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

J. Forster jfor at quik.com
Sat Jan 8 16:23:54 UTC 2011

```My belief is, if you were looking at the H0 Master, and H0 has two Slaves,
the two TDs (one to each slave) is sufficient to give you a position fix.

LORAN-A stations were closer together than LORAN-C  (maybe 600 mi).
Nothing I have read to date indicated there were more than 2 Slaves per
Master.

Since it seems impossible to distinguish between the Slaves, based on
their signals, there might be two apparently valid position solutions.

-John

==============

> So if I read the excel correctly you only actually need 1 system.
> Say H0 is the master then the delays for H1-X is how far away from the
> master the pulse would be. More importantly you would only need 2 other of
> the Hs to create a navigational fix.
> Is this a correct interpretation?
> Have to go dig out of the snow.
>
> On Sat, Jan 8, 2011 at 10:35 AM, Magnus Danielson <
> magnus at rubidium.dyndns.org> wrote:
>
>> John,
>>
>>
>> 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.
>>>
>>
>>
>> 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
>> 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.
>>
>> Cheers,
>> Magnus
>>
>>
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>

```