Introduction - Using Multipsk Software as a TNC for JNOS

Using a soundcard in place of a hardware modem or tnc is an option that has gained alot of interest over the past few years. There are some good programs out there that let you use a soundcard for lots of different digital modes. One such program is Multipsk - written by Patrick, F6CTE. If you want some more general information on this program, click here. What is cool about Patrick's program is that it has a built-in tcp/ip server, allowing outside applications to connect to Multipsk, and use it as a digital modem.

JNOS can now be added to the list of programs that are able to directly connect to Multipsk and use it as an AX25 (packet) modem. Patrick recently added the ability to send KISS frames over the tcp/ip server. My plans for using Multipsk do not stop at packet. I have other ideas and modes that I want to use, but for now the prototype is limited to AX25 (packet) only - and on LINUX versions of JNOS only - DOS version will come later.

Downloading Multipsk Software

You must use Multipsk (version 4.13) - earlier versions do not support KISS over tcp/ip server.

Click here to download.

Downloading JNOS Software

If you can't compile your own version, here is a gzipped binary from my development system.
* It might work on your linux, it might not. Only other choice (for now) is the patch below ...

The Multipsk interface is available only as a patch right now. Only apply this patch to JNOS 2.0f or higher. The patch will get put into an official release in the near future. You can download the patch from the following link :

Put the tar file in your JNOS source directory, extract using 'tar xvf mpsk.tar', then make sure '-DMULTIPSK' is defined in your makefile or '#define MULTIPSK' in your config.h, then enter the 'make' command to compile.

*** CORRECTION *** I should have included a makefile in the patch. The compile will fail when it tries to link in the mpsk_attach() function. BUT, you can fix this by adding 'multipsk.o' to the end of the 'NET=' section of your existing makefile. Sorry, if this has caused any inconvenience.

Example Setup

JNOS will run on a linux host machine. Multipsk will run on a Windows machine. Both machines will be connected to the network (LAN). Before you run Multipsk, you have to make sure that the Windows machine has a route back to JNOS. Remember that JNOS is not directly on the LAN, it is reachable VIA the linux host machine. For illustration purposes, let's say the IP address of JNOS (the tun interface) is, the linux host machine is, and the Windows PC is Then on the Windows PC, enter the following command :

   route add

Try to ping the JNOS system, make sure you can :


Note : IP forwarding must be enable on the linux host machine for this to work.

What to do on the JNOS side

All you have to do is run the following command (or put it in your autoexec.nos) :

   attach multipsk psk 3122

JNOS will try to connect to Multipsk once a minute - watch the JNOS log for this.

Once connected, the new 'psk' port is just like any other AX25 port in JNOS.

Running Multipsk


- After starting the "Multipsk.EXE" file, you will find the "Configuration

- Click on the "TCP/IP server "On"" button to start automatically the TCP/IP

- Click on big button "RX/TX screen" to start the decoder (and authorize the
TCP/IP connection required by Windows),

- It is strongly recommended to calibrate the sound-card: click on the
"Adjustments" menu button, then select the "Determination of the RX/TX
sound-card sampling frequencies" option and push on the "Determination of
the 48 KHz RX sampling frequency (test on 3 minutes)" button. At the end of
the test, click on "Return",

- Click on the "PACKET+APRS" orange button,

- To use the TCP/IP possibility, click in the "Options" button which opens
the window "Packet parameters", then push the "KISS through TCP/IP" button
located in the "Miscellaneous" box. Click on "OK".

- Push the "KISS" button. That's all for Multipsk.

Note about the sound level ("Level" indication in % at the top of the
screen): an AF level superior or equal to 10 % is OK. About 50 % is ideal
(but not critical). In case of very low AF level, select "16 bits" in the
"Determination of the RX/TX sound-card sampling frequencies" option
("Adjustments" menu button),

About the help in Multipsk:

- To bring up the text help (contextual sensitive one), click on the right
button of the mouse, with the cursor over the mode button "KISS", for

- Also use the button hints (wait a fraction of second over a button).

Closing comments

This is a first release (prototype) - expect bugs. The more people test this, the better it will get.

Please report any problems. Have fun.

March 19, 2009 - multipsk (4.13) replaces test version
March 4, 2009 - test version of multipsk available

73 de Maiko Langelaar, VE4KLM