Fun fact: the ethereal #Datatrak sound even got into a short film. "145 kHz" by Ian Bell and Julia Childs at Another Wave AV Productions.

https://www.youtube.com/watch?v=krF8f1Ic690

https://collections-search.bfi.org.uk/web/Details/ChoiceFilmWorks/150736624

I think the thing I'm most chuffed about with all the #Datatrak stuff isn't the reverse engineering. It's that I added "wav file output" as an option and one of the people who helped build the system now has it as his phone ringtone.

I'm not far off doing that myself... after some filtering it has a sort of ethereal air about it. To the point someone made a film, "145 kHz", about it.

This is what the old Datatrak UK network looks like in field strength, WHDOP, repeatable accuracy and measurement confidence factor.
These seem to match up pretty closely with Williams (2004).
If you want to play with it, it's on Github:
https://github.com/philpem/datatrak-bandpass2

Tip: Set the Grid Resolution to about 10km per square to start with for fast calculation, then reduce it for prettier plots.
#Datatrak

If anyone else is interested in the #Datatrak LF navigation network, it turns out Alwyn Williams' PhD thesis is on the University of Bangor's website for download:
https://research.bangor.ac.uk/en/studentTheses/prediction-of-the-coverage-and-performance-of-the-datatrak-low-fr/

This contains a mountain of information on the network and how it was set up. It's a long read though - 300 pages.

macOS and Linux autobuilds 95% pass rate. Takes under a minute (each) to run.
Windows autobuild? 45%. Takes 20 minutes to run.

I'm on the verge of disabling the Windows autobuild and saying "screw that platform".

(this is related to my trying to put together a #Datatrak network simulator and foolishly answering "which platform?" with "yes")