the 3 maritime radiobeacons IJmuiden *YM, Hoek van Holland *HH, and Eierland *ER formed a network on their working frequency, where each of the stations was transmitting the callsign and a dash for 1 minute each, giving the ship's radio operator good bearings to several fixed points in short time. A special item of this network was the use of a defined pitch of the dash: here it was 1052 Hz to differentiate from other signals. With the use of GPS (and DGPS) signals this service became obsolete.
no recordings available
see this very detailed letter from the files of Rudy van Dalen
(1982)
------------------------------------------------------------
Callsigns:
HH
Frequencies Morse Telegraphy:
287.5
294.2
.