The Cubic Corporation ARGO MF Positioning System
contained in this page.
Overview
ARGO (Automatic Ranging Grid Overlay) was a product of the Cubic Corporation of the USA. It was also sometimes referred as DM54. It was a positioning system using phase comparison techniques, operating in the 1.6-2.0 MHz band. It offered accuracies of around 4 to 7 metres and had a maximum range of 400km. The way in which Argo operates is significantly different to that of Hi-Fix or similar systems; it operates primarily in the range-range mode with up to seven mobile stations being able to use the same shore stations by means of time sharing. There is also a hyperbolic mode that allows an unlimited number of users to share the system.
An Argo chain consists of a master station and four slave stations. The transmission cycle is two seconds long, and is divided into seven 'sub-cycles', each of which is further divided into 44mS time slots in which a station may radiate a 36mS long RF pulse- except for the first time slot in a sub-cycle, in which the master station transmits a triggering pulse which is 120mS long.
The cycle commences when the master station radiates a trigger pulse that, because of its length, is uniquely identifiable by all stations. On receipt of the trigger pulse, the first ship-borne (mobile) station will transmit an interrogation pulse in the next time slot. This pulse is received by all of the slave stations, which measure the phase difference between the interrogation pulse and their own synthesised master oscillator. Each of the slaves then replies in turn in one of the four following time slots, with an RF pulse whose phase is adjusted to replicate that of the received phase. The mobile receiver receives all of these replies, and computes its postion by comparing the round-trip phase delay to each slave station. Following the next trigger pulse, the next mobile will transmit and so on until all seven will have obtained positions. There then follows a period of silence before the cycle repeats.
Lane identification can be used and requires the use of a second radio frequency approximately 10% higher than the main. The mobile operator can initiate a lane-check, transmissions are then made alternately on the lane identification frequency until the control unit has computed the lane error, which is presented to the operator as a number of lanes.
Poor image of ARGO units(?)
Argo stations comprise a Range Processing Unit (RPU) and an antenna coupling unit. The arangement is the same for all stations, except that the mobile requires an additional control and display unit. The transmitter output is up to 100 watts. The units are pre-programmed with up to 16 frequency pairs, and no retuning is required over a 200kHz switching bandwidth. The transmitter incorporates SWR monitoring and will reduce the output power to safe levels when working into a poorly matched load. Antennas can be between 8 and 30 metres high.
A feature of the system is the ability to integrate with a variety of other systems due to a number of flexible interfaces; GPIB and RS232 both being provided.
Chain Station Antenna
The Chain Station tower is made by Texas Tower & Mfg Ltd, of Irving, Texas, USA. It is triangular in section, with each face being 11 inches approx. and it is supplied in 10 ft. sections. The tower stands on a single insulator and is guyed with poly rope, 4 guys being attached at 20 ft intervals. A ring is provided for the attachment of ground plane radials- see the picture below.
Ship Station Antenna
This could be a Shakespeare model 222 glass-fibre whip of around 20 ft length.
Chain Station Power Unit
Below is a photograph of an ARGO 19in rack mounting power supply, in a chain station installation. Of the two switches on the right, the top one is labelled 'DC Output' and the bottom one is labelled 'Charger'. The switch on the left is labelled 'AC Input'
Sherod Crowell says:
"I started working with Positioning Systems for the Offshore Oil & Gas Industry in 1980. At that time, a new era of exploration/drilling was beginning & the first 'jack-up' rigs were arriving on Canada's East Coast.
"After spending 15 years plus in electronics servicing, I made the switch to a company offering survey & positioning services to the Oil & Gas Industry. I worked for more than 25 years with that company, and others as a field/shore technician installing & maintaining positioning systems. Most of my work was land or land-based, however I did occasionally do sea-time as a survey navagator. In fact one of my first assignments was 5 weeks on a seismic vessel in the Labrador Sea as electrical technician/ survey support. The client and operator for that job was Sefel Geophysical of the U.K..
"Previous to that i had been working on an ARGO chain set-up along the south coast of Nova Scotia. Most of the Stations were powered with Thermal Gererators & fueled by propane gas. So a lot of the work was trucking this propane & changing it out as required.
"Along with the ARGO, I was also looking after several MINI-RANGER stations set up for calibration of the ARGO. I also worked the Labrador coast, where there were 2 chains of ARGO with Mini-Ranger, Again all stations were powered by Thermal Generators & propane gas. This gas had to be transported to the stations by helicopter . It was in 100 lb. cylinders; each of which weighed over 50 lb empty, and about 160lb when full- so this was LOTS OF WORK!. Some of the stations were a considerable distance from where the helicopter could land it. For some sites we could sling in the cylinder with a small helicopter, but for the Northern stations this was not possible and so the cylinder had to be carried INSIDE the machine & often lying on their side- we took lots of risks back then that would never be allowed today!
"I spent many years on Sable Island running operations there for several companies. Duties included: Base-camp ops. Set-up & maintence of Positioning. Systems; ARGO, Mini-Ranger, Syledis, Del-Norte Trisponder. Misc. EDM. , Misc Radio comms, Vehicles, & so on.
"In later years I worked with Differential GPS stations; some 'In-house' systems using Trimble Receivers & Icom radio equipment. Then I spent a while working for Racal on their Differential GPS system, Delta-Fix. I Worked these systems both on the East Coast of Canada and the Arctic."
The photographs in this web page must not be used elsewhere without permission.
Page created 3/3/06, went live 30/4/06.