[time-nuts] [Fwd: Re: Simulating LORAN-A GRI Timing Generator]

Magnus Danielson magnus at rubidium.dyndns.org
Sat Jan 8 15:35:45 UTC 2011


On 08/01/11 16:08, J. Forster wrote:
> Pondering some more on this, doing some calculations (spread-sheets) the
> actual scheme emerge... the range of 0 to 7 is not selected by accident.

I had essentially the same spread sheet...

However, how would you be able to achieve simplicity of design by being 
true to the PRI/PRR given or to what seems like reasonable counter based 
solution. Notice that the ARN-4 has a "Crystal phasing" control to 
adjust the crystal frequency of the receiver so that the receiver will 
align up to the actual rate of the master station.

I think the PRI/PRR given is a presentation simplification rather than 
true numbers. Considering that absolute frequency was not a requirement, 
the repetition rate of the master needs to be sufficiently stable for 
distinction of station and the receiver to make stable reading, in 
presence of other stations.

That LORAN-C uses GRI indications with repetition rate in microseconds, 
and fairly even such numbers as well, is another hint.

Thus, I view the PRI/PRR ratios as approximations at best, a matter of 
presentation rather than actual nominal rates.


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