PMON - a PACTOR® Monitoring Utility for Linux

PMON allows the thorough observation and documentation of all presently available PACTOR-1/2/3 transmissions (PACTOR-4 will follow in early 2020). PMON covers all PACTOR levels with the appropriate Speedlevels and packet variations. PMON will read in parallel PACTOR-2 and PACTOR-1. The very wide receiving range (frequency offset ±200 Hz), as well as the automatic sideband recognition, ease routine operation of PMON with PACTOR-2 and PACTOR-3 considerably.

PMON automatically decompresses LZHUF compressed messages on the fly. This is very useful for monitoring Winlink email transfers.

Note: LZHUF compression is not inherent to PACTOR, it is not the internal PACTOR Huffman/PMC compression but an external compression variant utilized by some application software, e.g. Winlink. Nevertheless, as LZHUF is widely used, PMON supports decompression even of that third party compression type.

This tool is strictly for private use only! This means non-commercial applications, by private persons, e.g. radio amateurs. The monitored data may be published without restriction by those users - if not prohibited by law!


To use PMON you need at least a Raspberry Pi 3 Model B+ and an appropriate (capturing) sound device.

We have tested PMON thoroughly with

If you own a modern radio with built in USB audio capabilities like for example the ICOM IC-7300, this should work too.

We recommend to use high quality hardware. The better the equipment the better the results!

As operating system for the Raspberry Pi we recommend the current Raspbian Lite but the other versions of Raspbian should work too (not tested).

The PMON Primer

In case you are not familiar with Linux and the Raspberry Pi, hopefully you will find our PMON Primer helpful.

Installing on a Raspberry Pi (Raspbian)

You have the choice of three different installation methods:

  • One-step automated installation using our APT repository
  • Manually add our APT repository and install PMON
  • Complete manual installation

Use only one method!

We recommend method 1, the one-step automated installation.

APT Repository

The advantage of using the SCS APT repository is that you can easily update PMON if a new version is available with the well known commands:

sudo apt update

sudo apt upgrade

One-Step Automated Installation

wget -qO - 

wget -qO - | bash

Downloading from the Internet and piping directly to bash is a bit controversial. But you can easily check the script by entering the URL into your favorite browser. The script consists only of a few lines and is well commented.

Alternative Installation

Add the repository to your system:

(this is one line!)

echo "deb 

echo "deb buster non-free" | sudo tee /etc/apt/sources.list.d/scs.list > /dev/null

Then add our gpg key. This allows you to install signed packages:

wget -q -O - 

wget -q -O - | sudo apt-key add -

Now update your APT repositories and install PMON:

sudo apt update

sudo apt install pmon

Manual Installation


sudo dpkg -i pmon_1.0_armhf.deb


Uninstalling PMON is pretty straight forward. If you installed PMON via our APT repository do

sudo apt purge pmon

If you did the manual installation enter

sudo dpkg -P pmon

First Steps

Please read the license!

pmon --license

Please read the manual

man pmon

After reading all the material, the real first step is to check the audio devices available on your system

pmon -a ?

You will get a list like this (maybe not with that much devices)

List of available sound devices capable of capturing audio:

hw:0,0 - sndrpihifiberry [snd_rpi_hifiberry_dacplusadc], HiFiBerry DAC+ADC HiFi multicodec-0 []

hw:1,0 - Set [C-Media USB Headphone Set], USB Audio [USB Audio]

hw:2,0 - CODEC [USB AUDIO CODEC], USB Audio [USB Audio]

In this setup there are 3 audio devices:

hw:0,0 is the HiFiBerry DAC+ ADC

hw:1,0 is a cheap USB sound dongle

hw:2,0 is the microHAM USB Interface III

Let‘s say you like to use the HiFiBerry DAC+ ADC to capture PACTOR traffic

pmon -a hw:0,0

To connect the audio device to your radio you need an appropriate cable. If the audio device has stereo input, we use only the left channel. This is normally the tip of the audio jack.

Or you can simply provide the audio signal on both channels (tip and ring) of the audio jack.


Spezielle Communications Systeme GmbH & Co. KG

Roentgenstr. 36

D-63454 Hanau, GERMANY