Quick start guide for UltraMSK

This section contains information and instructions for setting up an UltraMSK receiver system.

There are many possible configurations for a working system. So please feel free to contact us to discuss your requirements.

13 Feb 2019


A typical UltraMSK hardware setup will consist of 1, a VLF antenna and preamplfier, and 2, a power supply for the preamplifier and a GPS receiver with a 1PPS signal output. A computer & sound card is needed to run the UltraMSK software.

Installing Linux

CentOS UltraMSK runs on the Linux operating system. Install Linux on your computer. The CentOS distribution is recommended.

Sound card connections

Once you have your PC setup and running CentOS, the next task is to setup the inputs to the soundcard. Typically, the GPS 1PPS signal connects to the first input channel and the VLF signals can be connected to the second and subsequent input channels of the computer sound card.

It is important that the GPS 1PPS signal does not overload the soundcard input. The ideal level for the 1PPS pulse is around 50 % of the full scale input level. You may need to attenuate the 1PPS signal and isolate the VLF signal for best results.

Signal check

Once you have the GPS 1PPS and VLF signals connected to the sound card, use a sound recorder such as Audacity to check the connections and signal quality are OK. The 1PPS pulse height needs to be around 50 % of the full scale range.

Software installation

Download the latest build of the ultramsk software from here

A license is required to run the software. A free evaluation license is available. Please contact us to discuss your requirements.

UltraMSK options

Running msk as shown below will display a list of command line options.

[james@orchid tmp]$ tar -zxvf UltraMSK-1.1.5.tar.gz 

[james@orchid tmp]$ cd UltraMSK-1.1.5/
[james@orchid UltraMSK-1.1.5]$ ./msk
UltraMSK. Version 1.1.5. Build Nov 30 2018.
Copyright 2005-2018 UltraMSK.com (info@ultramsk.com)
Receiver options:
-f [frequency]	: set receiver Frequency (Hz)
-b [baud rate]	: set MSK baud rate. Use 0 for CW. (default = 200 Hz)
-c [call sign]	: set station Call sign (default = MSK)
-r [resolution]	: set output Resolution (default = 1.0 seconds)
-o [directory]	: set data file Output directory (default = .)
-g [gain]	: set 1 PPS signal Gain (default = 1.0)

Audio sampling options:
-p [input]	: set input channel for 1 PPS signal (default = 1)
-s [input]	: set input channel for VLF Signal (default = 2)
-D [device]	: enable ALSA sampling using specified device
-F [sample rate]: set ALSA sampling rate (default = 96000 Hz)
-V [buffer]	: enable vlfrx-tools sampling

Output options:
-d 		: enable status output
-l 		: enable combined polar output (dB, degrees)
-m 		: output messages to a log file
-i 		: enable binary file format output
-h [site name]	: specify the site name to appear in the output file
-L [file prefix]	: output one minute summary file

Wideband output options (licensed feature):
-W [resolution/s]	: enable wideband power spectrum output
-U [frequency/Hz]	: set wideband power spectrum upper output frequency
-X [file prefix]	: set wideband output file prefix (default = UWB)

Advanced options:
-t [time/ms]	: set 1 PPS window (default = 0.950 ms)
-B [time/s]	: set sampling buffer length (default = 1 s)
-R 		: Enable real-time scheduling
[james@orchid UltraMSK-1.1.5]$

The main UltraMSK command line options are -f, -b, -c and -r:

sets the receiver centre frequency in Hertz eg. -f 19800, or -f 18600.000185
specify the MSK baud rate. Most stations are 200 baud but some are 100 baud
specify the signal call sign eg. -c NWC. The callsign is also used as the beginning of the data output file name eg. NWC20060704.txt
specify the data output time resolution

Running UltraMSK

Once you have received your license.dat.gz file, uncompress it and copy it into the UltraMSK directory.

[james@orchid tmp]$ mv license.dat.gz UltraMSK-1.1.5
[james@orchid tmp]$ cd UltraMSK-1.1.5/
[james@orchid UltraMSK-1.1.5]$ gunzip license.dat.gz 
[james@orchid UltraMSK-1.1.5]$ more license.dat 
Name: James Brundell
Organization: UltraMSK.com
License: Evaluation
Expires: 2019-12-31

Key: A91D1C7A1F....

Use the startUltraMSK.sh to run the software. The script will start the vlfrx-tools soundcard sampler and then start one msk receiver process for each VLF station received. You will need to edit the script to specify the name of the soundcard device and to setup which stations to receive.

More information

Some more information is available in the previous installation instructions for Fedora 17

Stuck? Feel free to ask for help at any stage!