This month I worked on our Baseband FM (BBFM) paper, “RADE for Land Mobile Radio: A Neural Codec for Transmission of Speech over Baseband FM Radio Channels” which is now available here on arxiv.org.

This paper is written at a professional technical level and has a description of the BBFM technology including design, derivation of our linearised FM model, training, ASR evaluation results, and the UHF Radio demo. There is a complimentary BBFM web page with demo samples, and Github branch with source code.

This months work included review corrections, upload and publishing on arxiv.org. Quite a lot of work to complete this paper by my co-author Tibor Bece, contributor George Karan, and myself however we are very pleased with the results. Thank you Bill Cowley and Jean-Marc Valin for reviewing the paper and your many useful comments.

Also this month I prepared a poster presentation for the WASPAA 2025 conference I am attending on October.

This months RADE V2 development was focused on fine timing estimator integration. In particular I am carefully testing the combined system to ensure the fine timing estimator doesn’t cause any distortion in the decoded RADE V2 speech.

This month has mainly been more refinements and bugfixes for the main FreeDV application and the FreeDV Reporter server. Some of these bugfixes and refinements include:

• Preventing random row selections in the FreeDV Reporter window when using Linux.
• Moving the Spectrum plot averaging setting to Tools->Options to free up some space in the window.
• Adding a sample file for RADE to allow users to test their own receive setup (and cleaning up sample files that are no longer useful).
• Including /dev/serial/* in serial device drop-down lists (Linux).
• Performance improvements in the audio pipeline, GUI and FreeDV Reporter handling.
• CI build reliability improvements.
• Fixing spurious errors on startup when changing locales. (macOS)
• Fixing lockups when testing invalid PTT configurations.
• FreeDV Reporter server: Fix more deadlock bugs preventing connections from completing.

Additionally, the PLT approved implementation of Automatic Gain Control (AGC) functionality in FreeDV. This was something much desired by users as it makes adjusting microphone volume much easier, improving TX and RX audio quality even further. This has now been merged and will be part of version 2.0.2.

On the topic of radio integration, I also began porting the ezDV FlexRadio implementation to Linux (specifically, Raspberry Pi 4) during the last few days of the month. This work will allow us to eventually produce a waveform file that can be uploaded using SmartSDR and effectively “build in” FreeDV support. Hopefully I’ll have more to update in my next report.

More information can be found in the commit history below:

• freedv-gui
• freedv-reporter

(Note that all commit logs above were generated with the following command line:)

git log --author="member@email" --after "Month 1, 2025" --before "Month 31, 2025 23:59:59" --all