The working acronym for the Radio Autoencoder has been changed from RADAE to the more use-friendly RADE (pronounced”raid”).
This month I continued working on getting RADE V1 into a form where it can be used in real time. The hybrid Python/C model seems to be working out quite well, meeting our goal of enabling hams to use the waveform early, and allowing us to spot any significant bugs that we may have missed with the stored file test campaign. It also makes development really fast and efficient compared to coding in C.
To support the RADE release I wrote a RADE Introduction document, that covers the basics of the mode and a description of the waveform. Thank you to the test team for providing feedback on this document, and Yuichi, JH0VEQ, for a Japanese translation.
Initial reports of on air performance are encouraging, and match our experience from the stored file test campaign. This represents a significant step towards our goals for our ADRC funded project:
- Improve speech quality to a level comparable to commercial codecs.
- Develop a “rag chew” FreeDV mode with subjective speech quality comparable to SSB at high SNRs.
- Improve low SNR operation such that FreeDV is superior to SSB over poor HF channels.
We are making good progress on all three goals, although it would be useful to perform some formal subjective tests to support the anecdotal reports. There is some work we could do to improve the usability of real world RADE, e.g. reduce PTT turn around delays, improved acquisition, and integration into SDRs.
RADE V1 is an interim step, and we need to keep moving forward. While a neat way to get the mode “on air” quickly – the hybrid Python model is not the end goal, nor is it intended for widespread packaging and distribution. Next step will be a C port of the core RADE encoder/decoder, which will significantly lower the CPU load and bring us one step closer to a more general purpose C library version of RADE, suitable for distribution and integration into SDRs.
The Baseband FM (BBFM) work (see demos from last month) is also moving along nicely. This project is aimed at high quality speech over VHF/UHF radio. This month I have been developing a single carrier PSK modem that can be used over DC coupled or bandpass filtered FM radio channels. This will support an on air experiments of high quality speech using off the shelf FM radios and handsets.