RAF 646 Signals Unit
Motto: KEIN HINDERNIS ZU HOCH (German: No obstacle too high)
The badge and caption above are from the
RAF Air Defence Radar Museum at Neatishead, Norfolk, 2007
where they collect the badges of disbanded units.
Significance of badge device: The White Horse of Hanover was chosen to signify the general location of
the unit, and the portcullis is significant of an obstacle to be overcome before an enemy is able to proceed
further.
No 646 Signals Unit was formed at Obernkirchen, Germany on 1 September 1952. No information has
been released as to this unit’s role. The unit badge was granted in January 1957 and was blazoned as: In
front of a portcullis sable a horse courant argined crined azure.
These next three paragraphs of notes were found on the RAF Gatow (Berlin) linguists webpages dated
2003. I’ve annotated them in italics. It now seems as though these pages have been taken down.
This unit can trace its history back to 1949/50 when it was known as the Air Scientific Research Unit (ASRU) and
was based at Obernkirchen. The exact role of the ASRU is not clear except that small groups would frequently
leave the station for unknown destinations, presumably along the East/West German border. From about 1951, the
ASRU had a permanent attachment in Berlin – probably accommodated on the roof of Lancaster House in
Ferbelliner Platz, later on the roof of the control tower at Gatow and finally in a wooden structure perched on top of
Hanbury Block. In about 1953 the name of the unit was changed to 646 Signals Unit. As 646 SU it continued to
despatch detachments to various locations throughout Germany and Austria and was noted in Cuxhaven, Putlos,
Faßberg, Berlin-Gatow and Schönbonn near Vienna. There is reason to believe that the ASRU/646SU had a very
secretive detachment at Habbaniya in Iraq, referred to locally as Palm Grove. The reason I mention this unit is
because it had a very close association with 5 Signals Wing and its various stations but apparently operated
independently until it arrived at Hanbury when it was fully integrated into the system.
In about 1953 646 SU moved (not quite correct, as I joined 646 SU at Obernkirchen in August 1958 - I don’t know
when Scharfoldendorf became a listening post for 646 SU, but before I moved there) from Obernkirchen to
Scharfoldendorf (about 40 miles south of Hannover) which later became the Headquarters of 5 Signals Wing.
Although working closely with 5 Sigs. Wing, 646SU maintained its independence for, at about this time, the CO,
Wg. Cdr. Eric G. Ackerman GM, (I remember him quite well, as well as his 2nd. in command, John Storer who
worked for GCHQ) who had also been the CO of the ASR, a Civil Servant in the grade of Senior Scientific Officer
with a Class CC Commission in the Royal Air Force, applied to the MoD for a 646 Signals Unit crest. Not unusual,
you might think except that Wg. Cdr. Ackerman proposed a German motto (his wife was German, and taught me
and others German in the library at Scharfoldendorf). In later years this would not have been considered a strange
request but it certainly was in the mid-1950s when it resulted in strong opposition from high ranking officers at
MoD. Nevertheless, Wg. Cdr. Ackerman persevered and, after many written exchanges between the Under
Secretary of State for Air, the Director of Personal Services, the German Embassy in London and Sir John HeatonArmstrong, Clarenceux King of Arms, the DPS (A) finally agreed with the comment "If he wants a German motto
– then let him have it!". In December 1956 the crest, with the white horse of Hannover, a portcullis and the motto
"Kein Hindernis zu Hoch" was given Royal approval.
646 SU was still at Scharfoldendorf until 1958 when, on 31st. August, it moved into rooms used by 5 Signals Wing
which a day earlier had moved to Butzweilerhof. (I moved to Scharfoldendorf from Obernkirchen in October
1958). When exactly 646 SU vacated Scharfoldendorf is not known but it probably joined the attachment in Berlin
which at that time was in Hanbury Block.
The job of 646 SU was to monitor Warsaw Pact radar transmissions emanating from East Germany, and
to relay the information gleaned, back to GCHQ at Cheltenham. To do this there were listening posts at
several sites in West Germany as well as one in West Berlin. The listening equipment was serviced and
the work was co-ordinated from Obernkirchen up to about October 1958, and from then onwards from
Scharfoldendorf.
Site Locations
Obernkirchen – about 20 miles to the west of Hanover, on the slight Buckeburg rise overlooking the
lower ground to the north and west. I don’t think this site was used as a listening post.
Scharfoldendorf – about 40 miles to the south of Hanover, on the summit ridge of the Ith Hils with good
views towards the east, and west. HQ from October 1958. Used as both a listening post, and equipment
servicing unit. Google Maps:- <Holzen-Ith, Germany> shows the site – very similar to what I remember,
including the Schloss, barrack blocks and NAAFI.
Putlos – is north-east of Hamburg and on the same latitude as Kiel, by the Baltic coast to the north of
Oldenburg, and was co-sited on the West German Army Training Ground. Used as a listening post.
Gifhorn – is sited about 20 miles NE of Hanover on the Luneburg Heath. Used as a listening post.
RAF Gatow – about 10 miles west of Berlin centre. Used as a listening post. Now, an aircraft museum.
Communication with sites / security
This was done using trucks and cars. Scharfoldendorf had a large mechanical transport department, and in
the event of invasion from the east, we were expected to go west as quickly as we could. It was thought
that the technical block was mined, and that sledge hammers were sited in the teleprinter room so that the
equipment could be smashed.
Communications with the site at RAF Gatow was via diplomatic bag and courier who travelled on the
early morning train from Berlin to Hannover, and was met by a small party of 3 of us from
Scharfoldendorf. At different times the site was subject to scrutiny by Warsaw Pact personnel travelling
in a marked Soviet Military Mission vehicle (SOXMIS).
Shortly before I arrived at Obernkirchen, two colleagues travelling from the UK by motor bike, had
arrived a day late as a result of a puncture. On arrival they were immediately arrested and held in the
prison cells, suspected of being impostors. After careful checks on their identity had been carried out,
they were released and welcomed to the site.
Monitoring techniques
The main object was to determine where any significant Warsaw Pact activity was based, and what type it
was; and particularly if there were any significant changes in activity which might indicate the
preparations before hostilities. We were also on the lookout for any novel type of signal because this
might indicate the introduction to service of a new or modified weapon. This was done by listening
(using steerable directional aerials) to radar signals from ground troops and aircraft. Due to the one way
path from the (enemy) transmitter to our (friendly) receiver, the system didn’t incur the enormous losses
when signals are scattered from a radar target and a small proportion reflected back to the radar receiver.
Consequently signals could be detected by monitoring, way beyond the active range of the radar.
As stated, the signals were listened to via directional aerial systems; and radar receivers of two
fundamentally different types. The more sensitive type of receiver was tuned to a narrow band of
frequencies, so it had to be re-tuned in accordance with a schedule so that all sites were listening at the
same time to this frequency band. The much less sensitive technique used a “crystal-video” receiver
which was not tuned in any way. This was very basic, and received all the signals in the band to which the
aerial and receiver horn responded, but had a relatively short range. In both cases the operators used
headphones to listen to the audible tones and pulses from the radar receivers.
Pulsed radar signals differ between types, and after rectification, they can be made audible thereby aiding
identification. Airborne radars with a relatively long range had a low pitch whilst shorter range radars
used for gun-laying had a higher pitch. The monitored signals were viewed on a simple CRT display to
aid maximising the signal by rotating the aerial dish, and recorded on Ferrograph tape recorders.
Comparison between tapes allowed experts to decide which signals emanated from the same radar. This
process was helped by recording a coded synchronising track (locked to the BBC pips) on the tape.
Most of the signals being monitored were in X-band (9-10 GHz) with a wavelength of around 3cm, and
most of the dish aerials had a diameter of around 1-2m, giving a receptance angle of around 2-5 degrees.
(Effective angle would vary with strength of signal being received). Consequently to be able to
differentiate between adjacent sites, the receiving stations had to be set well apart, and this is why in
addition to Scharfoldendorf, Putlos and Gatow were considered so important as listening posts. Simply
receiving the radar signals gave us no information on our distance from the transmitter, and transmitter
sites had to be deduced by triangulation using the angle information from our aerials. HQ gave
instructions as to which sectors and frequencies to monitor.
During my year with 646 SU I worked in the development laboratory giving support to the listening
function, testing new techniques and occasionally installing new equipment.
Sites - for which I have photographs
Obernkirchen
From memory, both domestic and technical blocks were on the same site on the outskirts of the village,
and with the same security.
Images are on BAOR Locations page for Obernkirchen.
Ratskeller, Obernkirchen
View to main gate, overlooking the plain
Street scenes in Obernkirchen (2 Images)
Scharfoldendorf
At RAF Scharfoldendorf the station was sited on the ridge of the Ith Hils with the domestic site, parade
ground, NAAFI and mechanical transport unit, MTU, close to the old German Schloss which held the
library, and the mess. The schloss could be seen for miles around. The technical site was in woodland on
the other side of the lane crossing the hills, and this was double fenced with strict security controls in
force.
Six Images are entered on the Scharfoldendorf page
Putlos
At Putlos we were close to the Baltic Coast and guests of the German Army, and accommodation
standards seemed somewhat higher than at Scharfoldendorf! The bedroom furniture was of a higher
standard with metal wardrobes with fitted drawers. Night times were quite interesting as exercises were
held and we could see the tracer rounds as well as hear the gunfire.
Three images are on the Putlos page.