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Baddow at War

Page history last edited by Alan Hartley-Smith 2 months, 3 weeks ago


The Interservices Ionosphere Bureau

These are details of the work carried out during WW2 by the research staff together with the drafted personnel from the Services particularly related to the Interservices Ionosphere Bureau established at Baddow. This provided data about the reflecting layers of the ionosphere, and was under the scientific direction of Mr.Eckersley and Mr. Tremellin. It was manned by Wrens for training and analysis of D/F work, and by RAF operators for measurement work. It provided data on which forecasts of frequency to be used by various wireless services throughout the world were based; it predicted magnetic storms or enabled them to be predicted, and in general provided a short-term preview of wireless conditions, and also assisted other organisations in devising ways and means of extracting the maximum of information from the intercepted signals. 


An initial article is here and an extended version with further detail is here, (first published as a combined article in Eden the journal of the Defence Electronics History Society) having made contact with a user based in New Zealand, who operated during the war in the Far East and has a a large collection of period equipment, so we now have pictorial material. 


A reference was found to the participation of Wrens in the Greenhill book "Bletchley Park's Secret Source - Churchill's Wrens and the Y Service in World War II" written by Peter Hore. On page 163 it has a sentence "The eight (Wrens) were sent in a truck to a Victorian house in Beehive Lane, Chelmsford, which had become a wrennery for sixty women. From there they cycled or walked to the Marconi Works, for more lectures, this time on the ionosphere, Heaviside layer and radio carrier waves." There follows a description of their subsequent posting to a Y Service station where they carried out the duties of "radio-finger-printers". (AHS note - I think the "Works" reference actually means Baddow which is within easy walking/cycling distance from Beehive Lane.). The WRNS history by M H Fletcher talks of an eight-week course for Wrens with the job title of Classifier.  That is normally related to RFP/Tina but the book states that this course was to train them in the “observation of the ionosphere and analysis of W/T transmissions”.  That must have taken place at Marconi Chelmsford which was the only location with the specialist knowledge and equipment.


There was also another Baddow group set up under R J Kemp to design and construct apparatus to implement the Propagation Group's findings for the Y Service and the military units, and which was ultimately assigned control of part of the operational intelligence service.


The hut occupied by Eckersley and his propagation team in 1938 was still in use by the current generation of propagation specialists in 1985! It survived until the second building housing new laboratories and drawing offices was built.


We have recently discovered the following details of the full involvement of the Company.


HW41/401 - a set of lists of UK Y stations - Y Stations lists and locations Oct 1941 to Aug 1945


All references to Chelmsford, Bedells End and Ford End are Naval. None feature in RAF, WO or FO lists.


11/10/41Chelmsford Postal address Bedells End, N. Chelmsford Map ref M124272 Sole mention of Bedells End in file.(Chelmsford)


17/12/41Chelmsford Now designated "Experimental D/F", linked to Marconi and Baddow? 

                 RAF site at Kingsdown is also Experimantal D/F. No others are designated like that.


12/1/42 -   Chelmsford Q - The Q indicates a research site. No others are designated Q at that time


25/6/42 -   Chelmsford Q - Now listed as inter-service rather than just Naval. Only station to have that tag. Link to Baddow and the IIB at        

                                                   Baddow? The change to inter-service ties in with the setting up of the IIB which links Chelmsford to Baddow.


10/5/44 -   Chelmsford Q - Abbotscliffe and Ventnor both designated as Q. However Chelmsford is always only Q, the other two are N, O, P as well as Q

                                                   M=Main Intercepting. N=D/F. O=VHF Intercepting. P=Non-Morse Intercepting. Q=Research


12/6/44 -   List of all stations - Chelmsford Q - M124272 Note - the Chelmsford site is listed separately to Ford End

                                             Ford End  -  M102352 - HF/DF Group Appears without prior mention - no other similar group listed 

                                             (Chelmsford) - M10535 -  covers six map refs




                                             M121344 Control Room


It is likely that the Chelmsford sites and Ford End were members of a DF Group, one of a number set up to improve results by using multiple bearings taken on the sme target - see below. This whole topic is the subject of a specific study.


Additional suppositions

Chelmsford was not a normal operational Y or D/F station. It might well have functioned as that but only as part of its experimental research work. That research must have been at Marconi and involve Baddow. However there is no solid proof for but it is hard not to draw that conclusion. The timing of the change to inter-service fits with the IIB being set up.


This map shows the probable location of the Bedells End Y site on the Roxwell Road out of Chelmsford (roughly opposite the blue line). It was said that Eckersley found the place looking for a "quiet" site, cycling round Chelmsford with an aerial wrapped round his chest and a receiver on his luggage rack. In 1956 there was still a hut located in the centre of a rhombic array where HFDF research was being carried out by Dennis Byatt. The main Marconi Writtle site was located further down Lordship Road near the village. (On a personal note, I have never forgotten my early days at Bedell's End. A year or so ago on a visit to Chelmsford I drove out along the Roxwell Road - there was no trace of either site but I went up the track and got out into the field - the crop was coming up just as it did in those days - and I felt something stir in the air like a ghostly array but it must have been the wind.)









The Ford End HF/DF group suddenly appears in June 1944 using five sites, approximately marked in blue, with the red marker at the Control Room. The actual air shot shows a more accurate layout, with the locations marked in red.




In February 1945, the Ford End group used aural sets Marconi DFG 24. Details of similar kit are on page 345 in this catalogue entry, and we have now found other references from an installation in New Zealand. The duration of five-group contact signals (about 25 seconds) meant that they were not too difficult for the Marconi aural sets to fix. Aural equipment was generally operated by skilled civilians (members of the Civilian Shore Wireless Service (CSWS). British research had indicated that plotting the mean bearing of four or five grouped stations should improve performance – a hypothesis supported by results from the other armed forces. 


Averaging bearings over space was an attempt to compensate for the fact that naval signals were often too short to apply any averaging over time. Following a proposal in April 1943, groups of five stations were therefore established at Anstruther (Fife, Scotland), Bower (near Wick, Scotland), Ford End (near Chelmsford) and Goonhavern (Cornwall), and in Iceland: one station in each group was held as a reserve. In practice, results from group stations were disappointing, for reasons that were still not fully understood in 1946 despite in-depth statistical studies. However, group stations led to some increase in accuracy, since it was easier to supervise and train their operators and maintain their equipment than on widely scattered sites. 


High-frequency direction-finders (operating on a frequency band of 1.5 to 30 Mc/s) were used extensively during the war for shore station d.f. networks. The aerial system employed was almost exclusively the buried-U Adcock type. The main considerations for using this type of aerial system were as follows:-(a) Small polarization error.(b) Wide frequency-band coverage.(c) Adequate sensitivity.(d) Suitability for use either with radiogoniometers or cathode-ray type direction-finders for rapid bearing indication.The main developments in h.f. direction-finding were in the reduction of polarization error by the use of earth screens, and an attempt to reduce phase interference effects by ray-separation technique. Improved methods were also been devised for aerial balancing and for compensating for instrumental irregularities. In this connection an internal injection method was developed for checking the overall balance of aerials, feeders and radiogoniometers, especially for use on sites where an external local calibrating transmitter was unreliable. Attention was paid to improvements in design of radiogoniometers, and instruments were developed for injecting calibrated voltage ratios into the field coils for laboratory checks of instrumental performance. A special type of local calibrating transmitter was developed which employed frequency modulation for rapid local calibration checks and more especially for sense circuit calibrations. This proved extremely useful in detecting minute aerial irregularities occurring over narrow frequency bands.An investigation was carried out into the operational performance of various d.f. systems on all classes of traffic. A comparison was made of the merits of visual and aural presentation and their effect on accuracy, speed of operation, flexibility and simplicity of maintenance.


A typical war time HF unit equipped with Marconi DFG 24 Direction Finding sets is shown in the first picture below - each unit would possibly have had four personnel working watches, one man on duty at a time. Both huts would have required power from an outside  source, usually a generator,  and have had the means to pass on significant data rapidly (phone/radio). Apart from a receiver the hut would have been equipped with an item called a goniometer, the large circular display in the centre of the second picture.


Details of other installations are being built up and will be added when completed. 




Recording kit designed and manufactured by Marconi



 Additional sources


CARS meeting here


A further article on the Chelmsford involvement


List of reports produced by the Bureau  

Centimetre waves effects of refraction; Eckersley T L; Air Ministry Great Baddow Research Laboratories; March 1942; TR/434; RAF 5
The investigation of horizontally and vertically polarised direction finding of frequencies of the order of 20 to 70 megacycles per second; Eckersley T L; Air Ministry Great Baddow Research Station; September 1942; TR/451; RAF 5
Short wave direction finding; Eckersley T L; Air Ministry Great Baddow Research Station; 1942; TR/454; RAF 10
The calculation of oblique-incidence transmission; Cox J W; Baddow Research Laboratories; November 1942; TR/434; RAF 11
1 to 10cm propagation curves; Millington G; Baddow Research Laboratories; January 1943; RD 460; RAF 19
Abnormal region-E ionisation; Eckersley T L; Air Ministry Great Baddow Research Station; March 1943; TR/464; RAF 13
Non-linear theory of wave propagation; Millington G; Baddow Research Laboratories; March 1943; RD 580; RAF 45
Transmission over ground of varying earth constants; ; Air Ministry Great Baddow Research Station; July 1943; TR/473; RAF 23
The LORAN system; Eckersley T L; Air Ministry Great Baddow Research Station; 8 September 1943; TR/475; RAF 28
Scattering; Eckersley T L; Air Ministry Great Baddow Research Station; November 1943; TR/481; RAF 49
The effect of the geomagnetic field on electromagnetic waves vertically incident on the ionosphere; Cox J W; Air Ministry Great Baddow Research
Station; December 1943; TR/477; RAF 34
The attenuation of short radio waves by vertical reflection from the ionosphere; Cox J W; Air Ministry Great Baddow Research Station; January 1944; TR/478;
RAF 33
The propagation of ultra-short waves round hills and other obstacles; ; Air Ministry Great Baddow Research Station; 18 November 1943; TR/479;
RAF 41
Height-gain tests in the troposphere; Isted G A; Air Ministry Great Baddow Research Station; July 1944; TR/488; RAF 39
The reflection coefficient of a linearly graded layer; Section ‘E’; Air Ministry Great Baddow Research Station; September 1944; TR/492; RAF 50
Preliminary analysis of Height-gain tests in the troposphere; L/AC McDowell R F C; Air Ministry Great Baddow Research Station; September 1944
TR/494; RAF 43
A note on the reflection coefficient of an isotropic layer of varying refractive index; Millington G; Air Ministry Great Baddow Research Station;
5 October 1944; TR/497; RAF 48
Alexandra Palace tests; Eckersley T L; Air Ministry Great Baddow Research Station; October 1944; TR/498; RAF 52

Polarisation measurements on reflected waves on 1.9 mc/s; Section ‘E’; Air Ministry Great Baddow Research Station; December 1944; TR/500;
RAF 53


Awaiting - TR456


There are also some referencing other work for the Admiralty:


A mercury-pool switch with electrostatic ignition; Baldwin Banks G; Great Baddow Valve Group; (ADM290A); December 1943; Box 2064

A wide range reflection oscillator valve (OT.48); Baldwin Banks G; Great Baddow Valve Group; (ADM294); January 1944; Box 2064


There is also an article authored by Marconi staff which is being traced:

Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication

Developments in h.f. direction-finder shore stations using Adcock aerials

Volume 94, Issue 15, March April 1947, p. 683 – 692




It should be noted that this type of activity was nothing new to Marconi - this is earlier history recorded by Bernard de Neumann.


In reading about MI6, I discovered that it's first official home was the old Marconi HQ in the Strand, and there are more connections, including that a secret RDF or Wireless Intercept Station was operated from Hall Street after the company officially moved into New Street.  (See below).


Many Marconi WW1  activities emanated from Essex.  For example the Marconi Wireless Telegraph Company of Chelmsford built and ran many radio direction finding (rdf) stations and Wireless Intercept (W.I. = Y) stations throughout the UK and elsewhere.  Bearing details from the rdf stations enabled the tracking of Zeppelin movements over the North Sea and England, making it possible to intercept them with aircraft.  The Y-stations listened into wireless transmissions and forwarded them onto the Admiralty's Room 40 for decryption, German cable telegraph systems having been cut by the British at the outbreak of war.  Many Marconi wireless officers serving aboard merchant ships were conscripted into the Royal Navy as soon as their ships returned to British ports.  Indeed, such was the contribution of Marconi's to the war effort that a history of the company's wartime activities was commissioned and written, titled 'Wireless in the War' by the well-known author Harold Begbie, but MI6 removed five chapters as publication was deemed to be detrimental to this country's interests, and so it was never published.  The remnants of the book may be found in the Marconi Archive at Oxford University, with related correspondence, 1919-20 Shelfmark: MS. Marconi 361 Extent: 1 box   Scope and Content:  Draft of the book with chapters 4, 10, 11, 12 and 15 missing, removed because of the sensitivity of the content; internal company correspondence directing adverse criticism at the draft overall; correspondence from the Directors of Military and Naval Intelligence with criticism noting material that should not be published in the national interest.

Another example is the Royal Naval Experimental Station, which was in Stratford during WW1.  Frank Brock of Brock's fireworks was one of the "brains" behind it.  He was the inventor of (i) the incendiary bullets that were used to bring down Zeppelins, (ii) the method used to generate smoke screens used by the Royal Navy in the 1918 Ostend and Zeebrugge raids, (iii) a very bright flare that was set off when in contact with sea-water (used by the Dover Patrol to force submarines to submerge in attempting to pass through the Dover Straits, thereby slowing them down and making them more vulnerable to our mine-fields); and several other chemically inspired devices.  He landed at Zeebrugge during the raid, which was to both block the entrance to the canal and prevent submarines from transiting it, and to try and discover the secrets of the "Görtz" sound ranging apparatus that was used to devastating effect by German coastal artillery.  He was the "boffin" of the raiding party, in a similar role to that of Jack Nissenthal, who dismantled and brought back to the UK parts of the German radar station at Pourville during the 1942 Dieppe Raid.  Nissenthal was accompanied by an armed guard under orders to shoot him if he fell into enemy hands!   Unfortunately Brock disappeared during the Zeebrugge raid and was never seen again."

There is much more to the story of the Marconi Co's involvement in WW1.  Although the British refer to all WW1 German airships as Zeppelins, there were also airships built by Schütte-Lanz, and both the German Navy, and German Army operated them.  The raids on England were conducted in the main by the German Navy, and initially it was the responsibility of the RN, and more specifically the RNAS, to intercept and engage with them.  Engineers in the Marconi Co quickly realised that spurious transmissions they were picking up were from Zeppelins navigating the North Sea (navigation of Zeppelins was very difficult at the time, because of lack of technology, and over the water they used to transmit some coded info to two ground stations in Germany, and from this their position was calculated and transmitted back in code).  Unfortunately for them, the Germans did not realise that Marconi's had developed a means of receiving weak wireless signals, and used this to good effect in also calculating Zeppelin positions.  H. Round, the Marconi engineer who developed the system, was awarded an MC.  The company operated a number of secret rdf and Y service stations along the East Coast, and, eventually, all around the British Isles, passing intercepts on to Admiralty Room 40.  They operated a secret intercept station in Chelmsford (Hall Street), and another in the attic of the Metropolitan Police HQ, amongst others.  After the war the precursor of the GCCS (now GCHQ) was set up in the old Marconi Company Head Office on The Strand, London; subsequently there was a strong link between the Marconi International Marine Co, and MI6, as Marconi Radio Officers could penetrate countries into which the RN, nor other official agencies of the British Government could venture.  The link continued until MIMCo was wound up in the 1980s.


Interesting link between The Royal Hospital School, Greenwich, and Guglielmo Marconi, from “The Sphere”, 11 September 1926.


Other sources being researched and it will be an ongoing task to record these and make them available for reference. 


The general area of interest, wireless monitoring, had been carried out since WW1, and an interesting reference for this has been found in chapter 6 of a book, "The Bright Sparks of Wireless" by G.R. Jessop, describing the work of the Radio Security Service, carried out by radio amateurs as Voluntary Intercepters, committed to secrecy for life, and as members of the Radio Society of Great Britain, quote "who knew all about fishing for rare signals under an overlay of noises various".  












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