Amateur Radio homebrew: Raspberry Pi + Packet Radio + social networking integration

I’m putting something together for our River City Amateur Radio Comms Society homebrew show n tell later this year. Here’s my ingredients so far:

I’m thinking of building a bridge between Amateur Radio Packet and social networking, like Twitter.

So far I’ve roughed out node.js to Twitter integration using node-oauth, and I I’ve put together a simple prototype using the node-ax25 library to connect to the KISS virtual TNC on Direwolf. It receives packets and writes callsigns and messages to the console.

Right now I’m testing this on a PC running Debian, with a Rigblaster Plug n Play connected to an Icom 880h. Later when my TNC-Pi arrives I’ll migrate this to the Pi.

So far using the node-ax25 library looks pretty easy. Here’s some code so far to dump received callsigns to the console:

var ax25 = require("ax25");

var tnc = new ax25.kissTNC(
    {   serialPort : "/dev/pts/1",
        baudRate : 9600
    }
);

tnc.on("frame",
    function(frame) {
        //console.log("Received AX.25 frame: " + frame);
        var packet = new ax25.Packet({ 'frame' : frame });
        console.log(new Date() + "From "
            + formatCallsign(packet.sourceCallsign, packet.sourceSSID)
            + " to "
            + formatCallsign(packet.destinationCallsign, packet.destinationSSID));

        if(packet.infoString !=""){
            console.log(">  " + packet.infoString);
        }
    }
);

/**
 * Formats a callsign optionally including the ssid if present
 */
function formatCallsign(callsign, ssid){
    var formattedCallsign = "";
    if(ssid == "" || ssid == "0"){
         formattedCallsign = callsign;
    }
    else{
        formattedCallsign = callsign + "-" + ssid;
    }

   return formattedCallsign;
}

The output for  received messages so far looks like this:

Wed Apr 19 2017 23:10:00 GMT-0700 (PDT)From KBERR  to KJ6NKR

Wed Apr 19 2017 23:12:05 GMT-0700 (PDT)From AE6OR  to BEACON

>  Š¤¤@à–¤ˆŽ@@`–„Š¤¤@`®žžˆ²@`–„Š¨@`¨‚žŠ@aðHello from 5W Garage packet node AUBURN 73's Steli !

Wed Apr 19 2017 23:12:08 GMT-0700 (PDT)From AE6OR  to BEACON

>  Š¤¤@à–¤ˆŽ@@à–„Š¤¤@ஞžˆ²@`–„Š¨@`¨‚žŠ@aðHello from 5W Garage packet node AUBURN 73's Steli !

Wed Apr 19 2017 23:16:49 GMT-0700 (PDT)From K6JAC -6 to ID    

>  K6JAC-6/R BBOX/B KBERR/N

Wed Apr 19 2017 23:19:31 GMT-0700 (PDT)From K6WLS -4 to ID    

>  Network Node (KWDLD)

Wed Apr 19 2017 23:19:50 GMT-0700 (PDT)From NM3S   to BEACON

>  Mike in South Sac.  Please feel free to leave a message. 73's

Packet Radio: Checking in to the Central California Sunday Packet Net using Linpac and Direwolf

I didn’t think it was year ago that I last checked to the Central California Packet Sunday night net, but looking for notes on how to send packet unproto frames from Linpac, this post was today exactly last year. Apparently January 15th is my favorite day for doing some packet radio.

This is using ax25, Direwolf and Linpac setup on Debian that I posted about a few days back. I did a screen recording of the net checkins so you can see what a packet net looks like. It’s not exactly fast paced, and in the middle there’s some WinLink email inbox checking going on, but you can see Ben KG6BNL running Net Control, and then check-ins that follow.

In the screencapture I’m ssh’d from my Mac into my desktop upstairs which has a Rigblaster Plug n Play connected to my Icom 880h. The top session is Direwolf, so you can see it’s decoding all the packets it hears. The bottom session is Linpac, where I’m using :unproto to send my check-in.

Capturing the KISS pseudo terminal /dev/pts/x value from Direwolf

If you startup Direwolf with a KISS pseudo terminal for connecting another KISS packet app through Direwolf, you probably also need to run kissattach and mkiss to attach to the pseudo terminal. You can do this manually, but after doing this a few times, I put together this script to grep for the returned /dev/pts/x and then execute the kissattach with this value:

Tuning Direwolf packet parameters for use with HT radios

Direwolf has a  number of tuneable properties – by default after installing and configuring the basics, your callsign etc, it normally ‘just works’. I’ve been experimenting setting up Direwolf and PiLinBPQ as a BBS on a Raspberry Pi, and using axcall or LinPac on another Pi with Direwolf to call into the BBS. I have a Rigblaster and Yaesu FT60 HT on one Pi, and a SignaLink and Wouxun HT on the other radio.

The problem I ran into was that either Pi seems to work ok to call into a Packet node nearby, but calling from one Pi to the other was pretty unreliable in terms of not decoding packets, and the number of retries before a packet would get received and decoded. I tried a number of options, and feedback in the Yahoo Groups Direwolf group give me some suggestions to try. The tuning parameters are all covered in the excellent Direwolf docs.

Possible problems with using HTs for packet could include a combination of these factors:

  • Receive audio too loud into Direwolf (aim for around 50)
  • Receive audio not loud enough – adjust soundcard volume (Rigblaster/Signalink) and alsamixer levels
  • The radio doesn’t transition quick enough between transmit and receive (can be fixed by adding DWAIT)
  • Latency from the soundcard audio either in receive or transmit – can be fixed by adding TXDELAY for delay at the start of the transmission, and/or TXTAIL for a delay at the end

The settings I finally wound up with on both Pis that worked for me are:

DWAIT 20

TXDELAY 60

TXTAIL 60