[time-nuts] Loran

Magnus Danielson magnus at rubidium.dyndns.org
Sat Dec 1 16:58:59 UTC 2012

On 12/01/2012 05:05 PM, Mark Kahrs wrote:
> Very interesting topic.  So, it appears that UrsaNav bought a pair of
> companies that have interesting IP.  In particular, CrossRate has a few
> interesting patents -- this may be the most relevant:
> United States Patent Application 20080144744:
>   A system for demodulation of the Loran Data Channel transmitted over the
> Enhanced Loran (eLoran) system including a quadrature filter. The
> quadrature filter calculates the real and quadrature phase components of a
> received ninth pulse. The resultant components are used to obtain the angle
> of the ninth pulse. This angle is then compared with a set of pre-tabulated
> angles/symbols that are calculated using the same quadrature filter on
> thirty-two different simulated ninth pulses. The closest angle match gives
> the corresponding symbol. Such twenty-four symbols make up a single Reed
> Solomon encoded message. This message is then passed through a Reed Solomon
> decoder and the transmitted message is obtained.

Do read the paper, as it proposed to remove the ninth pulse and use a 
OFDMA modulation for the data-part while the PNT part would be modified 
variants of the traditional LORAN-C pulses. This patent would those not 
be relevant for the proposed scheme.

> Also, UrsaNav teamed with Nautel, noted LF amplifier designer for this
> system.  Interesting.

Considering that they intend to change pulse-shapes and even add a 
complete new modulation technique, the transmitters need to support it.


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