THE ORFORDNESS RING

The Orfordness Ring is situated to the east of the Bomb Ballistics Building (see photograph p1 below):


 
To my knowledge there is no public record of the building, purpose, use; or technical details of the Orfordness Ring.  So far as I know there is no information, obtainable through legitimate public research, regarding the Ring in the public domain.

Most of what follows is therefore informed deduction, for which I alone am responsible.  However there are two problems with such deduction.  Problem one is security.  I would not wish to compromise in any way current U.S. U.K. security.  Mine is HISTORICAL research from public sources only.  Although tempted, I have sought to specifically avoid connecting any of this historical technology to current defence technology.  (The original text of this study was submitted to the Secretary to the Defence, Press & Broadcasting Advisory Committee before publication by disc and on the Internet).  Problem two is "The Jigsaw Effect" - the temptation to selectively collect and distort the evidence to support a particular theory.  I have tried to avoid this by a process of continuous review.  This has led to some rather indefinite results and the generation of more questions than answers!

Summary:

It is my deduction that the Ring was an H.F. research, possibly operational, facility concerned initially with the U.S. Forward Scatter Over the Horizon System 440L (1964 -1981), and possibly later with the preparations for the Cobra Mist Over the Horizon H.F. Radar.


Geoff Taylor November 2009 (see Index - Copyright/Contact)

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Index:

Description of U.S.Forward Scatter Over the Horizon System 440L
Description of Cobra Mist
Availability/Use of the Orfordness Ring site
My Photos (7/6/08) and Sketches
My Deductions Bearing 1
My Deductions Bearing 2
My Deductions Bearing 3
Mapping Bearings 1, 2, & 3
Analysis of my three bearings
Transmitter/Receiver coverage
Conclusion
Sources used to make this website
  (Books, Websites, Background Information)
Acknowledgements
Abbreviations
Copyright/Contact
Amendments


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Description of U.S.Forward Scatter Over the Horizon System 440L:

System 440L was an H.F. Forward Scatter Over the Horizon  system (O.T.H.-F.) deployed by the U.S. in 1967 to detect changes in the ionosphere caused by missile launches.  In 1968 the system was modified to show ionospheric disturbances caused by nuclear weapon tests.

See 'Advances in Bistatic Radar' pages 52-54, (see sources) from which I precis:

System 440L was developed by Stamford University in the U.S. in 1962/63.  In 1964 the long-range part of this research was moved to Europe (To Orfordness I think).  In 1967 System 440L was fielded.  Transmitters are quoted in Taiwan, Japan(2), Guam(Okinawa) and the Philippines; corresponding with receivers in Italy(2), Germany and the U.K. (Possibly Orfordness).  (Note that at five of these nine locations I think that 440L remains are viewable using Google Map/Satellite.  Note also that two of the five receiver sites and two of the four transmitter sites are currently active U.S./U.K. military bases).   In 1968 System 440L was modified to enable the detection of high altitude nuclear weapons tests ('A.E.D.S. Document 12' refers to modification of 440L at U.S. Air Base, Italy - see sources).   In 1970 the system was declared operational.  In 1971 it was demonstrated that the system could be easily 'spoofed'.  In 1975 dismantling of System 440L began. System 440L was finally ended in 1979.  (But note that 'The History of HQ U.S. Forces in Japan', 1975, refers to the termination of the three Japanese 440L transmitters in that year - see sources).

Technical:  System 440L used unmodulated C.W. transmissions having a relatively small target coverage per signal path, but there were many paths crossing over suspected Russian missile sites.  Detection of missile launches was by doppler-time signal recognition.  Range measurement was by triangulation.  Barry-Chirp sounders (pathfinders) were used at each end of the links for operating-frequency selection.  At the far east transmitting sites AN/FRT-80 transmitters fed imbricated (overlapping) rhombic antennae.  (I think that the Orfordness Ring was such a transmitter).  Receiving sites used different antennae, including eight-element phased monopole arrays.  (I think that there are the remains of such a receiving antennae at Orfordness today and that this antennae is shown on the April 1965 O.S. Aerial photograph reproduced on page 85 of 'Suffolk's Defended Shore' - my fig3).  Low noise, low spurious, receivers (Said to be AN/FSQ-76) were used.  Phase-coherent equipment drove the doppler processors and pattern-recognition equipment.  The achilles heel of the system was its simplicity.  An experiment by Stamford University in April 1971 illustrated system vulnerability in real-time. (precis ends)



See also www.history.army.mil//html/books/bmd/BMDV2.pdf  (see sources), from which I precis:

At the time of constructing B.M.E.W.S (Thule 1960, Clear 1961, Fylingdales 1963) it was recognized that there was only limited north and south coverage.  To cover launches to the south  it was decided to install a Forward Scatter O.T.H.R. net around the Soviet Union. The net would have four transmitters located in: The Philippines, Okinawa,  and Japan - 2; and five receivers in: the Mediterranean,  Italy - 2, Germany and England; with a correlation center in Northern Italy connected to N.O.R.A.D.  This system became operational on New Year's Eve 1965 but was beset with operational difficulties - from 7 to18th. June 1968 only 20% of launches were detected.  As a result there was an extensive revision of operating procedures which significantly improved the number of launches detected. (Note reference to modification of 440L in 1968 to detect Nuclear Weapons Tests - see sources).  System 440L is listed as a U.S. operational asset as at 31st. December 1971 having four transmitters and five receivers. (precis ends)


Note that System 440L was not a radar.  System 440L transmitted H.F. signals on one side of the world which were received, by H.F. multi-hop, on the other side of the world. The 'normal' characteristic of the received 440L signal was known.  Missile launches, and nuclear weapons tests, caused changes to the received signal from the normal state.  These changes too were known, each 'change' possibly being the signature of a missile launch or nuclear weapon test. ( See 'Advances in Bistatic Radar', page 52, para. 3, - refers to missile R.C.S. measurements1962/3 - U.S.A. - pre fielding 440L European/Far East 1964)


Coverage of System 440L:


Note that from the above map, for every transmitter to transmit to every receiver, and for every receiver to receive every transmitter; then all the transmitter antennae and all the receiver arrays would need to be steerable over approximately 30 degrees.  'Advances in Bistatic Radar', in the caption to fig 4-2 - see my fig 5, quotes "...... beam forming over about 100 degrees of azimuth coverage, from 5 - 25 MHz."  for two linear receiving phased-arrays - see my figs 3 & 5.   For the imbricated (overlapping) rhombic transmitting antennae I have no technical information, but looking at my picture 7 (later) it seems likely that the Orfordness Ring antennae had an coverage of approximately 90 degrees, and this is confirmed by looking at other rings (later).  It is a puzzle therefore that if only a coverage of 30 degrees was required, why did the transmitting and receiving arrays each have a coverage of approximately 100 degrees?  Was System 440L intended to have greater coverage to the north/south?  If so where would the additional transmit/receive sites have been located?  A second puzzle results from looking at the five sites currently viewable using Google Map/Satellite.  One of the two transmitter sites viewable also has receiver linear arrays and all three receiver sites viewable also have transmitting rings.   'Advances in Bistatic Radar' refers to ".... Barry Chirp sounders ....... were used at both ends of the 440L links .....".  But I do not think that a 50 meter diameter ring transmitter would have been needed for chirping (H.F. pathfinding).  Was it the case that the 440L system could transmit/receive from either end of all, or some, of the links?  (Note I have assumed that the linear arrays receive and the circular rings transmit).



Description of Cobra Mist:  (Which was an H.F. Over the Horizon Radar)

No description of mine could compare with the wealth of history, technical and equipment detail,  and operational performance, including diagrams and photographs; all  contained in Part One of the U.S. F.O.I.A. report regarding Cobra Mist (see sources).  The map of Cobra Mist coverage and bearings is specially relevant - Pt. 1, fig 2.  Also relevant is the chronology of Cobra Mist, as follows: Bids (U.K.) invited 1966, construction began 1967, testing 1971-73, closed May/June 1973. (see sources)

 

Availability/Use of the Orfordness Ring site:

The chronology of use of the Orfordness site after 1945 can be read on pages 98 to 115 of  'Orfordness Secret Site'.  From this it would seem that the Bomb Ballistics Unit ceased to operate in May 1956.  However research by Mr Paddy Heazell, National Trust, indicates that use of the Bombing Range by A.W.R.E. continued until 1958.  As the Ring is built on what was the bombing range  I deduce after-1958 to be the earliest possible construction date for the Ring.

If my deduction that the Ring was  an experimental/operational facility for the U.S. Forward Scatter Over the Horizon System 440L is correct, then it would probably have been difficult for such a facility to co-exist operationally with Cobra Mist - operational for testing July 1971.  (Both 440L and Cobra Mist operated in the same H.F. band:  440L 5-28MHz; Cobra Mist 6-40MHz).  Hence I deduce that use of the Ring as an H.F. facility probably ceased by 1971.

The window of availability of the Ring site I deduce therefore to be from 1958 to 1971.  Comparison of this window with the chronology for System 440L fits; as follows: System 440L was first of all tested and developed in the U.S.A.  in 1962/3.  (Details in 'Advances in Bistatic Radar' - see sources).  "In 1964 the long-range portion of the project was moved to a Western Pacific to Europe path complex"  (To the Orfordness Ring I think). System 440L was modified in 1968, and declared operational in 1970/71.  Note that Cobra Mist did not begin testing until 1971, so it is reasonable to assume that use of the Ring for System 440L research and Cobra Mist preparation could have been completed before Cobra Mist began testing.  However if the Ring was an operational component of System 440L then relocation elsewhere in the U.K. would probably have been necessary in 1971.  There is evidence for such a relocation at another site in the U.K.

Therefore I deduce that the possible working life of the Orfordness Ring as an experimental, perhaps operational, facility for System 440L; then possibly in the preparation for Cobra Mist was probably from 1963/4 to 1970/1.


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My Photos (7/6/08) and Sketches: (p1-6)


NOTE: all the bearings herein were measured using a protractor against Grid North on O.S. Map 212.  To this Grid North bearing I added 3 degrees to convert the protractor bearing to a True North bearing.  It is these True North bearings that are  quoted herein.


The Ring is 50m in diameter.




The Ring has surface-plinths and fixing bolts; also two triangles, one shown here, both inward
pointing.

 
          

The surface-plinths are not all round the Ring.


 
This picture shows the anchorages and bases, inside and outside of the Ring.


a,a,a, anchor center mast A.

b,b,b, anchor a mast at B  (The b,b,b, anchorages are different to a,a,a, - perhaps mast B did not co-exist with Mast A).

Z and off photo Z are anchorages possibly associated with mast B.

T and T are approximately the positions of the two triangles, both inward pointing.

P to P indicates the approximate extent of the plinths around the eastern side of the Ring.


I think that three possible antenna arrangements can be deduced from the dispositions of the anchorages/bases, triangles and plinths.



Between the Ring and the Bomb Ballistics Building there is a Platform.


I think that this was the location of the Ring transmitter equipment.

The Platform has a pillar to which is fixed the remains of electrical switchgear.

There is a duct under the Ring opposite the Platform.



Within the Ring opposite to the Platform there is a substantial circular metal 'stud' projecting from the ground.
l

I think that this stud was for earthing.



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My Deductions:


Bearing 1: (p7, p8, fig1) (yellow)

A line projected through Z,a,A,b,B, and off photo Z lines up with the Black Beacon.   T,T, - the Ring-triangles are equidistant to each side of that line pointing inward.  If this line is projected northward, at 17 degrees, it passes over Spitzbergen and on toward the Bering Sea.



What was the purpose of the Ring-triangles?



At the Black Beacon there is a ring of pavings in the floor, and a small building adjacent.

                                             

I think that this small ring and building at the Black Beacon, may  have been connected with the Ring and Platform.  The alignment of the Black Beacon, the Ring-triangles (purpose unknown), the ring-center and Spiztbergen/Bering Sea (17 deg.) may have been intentional when the  Ring was constructed.   However I have found nothing indicating what, if any, type of antenna might have been erected on this alignment.  Nor have I found, using Google Map/Satellite, any indication of any likely equipment on Spitzbergen (cloud obscured) or on the Bering Sea Islands; although both locations have been used for ionospheric and radar research, Spitzbergen since pre WW2, the Bering Sea Islands post WW2.  

However, given a coverage of 90 deg. the southern aspect of the 17 deg. bearing would have included all the Japanese 440L transmitting sites.  The northern aspect would have covered from Kamchatka to Northern Canada/Greenland approximately.  Also at another English 440L receiving site (not Orfordness) there are two in-line arrays and a ring.  The alignment of the ring cannot be deduced but the arrays are centered on 30 deg., which again with 90 deg. coverage would have included all the Japanese 440L transmitting sites within the southern aspect; the northern aspect would have covered from Japan to Alaska approximately.  And at Okinawa, Japan there is a ring(?) which seems to have a ring-crossing log-periodic array (?) aligned at 10 deg..  To the north the alignment passes over the most north-eastern part of Russia and on to Artic Canada/Northern Greenland.

From these three alignments I think that a case may be made for a northern aspect to System 440L, not obvious from the published information.  Thus the 17 deg. bearing at Orfordness may have included such a, conjectural, northern aspect of System 440L; and note that this was probably the first arrangement of the Orfordness Ring, as built.



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Bearing 2: (p7, map-ded 2, fig 2) (red)

A line projected eastward (seaward) through the center-line of the Platform, the central mast-base and the approximate center of the Ring-plinths; is at 116 degrees.  With 90 deg. steerability this gives coverage from Borneo to Southern Africa.  If the projection of this 116 deg. center-line is continued eastward, that projection passes down the length of Italy, through the Mediterranean, across Saudi Arabia and into the Indian Ocean.  This bearing of 116 degrees with 90 deg. coverage does not cover any of the 440L far eastern transmitting sites; but it does cover four of the European 440L receiving sites, but the significance of this must be debatable as the antennae at these sites would, logically, have been directed eastward.
 





This sketch (fig 2 below) is my idea of the type of antenna which might have been used on this 116 degree alignment, based on 'Advances in Bistatic Radar' Page 53, third paragraph. "At transmitting sites in the far east, the AN/FRT80 transmitters fed imbricated (overlapping) sloping rhombic antennas".  Antennae like this may have been used at most System 440L sites.


I think that there are also five 440L locations where the remains of rings - circular antennae bases possibly similar to my fig 2 (and similar to the Orfordness Ring), also linear arrays perhaps similar to those in my fig 3, can be viewed using Google Map/Satellite.

Okinawa, Japan (Tx.): Two rings ??? - one with ring-crossing antenna ??? - aligned approximately 10 degrees north - not toward any known 440L location.  No arrays.

Philippine Islands (Tx.): Two rings + arrays ?  Both rings - northern aspects, do align with 440L Europe.  Each ring total coverage is 110 deg., from North Norway to the tip of South Africa.  There are also three in-line linear arrays, the southernmost of which seems to be disused.  The European 440L receiver sites are covered by the northern aspect of the two, I presume in-use arrays; the total coverage of these two presumed in-use arrays, assuming 100 deg. steerability, is from North Norway to the tip of South Africa.

Southern Italy (Rx.): Two rings, and arrays similar to my fig 3.  The larger ring is comparable with the Orfordness Ring but there is no visible evidence of direction.  The northward array aspect covers 440L far east.  The southern array may have been disused before the Google Map/Satellite image was generated.  The total coverage of both arrays would have been approximately 120 deg.; from Finland to Western Africa.  The smaller ring is between the arrays, as at Orfordness, and there is something, I know not what, in the center. (Possibly for 'chirping'?)

Mediterranean (Rx.): One ring - clearly shows ring-plinths. No bearing evidence.
Note: from the dtic.mil website "Description of one-way tests from the Mediterranean to Cobra Mist" (see sources), page two, third paragraph:    (I quote) "The signal was transmitted via a side lobe of a rhombic antenna array, since the main lobe was not steerable to our azimuth." (end quote)  Perhaps this test transmitter was my presumed Mediterranean 440L ring shown by Google Map/Satellite?  If this ring was a 440L component then it would be normally facing east - hence possibly "...... not steerable to our azimuth" (Orfordness). (Note this might be an indication of the steerability limits of the 440L transmitter antennae; also this ring, at a 'receiver' site, was, at least for the purpose of the Cobra Mist tests, a transmitter).

England Rx. (not Orfordness):  One ring and immediately to the right two in-line linear arrays.  The alignment of the ring cannot be deduced but the arrays are centered on an alignment of 30 deg. - the southern aspect of this alignment would have included all the Japanese 440L transmitting sites.  The northern aspect would have covered from Japan to Alaska approximately.


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Bearing 3 - 65/66 degrees: (fig 3, p9-11, fig 4-5) (black)

An Aerial photograph of Orfordness, April 1965: (Please note acknowledgment)




This aerial photograph I interpret as showing a log-period antenna crossing the Ring, offset from the Ring-center.   To the north of the Ring there are two linear arrays, each angled southward, the resultant angle between the arrays being approximately 100 degrees. The track to the Lighthouse has been diverted around the eastern array.  The Ring-Platform and the Bomb Ballistic Building can be seen; also to the south of the Ring and the two arrays there is a small square (coloured red on my diagram), I assume this to be a building, perhaps housing operating equipment for the Ring-crossing log-periodic antenna, and/or the two linear arrays.  Note that the Ring-crossing log-periodic antenna and the two linear arrays may not necessarily be part of the same equipment; also that both antennae and arrays may have been located elsewhere on Orfordness before and/or after the date of the O.S. aerial photograph (April 1965).  Note also that this aerial photograph shows no evidence of any antenna on the 116 degree alignment shown in my P7/fig 1(Bearing 2).  Lastly note that the bearing (66 degrees from the O.S. Map) of the Ring-crossing log-periodic antenna is NOT the same as the Black Beacon - Ring-center alignment of 17 degrees shown in my P7/P8/fig 2, (Bearing 1) but IS almost the same bearing as the center-string alignment of Cobra Mist (65 degrees - from F.O.I.A. Report Part 1, fig 2; 66 degrees from the O.S. Map).

By reason of this bearing similarity (65/66 deg.), and the possible antenna similarity to any one element of  Cobra Mist, I think that perhaps the Ring-crossing log-periodic antenna may be associated with the preparations for Cobra Mist.  However the linear arrays do not belong to Cobra Mist but are of the System 440L type described and illustrated in 'Advances in Bistatic Radar ', p 53, fig 4-2; and also, I think, the array remains which can be seen using Google Map/Satellite at the Southern Italy 440L site.  I therefore think that perhaps the Orfordness linear arrays may possibly have been reused for Cobra Mist work together with the Ring-crossing log-periodic antenna, after their initial 440L use.  If this is correct then the two arrays may have initially been on the eastern seaward side of the Ring, or elsewhere on Orfordness; however  there are no remains near to the Ring, or anywhere else on Orfordness to support this idea.  (Note that 65/66 degrees from Orfordness is aligned to cover western Russia, as was Cobra Mist on almost the same bearing; including the Missile Base at Plesetsk near to Archangel).

Alternatively; the bearing of 65/66 deg. with an array coverage of 90 deg. includes all of the Japanese 440L transmitting sites within its northern aspect.  The southern aspect of 90 deg. of coverage on a center bearing of 65/66 deg. covers from Borneo to West Africa.  This is for the two arrays, the log periodic antenna may not have had anything like 90 deg. coverage.  So if what is shown on the O.S. aerial photograph (my fig 3) is to do with System 440L, not preparations for Cobra Mist, then the arrays would have been for receiving and the log periodic array for transmitting with a narrower coverage (Chirping?) - but not apparently directly toward any known 440L site. Therefore it is possible that the arrangement shown on the O.S. aerial photograph (my fig 3) was that of the first English operational 440L site, and that this site was moved elsewhere as Cobra Mist was constructed.  In this case the Ring had none, or only minimal, connection with Cobra Mist - as stated by Professor Shearman.

Looking again at fig 3, there are remains of the western linear array on the ground at Orfordness. There are no remains of the eastern array at all.








This sketch is my idea of how the Ring-crossing log-periodic antenna might have appeared.

This drawing is derived from fig 4-2, page 53 of 'Advances in Bistatic Radar', it shows how the arrays might have appeared. (Please note acknowledgment)
       
I think that angled arrays similar to the above, my fig 5, may be seen at the Southern Italy 440L site using Google Map/Satellite.




Mapping Bearings 1, 2, & 3:






This map shows my Bearings 1), 2) & 3) as black radial lines.  440L sites are shown as a large red dot - 4 transmitter sites in the far east, 5 receiver sites in Europe.  The area enclosed by the large and small red dots is the possible coverage of  System 440L. The purple dots indicate the coverage of Cobra Mist taken from the Cobra Mist Report Part 1, fig 2.  Note that there is some correlation between the three bearings, the coverage area of System 440L, and the coverage area of Cobra Mist.  Note also that each bearing is assumed to have approximately 90 degree coverage.



Analysis of my three bearings:

My Bearing 1) - 17 degrees, covers all the far eastern transmitting sites in its southern aspect.  The northern aspect is of interest because it includes two locations associated  with ionospheric observation - Spitzbergen and the Bering Sea Islands, and also seems to share the northern boundary of Cobra Mist coverage.  A possible 440L ring at Okinawa, Japan also may have a ring-crossing log-periodic array, on an approximate bearing of 10 deg.  And the linear arrays at the English 440L receiving site (not Orfordness) are aligned on 30 deg. the northern aspect of which would have covered from Japan to Alaska approximately.  The U.S.S.N. ship Observation Island has been associated with North Pacific observations concerned with nuclear weapons tests and thus might be considered as a speculative Tx/Rx from/to England or Okinawa.  But there is nothing which merits a firm conclusion from any of these northern aspect bearings/locations or my speculations.   What can be said is that consideration of the northern aspect coverage of the England/Okinawa(?) sites may possibly indicate a northern functioning of System 440L not obvious from the published information which I have used.

The bearing of my Bearing 2) - 116 degrees,  is similarly of interest because it covers four of the System 440L European receiver sites and seems to coincide with the southern boundary of Cobra Mist coverage.  But even 110 deg. steerability is insufficient on this bearing to transmit to any of the System 440L far eastern transmitting sites.  Also, logically, the antennae at the four European System 440L receiving sites which are coverable on this bearing, would be directed eastward.  The whole of the association of this bearing with System 440L as described (see previous) is backwards.   But later I shall speculate that this bearing may have been part of a System 440L intention to have greater southern coverage than shown in my System 440L Description coverage map.  Or perhaps this bearing is an aspect of System 440L that I have not understood or misinterpreted. 

The bearing of my Bearing 3) - 66 degrees,  is approximately the same as the center bearing of Cobra Mist - 65 degrees; and I deduced that it is possible that my, presumed, log-periodic antenna crossing the Ring on this bearing was a pre-construction test for Cobra Mist.  For this deduction there is some small physical evidence as I found several short lengths of Cobra Mist antenna-rod in the shingle inside the Ring.


Also, Gordon Kinsey in 'Orfordness Secret Site', page 119, second paragraph, writes " .... a small trial installation, code named POUND NOTE, had been evaluated near the old R.A.F. Station.  The aerial system for this scheme was comprised of large areas of wire netting". This quote could add weight to the idea of a pre-construction trial for Cobra Mist, but the description and location do not fit the Ring and a log-periodic array.  Also I have been unable to find any trace, U.S. or U.K. of the code POUND NOTE.

But against the whole Cobra Mist preparation idea is the possible presence of a ring-crossing log-periodic antenna on the possible 440L ring at Okinawa Japan.  This antenna is on a bearing of 10 degrees, pointing northward, across far eastern Russia and on to the extreme north of Canada; or southward toward Western Australia.  If my reading of this satellite photograph is correct and the ring on Okinawa was a 440L ring; then it could be deduced that  log-periodic arrays were used as a component of  System 440L.  And this is feasible as the 440L description in 'Advances in Bistatic Radar' , page 53, para. 3 refers to "... Barry Chirp Sounders .... were used at both ends of the (440L) links....".  And I presume that log-periodic arrays could be used for chirp-sounding (H.F. pathfinding) because of their wide bandwidth. (Development of pulse-compression 'chirp' - Barry & Fenwick, Stamford, 1971).  Therefore if the Orfordness Ring-crossing log-periodic of my Bearing 3 was being used for chirp-sounding then my association of fig 3 with Cobra Mist is wrong, and Professor Shearman is correct in his assertion that the Ring had nothing to do with Cobra Mist.  Note that the center bearing of the two (440L receiver) Orfordness arrays, and the log-periodic antenna, at 65/66 degrees with a 100 deg. array steerability - from Kamchatka to the Horn of Africa, would cover reception  from all the far east 440L transmitter sites. Therefore such an arrangement of 440L receiver arrays plus log-periodic 'chirper' on a center bearing of 65/66 deg. is probably practical, although this bearing is not aligned directly with any known to me 440L far eastern site.  (See the map at the head of this section showing the 17, 65, and 116 degree alignments from Orfordness)

Note: I think that the two angled linear arrays to the north of the Ring in my fig 3 are 440L because of their similarity to the arrays shown on my figs 3 & 5 derived from 'Advances in Bistatic Radar', page 53, fig 4-2; and also their similarity to the angled array, the remains of which can be seen using Google Map/Satellite at the Southern Italy 440L site. 

Lastly it might be worth thinking about what could be achieved by realistic pre-construction testing for Cobra Mist and some of the problems involved.  Re-using 440L equipment would only allow an unmodulated C.W. signal to be transmitted.  However the weak O.T.H. backscatter signal from a C.W. transmission might be obscured by breakthrough from a co-located C.W. transmitter.  The same problem would occur with FM-CW transmission.  In either case quite complex mechanical/electronic equipment might be necessary to reduce co-located Tx to Rx breakthrough to an acceptable level.  (Note, in some large FM-CW O.T.H. radars the transmitter and receiver were  physically separated to overcome this problem - Bistatic operation ).   Cobra Mist used Coherent Pulse Doppler technology requiring high transmission power and complex receiver processing.  Like straightforward Pulse Radar, Pulse Doppler Radar Tx/Rx may be co-located, as the protection of the receiver from the transmitter is much simpler for Pulse than C.W. transmission.  For a Cobra Mist pre-construction test it might have been possible to use a simplified  Pulse-Doppler transmitter/receiver, which would have eliminated the Tx/Rx breakthrough problem, and made possible the realistic testing of one Cobra Mist type log-periodic element;  transmitting from the Ring-crossing log-periodic, receiving on the two ex 440L arrays.  But why go to all this trouble?  Cobra Mist was built by  the U.S.A.F. and is said (Cobra Mist Report) to be based on the successful M.A.D.R.E. monostatic O.T.H.R.  Why should pre-testing at Orfordness be necessary?  Except perhaps for some particular Cobra Mist component?  And perhaps the only such component which could have been easily tested is the log-periodic antennae, eighteen of which formed the Cobra Mist Array, and perhaps a sample of which was the Ring-crossing log-periodic of my fig 3?   If U.S. experience  did not then include the use of log-periodic antennae for H.F. O.T.H.R. use (M.A.D.R.E. did not use log-periodic antennae.  W.A.R.F. did use log-periodic antennae) then such a test at Orfordness might have been considered desirable - perhaps to evaluate construction difficulties.   

So a case can be made either for what is shown in my fig 3 to be an experimental or operational facility for for System 440L; or to be a pre-construction test facility for Cobra Mist.  The equipment shown in my fig 3 is entirely compatible with System 440L - the two receiving arrays and the log-periodic for 'chirping'; only the bearing of 66 deg., virtually the same as the center-bearing of Cobra Mist is thought-provoking.  The case for Cobra Mist pre-construction testing is supported by this 66 deg alignment, the same as the center bearing of Cobra Mist as built, and my finding of several short lengths of Cobra Mist antennae rod inside the Ring; but the technical difficulties in using the arrangement of my fig 3 as a pre-construction test for Cobra Mist are considerable, and the value to be gained from such testing questionable.   Perhaps there is some other explanation of my fig 3 which I have missed?  Alternatively what is shown on the 1965 O.S. photograph (my fig 3) may have been the first English 440L operational site, after the use of the Ring for European research but pre-dating Cobra Mist.  This English 440L operational site may have been moved elsewhere (not Orfordness) as Cobra Mist was constructed - there is evidence for such a move.  If this is so then the Ring had none, or only minimal, connection with Cobra Mist - as stated by Professor Shearman.



Transmitter/Receiver coverage:

A perplexing aspect of this investigation is the apparent difference between the angular coverage necessary - 30 degrees;  for all the known 440L transmitter sites to transmit to all the known 440L receiver sites (and vice versa theoretically), and the angular coverage of approximately 100 degrees provided by the transmitting 'rings' (my measurement) and the two phased receiver arrays. (From 'Advances in Bistatic Radar', page 53, fig 4-2.)

Looking at the Google Map/Satellite pictures of the Philippines transmitter site; two rings can be seen each having six black dots equidistantly arranged around approximately one third of the ring circumference facing toward Europe.  I assume these six dots to be part of the rigging of the imbricated rhombic transmitting array.  If  GcmWin Freeware (Acknowledged with thanks) is used to plot and mark the great circle path from the center of a Philippines 440L ring (I used the larger of the two rings) to each European receiver site
(five great circle lines); then it is apparent that the aspect covered by only the northern three of the black dots is needed.  The aspect covered by the unused southern three black dots is centered to the south of  Europe, towards Africa.  The total arc from the southernmost to the northern most black dot is 110 degrees.  This might, approximately given the crudity of my measurement, represent the angular coverage of, at least the Philippines, and possibly all System 440 L transmitters - it would be logical for the transmitters to have the same angular coverage as the receivers.

 



Using the same technique at the Southern Italy 440L site, as used at the Philippines site;  it can be easily seen that the receiver aspect necessary to receive all four eastern transmitter sites needs only one receiver array only - the northern array.  The southern array seems to be disused, though this is debatable as the Google Map/Satellite picture must postdate the abandonment of the Southern Italy 440L site by many years.





From these crude measurements it would seem possible that as designed the rectangle of System 440L coverage was intended to extend farther to the south than as shown on my coverage map  (see System 440L Description).   An additional transmitter site at Christmas Island and a receiver site in Oman would have probably been feasible but these would not have occupied all the possible coverage.
 
The next map illustrates a possible southward extension of system 440L.  But note that the southern aligned arrays at the Philippines and Southern Italy sites seem to have become disused before the northern aligned arrays.  Does this mean that the southern aspect of System 440L was tried then abandoned?  Or was the southern aspect of 440L built but never implemented?

      

The African-pointing bearing of my Bearing 2) - 116 degrees is also relevant.  Could this be evidence of experimental work at Orfordness on this bearing - which does pass through Oman?  Is it possible that there is more to System 440L, and/or more to the Orfordness Ring, particularly with regard to this southern aspect than I have been able to deduce?



Similarly, considering my Bearing 1 (previous) and the three northern alignments:  17 deg. at Orfordness, 30 deg. at the 440L English Rx site, and 10 deg. at Okinawa.  It could be speculated that the rectangle of System 440L coverage was intended to extend farther to the north than shown on my coverage map (See 440L description).  In the next GcmWin Freeware map I illustrate this possibility with speculative sites in Northern Canada and the Bering Straits.




                                                                             --------------------------------------------------

Conclusion:

I deduce that the Orfordness Ring was built in 1963/4 as an experimental, then possibly operational, facility for System 440L when the research work for System 440L was moved from the U.S. to Europe in 1964.  (See 'Advances in Bistatic Radar', page 52, last paragraph).  I think that a 440L 'imbricated rhombic array' (See 'Advances in Bistatic Radar', page 53 para. 3) was built on the Ring, driven by the transmitter on the Platform behind the Ring; and that twin 440L linear phased receiving arrays (See 'Advances in Bistatic Radar' page 53, fig 4-2) were erected somewhere on Orfordness.   It would have been possible to adjust the configuration of these transmitting and receiving arrays on and around the Ring.  I think it possible that this facility was used to set-up the far eastern transmitter and European receiver components of System 440L and to explore the possibility of extending the coverage of 440L southward and northward.  Note that after 1968 System 440L was used to detect nuclear weapons tests for U.S. A.E.D.S.; perhaps the Ring was also used experimentally in connection with this addition to System 440L capability - would this fit in with northerly/southerly additional cover?  Alternatively what is shown on the 1965 O.S. photograph (my fig 3) may be the first English operational 440L site; after the Ring had been used for 440L European research and before Cobra Mist.  This operational 440L would have been moved elsewhere (not Orfordness) as Cobra Mist was constructed - there is evidence for such a move.  In this case the involvement of the Ring with Cobra Mist would have been none or minimal - as stated by Professor Shearman.

Or it is possible that after the initial 440L research/maybe operational use the 440L Ring facility was reused to carry out an evaluation of one log-periodic element of the Cobra Mist array during the Cobra Mist pre-construction phase.  This might have involved moving the 440L receiving arrays to a position to the north of the Ring, where there are remains on the ground today, and constructing a 'sample' Cobra Mist log-periodic element across the Ring.  Perhaps this, maybe the last H.F. operational use of the Ring, was controlled from the small building(?) marked in red on my fig 3.

Later the Ring may have been used for other non- H.F. purposes.

It can only be said with confidence that the Ring was associated with U.S. 440L Forward Scatter System.  This because I have found rings similar to the Orfordness Ring at 440L locations in Europe and the far east; and one of the far eastern rings is aligned on 440L Europe. Likewise I have found arrays similar to the 440L arrays described in 'Advances in Bistatic Radar' at Orfordness and Southern Italy, the later aligned on 440L far east.   And both arrays and rings compare positively with the photograph - fig. 4-2, page 53, and description - page 53, para 3 of 'Advances in Bistatic Radar' which book on pages 52/3 describes System 440L.  These comparisons have largely determined my conclusion.

However the puzzles of: research/operational use, possible involvement in Cobra Mist, and the possibility of additional 440L coverage remain.

My experience of historical research is that it is not unusual for conclusions to be few and ambiguity to be great.  Hence my distrust of nearly all history textbooks.   Perhaps the objective should not be to find a conclusion but to record, and increase understanding.  I hope that this effort will help to do just that and encourage others to progress this fascinating study further.



The sources used to make this website are as follows:


My own research 2006 to 2009

My own photographs and measurements of the Ring taken 7/6/2008

Help & assistance from Mr Paddy Heazell, National Trust


Books:

'Advances in Bistatic Radar', Ed. Willis & Griffiths, Published SciTech, U.S.A. 2007
Chapter 4, 'Missile Attack Warning' written by Edwin Lyon 111; pages 52-54 (Read with army.history websites - below)

'Suffolk's Defended Shore', Hegarty & Newsome, Published English Heritage 2007
Page 85, Reproduction of Aerial Photograph OS/65054 V108 30-APR 1965

'Orfordness Secret Site', Gordon Kinsey, Published Terence Dalton, 1981.  (Pages 98 to 115)


Websites:

www.history.army.mil/html/books/bmd/BMDV1.pdf  (page 241)
www.history.army.mil/html/books/bmd/BMDV2.pdf  (pages 225 - 230)
Purpose and deployment of 440L. (Read with 'Advances in Bistatic Radar' - above)

www.fernblatt.net/m3.html#a0512
AN/FRT-80 (440L transmitter - 20 X 5-28MHz) (440L receiver said to be AN/FSQ-76)

http://ir.lib.u-ryukyu.ac.jp/bitstream/123456789/446/7/gabe_06.pdf
History of HQ U.S. Forces Japan 1975 - 440L Termination (page 77)
   
www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB7/nsaebb7.htm
Alterations to System 440L at U.S. Air Base, Italy, for A.E.D.S., 1968 (Document 12)

www.spyflight.co.uk/cobramist.htm
First paragraph re U.S.N.S. Observation Island off Kamchatka Peninsula (Unverified. No source quoted).

www.msc.navy.mil/factsheet/t-agm.htm
U.S.N.S. Observation Island

www.globalsecurity.org/space/facility/shemya.htm
U.S. Air Base Shemya Island

www.dumka.us/Shemya-1.html
Map of the Aleutian Islands

www.globalsecurity.org/space/library/report/2001/x-band_radar.htm#A%20Brief
U.S. Air Station - Shemya, Aleutian Islands

http://en.wikipedia.org/wiki/St_Lawrence_Island
History/Maps of St Lawrence Island, Alaska

www.geckogo.com/Guide/Svalbard/Spitsbergen/People-Culture/History/

www.russianspaceweb.com/plesetsk.html
Plesetsk Cosmodrome, Archangel, Russia

www.globalsecurity.org/space/systems/bmews.htm
Dates of B.M.E.W.S. Radars

http://www.google.com/gwt/n?u=http%3A%2F%2Fwww.globalsecurity.org%2Fspace%2Fsystems%2Fan-fps-95.htm
Summary of Cobra Mist and reason for discontinuation

www.cufon.org/cufon/cobramst.htm
(Parts 1-4) U.S.  F.O.I.A. Report on Cobra Mist.  (Professor E.D.R. Shearman, Birmingham University, U.K.; Vice Chairman).  Part One of this report contains a history of Cobra Mist also a full Technical Description and Specification of the Cobra Mist transmitters and receivers, complete with photographs and diagrams, including a coverage map - fig 2.

http://www.dod.mil/pubs/foi/reading_room/480.pdf
The Enigma of the AN-FPS95 O.T.H.R.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD529743&Location=U2&doc=GetTRDoc.pdf
The effect of Meteors on O.T.H. Radar

www.dtic.mil/cgi-bin/GetTRDoc?AD=529085&Location=U2&doc=GetTRDoc.pdf
Description of one-way tests from the Mediterranean to Cobra Mist.  See Page 1, para 1 & Page 2, para 3


Also:

The Journal of the Airfield Research Group, No. 83, July 1999, page 20
Relevant to the English 440L receiver site


Background information:

David Farrant's excellent website: www.century20war.co.uk, for a comprehensive overview of the Orfordness site.

www.ottawa.drdc-rddc.gc.ca/docs/e/TM-2006-285-eng.pdf
A Canadian Perspective on HF O.T.H. Radar, R.J. Riddolls - (This excellent paper is no longer available via I/N)

http://www.dsto.defence.gov.au/attachments/The_development_of_over-the-horizon_radar.pdf
The Development of O.T.H. Radar in Australia, D.H. Sinnott

www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA445505&Location=U2&doc=GetTRDoc.pdf
The Development of O.T.H.. Radar in the U.S.A.,  J.F. Thomason

Radar Handbook, Ed. Merrill Skolnik,  Second Edition, McGraw-Hill 1990


For Mapping, acknowledgment & thanks to:

Google Mapping/Satellite imaging

GcmWin Freeware:  Location-adjustable Great Circle Globe Maps

O.S. Explorer Map No. 212 - Woodbridge & Saxmundham


Abbreviations used in the text:

A.E.D.S.        United States Atomic Energy Detection System
B.B.B.           Bomb Ballistic Building (Orfordness)
Bistatic          Transmitter and Receiver  separately located
B.M.E.W.S.   Ballistic Missile Early Warning System
C.W.              Continuous Wave (transmission)
deg.               degree (bearing)
FM - CW      Frequency Modulated - Continuous Wave (transmission)
F.O.I.A.        Freedom Of Information Act  (U.S.A.)
H.F.              High Frequency 3 - 30 MHz
m                  meter
M.A.D.R.E.  Magnetic Drum Radar Equipment (U.S.)
MHz             One million hertz (cycles) per second
Monostatic   Transmitter and Receiver at the same location
N.O.R.A.D.  North American Aerospace Defense Command
O.S.              Ordnance Survey (U.K. Mapping)
O.T.H.          Over The Horizon
O.T.H.R.      Over The Horizon Radar
O.T.H. - F    Over The Horizon - Forward Scatter
R.A.F.          Royal Air Force (U.K.)
R.C.S.          Radar Cross Section
Rx                Receiver
Tx                Transmitter
U.K.             United Kingdom
U.S.A.          United States of America
U.S.N.S.       United States Naval Ship
W.A.R.F.     Wide Area Research Facility (Stamford University, U.S.A.) 

Notes:  'Ring' (with a capital letter) = the Orfordness Ring.

Following from 'Advances in Bistatic Radar' pages 52/3 the five European 440L sites are referred to herein as 'receiving' sites; and the far eastern 440L sites are referred to as 'transmitting' sites, although it is possible that all the sites could transmit and receive.  (See System 440L description below).



Author of this website:  Geoffrey Taylor C.Eng M.I.E.T.
Contact:  geoffrey.jefftee@gmail.com


Website made using the Nvu html code generator, checked using W3Markup Validation service.  FTP by File Zilla.  Hosting by 123-Reg.co.uk.  Acknowledgment and thanks to all these website-making facilities.


 




Amendments:

30/11/09 - Abbreviations R.C.S. & O.S. added.  Acknowledgment O.S. 212 added.

20/12/09 - Acknowledgment Airfield Research Group added.
Alterations throughout the text to clarify re English 440L receiver.
'Description' - Revision re transmit/receive numbers details, also Note re assumption; arrays Rx, rings Tx.
Revision of wording of  'My Bearing 1' to clarify re northern aspect.
Globe 'Map illustrating Bearing 2' revised to clarify coverage shown.

30/12/09 -  Alterations to conclusions re. possible use of Orfordness Ring-crossing log-periodic antennae for System 440L or for Cobra Mist, with particular reference to difference in transmission methods: 440L - CW; Cobra Mist - Pulse Doppler.

20/1/2010 - Opening altered to place text before picture.  18/2/2010 - opening picture removed.

18/2/2010 - Sources info. moved from beginning to end of website.

22/2/2010 - Acknowledgment 'National Trust' added after 'Mr Paddy Heazell'.

28/2/2010 - Acknowledgement David Farrant added.

2/3/2010   - Website Sources converted into links.

5/4/2010   -  Amendment of 20/1/2010 reversed i.e. opening picture restored.
Colours added to Bearings 1,2,3.

14/4/2010 -  Amendments throughout the script to give greater emphasis to the possibility that what is shown on the 1965 O.S. photograph (my fig 3); may be the first English 440L operational site.
Four additional websites re Cobra Mist.

3/5/2010  -   Linked Index added

16/5/2010 - Author name added to introduction