[Bruce Dennis]

"SECRET A. D. I. (K) Report No. 390/1945
THE FOLLOWING INFORMATION HAS BEEN OBTAINED FROM P/W
AS THE STATEMENTS HAVE NOT AS YET BEEN VERIFIED, NO
MENTION OF THEM SHOULD BE MADE IN INTELLIGENCE
SUMMARIES OF COMMANDS OR LOWER FORMATIONS, NOR SHOULD
THEY BE ACCEPTED UNTIL COMMENTED ON AIR MINISTRY
INTELLIGENCE SUMMARIES OR SPECIAL COMMUNICATIONS.

RADIO AND RADAR EQUIPMENT IN THE LUFTWAFFE – X.
German early warning Ground Radar.
1. This report is the tenth of the series dealing with radio
and radar equipment in the Luftwaffe. As in the case of the
previous nine reports (A.D.I.(K) 343, 357, 362, 365, 369, 370
and 330/1945), it is based on interrogation of General
Nachrichtenführer MARTINI, Director General of Signals, and
some members of his staff, and has been supported by a number
of relevant documents of recent date which were in the
possession of the General's Chief of Staff.

DEVELOPMENT OF EARLY-WARNING RADAR.
Early History.
2. As recounted in A.D.I.(K) 343/1945 and again mentioned in
A.D.I.(K) 365/1945, the Freya, which became the first standard
early-warning radar set for the G.A.F., was developed by the
firm of Gema, Berlin, with the encouragement of the Navy. The
first Freyas were in operation as naval coast watchers in 1938
at a time when the G.A.F. was only thinking of radar in terms
of searchlights and Flak.
3. The Technisches Amt wished to push 50 cm. wavelength
like that of Würzburg, but the Navy backed the longer
wavelength of Freya, and General MARTINI, who immediately
appreciated the advantage of a wide-angle apparatus of Freya
type to early warning, asked that a number of Freyas should be
allocated to the G.A.F.
4. In early 1939 one of the present P/W, Oberst Ing. HENTZ
was selected from among the Köthen staff to take charge of the
first experimental Freya used by the G.A.F. in that year.
It was thought at first that the Freya would only give
indications over the sea, but during the march on Prague in
the first part of 1939 an experimental Freya was set up in the
Riesen Gebirge in order to watch Czech aircraft which might
react to the German advance. This experiment was not a
success, as the signals operators had not been expecting to
find their tube cluttered up with permanent echoes.
5. At the outbreak of war the G.A.F. possessed eight Freya
stations distributed round the East and North Frisian islands
guarding the Heligoland Bight and the approaches to the North
Sea ports. These Freyas proved their value during the early
Bomber Command raids on Cuxhaven and Wilhelmshaven etc., when
some outstanding successes were registered by German fighters,
which were vectored on to the bomber formation as a result of
the early-warning obtained by the Freyas. It was this success
which convinced the G.A.F. of the practicability of radar as
an early-warning device.

Early Developments.
6. The range of the early Freya was of the order of 80 km and
their accuracy of the order of a few degrees. No height
finding facilities were available. The height finding problem
at close range was solved by directing a Würzburg on to the
target when it came within the range of the latter, which in
these days was about 30 km. This system of height measurement
continued to be the only practical one for a long period,
although the field operators had put in requirements for
height finding Freya apparatus as early as 1940.
7. Experiments by the G.A.F. produced the Wassermann, but
the German Navy experimented with the object of introducing
height finding facilities in the Freyas, and the N.V.K. at
Pelzerhaken produced the "Chinese" and "Tiefland". The former
gave maximum location by means of a compensator in an serial
system inclined at 45° and was used for angles greater than
15°, whilst the latter was intended for angles less than 15°.
The combination of the two mounted on the Freya was known as
the “Malaya”.
8. Measurement of height with the Tiefland was possible
between 2° and about 15° over level terrain; measurement of
angles of less than 5° was, however, very inaccurate and range
was actually less than that of the Würzburg-Riese. Over uneven
terrain, measurement of the vertical angle was impossible.
9. The Tiefland had the disadvantage of being complicated in
operation - a large field of reflector nets was also necessary
- in addition to which it gave no better performance than the
Würzburg-Riese. Its use would only have been justified had it
been a device which could be moved easily and quickly and had
there not been restrictions on the selection of suitable sites
for its mounting.
10. Freya Fahrstuhl was designed by Köthen as early as 1943
but was never put into large-scale production, and was not
satisfactory. This apparatus depended on the difference of
phase observed between direct ray and ground reflection to
give height.
11. Finally, in 1944 methods or swinging the beam
electrically were used in the Wassermann for height
measurement, but the Würzburg remained the basic means of
measuring the elevation up to the end of the war. The D/F
accuracy of the Freya was greatly improved when the split beam
or A.N. technique was introduced in 1942, end this made Freya
valuable for fighter control on the Egon system.
12. The range of Freya, naturally dependent on height of an
objective, was about 150 km. but this was not considered
sufficient for the early-warning service and efforts were made
in 1942 to produce early-warning apparatus with greater range.
The first of these was the Wassermann which improved the
early-warning range to about 200-250 km, while the Mammut,
used by the Navy for coast watcher purposes, was also used by
the G.A.F. and gave ranges up to about 300 km. Finally
Elefant, which gave ranges up to 350 km., was built and came
into operation in about 1944.
13. By the middle of 1943 an elaborate early-warning service
covering the whole of Germany and composed of sites with both
Freyas, Würzburgs and Giant Würzburgs had been built up, and a
number of Wassermann chimneys were in operation along the
coast of Europe.
14. The great improvement in D/F accuracy resulting from the
split beam technique was utilised by KAMMHUBER to develop his
box system of night fighting, and in fact at this time it was
strictly forbidden for a night fighter to fly any form of
night defence other than the close control of the KAMMHUBER
box system.
15. Other methods of fighter control namely the Egon and
Bonito, were under development, and of these the former also
used the Freya wavelength for range and D/F.
Effect of first use of Window.
16. When Window was first used in July 1943 the whole of the
early-warning system as well as the night fighter control
system broke down completely.
17. The first German reaction to the use of Window was to
attempt to filter it out or obtain some method of
distinguishing between blips due to window and those due to
the aircraft itself. Virtually no work had been done on this
problem before July 1943 because GOERING had been so
frightened by the prospect of Window being used by the enemy
that the theoretical possibilities had been hushed up and
scientists has not being allowed to work on the problem (cf.
A.D.I.(K) 334/1945).
13. Nevertheless, when Window was first used by the Allies, it
was only a matter of some ten days before the first solution
to the Window problem for the Würzburg was forthcoming in the
shape of the Würzlaus, which relied on the Doppler effect.
High priority was given to the problem and even money prizes
were offered for solutions.
19. Three main types of equipment were evolved as a result of
the various solutions proposed; one was Taunus, which gave
greater blip resolution, another was the propeller modulation
type such as Nürnberg and the third was based on the Doppler
effect, the latter being termed Laus A—J devices. Of these the
Freyalaus for Freya and Wasserfloh for the Wassermann were not
used operationally till 1944.

Effect of Further Countermeasures.
20. As Allied countermeasures became more intense and
electronic jamming was also used, the signals staff decided
that it should be the genera1 policy to provide all types of
radar with the facility for a change of frequency. The first
efforts to do this were brought about by mechanical trombone
tuning of the aerials so that two or three neighbouring
wavelengths could be used. This was termed the WISMAR
principle.
21. Sometime in 1943 Dr. SCHULTER of the firm Siemens
developed the Breitband (wide band) aerial which enabled a
much greater frequency spread to be used. This principle was
termed Voll Wismar and with increasing experience was to be
applied to all types of ground radar. At the same time Freya
and Würzburg were allotted different "Inseln" or frequency
bands in the hope that some of these bands would not be jammed
locally. This policy was carried to great lengths, but Allied
countermeasures still remained extremely effective.
22. Either owing to the weakness of German centimetre
technique, or to a lack of appreciation of the value of
centimetre wavelengths, the main trend in avoiding British
countermeasures was towards longer wavelengths, and special
Köthen Freyas using wavelengths of 5 and 8 metres were
prepared. When jamming on the more normal wavelengths
became severe these reserve sets were operated for a minimum
period often only a few seconds, in order not to compromise
the wavelength, and an effort was made to obtain a clear
picture of the air situation with their aid.
23. Eventually wavelengths up to 13 metres came into use for
early-warning with giant sets such as Elefant.
British Transmissions as an Aid to Early Warning.
24. Despite all these precautions, and despite the fact that
P/W claimed that many of these wavelengths were not
effectively jammed, it frequently happened that the earlywarning
service was unable to obtain a clear picture of the
situation and recourse had to be made to indirect means. The
monitoring service was of particular value in this respect,
and they successfully maintained their point of view that it
was not worthwhile jamming the fighter R/T because D/F’ing of
this provided excellent early warning.
25. The fact that British night bomber crews were in the
habit of using Monica and H2S from the very beginning of their
flights was also of great assistance in supplementing the
early-warning picture. In the same way Allied I.F.F. was of
great value, and special Freyas known as Freya Flamme which
covered the I.F.F. frequency band were erected on some
important early-warning sites.
26. Finally, an ingenious system which was invented by Oberst
Postrat SCHOLZ called Klein Heidelberg utilised the reflection
of the transmissions from British C.H. stations and was
regarded as virtually unjammable.
Development of Panoramic Presentation.
27. As early as 1940 a requirement was put up for a panoramic
presentation for early-warning radar, but no great progress
seems to have been made until the discovery that H2S was using
a P.P.I. successfully. Difficulties were encountered with the
early types such as Propeller developed by Lorenz and it was
not until early 1944 that the Jagdschloss sets came into
existence. These were originally used entirely for early
warning and not with the idea that night-fighter aircraft
could be controlled with their aid. It was not until 1945,
when the value of Jagdschloss was fully appreciated and it was
numerous enough to cover 1st class radar sites throughout
Germany that some efforts were made in its employment for
control of night fighters.
28. With the intended introduction of Neuling I.F.F., which
could distinguish not only between friend and foe but between
individual crews as described in A.D.I.(K) 365/1945, fighter
control from panoramic presentation was to be greatly
extended.

SPECIAL PROBLEMS AND APPLICATIONS ON GROUND RADAR.
Day Fighter Control.
29. The necessity for day-fighter control from ground radar
stations was early appreciated by the Signals staff, and the
Battle of Britain proved to them how successfully it could be
used by air force inferior in numbers. Spasmodic attempts were
made to introduce it into the G.A.F. but the German fighter
tradition was too strong, and the pilots would not accept
ground control.
30. It was not until 1943 that close ground control on the
Egon system using the FuGe 25A in the aircraft was introduced.
Control of Night Fighters.
31. With KAMMHUBER’s box system two Würzburg sets were used -
one to follow the target and one to follow the fighter, the
positions of each being projected on to the map by means of
the so-called Seeburg Tisch. So long as there was no jamming
of ground radar, this method was successful and could place a
fighter within 200-400 metres of the target. Later the
Würzburg Riese was used and the majority of these sets were
allocated for this purpose.
32. A suggestion had been made that the Würzburg 50 cm.
transmission should be used simultaneously for giving the
fighter his vectors and a system named Sprechstange was
experimented with. It was rapidly found that, if the operator
failed to hold the fighter in the beam, the pilot received no
instructions from the ground, and so vital instructions might
not be heard. For this reason it was soon abandoned as not
practicable.

I.F.F. Problems.
33. The FuGe 25A was originally designed by the firm of Gema
for use with the first Freyas operating on 2.4 metres. As
recounted in A.D.I.(K). 365/1945 it became the standard German
airborne I.F.F. set in 1942 and was used with the Kuh
transmitter and Gemse receiver on all ground radar
installations, whatever the wavelength, with the exception of
the Würzburg series. A full description of the problems of
ground radar has been given in the above-mentioned report.
Plotting of High Flying Aircraft.
34. In 1944 it was found that the very high level Mosquito
bomber attacks on the Reich sometimes crossed the coast
unplotted, and at best were only detected intermittently after
passing the coastal screen of Wassermanns which could swing
their beams upward electrically. The reason for this was that
the main lobs of Freya only went up to about 8,000 metres.
There were two subsidiary lobes, the higher of which reached
to 12,000 metres, but the latter only gave limited coverage at
this height over an estimated range of 70 km.
35. The Würzburg beam was too narrow and did not give general
coverage, while Freya Fahrstuhl, which could also be utilised
for aircraft flying at great height, had hardly been
introduced into operations. For this reason considerable use
was made of the Würzburg Riese-G which was a Giant Würzburg
with a very narrow 50 cm. beam, with additional Freya aerials
on 2 metres, set in the paraboloid, giving a wide beam
coverage as well. As the circle paraboloid could be tilted
upwards, excellent high coverage was obtained and high fliers
were plotted with its aid.

Plotting of Low-Flying Aircraft.
36. The Germans were fully aware of lack of low cover, which
enabled aircraft flying low over the sea to cross the coast
unnoticed. A number of experiments were conducted to overcome
this disadvantage by placing special aerial arrays at
considerable height above the ground as for instance in the
case of the Würzmann using the Würzburg frequency and the
Tiefentwiel using the Hohentwiel A.S.V. frequency.
37. Some experiments were also conducted with wavelengths of
about 20 metres with the idea, it was believed, of making use
of the curved path which those waves followed. The experiments
were never completed, as this band was interfered with by
communications signals transmitted on the same wavelength.
38. Experiments had also been made at Köthen with Taunus
equipment coupled to the Freya to obtain extremely high
resolution. A Fieseler Storch aircraft was used, flying at 150
metres over flat country, and under these conditions the
aircraft could just be seen at ranges of 4 or 5 km. through
the ground returns due to woods and houses. It was concluded,
however, that this range was so small that no advantage was to
be gained.

GROUND RADAR INSTALLATIONS.
Freya.
39. Freya was manufactured by the firm of Gema, Berlin,
which, at the outbreak of war, was only a small establishment
largely financed by the Navy. Members of the Technisches Amt,
as well as of MARTINI’s staff, criticised the firm, severely,
saying that they lacked experience of manufacturing and were
unwilling to make themselves adaptable. They described the
Freya Stand for instance as a “cast iron monstrosity”, which
they felt could easily have been made very much lighter in
weight and manufactured more simply.
40. Despite this complaint against Gema, it was a principle
that all ground radar apparatus should be of fairly simple
construction so that it could be made mobile. A few days after
the invasion of Norway the Germans were experiencing
considerable trouble from bomber raids in the Stavanger area
and an urgent request was sent out from there for a Freya to
be supplied. This job was given to one of the present P/W, and
within three days of receiving it a Freya LZ Stand had been
dismantled and packed into three Ju.52's and transported to
Stavanger. Eight days after the reception of the order the
Freya was operating.
41. At the beginning of the war the G.A.F. possessed eight
Freyas. At the end of the war over 1,200 had been manufactured
and a document dated 1st January 1945 states that 671 were in
operation at that time.
42. Owing to the incidence of all forms of Allied jamming,
the original wavelength of 2.40 metres had been modified very
considerably. The following impressive list of wavelengths
current at the beginning of November 1944 was found among
documents brought by General MERTINI’s staff:-
M. M.
Insel A
Insel B
Insel C
Insel D Band Z
- 2,32-2,45
- 2,08-2,24
- 3,00-3,30
- 1,50-1,55
Köthenband gelb/braun
Köthenband gelb/rot
Köthenband Ludwig
Köthenband gelb
1,70
1,80
1,95
2,00
Y
X
W
V
U
T
Vollwismar
Bereich I
II
III
- 1,55-1,60
- 1,60-1,65
- 1,65-1,70
- 1,70-1,75
- 1,75-1,80
- 1,80-1,85
- 1,90-2,50
- 1,20-1,90
- 2,50-4,00
Köthenband gelb/grün
Köthenband grün
Köthenband rot
Köthenband braun
Köthenband weiss
Köthenband schwarz
Köthenband blau
Köthenband violett
Köthenband grau
Köthenband blau neu
2,56
3,15
3,40
3,65
4,05
4,60
4,80
5,20
5,75
8,80
43. In addition to this formidable list P/W states that in
early 1945 experiments were being made with a Köthen Freya on
about 12 metres. The Köthen Freya with wavelengths of over 4
metres presented a problem to the aerial experts which was
being solved by using Yagi aerials mounted above the normal
aerial mattress. Although it was considered desirable to mount
the aerials at a height above the ground of at least ten times
the wavelength, this was not always possible; for instance the
Yagi aerial of Köthen Blau (4.80 metres) was, according to a
document, to be mounted 30 metres above the ground.
44. Two further new wavelengths known as the Rotschwarz and
Grünschwarz were planned and were to operate on two of the
frequencies used by British Gee in the hope that they would
not be jammed. It was realized that these wavelengths could
only be used when the jamming of Gee by Heinrich transmitters
was not being carried out. The Freyas so equipped were to be
located as far as possible from the positions of the Heinrich
jamming transmitters.
45. In order that these longer wavelengths should not be
compromised, a so-called Kurz Zeit apparatus was built into
the Freyas which allowed transmission of only ten impulses and
prevented more impulses being emitted for a period which could
be set between 2 and 22 seconds. It was considered unlikely
that listening aircraft would be able to tune to these short
interrupted pulses.
46. A document, dated June 1944, in the possession of a
member of General MARTINI's staff, contains a short history of
the jamming experienced by Freya. Extracts from this document
are given below in free translation:
"Jamming by Jamming Transmitters.
"In April 1942 the jamming of Freya on the original 2.40 metre
wavelength was reported.
"On 5th March 1942 the Chef N.V.W. put up a requirement to the
Technisches Amt asking that alternative frequencies for Freya
should be made available, basing his request on the fact that
parts of a Würzburg, from which the exact wavelength could be
determined, had fallen into enemy hands during the Cap
d'Antifer (Bruneval) raid on 27th February 1942. By the end of
1942 the original Freya wavelength was being jammed generally.
"As no steps to provide alternative frequencies in operations
had at that time been taken by the Technisches Amt or by
industry, Ln. Versuchs Regiment Köthen was asked to use its
resources to provide them.
"After about one month, on 15th June 1945, the first Freya
which operated in an unjammed band, the Köthen Grün, was
handed over to a unit for operational use.
"In 1942, Freya on Insel B and Insel C had been demanded from
the industry but they were not delivered until 1943. The Insel
B sets were first available on 23rd February 1943, but shortly
after being used operationally were jammed by the Allies. The
Insel C apparatus was made available on 10th July 1943 and has
been in regular production until the last few months.
"It must be recorded at this point that the first new Insel
was produced by the industry about a year after Köthen had
produced an improvised apparatus. Moreover, the Technisches
Amt and industry were unable to give the Signals branch a
Freya which was not jammed. Assistance had to be sought from
Köthen, who produced Köthen bands which alone enabled the
further operation of Freyas to take place.
"In view of the jamming situation the Chef N.V.W. demanded on
19/12/42:-
(a) Freya frequencies below 1.90 metres.
(b) A Voll Wismar band which allowed constant frequency
change
(c) Long waves over 4 metres, with the suggestion that the
Yagi aerial arrays should be used.
"The following comments must be made on the foregoing
demands:-
(d) The first Freya below 1.90 metres (Flum 41) became
available on 2/7/43.
(e) The first Voll Wismar was delivered in May 1943, but in
spite of this the first mass-produced apparatus was not
available until July 1944, and then only in small
numbers.
(f) The problem of long-wave Freyas was never taken up by
either the Technisches Amt or by industry. This problem
was solved by the development by Köthen of Yagi
aerials, and these were first built into operational
sets in September 1944.
"Jamming by Window.
"The possibilities of jamming by Window were made quite clear
on 17/3/1943 and a requirement for an anti-jamming device for
all radar apparatus was formulated. Not until 19th June 1944,
that is, one year and three months later, was the Freyalaus,
which had been developed by ZVH, made available by the Chef
TLR.
"Since it was clear that a change-over to longer waves to
avoid Window was the only possibility available at that time,
the only solution was the use of long-wave apparatus (Yagi
Köthen Grau). With this type of equipment it has been possible
for some months to obtain an early picture free from jamming.
Further Yagi wavelengths were developed and units are being
equipped with them.
"To make recognition of new radar wavelengths impossible for
the enemy, a short transmission system (Kurz Zeit Messung)
described above was formulated as a requirement on 23/9/42. At
the data of writing this has not yet been introduced."
48. The decision to avoid Window by using longer wavelengths
appears to have been taken on the results of some experimental
work. When Window 1.80 metres long was produced against SN2,
Insel C was severely affected, and research work was done on
the susceptibility of different wavelengths to Window of this
length. The diagram produced in Appendix I shows the effect
produced by a standard quantity of 1.80 metre Window at a
range of about 70 km. on various types of Freya.
49. As a result of this experimental work, the Signals staff
realised that it was an advantage to increase the wavelengths
as the intensity of the signal received fell off sharply above
3.80 metres. It was considered impracticable to put a longer
Window into use and as a result the so-called-Köthen bands
were produced.
50. The Germans were unaware that we were dropping very long
Window {rope) at a later date. A certain number of specimens
of this had been picked up and it had been assumed that it had
something to do with meteorological observations.
51. In an interesting publication Funkmessnachrichten No. 19
dated 25th February 1945, it is stated that the C-Insel of
Freya suffered worst from jamming by ground transmitters but
gelb-rot, grün, braun, weiss and grau Köthen bands and the A,
B and D Insel were also jammed at times.
52. Airborne transmitters were beginning to jam the Köthen
grau band, while Köthen braun and D Insel experienced
occasional interference by airborne-electronic jammers. Only
on one occasion had jamming of the Köthen weiss been observed
from the air.
53. The G.A.F. was vitally interested in the Köthen grau band
which was the main stand-by for the early-warning service, and
it was this band and the Köthen blau on 8.80 metres about
which instructions had been given that they were to be
switched on only for very short time in emergency. About 40
Köthen grau equipments were in operation.
54. The range claimed for Freya was 80-120 km., with a range
accuracy of ±300 metres and D/F accuracy with split beam
(A.N.) 1/3°.
55. It is stated in the same document that by February 1945
all Freya equipments, with the exception of some motorised
units, had been fitted with the Freyalaus. A new type of A-J
device, which is however, not described, named the Prüflaus
was at this time being tested on a few sites.

Freya Flamme.
56. A certain number of Freyas in the Insel D band were set
aside for the purpose of triggering off British I.F.F. when
this had been left on in aircraft inadvertently. It was
claimed that, provided the aircraft was flying at a
considerable height, ranges of up to 450 km. had been obtained
with the Freya Flamme. D/F was difficult due to the wide
spacing of the short pulses and no continuous echo beingobtained.
The Germans were aware that six codes were
transmitted by British I.F.F. and believed that they know the
significance of the various identifications.
57. Initially this proved a most useful very long-range early
warning, but the number of aircraft flying with I.F.F. had
been greatly reduced during the last year of the war.

Freya Fahrstuhl.
58. The Freya Fahrstuhl, designed by Köthen, is a Freya with
height—finding facilities obtained by making use of the
reflected ground wave. It was first introduced in early 1943,
but owing to unknown causes, a certain amount of trouble was
experienced and only about eight equipments were in operation
on 1st January 1945. The original requirements were formulated
in 1940 for a Freya type apparatus to give elevation.
59. This set had a range of 220 km. and was used for height
finding by the early—warning service and also as an aid to
Flak if the Würzburg were jammed. The wavelength used was 2.00
metres (Köthen gelb). The Freya Fahrstuhl was originally
intended as an early-warning radar giving height, but the few
produced were largely used to give height to Flak when the
latter's Würzburg was jammed.

Würzburg.
60. The history of the development of this apparatus will be
told more fully in the next and final report of this series
which will deal with German Flak radar, for which purpose it
was originally designed.
61. The original Würzburg Insel A had no split beam D/F but
was nevertheless used for early attempts to control night
fighters.
62. The frequency used by Würzburg A was a single spot
frequency, between 53.0 and 54.2 cm. It was first introduced
in any quantity for raid reporting purposes in the autumn of
1940, when it was used to obtain the height of aircraft
observed on the Freya. Its maximum range was about 25 km.
63. The next type introduced was the Würzburg C with A.N. D/F
facilities and range of 25 km. The first Würzburg C’s came
into service in the summer of 1941. A few were used for
controlling night fighters, but the great majority was used by
Flak. The Würzburg C’s were on fixed frequencies in the band
53.0 to 54.2 cm.
64. The final form of Würzburg, the D, had still only a 25
km. range operationally, but was a general improvement over
the C with split D/F facilities giving an accuracy of ± ½° and
range accuracy of ±50 metres. It was introduced in the autumn
of 1941 believed to have been used for Flak purposes only.
65. The original sets were in the frequency band known as
Insel A 53.0 - 54.2 cm but later a B band from 56.7 to 58.0
and a C band from 62.3 to 63.8 were introduced.
66. Finally a Würzburg was manufactured with wide band
aerials using the Urechse equipment which allowed any
wavelength between 53.0 and 63.8 cm. to be used. The Urechse
transmitter was being generally introduced in the spring of
1945.

Würzburg Riese.
67. The Würzburg Riese was introduced in 1941, and from the
beginning was mainly used for the close control of night
fighters on the Himmelbett system. In all, 452 sets were in
operation on 1st January 1945. A few sets were used for
providing the Gross Batterien, situated at Berlin and other
places, with information for their anti-aircraft operations,
but these were of the Riese G (Gustav) type with Freya aerials
incorporated in the paraboloid, so that a 50° wide search beam
was provided as well as the 13° main beam on 50 cm.
68. The wavelength used for the Freya section of the Riese G
was originally 2.20 Metres, but wavelengths of 1.80 metres and
1.70 metres were also introduced, and it was intended to use
1.60 metres in the future. The Würzburg section of the Riese
used the A and B Insel of the Würzburg bands, namely 53.0 -
54.2 cm. and 56.7 - 58.0 cm. The range of the Würzburg Riese
was about 70 km. and its range accuracy was of the order of
±50 metres.
69. Some ten of the sets used for Flak were provided with
Voll Wismar using the Schwarz Echse transmitter on a new
wavelength of 1.50 metres.
70. The additional Freya wavelength was found to be
particularly valuable against U.S. day bombers, which usually
only jammed the Würzburg 50-60 cm. band and left the Freya
band unjammed.

Wassermann.
71. The original purpose for which Wassermann was introduced
was to obtain a more powerful early warning radar with a
greater range than Freya, and it was therefore the G.A.F.
equivalent of the novel Mammut. Three main types of Wassermann
were produced, the L, S and M.
72. The Wassermann L (Leicht = light) was produced by Gema
and was said to have a range of 200 km., an accuracy in D/F of
± ½° and in range of ±5 km. The first set came into use about
the summer of 1942; two types were manufactured, namely L.I,
on 2.40 metres and L.II on 2.01-2.27 metres, in which spot
frequencies (Streuwellen) at 15 mc/s intervals were available.
About 25 of these were built. They were constructed as lightly
as possible so that they would be transportable, which was
considered specially important for the Balkans and in Norway.
It was estimated that they took about 3-4 weeks to erect. They
had, however, a disadvantage that in strong winds the whole
tower was apt to be blown over.
73. The Wassermann S (Schwer = heavy) was also constructed by
Gema and its accuracy was comparable with the L, except that
ranges of 300 km. were obtained. The first equipment was
erected towards the end of 1942 and in all some ten became
operational. The first seven sets erected (S.1 to S.7) used
wavelengths of 2.40 or 2.46 metres. These numbered S.8 to 10
used 2.36 metres, 2.34 metres and 2.29 metres. These sets took
something over 4 months to build, but they were at least more
robust than the Wassermann L.
74. The final form of Wassermann, the M. (Mittel =
intermediate) was designed by Siemens. Its accuracy in D/F and
range was about the same as the other two types but a maximum
range of about 220 km. was obtained.
75. The first types introduced were the M.I and M.II in the
autumn of 1943. Both used frequencies in the 2.01-2.20 metre
band but the M.II allowed different frequencies within this
band to be used on the Wismar principle.
76. The M.III used the 1.20-1.90 metre band, and was of the
wide band Voll Wismar type but only two sets were built, as it
was succeeded in the spring of 1944 by the M.IV which gave
wide-band facilities from 1.90-2.50 metres. Some twelve M.IV.
were in operational use by January 1945, and more were being
produced.
77. The latest form of Wassermann was to be the M.V. which
was a wide band equipment working on 2.50-4 metres, of which
one experimental set had been set up on the Baltic coast.
78. Since about the beginning of 1944 an electrical
compensating arrangement had been built into the Wassermann
which allowed the beam to be swung in elevation, and an
elevation of about 15° could be obtained. The A-J device
Wasserfloh with Doppler effect was fitted first towards the
end of 1944.
79. Generally speaking the Wassermann was a disappointment.
Production of Elefant was postponed as the original estimate
of Wassermann's range, as late as autumn 1943, was that it
would give 400 km. coverage. Wassermann never succeeded in
giving coverage much over 200 km.

Mammut.
80. This coastal radar equipment which was known to the
Allies as the "Hoarding" was really a Naval coast-watching
radar of which some 8-10 specimens were operated by the
Luftwaffe. It had the advantage that the polar lobe was well
beamed - more beamed than the Wassermann - and, therefore, it
was not very susceptible to jamming but it took about 8 months
to erect and was costly and unvieldy. The comparatively narrow
lobe scanned electrically by means of a phase shifter, termed
a compensator. The wavelength used was the original Freya band
2.40 metres and the range achieved some 300 km. No height
finding was available.

Elefant.
81. The Elefant, sometimes referred to as See-Elefant was
produced by the Reichspost and was designed in part by Ober
Postrat Dr. SCHOLZ. At the end of the war three equipments of
this type had been built and a further three were in course of
erection. The wavelength used was comparatively long, in
conformity with policy of escaping the effect of Window by
increasing the wavelength. Of the three sets built, two were
in the 7.90-8.80 metres band, and the remaining one in the
band from 10.70-12 metres.
82. A D/F accuracy of 1° was obtained and range accuracy of
±4 km. The first set was created in the summer of 1942. But it
underwent constant improvement and its form was not finalised
until 1944. In November 1943 the Technisches Amt refused
definitely to sanction the large-scale introduction of Elefant
as although a range of 400 km. was obtained similar results
were expected (but never obtained) from the Wassermann. A few
were, however, built by Köthen in the field.
83. In order to prevent the long wavelength from being
compromised, the Elefant was only used for short periods and
when the air situation was not clear to the ear1y-warning
service. This was the more important as it was realised that
Elefant could easily be jammed. The normal array consisted of
two 100 metres high towers.

Heidelberg.
84. One of the present P/W believed that experiments were
being carried out with an early warning set on a wavelength of
between 18 and 20 metres which was to be called Heidelberg. He
understands that jamming interference was encountered, as the
set operated on the frequency band used by W/T traffic, and
for this reason the project was dropped. P/W stated that it
was hoped to obtain very great ranges, as the waves would
conform to the earth's curvature. There may, however, be some
confusion in his mind with the Klein Heidelberg system
described below.

Klein Heidelberg.
85. The name Klein Heidelberg was given to a system utilising
reflections from aircraft of the pulses emitted by British
radar stations or by distant German stations. Strictly
speaking, therefore, it was not a radar set at all.
86. The results obtained were satisfactory at the three
stations used, but at the time of its invention by Ober
Postrat SCHOLZ, in 1941, it was not regarded as of particular
importance, as their radar was not being jammed.
87. In 1944, when jamming became serious, the Klein
Heidelberg system proved of great value. Its D/F was poor but
range was adequate for early warning information.
88. It was noticed in October 1944 that our 25 cycle CH
stations had started to change their p.r.f. but a radio
locking system was improvised within six weeks and thereafter
no trouble was experienced. Tests were made to utilise the
Gee pulse sources, but the system worked adequately with CH
and the experiments were not pursued.
89. When he was interrogated on this matter Dr. SCHOLZ stated
that he understood that the results obtained at the Römö
station were surprisingly good, despite the great distance
from Great Britain.

Würzmann.
90. The Würzmann was the name given to an experimental
coastal set which was to be used for the location of low
flying aircraft. According to P/W, it was a Jagdschloss
Michael B aerial array set up on end. The aerial array of the
Jagdschloss Michael B consisted of a double row of 18 Würzburg
mirrors and measures not less than 56 metres x 7 metres.
91. This gigantic erection was mounted so that the electric
centre of gravity was 50 metres above sea level and produced,
in fact, a Würzburg beam which was very narrow in azimuth.
With its aid it was claimed that aircraft flying at 0 feet
could be seen at a range of 20 km.

Tiefentwiel.
92. Tiefentwiel was the code name applied to an aerial array
placed high above ground using the Hohentwiel A.S.V. set with
the intention of detecting low-flying aircraft coming in over
the sea. No details of the aerial array or method of operation
were known but it was stated that the Tiefentwiel achieved as
good results as the Würzmann, namely a range of about 30 km.

Hohentwiel Boden.
93. Funkmessnachrichten publication No. 19 announced the
introduction of a short-range highly-mobile early-warning
radar called Hohentwiel Boden which could be erected in 15
minutes. The set consisted essentially of the Hohentwiel
A.S.V. set with an aerial array mounted on the top of a 10'
high mast. This improvisation was carried out by the Ln.
Versuchs Regiment Köthen, who stated that individual targets
could be seen at a range of 30-35 km. and formations at 60-70
km. It was to be used in the front line to give advance
warning of raids.

PANORAMIC RADARS.
Propeller.
94. Some time in 1943 the firm of Lorenz produced an idea for
a P.P.I. presentation for early warning to which they gave the
code name "Propeller". This set relied on extremely rapid
rotation of the aerials and used a wavelength of about 50 cm.
95. Just before the set was officially demonstrated to the
G.A.F. it exploded. All the apparatus was lost and the project
was abandoned.
Jagdschloss F.
96. The first type of early-warning radar set giving
panoramic display which come into operation in usually
referred to as the Jagdschloss, although it’s official
designation is Jagdschloss F, to distinguish it from later
types, such as the Michael B and Z. It was produced by the
firm of Siemens and was first used in operations in early
1944. About 65 Jagdschloss F equipments had been manufactured
by the end of the war.
97. Equipments No. 1 to 62 were of the Voll Wismar type using
wide band aerials and covering the band 1.90-2.20 metres. From
63 onwards the frequency band to be covered was 1.20-1.90
metres. A document mentions Jagdschloss lang (=long) with a
wavelength of 8.0-10 metres. No information about this has
been obtained.
98. These sets were used exclusively by the early-warning
service and gave a range of about 100 km. with a D/F accuracy
of 1° and a range accuracy of 4.5 km.
99. The range accuracy depended largely on the presentation
on the 40 cm. P.P.I. tube. At 100 km. the area of error was
stated to be 5 x 5 km. but Köthen was attempting to improve
the presentation so that blips could be read to a greater
accuracy by introducing electrical range rings.
100. Another trouble that was being experienced in February
1945 was that the 50 cycle frequency at the national electric
grid affected the presentation so that the blips which should
have appeared as small arcs actually appeared as an arc with a
wavy out-line.
101. The P.P.I. tubes produced by Siemens were being modified
to avoid this imperfection while the Fernseh A.G., who also
produced tubes for Jagdschloss, were working on the problem.
It was believed that a new type of "Tonfrequenz" cable would
be necessary. Particular attention was being paid to this
point because of the difficulties in reading the tube caused
by window.
102. According to a document a new type of valve called the
Nullode was being introduced at this period to replace the
8D.6 diode in the Simultan unit.
103. It was proposed to introduce a selecting switch, by
means of which three alternative pictures could be produced on
the P.P.I. tube. The first picture showed all blips present on
the tube, the second position allowed the I.F.F. to be
switched in, while the third was a purely I.F.F. picture in
which only friendly aircraft with I.F.F. operating came up.
104. The I.F.F. problem had not been fully solved and it is
stated in a document that a separate FuGe control set is
necessary to assist in obtaining unequivocal identifications.
105. In this same document mention is made of the Münchhausen
system which was to use coloured photographic films to
distinguish between Windows and moving targets; stationery
targets would appear on the film as dark spots while moving
aircraft would appear as spots with red and blue edges in the
direction of movement. This system had been worked out at
Werneuchen and in February 1945 the first apparatus was in use
with a Jagdschloss equipment in the field. The film, however,
took between one and two minutes to develop.
106. Further difficulties in the form of dead zones were
being encountered with Jagdschloss and it is suggested in
Funkmessnachrichten publication No. 19 that a wire netting
surface with a radius of 50-60 metres should be built round
the Jagdschloss in order to get rid of the lower dead zone and
to aid in increasing the range against high flying aircraft.
It is stated that one ton of iron wire netting necessary for
each site.
107. According to P/W the electrical jamming of Jagdschloss
was never very severe, particularly as it had Voll Wismar. The
fact that it was causing trouble was, however, proved by the
fact that in Funkmessnachrichten publication No. 19 it is
stated that a number of special cameras had been provided and
were in use at various Jagdschloss sites to take pictures of
the type of jamming encountered in order to ascertain what
measures could be undertaken against jamming.
108. A so-called electric lens was to be used as a means of
seeing through Window. This was an arrangement whereby a
magnification of between 2 and 3 times natural size could be
obtained of a circular area of the picture. The area which
could be magnified could be chosen but was limited to circles
whose circumference passed through the centre of the tube, but
did not reach the edge of the 40 cm. P.P.I. tube.
Jagdschloss Michael B.
109. A ponderous aerial array of two rows of eighteen
Würzburg mirrors measuring 56 metres long x 7 metres high was
used in the Würzmann experimental early-warning radar, and
formed the serial array for Jagdschloss Michael B with the
array in a horizontal position. The wavelength employed, was
that of a Voll Wismar 53.0-63.8 cm.
110. By means of this aerial a beam of ½° horizontal width
was obtained and a range of about as much as 250 km on single
aircraft was expected. It was also expected that the narrowbeaming
of Michael B would be of great assistance in avoiding
Window. The dead zones were to be overcome by switching the
frequency to another wavelength in the Voll Wismar band II,
which was believed to run from 50-60 cm. The first set was to
be ready in April 1945.

Forsthaus F.
111. This apparatus was designed by Telefunken to fulfil the
same purpose as the Jagdschloss Michael B using the so-called
Euklid 25-29 cm. waveband employed by the Navy. Once more a
very long aerial array 48 metres long and about 8 metres high
was used, employing a cylindrical paraboloid. A wave guide
antenna (Hohlraumstrahler) was placed along the focal line
with a second and a third wave guide parallel to it above and
below respectively. The object of these two supplementary wave
guide aerials was to provide displaced beams and so avoid the
dead zones. A range of 220 km. was expected against single
aircraft but no details were available as to whether it had
come into operational use.

Forsthaus KF.
112. In order to introduce as rapidly as possible a panoramic
early-warning radar in the West on a hitherto unused
wavelength, a smaller form of the Forsthaus F called the KF
was to be introduced while the F was being completed. It was
planned so that it could be used on a railway wagon; the
revolving aerial array was only 24 metres long and it was
expected to give a range of 120 km. The wavelength and
electrical circuits used were exactly the same as in the

Forsthaus F.
Dreh Freya.
113. This set, which was also known as Freya Panorama, was
first introduced in June 1944. It consisted of a Freya aerial
of the Breitband type working in Bereich I (1.90-2.50), the
frequency of which could be adjusted at will. The aerial was
so built that it rotated through 360° and gave a remote
panoramic presentation. About 20 equipments were in use in
January 1945. The range claimed for it was only about 100 km.

Jagdhütte.
114. This apparatus, which was produced by Siemens, gave a
panoramic P.P.I. display of the German I.F.F. responses, using
24 metre or 36 metre rotating aerials. The wavelength employed
was 2.40 metres and it was planned, with its aid, to trigger
off the FuGe 25A. In this way friendly fighters were to be
controlled from the ground at ranges up to about 300 km. It
was fully realised that if the FuGe 25A frequency was ever
jammed the Jagdhütte would be useless, but it was not
considered likely that the Allies would attempt to jam it.
115. On the 1st January 1945 the first Jagdhütte equipment
was being erected, and it was expected that production would
amount to two per month thereafter. At the end of the war
about 8-10 were being built, but there is no information as to
how successfully they were employed.

Jagdwagen.
116. Jagdwagen was designed as a mobile Panoramic radar to
control fighterAs at close ranges immediately behind the front.
It was a project of the firm of Lorenz. The aerials were
considerably smaller than the Jagdhütte, the array being only
8 metres long. The aerial array was to be mounted on the
Kumbach stand as used in the Egerland Flak set. The frequency
bend used was that of the A.S.V. set Hohentwiel namely 53-59
cm.
117. The horizontal beaming was of the same order as that in
the full Jagdschloss F, namely about 6°, and ranges claimed
for it were of the order of 40-60 km. for medium heights. A
small P.P.I. tube of about 15 cm. diameter was used.
118. In February 1945 the first sets were being tried out at
Werneuchen but it was hoped to produce the Jagdwagen, in
series, as a fully mobile panoramic set operated by a
motorised company to install them on aerodromes so that a
picture of the local air position could easily be obtained.

Jagdschloss Z.
114. The Jagdschloss Z was the centimetric form of
Jagdschloss, which was in development by Siemens; the rotating
aerials were to be about 24 metres long. These sets were to
give an extremely narrow beam and so offer protection against
jamming. The range expected was of the order of 100 km., and
although the first experimental equipment had been built it
was not expected that sets would came into operational use
until the autumn of 1945.

Forsthaus Z.
120. The Forsthaus Z was another form of 9 cm. panoramic for
early warning, which was produced by the firm of Telefunken.
It differed from Jagdschloss Z mainly in the design of aerials
and was about in the same stage of production. No information
could be given as to the advantages or disadvantage possessed
by Jagdschloss Z.
NOTE: One of the documents brought to England by General
MARTINI’s staff contained a list of the frequency
coverages mentioned in this report, and is reproduced
in Appendix II."