Generating sideband to transmit on a HackRF

While working on my C port of FreeDV RADE1 I wanted a reliable radio signal to test with. While I have off air recordings from the FreeDV GUI app I thought it would be nice to generate my own files to transmit with the HackRF Portapack Mayhem which can record to C16 files and play them back. There's a TXT file with each recording that specifies the sample rate and output frequency.

I've made a python utility that can read a WAV file recording and produce C16 sideband. Here's how it sounds.

The code is pretty short so I've published it as a gist on GitHub.

The HackRF is a wonderful tool for radio experimentation. I'm using the standalone Mayhem but it works just as well from a computer via USB with hackrf_transfer.

FreeDV Sunday net - 23 stations

An excellent FreeDV RADE1 net here in South East Australia with 23 stations on frequency. Some for the first time. Stations: VK5KHZ, VK5KFG, VK5AG, VK3ZUM, VK5KVA, VK3UBK, VK3SRC, VK3KEZ, VK3JCO, VK3GTP, VK3FC, VK3DJB, VK3CDH, VK3BQO, VK3BAL, VK2YW, VK2XOR, VK2UMZ, VK2KNC, VK2DWG, VK2AWJ, VK5HM and me VK3TPM. 

Normally I call in stations in alphabetical order but today I thought I'd trick Jack VK5KVA, by going in reverse.

 

C port of FreeDV RADE going well - transmit working today

Today marked a milestone in my investigation into using Claude Code with a complex codebase. I had a FreeDV RADE contact with another station using code it wrote under my instruction in just one week - very much part time. Here's a receive demo:

My thanks as always to Joe, VK3SRC, for assistance in testing and feedback. Also thanks to Britt, VK3AOB who responded to my first call which I really expected to not be decodable.

Here's how Claude Code looks while working on a bug in the code (click to enlarge):

 I'm developing on Linux Mint. The app is C++ using GTK and Claude seems very knowledgable in this scenario. I suspect that the large amount of open source software around is a great advantage for this sort of thing.

The code is here: https://github.com/peterbmarks/radae_decoder As you can see the name of the project is no longer correct as it encodes as well.

Tech talk on ABC Radio - Is OpenClaw the future?

Have you heard of a tool called OpenClaw? Apparently, you install it on your computer and it acts like your personal assistant. it's generating a lot of buzz and users are saying it's like they're 'finally getting a glimpse of the future'. 

Tech Talk takes a look at this and how the big four tech companies are faring after they've spent big on AI. 

Peter Marks, mobile software developer and technology commentator from Access Informatics, joined Philip Clark and listeners to Nightlife with the latest tech news. Listen here: https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/106328266 

FreeDV Sunday net - excellent conditions

An excellent Sunday FreeDV net this morning with VK2, VK3 and VK5 stations all with good SNRs. 

Some interest was expressed in the C port of the RADAE python code which is encouraging. On the frequency, (not everyone transmitted), VK2AMF, VK2AWJ, VK2DWG, VK2GMH, VK2YE, VK3DJB, VK3FC, VK3GTP, VK3JCO, VK3KEZ, VK3XCI, VK3YV, VK3ZUM, VK4TEW, VK5ABE, VK5KHZ, VK5KVA, VK5LN, VK5ST, VK6YR, VK3BAL (running three copies of FreeDV!), VK3AOB, and me VK3TPM.

Experimental C port of the FreeDV RADEV1

One of the objectives of the work on RADEV2 is to replace the currently required Python runtime from the distributed FreeDV app. This would make it easier to install, smaller, and hopefully more efficient. (Other objectives are improvements in how it works). Python is an important part of the project and is used for prototyping and testing - that won't change.

Re-writing all the python in C is a daunting, tedious, expert task, estimated to take many months that would result in an app that works pretty much the same as it does today.

I've been experimenting with Anthropic's Claude Code recently and it occurred to me that one of the things LLMs are particularly good at is translating between languages, human or programming. The result of just a few days of guiding Claude Code is an experimental RADEV1 decoder app.

The intial work, which includes command line tools to decode and encode from and to WAV files is on github here.

The proof of concept Linux application shown above is in a Github repo here. 

While it seems to work and does pass important tests, this is not code supported by the project at this time.

Claude Code enabled me to attempt something I wouldn't dream of until now. It was quite a big job for it (I hit my quota on two separate days and had to wait to resume).

Working with an LLM to write software does still require enough knowledge to know what to ask for and to guide the work.

I hope this work will encourage others to develop innovative FreeDV RADE software along side the official FreeDV App which remains the reference release. My sincere thanks to Dr David Rowe for his fantastic work and his help and encouragement with this little experiment.

A well used laptop keyboard

Many years ago I handed down a MacBook air to our youngest daughter. She used it until I handed down a later machine. Last week she returned it and I'm amazed to see how heavily she had used it over the years without complaint.

It still works although the battery is dead now. 

Some people complain that Apple is expensive but I think it's value for money.

This kind of keyboard wear reminds me of an HP25C calculator I had many years ago. It was also a piece of quality engineering and, as I recall, one feature was that the symbol on the buttons was plastic that extended right through the key so it would never wear off. 

Xiegu X6200 review

Keen to do more field operating (and overnight camping). My rig of choice has been the Elecraft KX3 with it's excellent antenna tuner and easy to read LCD display. Since using rigs with a waterfall display of the band I find it hard to going back to tuning up and down trying to find stations. 

I purchased a Xiegu X6200 from AliExpress for AU$1200. 

It has some terrific features for portable operation:

• Decent flat battery pack that clips on the back
• Wonderful sharp and bright display
• Excellent built-in antenna tuner
• USB-C socket with interfaces for CAT control and audio
• Handles to protect the knobs

The front facing speaker is small but quite effective. Surprisingly it is NOT a touch screen (although if you connect a mouse you get a mouse pointer). This means that to go through menus you must spin the outer lower left knob to move between settings and spin the inner knob to change a setting.

A waterfall with a touch screen is a wonderful thing and on a 7300 being able to tap a signal to tune there is missing here. Tuning with the knob is a little laggy and seems to have some inertia for some reason. (Unfortunately clicking on the waterfall with a mouse isn't supported).

The rig is certainly a quality build. All the controls feel excellent and the battery pack, sadly proprietary, clips on to the back. It's remarkably compact and solid feeling. The microphone has a full set of buttons including three configurable buttons for things like NR or NB. You can also direct enter frequencies. There is also a built-in microphone and PTT button so you could use it like a hand-held.

Because of my focus on digital modes, I wouldn't buy a radio without a direct USB connection and this radio does it all. I have found that it's rather sensitive to the cable being used and I've experienced the serial devices not appearing even though I was using a USB-C to USB-C cable that clearly carries data as it works with hard disks. The supplied USB-C to USB-A cable.

When plugged into a computer two serial devices appear. The second one is the CAT port (the other is a serial terminal).

Here's the settings that work with fldigi:

Here's the settings that work with FreeDV:

Rig: Xiegu X6200

Serial Port: /dev/ttyACM1

Baud Rate: 19200

Data bits, stop bits, handshake: Default

PTT Method: CAT

Mode: Data/Pkt

Split Operation: None.

Audio Input: alsa_input.usb-C-Media_Electronics_inc.USB_Audio_Device-00.mono-fallback

Audio Output: also_output.usb-C-Media_Electronics_inc._USB_Audio_Device-00.analog-stereo

The radio should switch to mode: U-DIG or L-DIG depending on band with FreeDV

I note that the audio level to WSJT-X is too high, 88dB. I needed to reduce "mic" gain in Linux sound settings.

Bugs

Xiegu has a history of software bugs in their radios. It seems some never get fixed. The most disappointing one for me is that I'm on the latest firmware 1.0.7 and I cannot get it to connect to Wifi which is a pity as there's a WFView server (Icom radio networking server) built in and it would be great to remote access the radio.

There is a discussion group at https://xiegu-x6200.groups.io/g/main/topics that looks to be a great resource.

Conclusion

I think this is quality radio for the money. I joined our club 80m net this week and got good reports from other stations. The radio puts out about 4W on the attached battery and about 9W with external power.