packetradio-guide/docs/modems/ninotnc.md

NinoTNC

The NinoTNC is a modern hardware modem that can come in either kit form or assembled. It connects to a computer by USB, and to a radio by a cable that is usually custom built buy the operator.

It supports traditional 300, 1200 and 9600 baud packet modes as well as some more modern experimental modes designed to be more efficient that also include forward error correction. The NinoTNC has become an integral part of many new packet radio deployments in the UK and further afield.

Buying one

Information is available on the TARPN Website Ordering Page.

For the UK & Ireland, boards are are available from Tom, M0LTE.

Build

The build gide for the NinoTNC is available on the TARPN Website.

Operation

The Through Hole NinoTNC has 2 banks of switches: Mode and Signals, explanation below.

USB is always 57600 baud

Mode Switch

Current modes as of firmware release 3.3.1:

Mode	Baud	bps	Mod	Protocol	Intended mode	BW	Typical use
0010	9600	9600	GFSK	IL2P+CRC	FM	25k	Current recommended mode for new 70cm (25kHz) links where both ends are compatible
0100	4800	4800	GFSK	IL2P+CRC	FM	12.5k	Current recommended mode for new 2m (12.5kHz) links where both ends are compatible
0101	2400	2400	DPSK	IL2P	FM	12.5k	For situations where only a speaker/mic connection is available but > 1200 baud is desired
1011	1200	2400	QPSK	IL2P+CRC	SSB/FM	2.4kHz	HF - quadrature version of 1200 BPSK, twice the throughput for +3dB SNR.
1010	1200	1200	BPSK	IL2P+CRC	SSB/FM	2.4kHz	HF - use for circuits where wider transmission is acceptable.
1001	300	600	QPSK	IL2P+CRC	SSB	500Hz	HF - quadrature version of 300 BPSK, twice the throughput for +3dB SNR
1000	300	300	BPSK	IL2P+CRC	SSB	500Hz	HF - slowest but best performing mode. ~7dB better than classic 300 baud FSK AX.25
1110	300	300	AFSK	IL2P+CRC	SSB	500Hz	CRC improvement of IL2P 300 baud AX.25. Recommended if you can't do BPSK / QPSK on HF.

Superseded (but still supported) modes:

Mode	Baud	bps	Mod	Protocol	Superseded By	Intended mode	BW	Typical use
0000	9600	9600	GFSK	AX.25	9600 GFSK IL2P	FM	25k	Backwards compatibility with legacy G3RUH modems
0001	9600	9600	GFSK	IL2P	9600 GFSK IL2P+CRC	FM	25k	Backwards compatibility. Obsoleted by 9600 GFSK IL2P+CRC
0011	4800	4800	GFSK	IL2P	4800 GFSK IL2P+CRC	FM	12.5k	Debugging against 4800 GFSK IL2P+CRC in case of issues with the CRC mode
1111	1200	1200	BPSK	IL2P	1200 BPSK IL2P+CRC	SSB/FM	2.4kHz	Backwards compatibility
0111	1200	1200	AFSK	IL2P	4800 GFSK IL2P+CRC	FM	12.5k	Improvement over 1200 AFSK IL2P, where none of the GFSK modes are possible
0110	1200	1200	AFSK	AX.25	1200 AFSK IL2P	FM	12.5k	VHF APRS, backwards compatibility with classic / legacy TNCs like PK232
1100	300	300	AFSK	AX.25	300 AFSK IL2P	SSB	500Hz	Backwards compatibility with legacy HF packet modems. Modulation invented c. 1962!
1101	300	300	AFSK	IL2P	300 AFSK IL2P+CRC	SSB	500Hz	IL2P improvement of AFSK 300 baud AX.25.

Prefer:

• QPSK > BPSK > DPSK > AFSK
• IL2P+CRC > IL2P > IL2P > AX.25
• SSB > FM

Signals Switch

Switch 1 - Transmit audio range selection - DATA/MIC

The data / on / up position increases the TXA level so the TX-LEVEL potentiometer adjustment is in the range needed by the Data radio.

The mic / off / down position reduces transmit audio to the range needed by a microphone-level-input radio.

Switch 2 - Receive audio sensitivity - 1x/11x

The on / up / 1x position is about the right level for a speaker output, and is also appropriate for a data radio output.

The off / down / 11x position is used for radios which have a very low level of receive audio, e.g. perhaps when taken from a speaker mic connection.

Switch 3 - Transmit audio coupling control - DC/AC

Leave in the off / down / AC position unless you have a rare case where having the voltage into the modulator track the TNC’s output, exactly, is required (DC coupling).

Switch 4 - External carrier detect - EN/CD

Leave in the off / down / CD position unless you want to provide external transmit inhibit using pin 2 of the DB9 connector.