DECCA SURVEY CHAINS

 
This document is intended to list Decca Survey chains and other products which were part of the Decca Navigator suite.

1.1 SURVEY CHAINS - SYSTEM OVERVIEW

Survey chains were either engineered and installed by Ian Thompson of Decca's Survey Department or Tom Moore of the Chain Implementation Department (CID). In the early days there was always considerable competition between CID and the Overseas Projects Department (OPD) as to who was going to do what in building new Chains.

Under Ian Thompson, the SURVEY division eventually grew totally independent and became a separate entity and distinct from Decca Navigator. Other temporary or evaluation chains were installed by the (OPD) whose head was Cecil Hamilton. There were all sorts of chains run by Decca Survey for oil exploration and numerous other activities but they were special usage and the charts would only have been issued to the specific customer and Survey's own people.

Later, Decca Survey also ran Loran C chains , Lambda chains, Pulse 8 (similar to Loran C and there were several of these chains around the North Sea), Long Range Shoran , Hi-Fix 6, Hi-Fix, Sea-Fix, Trisponder and Aqua-Fix. These were located all around the world. Some lasted for years and others for only a few months.

Survey Chains used three ground stations which radiated frequencies of 88.516 kHz (Master), 118.0213 kHz (Red)  and 132.774 kHz (Green). At the surveying receiver, these frequencies were multiplied by factors of 2, 3, and 4 without changing the phase values. In this way, two so-called comparison frequencies of 354.064 and 265.548 kHz were formed to correspond to to the Red and the Green hyperbolic patterns respectively.

In other words: If  f = 14.1129 to 14.1500 kHz.

Master = 6f
Red    = 8f
Green  = 9f

18f =265.548 kHz
24f= 354.064 kHz

Survey equipment was known as two range Decca because it only had two slaves.
Possible equipment name of 793 series.

Walter Blanchard offers some additonal information on Survey Chains.  Lambda was an early (1950's) Survey system carried mainly on board Naval Survey vesels operating in remote areas who needed to set up a Decca-like positioning aid quickly. The vessel carried a Master station transmitting a master signal that was re-transmitted by two slave stations the ship had set up on-shore. The vessel could then move about continuously measuring its range to the two slaves and thus obtaining position. Obviously it could only be used by that one vessel. It had a range of about 200 km and an accuracy of 10m.   This was the "two-range" mode. By a re-arrangement of frequencies and triggering it could also operate in a hyperbolic mode which had the advantage of being usable by several vessels if the Master vessel anchored and wanted to send out smaller survey launches".



decca_survey_decometer_04.jpg
The Survey system employed a “Two range Decca” whereby the ship ranged a Red and Green shore station. The “Mk III” on the red decometer refers to the type of meter, not the Mark of the receiver. (Photo via E-bay). 
 
1.2 LOCATIONS OF SOME SURVEY OR DEMO CHAINS

Canada - In 1971, a Lake Ontario Lambda chain was installed in support of the International Field Year for the Greal Lakes (IFYGL).

Canadians also applied Decca Survery in many ways but perhaps the most challenging was trying to establish the position of the Polar Shelf in the Arctic. Link to photos and story.

Dutch New Guinea - Use of the Decca navigator survey system in New Guinea for hydrography and as a geodetic framework2 Link to map and story.

Greenland - An order for a Greenland survey chain was placed in 1946 and it was shipped in 1947.

Europe and Africa -  Morocco, Tunisia, France - mine sweeping chains in the 1950's.

Italy
 
LOCATION DESIGNATION FREQ COORDINATES
? Master ? ?
? Red ? ?
Sabaudia, Italy Green ? 41.3000N, 13.0167E
? Purple ? ?

Nigeria - Initially, Nigeria used Survey chains. Under the auspices of David Parker, Decca Navigator was proposed for Nigeria to replace Survey. Four Navigator chains were proposed. Only two were built but they were closed down before seeing commercial service.

Persian Gulf -  The main organizer for Decca Survey was the Persian Gulf Lighting Service (PGLS) and Capt Webb. The first oil survey chain for Caltex was established in 1949. A rent-a-chain business started with Shell in 1952.

Spain  - 1957. Between Menorca and The Costa Brava a pipeline survey chain was installed for Gaz de France by Cte Jacques Cousteau with his vessel Calypso.

The "Broken Arrow" incident in Palomares Spain saw the use of Decca Hi Fix to obtain grid square fixes in the search for a hydrogen bomb on the sea floor off Spain after a mid-air collision between a B52- bomber and a KC-135 tanker. The are numerous stories about this incident on the web but the 40th anniversary story which appeared in the September 2006 issue of  FACEPLATE page 15, is a good one.

Sweden -  The first Swedish ‘portable’ Decca chain was erected in 1947 in the Southern Baltic area with stations at Skedshult (Master), Fåsbo (Red), Tystberga (Green). Transmit power was 600 watts per station. The chain was then moved to Gävlebukten in fall 19511. It also operated in Southern Bothnia 1956-1959, and in Northern Bothnia 1959-1962 when it was dismantled.

The Gävlebukten chain was used by a Finnish survey team led by Simo H. Laurila during 1951-1953. Team was using a steamship ‘Nautilus’ rented from the UK to conduct the survey. Later, Vaino Lehtoranta, OH2LX  helped Laurila to finish his doctoral thesis in 1953-54, soon after he left to Ohio State University, then to Hawaii University. He wrote a well known book,  "Electronic Surveying and Mapping", Ohio University Press, Columbus, 1960.
 

1.3 RESTRICTED-USER CHAINS

* North Sea oil: Sea Shell, Sea Search etc.
* Gulf of Mexico: Mk V chain for use for oil companies.
* Vietnam -  a special Decca chain was built for the US government.
* Europe: a special chain operated exclusively for the RAF. (See 1.4.2)
* Christmas Island: Britain's first hydrogen bomb tests. Used mainly by the RAF.

1.4 OTHER

1.4.1 The Decca Data Link

* Used by the Decca Ambassador aircraft flying along the Berlin corridor using the plot from the Data Link equipment installed at Tempelhof airport

1.4.2 R.A.F.'s Secret German Chain

John Molloy-Vickers recalls the secret German chain built for the RAF:.

"There was another UK Ministry of Defense chain installed in Germany in the early 1960's. Initially they were secret but they were given RAF station names on boards outside the front gate, thus overriding any prevailing secrecy.  It was also difficult not to notice a 300 foot  and a 150 foot  mast in a field.  Two of the stations were located near Zeven Germany and Glandorf/Bad Iburg.

I recall we shipped the equipment as quietly as possible but it was delivered to site in RAF trucks. The idea was interesting as they were to be fired up in the event of a major conflict with the Russians. There were double towers at each site with two signals and the intent was that one would cloak the other so nobody could jam the main signal. It was hoped it would last long enough to get the Vulcan  nuclear bombers (equipped with special receivers) on their right course".

One ex-Vulcan navigator said that in the event of a nuclear war, he had planned a one-way trip to Moscow, arming the bomb en-route and heading back to somewhere in Africa on the understanding that Europe would then be in ashes.

Dennis Ruffles relates his experiences while serving with the RAF. " I was posted as a ground wireless mechanic  in Germany in late 1961. Here I worked on the Tactical DECCA chain as it was being set for operation around 1962 and stayed with the chain in Germany for 3 years. The chain was considered "tactical" because the equipment was shipped in air transportable containers, although the containers were effectively  "grounded" once a site was installed. This chain used the lower frequencies and not the higher frequencies as quoted in par. 1.1 above for Survey Chains.

The Master site was located at Glandorf with the slaves at Jever in the  north (about 60 km ENE of the civilian site at Zeven) and at Dannenrod in  the south. Each site had two towers;  the main tower being 300 feet tall with a 150 foot standby tower.  Each tower had its own modular transmitter.  If I remember correctly, the main transmitter had a maximum power of 3.6 Kw but we ran them at only a fraction of this power.

When we started operation, the sites were active and transmitting continuously until the chain was shut down in the early 1970s. We did not use any "cloaking" transmissions to prevent jamming.  Protection from jamming was achieved in the following ways:

1)  We made every effort to transmit a very pure and stable sine wave to reduce the bandwidth to the minimum.  To this end, we even ran our power amplifiers in Class B mode to avoid noise on the signal.  This was expected to make it extremely difficult to jam.

2. By using a very narrow bandwidth, a jamming signal sweeping the frequency band would only interfere for short periods. Since the receivers would "flywheel" in such cases, it was difficult to disrupt the system.

3. Transmission from all sites was continuous with no lane identification signals.

4. The system was arranged so that we could change the frequencies of the chain in a matter of seconds in the event of an operational frequency being jammed.  I think we had 3 or 5 frequency sets to chose from.

From an administrative standpoint, we came under No.140 Signals Unit based in Iburg.  This unit had been running the North German GEE Chain since it's inception. We were a slightly "odd ball" part of this unit as they were all radar personnel and we were wireless bods. For me, this was a plum posting, being billeted in a small hotel in a village in the American zone for 3 years".

FOOTNOTES:

1. Iggö (M), Hornslandet (R), Gräsö (G).
2. Verstelle, J, Th. . Report, GA, IUGG, Toronto, 1957.



Credits and References:

1) Vaino K. Lehtoranta, OH2LX. E-mail:  <vaiski(at)dlc.fi> provided the initial information on Decca Survey.
2) Brian Kenny provided information about Italy and Dutch New Guinea. E-mail:  Brian.Kenny1(at)btopenworld.com
3) Dennis Ruffles  <dvrv1(at)tiscali.co.uk>
4) Walter Blanchard <wblanch(at)ntlworld.com>

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Feb 4/14