VLF Software Packages

To be successful on VLF the use of software based digital signal processing on a PC is almost essential. The following packages are recommended, particularly the first. All are freeware or shareware.

Spectrum Lab

A powerful package by DL4YHF. Details and download at http://www.qsl.net/dl4yhf/spectra1.html. This is THE package to use: it is very powerful, but not that easy to use initially.  Once the fundamentals are grasped, it can be configured in many ways.  A great feature of this package is the ability to use a VLF MSK signal such as GBZ as a frequency reference to automatically calibrate a PC's sound card. This allow fantastic frequency accuracy and stability without the need for an external GPS reference. Speeds such as QRSS6000 are possible using such frequency locking. The same package can also be used to generate stable signals for transmitters too, although I've yet to find out how!

A less powerful, but very useful package from http://www.weaksignals.com/ .This is my choice for use in local area (0-10km range) earth mode tests at QRSS3 speeds as it is easy to understand, set up and use.

A simpler version of Spectran from http://www.weaksignals.com/ .

SM6LKM's PC based VLF Receiver

A complete VLF receiver implemented in software on a PC. Great for checking your system is working correctly by listening for Alpha beacons, GBZ and other VLF MSK signals. This was originally produced to allow people to receive SAQ on 17.2kHz but it is tunable from 0-22kHz. Available from https://sites.google.com/site/sm6lkm/saqrx