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FAQ

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Wojciech Kaczmarski edited this page Oct 4, 2019 · 1 revision

FAQ (EN)
1. What's M17?

  • It's a truly open, free to use digital radio system. All schematics and source code is available for free at my GIT page.

2. How long have you been workikng on it?

  • For about 1 year.

3. Why M17?

  • Mainly because there's no open platform for developing digital radio. Also, the DMR system, although the standard by ETSI is open, isn't really amateur-friendly. You can't really experiment with it. M17 provides all that DMR misses and adds better voice quality to that.

4. What are the disadvantages of M17 as compared to DMR?

  • M17 uses Frequency Division Multiple Access (FDMA) instead of Time Division Multiple Access (TDMA), which doesn't allow two simultaneous links to be established on one channel.

5. What's the vocoder you use?

  • It's Codec2 by David Rowe. It outperforms codec used in DMR.

6. Why not just implement Codec2 into existing DMR standard?

  • As it was said before: there are no open platforms for experimenting with DMR. It's no fun using something, that's only available at commercial retail. Is that true ham spirit?

7. What is the coded speech bitrate?

  • 3200 bits per second.

8. Does the M17 support any encryption?

  • Not right now, but I am working on AES implementation.

9. How do you identificate users?

  • IDs work the same as in the DMR system.

10. Can I use M17 on my DMR radio?

  • Most likely - no.

11. Can I send data with M17?

  • Yes, it is possible to send data packets alone or as embedded data along with voice channel.

12. Can I link M17 with my DMR repeater?

  • Why not? :)

13. What are the radio internals?

  • Theres an STM32F7 family microcontroller along with a SiLabs Si4463 RF front-end chip. Of course there is more to that - an RF power amplifier and so on. There is even an accelerometer (ADXL345) and a place for a GNSS module.

14. Can I send APRS frames with it?

  • Likely, yes, since the codec is based on sinusoidal coding principle. But why doing that, if you can send data with... FSK instead of a bunch of beeps? Wy use APRS if there's no error correction at all?

15. Is M17 compatible with DMR?

  • Nope.

16. Can your radio be switched to use DMR instead of M17?

  • Nope.
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