9.1 KiB
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 guide 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Superseded (but still supported) modes:
| Mode | Baud | bps | Mod | Protocol | Superseded By | Intended mode | BW | Typical use |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. |
Our order of preference for modes at UKPR are:
- QPSK > BPSK > DPSK > AFSK
- IL2P+CRC > IL2P > IL2P > AX.25
- SSB > FM
Why? Simply put, see the below three statements but tread carefully. Not all things are equal, and not all rigs are capable of 'optimum' performance. Perfection is the enemy of good enough, so please endeavour to get something working, not something perfect.
Modulation: These modes offer increasing bandwidth efficiency, with QPSK being our over SSB being our preferred - AFSK over FM is the least efficient mode.
Protocol: IL2P+CRC is the most resilient mode against corruption or data loss as it transits the air, with AX.25 being unprotected against this.
Mode: SSB is preferred as the channels are narrower and allow for more flexibility - tighter filtering and better amplification per hz. FM is good enough, however.
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.
Debugging Strategies
Link not working as well as you want? Can your friends not hear you? Can you not hear them? Let's take it back to basics and see if we can find the problem.
Let's strip the complete system back. Make sure that BPQ or other node software is stopped - it's going to want to take over the modem and that'll get in the way. This will be easiest if you can connect to your TNC with a client such as QtTermTCP that offers both monitor and interactive panes. If you're running the linux stack, you can run sudo axlisten -ac to see the data decoded by your modem.
No Received Signal
Not seeing anything in the monitor? We need to think about two things here: Is the modem receiving signals from the radio, and is the computer receiving signals from the modem. Let's eliminate each issue one step at a time.
Radio -> Modem Fault
First off, check the radio and check the cable. Check if the radio is set up for outputting audio through the accessory socket you're using, and it's in the correct mode (1200bd vs 9600bd - check your manual). A good test here is can you hear the signal you want to decode? If you can hear it, we need to find out why your modem can't. As the faster modes sound quite close to white noise, this doesn't always hold true, but it's a least a starter. Perhaps combine eyes and ears and watch the S-meter too!
I often confuse the 9600bd and 1200bd lines on my interface cable - have a look to see if you've done the same. More often than not, this has melted my head during cable construction, or I'm using the cable for my UHF Radio on my HF Radio.
Next up: is your modem in the right mode? Look online at either the node's website or UKPRN Website for hints and clues or ask questions of your peers - we're here to help.
Finally - is your radio outputting enough audio? Is it too much audio? Look at the LEDs on your NinoTNC. Here is a guideline of how to read them:
Modem -> Computer Fault
Is your modem decoding a signal?
You can tell by the RX DCD / Green LED lighting when a packet is successfully received & decoded.
It's being powered, and that's presumably from the computer USB port, but maybe it's not connected properly.
Check if it is a serial device: run ls /dev | grep ttyACM, unplug the modem and run the command again. If there's a difference, when you plug it back in and rerun the command (for a third time, yes!) you should see a new device appear, and appear similar to below:
hibby@GB7HIB:~ $ ls /dev | grep ttyACM
ttyACM0
We've now identified your modem's device and we know it is appearing on your computer. If it isn't, check you are in the 'dialout' group by opening a terminal and running groups on the command line. If it doesn't say dialout in the output, follow this advice and log out/in. If the above doesn't work, try a new USB cable.
An alternative command to look at running before and after disconnect is sudo dmesg - this should tell you if Linux has detected your device disappearing and reappearing.