[time-nuts] [Fwd: Re: Simulating LORAN-A GRI Timing Generator]
jfor at quik.com
Sat Jan 8 15:08:12 UTC 2011
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.
The base pulse repetition rate is 30 ms, 40 ms and 50 ms. The pulse
repetition rate modifiers modifies the repetition rate by -100 us per
step. It would only take two (or possibly three) wheels to select PRR.
This explains the high rate starts with 33 3/9... it also makes the
receiver design easier to understand.
Very interesting observation! I did the calculation using Excel (attached)
but missed the 100 uS increments., I was blinded by modern precision.
Since the LORAN Indicator has sync circuits, your observation is a nice
simplification. Thank you.
So a 10 kHz source would suffice for PRR settings. A phantastron divider
from a 100 kHz standard should do it in those days technology, if not a
10 kHz standard was used directly.
Only the delayed pulse would need the full set of thumb-wheels.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: LORAN-A GRIs.xls
Size: 18944 bytes
Desc: not available
More information about the time-nuts