[time-nuts] Datatrak navigation system - looking for signal recordings and technical information

[Philip Pemberton]

Hi there,

I'm currently on what some might call a fool's errand: I'm trying to
build a signal generator to simulate the old Securicor Datatrak (later
Datatrak / Siemens / Mix Telematics) LF signal chain.

Bear with me before you laugh ;)

Datatrak was an LF navigation system, originally built by Securicor to
track their armoured vans as they moved around the UK. It was a little
like Decca Navigator but had a few unique attributes -- automatic lane
identification and a data channel for one.

I've figured out most of the signal format, at least enough to have a
fifty-fifty chance of getting the receiver to lock on and decode it.

At this moment in time I'd really like to find someone who has
recordings of the Datatrak signals. These were transmitted between about
130 and 145kHz and have an odd warbling/chirping sound to them. There's
an example on Youtube:
  https://www.youtube.com/watch?v=NbCfYXab0QQ

I've heard rumours that there's still a Datatrak chain operating in
Argentina and parts of Brazil. A recording from this (upper sideband
mode, radio tuned about 500Hz to 1kHz lower than the signal frequency)
would be tremendously useful if the rumours are true!

Otherwise -- any information on the system would be of interest to me.
I'm piecing things together by (slowly!) reverse-engineering the
receiver firmware... this might go a bit faster if I had a pair of
27C010-capable EPROM emulators, but such is life.

Thanks,
-- 
Phil.
lists at philpem.me.uk
http://www.philpem.me.uk/