Based on the open source COFDMTV modem developed by Ahmet Inan / aicodix GmbH. Modulations from BPSK to QAM4096 with code rates from 1/4 to 5/6 and payloads from 256 to 6144 bytes per frame. Rates run from about 790 bits per second to over 13 kilobits per second in the same 2400 Hz.

A set of slow modes built for fading HF paths such as 40 and 80 meter NVIS. Five modes from 1150 bps down to 149 bps in either 2400 Hz or a 600 Hz narrow variant.

A non-coherent mode for weak signal propagation and backup links.

░▒▓█ MODE RECOMMENDATIONS

▐ On VHF/UHF FM, use any OFDM mode

▐ On good HF SSB paths, use OFDM at 8PSK 2/3 or below

▐ On fading/weaker HF paths, use ROBUST modes

▐ For very weak signals or as a backup, use MFSK

░▒▓█ MODE TABLES

Bitrate in bps / payload in bytes, by code rate. 2400 Hz bandwidth.

| Modulation | 1/4 | 1/2 | 2/3 | 3/4 | 5/6 |

| ---------- | --: | --: | --: | --: | --: |

| BPSK | 300 / 64 | 700 / 128 | 900 / 171 | 1000 / 192 | 1100 / 213 |

| QPSK | 500 / 64 | 1100 / 128 | 1400 / 171 | 1600 / 192 | 1800 / 213 |

| 8PSK | 1100 / 256 | 2100 / 512 | 2900 / 684 | 3200 / 768 | 3600 / 852 |

| QAM16 | 1000 / 128 | 2100 / 256 | 2900 / 342 | 3200 / 384 | 3600 / 426 |

| QAM64 | 2200 / 512 | 4300 / 1024 | 5700 / 1368 | 6400 / 1536 | 7100 / 1704 |

| QAM256 | 2700 / 512 | 5400 / 1024 | 7300 / 1368 | 8200 / 1536 | 9100 / 1704 |

| QAM1024 | 3700 / 1024 | 7500 / 2048 | 10000 / 2736 | 11200 / 3072 | 12500 / 3408 |

| QAM4096 | 4300 / 1024 | 8600 / 2048 | 11400 / 2736 | 12800 / 3072 | 14200 / 3408 |

| Modulation | 1/4 | 1/2 | 2/3 | 3/4 | 5/6 |

| ---------- | --: | --: | --: | --: | --: |

| BPSK | 400 / 128 | 800 / 256 | 1100 / 342 | 1200 / 384 | 1300 / 426 |

| QPSK | 800 / 256 | 1600 / 512 | 2100 / 684 | 2400 / 768 | 2600 / 852 |

| 8PSK | 1200 / 512 | 2400 / 1024 | 3200 / 1368 | 3600 / 1536 | 4000 / 1704 |

| QAM16 | 1600 / 512 | 3200 / 1024 | 4200 / 1368 | 4700 / 1536 | 5200 / 1704 |

| QAM64 | 2400 / 1024 | 4800 / 2048 | 6400 / 2736 | 7200 / 3072 | 8000 / 3408 |

| QAM256 | 3200 / 1024 | 6300 / 2048 | 8400 / 2736 | 9500 / 3072 | 10500 / 3408 |

| QAM1024 | 4100 / 2048 | 8300 / 4096 | 11000 / 5472 | 12400 / 6144 | 13800 / 6816 |

| QAM4096 | 4800 / 2048 | 9600 / 4096 | 12800 / 5472 | 14400 / 6144 | 16000 / 6816 |

| Modulation | 1/4 | 1/2 | 2/3 | 3/4 | 5/6 |

| ---------- | --: | --: | --: | --: | --: |

| BPSK | 428 / 256 | 856 / 512 | 1144 / 684 | 1285 / 768 | 1425 / 852 |

| QPSK | 856 / 512 | 1713 / 1024 | 2288 / 1368 | 2569 / 1536 | 2850 / 1704 |

| 8PSK | 1275 / 1024 | 2551 / 2048 | 3408 / 2736 | 3826 / 3072 | 4245 / 3408 |

| QAM16 | 1713 / 1024 | 3425 / 2048 | 4576 / 2736 | 5138 / 3072 | 5700 / 3408 |

| QAM64 | 2551 / 2048 | 5101 / 4096 | 6815 / 5472 | 7652 / 6144 | 8489 / 6816 |

| QAM256 | 3425 / 2048 | 6851 / 4096 | 9152 / 5472 | 10276 / 6144 | 11400 / 6816 |

| QAM1024 | - | - | - | - | - |

| QAM4096 | - | - | - | - | - |

| Mode | Bandwidth | Payload | Airtime | Bitrate |

| ---- | --------- | ------: | ------: | ------: |

| RDM-1200 | 2400 Hz | 512 B | 3.6 s | 1150 bps |

| RDM-800 | 2400 Hz | 512 B | 5.2 s | 781 bps |

| RDM-600 | 2400 Hz | 512 B | 7.0 s | 585 bps |

| RDM-300 | 2400 Hz | 512 B | 13.8 s | 296 bps |

| RDMN-300 | 600 Hz | 512 B | 13.8 s | 296 bps |

| RDMN-150 | 600 Hz | 512 B | 27.5 s | 149 bps |

| RDM-1200S | 2400 Hz | 172 B | 1.9 s | 731 bps |

| RDM-800S | 2400 Hz | 172 B | 2.7 s | 513 bps |

| RDM-600S | 2400 Hz | 172 B | 3.6 s | 378 bps |

| RDM-300S | 2400 Hz | 172 B | 7.1 s | 194 bps |

| RDMN-300S | 600 Hz | 172 B | 7.0 s | 196 bps |

| RDMN-150S | 600 Hz | 172 B | 13.9 s | 99 bps |

| Mode | Tones | Bandwidth | Code rate | Payload | Bitrate |

| ---- | ----: | --------- | --------- | ------: | ------: |

| MFSK-8 | 8 | 250 Hz | 1/2 | 19 B | 34 bps |

| MFSK-16 | 16 | 500 Hz | 1/2 | 27 B | 48 bps |

| MFSK-32 | 32 | 1000 Hz | 1/2 | 35 B | 63 bps |

| MFSK-32R | 32 | 1000 Hz | 3/4 | 55 B | 99 bps |

░▒▓█ BUILDING FROM SOURCE

On a system with apt? Run the installer script:

./install.sh

Or build manually:

# Debian/Ubuntu/Pi

sudo apt install git build-essential libncurses-dev g++

git clone https://github.com/RFnexus/modem73

cd modem73

make

# Optional: move to /usr/local/bin

sudo make install

For CM108 USB PTT support, install libhidapi-dev before building. The Makefile will auto-detect it and enable the feature.

░▒▓█ RUNNING

By default, MODEM73 listens for KISS on port 8001 and starts a JSON control port on 8073. See CONTROL_PORT.md for the full spec.

# Start in UI mode

./modem73

# Start in headless mode

./modem73 --headless

# See all options

./modem73 --help

There are five PTT options: NONE (speaker/mic over the air), rigctl, VOX, serial, and CM108.

# rigctl, while rigctld is running

./modem73 --rigctl localhost:4532

# VOX with 500ms lead and 150ms tail

./modem73 --ptt vox --vox-freq 1200 --vox-lead 500 --vox-tail 150

# Serial

./modem73 --ptt com --com-port /dev/ttyUSB0 --com-line rts

# CM108 USB audio interface (GPIO3 is the default)

./modem73 --ptt cm108 --cm108-gpio 3

modem73 supports the All In One Cable out of the box. Set PTT to COM, specify your COM port, set PTT line to BOTH and Invert to INVERT RTS. The AIOC usually shows up as /dev/ttyACMx and may change after a restart or replug.

Since you're reading this over Reticulum, this one's for you. Grab the modem73interface, drop it into ~/.reticulum/interfaces/, and add this to your Reticulum config:

[[MODEM73]]

type = Modem73Interface

enabled = yes

target_host = 127.0.0.1

target_port = 8001

control_host = 127.0.0.1

control_port = 8073

Interface source: https://github.com/RFnexus/modem73interface

modem73 includes an update utility. To update to the latest version:

./update.sh