anyone that is having issues with their RadioBerry after an O/S update.

More soon …

19 November 202429 November 2024

Another new radio!

Many years ago when I lived in France I had a Flex-3000 transceiver, one of the first fully SDR transceivers on the market. It was paired with a proprietary Windows XP application called PowerSDR (now Opensource and called Thetis) and connected via a firewire connection.

17 years later I am once again venturing into the world of SDR transceivers in the form of a Hermes Lite 2. (HL2)

The HL2 hardware is available via the Makerfabs website in kit form. I ordered the HL2 motherboard, the N2ADR Filter Board to ensure a clean signal from the transceiver and the enclosure. Total cost for all the parts and shipping was £288.00 including all taxes.

The kit took about 10 or so days to arrive and was very easy to put together making sure to fit the PA transistor heat sink the right way round so that it doesn’t short out the main board. (There are many videos about this on YouTube)

Once the hardware was put together I needed to install some software to control/drive the HL2. Being a heavy weight Linux user my software choice had to come from the Opensource world.

M0AWS Hermes Lite 2 SDR Trasnceiver and Xiegu XPA125B Amplifier

After much research and chatting with other HAMs on the Matrix who have the HL2 I found that most people use the closed source SDR Console software to control the transceiver. Since this software is for Windows it’s not something I can use as I don’t have any Windows PCs, they’re all Linux only.

To this end I started researching Linux SDR software for the HL2 and decided that PiHPSDR was the one I was going to try first.

PiHPSDR was originally written for the RaspberryPi 3/4/5 single board computers (SBCs) but, I wanted to have a go at compiling it on my Kubunu Linux desktop PC. I found it straight forward to follow the instructions in the pihpsdr-install.pdf file and in no time at all I had the software compiled and running.

PiHPSDT running on Kubuntu Linux 22.04LTS — PiHPSDR running on Kubuntu Linux 22.04LTS

PiHPSDR is infinitely configurable and thus it feels like it has an infinite number of menus and options. Since the HL2 has two separate receivers, it’s possible to listen to two bands at the same time. This is the one feature I really missed more than anything with my FTDX10 so, I’m glad to have dual receive capability back once more!

Going through all the settings I realised that the A and B VFOs have individual settings. Initially I setup the software using just VFO A but, when I switched over to VFO B none of my settings were there. I then had the realisation that the settings apply only to the active VFO. I quickly went through all the settings again for VFO B and all was well.

In no time at all I was on the air with just 5w as my Xiegu amp hadn’t arrived. Not being perturbed I tuned up on the 15m band and started searching for stations. Interestingly it was CQWW SSB weekend and the band was full of contest stations. Working my way along the spectrum I found I was able to work quite a few stations with ease using my vertical and inverted-L antennas.

Contacts of note were VE3KG at 3406 Miles, VE3JM at 3382 Miles, RW9DX at 2380 Miles, KC1XX at 3331 Miles and N1DE at 3600 Miles. I also worked a bunch of European stations and had a great time giving away points with my little QRP rig.

Contests are a good time to try out new radios as all the big stations with good ears are on the bands and make the effort to get us QRP guys in their logs.

I have been extremely impressed with the receivers in the HL2 radio. It handles both strong and weak stations exceptionally well. PiHPSDR really does have brick-wall filtering and I was able to work the weaker stations right next to large contest stations with ease. At no time did the front-end of the receiver get overloaded.

Below is a short video clip of a conversation on the 80m band. The band was quite noisy however, with a reduction of the AGC gain and the 2700Hz filter it’s possible to remove almost all the noise.

Hermes Lite 2 SSB reception on the 80m Band

On CW the radio is a real delight. With the filtering and AGC gain control I am able to use extremely narrow receive filters without any ringing whatsoever. I would say that on CW the HL2 is as good as my FTDX10 when it comes to receiving even the weakest of stations.

I’m sure on paper the FTDX10 receiver has better numbers however, to the ear there really is no discernible difference.

Below is a short video clip of D4DX on CW on the 80m band. The band was noisy but, with the 100Hz filter enabled and clever use of the AGC Gain I was able to remove almost all the noise completely, reducing fatigue on the ears and making reception very easy even though there was some fairly deep QSB at times.

Receiving D4DX on CW on the 80m band using 100Hz filter and reduced AGC gain

A few days later my Xiegu XPA125B amplifier arrived. Unfortunately the amp didn’t come with the normal PTT lead that comes from the factory and is detailed in the user manual. For some bizarre reason this is a chargeable option when you buy the amp from Martin Lynch and Sons even though it is included from the factory.

This meant I had to make a lead which was a problem as I didn’t have one of the mini DIN plugs required for the connection to the amplifier. Jumping onto Amazon I ordered a packet of two and sat back and waited for their arrival.

A couple of days later the DIN plugs arrived and I quickly made up the necessary phono/RCA to mini DIN lead and got the amp operational.

The Xiegu XPA125B isn’t cheap but, it’s a really nice bit of kit. The neat little LCD display keeps you informed of power O/P, I/P and O/P SWR, voltage, current draw, temperature and band selected.

With just 0.7w of input from the HL2 I’m able to get a full 100w O/P from the amp. On the lower bands I have to reduce the O/P from the Hermes Lite 2 even further so that I don’t over drive the amp.

Being an avid Short Wave Listener (SWL) I wanted to see how the HL2 performed when listening to the big AM broadcast stations. To my surprise it makes an excellent SWL receiver with better AM demodulation than many of the more expensive radios. Having the option to select receive filters up to 16Khz wide I found I was able to get the best audio possible from many of the broadcast stations including Radio Caroline on 648Khz. It’s quite an improvement over the 12Khz maximum on the FTDX10.

Listening to AM Broadcast stations

What makes this project even more exciting is that both the hardware and software are from the OpenHardware/OpenSource world. The complete circuit diagram, PCB layout and information is available for all to download, something you don’t often see these days!

PiHPSDR is one of the nicest SDR applications I’ve seen in the Linux world and even comes with a 200 page downloadable user manual. Something you don’t see in many Opensource projects. The source code for the application is downloadable and you are able to make your own changes to it without restriction.

Overall I am really pleased with the Hermes Lite 2 SDR transceiver.
It has two excellent receivers, is infinitely configurable via the PiHPSDR software and performs extremely well under all conditions. Since getting the radio I haven’t even switched on the FTDX10.

More soon …

12 June 202422 June 2024

Deep Dive – Node-RED QO-100 Satellite Ground Station Dashboard

Following on from my article about my QO-100 Satellite Ground Station Complete Build, this article goes into some detail on the Node-RED section of the build and how I put together my QO-100 Satellite Ground Station Dashboard web app.

The Node-RED project has grown organically as I used the QO-100 satellite over time. Initially this started out as a simple project to synchronise the transmit and receive VFO’s so that the SDR receiver always tracked the IC-705 transmitter.

Over time I added more and more functionality until the QO-100 Ground Station Dashboard became the beast it is today.

M0AWS QO-100 ground Station Control Dashboard built using Node-RED. — M0AWS QO-100 Ground Station Control Dashboard built using Node-RED.

Looking at the dashboard web app it looks relatively simple in that it reflects a lot of the functionality that the two radio devices already have in their own rights however, bringing this together is actually more complicated than it first appears.

Starting at the beginning I use FLRig to connect to the IC-705. The connection can be via USB or LAN/Wifi, it makes no difference. Node-RED gains CAT control of the IC-705 via XMLRPC on port 12345 to FLRig.

To control the SDR receiver I use GQRX SDR software and connect to it using RIGCTL on GQRX port 7356 from Node-RED. These two methods of connectivity work well and enables full control of the two radios.

M0AWS Node-RED QO-100 Ground Station Dashboard - 12/06/24 — M0AWS Node-RED QO-100 Ground Station Dashboard Flow as of 12/06/24

The complete flow above looks rather daunting initially however, breaking it down into its constituent parts makes it much easier to understand.

There are two sections to the flow, the GQRX control which is the more complex of the two flows and the comparatively simple IC-705 section of the flow. These two flows could be broken down further into smaller flows and spread across multiple projects using inter-flow links however, I found it much easier from a debug point of view to have the entire flow in one Node-RED project.

Breaking down the flow further the GQRX startup section (shown below) establishes communication with the GQRX SDR software via TCP/IP and gets the initial mode and filter settings from the SDR software. This information is then used to populate the dashboard web app.

M0AWS - Node-RED QO-100 Ground Station Dashboard - GQRX Startup — M0AWS Node-RED QO-100 Ground Station Dashboard – GQRX Startup Flow

The startup triggers fire just once at initial startup of Node-RED so it’s important that the SDR device is plugged into the PC at boot time.

All the startup triggers feed information into the RIGCTL section of the GQRX flow. This section of the flow (shown below) passes all the commands onto the GQRX SDR software to control the SDR receiver.

M0AWS - QO-100 Ground Station Dashboard - GQRX RIGCTL flow — M0AWS Node-RED QO-100 Ground Station Dashboard – GQRX RIGCTL Flow

The TCP RIGCTL -> GQRX node is a standard TCP Request node that is configured to talk to the GQRX software on the defined IP Address and Port as configured in the GQRX setup. The output from this node then goes into the Filter RIGCTL Response node that processes the corresponding reply from GQRX for each message sent to it. Errors are trapped in the green Debug node and can be used for debugging.

The receive S Meter is also driven from the the output of the Filter RIGCTL Response node and passed onto the S Meter function for formatting before being passed through to the actual gauge on the dashboard.

Continuing down the left hand side of the flow we move into the section where all the GQRX controls are defined.

M0AWS - QO-100 Ground Station Dashboard - GQRX Controls — M0AWS Node-RED QO-100 Ground Station Dashboard – GQRX Controls Flow

In this section we have the VFO step buttons that move the VFO up/down in steps of 10Hz to 10Khz. Each button press generates a value that is passed onto the Set DeltaFreq change node and then on to the Calc new VFO Freq function. From here the new VFO frequency is stored and passed onto the communications channel to send the new VFO frequency to the GQRX software.

The Mode and Filter nodes are simple drop down menus with predefined values that are used to change the mode and receive filter width of the SDR receiver.

Below are the HAM band selector buttons, each of these will use a similar process as detailed above to change the VFO frequency to a preset value on each of the HAM HF Bands.

The QO-100 button puts the transmit and receive VFO’s into synchro-mode so that the receive VFO follows the transmit VFO. It also sets the correct frequency in the 739Mhz band for the downlink from the LNB in GQRX SDR software and sets the IC-705 to the correct frequency in the 2m VHF HAM band to drive the 2.4Ghz up-converter.

The Split button allows the receive VFO to be moved away from the transmit VFO for split operation when in QO-100 mode. This allows for the receive VFO to be moved away so that you can RIT into slightly off frequency stations or to work split when working DXpedition stations.

The bottom two Memory buttons allow you to store the current receive frequency into a memory for later recall.

At the top right of this section of the flow there is a Display Band Plan Info function, this displays the band plan information for the QO-100 satellite in a small display field on the Dashboard as you tune across the transponder. Currently it only displays information for the satellite, at some point in the future I will add the necessary code to display band plan information for the HF bands too.

The final section of the GQRX flow (shown below) sets the initial button colours and starts the Powermate USB VFO knob flow. I’ve already written a detailed article on how this works here but, for completeness it is triggered a few seconds after startup (to allow the USB device to be found) and then starts the BASH script that is used to communicate with the USB device. The output of this is processed and passed back into the VFO control part of the flow so that the receive VFO can be manually altered when in split mode or in non-QO-100 mode.

M0AWS - QO-100 Ground Station Dashboard - Powermate VFO section — M0AWS Node-RED QO-100 Ground Station Dashboard – Powermate VFO Flow

The bottom flows in the image above set some flow variables that are used throughout the flow and then calculates and sets the RIT value on the dashboard display.

The final section of the flow is the IC-705 control flow. This is a relatively simple flow that is used to both send and receive data to/from the IC-705, process it and pass it on to the other parts of the flow as required.

M0AWS - QO-100 Ground Station Dashboard - IC-705 control flow — M0AWS Node-RED QO-100 Ground Station Dashboard – IC-705 Control Flow

The IC-705 flow is started via the timestamp trigger at the top left. This node is nothing more than a trigger that fires every 0.5 seconds so that the dashboard display is updated in near realtime. The flow is pretty self explanatory, in that it collects the current frequency, transmit power, SWR reading, PTT on/off status and S Meter reading each time it is triggered. This information is then processed and used to keep the dashboard display up to date and to provide VFO tracking information to the GQRX receive flow.

On the left are the buttons to change band on the IC-705 along with a button to tune to the VOLEMT on the 60m band. Once again there two memory buttons to save and recall the IC-705 VFO frequency.

The Startup PTT Colour trigger node sets the PTT button to green on startup. The PTT button changes to red during transmit and is controlled via the Toggle PTT function.

At the very bottom of the flow is the set transverter IF Freq function, this sets the IC-705 to a preselected frequency in the 2m HAM band when the dashboard is switched into QO-100 mode by pressing the QO-100 button.

On the right of the flow there is a standard file write node that writes the 2.4Ghz QO-100 uplink frequency each time it changes into a file that is used by my own logging software to add the uplink frequency into my log entries automatically. (Yes I wrote my own logging software!)

The RX Audio Mute Control filter node is used to reduce the receive volume during transmit when in QO-100 full duplex mode otherwise, the operator can get tongue tied hearing their own voice 250ms after they’ve spoken coming back from the satellite. This uses the pulse audio system found on the Linux platform. The audio is reduced to a level whereby it makes it much easier to talk but, you can still hear enough of your audio to ensure that you have a good, clean signal on the satellite.

As I said at the beginning of this article, this flow has grown organically over the last 12 months and has been a fun project to put together. I’ve had many people ask me how I have created the dashboard and whether they could do the same for their ground station. The simple answer is yes, you can use this flow with any kind of radio as long as it has the ability to be controlled via CAT/USB or TCP/IP using XMLRPC or RIGCTL.

To this end I include below an export of the complete flow that can be imported into your own Node-RED flow editor. You may need to make changes to it for it to work with your radio/SDR but, it shouldn’t take too much to complete. If like me you are using an IC-705 and any kind of SDR controlled by GQRX SDR software then it’s ready to go without any changes at all.

M0AWS-QO-100 Ground Station Dashboard 12 June 2024 Download

More soon …

5 June 20245 June 2024

QO-100 Satellite Ground Station Complete Build

I get quite a few emails from readers of my blog asking how my QO-100 satellite station is put together and so, I thought perhaps now is a good time to put together an article detailing the complete build.

My QO-100 satellite ground station is built around my little Icom IC-705 QRP transceiver, it’s a great little rig and is ideal for the purpose of driving a 2.4Ghz transverter/up-converter.

Of course all the software used for the project is Opensource and freely available on the internet.

M0AWS QO-100 Ground Station Build Visual (Click to Enlarge)

The station comprises of the following building blocks:

Icom IC-705 Transceiver
DXPatrol 28/144/433Mhz to 2.4Ghz Up-Converter
DXPatrol GPSDO Reference Oscillator
DXPatrol 2.4Ghz 5/12w Amplifier
Nolle Engineering 2.2 turn 2.4Ghz IceCone Helix Antenna
1.1m (110cm) Off-set Dish
Bullseye 10Ghz LNB
Bias-T to feed 12v to LNB
NooElec SmartSDR Receiver
PC Running Kubuntu Linux Operating System
GQRX SDR Opensource Software
Griffin Powermate USB VFO Knob
QO-100 Ground Station Dashboard developed using Node-RED
LMR400-UF/RG58 Coax Cable

M0AWS QO-100 1.1m off-set Dish and IceCone Helix antenna ground station — M0AWS QO-100 1.1m (110cm) off-set Dish with IceCone Helix antenna and Bullseye LNB.

To get a good clear view of the QO-100 satellite I have the dish mount 3.2m above the ground. This keeps it well clear of anyone walking past in the garden and beams the signal up at an angle of 26.2 degrees keeping well clear of neighbouring gardens.

The waterproof enclosure below the dish houses all the 2.4Ghz equipment so that the distance between the feed point and the amplifier are kept to a minimum.

The DXPatrol amplifier is spec’d to run at 28v/12w or 12v/5w, I found that running it at 28v produced too much output for the satellite and would cause the LEILA alarm on the satellite to trip constantly. Running the amp at 12v with a maximum of 5w output (average 2.5-3.5w) is more than enough for me to have a 5/9+10 signal on the transponder.

The large 1.1m dish gives me quite an advantage on receive enabling me to hear the very weak stations with ease compared to other stations.

2.4Ghz ground station enclosure ready for testing

The photo above shows the 2.4Ghz equipment mounted in the waterproof enclosure below the dish. This photo was taken during the initial build phase before I rewired it so, the amplifier is shown connected to the 28v feed. To rewire the amp to 12v was just a matter of removing the 28v converter and connecting the amp directly to the 12v feed instead. This reduced the output from a maximum of 12w down to a maximum of 5w giving a much better (considerate) level on the satellite.

It’s important to keep all interconnects as short as possible as at 2.4Ghz it is very easy to build up a lot of loss between devices.

For the connection from the IC-705 to the 2.4Ghz Up-Converter I used a 7m run of
LMR-400 coax cable. The IC-705 is set to put out just 300mW on 144Mhz up to the 2.4Ghz converter and so it’s important to use a good quality coax cable.

Once again the output from the 2.4Ghz amplifier uses 1.5m of LMR-400-UF coax cable to feed up to the 2.2 turn Icecone Helix Antenna mounted on the dish. This keeps loss to a minimum and is well worth the investment.

Bullseye 10Khz High Stability Unversal Single LNB for 10.489-12.750Ghz

The receive path starts with a Bullseye LNB, this is a high gain LNB that is probably one of the best you could use for QO-100 operations. It’s fairly stable frequency wise but, does drift a little in the summer months with the high temperature changes but, overall it really is a very good LNB.

The 12v feed to the LNB is via the coax and is injected by the Bias-T device that is in the radio shack. This 12v feed powers the LNA and associated electronics in the LNB to provide a gain of 50-60dB.

Bias-T to inject 12v feed into the coax for the Bullseye LNB

From the Bias-T the coax comes down to the NooElec SmartSDR receiver. This is a really cheap SDR device (<£35 on Amazon) based on the RTL-SDR device but, it works incredibly well. I originally used a Funcube Dongle Pro+ for the receive side however, it really didn’t handle large signals very well and there was a lot of signal ghosting so, I swapped it out for the NooElec SDR and haven’t looked back since.

The NooElec SmartSDR is controlled via the excellent Opensource software GQRX SDR. I’ve been using GQRX SDR for some years now and it’s proven itself to be extremely stable and reliable with support for a good number of SDR devices.

To enhance the operation of the SDR device I have added a Griffin Powermate VFO knob to the build. This is an old USB device that I originally purchased to control my Flex3000 transceiver but, since I sold that many moons ago I decided to use it as a VFO knob in my QO-100 ground station. Details on how I got it working with the station are detailed in this blog article.

Having the need for full duplex operation on the satellite this complicates things when it comes to VFO tracking and general control of the two radios involved in the solution and so I set about creating a QO-100 Dashboard using the great Node-RED graphical programming environment to create a web app that simplifies the management of the entire setup.

The QO-100 Dashboard synchronises the transmit and receive VFO’s, enables split operation so that you can transmit and receive on different frequencies at the same time and a whole host of other things using very little code. Most of the functionality is created using standard Node-RED nodes. More info on Node-RED can be found on the Opensource.radio Wiki or from the menu’s above.

I’ll be publishing an article all about the QO-100 Dashboard in the very near future along with a downloadable flow file.

I’m extremely pleased with how well the ground station works and have had well in excess of 500 QSO’s on the QO-100 satellite over the last last year.

More soon …

13 May 202413 May 2024

Update to my NodeRed QO-100 Dashboard

Ever since my QO-100 ground station has been operational I’ve been using my NodeRed QO-100 Dashboard to control my IC-705 and GQRX SDR software to drive my NooElec SmartSDR receiver. This gives me a full duplex ground station with both transmit and receive VFO’s synchronised.

This solution has worked incredibly well from the outset and over time I’ve added extra functionality that I’ve found to be useful to enhance the overall setup.

The latest addition to the ground station solution is a Sennheiser Headset that I picked up for just £56 on Amazon (Much cheaper than the Heil equivalents at the HAM stores!) and have found it to be excellent. The audio quality from both the mic and the headphones is extremely good whilst being light and comfortable to wear for extended periods.

M0AWS - Sennheiser SC 165 — M0AWS – Sennheiser SC 165 Headset

To incorporate this into the ground station the headset is connected to my Kubuntu PC and the audio chain to the IC-705 is sent wirelessly using the latest version of WFView. This works extremely well. The receive audio comes directly from the GQRX SDR software to the headphones so that I have a full duplex headset combination.

Audio routing is done via pulse audio on the Kubuntu PC and is very easy to setup.

Since I no longer have a mic connected to the IC-705 directly I found that I needed a way to operate the PTT wirelessly and this is where the latest addition to my NodeRed QO-100 Dashboard comes in.

Adding a little functionality to the NodeRed flow I was able to create a button that toggles the IC-705 PTT state on and off giving me the ability to easily switch between receive and transmit using a simple XMLRPC node without the need for a physical PTT button.

M0AWS - Additional NodeRed PTT Flow — M0AWS – Additional NodeRed PTT Flow

The PTT state and PTT button colour change is handled by the Toggle PTT function node shown in the above flow. The code to do this is relatively simple as shown below.

M0AWS - NodeRed Toggle PTT Function to change button colour — M0AWS – NodeRed Toggle PTT Function to change button colour

The entire QO-100 Dashboard flow has grown somewhat from it’s initial conception but, it provides all the functionality that I require to operate a full duplex station on the QO-100 satellite.

M0AWS - NodeRed QO-100 Dashboard complete flow — M0AWS – NodeRed QO-100 Dashboard complete flow

This simple but, effective PTT solution works great and leaves me hands free whilst talking on the satellite or the HF bands when using the IC-705. This also means that when using my IC-705 it only requires the coax to be connected, everything else is done via Wifi keeping things nice and tidy in the radio shack.

M0AWS - Updated NodeRed QO-100 Dashboard with PTT button — M0AWS – Updated NodeRed QO-100 Dashboard with PTT button

The image above shows the QO-100 ground station in receive cycle with the RX/TX VFO’s in split mode as the DX station was slightly off frequency to me. The PTT button goes red when in TX mode just like the split button shown above for visual reference.

As you can probably tell, I’m a huge fan of NodeRed and have put together quite a few projects using it, including my HF Bands Live Monitoring web page.

More soon …