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. Cheers, Magnus
LORAN-A GRIs.xls
Description: MS-Excel spreadsheet
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