no recordings available
a friendly letter, and a fine picture postcard, verify the reception
on 291.9 kHz by Rudy van Dalen, and give an example of former
navigational NDBs (1989)
The above letter shows a copy from a navigational handbook, listing
an example of the system of maritime navigation used those days.
There are 6 NDB's chained on the same frequency, and within a
6-minute sequence, each of those stations transmits its callsign,
and a long dash for exactly 1 minute. A ship's radio operator
then has the bearings of each signal on his ship's position,
allowing for a quite precisely position determination. In this
example, Gatteville in 'Sequence 6' transmits 'FG' and a long
dash in minutes 05, 11, 17, 23, 29, 35, 41, 47, 53, and 59 of
each hour, whereas Le Havre in 'Sequence 4' transmits 'LH' and
a long dash in minutes 03, 09, 15, 21, 27, 33, 39, 45, 51, and
57 of each hour. Other stations listed do it accordingly, with
'Sequence 1' starting at minute 00 of each hour. Such networks
were used very widely in coastal areas, and some are still used
(black sea, for example). Nowadays, satellite operated systems
like GPS are used.
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Callsigns:
FG
Frequencies Morse Telegraphy:
291.5
291.9
297