The USAF Radio Station at Martlesham Heath, East Suffolk

THE COLD WAR SIGNALS BACKGROUND

The background to the Martlesham Heath radio relay station was of course the Cold War. Because NATO spanned the Atlantic, and the English Channel and North Sea, its members’ armed forces in North America, the UK and Western Continental Europe had to have a single communications network which could not easily be cut, jammed or overheard by the Soviets. At first, and for several years, this consisted of HF (high frequency) radio, using Morse code, probably encrypted and decrypted using 2nd World War “Enigma” type machines, undersea cables and telephone land lines.

This always had its flaws. Having captured eastern Germany in 1945, the Russians were fully aware of the Enigma system. Through the “Cambridge traitors” and other sources, they also knew how it had been intercepted, decrypted and exploited by the British. Because NATO HF transmissions carried far over the horizon, and could not be confined to narrow beams, they could be picked up behind the “Iron Curtain”. Undersea telephone cables were not a military secret, because for their own preservation they were marked on public sea charts, and though the Soviet Navy was not capable of gaining control of the seas around Britain and Western Europe it could, probably with submarines, have cut them. (2017—again in the news!) However, American nuclear dominance made a European war unlikely, so the existing system sufficed until the Soviets developed and deployed nuclear missiles towards the end of the 1950s .

In the new strategic situation military information and orders would need to be passed on in minutes, not hours. Nuclear warhead explosions might also sever underground cables. What was now needed was an instantaneous communication system between all the main American and NATO command centres and bases which could not be readily cut or listened into.

THE RADIO TECHNOLOGY BACKGROUND

During the 1950s six technological steps had made this possible: 1)The wider availability of microwave (beyond Very High Frequency) radio—invented for radar purposes during the War, when it was called “centimetric wavelength”. Its transmissions could be confined to very narrow beams of defined range which did not “leak” out sideways or over the horizon, and, futhermore, could carry more information in relation to time.2)The substitution of “solid-state” radio transistors for traditional glass, wire, gas and vacuum valves (in American parlance “tubes”). Apart from advantages of durability, lesser size and weight, and portability, these gave more flexibility and speed of operation .3)Digitalisation—that is, transmitting computer-style binary-number (0, 1, negative, positive), instead of the traditional modulations (variations) in the wave which constitute analogue. Digital signals can be input for transmission more quickly (thereby freeing up the channel for new messages), carry more information, more easily handle images, are more easily encrypted, are less subject to interference, and are more easily stored (by computer memory).4)Space satellites—positioned hundreds of miles above the Atlantic, if fitted for radio relay, these could by-pass the undersea cables between North America and the UK.

5) More advanced “Multiplexing”—that is, the sending of more than one message from one transmitter and through one aerial at the same time. Though this predated the 2nd World War, it had until recently had only limited application. With analogue, and HF transmission, this had meant “frequency division”—i.e, sending separate messages on one broadband signal which was split, and read, separately at the receiver station. With digital it could be “time-divided”—i.e, a single signal on one narrow frequency rapidly alternated between different messages, and the tiny snippets were reunited at the receiver. Multiplexing meant more information communicated to more people, again in less time.6) (Forward) Tropospheric scatter—bouncing radio transmissions off the atmosphere and so far over the horizon (where not a security risk), thereby avoiding low-altitude routes, landlines and undersea cables, which could be cut, jammed or intercepted.That radio waves bounced back down from ionised belts up in the sky been known since the early days of “wireless”—the lower frequencies relied on it transmit hundreds of miles round the curvature of the earth. On the higher frequencies developed in the 1930s (HF, VHF) this had been regarded as a nuisance, as the returning radio echoes interfered with reception, causing sizzling sounds on sound radio and false blips on radar. However in the 50s it was realised that forward echoing could be used intentionally to signal beyond the horizon to a receiver too distant to be reached by line-of-sight. According to the frequency and transmission power there was such forward “deflection” from several levels of the atmosphere, but the handiest was the lowest--the troposphere”around 1-8 miles above ground. The “bouncing” signals scattered, which caused them to reach the receiver at slightly different times, and with very reduced strength, but by means of various electronic devices they could be regathered and made clear.

Coincidentally, between 1949 and 1958 some of the early troposcatter test work was done by Marconis at Great Bromley, which had received BBC signals from Yorkshire and transmitted to receivers in Yorkshire and as far away as Scotland. Reports on it were filed by the Americans. The transmission frequency they used (858 mc/s) was almost the same as that later used at Martlesham for the same purpose. (Power had been 500 W—half that later used at Martlesham).

Because of the height of the troposphere transmission could not exceed about 500 miles, and was pointless below about 30, where masts could be built with mutual line of sight. However, it made sense for signalling across the sea between the UK and the European Continent, where the intervening distances (except Dover-Pas de Calais) vary between 100 and 350 miles. The six steps above were in many ways interdependent.

THE USAF SHF NETWORK--& STAGE 1 AT MARTLESHAM.

By early 1960 the American Department of Defense was ready to start installing this new high-speed, high-content, cable-free, network. Already the day was foreseen when Strategic Air Command or the Pentagon in the USA could talk, directly, instantaneously, both ways, and securely, with the US Air Force in Germany or the British Ministry of Defence.

However, for many practical reasons the scheme could not be implemented all at once, but had to proceed in steps. The first step was to use SHF (super high frequency or microwave) radio beams instead of HF and landlines for intercommunication between the existing USAF headquarters and bases within the UK

and Western Europe. This meant relay masts about every 25-30 miles along chains across South East England, France, the Low Counties, and West Germany. The masts needed to be so close and numerous because the microwave beams travelled in straight lines and could not cross the horizon as “seen” from the aerials. An aerial at 300 feet only has at best a horizon of about 17 miles, assuming there are no hills or other obstructions in view. If the aerial it linked to on the next mast is also at 300 feet, “looking” back the other way, the two masts can be no more than 34 miles apart.

The USAF microwave chain planned for the UK in 1960 consisted of:--A radio terminal at Hillingdon, on the western edge of London, near the 3rd Air Force’s British HQ at Ruislip, which received long distance HF and undersea cable signals from the USA, and retransmitted them in SHF (though still analogue form) into the UK chain;--A circular chain of SHF radio relay stations, running round the Upper Thames Valley, via Croughton in Northamptonshire, to link the US bases there;--Branching off from this eastwards, a line of relay stations to the USAF bases in East Anglia, such as Wethersfield, Mildenhall, Lakenheath, Bentwaters and Woodbridge;--Branching off south eastwards, a similar line to Swingate, near Dover, and then on to France, for contact with the Continent, especially West Germany, the likeliest scene for any NATO-Warsaw Pact land fighting. The 35-mile “hop” across the sea from Swingate to France was possible because the existing masts at the two places were high on cliffs above open water and so within line of sight;--A northward branch, via Fylingdales as far as southern Scotland;--A south-westward branch from Surrey to Ringstead on the Dorset coast.It is clear from the termination of the south-western and eastern legs on the coast that there were to be longer-distance tropo-scatter stations at those points.

The system was to be operated and staffed by the USAF (in the UK and northern Europe the 3rd Air Force), but it also handled some of the signals traffic of the other US services.

The East Anglian relay chain proposed at that time ran Hillingdon-Bovingdon (Herts)-Stansted (Essex)-High Garrett(Essex)-Walton on Naze (Essex)-Martlesham Heath (Suffolk), using masts at existing RAF airfields, or, in Walton’s case, a onetime radar station. Martlesham’s existing mast, taken over by the USAF in the 1950s, had been for the shared use of their nearby Bentwaters and Woodbridge bases, and had presumably linked to them via landlines and/or the 168-megacyles-per-second (Megahertz) VHF radio used on airfields to speak with outlying fire, rescue, and ground-defence units.

Almost immediately (apparently in 1961) this East of England relay chain was altered to Bovingdon-Barkway (Herts)-High Garrett (Essex)-Great Bromley (Essex)-Martlesham. Why this change of route occurred is at present unknown. Possibly for secrecy, especially with the mast up on the Naze at Walton? Possibly because Barkway and Bromley were higher masts, raising the signals further from the ground?

The radio relay equipment installed consisted of:a)Marconi-made HM560 sets for receiving, boosting, “cleaning up” and retransmitting the 4 GHz (4,000 MC/s) SHF beams. These consisted of 3 adjoining racks, each of about 7 X 2 feet, respectively for reception, re-transmission and frequency control. They were housed in trailers painted olive drab, and were two per single-route station (for relaying in opposite directions), or three where a route split.b)Standby diesel-electric generators to power the sets in case the mains supply failed;

c)Two “paraboloid” (dish) aerials for reception from the two next stations (in opposite directions);d)Two similar transmitter aerials, but at the base of the mast and sending the beams up to two diagonally-sloping flat metal boards which reflected them out to the next stations. This reflecting arrangement was adopted because microwave transmissions have to go up to aerials in tubes called “waveguides” which will not work if more than a few dozen yards long. These upward-facing ground transmitter aerials and high sloping boards (nicknamed “flyswatters”) were clearly visible to the public, even from afar, at the relay sites, including Martlesham, but total secrecy was impossible.

So far the new network enabled any major US base within Britain to communicate with any other one, both with Morse code and voice. It did not yet extend back to the USA or on to Continental Europe.

The USAF wanted all the terminal and relay sites to have a supplementary VHF system, for liaising between the SHF relay sites, and for this the British GPO (then responsible for allotting all UK radio frequencies) allowed the same 168 mc/s the USAF already used on and around its bases.This was installed in about 1962, and survived a British suggestion to remove it in 1963. It was probably worked through the single VHF “folded” aerials visible on the mast legs at Martlesham, Bromley and Barkway all the time the USAF were there.

Martlesham Heath at this juncture (1960-61) was not a radio terminal or major facility, but just the last link in the relay chain which ran from 3rd Air Force HQ to its “Twin Bases” at Bentwaters and Woodbridge.

“ACE HIGH” COMES TO MARTLESHAM

However it came into its own with the next step—“tropo-scatter”.So as to have alternate routes, in the event of enemy attack, the cross-Channel Swingate-France relay needed complementing with another which reached US forces in Germany via the North Sea and Belgium. So as to make use of the existing East Anglia chain, and include the Suffolk “Twin Bases” in it, in March 1960 a tropo site was suggested for one or other of those bases, linked across to a similar site at Selzeate in Belgium. By the summer of 1961 Martlesham was substituted as the UK terminal, and Flobecq as the Belgian.

Martlesham would not be the only tropo station in the UK, because a whole North Atlantic-North Sea tropo chain had already been planned. This was to run from the USA, via eastern Canada, southern Greenland, Iceland, and the Faroe Islands, to the Shetlands. From there it would run in a circle all round the North Sea via Norway, Denmark, Germany, France, Coldblow in Kent, Stenigot (a former RAF Chain Home radar station in Lincolnshire), RAF Boulmer (Northumberland) and Mormond Hill near Aberdeen. (Messages could go round either way). Another, and ambitious, tropo link was to run from Ringstead in Dorset right over the western English Channel and Bay of Biscay to Humosa on the north coast of Spain, so as to connect to a chain running east along the Mediterranean.

A short tropo chain had, in fact, been installed across mountainous Norway from Oslo via Trondheim to the northern port of Bodo as early as 1958—and was now to join the circle.

The whole new US network was officially codenamed “Ace High”. “Ace” because of “Allied Command Europe”, but also possibly because it was the highest card in the pack.

Within UK territory it needed H M government approval, partly because its transmissions cut across existing, or planned, British civilian radio telephone and television transmissions all the way down the country. On civilian behalf the GPO initially objected, and even questioned whether “tropo” was necessary. There were similar doubts on the Continent. However, the scheme was approved and the plans finalised by the end of 1961, on condition that the signals were confined to two frequencies—862 mc/s for transmisssion and 927.60 for reception (these refer to Martlesham). These were UHF (microwave), but not at the top end. They were not ideal, because, being slightly cone-shaped rather than narrow beams, the transmissions tend to spread, weakening them and making enemy interception easier. The USAF had wanted a tropo frequency of around 2600 mc/s.The bandwidth of 1450 kc/s allowed for many channels to be frequency-division multiplexed.

In official correspendence the current Berlin Crisis was cited as justification for the scheme.

As far as is known the original Martlesham tropo frequencies were never changed, as a late 1970s US report says that, though desirable, it had to be ruled out for technical reasons.

The Martlesham Heath tropo station had been built and equipped by 26 February 1962, and started work on 9 April that year. Its transmission power was 1 Kilowatt. Its new radio equipment was made by Siemens-Halske. At that stage it had two masts, each 115 feet tall and three-legged, with the transmission aerial on one, the receiver on the other. In about 1966 additional aerials went onto the two masts for a new link to the Ballistic Missile Early Warning radar station at Fylingdales, on the North Yorks Moors. All four aerials (transmit and receive) were 30-foot dishes. Those for the Flobecq link were solid and black, but the Fylingdales ones mesh. The westermost (Flobecq) mast also carried the relay dish and board aerials for linking to Great Bromley. It appears to have been heightened for the sake of the transmission reflecting board, so as to get line of sight onto the Bromley receiver dish, which was mounted lowest of all its aerials. The eastern mast (also Flobecq) mast had two small flat mesh aerials of the type used with the old American forces’ VHF TRC-24 radio, for communicating with Woodbridge and Bentwaters nearby, and a small folded VHF aerial for Great Bromley liason .

SHF transmission to Gt Bromley

SHF reception from Gt Bromley Fylingdales tropo Hook tropo

Hook tropo Hook of Holland tropo

2 Bases VHF

BHook of Holland VHF

tropoFylingdales tropo Autovon building Twin Bases VHF

Gt Brom VHF l Standby generators

It is uncertain whether Martlesham regularly handled tropo traffic originating from, or bound for, north of Fylingdales—such as from the USA via the islands of the North Atlantic. The coloured American 1967 map in a later section shows two paths down through England for “stateside” signals, the other one being Boulmer -Stenigot-Hillingdon-Martlesham-Flobecq.

Clearer view of 3 masts showing ADDITIONAL aerials when Martlesham linked to the Hook of Holland but Flobecq link was still also in place.Masts and aerials (left to right): Triangular mast--Great Bromley receiver dish-- Fylingdales mesh dish ((facing away from camera)--Flobecq solid black dish.4-legged mast—Hook of Holland mesh dish (edge on to camera)Triangular mast—Fylingdales mesh dish (facing away from camera)—Flobecq solid black dish.The 4th (4-legged) mast carried the other Hook of Holland mesh dish and is off shot to the right.

Photo from Ipswich newspaper, taken at a late date. This shows the following (left to right):Triangular mast with Gt Bromley receiver dish (edge-on on leg nearest camera) and Fylingdales mesh aerial facing away from camera.4-legged mast with Hook of Holland aerial.Triangular mast in background with Fylingdales aerial.Big new 4-legged mast (top out of shot) in foreground—no aerials visible.4-legged mast with Hook of Holland aerial at top and small Bentwaters aerials below.And there was another new mast, presumably off-shot to the right.The Flobecq aerials have gone. But there are now SIX masts, not four.(See “The Big Masts” section).

When radio “carrier waves” arrived at or left Martlesham they had to change frequency (e.g, SHF to UHF or vice versa, of from radio frequency to landline telephone). The modulated signal (reproducing the pattern of voice or Morse had to be removed beforehand and then reimposed by a “modem” (modulator-demodulator)—a term familiar to radio engineers long before household computers. Some websites suggest that the whole USAF radio network, including Martlesham, was just an emergency one to be turned on in the event of nuclear war. This is a misunderstanding. This was an active system in daily use, even if some of the older communications links (landline phones, undersea cables, HF radio) were also still used. However, most messages passed through Martlesham, and were not composed or read there. One website confuses by saying that it was a centre for “sending out secret messages” (the word should be “relaying”).

Since Bentwaters was already the “parent station” for nearby USAF sites (ranging from housing estates to radio masts) it was the base for the unit staffing and maintaining Martlesham (and Great Bromley relay site)—2130 and later 2164 Communications Squadron.

THE FRENCH COMPLICATION

In 1966 a complication hit the system. President De Gaulle gave notice that France, though still a member of NATO, would withdraw from its military structures, including radio systems. This had several effects. Because Swingate (SHF relay) could no longer link to France it had to shift across to the first relay site in Belgium, at Houtem near Ieper (Ypres). The mast there had to be rebuilt to a height of 900 feet, as it was too far from Swingate to have line of sight. While it was being put up the two new four-leg masts and mesh aerials were erected at Martlesham to link with a new tropo station at the Hook of Holland—located to the east instead of south-east. To eliminate the Swingate-Houtem line of sight link, tropo was proposed for the former to connect to Flobecq, but when installed was used for the British to link straight to Germany. So for some years Martlesham seems to have been the only station linking the USAF’s British and German air bases via reasonably secure Morse and speech radio. (There were no doubt still undersea cable, landline and HF radio links, as a backup).

Certainly the Scotland-Norway tropo route marked on 1960 maps was installed. It gave the USA a link to Scandinavia, and via there Northern Germany, without going through Hillingdon, Martlesham or Swingate. The USSR had a strong armed forces presence in the Murmansk area, adjacent to Arctic Norway, and one NATO war scenario was that they would be first attacked there. There was the alternative scenario that the attack (conventional or nuclear) might knock out Southern Germany, Belgium and Britain while NATO still held out in Scandinavia.

The eventual outcome of the French decision (south of Scandinavia) was therefore at that time meant to be two separate links, using SHF dishes and reflecting boards overland, and tropo-scatter over water, between the USAF’s UK and German HQs (and airfields), one running through Martlesham, the other Swingate. This meant that more radio traffic could be carried, and also that one link could be the alternative for the other in the event of breakdown, bombing, etc. “Unreliable” French links would also be cut out altogether.

MARTLESHAM AS A ROUTING POINT (see next map)

From the start Martlesham and the rest of the USAF radio chain could handle many messages simultaneously because of “multiplexing”. At that time this meant “frequency division”, in which a single set and aerial transmitted or received channels of slightly different frequencies at the same time. Each on its own channel, a message could start and finish at any time,

A 1961 Marconi document therefore says that from an SHF radio terminal (of which Martlesham was one), the radios installed that year could pick any one of a “Group” of 12 channels to send a message, or any one of a “Super Group” of 60. It seems that the 12-channel group here means twelve UK bases—the likely list at that time being Wethersfield, Alconbury, Mildenhall, Lakenheath, Sculthorpe, Chicksands, Barford, Croughton, Upper Heyford, High Wycombe, and USAF and US Navy HQs in London. The 60 might mean the phone extensions within those bases, or more probably all those bases on the wider US North West European network, including those in Germany, Norway and Iceland—reachable via some of the over-water tropo links then planned. The same Marconi document says the sets could run up to 240 channels, and the map below credits the Martlesham-Flobecq tropo link with 120, both multiples of 60. Perhaps these higher figures refer to a potential wartime capacity, when there would be more American units and bases in operation, or to the on-base phone extensions (an average of 10 or 20 for each UK base).

Bentwaters and Woodbridge are not included in the lists of SHF stations, from various dates, and no SHF aerials face in their direction on photos of Martlesham. Instead old-style TRC-24 VHFs (or low-UHFs)---visible on its eastermost mast-- provided the link with Bentwaters, and according to a late 1970s report that base connected on to Woodbridge by GPO telephone cable.The routing would have been done manually, by the signaller, at whichever base was transmitting, not at Martlesham, except for its own limited number of messages, and when it was needed to switch signals between the Flobecq and Fylingdales tropo routes. All this is distinct from the automated routing of signals between hundreds of telephones later performed by the Martlesham “Autovon” (in next section).

From American website. Shows state of the DCS network in 1967. Martlesham links to Flobecq and Fylingdales but with Hook of Holland also about to join up. Hillingdon and Martlesham each has an Autovon Exchange. Overland relay routes run round all the US bases in Britain. Connection across via Swingate to Belgium not yet created (route ends at Cold Blow).

Route-selecting also happened at some other stations along the inland SHF relay chain, such as High Garrett (for the nearby Wethersfield air base), and Barkway (where the chain split to go up to Mildenhall and Lakenheath to the north-east and Alconbury to the north-west). However this was done remotely, by the signaller at the source of the transmission choosing (say) either a Mildenhall channel or an Alconbury channel.

Part of 1978 DEB routing diagram. Left to right—Barkway, 21 mile SHF link, Wethersfield, 24 mile SHF link, Gt Bromley, 14 mile SHF link, Martlesham (the big circle with the V meaning “Autovon”, 116-mile tropospheric link, Hoek van Holland. The numbers above the links are the west-east transmission aerial heights in feet, those underneath the distances in miles. “DCS”=Defense Communications System: the whole US radio network.

Another 1978 DEB diagram. The triangle marked CRO is the Croughton space satellite receiving station.On the bottom left there is another direct link back to the USA—probably cable..The big lefthand square is the Hillingdon signal centre. The two chains running north-east and south-east go to Germany via Martlesham-Holland and Swingate-Belgium. The oblongs along these arms are the SHF relay stations. The square top right is Martlesham. “TPO” above it=tropo. The Martlesham chain has TWO separate links: the upper one seems to be for communication between London on the one hand, and the East Suffolk “Twin Bases” and Martlesham itself on the other; the lower for direct communication, going right through via the “Tropo” to the Feldberg signals “gateway” centre in Germany. (“FEL”=Feldberg). The Swingate chain is only single because there are no bases along it (apart from its own minor relay stations). The southern chain is all line-of-sight, not tropo, as the unusually high Houtem relay mast is still in use—with “FLO” (Flobecq) 2 stations to its east. Both local and “straight-through” chains are still mainly analogue, in spite of the term “Digital Backbone”.The USAF London centre (Hillingdon) has 34 analogue and 9 digital trunks to the East Suffolk bases. The East Suffolk bases have 13 analogue and 6 digital trunks to the German Feldberg “gateway”. And there are 5 analogue and 3 digital trunks for Hillingdon and Feldberg to message each other direct—via the Martlesham tropo.This fits the respective volumes of signals traffic one would expect—local airfield messages would be more common than top-level ones between countries. The abbreviation “MAM” was used colloquially as well as on official documents—“I was based at MAM”.

“AUTOVON”

The next step, was “Autovon” (the Automatic Voice Network). Autovon, as its name implies, enabled users to talk in instantaneous, two-way, style, as on any domestic telephone, stating questions and answers. “Automatic” meant that when one base called another it only had to dial the number—not manipulate a radio transmitter to select a channel or ask an exchange operator to put the call through. (I can remember having to do this with civilian phones till the 1960s!) This meant that the switching was no longer done by a person—unless a caller was failing to get through, perhaps. Each base had a PBX (Private Branch Exchange), a small, manned, switchboard connected to its own extensions. It seems that, as with civilian PBXs, at some bases an extension could independently call out (by dialing a prefix number), wheras incoming calls had to be taken first by the PBX operator and then relayed. In that case the caller would have to ask for a particular unit, or for admin, aircraft maintenance, air traffic control, supply, security etc. “PABX”s were automatic in both directions.

Autovon was based on the existing American Bell company civilian system (vintage 1963), and not new defence technology. In Britain its first exchange had first been installed at the Hillingdon network centre in July 1966. There was an Autovon phone book, with users listed alphabetically alongside their numbers, as in civilian books.

Later that year Martlesham became the UK’s second Autovon Exchange, and the existing operations block was rebuilt or extended to house it. It was certainly chosen because it lay at the point where the radio routes between London, the East Anglian USAF bases, Fylingdales/Scotland and Germany met.

The 1992 Ipswich newspapers and Suffolk Aviation Heritage website say that the Autovon Exchange was connected to 550 telephone lines. This needs clarifying. One reason for the system was to avoid long-distance landlines. So “lines” here mainly means “potential radio telephone connections”. With a few important exceptions wires did not radiate out from Martlesham as from a civilian exchange. At first sight 550 might suggest a connection to every American base or HQ in Europe, but there were only 420 European numbers (for around 130 bases) in the whole 1986 Autovon phone book—and these range from Iceland to Turkey, Norway to Spain, the Azores to Germany. The extensions within bases are not listed, but were reached by dialling the area code and then either 4 asterisks or (in the UK) 1110 so as to ask the PBX for a connection. And there were several other Autovon exchanges in Europe, including four in Germany and Hillingdon in the UK. So probably the Martlesham exchange (as opposed to the radio, which ran some calls straight through), mostly just handled calls within Britain and over to Feldberg, where there was another exchange. One call might go through a number of exchanges. A call from a base in the USA to another in Germany might be “switched” a number of times before crossing the Atlantic, twice in Britain (Hillingdon and Martlesham), and twice in Germany (Feldberg and Donnersburg).

The phone dialing worked as follows. To obtain an outside line, as opposed to another extension on his own base, a caller dialed an 8 or 9 first digit. His next 3 digits might be an area code (as with civilian phones), or instead a trunk route or branch of the armed forces—and would also indicate the exchange best located to route his call, in the UK’s case Hillingdon or Martlesham. So, for instance, Alconbury, Chicksands, Martlesham, and the nuclear submarine base at Holy Loch in Scotland were all on 221, Hillingdon, Upper Heyford, and Wethersfield on 231, and the US Navy in London and Italy on 235. The caller’s last 4 digits were for the actual phone he wanted to ring. But, as noted above, often only 1110 or the four asterisks could be dialled, as the call could not go through except via the PBX operator on the other base. Though 4 digits could theoretically have meant 9999 numbers, only a small fraction of these actually existed. Each number dialed travelled as an equivalent number of radio and phone-line pulses.

It perhaps ought to be said that with analogue calls the pulsing, switching, routing, and phone-ringing happened first, and the actual message transmission second. Until digital systems numbers could not be held in memories. (Again I can recall several seconds clunking and clicking on old-time phones before the ring tone was heard).

Most lines were “4-wire” (for two-way conversations), the rest “2-wire” (for one-way Morse). A possible confusion here is that “4-wire” circuits actually had 6 wires, and “2-wire” 3. These extra wires—or, with radio, frequencies-- were known as the “E” (“ear”) and “M” (“mouth”), and respectively opened the way into the Switch, and then back out again in the case of 2-way voice. The Switch did not rigidly tie one incoming line to one outgoing, since that would have been wasteful of

capacity, incapable of dealing with broken down lines, and unable to adapt to an emergency flood of calls. Instead the E and M wires ran through a computer-like “Central Control” which “scanned” all the lines “hunting” for the first available free one. This aspect of the Switch was “time-divided”, in the sense that connections were not made and severred simultaneously, but in succession with split-second rapidity.

One 1970s Martlesham veteran recalls 250 voice and 180 telegraph lines there. So 430 was the maximum number of potential connections possible at the same time. It seems to be only a coincidence that it was also roughly the sum of the European numbers in the Autovon book. 430 does not mean that every potential user could go the phone at the same time, because a)with all the local on-base extensions there were far more of them than that, and b)there were only 120 channels over to the Continent, and a smaller number in the UK. So some callers or signallers would have had to wait their turn. This would have been problematic in a crisis. However in peacetime delays were permissible, though one website veteran says they were an irritation--along with poor sound quality on some calls. There was also the delay (mentioned earlier) of the local PBXs delaying their bases’ incoming calls. The network did get busier when France pulled out, so additional capacity for the Martlesham-routed Autovon was agreed to by a US Congress funding committee in 1967. Perhaps 430 then became 550.

The “490-L Switch” fitted at Martlesham and the civilian version on which it was based were “cross-bar”, or “cross-point”, semi-mechanical, structures. It was termed “5-bar”, because it had that many horizontal bars, but it acted as if it were 10, because each swivelled up or down so as to make two possible connections with each vertical bar. It was a non-blocking Switch, because although its horizontals and verticals crossed over each other, they did not connect unless a horizontal bar pushed a “finger”(line switch) into a grip on a vertical., whereupon a call could go through. When the caller hung up the finger would retract. The fingers were moved in and out by pairs of little wire rods (called “reeds”), which closed and opened when magnetised and demagnetised by surrounding coils charged along the E and M wires. Each of these individual “line switches” was hermetically sealed and about the size of small beer bottles. A photo taken at Martlesham shows they—or the lines taking their signals to or from the modems and radio multiplexers-- were labelled “Channel Translators”.

One 10 X 10 cross-bar “matrix” could handle 100 calls simultaneously. The standard “overseas” (Defense Departmemt) autovon switch” had three matrices. Matrices A and C were “folded”, meaning that they could send mutually exchange signals via “junctor” switches, so as to handle both “in” and “out” through both horizontals and verticals, doubling their joint capacity to a total of 400 calls. Each was also linked via its junctors to Matrix B, a double board (10 X 20), which could interchange calls with A or C, giving the whole Switch a capacity of 600. Subtracting some spares for local inter-relay-site calls, testing and servicing, this probably equates to the “550 lines” referred to above.

It is not clear why there was not just one big board with about 24 horizontals and verticals (=576 “lines”), and the horizontals and fingers did not need to swivel, but it was perhaps because the Bell equipment had been manufactured for average commercial offices, where one matrix might connect to 60 outside businesses (such as regular customers) or internal extensions.

Photographs show square boards at Martlesham with numerous tiny lights. Presumably each light represented a potential connection, and came on when it was made. Perhaps it flashed on and off if the call was not going through, or not being clearly picked up. Each light would have been fed from behind the boards by a “crosspoint” interconnecting. If a large majority of lights were on—and

especially if they were flashing—a Controller would need to override the automatic process and delay, reroute or even answer a call himself.

To sum up so far through an example: Wethersfield combat unit calls Ramstein 3rd AF HQ, while US Navy in London calls USN at

Bremerhaven, and Hillingdon sends printed supply list to West Berlin—all 3 messages arrive at Martlesham via SHF overland radio relay simultaneously

3 messages are de-multiplexed (split) at Martlesham so as to be routed onto new channels By means of “hunting” and “junctor-switching” the Autovon Switch connects the 3 UK calls to the 3

German bases By re-multiplexing (rejoining) Martlesham relays the 3 messages simultaneously, through one tropo

aerial At Feldberg the 3 tropo messages are de-multiplexed (split again) to go off along separate overland

SHF relay links to Ramstein, Bremerhaven and Berlin.

In 1970 a refinement—though also complication—was added to the system. Callers had to choose between 5 levels of priority, as follows: FO (Flash Overdrive”, F (“Flash”), I (“Immediate”), P (“Priority”) and “Routine” (the default setting). They were in descending order of importance and urgency. Only the US President, Secretary of Defense, Joint Chiefs of Staff and senior commanders could use the first, for example. Higher-priority calls might block or delay less important ones. There were different ring tones for the different levels of priority—appropriately the most rapid ringing indicated the most urgent call!

Autovon phone use instruction. NORAD=North American Air Defense Command.“Defcon One”=war, probably nuclear!

Autovon was officially a “non-secure” system. Again this needs clarifying. On-base phones presumably had “scrambler” devices which jumbled up speech (the technology was already used in the 2nd World War). But, though incomprehensible in “real time” to a wire-tapper, scrambled calls could be now be decoded if recorded and played back into computers. “Enigma”-style encrypting was eventually introduced for the top secret communication. The pathway for its calls was called “Autosevocom” (Automatic Secure Voice Communication). The exchange for this was in London, but by the mid-1970s Martlesham is known to have had “COMSEC” encrypting and decrypting equipment, presumably for its own more secret messages. But what this consisted of is unknown.

So as to minimise the amount of “pre-empting” (stoppage) and delaying (for even routine calls still needed to get through) the Martlesham exchange had to switch calls between busy and free channels, and even re-route them altogether (e.g, via a Continental station other than Feldberg), to a greater extent than before.

In fact a “550-line” exchange housed in one smallish room was of very modest size compared to most urban civilian exchanges, which would have thousands of lines and occupy large buildings. Moreover it was seldom that anything like even the 550 lines would be busy. But the system was intended to cope with a nuclear war when most other exchanges, lines and radio relay stations might be destroyed. So its peacetime capacity was mostly spare.

Incidentally Martlesham itself featured in the Autovon Directory—one number for the station andtwo others for air traffic control at the Twin Bases—possibly on another site and linked to the Foxall Road exchange along landlines.

“AUTODIN” (Automatic Digital Network)

Originally, including for the first year of UK Autovon, all messages going through the network were analogue, at composition, en route, and when received. But computers were now coming into their own, albeit still ones with large wheels turning punched tape. So, as explained above, a minority of signals were from 1967 onwards digital. The exchange for routing these was at Croughton, Northants, not Martlesham. Most merely passed through on the radio, but Martlesham did have a computer and printer of its own, for receiving and sending its own limited number of messages.“Autodin” was described as “store and forward”, because like today’s e-mails messages were typed first, then sent, and did not go as they were expressed, as speech did.

Though the Autodin data was input and printed out by digital computers, it was sent in analogue (modulated) form—called “quasi-analogue”. Its speed of transmission was by today’s standards low—only 2.4 or 4.8 kb/s (thousand bites per second), so that even the briefest messages would have taken several minutes to process. By 1977 there were three speeds—2.4, 9.6 and 50 kb/s. The faster ones must have been for longer and higher-priority messages, as opposed to routine. In 1978 a single 9.6 was the situation.The early digital signals consisted of words and numbers (“alpha-numeric”, in the jargon), and seem mostly to have been lists of supplies or personnel.

NOTE ON “COBRA MIST”

An even more striking feature of the East Suffolk landscape was the huge “Cobra Mist” over-the- horizon radar at Orfordness. There was a small scientific similarity between the two, because Orfordness picked up faint echoes from the upper atmosphere-- but by measuring how far these had been shifted in frequency from the original transmission when received back as an echo (the “Doppler effect”) could calculate the latter’s speed and direction and differentiate between civil aircraft, jet fighters and especially missiles. (What tended to be measured, at the heights and distances involved, was not the echo from the craft itself, but the disturbance in the atmospheric reflecting layer around it).

Did Martlesham link to Orfordness? Since it connected to Fylingdales (the other key missile-tracking station) presumably it must have. But Orfordness was only in action (and then just for testing) for one or two years in the early 1970s, and so is not included in the 1986 Autovon directory, as Flyingdales still was.

STAFFING

In spite of automation considerable staffing was needed. In fact the exchange, as opposed to radio relay, must have added to it. After the station shut the local press gave a figure of 110. Mark Trebacz has kept names lists saying that 80 men worked on Technical Control. This must have included radio as well as exchange personnel. A 1979 US study says that DEB would reduce the total number of “controllers” at Martlesham from 18 (with 81% of their time idle) to 15 (78% idle time): so perhaps 4 X 18-man watches (72 men), with 8 more men as reserves to cover for sickness or leave—confirmed by Mark Trebacz listing 8 names as “contingency” staff;The breakdown may have been:-- attendants and engineers at the separate tropo-scatter and inland relay sets-- X 4 watches for the 24 hours;-- personnel watching the automatic Autovon switching gear and routing calls if it failed to cope (X 4 watches), and running the digital equipment (X 4 watches)--a telephonist to manually switch routine calls within the station, and a radio operator to speak directly to Hillingdon and Bentwaters about any concerns (X 4 watches);--a commanding officer (mainly doing admin and discipline), with a secretary;--a few stores personnel, for both technical and other material;--a security officer and his gate guards (X 4 watches), and perhaps a dog handler;--a few fire, first-aid or similar safety personnel;--perhaps a small canteen staff, and those tending an on-base shop, recreation room and dormitory which existed on the site.Up to around 35 personnel would have present at any given time.

One British civilian (“Mr Lewis”) features on Trebacz’s list, and was probably the service engineer for the standby generator. Apparently a few other British civilians had passes for the site to help with security, cleaning and catering, but were not of course allowed into the technical buildings.

As the “idle time” cited above show, the men at the sets, switches and phones would have mostly had fairly little to do, unlike radar or air control staff. However, reports as to how all equipment was functioning probably had to go to Hillingdon at fixed times each day. On the radio side periodic, fluctuating interference, variations in the weather and height of the troposphere causing signals to fade or become indistinct or garbled, electric voltage dropping, breakdowns at other stations causing Martlesham to go dead, parts burning out—all meant that dials and indicator lights had to be watched and controls adjusted, rather as a driver might do with a car dashboard. On the telephone side the occasional query had to be responded to when a caller could not get through or could not hear the reply. Station-defence exercises, fire drills, and crisis procedure rehearsals must also have been staged. A daily log had to be kept.

When off duty most of the “Detachment 7” unit which manned Martlesham was scattered in private lodgings all over the area, as far away as Felixstowe and Bawdsey, and drove in for their shifts. About ten men were, however, lodged in a small dormitory on-site, perhaps so as to have extra Controllers who could step in an emergency, or if outlying personnel could not report in because of roads cut by bombing or even bad weather. By the 1980s a few women were included in the staff.

MARTLESHAM BUILDINGS

Prior to the tropo set-up at Martlesham there must have been a couple of huts or trailers for the radio sets and personnel who relayed the signals for the old Martlesham air base and the newer Twin Bases. Probably the large permanent, flat-roofed, block for the tropo was built in 1961 or 1962, then extended for the Autovon exchange in 1966. An airman from the mid-60s says there were “Marconi microwave caravans”—presumably for the SHF inland relay sets.Judging by photos of the interior, and the set-up at the wartime Chain Home radar stations, the various rooms were for:--the radio transmitter and receiver sets (large metal boxes with doors)--the Autovon exchange gear (mostly vertical switchboards)--the electric mains switches, fuse boxes, “regulators”, DC-AC converters and other gear for ensuring that a constant-voltage, constant-frequency, safe power supply reached the equipment--backup emergency batteries, if the standby generator as well as mains power failed.--ventilator and air-filtering room (air pump, big ducts), essential if gas or radioactive dust shrouded the site—with perhaps an airlock entrance between this and the outside--a decontamination room for anyone who had not had the benefit of this--an office, perhaps with a small internal phone switchboard.--a lounge (with a bar), canteen and small shop mentioned above.--and, some yards out to the west, the standby generator block.

Also see “Big Masts” section for new “ETA building”.Incidentally, it is surprising that there seem to have been no “protected” (bombproof) structures, whereas all the equivalent rooms just listed were behind several feet of earth and concrete at other sites—including the local 2nd World War Chain Home radars. A modest blast wall apparently shielded the main building early on, but later disappeared.

In about 1975 the Great Bromley westfacing aerials were moved up the 358-foot tower from part way up to the very top, extending their horizon by several miles. The next relay site to the west was moved a few miles west, and around 50 feet higher up, from High Garrett (north east of Braintree) to Wethersfield (to its north west). This could possibly have been to raise the beam to above new Electricity Board pylons or the new hospital, and accompanying mast, at Colchester , as these lay across its path.

MINOR (SHF) RELAY STATION CHANGES

SHF aerials at Great Bromley. Dish and board at top communicate with Wethersfield, those below with Martlesham. The highest aerial is 356 feet up. The boards were fed with transmission beams coming up from dish aerials on the ground. One Martlesham mast carried identical aerials.

Also at Bromley, and the other inland relay stations, small semi-permanent huts were built near the masts to house the sets, though (photographs show) without the original trailers leaving. Perhaps active sets were in the one and standbys, together with the mains switches and fuse boxes, in the other. The granddauaghter of the civilian site caretaker at Bromley recalls a hut there which had equipment at the back and a pool table at the front.

It also seems that the SHF relay sets (e.g, those at Great Bromley and Barkway) could be left unmanned, since they were linked back to Martlesham via “Service Channels” (as opposed to the “Mission Channels” for base-to-base messages), which automatically notified equipment failing, intruders on the site, etc—via devices called “RAMMS”—rapid aceess maintenance monitors. These lesser sites are known to have been manned in 1969 (e.g, three at Bromley, five at Barkway), unmanned in 1990, but when the change occurred in between is unknown. 1982 is a possibility, because that May the pay system for these sites ended according to a US Defense Department memo—though some Bentwaters veterans suggest a decade earlier. Of course the unmanned stations were also checked or serviced periodically by visiting parties. As the sites had civilian caretakers or security men, and were behind high fences, they were deemed still secure. One curious thing about the SHF relay sites is that some lay right alongside farm barns, haystacks or junkyards. This may have been to suggest that they were only civilian facilities. The same may apply to the personnel driving in civilian, not camouflaged military, cars.

NEW AMERICAN RADIO SETS

Some time between 1975 and 1984 the original sets (including multiplexers) were replaced by American-made Raytheon ones. So instead of Marconi HM510 landward-facing terminal and HM560 relay sets, TRC-167s and TRC-150s (TRC=”Transportable Radio Communication”), and instead of Siemens-Halske tropo sets, TRC-170s. The TRC-170s had 3 sub-types, the 10 kW long-range V-1, 2 kW medium-range V-2, and short-range transportable 1 kW V-3. A 2164 CS veteran recalls a 10-kW at Martlesham.

When the changeover occurred is uncertain. On the one hand veterans recalls the new sets in the mid-1970s. On the other an official report of the late 70s says that the existing radio equipment is about 20 years old and needs replacing. Possibly the inland SHF relay equipment (TRC-167s and 150s) arrived first, and the TRC-170 tropo later.

It is also unclear whether the new equipment was to be part of DEB (see below), the long-term plan for the mid-1980s. The radio sets for this were called “DRAMA”s (Digital Radio & Multiplexing Acquisition). But “DRAMA” sets had the same workings and performance as the TRC-150s, 167s and 170s, and may indeed have been one and the same.

Just as the early Autodin data signals travelled quasi-analogue, now analogue voice signals went digitally. By 1979 the speed of each of these—whether “clear” Autovon or encrypted Autosevocom-- was 16 kb/s, as opposed to the earlier 9.6. The overall transmission rate, of numerous “multiplexed” (combined) signals, varied from from 128 kb/s, which eight channels could carry, to about 9200 kb/s—for all 192. For that reason the term “MTDS” (Megabit Tropo Digital System”) came into use (“mega” = 1 million; 9200 kb/s =9,200,000). The largest single message that could be carried would travel at 129 mb/s. The variation in speed of these “mission signals” was to accommodate long but low-grade and short but high-grade content—say a long morse message versus a single photograph. (The only doubt here is that the army version of the system involved two transmission and two receiver aerials—for so-called “quad diversity”, which better reduced interference and error. That could have been the case at Martlesham if each dish altenately transmitted and received, as the army’s did. If so which its maximum kilobit rate would have been 4608).There was a separate path for three “service channels” or “order-wire” signals used to check on or instruct the inland SHF relay stations. Digitally this carried up to 192 kb/s only, because they would have been short, simple and occasional. Because it just linked to a few relay stations it connected only to the Level-1 Multiplexer.The TRC-167 and 170 sets used the new (essentially digital) time-division system of multiplexing (simultaneous multiple messaging—see Point 5 in second section, above).The FCC-198 1st-Level Multiplexer merged up to 24 signals into one, with a combined capacity of 1.544 mb/s. The “FCC-99 2nd Level Multiplexer” then merged up to eight of these 24-channel groups into one for tropo transmission—a maximum possible total of 192. (One report says six X 24, or 144). Demultiplexing was, of course, the reverse. The messages these multiplexers dealt with were of 32 kb/s or more (a few pages of type, or a diagram). But, perhaps so as to send messages in successive snippets—for instant response at the other end, as in a telephone conversation, a “LSTDM” (low speed time division multiplexer) was installed, going down as low as 35b/s.

A NEW “SWITCH”?

Around the early or mid 1980s (again the date is uncertain) the original 490-L switchboard was perhaps replaced by the new TTC-39, already on issue to the US Army. It was faster, but more importantly had a digital as well as analogue side, and the capacity to convert one type of message to the other, and to be upgraded to fully digital in the future. Since digital signalling was all time-, not frequency-, divided, the TTC-39 was fitted for this. It seems that this meant that it was now done within the switchgear, not the radio sets.It had a 600-line capacity, which would still fit with the “550 lines” mentioned above.

The TTC-39 was a blocking 3- or 4-stage system. This is complicated to explain, but basically calls were switched 3 or 4 times so as to dodge round each other as much as possible. 100% dodging was impossible, but the computer attached to the switchboard minimised it to a tiny possibility, and for higher-priority calls eliminated it altogether. The dodging of analogue calls was still done by shifting calls from wire to wire (the old “space division” method). But with digital it was done by time-division, like in the radio transmission, and therefore not by means of a physical frames and switches.

SATELLITES

Radio satellites were now up, so that the whole Transatlantic tropo (and where it survived, undersea cable) chain between the USA and Scotland could be suspended. From now on 3rd Air Force in the UK would receive the American messages at Croughton, and relay them on round the existing chain out to the various bases including Ringstead (for Spain), Fylingdales and Scotland, Swingate (for Belgium) and Martlesham (for Holland).

“DEB”

The next plan was for “DEB”—the eventual Digital European Backbone.Using most—but by no means all-- of the existing stations, this was to be an upgraded, faster, bulk-traffic, failure-proof, network. It was a streamlining, refining and joining-up, rather than a technological leap. It included the merger of Autovon and Autodin, a step-by-step progress towards full digitalisation, higher digital speed, the capacity for images, the full control (as well as mere monitoring) of lesser relay stations from the main ones, more flexible route-switching in the event of problems, and the inclusion of non-American NATO-ally traffic.It was to come in 4 stages, the inclusion of other NATO allies being in the fourth!The new TCC-39 Switch, if not already installed, would have been part of it.If the first system had been a continuation of 2nd World War Morse code, scrambler telephones and teleprinters, Autodin a system of early paper-tape computers, and Autovon like the modern BT phone, this was a forerunner of the Internet.

It did not replace Autovon, but incorporated it. As the name “backbone” suggests, it would go along the shortest possible routes, and so exclude most airfields, but these, and various “tails” would still be linked to it via their existing sets and masts. The 1978 Honeywell report makes this clear.

Its digital voice speed was to be 64 mb/s, quadruple that of the existing 16. (64 is considered slow today). It was to multiplex up to 192 channels (1st Level X 24, 2nd X 8)—the same as the current TRC-170.

Signals sent with the original multiplexing did not intersect, as they travelled on different frequencies. The speeds with which they passed along the chain could therefore slightly differ, due to such factors as varying weather. But digital stations had to be mutually synchronised. Otherwise the time-divided message “snippets” being multiplexed would have cut into each other, garbling what was received at the other end. This was already the case with the signals sent along by Croughton Autodin. To “sync” the other stations with itself Croughton seems to have sent a micro-second-accurate pulse to them along “order wires”. But with the faster bit rate (digital transmission speed) of DEB even more precision was needed. So the main relay stations were now to have atomic “master clocks”. A 1984

American chart says that the local ones were to be at Martlesham, Wethersfield, Barkway, the Twin Bases and Mildenhall. Another suggests that Martlesham would have the clock for remotely controlling the “slave” multiplexing timing at Wethersfield, Bromley, the Twin Bases, Colchester and Shoeburyness (see “the Big Mast” section below). Areas synchronised by one “master clock” were called “segments”.

Many other refinements were suggested for DEB.Through “CRU” (Channel Reconfiguration Unit”) computers at “switches” (exchanges)—and eventually “ATECs” (central Automated Technical Control centres)—it would automatically move signals from busy to free channels or find alternative routes for them when their usual ones were cut or degraded. (This is now standard in civilian phone networks). “Tramcons” (Transmission Control centres) would be able to isolate faults in unmanned stations, reactivate them if they were breaking down, and react to enemy jamming .

That Martlesham was to be a main site at which the British military radio network was to link to American DEB is abundantly clear. The evidence so far is:

--In the 1970s the British Ministry of Defence set up their own within-UK radio relay system, named “Mould”, using VHF and UHF. It had relay stations at Great Bromley, RAF Wattisham and Danbury (near Maldon). Its aerials are visible on 1980s photos of the Bromley mast. It was replaced by a higher- frequency system, using both masts and also underground fibre-optic cables, called “Boxer”. In 1982 there was an MOD suggestion to link “Boxer” into the Americans’ DCS. --Meanwhile a 1980 American DEB study proposed linking its tropo to the British “Starrnet” (Static Radio Relay Network), which had handled the signals of the British armed forces in Germany since the 1960s, and had linked directly back to the UK via the long-distance tropo station at Swingate since 1970. Martlesham was proposed as the junction between UK Starrnet and the UK part of the US network.

--The “Ace High Journal” website, set up by Gerrit Padberg, says that Starrnet connected to the American DCS at Roetgen, Germany, and has a floor plan showing that each of the two had its own site, but were adjacent and interconnected via an underground cable.

--A 1984 DEB routing chart for remote-control purposes, includes RAF Farnborough and Honington, and the British Army at Colchester and via Shoeburyness the Royal Navy at Chatham—these last two linking to Martlesham via Great Bromley.

--In the 1980s a new building was put up at Martlesham, alongside the new mast, and called the “ET- A” Building. ET-A stood for “European Tropo-Army”. (Note army not air force).

It would be nice to know how exactly Martlesham would have handled the British Starrnet and/or Mould and/or Boxer traffic. Through separate British-only radio channels? Through another prioritisation system which put vital British messages ahead of American routine ones? One detail in the 1978 DEB study was a suggestion to enable Martlesham to switch the tropo at Thurso (Scotland) between Norway and England if Thurso broke down, and Thurso to do the same at Martlesham if it could no longer switch between Northern England and Holland. (Thurso, on the Scottish mainland near John O’Groats, was a US Navy facility).

A later change in the DEB plan was to move Martlesham’s Dutch opposite number inland to a mast on Woensdrecht air base, which would have meant a slightly longer North Sea tropo link and

adjusting the Martlesham aerials. A still later plan located it near Utrecht. It is unclear whether these last two changes were ever made.

THE BIG MASTS

In photos of the Martlesham station from the 1980s, as opposed to 1970s, two large new masts, additional to four built in the 1960s, stand at the eastern corner. One is higher and wider than the originals, the other about the same height but wider. In the Ipswich newspaper photo shown above the tallest of these masts stands in the foreground and seems to be carrying no aerials. In another photo both new masts have small platforms on their eastern corners.Clearly these masts, and the new “ET-A building” alongside, were to accommodate DEB (IV) and inter-ally (US-British) sets and aerials. They may also have been for the proposed tropo dishes facing Woensdrecht, perhaps while the old Hook of Holland ones stayed as a backup. As Swingate had its own DEB tower, perhaps that was also intended here.

The extra height of the one of the new masts would have enabled it to send signals to relay stations further out than its existing masts could reach--though it would only have gained another five miles. The known “Mould” masts at Back Street (near Bury St Edmunds), Wattisham, and Linstead (near Saxmundham) were all high enough for this to work. Also “spacing” of aerials—so that their beams did not cut across each other—may have been a factor in the dessign of both.

The DEB diagrams show no Fylingdales or other northern link, but this does not mean that it had by now been scrapped—the USAF were still at Fylingdales according to their 1982 base lists and the 1986 Autovon book—and DEB still lay ahead. According to the Ipswich press the Fylingdales link ended in 1990. Martlesham kept the Fylingdales aerials till it shut.

How many of the proposed DEB refinements were actually installed at Martlesham before it shut is still unknown.

CONTINENTAL COMPARISONS

This section isn’t directly about Martlesham Heath but does help put it in context.The Hook of Holland aerials were all mounted on one large latticework structure, with the Martlesham and inland dishes back to back (photos are online).The Martlesham-Hook tropo signals hived off into the German half of US 3rd Air Force, and other NATO bases, at Feldberg, in western Germany--apparently not the same Feldberg as the mountain in the Black Forest. From there a whole spider’s web of radio relay routes took it off in all directions—especially to US 3rd AF at Ramstein, its big air base at Frankfurt Rhein-Main—and eventually to West Berlin. The Continental network, and station sites, varied over time, not only because of France dropping out, but also because of old air bases shutting and new ones opening, cost-cutting, and other factors. A 1990 map of the system only partially resembled the original 1960-61 ones.

There were Autovon and Autodin exchanges in Germany similar to those in England, for routing the traffic—including Feldberg and Schoenfeld. Germany also had a satellite terminal like Croughton’s.

Whereas there were four relay stations in the 85 miles between London and Martlesham, there were only two in the 300 between the Hook and Feldberg—Bruggen (on the Dutch-German border near Maastricht) and Stein. Hook-Bruggen (about 100 miles) was another tropo link—why is unknown, as the flat Netherlands obviously meant long SHF radio horizons and the route is entirely overland. It did point east-south-eastwards towards Warsaw Pact Czechoslovakia, so perhaps its tropo was to minimise enemy eavesdropping. Between Feldberg and Stein an unusual system was used—“diffraction”. The signal crossed the gap by bouncing around between hills and buildings. The 1978 DEB study lists it as a “digital diffraction relay”. Perhaps English-style SHF stations were also avoided because of mutual interference with Dutch and German radio (civilian and military) or TV.

In the earlier period (1962-68), when Martlesham worked through Flobecq, it routinely handled traffic to and from SHAPE (Supreme Headquaters Allied Powers Europe) near Brussels, but this did not normally apply after Swingate came on line and Martlesham shifted to the Hook of Holland. Swingate messages reached Germany at Schoenfeld. The Russians, incidentally, were not only perfectly aware of tropo-scatter, but used it themselves. The Martlesham tropo was mentioned in their own military literature. They had their own masts and dishes, military and civilian, for linking their vast home territory as well as their armed forces in Eastern Europe, as far west as East Germany. In fact the sites of the two sides in the Cold War came within 50 miles of each other at some points on the map!

One reason for tropo-transmission, especially in UHF beams, was to signal “over the heads” of enemy radio-interceptors on the ground or on ships. However, Martlesham’s signals could have been picked up by Soviet aircraft flying along its routes to Flobecq and Hook of Holland, assuming they carried the right equipment.

PUBLIC AWARENESS

There are two ways of looking at this.Many local British civilians had limited interest in, and awareness of, bases such as Martlesham. Some assumed the masts and aerials were for radar, as two of the big aerials faced seawards and older locals could recall the RAF radar at Bawdsey, which was still in operation when Martlesham tropo was built. There was also an assumption that the station served the nearby USAF “Twin Bases” in this connection, though in fact their proximity was largely coincidental.

On the other hand the idea of troposcopic scatter was known to anyone with a fair knowledge of radio and TV aerials. Popular magazines about wireless and TV, read by amateurs as well as professional engineers and radio shop owners, explained it. The Marconi house magazine, and several technical journals, described the relevant tests in detail, and included photos of aerials almost identical to those later put up for SHF relaying and tropo at Martlesham. The development of military tropo-scatter coincided with the great boom in TV stations and sets, as well as “ham radio”. The principle was described in such civilian publications as Odham’s “Television Servicing Handbook” of 1958.

Less public than the tropo station itself was the network it belonged to. Very few would have made a connection between the new Martlesham masts and huge aerials and the very different-looking ones scattered across other counties.

In the early 1980s the Cold War intensified again after a lull: Russia had invaded Afghanistan and President Reagan was sending cruise missiles to Greenham Common in England. This sparked a revival in CND. Leftwing Labour MPs asked in the House of Commons for a list of all the USAF bases in the UK, together with their functions, and this was provided and published in Hansard. The New Statesman and CND’s own leaflets republished it, with the claim that Britain had been reduced to America’s “aircraft carrier”, “puppet” or “shield”. In June 1982 CND staged a simultaneous two-day weekend protest sit-in at all the US bases in Britain—and there was another in November 1983. Martlesham was included, together with Great Bromley. The relevant CND news leaflet quite accurately stated the purpose of the two stations—i.e, radio relay, not radar, though it made the rather unfair claim that they were specifically for passing orders to launch nuclear missiles. The local press, and police, said that the mood was peaceful—and 2164 CS’s own record agreed that there had been no trouble.

CUTTING BACK & CLOSING DOWN

DEB had certainly been proposed as early as 1978, because that December the American Honeywell organisation wrote a secret report for the USAF Defense Department on how it could adjust itself in the event of stations breaking down. (The report, referred to above, is the best single source on the existing relay chain, the use of satellites, tropo, analogue and digital, and the number of trunks available on each). Perhaps for cost reasons, and waiting on the “Internet”-type technology to develop, DEB was much slower in appearing than previous steps. Apart from Martlesham, nine other UK relay stations were allotted for it (including Great Bromley, Wethersfield and Barkway). But when the relevant US Congressional committee discussed financing it in 1987 it was told that none were as yet operational. In 1988 the Martlesham Heath tropo facility closed, because:

i)Satellites now took signals across seas without the need for ground stations and masts;

ii)Soviet defence capability was weakening as the Warsaw Pact broke up, the USSR ran out of money and fell behind in digital capability, the Americans proposed “Star Wars”, and Communism crumbled;

iii)Many of the USAF airfields in Eueope were therefore scheduled for closure;

iv)There were plans for fiber-optic cabling, which, by exploiting the fantastically high frequency of light, could carry almost countless multiplexed simultaneous signals of all kinds.

In June 1992 the USAF left Martlesham, Great Bromley, Wethersfield and the other lesser relay stations on the East Anglian branch of the chain. They had probably stayed on for the four years after the Martlesham tropo station closed so as to link the remaining inland 3rd AF bases with the East Suffolk twin bases. The “Twin Bases” were eventually to shut anyway. The Swingate branch of the chain (now fitted for DEB?) stayed until 2004. The official US report gives cost-saving as the one reason for closure, but this was for public information! (The Cold War has partly returned, and technology has moved on still further) so one wonders what system is used today, and where its secret sites and routes are).

SUMMARY

Martlesham Heath was the Eastern England USAF (and via them NATO) radio terminal and switching exchange between 1962 and 1988. It was not a command centre or combat base, but had the vital task of routing and relaying radio signals between the “missile watchers” in Northern England, the USAF HQs and combat bases in the UK, and those in Germany. It was one of a handful of UK stations of this type. Its radio traffic would have ranged between policy conversations between heads of government and routine lists of supplies, and between warnings from long-range radar stations about potential approaching nuclear missiles and weather reports for pilots. Whether it ever relayed a signal which caused Washington or Moscow to use their “Hotline”, is unknown!

Though in a sense a “glorified telephone exchange”, not dissimilar technically from those built for their own use by the British GPO and Telecom at the same period, its NATO defence role obviously put it in another class.Its high frequencies, switching system, and eventual digitalisation enabled it to handle a large amount of varied messaging almost instantaneously—and operate in 4 different directions. Its tropo communication let it cross distances too great for line-of-sight, and gave it a degree of security from Soviet eavesdroppers.

It was periodically updated with new equipment, so that signalling could be increasingly quick, flexible and informative. It was staffed by US Air Force personnel of the Bentwaters-based Communications Squadrons, mainly 2164.

Key dates:

1950s—Martlesham Heath operating overland short-distance radio link between inland bases and the East Suffolk “Twin Bases”.1957—USSR test fires world’s first Intercontinental Ballistic Missile.1960—USA decides on tropo-scatter system to link its various local radio networks over long distances across water. Woodbridge or Bentwaters suggested as the UK terminal for the tropo link across to Belgium and Germany.1961—Berlin Crisis. -- Martlesham appointed as the tropo station for the Belgian link, and the general “Ace High” scheme accepted by NATO governments. --Inland microwave radio relay route between Martlesham and London set up.1962 --Martlesham starts tropo operations, linking to Flobecq (Belgium).1966—Martlesham acquires Autovon (490-L) Exchange, for routing USAF and other US radio telephone calls. -- Martlesham-Fylingdales BMEWS tropo link established.1967-8—Link opened to Hook of Holland on two new masts.c.1967—System goes partly digital, but via “quasi-analogue” lines.1970—Call prioritisation added to Autovon.c.1975—American-made radio equipment replaces British-made Marconi’s. -- Lesser relay stations left unmanned but to be monitored from Martlesham. —Original Flobecq-link aerials removed. —TRC-170 tropo sets replace originals.1978— Martlesham assigned eventual DEB.c.1982—Two new masst built at Martlesham for extra NATO links included in DEB IV. 1984?---TTC-39 exchange replaces 490-L?1988—Martlesham ends its Hook of Holland tropo link without DEB being used.1988-92—Martlesham acting (temporarily) as local relay for Twin Bases, and perhaps as reserve.1990—Fylingdales aerials removed.

2004—Last of “Ace High” (in rest of UK) removed.

TECHNICAL GLOSSARY

“Ace High”—General codename for US armed forces troposcatter radio system.Analogue—Modulated radio waves mirroring pattern of speech, Morse, etc.Autodin—Automatic Digital NetworkAutovon—Automatic Voice Network, with radio, undersea cable and landline links.Bandwidth—Radio frequency and its possible up and down variation, e.g, 795-805 MHz (either side of 800)b/s, kb/s, mb/s (bits, kilobits, megabits per second—rate at which digital messages come through.Channel—One-way link between signaller and recipient or vice versa; Circuit—radio link or electric wire which, when connected, carries a signal or current.DEB—Digital European Backbone (all-NATO digital radio network proposed for mid-late 1980s),Digital—Radio wave broken up into simple very fast succession of positive (on) and negative (off) states. Four-wire –phone circuit for two-way communication, as opposed to two-wire for one-way.Frequency—number of radio waves per second. Frequency division—multiplexing signals onto slight variations of the main frequencyHF--High FrequencyKc/s (or kHz), mc/s (or mHz)—kilocycles per second, megahertz, etc=carrier waves per second, or frequency.Junctor—switch taking calls between Autovon Switch matrices for the sake of more capacity and flexibility.Matrix—“criss-cross” of telephone circuits on the Autovon Switch. Modem—device to remove modulated signal from received radio signal and then reimpose it on transmission of different frequency or type (analogue/digital).Modulate—shape transmitted radio wave into patterns mirroring speech, Morse code, letters and numbers. Multiplexing—sending several messages through the same set and aerial at the same timePBX—Private Branch Exchange—switchboard connecting on-base extensionsQuasi-analogue—radio signal composed and read digitally but still transmitted in modulated analogue. SHF—Super High Frequency (used for short-distance overland radio relay).Six-wire, four-wire etc—number of electric wires on one telephone line, so as to enable one-way signalling, two-way conversations, and registering the number calling and being called with the Switch so they can be connected.Space division—switchboard-operating by keeping calls on separate circuits.Switch—In US use, a telephone or radio telephone exchange.Time division—multiplexing, or switchboard-operating, by breaking calls into snippets and sending them at alternate fractions of a second with other calls, on the same circuits.Tropo (scatter)—signalling over the horizon by reflecting radio ways back down from the atmosphereTrunk—Pair of channels (transmit and reecive) running between 2 exchanges.UHF—Ultra High FrequencyVHF—Very High Frequency Wavelength—length (in metres or fractions of) of each radio wave; in inverse ratio to frequency (the higher the frequency the shorter the waves and vice versa). The wave on which the modulated signal is imposed is called the “carrier wave”.

RADIO FREQUENCIES SUMMARY

HF (High) VHF (Very High) UHF (Ultra) SHF (Super)_____pre-existing 1939+ 1941+ 1950s +______________ medium range short range, though short range only dittocan go over horizon goes a little over visual line-of-sight only ditto

horizon ____________________________________________________________________________________spreads out wide—so transmits over V-shaped narrow beams; little ditto security risk areas; some security security risk. risk.__________________________________________________________________________________________suited for morse & can be used for images even better for images ideal for images speech, but not imagesscatter from above tropos. some scatter from tropos scatters best from tropos penetrates rather than scatters

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civilian radio “shortwave” local civilian radio from TV from 1970s 1950s & TV in 1960s1939-45 Chain Home 1939-45 Chain Home Low low-angle radar 1942+ modern radar for detecting radar (e.g, Bawdsey) radar high-altitude missiles.LOCAL VHF^ MINOR RELAY STAS^ MARTLESHAM TROPO^ ^ TROPO ORIGINALLY REQUESTED BY USAF