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  M17 weekly net
Posted by: N2XDD - 03-18-2021, 11:23 PM - Forum: General discussion - No Replies

The m17 weekly net meets fridays at 1700 hrs UTC on the m17 reflector module  C  or the TGIF DMR network talkgroup 1017. 
 Please try and join us.

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  M17 Scheduled QSO
Posted by: nizzo - 03-05-2021, 09:40 AM - Forum: General discussion - Replies (2)

Hi everybody,

it would be nice to program a scheduled QSO, maybe bi-weekly, to talk about M17, via M17.

We could begin this Friday 5 March at 8pm UTC.

I know we are an international community so feel free to suggest an alternative time which is more comfortable for western timezones.

73 de IU2KIN

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  TX Bar
Posted by: N2GYN - 02-24-2021, 06:15 PM - Forum: Technical - Replies (3)

Please.... For the love of God, add a lock button for TX!! You can add a timeout timer so no one keeps it keyed by accident. Also make the TX bar bigger. My finger is getting fatigued. I want to free up my hands for other things.

Thanks,
John 73

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  How to turn an old Motorola GM300 into M17 transceiver
Posted by: SP5WWP - 02-21-2021, 01:23 PM - Forum: Technical - Replies (4)

TL;DR: it is possible to turn GM300 radios into complete M17 transceivers. See the "New setup" section below for a tentative guide on how to accomplish this.

TEST SETUP: My setup is very simple. A Raspberry Pi 3B is basically playing back a .raw file containing the M17 baseband. The .raw was generated with m17-mod tool. See the code below for details. Output from the soundcard is applied (through a 1k potentiometer) to pin 5 of the connector at the back (accessory connector). The REF trim pot in the radio is set fully clockwise, allowing the signal to pass through. The VCO_MOD pot is set to about 90% of its range (more details later). PTT is keyed by asserting low voltage level at pin 3 (pin 7 is GND, just connect them both).

[Image: gmacc8.gif]

Code:
#generate the baseband from a wave file (8000Hz sample rate, mono, signed 16 bit, little endian)
sox sample.wav -t raw - | m17-mod -S SP5WWP > m17_baseband.out

#the baseband signal is sampled at 48000Hz
#play it back with the external USB soundcard
cat m17_baseband.out | aplay -D plughw:1,0 -c 1 -r 48000 -f S16_LE

Update: Encoding signal from the microphone input is possible, use this script.

NEW SETUP:
A USB soundcard and RPi >=3 is needed. My soundcard is based on a C-media HS-100B chip, they are very cheap.
GM300 modifications needed: JU551 in A position, REF pot set to 100%, VCO pot set to about 90% (set them both to get a flat baseband response, use Gqrx's audio FFT plot), cut pin 4 of TDA1519 open (to be able to inject AF from our own amplifier).
TX: Connect microphone or apply any other equivalent signal source to the mic input (thru a pot if needed). Run the PTT python script. Set the pot so that the reported deviation is 1.0 (use rtl_fm, see this for details). Output from the line out should go to pin 5 of the accessory connector; again: thru a pot... Smile No dc-blocking cap needed.
RX: Connect pin 11 to the mic input (via a pot). Run the command below:
Code:
arecord -D plughw:1,0 -c 1 -r 48000 -f S16_LE | sox -t raw -e signed-integer -c 1 -b 16 -L -r 48000 - -t raw - vol -1 | m17-demod -d | aplay -D plughw:1,0 -c 1 -r 8000 -f S16_LE

Amplify the line out signal using LM386 or something similar and feed it to pin 16 (tie pin 1 to GND).

Note:
The "RX audio" output (pin 11) looked clipped. I had to bypass 390k R552 resistor with a 100k one (THT resistor in the center of the image below). See page 37 of the attached document (GM300 schematic). Alternative link.
[Image: aGfdlre.png]

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  M17 Voice Using Mobilinkd TNCs
Posted by: WX9O - 01-29-2021, 02:50 AM - Forum: Technical - No Replies

M17 Voice OTA (over the air) is now possible using the Mobilinkd M17 KISS HT Android app (forked from Codec2Talkie), either a Mobilinkd TNC3 or Mobilinkd NucleoTNC, and a 9600-baud capable radio (requires direct access to the discriminator and modulator).  They has been tested with a Kenwood TM-V71A and  Kenwood TK-790.

The TX chain is Android App -> TNC -> Radio.

The RX chain is Radio -> TNC -> Android App.

The radio handles FM modulation/demodulation.

There is a physical connection between the radio and the TNC/Modem.

The TNC handles M17 baseband physical layer and data link layer encoding and decoding. This includes 4-FSK modulation/demodulation, sync word recognition, framing, convolutional encoding/decoding, Golay encoding, LICH assembly (if needed) and Link Setup Frame validation.

The TNC communicates with the Android app via KISS streaming protocol.  Currently USB Serial and BLE are supported transports.

The Android app is responsible for the UI, constructing or decoding the Link Setup Frame, audio input/output, and Codec2 encoding.  It currently only supports Codec2 3200bps mode.

The Android app can be found here: https://github.com/mobilinkd/m17-kiss-ht/releases
The NucleoTNC firmware can be found here: https://github.com/mobilinkd/NucleoTNC/releases
The TNC3 firmare can be found here: https://github.com/mobilinkd/tnc3-firmware/releases
Currently, the only config app that can be used to configure the NucleoTNC or TNC for M17 is the Python config app: https://github.com/mobilinkd/tnc1-python-config

Make no mistake, the firmware is highly speculative right now, designed to provide a working M17 voice implementation for M17 developers and experimenters.

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  Hurdles of mating M17 with MD380
Posted by: SP5WWP - 01-28-2021, 10:08 AM - Forum: Technical - Replies (1)

We have been trying to check if M17 can be implemented on MD380-class radios. Many thanks to the OpenRTX team for helping us with that one.

Let me list all unsolved mysteries and some other problems.
- There's no microphone audio signal present at the microcontroller (ADC)
- PC8 pin, that's probably configured as a PWM, is lowpassed and fed into speaker amp - is that enough to get speech out?
- 2-point modulation is done by the HR_C5000 chip. We can only try and set offsets at both outputs by writing to specific registers. That in turn allows us to swing MOD1 and MOD2 only by about 850 mV. Is that enough to get M17 RF out?
- How to get demodulated data?

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  New mrefd release 0.3.6
Posted by: n7tae - 01-19-2021, 08:37 PM - Forum: Reflectors - No Replies

This is a non-essential release and is more efficient at validating incoming packets. It will save cpu cycles and the savings will be directly proportional to the amount of traffic your reflector handles.

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  Packet Mode Questions
Posted by: akbat - 01-17-2021, 03:54 AM - Forum: Technical - Replies (7)

The section of the specification documentation on packet-mode say puncturing uses a 7/8 matrix (1, 1, 1, 1, 1, 1, 1, 0) but the Physical Layer section discusses 2 different puncturing matrices that are much longer. (P1 for the LSF and P2 for all other frames) Which is actually used for packet-mode frames? I assume a packet-mode LSF uses P1 as described.

The specs also say a packet-mode super-frame has 798 bytes of payload, but I can't figure out how regular frames fit into this evenly or if subsequent frames include LICH chunks like with stream-mode.

Finally, I gather that LICH refers to the data in the LSF, but what does LICH actually stand for?

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  Hello KC1AWV
Posted by: HB9TVW - 01-05-2021, 08:42 AM - Forum: Reflectors - Replies (1)

Hello KC1AWV

Can you Please add this Reflector Name M17-CHI Reflector


url:  [url=https://m17-lom.myddns.me:24033/][/url]m17ch-italia.ddns.net/m17/
iPv4: 212.237.33.114/m17
IP6: none
Sponsor: HB9CSR Basel Group
The country: Switzerland

Sysop: HB9TVW

Thank you, 73s

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  M17 Reflectors Beta
Posted by: KC1AWV - 01-01-2021, 11:42 PM - Forum: Reflectors - Replies (3)

The M17 Reflectors Beta is now open to the public!

https://reflectors.m17.link

Please register your reflectors there. Requests placed in the forums will no longer be processed.

Thank you, and Happy New Year!

Steve KC1AWV

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