HOW 'NOISE'  INVESTIGATION WAS DEVELOPED

East Coast Development

In 1941, E-boat sorties against British East coast convoys were frequent. As a result, a chain of VHF stations were set up, to monitor German VHF R/T traffic. Buildings occupying suitable sites on high ground were requisitioned. One room of ample size was equipped as a watchroom. Small supplies of receivers ordered from the United States began to arrive. Efforts were made to increase the aerial gain by the use of spaced reflectors, and frequency response was broadened by the employment of wire cage dipoles, sometimes referred to as "sausage" antennas.

October 24, 1944: Attached to the lattice mast at the Southwold station were some vertically and horizontally polarized wire cage dipoles. A physical characteristic of this antenna type are the wire spreaders which resemble the 'Star Of David'.  Horizontally polarized wire cage dipoles have been installed on the ends of the topmost yardarms.  (Imperial War Museum photo # A 26123)

This graphic illustrates the construction of a multiwire dipole antenna which is horizontally polarized. At each end of the two segments, the conductors are joined together. The outer ends are attached to support lines using insulators while the inner ends connect to the transmission line.  The antenna can be fed with coaxial cable or open wire transmission line and mounted in either a vertical or horizontal orientation depending upon the desired polarization.. (Graphic courtesy ex-RAF Aerial Erectors)

Maximum height of aerial was aimed at, and achieved by mounting the dipoles on 20 foot masts clamped to chimney breasts on the roof of the building. Chimney breasts are the brickwork or stonework  from the fire place up to the flat top on which is placed the chimney pot. As many of the 'Y'  stations were in old Coast Guard stations, the chimney breast would be the  strongest or easiest place on which to attach the bracket for the mast/aerial.  All through 1941, the enemy made full use of R/T during his sorties, and in the absence of surface-watching radar, the VHF stations were undoubtedly of great operational value. The lack of accurate and sensitive DF equipment however, continued to be felt.Owing to the heavy burden being shouldered by the Admiralty Signal Establishment at that time, it was not thought practicable to ask for the development of a special VHF DF system.

The DF Problem

Early in 1942, with  the help of Dr. H. G. Hopkins at the National Physical Laboratory, a survey of several Admiralty stations was undertaken. This resulted in the development of a DF aerial system capable of an accuracy of  +/- 3 degrees.

The euiipment was housed in an octagonal wooden tower of Air Ministry design. An open site near the main building was selected, the standard aimed at being a ‘field’ of 150 yards radius, clear of buildings, and other reflecting objects. Every VHF station was thus equipped by the spring of 1943, but although the accuracy was greater than had been anticipated, the sensitivity was considerably below that of the open dipole used with the main interception receivers. The result was that on many occasions when enemy signals were weak but readable on the  intercept receivers, they were inaudible on the DF receiver.

The loss was traced to the transformer in the aerial system, and a ‘home-made’ toroidal type was substituted as an interim measure with good results. The problem was also submitted to the National Physical Laboratory once more. Eventually a high efficient antenna transformer coupling, of the screened loop type, was produced by Mr F. Horner, which incorporated a remote controlled aerial tuning device easily accessible to the operator.

This  graphic shows the concept of an 'H' Adcock  attay. These were simply four, vertically polarized dipole antennas.	This is how the 'H' Adcock array looked in actual practice. It was mounted atop an octagonal wooden tower of Air Ministry design. The radio equipment was housed in the structure below. This was the Beeston Hill  'Y' station installation (Image courtesy Wikipedia)

Maintenance

The maintenance of the stations was carried out by experienced personnel of the Civilian Shore Wireless Service. General supervision was undertaken by technical officers on the staff of DSD who were also responsible for the siting, building and equipping of new stations. In 1943, the efficiency of the organization was greatly increased by the acquisition of suitable signal generators, output meters and frequency measuring equipment.

Records were kept showing the sensitivity figures for all receivers, which were re-aligned whenever necessary. Accurate frequency measurement was an important requirement at all shore stations, because enemy aircraft operating in separate groups used slightly different wavelengths. It was necessary therefore to ensure that bearings at two or more stations were taken on identical frequencies. The equipment used was a GEC crystal wave meter which had an accuracy to within  0.1 MHz in the range 30 to 130 MHz. With all VHF aerials, low loss feeders were used. Their  attenuation was approximately 2 decibels at 200 MHz.

Masts

In order to simplify the erection and subsequent inspection and maintenance of the dipole aerials, wooden lattice masts were erected at every station in 1942. These were 70 or 90 feet high, and in the final design,  they incorporated a balcony some 20 feet from the top, which greatly facilitated the fitting of aerials. The mast was sited as close to the watchroom as possible in order to reduce the feeder length to a minimum.

Receivers

The standard VHF receiver at all stations was the Hallicrafters S 27D (27.8 to 143 MHz). In 1941, a contract was placed with the Plessey Co. for the design and manufacture of a VHF receiver, in order to avoid complete reliance on the continued supply of American equipment. This resulted in the production of the 13 tube Plessey RL 85 receiver (27 to 84 MHz in 3 bands), which was of robust construction, and which gave very good service. Its measured sensitivity was slightly greater than the S27, but its overall performance somewhat inferior. In particular, its RF circuits did not provide such a high degree of discrimination as did those of the S27.

A few Marconi type RG 43 receivers were also used but they did not prove to be as popular with operators as the Hallicrafters or Plessey sets. This may have been due to the design of the main tuning control, which was most tiring if used for a long period. There is no doubt that the Hallicrafters S27 receiver won the  prize on practically all counts; it supported amplitude and frequency modulation and had an efficient S meter. Its main tuning drive was practically faultless with an exceedingly smooth action and an excellent vernier dial.

The Hallicrafters S27D receiver was the standard VHF receiver at 'Y' stations. The variant in the photo is unknown. (Courtesy Radiomuseum.org)

Plessey RL85 (27 to 84 MHz) receiver front panel. Click on the image to download the service manual. Note that the schematic is missing. (Courtesy Collingwood Heritage Collection)

Looking for a photo of the Marconi RG43 (Contact: jerry.proc@sympatico.ca

RL 85 in colour. Click on image to enlarge. (Provided by Clive Kidd)

HF Watch at VHF Stations

A subsidiary W/T watch was kept at most VHF stations, chiefly in connection with transmissions from enemy coastal W/T stations and vessels concerned with Harbour defence. The VHF stations were favourably placed for the reception of these transmissions and in general special aerials were not necessary. The receivers used were the National HRO, the Hellicrafters SX 28 and the Admiralty Pattern  B29.

HRO receiver  (Photo by Andre Guibert)

SX28 receiver (Courtesy Western Historic Radio Museum)

B29 receiver (Photo by Ray Robinson VK2ILV)

Receivers used for the HF watch at 'Y' Stations

Facilities Provided For Non-Morse Investigation

Although this history is mainly concerned with the reception of German R/T, the technical record would be incomplete without a brief description of the facilities provided at VHF Stations for ‘noise’ investigation. This equipment was serviced and maintained by the VHF technical staff at certain stations which were of a dual purpose nature. Early in 1942 it became evident that a Naval watch for signals of a non-Morse character was essential. Included in this category were the following types of enemy signals:

• Radar transmissions
• Navigational beacons
• High speed communications
• Radio teleprinter links
• IFF Transmissions (Identification friend or foe)
• Electronic navigational aids
• Jamming transmissions
• Meteorological balloon transmissions
• Guided missile transmissions

Noise investigation involves the use of a wide assortment of equipment and presents many problems which are not encountered in ‘Y’ work. A ‘noise’ station had to be equipped so as to cover the complete range of frequencies from M/F to UHF.  It should be able to DF any signal heard; and it should be able to record and photograph any signal. Most of the identification was done visually rather than aurally -  i.e. by the use of a cathode ray oscilloscope. In addition, it was essential that the audio frequency be measured, and the polarization of the transmission determined.

A start was made at the Abbot's Cliff ‘Y’ station, near Dover. A small watchroom was equipped with the limited amount of gear available at the time and operated by a few Wren W/T operators who were gradually trained in their new duties by civilian representatives of the Admiralty Signal Establishment. Aerials  used at this time were plain dipoles and dipoles with corner reflectors. A jacking system was employed to enable the DC or AC output of any receiver to be viewed on an oscilloscope.

After some months it was evident that further ‘noise’ stations were necessary, and accordingly ‘noise’ watchrooms were provided at the Ventnor and Southwold ‘Y’ Stations. Additional equipment was becoming available, and it was possible both to make recordings and also to photograph any transmission. These three stations, at Abbot's Cliff, Ventnor and Southwold produced a mass of data for subsequent analysis, and eventually Admiralty approval was given in June 1943 for the building of four ‘Y’ and ‘noises’ stations. The sites chosen for these were at Southwold, Abbot's Cliff (near Dover), Ventnor, IOW and Coverack, Cornwall. It will be seen that four of the stations were suitably placed to provide coverage of the French, Belgian and Dutch coasts.

The buildings and layout, designed in specification DSD9 were standardized as much as possible. The accommodation consisted of:

* Noise Watchroom (approx 28’ x 16’)
* Main Building ‘Y’ Watchroom (approx 20’ x 16’)
* Test and Maintenance room
* Photographic development room
* Office
* Toilet facilities
* Emergency supply power house
* D/F Tower - 30 to 100 MHz with vertical polarization of antennas
* Two  D/F Huts - 100 to 600 MHz  - with vertical and horizontal polarization of antennas

Aerials

The standard VHF and UHF aerial system consisted of multiwire, centre-fed dipoles . Four aerials provided coverage in the 30/60 MHz, 60/120 MHz, 120/240 MHz and 240/480 MHz bands  These were vertically polarized. In addition, four horizontal aerials covering the same ranges were also used.

The H/F system was supported between four 70 foot lattice masts, and consisted of four wideband, centre-fed dipoles covering the range 2 to 16 MHz. These were omni-directional. The UHF aerials were connected via twin feeders to an aerial exchange board, then to the receivers. The HF aerials were connected by underground coaxial cable which fed wide band amplifiers and an aerial exchange board. Thus, several H/F receivers could be used on the same aerial without cross-modulation.

Layout of Noises Watchroom

For ease of operation, it was found convenient to group two receivers together so that one operator could use either at will. Associated with each pair of receivers were a cathode ray oscilloscope, a Beat Frequency Oscillator and a small jackboard. All the controls being in reach, the operator could use either receiver and by means of the jackboard, either audio output could be selected.

The bench wiring was designed to be as flexible as possible. Each bench carried a master jackboard which enabled any desired combination of equipment to be used. A connection from the jackboards to the telephone exchange switchboard enabled a signal to be put out to the telephone line.
At Southwold, two long wire aerials were erected - one was aligned to the North Dutch and German coasts while the other was aligned to the Western coast of Norway. These HF aerials proved most efficient in practice. Their directional properties greatly improved the signal-to-noise ratio on weak signals.
 

ABBOT'S CLIFF

Abbot's Cliff location. (Image courtesy Google Maps)

COVERACK STATION

Coverack station location. (Image courtesy Google Maps)

 
EASTON BAVENTS STATION

The pin marks the actual location of the former Y station.  East Bavents is the nearest town. (Image courtesy Google Earth)

At coordinates 52°20'31.61"N,  1°41'13.48"E , this is all that remains of the Easton Bavents site as of November 2017. Just to the right of the photo is the North Sea (Image courtesy Google Maps)

SOUTHWOLD STATION

 Researcher Stuart Rayner provides this information about the Southwold station. "My interest is in the Southwold 'Y' Station.  It was located at the  most Easterly point of England. During WWII,  a Naval 'Y' (W/T or R/T intercept) station was set up in a big house overlooking the sea. It was part of a string of 'Y' Stations along the UK East and Southern coasts. These stations were manned by WRENS. Southwold was expanded in 1942 to include ‘noise’ intercepts. It was only one of four such stations The others were Abbot’s Cliff (Dover), Ventnor (Isle of Wight) and Coverack (Lizard Peninsula). In 1943, new watch rooms were built not far along the coast at Easton Bavents. One watch room was designated  'Y' and the other 'N.

Southwold station location. (Courtesy Google Earth)

Floor plan of the Southwold station as drawn by Stuart Rayner. Download image to enlarge.

At the Southwold station, the 'Y'  hut contained the Y watch room, the test/ maintenance room and an officers room. The huts were linked with a single entrance having wash facilities between. The 'N' hut contained just the 'N' watch room which was larger than the Y watch room and another area which was a  photographic room. There was also a large hall in this hut. One interesting aspect is that the 'noise' watch room had a Faraday Cage around it. It was the only room to be plastered  since the plaster held the wire mesh against the brick wall. It was the only room to be plastered in this manner. When the asbestos sheeting was taken off the roof, it  could be seen that wire mesh was sandwiched between the asbestos and the boarding underneath. There were also two loops either side of the windows, where presumably the metal shutters over the windows (confirmed metal by the hut owners) could be connected.

In  a source document used for this web page (ie A History of the R/T ‘Y’ Organization Ashore and Afloat) one section says that aerial exchange boards were avoided while another section says they were used. Stuart Rayner believes that he can explain this apparent contradiction. " You can see an aerial exchange board in the Imperial War Museum photograph of the ‘Noise’ watchroom, but not in the Y watchroom. I think the preference was to plug the aerial directly into the receiver where they could, which was relatively easy for the Y watchroom. In the ’Noise’ watchroom they would not have been able to fit in the number of receivers for the number and type of aerials, so it was simpler to have one or two workstations and an exchange board, although this would have limited what they could monitor at any given time".

There is also a series of Admiralty photographs taken in November 1944 when the Southwold station was operational. These twelve photographs are held by the Imperial War Museum and can be seen at the following URL:

http://www.iwm.org.uk/collections/search?query=Southwold&items_per_page=10

As one can see,  the interior photographs of Southwold are titled by Watchroom and only one photo was taken of the Noise watchroom.

This is a photo of the 'N' hut at the Southwold station.  The deliberate fogging in the photo  has been minimized as much as possible. © Imperial War Museum Photo #A 26125

Equipment identification in the N watchroom: 1- The receiver in front of the Wren is believed to be the Hallicrafters S-27D. An S-27C manual can be found here. (Courtesy Collingwood Heritage Collection)  2- Cossor Oscilloscope Type 3339.  3- G205 Oscillator. Commercially known as a BSRL50A or BSR L50B . This oscillator could be used to  produce a signal to beat with and thus measure any modulation from the transmitter of interest, 4- Not identified at this time.  © Imperial War Museum Photo #A 26125

October 24, 1944: The interior of the Test Room at the Southwold station. (Imperial War Museum photo # A 26129)

The 'N' hut was the one closest to the tower with the more complicated aerial sets, which were directly linked into the respective huts through conduits in the walls. The experts are having difficulty with what the different aerials were used for although the present opinion is that the very top of the N tower could probably be rotated to enable direction finding.

In addition to this, is that there are some recordings from a shellac disc available on web sites of noise intercepts made at Southwold in 1943. These can be found at:
https://www.youtube.com/watch?v=cLG1Q-z-1e0
http://www.cdvandt.org/fading-wartime-sounds.htm

They conclude that the recordings are of jamming and one of a radar transmission, but they also think that voices can be heard in the background. It is possible that the recordings were made from a tannoy (a sound-amplifying apparatus used as a public-address system) in the room? When I was making the survey, it was quite evocative playing these recordings in the room they were probably recorded in."

VENTNOR STATION

Ventnor station location. (Image Courtesy Google Earth)

CAFO (Confidential Admiralty Fleet Order - see note [1]) 1907 issued on August 31, 1944  defined the additional training required for  personnel performing 'noise' intercept work att 'Y' stations.

In this explanation,  the following terms apply.

Ldg Tel =  Leading Telegraphist.
(S) = Special
Wren (S.O.) is WRNS Special Operator
(N) = Noise Duty qualified

Before additional training could begin, personnel had to meet the standards set out in CAFO 1128/43 for Telegraphist (S) and  CAFO 1182/43 for Wren S.O.   Personnel suited for additional training were selected from a pool of volunteers . This advanced training was to be 2 months in duration. People not suited for 'noises' work were to remain in the Telegraphist (S) and W.R.N.S. branches. Personnel who qualified for 'noise"
 work would continue to wear the same badges as Telegraphists (S) and Wrens (S.O.).

These were the percentages required for a passing grade for the listed examinations

The Buzzer receiver standard consisted of the followung minimums:

* Plain language English - 23 wpm
* Plain language foreign- 23 wpm
* 5 figure cipher - 14 wpm
* 4 letter code - 25 wpm
* Short messages - 20 wpm

CAFO 1907 also expands on the standards of knowledge. for the W/Y technique.  The following table rates knowledge levels into  A and B categories.

A= Detailed knowledge of the subject
B = Good general knowledge of the subject, omitting details.
 
 

KNOWLEDGE ITEM	Ldg. Tel (S) (N) and  Ldg. Wren (S.O.) (N)	P.O. Tel. (S) (N) and P.O. Wren (S.O.) (N)
Knowledge sufficient for purposes of recognition of Allied and foreign W/T procedures . Both of the fighting forces and commercial.	B	A
Knowledge of all kinds of receiving and recording apparatus in the station which is doing the receiving.	B	A
Knowledge of the method of investigation of signals, analysis, treatment  and disposal of material received.	B	A
Operation and adjustment of all types of receiving  and D/F and recording apparatus in the station doing the receiving	A	A

CAFO 1907 contains more detailed information about the level of knowledge required to qualify for noise analysis. Only highlights have been extracted and posted here.

LINGUISTS

In the book "They Listened in Secret, Edited by Gwendoline Page" oral histories were derived from the the German linguists who had a lot of memoirs of their time in the ' Y' Service. There are three sections written by Freddie Marshall who ran the “Special Duty” linguist section from its inception through to the end of the war. He identified how it was set up, the required training and how it progressed throughout the war.

Freddie identified the need for Wren German linguists in early 1940 after the evacuation of Dunkirk, to take over from the male German linguists at the 1st Y Station at Dover. Male linguists were required on vessels. A “Special Duties” section was set up under the ultimate direction and control of NID9 at the British Admiralty, growing up to be a private army of NID9, almost without reference to Naval Commands. Local Wren commanding Officers had no idea what went on at the Y Stations, nor did they have any authority over them and were not allowed anywhere near the intercept rooms. German intercept training started at the Royal Naval College Greenwich, the first course starting 22nd July 1940. The attendees had to sleep in the basement in hammocks during the air raids. After January 1942, the course was held at RNTE Southmead at 22 Inner Park Road, Naval personnel went through the same course at Southmead as did the Wrens. The Wrens were taught the likely R/T traffic from E-boats and provided  the Wrens with German nautical terms and the English equivalents they were likely to hear. Traffic was given in plain language and coded commands in German phonetic alphabet.

There was a shortage of German speakers at the beginning of the war and initially they were channelled into R/T intercepts, being the only people who could complete this task. The Y Stations expanded as German linguist Wrens became available. Wrens also served at the intelligence centres where they translated the W/T intercepts. Later on, linguists became W/T operators, as the German empire shrank, however the Southwold station remained operational until 1945 as the S-boats were still operating up until April that year.

RADAR COUNTERMEASURES (R.C.M.)

Noise operators were trained to recognize non-communications emissions. Today we would call them ELINT operators. Their primary task was to find hostile emissions and recover as much parametric data as possible from them, so the data could be recycled for future use in identification . (CAFO 91/45 para 3). Some of the Noise operators were also taught how to use jammers - that is non-communications jammers - typically against radars, German radio controlled bombs (missiles) and other emitters.

Noise operators served both on land (Wrens and Matelots) and at sea (Matelots).  Jammer operators served mainly on land because, with few exceptions, ships did not have radar or comms jammers (CAFO 1569/44). Such systems were too big as space on ships was limited.  They were power hungry, heat generating sources of RF  which interfered with ship's own systems. When not used, they would have also taken up valuable space. There were a few exceptions to this.- the primary ones being J Ships, specially selected and fitted with jammers in support of Operation OVERLORD.  There were also a couple that served in the Mediterranean with comms jammers, to disrupt the Italian R/T air-to-air and control circuits.

The main land-based radar jammers involving Royal Navy personnel were located in the Dover area. It is believed there were some on the Isle of Wight, but there is no proof at this time. These are believed to have been targeted at aircraft emitters and aircraft receivers and in particular to interfere with the German guidance beam systems that were used to guide the bombers to find their High Value Targets in the UK.

L/Tel(S)(N) and POTel(S)(N) were fully qualified in ’noises’ and RCM and served both ashore and afloat. These ratings were already (S) trained, so they were well aware of foreign Morse and R/T intercept techniques, and with some limited language ability; they were aware of German (and Italian) codes and cyphers) and capable of carrying out traffic analysis when a new circuit was found. Noises and RCM requirements appeared rather late in WWII mainly from around mid-1942 onwards

By 1945, candidates for Leading Telegraphist (S) (N) and Petty Officer Telegraphist (S) (N)  given a practical examination in Radar Counter Measures (R.C.M.) on the following equipment.

* Type 78T was the predecessor to the Type 91 CFXR, however no details are available at this time.
* Type 91 CFXR radar (350 to 800 MHz) was used in conjunction with the P58 and Marconi 1147/A receivers.  It was the Admiralty's intention to replace type 91 CFXR with American type TDY, however, WWII ended before this could be implimented.
* Type 650 series  missile jammers [3] were not actually introduced into service until 1944  Then came type 651.
*  American type TDY jammer (90 to 800 MHz) per CAFO529 page 6.

In all of this, it was *not*  the Admiralty's policy to jam German communication circuits [2]

NOTES:

[1] These CAFOs and AFOs were the way that the naval hierarchy disseminated info and management instructions to RN Personnel both ashore and afloat. The instructions might be temporary or could be incorporated into Kings Regulations and Admiralty Instructions or one of the mass of handbooks and operating manuals that abounded (and still do to this date).

[2] Per CAFO 529 Page 6.   As a rule, ships generally did not have comms jammers. They took up too much room, ate too much power and generated too much heat for very little use. There was more to be gained by listening to a comms circuit than by jamming it. There were exceptions to the general rule, mainly based on strategic grounds, such as Operation Overlord.

[3]  As a trial, the first ship fitted with a Type 650 radar jammer, was HMS Woodpecker in 1944. The Type 650 comprised a 5AD and 5AE transmitter and a P101 and B38 receiver using an APW dipole aerial. It is believed that this trial was part of the proving process for Operation Overlord.

Webmaster's note:  If anyone can contribute additional content (ie noise analysis or RCM ) to this story, please contact: jerry.proc@sympatico.ca

---

Contributors, Credits and References:

1) Stuart Rayner <stuart.rayner(at)mac.com>
2) Extracts from A History of the R/T ‘Y’ Organisation Ashore and Afloat, July 1940 to May 1945, TNA HW8/99
3) Beeston Hill photo  https://goo.gl/images/5o5nzd
4) https://www.radiomuseum.org/r/hallicraft_uhf_receiver_s_27_s27.html
5) http://www.iwm.org.uk/collections/search?query=southwold&items_per_page=10
6) http://www.hariggers.co.uk/odds.htm
7) CAFO 1907 Pages 12 and 13
8) Clive Kidd  <cjckidd(at)waitrose.com>
9)
10) Imperial War Museum photos of the Southwold station
11) CAFO 91, Item 6
12) CAFO 529 page 6
 
 

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May 3/24