Setting up HF APRS iGate

After several years of running APRS igate on VHF band, last Sunday I went to try setting up APRS igate on HF band.

The frequency would be on 7.036 MHz LSB.

Here is the picture of my iGate, on the top an Alinco DR-135 using external OT2 tracker for 1200 VHF APRS, and underneath it an Icom IC-706 for HF APRS. On the lower rack the laptop running APRX on Ubuntu Linux:


Step 1 – Hardware Setup
The radio would be an Icom IC-706 that I plug the headphone out to the mic in of my MSi U100 netbook running Ubuntu Linux .

Step 2 – SoundModem Installation
The soundmodem tool is usually already installed on typical Ubuntu machine, if it is not then do the following:

sudo apt-get install soundmodem

Step 3 – SoundModem setup
The setup procedure, using soundmodemconfig, is very easy as it is windows based, but as my linux-based iGate is a remote box with no local screen, I have to redirect the Xwindow screen back to my desktop.

Here is the site that explains the procedure to remote configure the soundmodem.

And here is the site with generic information on soundmodem.

The following is my soundmodem setup:
– Driver: alsa
– Board: plughw0,0
– Modulator: afsk, 300 bps
– Demodulator: afsk, 300 bps
– IO: /dev/soundmodem0

Step 4 – Testing
First we have to launch the program with verbose level 5 to see incoming packets:

sudo soundmodem –v5

Make sure the line shows sample rate of 11025, not 5000.
If showing 5000 then you have the unpatched soundmodem:


Step 5 – Patch the program
It took me 2 nights to figure out as it won’t decode incoming 300 bps packets, and also the transmitted packets did not sound right.

Here is the site that explains the problem and link to the patch.

You have to download the source code from here, patch it, and compile yourself.

During the ./configure step, you probably need to install:
– libxml-dev
– libgtk2-dev
– libaudiofile-dev

Here is a good working soundmodem decoding 300 bps packets:

Step 6 – Incorporate to APRX
Edit /etc/aprx.conf and add one more Interface, with a callsign line using different callsign

Step 7 – Restart APRX
You have to restart APRX to have the packets from HF delivered to the APRS-IS.
Then check on to confirm that HF packets are recorded

Project completed.




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