Hyperfix System Description
General description.
Hyperfix is a third generation small position-fixing system developed to operate in the frequency band 1.6-3.4 MHz. Hyperfix supercedes the earlier Hi-Fix system, development of which began in 1960. The fundamental operating principle is that of phase difference measurement in the receiver. The operating range over sea in full daylight conditions is approximately 700 km and during the night approximately 250 km, depending on the antennas used and prevailing propagation conditions. Over land and inland water, and during difficult atmospheric conditions, the range is correspondingly less. The accuracy obtainable depends on a number of factors, but under ideal conditions it is around 0.5 metres for a system operating at 3.4 MHz and 1 metre for a system operating at 1.6 MHz. Hyperfix was designed to be a highly flexible system, meeting the needs of a wide variety of users. It is capable of being used with both temporary and permanent shore-based chains, and microprocessor control is used to enable the main system features to be programmable. It also enables a high level of flexibility automation of functions such as line identification and ambiguity resolution. Although single frequency operation is possible, normally two frequencies are always used, and this does not require any additional equipment. Frequency synthesis is used to generate the transmitter drive signal and phase comparison and control is carried out by digital signal processing.
Hyperfix can operated in three ways:
Hyperbolic Operation
A minimum of 3 shore stations are required, a master and two slaves. The patterns produced are the classic hyperbolic lines, with the stations located at the focus of the hyperbolae. The accuracy depends on the 'angle of cut' of the hyperbolae, which itself is dictated by the geometry of the chain. The chain may be extended by the addition of more slave stations, such that continuos coverage of an area of coastline is achieved. The user may select 3 pairs of stations on the receiver for display of the lane information.
Circular Operation
Also known as range-range operation, this mode requires a minimum of two shore based stations. One or more stations are carried aboard the user's vessels. The positional lines in this case form a series of concentric circles centred on the shore stations, and the fix is obtained by measuring the distance to each shore station. As the distance from the shore increases, the accuracy of hyperbolic mode degrades and this is when circular mode is the most useful.
Combined Mode
Hyperfix enables the simultaneous provision of both hyperbolic and circular operation. In this way, the best use can be made of hyperbolic operation close to the shore, and circular operation further out to sea.
The flexibility of microprocessor control means that the system can be set up to fulfil a number of different tasks and to achieve this Racal have defined a number of 'Modes' of operation for Hyperfix chains. In the timing diagrams that follow, the following key applies:
- T - Trigger pulse transmitted by the master station at the start of each cycle in order to achieve timing synchronisation.
- D - Data slot, used for signaling between stations when remote control is in use
- S - Slot: a station transmits in one or more slots (1 to 6 in a Mode 1 cycle).
- U - Unit: In mode 2, each station transmits in a pre-determined slot, so each slot is related to a unit number.
- G - Guard period (transmission break)
- A - Used by the Auto-aliasing lane identification error routine
Mode 1
This mode is primarily intended for hyperbolic positioning with up to 6 shore stations in the chain. One of the 6 stations may be located on board a vessel and used for circular operation, however. The duration of the timing cycle is 600 mS, and is shown in the diagram below.
Mode 2
This mode is principally intended for circular operation, by siting one of the stations on board a ship. Two ship stations may use up to 4 shore stations in this way. Interestingly, it can also be used for joint hyperbolic and circular operation by siting one of the ship stations ashore. The diagram below shows the timing diagram for this mode, which has a cycle time of 620 S.
Mode 3
Mode 3 is a combination of the facilities available in modes 1 and 2. Up to three mode 1 or mode 2 timing cycles may be used, in any combination. For this reason, a mode 3 cycle is said to consist of up to three sequences. The advantage of this approach is that the chain can be configured to meet what would otherwise be conflicting requirements. The cycle length varies from 760mS for a single sequence up to 2040 mS for a full 3-sequence cycle. Extra slots are provided for a remote control data link and a lane identification error correction routine. The diagram below shows examples of Mode 3 cycles, based on combinations of Modes 1-2-1, Mode 1 only, and Modes 2-1.
Hyperfix Equipment
The Hyperfix equipment is built using modern solid state electronics, housed in compact cases that feature what Racal refer to as 'enhanced styling'.
Major Items
| Unit | Racal Type No | Comments |
| Receiver-Control Unit | 90515 | Performs role of site controller and receiver for shore stations and receiver and display for mobile stations. 24V DC operated. |
| Power Amplifier | 90512 | Amplifies RF drive from 90515 up to 50 Watts. Includes mains power supply and battery charger for 24V batteries. |
| Antenna Tuning Unit | 90516 | Matches output of PA unit to antenna. |
Minor Items List
- Cable assembly 90518: interconnects units
- Protection Unit 90532: lightning protection
- Secure Supply unit: 90533R rubidium high stability oscillator unit.
- 90538 Receiver antenna
Standard Station Plans
Racal envisaged a number of 'standard stations' to simplify the deployment of Hyperfix systems. There are 4 transmitting station plans (3 shore based and 1 ranging mobile) and 4 receiver stations.
SRT1: Short Range Transmitting Station
Consisting of:
- Receiver/Control Unit 90515
- Power Amplifier/Battery Charger 90512
- Antenna Tuning Unit 90516
- Transmitting Antenna Kit
- Interconnection cables
SRT2: Short Range Transmitting Station
Consisting of:
- Receiver/Control Unit 90515
- Power Amplifier/Battery Charger 90512
- Antenna Tuning Unit 90516
- Transmitting Antenna Kit
- Interconnection cables
LRT1: Long Range Transmitting Station
Consisting of:
- Receiver/Control Unit 90515
- Power Amplifier/Battery Charger 90512
- Antenna Tuning Unit 90516
- Secure supply unit (with rubidium) 90533R
- Supply Protection Unit 90532
- Transmitting Antenna Kit
- Interconnection cables
RMS1: Ranging Mobile Station
Consisting of:
- Receiver/Control Unit 90515
- Power Amplifier/Battery Charger 90512
- Antenna Tuning Unit 90516
- Transmitting Antenna Kit
- Interconnection cables
Transmitting antennas
A number of options exist for trasnmitting antennas. For permanent long-range shore stations, the Francis & Lewis WD25 30m steel lattice tower was recommended. This is described on the antenna page. Alternatively, the following antennas were available:
- 10 metre transmitting antenna Racal P/No 90048/1/3/1
- 26 metre trasnmitting antenna Racal P/No 90048/1/3/5
- 10 metre top-loaded whip antenna for ranging installations, P/No BA7D
- 7 metre centre loaded antenna, self supporting P/No BA6R
Receiving Station Plans
HMR1: Hyperbolic Mobile Receiving Station
Consisting of:
- Receiver/Control Unit 90515
- Receiving Antenna Assembly 90538
- Interconnection cables
HMR2: Hyperbolic Mobile Receiving Station
Consisting of:
- Receiver/Control Unit 90515
- Secure Supply 90533
- Receiving Antenna Assembly 90538
- Interconnection cables
Consisting of:
- Receiver/Control Unit 90515
- Receiving Antenna Assembly 90538
- 6-channel pen recorder, Chessell 3020 or Watanabe MC6715
- Interconnection cables
User Receiver Interfaces
The 90515 Receiver/Control Unit is fitted with a variety of interfaces to enable it to integrate with a variety of other systems. Soem additional units that could be provided are:
- computer
- plotting unit
- autopilot
The computer has various programs that, among other things, can convert lane values to x - and y coordinates, with respect to the shore chains or to latitude and longitude. There is also software that can provide steering information to an autopilot so that the vessel may reach a certain predetermined position.
The computer can also control a plotter that can give a continuous readout of the vessels position. With the plotter one can draw up a route in advance and state certain important positions.
The computer can also be programmed to compensate for certain errors.
MoD PINS
The MoD (Royal Navy) is believed to use a system called PINS (Precision Integrated Navigation System) on board their ships. The 90515 receiver is beleived to have been interfaced to this.
Appeal for information
The information I have on Hyperfix is far from complete. I would very much like to see the following documentation:
- Hyperfix theory and applications manual STM1201 (or, STM1218)
- Hyperfix Receiver/Controller 90515 (or 90568) manual
If you can help with this quest, please get in touch:
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Last Update 17/5/05 prev. 14/5/05, 27/4/05