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Following recent discoveries of sources of information about the WW2 ‘Y Service’, it has become possible to construct an outline description of the activities carried out at the Baddow Laboratories after they were taken over, and why by all three military services, for the duration of the war.

It has been known that Baddow became the home of the so-called ‘Inter-services Ionosphere Bureau’ under the leadership of T.L. Eckersley, but not exactly what that was formed to do, and what roles it actually played during the whole course of the war. This is now partially unearthed.

The Y Service

The ‘Y Service’ was initially formed to ‘listen-in’ on enemy radio communications, but it was quickly realised that in addition to the message content it was possible to extract further information from the identity of the sender, their manner of working, the characteristics of the method of transmission  (plain speech or morse code), the affiliation of their location and their service unit, as well as the transmission characteristics of the actual radio signals, which is where the skills and capabilities of the Baddow Bureau were called upon. This came under the banner of traffic analysis.

So a series of ‘Y stations’ were set up world-wide and equipped to monitor all German, Italian, and eventually Japanese, military units, and manned by selected personnel from all three Services, both male and female – the WAAFs and Wrens were strongly involved. By recording received signals in a variety of ways then correlating the types of extracted data over a period of time it became possible to build up a surprisingly useful  picture of the nature, disposition and intended actions of enemy forces over a wide area, frequently in advance of they themselves actioning it. That allowed the intelligence teams to make predictions on future activity. There were several principal units at which information was correlated, merged, and new ways and methods of approach devised, the output then passed on for formal and deeper examination by the Government Code and Cypher School at Bletchley Park to decipher, to enable Allied Forces to formulate appropriate defensive and offensive actions. Baddow provided very specialised services concerning the behaviour and stability of the transmitted radio signals which affected how, when and where messages could be received, from unintended recipients to advising preferential channels to monitor.

The following more detailed descriptions derive from two sources – a personal story of a player in the intelligence war, and detailed articles researched and written by a fellow member of the Defence Electronics History Society; both of these are acknowledged and credited with due thanks.

Aileen Clayton was in the right place at the right time, being fluent in German, joining the Women's Auxiliary Air Force in the summer of 1939, and becoming a major player in the Y Service. She has recorded her story, and that of her compatriots, in a book ‘The Enemy is Listening’ and it is from this publication that the following information is derived; it is commended as an essential read for anyone interested in this aspect of the war. In the book's foreword by Air Chief Marshal Sir Fredrick Rosier it is quoted as ‘a tribute to a tenacious and gifted band of men and women’ .

In addition to the main function of supplying Bletchley the Service provided local warnings of impending raids, often identifying the target and the leader of the attackers. It also assisted in radar directing, and carried out the breaking of low-grade cyphers. It was initially staffed by expert German and Italian speakers, with other languages added as the war moved to the East.

Initially the input material was WT morse traffic followed by non-morse and Radio Telephony on VHF from pilots to-and-from ground control, and air-to-air, on the 40Mhz frequency band, recording time, actual frequency, call-sign together with a translation, including the incidental and revealing informal pilot-to pilot chatter.

Their initial location for R/T interception was at Fairlight on a cliff-top in a van with telephone links, but no accompanying DF, near RAF Hawkinge. They were equipped with civilian receivers – Hallicrafters - plus an oscilloscope with a simple aerial array. There were also two main stations at Cheadle and Chicksands, and their duties were to obtain the German Air Force order-of-battle, its strength, movements and if possible intentions.

They maintained a liaison with the Royal Navy to provide R/T data from e-boats on short-wave. They later moved to West Kingsdown, and became integrated with the filter room. Recognition of previous interceptions enabled anticipatory action, and a series of new coastal intercept stations - Home Defence Units – were set up to monitor inland stations for bombers.

Cheadle was concerned with medium and high frequency W/T plus a D/F network – No 61 WU. They also monitored the presence of navigation beams on 30Mhz frequency  which resulted in more VHF traffic. These were Knickebein (crooked leg), then  X-Geraet. The Wireless Intelligence Development Unit flight then set up jamming countermeasures.

They were visited by the science team, including T.L. Eckersley, from Baddow, to assess their operation. The German central organisation expressed irritation over the apparent malfunctioning of the system and this resulted in open pilot communication which was then monitored. The disruptions caused greater use of traffic over the air and a new intercept station at was set up at Chicksands.

As the war moved away from Europe so did the Y Service having proved to be a significant player in the provision of intelligence.

Radio Finger Printing (RFP), Tina, Range Estimation (R/E)

Paul Marks is well-known to DEHS members as a meticulous investigator. In his latest research, he takes on the challenge of tracking the history of Radio Finger-Printing (RFP). This and the other additional interpretations of the intercepted signals enabled even more detailed discovery of information about the enemy. His full paper, of which this is a brief extract, has full details.

RFP was a technique developed to detect the characteristics of individual W/T transmitters, to add to other intelligence on the location of enemy units. Instigated as a laboratory project at the RN Signal School during 1938.

Tina looked at the precise Morse-keying habits of specific operators, weighted towards the Admiralty but both the RAF and the Army were involved as it had potential uses by all three services and the broader intelligence community. However, the Admiralty set the pace throughout the war.

R/E was a highly technical method of assessing the distance to a transmitter using knowledge of the ionosphere and dovetailed with direction-finding. Note – probable major interest at Baddow.

Expected purposes of these additional sources:
Navy: primary role was locate and help track mobile units – vessels. U-boats became a desired target as the scale of the threat they presented became apparent. Plus help with identifying the source of transmissions where D/F was poor, linking static sites and transmitters.

RAF: call-signs. Seems to have been more of a traffic analysis aid throughout.

Army: call-signs. Again, seems to have been more of a traffic analysis aid throughout.

Foreign Office: used to ensure that decoy transmitters for double agents had correct characteristics. The files have only rare fleeting mentions of such activity.

In each case it assisted with call-signs (creating cribs for Bletchley Park) and traffic analysis, adding to the intelligence picture.

The Y Service listening posts were either coupled with Radio Direction Finding (RDF) installations  or worked in conjunction with existing RDF inputs, and it is known that the design and manufacture of these was carried out at Chelmsford, and that their operation and use was also a major interest at Baddow. Unfortunately the timing of this investigation has come too late as the last known remaining member of technical staff from Baddow who was involved, Roy Simons, died last year. So we now have to rely on what published material we have, and in this instance the Marconi Revue is the most likely source.We have a link to a library with a large collection
( so we are appealing for volunteers to comb through these for relevant material and list this for closer examination.