Swedish Hyperfix Chains
The Swedish Navy operated until recently a number of Hyperfix chains giving coverage of Swedish waters. The Swedish government publishes a document, "The Swedish Radio Navigation Plan" which contains some interesting references to Hyperfix operations. The plans for 2002 and 2003 can be found on the internet. I quote from the latter document:
|
Naval surface units use mainly radar, GPS and DGPS as add-on systems to the on-board DR systems (gyro compasses, log). Hyperfix still serves as a back up system. For sub-surface vehicles the primary navigation system is INS supported by GNSS whenever it is available. For safety of life applications, e.g. handling and clearing of mines, other HF radio navigation systems can be used. Generally there is a trend towards increased use of INS as a main navigation system integrated with other sensors. Decca Navigator has been taken out of use and Hyperfix is being used only as a back up system until all installations are taken out of service. Increased use of the transponder system based on GPS for identification and short message communication is foreseen. It is also possible that the transponder system will be extended to other functions than positioning and navigation. |
Thus it would appear that Hyperfix continued in use in Sweden well beyond the time that it was decommissioned elsewhere- certain it was still available in 2003.
One of the chains gave coverage of the Baltic Sea from approximately the Southern end of the island of Gotland to North of Stockholm, and from the Swedish Coast east to the shores of Latvia and Estonia. At least two other Hyperfix chains provided coverage elsewhere. 5 Stations provided the coverage in this chain, as shown on the map below.
The curved countours show the positioning accuracy of the system, in metres. You can see that most of the coastal waters wround and to the south of Stockholm is in an area with accuracy better than 5 meters.
The locations of the stations, as closely as I can place them on a map, are as follows:
| Station 1 | Torö |
| Station 2 | Runmarö |
| Station 3 | Hall |
| Station 4 | Gryt |
| Station 5 | Norrköping |
I am indebted to Vaino Lehtoranta OH2LX who has studied the signals received from the Swedish chains, and provided me with most of the information on this page.
Here is an audio clip: Real Audio|mp3 (coming soon)
The diagram below shows an oscilloscope view of the signal received off-air from one of the chains.
Here is a view of the RF spectrum around 1809 kHz:
And here is a diagram showing the transmission pattern of two of the chains on 1809 kHz. They appear to be synchronised and run together as a 1-2 sequence occupying 35 40mS time slots, thus the entire sequence lasts 1.4 seconds.
Last update 3/3/06