Researching the Luftwaffe through Prisoner Interrogations

[Bruce Dennis]

"SECRET A. D. I. (K) Report No. 369/1945
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 – VI.
Target Homing for Night Fighters.
German early warning Ground Radar.
1. This report is the sixth of the series dealing with radio
and radar equipment in the Luftwaffe. As in the case of the
previous five reports (A.D.I.(K) 343, 357, 362, 363 and
365/1945),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.
POLICY AND REQUIREMENTS
2. Members of General MARTINI’s staff have often repeated
a catch phrase "Aller Funkverkehr ist Landesverrrat" - all
radio traffic is treasonable, and the G.A.F. were only too
well aware that a transmission of any type could be listened
in to by the Allies and then D/F'd. They were, therefore,
fully aware of the opportunities of homing on to
transmissions from Allied aircraft and so when airborne
countermeasures against the Freya ground installations were
first taken by the Allies, Köthen developed an apparatus
which would enable a German night fighter to home on to the
source of the jamming transmission.
3. This equipment was called Freya-Halbe (Halbe = half
signifying that it was a radar apparatus equipped with the
receiver half only and not the transmitter), and it was
tried out at Werneuchen in early 1943. The trials were
successfully completed by about June of that year and it was
then demonstrated to the authorities for use by the G.A.F.
night fighter units.
4. At that time, however, the German night fighter force was
commanded by General KAMMHUBER who was the creator of the
Kammhuber line and whose night fighter organisation relied
essentially on ground-controlled night fighter aircraft
operating in comparatively limited boxes. The suggestion of
homing on to jammers was turned down by KAMMHUBER out of hand
because he was a rabid opponent of any form of freelance
night fighting and insisted on strict adherence by his
aircraft to the limits of their box.
5. With the discovery of Monica and the development of the
Rosendahl and later the Flensburg homers on to Monica,
KAMMUBER still maintained his obstinate stand against any
departure from the box system of control. It was, therefore,
not until General SCHMIDT assumed the control of the night
fighting force in November 1943 and proceeded to introduce
freelance methods that D/F homers on to transmissions from
the bombers could be used operationally.
6. Although the technical experts were satisfied that the
homers on to transmissions of metric wavelengths were
successful, aircrews seemed to be unable to use them well and
results obtained were never wholly satisfactory. Exactly the
same applied to Naxos for homing on to H2S is its early days,
particularly when a number of minor troubles were still being
encountered with its electrical parts and, though it was
available in January 1944, for the first three or four months
comparatively little use was made of an excellent homing
device.
7. By about Easter 1941 the early troubles of Naxos were
overcome and crews began to gain confidence in its use; with
the success of Naxos reliance on all types of homing apparatus
increased. At this stage, however the R.A.F. had almost ceased
to use Monica and Naxos remained the only important set of its
type.
8. In view of the change of policy governing night fighter
operations experimental D/F receivers known as X-Halbe were
designed capable of adaptation to any metric wavelength which
might be used by the Allies. In addition one of the tactical
requirements laid down after 1943 for all future A.I. sets was
that provision should be made for the switching off of the
transmitter portion so that the receiver could act as a homer
on to any airborne jammers employed by the Allies. Naxos and
Korfu Z which covered the 1.5 cm. to 20 cm. band already
existed.
9. As R/T and W/T Jamming became more intense and even
ground control by commentary broke down, increasing use was
made of homing on to the bomber stream by means of receivers
of the Naxos type but there remained always the serious
disadvantage that these receivers did not supply range. It was
claimed that both Naxos and Korfu were so sensitive that the
bomber stream could be picked up at a range of 200 km. and
that in consequence useless chases often ensued. Estimates of
range had to be made by deduction and even in the case of
experienced crews the estimate of range by indirect means was
not always reliable.
10. Short mention is made below of another form of homing
device, the Kiel Z, which attempted to use the infra-red
radiations from the exhaust stubs of the bomber. A fuller
description of the Kiel Z was given in A.D.I.(K) 390/1945,
paras 41 to 48.
FREYA-HALBE.
11. The Freya-Halbe, officially known as the FuGe. 221, was
designed early in 1943 to home on to airborne Freya jammers
but owing to KAMMHUBER's opposition to freelance night
fighting was not adopted. Towards the end of 1943 when freelance
operations were introduced it was proposed to install
the twenty-five Freya-Halbe sets which had been manufactured
but, when they were indented for, it was found that the makers
had used various parts for manufacturing other apparatus and
that the sets had been virtually consumed as spares. Freya-
Halbe was, therefore, never used on operations.
ROSENDAHL-HALBE.
12. The first Monica set obtained by the Germans was
recovered from a British four-engined bomber which was shot
down over the town of Rosendahl in Holland and the name of
Rosendahl or FuGe. 221.A was then given to the D/F equipment
developed for homing on to Monica.
13. According to one of the P/W who had flown the trials with
Rosendahl, it was quite successful, and gave good D/F until
the night fighter came within 4 km. of its target, after which
the D/F became unreliable. For this reason the general
introduction of Rosendahl-Halbe was delayed.
14. It was ultimately discovered that the polarisation of
the receiver aerials was at 90° to that used by the bombers
and it was assumed that this was the cause of the poor D/F. For
some technical reason it was not found possible to twist the
aerial through 90° in order to obtain the right polarisation
and by the time that these difficulties had been overcome the
R.A.F. use of Monica had ceased.
15. An interesting experiment was carried out with Rosendahl-
Halbe when a set of Rosendahl aerials was mounted round a 150
cm. searchlight. The idea was to align the searchlight beam on
to an aircraft transmitting Monica. Considerable difficulty
was encountered in getting the searchlight beam and the axis
of the receiving lobe to coincide and by the time this had
being achieved R.A.F. bombers were no longer using Monica.
16. The Flensburg, officially known as FuGe.227, was another
attempt at solving the problem of producing a homer to D/F on
to Monica transmission. Difficulty was encountered with D/F
properties but the set was satisfactorily selective and could
discriminate between a large number of signals by tuning to
both the r.f. and p.r.f. It was used to a limited extent in
night fighter operations.
17. With the cessation of the use of Monica the original
Flensburg became known as Flensburg I and a series of other
F1ensburgs, numbered from II to VI, were manufactured to cover
the frequencies used by the mandrel screen and other Freya
jammers. The frequencies as given in documents were:-
Flensburg I 1.3 m. to 1.75 m. against Monica.
Flensburg II 1.7 m. to 2.6 m. against Freya A and B
band and Jagdschloss jammers.
Flensburg III
Flensburg IV
2.3 m. to 3.8 m.) against SN 2 and Freya
3.8 m. to 5.0 m.) C frequency jammers.
Flensburg V 25 cm, band against 25 cm. P.P.I. ground
radar jammers.
Flensburg VI 50 cm. band against Würzburg jammers.
18. It was not known to what extent these additional
Flensburgs had been used in operations. They were considered
to be a successful solution to the homing problem except for
the fact that the large aerials, particularly on the Freya
frequencies, reduced the speed of the aircraft considerably.
A.G.L.T.
19. The interrogation of British prisoners of war had
provided information with regard to Village Inn and some
details of it were known. It was thought to operate on a
centimetre wavelength and pieces of equipment had been found.
Nevertheless, P/W were convinced that though preparations for
using it had been made it had not yet been employed
operationally.
X-HALBE.
20. This was the designation of the airborne receiver which
could be adapted for D/F'ing any new metric radar that was
observed by the monitoring service.
NAXOS.
21. The Naxos, known as the FuGe.350, was a detector set
which received all transmissions on the 8 to 12 cm, band but
could not discriminate between different wavelengths in the
band.
22. The problem of producing a homer on to a beamed
transmission rotating at 60 r.p.m., as in the case of H2S, was
first tackled in March 1943, some two months after the
discovery of H2S. Little progress was made until an engineer
hit on the idea of getting continuous presentation of the
signals received by employing aerials rotating about twenty
times faster than those of the transmitter. The G.A.F. signals
staff were so impressed with the ease with which it was
possible to home on to a slowly rotating beam such as that of
the H2S that one of the requirements for the Berlin A was that
its rate of rotation in searching should be very high to
ensure that the Naxos solution to the homing problem could not
be employed against it.
23. The first trials with the Naxos were flown in December
1943 at Werneuchen and the first operational Gruppe to be
equipped with the set had it installed in all their aircraft
by the 25th January 1944.
24. A whole series of Naxos sub-types were produced and of
those the following were mentioned:-
Naxos Z. = (Zielanflug = Target Approach): was the original
homing device operating on the 8 to 12 cm. band; it could
not differentiate between frequencies in the band so that
if there was more than one H2S aircraft in the
neighbourhood, a confused picture was obtained.
Naxos ZR. (R Rückwärts = Backward): employed aerials placed
both above and below the after part of the fuselage of the
Ju.88 and served as a backward warning device for the
approach of British night fighters using Mark VIII or Mark
XI on the 9 cm. wavelength.
Naxos ZX. (X = X-band = 3 cm. band): was the 3 cm.
equivalent of the original Naxos Z. It operated on the 2.5
cm. - 4 cm. band.
Naxos RX. was the 3 cm. equivalent of the Naxos R and was
used as a backward warner against 3 cm. A.I.
Naxos ZD. was a combined homer for both the 9 cm. and the
3 cm. bands. The 3 cm. aerial rotated on the same axis but
above the 9 cm. aerials.
25. As stated, the value of Naxos was first appreciated by
crews in the early summer of 1944 when the increase in British
jamming had reached such a pitch that communications with the
ground were affected and it was difficult to find the bomber
stream. The picture obtained by Naxos, however, was nonselective
and it was not always possible to home on to a
single aircraft unless the aircraft in question was separated
from the others in the stream. On the other hand Naxos made it
easy to locate the bomber stream, which at that period was the
main preoccupation of the G.A.F.
26. Although estimate of range could be gained if the height
at which the bombers were flying was known, since, by climbing
and determining at what point the Rotterdam signals were no
longer picked up, the night fighter aircraft could judge the
distance of the transmitting aircraft. A full description of
the method of approach employed appeared in A.D.I.(K)
125/1945. paras. 93-98.
KORFU Z.
27. The original Korfu set, otherwise known as the FuGe.351,
was a development of a superhet receiver designed for
frequency modulated 9 cm. carrier communications purposes.
After the discovery of H2S it was adapted for use by the
German "Y" service and towards the end of the war was further
modified for use as an airborne set and then became known as
the Korfu Z or FuGe.351Z.
28. The aerials employed were of the Naxos type and gave the
relative bearing of the transmitter but the advantage of the
Korfu Z lay in the fact that it could be sharply tuned and
could, therefore, home on to individual aircraft.
29. It was also hoped that with the help of the Korfu Z night
fighters would be able to differentiate between H2S and 9 cm.
A.I. which the Germans presumed used different sections of the
9.0 to 9.3 cm. band. In this connection, as mentioned in
A.D.I.(K) 363/1945, it was hoped in due course to produce the
Berlin and other German "9 cm. " radar on the 8.6 to 8.9 cm.
band in order to aid German night fighters to differentiate
between British and German aircraft.
30. The Korfu Z was to have been ready by mid-summer of 1944
but its advent was delayed by the shortage of magnetrons, all
available specimens of which were required for the ground
Korfu used by the "Y" service. So far as was known the Korfu Z
was never used operationally.
Kiel Z.
31. The Kiel Z was manufactured by Zeiss and known officially
as the FuGe 280. Infra-red radiations from the exhaust stubs
of aircraft were picked up in a parabolic mirror and focused
on to an Elac lead sulphide cell. The field of view in a cone
of ± 10° was scanned. A wider field of view could be obtained
by moving the entire scanner by hand in the same manner as
employed with the Berlin M.1.A.
32. Shortly before the end of the war a number of Kiel Z sets
were tried out in operations but it was found that, although
they gave a range of about 4 km. on a four-engined bomber,
various difficulties arose. Infra-red radiations from the moon
and stars formed "permanent echoes" on the cathode ray tube
used as viewing screen, and were not always easily
distinguished from a moving aircraft. In addition, if the
target aircraft was between the fires caused by the raid and
the night fighter aircraft, the target was obviously quite
indistinguishable against the background of the fires.
33. Night fighters equipped with the Kiel Z were also to
carry the FuGe 218 Neptun R3 backward warning radar so that
they at least had warning of British night fighters
approaching from the rear.
FALTER
34. Falter was an infra-red telescope of the Bildwandler type
used by German night fighters for homing on to British infrared
recognition lamps. Reference to Falter appeared in
A.D.I.(K) 365/1945, paras. 72-76. It was not known if it had
been used operationally.
A.D.I.(K)and S.D. Felkin
U.S. Air Interrogation. Group Captain
2nd August 1945"

[Marcel van Heijkop]

Originally Posted by Dan O'Connell

Amazing.

The story of I./KG66 is indeed amazing!

Best regards,

Marcel
(I./KG66 Research)

[RudiS]

Very interesting reading. Thanks for that.

Paragraph #74 of post #178 is probably responsable for the rumor that initially KG 54 was to convert to the Ar 234 in stead of the Me 262.

Originally Posted by Nick Beale

would people like a dedicated "Researching the Luftwaffe through Prisoner Interrogations" thread?
[/url]

I know I would, Nick.

[Dan O'Connell]

Fascinating, especially by U.S. Air Interrogation.

[ju55dk]

ADI K 065 5/NJG 101 Ju 88.
Junker

[Bruce Dennis]

"(49) A.L. No. 19 (Sheet 2) 29/9/45
Interrogation of Baron Von Schalcky CIOS File 24-15

JAGDSCHLOSS
The original plan for Jagdschloss provided three models
covering the following frequency ranges; 75 to 120 Mcs; 120 to
160 Mcs. Jagdschloss A was actually operated between 130 and 160
Mcs, with a frequency change requiring only five seconds. This
frequency change was among a choice of four pre-set frequencies
in which the proper dial settings for transmitter, receiver, and
TR-antenna coupling systems were indicated with special markers.
The antenna was designed to work over a two to one frequency
range with the limit set by tactical requirements rather than by
standing wave ratio.
Jagdschloss was first used in April 1944 and by February
1945 it was felt that the Jagdschloss coverage of Germany was
complete and with considerable overlap. The normal usage of
Jagdschloss was described as "Luftlage"; that is, it was used
for early warning and to maintain a watch of all aerial
activities. It was used in this capacity to assign targets to
either ack-ack control or GGI installations and, as noted below,
was used directly for fire control under some conditions.
The maximum range ever obtained on a Jagdschloss was said
to be 250 kilometers on an 8th Air Force formation. Ranges of
180 to 120 kilometers could be obtained normally. However, these
ranges were obtained with the A scope which was normally used
for tuning and testing purposes. In normal operation for
Luftlage, the range of Jagdschloss was limited by the 120
kilometer sweep length on the Sternschreiber (P.P.I.)
In the Berlin area on several occasions during August and
September 1944, Jagdschloss data was used directly for fire
control. This was done by assuming the altitude shown by our
bomber formations to be a constant which was found statistically
to be quite an acceptable assumption. Then the range and azimuth
of the formation was obtained by Jagdschloss and appropriate
data was transmitted to the flak batteries. The battery then
fired a controlled barrage, setting the fuzes in such a way as
to cover about 2,000 foot altitude spread. The Baron said this
procedure was considered very effective against our 8th Air
Force bomber formations. Incidentally, the Baron was well
acquainted with our division of bomber activities and was
familiar with 8th Air Force organisation and procedure.
Jagdschloss was fitted with a remote transmission system
which transmitted the Sternschreiber picture up to 150
kilometers OVER WIRE TRANSMISSION LINES. No specific mention of
direct use of this facility was made.
Several Jagdschloss radars were in various stages of
development: One of these sets was the 50 cm set on which the PW
had been running tests. This was another Jagdschloss by Siemens
Company. In addition a 25 cm set of similar characteristics had
been developed by Telefunken and was known as Forsthaus F. This
set used a conventional type tube in the transmitter known as
Scheibenröhren. The details of its construction were not known
to von Schalcky. A 9 cm. Jagdschloss set, known from other
sources as Forsthaus Z, was also in development by Telefunken.
The PW indicated that Forsthaus was the Telefunken name for
"Luftlage" radar whereas Jagdschloss was the name used by
Siemens. The effort on these radar developments was to obtain
higher discrimination so as to provide less susceptibility to
Düppel. Von Schalcky was of the opinion, however, that going to
narrower beams, although it provided a smaller pulse packet and
thus higher discrimination, caused sufficient loss of target
return due to the shorter length of time that a target was
illuminated as the radar antenna rotated, to set a limit to this
technique. His reasoning is probably correct if one considers
the low peak powers used in precision German radar. The PW also
had the opinion that the higher frequency sets (above 1000 Mcs)
were less satisfactory for early warning due to what he called
"Troposphere" reflections.
Several anti-"Düppel" (anti window) measures had been
developed and were being tested on the 50 cm. Jagdschloss. It
was interesting to note that the procedure was to utilize 8th
Air Force Window for test purposes rather than bothering to drop
their own.
1. Phosphor clearing device.
This was a simple expedient which was made necessary by a
characteristic of the Sternschreiber phosphor. Apparently the
decay time was so long that Window echoes would tend to build up
large, fully, illuminated areas giving a sort of compound
jamming effect over a period of time. The expedient was to turn
off the beam for one or two rotations of the antenna system and
to radiate the screen from an infra-red source during this off
period. The existing echoes were thus erased. Equipment for
doing this automatically was just being completed.
2. Film frame comparison method.
Exposure of two successive frames of the Sternschreiber
presentation were made on the same piece of colour film. The
exposure for frame A was made with a red filter and exposure
frame B was made with a green filter. Each rotation required six
seconds, thus the total exposure required 12 seconds. The
equipment for doing this job had been developed and built by
Zeiss. The existing development model had been destroyed by von
Schalcky at Heidhof. The equipment was arranged so that one
minute after the exposure, the colour film could be projected on
a screen. Due to the additive effects of green and red, fixed
echoes appeared as black marks or "streams". However a moving
target in which the succeeding exposures were displaced in
accordance with the motion appeared as a "beetle" having a green
head, black center, and red tail. The green, of course, points
in the direction of motion.
Von Schalcky distinguished between heavy 8th Air Force
daylight window and thinner RAF Window. Heavy Window gave
definite black areas or "streams". However, Window occurring in
small separated clumps sometimes gave the effect of motion due
to the random shifting of dipole orientation with consequent
random displacement of the effective center of the Window cloud.
This effect was considered a disadvantage of this
particular A/J system, the principal aim being to enable
distinction of fixed and moving targets.
3. A frame storage moving target indicator method was being
developed and had undergone preliminary tests. An iconoscope
mosaic storage was employed. The Baron did not think that this
method used coherent pulse. The same disadvantage of the
difficulty of distinguishing between aircraft and small clumps
of Window was encountered as in the case of the photographic
method.
4. Siemens was developing an adaption of the Laus or coherent
Doppler to Jagdschloss, the intention being to alter the display
of moving targets on the Sternschreiber, allowing fixed echoes
to be presented normally. A third detector circuit derived a
pulse signal from the beating Laus of a moving target. This
pulse was applied to the radio deflecting system in such a way
that moving targets tended to trail in towards the center of the
tube as shown in the sketch below.
The Sternschreiber tube had a double phosphor similar to
our P-7, in fact, adapted from the P-7. The flash trace is blue
but in the Sternschreiber the afterglow is green and apparently
of longer duration than our yellow. Von Schalcky did not know
the chemical details of this phosphor. He thought a persistence
of ten minutes was obtained.
Comment was made that our daytime 8th Air Force jamming was
picked up often on the 50 cm. experimental Jagdschloss and that
it was never possible to see aircraft in the jammed sector on
the Sternschreiber.

B. Freya.
The Dreh Freya was considered very inferior to Jagdschloss for
general search and coverage because of the serious nulls in the
vertical antenna pattern.
The modification of the Freya Laus, known as "Windlaus",
was designed to enable cancellation of any particular Doppler
beat caused by wind drift of the Window. Two oscillators were
used, one to lock the transmitter frequency and a second for
comparison in the receiver. The frequency of the receiver
oscillator could be adjusted independently so that a particular
Doppler frequency produced no output, thus wind-blown Window
echoes would not appear as a Laus presentation, whereas fast
moving aircraft would still be detected as moving targets. This
was said to be in use on a considerable number at Freya
installations.
The use of centimeter listening receivers, either, on Freya
mounts (as at Kothen airfield) or in separate installations, was
quite common as an early warning system for detecting the
approach of H2S or H3X.

C. Fire Control Radar.
The PW stated that the Würzburg Frequency spread was 63 to
50 cms (476 to 600 Mcs). He stated this twice, and was rather
positive on the point.
Gustav is a code name for Würzburg Riese G and consists of
Freya radar added to the normal Riese. Freya equipment is
located in the far end of the can necessitating very slight
alteration in the normal layout. Two antenna arrangements are in
use, in one a single vertically polarized radiator one wave
length long being mounted in front of the normal Würzburg
antenna and using the normal Würzburg reflector to obtain a
measure of directivity. The second arrangement utilizes two
dipoles one on each side of the normal antenna, again vertically
polarized. Von Schalcky did not believe that reflector elements
were used with this antenna arrangements and that the Würzburg
dish was the only other element involved. In addition to Riese
G, there was a variation with a broadband Freya installation
known as the Riese G-la. The use of these combinations as
understood by this PW was simply to aid in putting the Würzburg
on target. He did not believe they were used for range, only
A/J.
The Mannheim was preferred over either Würzburg for
tracking in normal conditions but it was considered less
effective in the presence of jamming than the Würzburg. This was
attributed to the ability of a good operator to interpret a
jammed scope on the Würzburg, a procedure impossible in the
Mannheim meter presentation. It appeared the Mannheim scopes
were not usable where jammed. The use of aided tracking on the
Würzburg D, on the Riese, and on the Mannheim, was common as a
measure against jamming which was not effective all the time. A
fixed tracking rate could be set in by the operator.
Von Schalcky did not know of any centimeter fire control
sets.

D. Fire Control Procedure
With regard to predictors used for fire control
computation, von Schalcky knew only of the KG-40. He understood
that the preferred SOP was to use optical direction and radar
range in all possible circumstances including night operations.
In this connection, the small Würzburgs were used for
searchlight control, the optical system built in the KG-40 being
then applied for final direction finding. Using the Riese, he
thought it was nearly always possible to obtain slant range in
the presence of our jamming. He felt that the KG-46 was still
the most widely used predictor in the GAF defense system.
Use of Wurzburg Riese and Riese G's for fire control was
said to be quite common and extensive.
A procedure for utilising data from several different
radars as in the Gross-battery was mentioned. In this, a
specially trained operator surveyed Selsyn relayed data from the
several radars associated with the battery and mentally selected
and averaged the best appearing data. That is, if two radars
were producing roughly the same information but a third was
giving different indication, he would utilise the data from the
two more consistent sets, delivering this information by phone
to the KG-40. With this installation, which was said to be
fairly common, it was thus possible to change instantly from one
radar to another for control purposes.
In a defense area such as a city or other specific target,
all defenses were controlled from a central Kommand post. A
Jagdschloss was associated with this Kommand and was used in
assigning targets to ack-ack or fighter defenses. In addition,
Wassermann or other height finding radar would usually be
associated with the Jagdschloss. In the case of fire control, if
the battery was unable to track an assigned target because of
jamming, it was usually instructed to fire a barrage on the
basis of Jagdschloss data. In a few cases, arrangements were
made for relaying information between adjacent batteries by
phone but the P.W. did not believe this to be as common as the
practice of using Jagdschloss data. Provisions for automatic
transmission of data between batteries had been worked out but
were not in common use.

E. GGI Procedure.
Naxos had been in use since April 1944 for homing on
British H2S radar.
The practice of triggering our IFF from both ground and air
installations was common and, it was felt, quite successful.
Also few night fighters had recently been fitted out for
triggering what must have been Oboe Mark II in the RAF planes.
Automatic Seeburg was not liked as well as the manual
because of the roughness of the data plotted when a radar would
"spring" or deviate from the true tracking course. A manual
table allowed smoothing in the process of manual plotting.

F. Allied RCM.
As-noted previously our jamming was not considered
effective in jamming range on the Riese. However, against
Würzburg D and Mannheim, the combination of Düppel and
Störsender was quite effective, especially after October 1944.
Screening of Freya was more effective in night than in the day
time but was never considered a serious effort. This PW had the
understanding that screening was also directed against
Jagdschloss and knew of cases where Allied planes had circled a
Jagdschloss site continuously during operations in that
vicinity. The overlapping coverage of Jagdschloss made it
possible nearly always to obtain the necessary information,
though a particular set was out. The maximum range of
Jagdschloss as used operationally was 120 kilometers.

G. Centimeter antennas.
The PW knew of the poly-rod antennas used in Naxos and the
use of a parabolic reflector copies from H2S. The parabolic
reflector antennas were chiefly by Siemens.
One other type of centimeter antenna of interest was a
slotted wave guide as shown in the sketch.
The slot is tapered to provide uniform radiation from all
sections of its length. This was Telefunken development, known
as Holstraehlen.

(47) A.L.No.14 (sheet 20) 24.9.45
Magnetrons & Klystrons
Interrogation of Drs. Kleen, & Lerbs by Mr. Griffing,
Major Ravenel,
F/Lt. F. R. Holt.
(Evaluation Report 139)
Dr. Kleen was head of the Telefunken Tube Research
Laboratories, recently at Berlin. Dr. Lerbs was in charge of the
Magnetron group under Dr. Kleen.

Most of the German centimeter tube development has been
made in these laboratories, which were for some time in
Liegnitz.
The first 10 cm. equipment. "Rotterdam" was operational
between 6 and 12 months ago; since then further marks of this
(known as X1 and X2) also "Berlin" and "München" have been
developed. The magnetron used, LMS 10, was a copy of the allied
one. The 3 cm. ones produced were claimed to be their own
development. The LMS 10 was 30% efficient. The LMS 100 up to 100
kW, also on 10 cm. was 10% efficient and had a field of 1500-
2000 Gauss, 30% greater than critical. It was air cooled and was
suitable for space/mark of 1000. The LMS 12 on 3 cm. had 18
splits, the L.M.S was 3 cm. tuneable, and water-cooled, with 2
kW loss. Small receiver magnetrons are the RD2MG (3 cm. 6 or 8
splits, 50 kW output, short life), the RD2MH, and the RD4MG,
This series contains about 10 other types. They have only used
Copper Magnetron anodes recently, have had trouble with glass
sealing (usually Nickel-iron soldered to the copper with Silversolder
was preferred), and have only recently found a
satisfactory method of pumping the LMS 100. For power
measurements up to 10 watts, they used the heating effect on a
resistance wire forming part of the Wheatstone bridge; above
that, water-flow methods.
Most of the tunable Magnetron work was done on 3 cm. They
used a metal ring supported on a flexible membrane and moved
towards the circle of gaps. Some magnetron development was done
by Sanitas GmbH, and possibly the Reichspost at Heidelberg. They
were produced by Telefunken at Berlin and Reichenberg in
Eulengebirge, and also by Sanitas and Getewent.
Most of the work on Klystrons was done in Prague by Dr.
Labos of the B.H.F., Telefunken have made 3 cm. all metal (that
is, main body) Klystrons and have been experimenting on 1 1/2
cms. These are reflected beam tubes. The following ceramic and
metal grounded-grid triodes have been made:-
LD7, LD9, LD11, LD13, LD70, LD90, LD110, a development of
LD10, LD120, LS1000, and a diode of similar construction
LG11. (They prefer however use a crystal detector up to
20 cm. LD12 was used in "Berlin", and LD11 in "Euclid" a
27 cm Navy equipment.
With the triodes they have obtained 10 kW peak power with a
space/mark from 5 to 10. This was of course in jammers. Names of
jammers mentioned were "Anti-Boomerang" i.e. Oboe "Anti
Rotterdam" i.e. H2S and any equipment with name beginning with
"Feuer" e.g. "Feuermolch" and "Feuer-Zauber". These jammers are
said to have been used operationally in small numbers (10 to 20
equipments.)"

[Bruce Dennis]

"ITEM N° 21,22,31
FILE N° XXXIII-36 SECRET UNDERGROUND FACTORIES IN GERMANY Reported by C.I.O.S. Party 536

(L) HAMMERWERKE FACTORY, near Hausberg Porta Westfalica, Minden
This factory, of the multi-storey type, was constructed in underground quarries on the East side of the Weiser gap south of Minden. The quarries were situated in the Porta Sandstone above the Dachs I Refinery, and had been enlarged by the Gewerkeschaft Porta to house the Phillips Radio Valve factory from Eindhoven, in Holland.
Constructional work is said to have started in March, 1944 and to have been completed in September, 1944. Production started in February, 1945.
Contracts
The following were interrogated-
Herr Goosens, engineer, Dutch, speak English.
Herr Pott, mining engineer, manager of the Gewerkeschaft
Porta.
Herr Haupt, formerly engineer on plant installation now custodian of the factory for the military Government

Geology
The geology of the area has already been described in the
sections dealing with Dachs I and Denkmal Stollen. The Hammerwerke factory nine storeys high was constructed in the Porta sandstone (photograph No. 21) and being south of Dachs I was at a higher level as a result of the dip of this stratum as can be seen in the geological motion attached to this report (Fig. 8A.) The two factories were to have been connected by an internal shaft.
There was no evidence of rock falls in the factory area.

Lining & Support
The workings were for the most part unsupported and the rock surface only whitewashed. At a few points steel joists and timber laggings had been used.

Excavation
The little excavation done on this site was carried out simultaneously with Dachs I and no separate data was available on labour, costs or progress.

Entrance
The main entrance, on the seventh floor, was protected by a blast wall of concrete 1.1 metres thick, and was connected with the main road at Hausberg by funicular railway.

Water Supply
Process water was pumped from the River Weser. Water was available from the town supply.

Sewage Disposal
Sewage was disposed by gravity into the Weser after treatment.

Air Attack
There was no evidence of air attack on this site.
Engineering Services
(a) Heating
The Boiler House was located on the surface at road
adjacent to the entrance of the Porta (Dachs I) factory.
The boiler was of the horizontal type in three sections:-
1. Cornish boiler design with corrugated flue.
2. Section comprising smoke tubes.
3. Smoke box section.
Steam was taken off the middle section, which was also provided with dead weight safety valve, and thence proceeds to
the super heater section located round the crown of the smoke box.
Steam and condense mains were taken through the entrance of the Dachs I factory and thence by means of a sloping tunnel up to the ground floor of the Hammerwerke Factory and to the various steam heater batteries associated with the ventilation plants.
(b) Ventilation
Six separate plenum extract systems were installed all of similar character and dealing with the floors in groups. Each system draws fresh air from, and discharges vitiated air to, the cliff face.
Each inlet system comprised a main inlet fitted with a wire grill leading into a concrete spray chamber thence to an eliminator and finally to the fan chamber. The water sprays were not connected, but it was clear that they were to be supplied with water from the main supply and that this water would be rejected to waste.
Two types of delivery fan were used:–
1. Double inlet type in an enclosed fan chamber following spray and eliminator chamber.
2. Single inlet fan with duct connection to the spray and eliminator chamber.
Each inlet fan discharged into a main delivery duct constructed in building board, at the respective ceiling level, and vertical metal ducts were taken down to floors as required with adjustable discharge openings near each floor level.
Vertical extraction ducts with inlets at high level, as required, were connected to a main extraction duct, also constructed in building board, running adjacent to the corresponding main fresh air delivery duct. The main
extraction duct was connected to the extraction fan chamber and thence to atmosphere. At the time of the inspection all fans were running but heater batteries and water sprays were out of commission. Condensation was evident on the lower floors but the general state of the factory suggests that production heat energy in conjunction with the use of steam heater batteries had resulted in a reasonable air condition.
(c) Electric Power and Lighting
The electric supply was taken from the sub-station at Porta (Dachs I) at 6,000 volts and the high tension cables were brought up through the service tunnel and taken to four transformer stations. The voltage was than transformed from 6,000 volts to 400 volts 3 phase 4 wire, each of these transformers was rated at 800 KVA.
Low tension feeder cable were taken as risers to metal closed cabinets containing main switches, fuses, circuit breakers and relays.
Circuit wiring was taken at high level and in general was supported by a series of galvanised multi-strand steel cables which also served as earthing wire collectors. Each steel cable was thoroughly bonded to the rising watermain.
Drops to machines and table inspection lights were taken from special metal junction boxes with porcelain interiors.
All metal parts and components were earthed on to the galvanised straining cables by means of single strand cables, approximately No. 18 gauge.
An attempt was made by interrogation to gain information regarding the type of earth leakage system installed but the only information offered was that every power unit had a leakage trip and that transformer were earthed at the star point.
The general illumination and local bench lighting were of a high standard for example 4 kilowatts of lighting load has been installed in an inspection bay approximately 25' x 25'.
(d) Fire Protection
Fire hydrants complete with hose reels were provided in metal cabinets fixed to walls and connected to the rising waterman. Portable fire extinguishers were also provided.
(e) Gas Installation
Gas for process work was obtained from the town supply and the installation followed conventional standards for the class of work under consideration.

Production and Layout
This factory consisted of nine floors with layout as shown on the attached print and situated in the same hill as the Oil Refinery, Dachs I, which is the subject of a separate report. This factory was first put into operation in February, 1945 when
it was intended to reinstate the production hitherto obtained from Philips Eindhoven factory, Holland. All plant and equipment even down to the inspection benches and stools were transferred from Eindhoven. This factory was very impressive in so far that there was ample spacing, and lighting was particularly good.
The ultimate production was to have been 12,000 radio valves per day, but it was ascertained that up to the date of ceasing production, some 7,000 serviceable valves only had been issued. This in no way represents the total number of valves actually manufactured since it was made clear by the Production Engineer (Dutch) that the number of defective was considerable and this in the main was due to inclusion of dust at the final assembly stages. It should be appreciated that this dust trouble would not be discernible by casual observation. Nevertheless, the question of dust did not apparently interfere with the manufacture of component parts nor did it affect work carried out in the tool room and maintenance shop. Walls had been whitewashed but not otherwise treated or lined.
The total labour force spread over three shift would have been 1,200/1,400, the vast majority being female, mainly young Jewish girls from concentration camps. Three shifts were arranged via:- two of 6 hours, and one of 8 hours, the break coming between 3.0 am and 7.0 am.
Production arrangements were as follows :-
lst floor - Toolroom and general maintenance shop. This plant was in first class condition, amply spaced and machines were of first class make, including several American tools such as Gorton and Milwaukee Milling machines. This floor also housed the gas production
mixing plant required in production and was distributed to the required stations on the other floors by normal pipe distributing system.
2nd floor - This was essentially devoted to grid rolling and all the requisite plant for this operation had been installed and its condition was good.
3rd floor - Allocated to component assembly. This floor was also used as a main stores for component parts.
4th floor - Mainly for assembly and testing.
5th floor - This was laid out for the drawing of filament wire. and testing, but it was obviously not yet in full production. A side gallery on this floor was occupied by a separate firm, Carsten of Hamburg, who
were apparently responsible for stamping out the mica parts which were subsequently used by Philips in the assembly.
6th floor - Had no defined use at the time of visit, except for a few offices and it was understood to have been used as sleeping quarters.
7th floor - This was the main entrance and exit for the whole factory, and contained a certain amount of plant for preparation of cathodes and filaments.
8th floor - Preparation of cathodes and filaments.
9th floor - This was used for offices and ablution, and had a small exit probably used by staff only.
Access for employees to the respective floors was by stairway, and for goods, a lift 4 x 3 metres and having a capacity of 5,000 kilograms was installed to serve floors 1 to 7.
The only external access provided to this factory from the main road was by means of a funicular railway which terminated at the level of floor 7 and about 200 ft. from the tunnel entrance."

[Bruce Dennis]

"SECRET A. D. I. (K) Report No. 394/1945
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.

G.A.F. INTELLIGENCE IN THE WAR – II.
Sources and Dissemination of Intelligence.
1. This, the second report of the series dealing with G.A.F.
Intelligence during the War, is based mainly on the interrogation of
Hauptmann ZETZSCHE who, during the Period of Major WODARG's office, was
in control of Gruppe A of the department "Foreign Air Forces West" under
Chef Ic.
2. The infuriation set out in this report falls into two main headings
of "Sources" and "Publications". The paragraphs dealing with the German
"Y" Service as a source of intelligence have been purposely reduced to a
minimum, since a series of eight reports covering that subject alone is
to be issued shortly by A.D.I.(K).

SOURCES OF INTELLIGENCE.
FOREIGN AIR FORCES WEST.
3. The department of Foreign Air Forces West, under Major OWE (see
A.D.I.(K) 393/1945, Appendix IV) and with a staff of about 100, was
responsible for covering Great Britain, the Empire, the U.S.A., France,
Switzerland, Spain, Portugal and the Middle East.
4. The two Gruppen of the department "A" and "B", dealt respectively
with military aspects and political and economic questions. In spite of
the far greater commitments of Gruppe A, departmental strength was
equally distributed between the two Gruppen.
5. The following are the sources upon which Foreign Air Forces West
depended for collation of intelligence.
German "Y" Service.
6. The German Y-Service - Abteilung 3 of General MARTINI's staff –
supplied collated data to Chef Ic. In spite of Generalleutnant SCHMID's
complaints of that department's methods of working (see Part I para.
31), Hauptmann ZETZSCHE stated that this source provided extensive data
for Allied Order of Battle, subordinations and chains of command,
operations, radar developments and ferryings of aircraft from the U.S.A.
7. Four sub-sections of Abteilung 3 covered all aspects of Allied
activities, and issued daily intelligence summaries which were
telephoned or teleprinted to Chef Ic. Ten-day and monthly appreciations
of Allied activity were also issued, the latter containing valuable
Statistics of Allied incursions.
8. One section, Chi-Stelle (codes and cyphers) Referat B covered all
radio and radar intelligence on the western front such as details of
current air operations, including Gee-H and Oboe attacks. The southern
front was similarly covered by Chi-Stelle Referat C, and a sub-section,
Referat C-1, dealt with Allied transport and ferrying traffic, this
latter was of special value to Ic in assessing Allied production and
losses.
9. Radar intelligence from both Western and Southern fronts was
collated by a section known as Funkleitstand. A monthly report was
issued which was of great help to Ic in assessing Allied radar and the
effects of German jamming. A liaison officer was maintained by
Funkleitstand with the P/W Interrogation Centre at Oberursel for the
purpose of clearing up obscure points by interrogation of Allied
aircrew.
10. Another section, the Zentrale Funkaufklärung (ZAF) was set up at
Treuenbrietzen for tactical evaluation of radio and radar data received
in the area of Jagdkorps I. As this section was solely concerned with
tactical considerations, its relations with Chef Ic were not close.
Prisoner of War Interrogation.
11. Excellent results were obtained from the close co-operation with
Auswertestelle West - formerly Dulag Luft; collated reports resulting
from detailed interrogation of Allied aircrew provided valuable matter
for Ic publications as well as for filling in gaps in Order of Battle,
etc., left by the "Y" service, and supplying the Y-Service itself with
working data.
12. The actual methods employed by the Germans in the interrogation of
their prisoners has been set out in detail in A.D.I.(K) 388/1945. It is
perhaps worth recording that Oberst WODARG was frequently caused no
little embarrassment as a result of Generalleutnant SCHMID of Jagdkorps
I being on the distribution list for P/W interrogation reports; SCHMID
usually had his copy first, and WODARG found it disconcerting to have to
tell GOERING things he already knew.

Air Reconnaissance.
13. The G.A.F. strategic reconnaissance effort was limited by lack of
fast aircraft types. During the period leading up to the invasion,
reconnaissance of England by day had been practically nil; at the end of
May 1944 two Me.109's succeeded in carrying out a probing reconnaissance
of the Isle of Wight under cover of cloud and an American four-engined
sortie. The invasion fleet in Southampton was covered only once -
whereupon a night attack by Fliegerkorps IX followed. Beyond a few
isolated daylight efforts, reconnaissance results consisted entirely of
night flash bomb cover - mainly valueless - and visual reconnaissance by
Me.410's.
14. With the introduction of the Ar.234 subsequent to the invasion, the
situation improved steadily. Airfields, harbours, London etc. could then
be effectively covered. Nevertheless there were still too few aircraft
(three names of pilots only were to be read on aerial photographs), and
the enemy picture obtained continued to be only a partial one. This
state of affairs was partly due to the emphasis placed on tactical
reconnaissance, the results of which were of interest only to the Army
and G.A.F. operation commands.
15. Scientific evaluation and appreciation of aerial photographs by Ic
was made difficult through bad organisation, the G.A.F.
Hauptbildabteilung being subordinated to the General der
Aufklärungsflieger.

Fremde Heere West (Foreign Armies West) and 3 S.K.L.
16. Ic placed great value on the information on Order of Battle,
subordinations and directions of thrust of Allied ground forces supplied
by Fremde Heere West, which for its own part found the Ic enemy air
situation report extremely useful, in that the Order of Battle of air
ground support units showed a clearer cut and timelier picture of enemy
intentions than the movement of military ground forces.
17. Fr.H.W. issued extremely good appreciations. Alone with Ic/West it
pointed continually to the probability of one sole landing on the
Normandy coast, in opposition to the firm Wehrmachtsführungsstab belief
in the likelihood of a second landing in the Straits of Dover.
18. Intelligence received from 3.S.K.L. the Naval liaison unit, was for
the most part scrappy, owing to the dearth of information regarding the
occupation of Allied harbours and the distribution of the Allied navies,
landing craft and merchant fleets.

Reports from Operational Commands.
19. Ic officers at the front complied only partially with Chef Ic's
requirements, owing to a variety of reasons, such as Chef Ic's lack of
personal influence, the sometimes poor quality of the Ic officers
themselves, and the emphasis placed at the front on the reporting of the
enemy’s actions rather than on knowledge about him, such knowledge being merely designated as enemy propaganda.
20. The main teak of Operational Command Ic's was to teleprint to Ops.
Staff In a current enemy situation report, comprising Order of Battle,
operations, tactics and any special considerations such as possibilities
of air landings, invasion eta. These reports were, however, only
forthcoming at irregular intervals and even then seemingly with an ill
grace. Thus, with the exception of the Luftflotte 3 Ic appreciation
prior to the invasion, Front Ic reports could not be considered as a
regular source of intelligence comparable with Auswertestelle West or
the W/T Listening Service.
21. A further duty was also neglected by Ic's at the front, that of
passing up Staffel reports to Chef Ic and passing down Chef Ic reports
to the Staffeln. Instead, every month each Operational Command
painstakingly produced its own comprehensive report of the air situation
carefully printed and edited and covering enemy incursions, operation.,
Order of Battle strength, subordination., etc., the figures naturally
differing between one Command and another, and from those of Chef Ic who had other sources at his disposal.
22. As for the sources available to Operational Commands, on which the
reports were based, Oberstleutnant OHLETZ, one-time Chief Intelligence
Officer of Luftflotte 6, gave the following as sources available between
January 1941 and March 1943:-
i) The Luftflotte tactical and strategical reconnaissance units.
These were at the disposal of the Ic as and when required.
ii) A signals intercept unit for the Luftflotte 6 area.
iii) The interrogation centre for Russian flying and Flak personnel.
iv) A photographic unit.
v) Evaluation of battle experience of Luftflotte 6 units.
vi) A captured equipment evaluation centre.
vii) Current data from adjacent Luftflotten.
viii) Reports from Ic-Heer, supplied by the Army Group Centre.
ix) Reports from the Military Intelligence Service affecting
Luftflotte 6 area.
23. OHLEZ states that results of a tactical nature were distributed by
him to Luftflotte 6 units. Full details were sent to O.K.L. Ic and Army
Group Centre, and brought to the daily conferences of the Flottenchef
with his Chief of General Staff and officers in charge of operations.
24. It is therefore not difficult to understand why Operational Command
Ic's with such resources at their disposal and in view of their special
operational commitments, should feel themselves independent and to some extent intolerant of control by Chef Ic, and why Chef Ic on his side,
with responsibility for the accurate assessment of the full enemy
situation, and viewing the situation solely from this standpoint, should
maintain that Ic's at the front were overstaffed and negligent of their
true functions.

Evaluation of the Press.
25. Each Intelligence organisation in Germany made its own arrangements
for the procuring and evaluating of foreign newspapers and periodicals.
Chef Ic obtained its papers either through the R.S.H.A. or the G.A.F.
Air Attachés in Bern, Stockholm and, up to 1944, Madrid, Lisbon and
Ankara; Papers were at least four weeks out of date when received owing
to poor R.S.H.A. organisation. American newspapers and periodicals were
received only occasionally and in small numbers. Luftwesen was
responsible for supply within Ic, and thus provided a further cause of
delay.
26. Intelligence was extracted from press reports concerning
personalities (e.g. from "Aeroplane, "Tatler" and "Sphere"), production
figures, photographic material, tactics and economics matters.
Technical Intelligence.
27. Enemy aircraft armament was covered mainly by Chef Technische
Luftrüstung section A/Rü, and Ic could neither guide nor co-ordinate its
work. Generally speaking, A/Rü took upon itself to keep industry and
Operation Commands informed, Ic serving to pass its reports down to unit
level.
28. These reports mare very good and complete, but came much too late
to be really valuable, since TLR-Rü invariably waited until the last
details were known on any subject before issuing a report upon it. For
the same reason Ic only received at long and irregular intervals reports
on Allied aircraft shot down.

Broadcast Monitoring.
29. Of special interest and value were the broadcast links between the
news agencies and their correspondents in the various capitals of the
world. Of broadcasting stations, the B.B.C. and Swiss stations were
considered the most reliable, Daventry in particular being appreciated
for its figures concerning Allied sorties and losses. Indeed, during the
period between the invasion and collapse, BBC reports were often the
only source of reliable information on the war situation.
30. Radio monitoring was done by O.K.W.-Chi, its Naval counterpart the
Seehausdienst, and the Forschungsamt, the results being sorted out and
distributed by Ic/Luftwesen.

Agents.
31. The complete failure of the German Agent Organisation as a source
of reliable information was attributed by ZETZSCHE to the following
causes:-
i) The unsuitability of personnel both at home and abroad.
ii) Lack of agents in high positions.
iii) Many agents inspired by British Intelligence, e.g. Hector,
Josephine probably, and Ostra for certain.
iv) No agents in America.
v) Agents' reports evaluated and issued without reference to Ic,
final judgment on them being passed by Abwehr I/Luft (later
R.S.H.A. Mil.Amt).
vi) The splitting of the Agent organisation between Haupt Amt IV
and Haupt Amt VI of the Mil.Amt, thus giving rise to two
separate organisations abroad.
vii) The final assumption of control by the S.D. causing the whole
organisation to fall to pieces, and the flow of useful reports
to cease altogether.
32. Liaison was maintained with the Militärisches Amt through Oberstleutnant von DEWITZ. From the middle of 1944, however, agents' reports were not passed out to Commands owing to their proved unreliability.

Attaché Reports.
33. Attaché reports came from Amtsgruppe Ausland (Admiral BÖRKNER) of O.K.W. which passed to Ic important reports from military, Naval and
G.A.F. attachés, as well as direct from Air Attachés in neutral
countries, organised by the Ic Attaché Gruppe.
34. For the most part attaché reports consisted of descriptions of
economic conditions and morale abroad, sometimes amounting to no more
than translations of newspaper reports. Little of any value was ever
received concerning England, France or U.S.A. On the other hand attachés
often swallowed whole rumours issued by the Allies for German
consumption, e.g. rumours concerning the imminent invasion of Norway,
the Balkans, etc.
35. Air attaches were not held in very high esteem partly owing to
their being considered poorly chosen for the task and partly owing to
lack of firm direction by Ic (Luftwesen).

Diplomatic Reports.
36. Reports from the Foreign Office and agencies abroad came to Ic both
through Amtsgruppe Ausland of O.K.H. and through the Ic Liaison Officer
with the Foreign Office, Hauptmann EHRENHAUS (Ic/Luftwesen/Pol). They
were of little military value.
37. Intelligence concerning foreign diplomatic exchanges was received
from the Forschungsamt (subordinated directly to GOERING) through
Ic/Luftwesen/Abwehr, and was given a restricted distribution. It
consisted of intercepted Allied radio-telegrams (e.g. London-Stockholm),
ordinary radio reports (e.g. Atlantic Radio) and intercepted traffic
between diplomats and ministers on certain links, Ankara-Moscow (Turks),
Bern-Washington (Americans), London Washington (Poles).
36. The last-mentioned source was of great value before and during the
invasion and after the breaking-off of Turkish-German relations. In
general the Forschungsamt reports contained a great deal of significant
information concerning economic and political matters.

Reports from Repatriated Germans.
39. The Army, Navy, G.A.F. and Gestapo interrogated at will both
military and civilian repatriates. A general lack of direction and coordination resulted. Auswertestelle West, Oberursel, was responsible for
the G.A.F. interrogations and obtained many interesting details on enemy
morale and supply.

FREMDE LUFTWAFFE OST (FOREIGN AIR FORCES EAST).
40. This section, the eastern front counterpart of Fremde Luftwaffe
West, covered the Soviet Union, China, Sweden, Finland and the Balkans.
It was organised into the following subsections:-
i) Aufmarsch.
In this section the Russian Order of Battle was worked out in
the greatest detail. Since the bulk of the Soviet Air
Forces was employed tactically in support of the Armies at the
front, this work was of the utmost scope and importance.
Appreciations of the air situation were issued whenever
necessary, on average every three to five days. Maps showing
the locations of Soviet flying units were issued on the 1st
and 15th of each month.
ii) Training and Organisation.
This section covered Soviet subordinations and chains of
command, the organisation of Soviet flying schools and the
training of pilots.
iii) Archives.
This section was responsible for provision of target data. It
covered Soviet Industry, power plants, oil installations, ball
bearing factories, etc. It issued industrial reports, based
mainly on P/W statements and W/T intercept material supplied
by the Forschungsamt.
iv) Auswertestelle Ost (Evaluation Centre East).
This organisation differed from Auswertestelle West in that it
dealt only with the most important and knowledgeable
prisoners, as for instance the Russian Inspector of Fighters
who landed with his staff by mistake on a German airfield in
1943. Thirty to forty P/W at the most were at Auswertestelle
Ost at any one time. The remainder were dealt with by the
interrogation centres of the individual Luftflotten, which
reported anything of interest daily. Since the Listening
Service provided the complete Soviet Order of Battle, and
knowledge of Soviet tactics was deemed unimportant, P/W were
only kept for what information they might provide concerning
Soviet organisation.
Auswertestelle Ost was located near Karlsbad and was under the
command of Oberstleutnant MOLTERS.

MELDEWESEN.
41. As the receiving and distributing centre for all data concerning
German and Allied operations, Meldewesen constituted an information
bureau highly appreciated by its users, i.e. O.K.W., O.K.L., GOERING,
Operational sub-areas, etc. The limited communications and staff of Ic
were however, insufficient to cope with the stream of enquiries from
HITLER, GOERING, Chief of General Staff and the rest, so that the flying
units were perforce neglected and the very success of this section
tended to have a detrimental effect on the work of Ic as a whole.

LUFTWESEN.
42. This department was an unhappy attempt to co-ordinate a number of
widely differing functions. It comprised the following sub-sections,
some of which have been already referred to:-
L/Abwehr, which was responsible for the maintenance of security
within the G.A.F. and for the security training of the flying units. For
the first task it did not dispose of sufficient personnel, and as
already indicated, Fremde Luftwaffen West and Ost were the only
departments competent to carry out the second. However, from the middle of 1944 an Oberleutnant ROLFES was appointed liaison officer with German P/W camps with the object of exploiting the intelligence possibilities of this source.
L/Pol. Maintained Ic liaison with the Foreign Office. His main
effort was to produce his "Aussenpolitischen Wochenbericht", a weekly
report on the political situation, reflecting Foreign Office views and
mainly emphasising the reasons for an Anglo-American-Soviet Russian
conflict of views.
L/Informationsdienst sorted and distributed radio reports sent in
by O.K.W./Chi.
L/Presse received reports from the Army, Field Propaganda companies
etc. as well as foreign publications.
Liaison with the S.D. was provided by Major MERKWITZ and Hauptmann
BULA.

Attaché Gruppe. Owing to the total lack of accommodation in Berlin,
the close direction of Attachés by Luftwesen was made impossible and
their control virtually ineffective.

INDEPENDENT SPECIALISTS.
43. Ic Wirtschaft. In this section Oberstleutnant SEIDL, with the
assistance of one officer, issued a monthly report on Anglo-American
bombing attacks, comprising details of damage, falling-off of production
etc. and predicting probable future Allied tactics.
Ic/See. This department covered purely Naval matters.
Ic/Bild. Theoretically for the purpose of Ic-liaison with the Main
Photographic Section, this department was rendered superfluous owing to
the practice of subordinate units by-passing Ic and dealing direct with
the Hauptbildabteilung.

PUBLICLTIONS ISSUED BY Ic.
44. The succeeding paragraphs in this report are in the form of a
catalogue of publications issued by Chef Ic. Hauptmann ZETZSCHE's
assessment of the scale of contribution to the subject matter of these
reports by the various sources of intelligence already mentioned will be
found in Appendix I to this report. A diagram prepared by Hauptmann
ZETZSCHE summarising the sources which went to make up Ic's publications
appears in Appendix II.
(a) Maps showing Order of Battle.
Maps of the Western Front (Great Britain and France), Southern
Front (Italy), Mediterranean area and the world as a whole were issued
monthly down to Divisional level and to O.K.W., O.K.L., O.K.H. and
O.K.M. Printing difficulties were responsible for this limiting of
distribution.
(b) Rechenzettel (Allied Strength Estimate).
Issued monthly down to Divisional level and to the Flugmeldedienst.
(c) Truppenfeststellungen.
Covered unit transfers, rearmament and changes of subordination and
command, quoting the source of each item, e.g. Presse, Grönbild
(covername for Listening Service). (Issued every two to three days to
Luftflotte Ic's and the Flugmeldedienst).
(d) Appreciations of the Air Situation.
Teleprinted at three to five-daily intervals to specialist
departments of O.K.W, O.K.H., O.K.M., Luftflotte Ic's and Air
Observation Units, these appreciations covered tactics employed against
special targets, new operational procedures, estimates of Allied
production and losses, ferrying figures, invasion potentialities.
(e) Red Books.
Issued by Gruppe B of Fremde Luftwaffen West, the so-called Red
Books contained data concerning Allied targets and airfields and those
of neutral countries.
(f) Target Data and Photographs.
Also issued by Gruppe B.
(g) Notes on Allied Air Armament.
Figures of Allied production and losses, derived mainly from press
and radio reports were prepared for O.K.L. headquarters units. German
and agent reports of aircraft shot down were disregarded owing to
unreliability. These figures, as well as Ic predictions, proved more
accurate than those issued by TLR/Rü.
(h) Reports on Allied Morale.
Contained notes on morale, supplies, political questions, economy,
etc. derived from P/W statements and extracts from captured letters.
(i) Foreign Comment on the Air War.
Press and radio opinion concerning the German and Allied air
forces, presented in tendencious form to illustrate various themes, such
as, for instance, that the G.A.F. was handmaiden of the German Army.
(j) Ic Kurzmeldungen.
Immediate reports on new aircraft types, new operational
procedures, new commanders and their characteristics, new weapons and
apparatus, etc. Distribution was extremely varied to include all
possible interest parties. Up to the middle of 1944 advance warnings of
Allied attacks, derived from P/W interrogations, captured maps and
target data, were also promulgated in this form. After that date, to
avoid unnecessary delay, they were issued independently at source by

Auswertestelle West.
(k) Stichworte zum Feindeinsatz (Notes on Enemy Operations).
Contained extracts from P/W interrogation reports of special
interest, evaluations of captured documents, press and radio reports
etc. Cartoons from the foreign press added immensely to its popularity.
It was issued every three to five days and distributed to some 60
departments (O.K.L., Commands, Flugmeldedienst Units, Research,
Industry, etc.).
(l) P/W Interrogation Reports.
Demand for these was great largely owing to the political
observations they contained, and until about August 1944 they were
allowed a wide distribution. After this data the original reports were
limited to Commands sod Air Observation Units, the remainder receiving
"Stichworte sum Feindeinsatz" instead.
(m) Blue Books.
Instituted by KIENITZ at the end of 1943, the Blue Books dealt with
subjects of a confidential nature, e.g. American day operations, A1lied
ground support, British navigation, etc. However, in spite of a wealth
of illustration and good printing they proved a failure, being too bulky
to be easily read, apart from the contention in certain high quarters
that they only amounted to Allied propaganda.
(n) Einzelnachrichten des Ic Dienstes (Special Ic Studies).
The first of this series was brought out in the middle of 1943,
nothing of the kind having been attempted before. At first they appeared
weekly on such subjects as "American day and British night operations",
"Experiences of Fliegerkorps IX in the bombing of London", etc. With the
dropping of the Blue Book series round about June 1944, E-N began to
include such restricted subjects as "Allied twin-engined operations',
"American fighter navigation", etc. Difficulties were encountered in its
distribution, which were countered by the printing of 3,000 copies. It
was highly valued by such as managed to get hold of it, and was in
constant demand by the Wehrmacht, industry and research.
(o) Schnellbildsendungen (Rapid Photo Delivery).
This was a system, inaugurated by Ic/See, of delivering negatives to
Commands in order that the latter might run off as many prints as were
required by subordinate units. The system was originally utilised by
Ic/See for distributing Ship types, but Ic applied the idea generally to
the swift distribution of new aircraft types, captured H2X negatives,
and apparatus, aerial photographs of airfields, etc.
The system did not work effectively; for instance, it took longer to
procure both positives and negatives from the Main Photographic Section
than to obtain the required number of prints. Moreover, the shortage of
photographic material at Commands made it difficult for them to do the
necessary printing from the negatives which they received. Finally, the
previous system of delivering normal prints had to be reverted to.

A.D.I.(K) and Walter A. Frank
U.S. Air Interrogation. for:- S.D. Felkin
2nd October 1945 Group Captain.
SECRET. APPENDIX I.
AN ASSESSEMENT BY HAUPTMANN ZETSCHE
OF THE RELATIVE CONTRIBUTIONS OF IC SOURCES
TOWARDS FINAL APPRECIATIONS BY CHEF IC.
A. ORDER OF BATTLE.
W/T Listening Service……………………………………… 70%
P/W Statements )
Captured Material )…………………………………………… 20%
Press ……………………………………………………………………………… 1%
Air Photos ………………………………………………………………… 9%
B. SUBORDINATIONS AND CHAINS OF COMMAND.
W/T Listening Service……………………………………… 50%
P/W Statements )
Captured Material )………………………………………… 5%
Press ……………………………………………………………………………… 45%
C. PERSONALITIES.
Press ……………………………………………………………………………… 90%
P/W Statements )
Captured Material )…………………………………………… 10%
D. OPS. APPRECIATIONS.
P/W Statements ……………………………………………………… 55%
Captured Material ……………………………………………… 20%
W/T Listening Service …………………………………… 20%
Press ……………………………………………………………………………… 5%
E. TECHNICAL APPRECIATIONS.
P/W Statements ……………………………………………………… 30%
Captured Equipment …………………………………………… 50%
Press ……………………………………………………………………………… 20%
F. ESTIMATES OF ENEMY PRODUCTION.
Ferrying and O.B. Data (Mainly W/T
Listening Service) …………………………………………… 35%
Enemy Losses …………………………………………………………… 30%
Radio and Press …………………………………………………… 30%
P/W Statements ……………………………………………………… 4%
Agents' Reports …………………………………………………… 1%
G. ESTIMATES OF ENEMY LOSSES.
P/W Statements ……………………………………………………… 20%
Press and Radio …………………………………………………… 40%
W/T Listening Service ………………………………… 30%
Neutral Reports …………………………………………………… 9%
Agents' Reports …………………………………………………… 1%"

[Bruce Dennis]

"A. D. I. (K) Report No. 365/1945
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 – V.

I.F.F.
1. This report is the fifth of the series dealing with radio
and radar equipment in the Luftwaffe. As in the case of the
previous four reports (A.D.I.(K) 343, 357, 362 and 363/1945), it
is based on interrogation of General Nachrichtenführer MARTINI,
Director General of G.A.F. 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.
2. For convenience in reading, the report is divided into
three main sections covering the following applications of
I.F.F.
A - Flak.
B - Early Warning Radar.
C - Air-to-Air Recognition.

GERMAN VIEWS ON THE IMPORTANCE OF I.F.F.
3. Before the outbreak of war the practical application of
radar was mainly concentrated upon its use as an aid to Flak,
and the Germans did not realise the importance of an early
warning service until after hostilities had begun. In
consequence the need for the identification of friendly aircraft
picked up by radar sets arose initially mainly in conjunction
with Flak requirements.
4. Owing possibly to the fact that the first solution to the
Flak problem was not as successful as that achieved in
connection with early-warning radar, while at the time great
importance was attached to Flak as a defensive weapon, much
effort was devoted in the first few years to producing a
suitable identification system for that arm.
5. By 1944, the American bomber force was able to bomb Berlin
by daylight in clear weather with insignificant losses by Flak,
despite the application of various radar and optical aids. As a
result, Flak had fallen into disrepute as to defensive weapon.
6. This opinion of the ineffectiveness of Flak was very
pronounced among the members of the Signals Staff of the G.A.F.
and it is hoped to give their reasons for this view in a later
report in this series on Ground Radar. Flak was regarded by them
as an out of date weapon and for this reason as well as on
account of the inherent difficulties of the problem, practically
no effort was made to provide a means of identification of
friendly aircraft for Flak purposes during the later stages of
the war.
7. On the other hand the position of early warning radar was
exactly the reverse and as early warning became vital so the
G.A.F. attached ever greater importance to I.F.F. for early
Warning radars, particularly in connection with bad weather and
night raids involving feints and spoof sorties. It was
considered essential to obtain a clear picture of the tracks of
Allied raiding aircraft and to avoid any confusion with German
fighter aircraft which also flew in group. The latest endeavour
in this field went so far as to provide separate identification
for different G.A.F. night fighter units in order to assist
ground control still further.
8. Increasing attention was also being paid to air-to-air
recognition between German aircraft but this, though considered
desirable, was not thought to be nearly so important as the
essential requirement that friendly aircraft should be
recognisable to the early warning service In order that a true
picture of the progress of Allied bomber attacks could be
obtained and fighter aircraft vectored to the attack by ground
control.

A – I.F.F. FOR FLAK
9. At the beginning of 1939 it was intended to equip all
Flak sites with a radar fire control apparatus then being
developed by the firm of Lorenz. The Lorenz apparatus proved
unsatisfactory and in the course of 1939 the Würzburg, produced
by Telefunken, was adopted for Flak fire control.
10. The need for the recognition of friendly aircraft for Flak
purposes had been apparent to the Germans and an I.F.F. set for
use with the Würzburg was produced, and was available at the
outbreak of war. It was known as the Zwilling and was given the
designation FuGe 25.
11. The 50 cm. Würzburg transmission received by the FuGe 25
caused the FuGe 25 transmitter to broadcast an audible morse
signal on the same frequency, which could then be heard by the
Würzburg operator in his headphones. As this was not a retransmission
of the Würzburg radar pulses, it gave no indication
of range and might equally well have originated from an aircraft
in the vicinity beamed by some other Würzburg. General MARTINI
was fully aware at this stage that the FuGe 25 was no real
solution to the identification problem.
12. Meanwhile, the firm of Gema had produced the Freya for
the Navy, and in October 1939 eight of these had been taken over
by the G.A.F. and were stationed on the East end North Frisian
Islands, where they proved their value la combatting early
British bombing attacks directed against the North Sea ports.
13. In November 1939 Gema demonstrated an I.F.F. set for use
with Freya which proved to be forerunner of the FuGe 25A
Erstling. General MARTINI recognised immediately that this Freya
I.F.F. which operated on the principle of returning the Freya
pulses and which provided range measurement, was a far superior
solution and he endeavoured to use his authority to have the new
principle universally adopted for Flak.
14. At that time many different departments were involved and
partly on this account and partly because FuGe 25 Zwilling was
sponsored by the Technisches Amt, MARTINI failed to gain his
point. (see also A.D.I.(K) 334/1945),paras. 95-96). It was only
with great difficulty that he was able to persuade the R.L.M. in
early 1940 that an order for 3,000 FuGe 25A for Freyas should
be placed and even then considerable delay occurred before they
were supplied.
15. During 1940 and 1941 the shortcomings of the Zwilling
gradually became apparent, particularly in connection with night
fighter operations, but by the time the advantages of the
FuGe 25A Erstling had been recognised and the set had been
finally adopted, over 10,000 Zwilling sets had already been
manufactured.
16. The original Freya used a wavelength of 2.40 metres to
which the FuGe 25A Erstling responded on 1.90 metres. To permit
of the universal application of the FuGe 25A a small transmitter
called the Kuh had to be built into other types of early warning
radar in order to interrogate the airborne set. The response was
picked up by the Gemse receiver unit. In this manner a simple
pair of wavelengths were, in effect, set aside for aircraft
I.F.F. purposes.
17. In spite of these achievements the Flak problem had not
been completely solved, as it was not possible to produce a
sufficiently beamed transmission on 2.40 metres to be certain
that a response seen on the recognition tube was that of the
aircraft in the Würzburg beam. Various expedients were tried out
but as mentioned above, the problem still remained unsolved up
to the end of the war and was finally abandoned.

FUGE 25 - ZWILLING.
18. The FuGe 25 Zwilling (= twin) received the Würzburg pulses
on a 50 cm. carrier wave and re-transmitted a morse recognition
signal on the same frequency, but as it did not re-transmit the
pulses received, no range could be obtained by the ground set.
The shortcomings of this system were recognised in 1941 end a
series of attempts was made to overcome them by using responder
technique as detailed below.

HÄUPTLING.
19. In order that the Flak Würzburgs should get a range with
their recognition signal, the FuGe 25 Zwilling was converted so
that the pulses received on 50 cm. were re-transmitted on the
FuGe 25a wavelength of 1.90 m. This conversion was complete by
the autumn of 1942. The new set was called Häuptling. About this
time, however, Allied jamming of Würzburgs commenced and the
Germans were forced to produce Würzburgs on various wavelengths
known as Insel A 53.0-54.2 cm. and Insel B 56.7-58.0 cm. As a
result, the FuGe 25 no longer responded to all Würzburgs and so
the Häuptling did not fulfil its task.

KUCKUCK.
20. When Würzburgs on various frequencies were introduced, the
basic FuGe 25 set was finally given up and the FuGe 25A Erstling
became the standard airborne set.
21. All Würzburg radars were provided with a Kuh type
transmitter on 2.40 m. called the Kuckuck, the aerials for which
were placed in the Würzburg paraboloid. The resultant polar
diagram was extremely wide-angled as compared with the Würzburg
beam and a response at the same range as that of the aircraft
held in the beam was not positive proof of identity if many
aircraft were about.
22. In addition the 2.40 metre transmission spilled over and
could be picked up at distances of as much as 10/15 km. behind
the Würzburg set, so that even aircraft behind the Würzburg were
triggered off. As Flak was only interested in aircraft within
firing range of the Würzburg, this procedure was at its weakest
with the very type of recognition for which it had been
expressly designed, and in consequence Kuckuck was finally
condemned as a failure in 1943.

WOBBELBIENE.
23. With the failure of Kuckuck the Germans decided that the
only solution to the Flak problem was to apply British I.F.F.
technic. The FuGe 225, known as Wobbelbiene, which was designed
to sweep through (Wobbeln) the 50 cm. to 60 cm. band and act as
responder (Biene), was developed for this purpose and was to
have been introduced in the winter of 1943/1944. This, however,
still did not cover the new Würzburg Insel C of 62.3 - 63.8 cm.,
which was being introduced in 1944.
24. Further modifications to Wobbelbiene were considered in
order to cover this waveband but many difficulties, both
mechanical and electrical, had been encountered with the design
despite the fact that the set was said to be a direct copy of
British R.F.3090.
25. The project was ultimately given up before being used
operationally and up to the end of the war no satisfactory
solution to the Flak problem had been found.

B - I.F.F. FOR EARLY-WARNING RADAR.
26. The Kuh and Gemse arrangement in conjunction with the
FuGe 25A whereby two wavelengths, 2.40 m. for interrogation and
1.90 for response, had been set aside for I.F.F., worked
satisfactorily for early-warning radars. MARTINI's staff
considered that this system was superior to the then current
British principle of an I.F.F. set sweeping through the various
early-warning wave bands and responding only intermittently to a
particular frequency.
27. When Allied jamming became serious, it was fully realised
that the use of one special wavelength for recognition purposes,
rendered recognition very vulnerable to Allied countermeasures
although it was considered difficult from a technical point of
view to carry out effective jamming.
28. To anticipate this eventuality, a tactical requirement was
formulated in 1943/1944 calling for a FuGe 25A working on a new
frequency and the Erstling-Grün was designed and manufactured,
but never put into use as the Allies did not employ the expected
counter-measures.
29. With the advent, during the course of 1944, of automatic
sweeping ground radar with a P.P.I. presentation like
Jagdschloss, a new problem for I.F.F. arose. So long as the
recognition signal emitted by the aircraft in responding was a
morse letter there was no guarantee that it would come up
effectively as the beam swept over the target aircraft.
30. The Germans' first solution of this problem, was the
Erstling-Rot, a form of FuGe 25A, which responded with the morse
identifications separated by a six-second dash, thereby ensuring
that response was sufficiently continuous for the ground set to
sweep the aircraft at least once whilst the airborne set was
transmitting the long dash.
31. In 1944 Allied radio countermeasures became more intense
and it was realised by the Germans that the general principle
applied in all their anti-jamming countermeasures must also hold
for I.F.F. This principle was to have a number of alternative
frequencies available for every type of set and a new tactical
requirement embodying this facility was, therefore, formulated.
32. It was decided that the new I.F.F. set must also give
continuous presentation of the recognition response so that
ground controllers could immediately identify friendly aircraft.
At the same time this would solve the identification problem for
panoramic ground equipment of the Jagdschloss type.
33. This requirement led to the development of the Neuling
which, however, had not been used operationally up to the end of
the war. It appears to have been a set with a number of novel
features which are discussed below at some length.
34. In complete contradiction of the principles used in all
earlier sets, the problem of I.F.F. for centimetre radar was to
be solved by using the searching beam to trigger off the I.F.F.
set. A small unit called the Frischling was to convert the
centimetre wavelength to a frequency which would be accepted by
the standard Erstling receiver.

FuGe 25A – ERSTLING.
35. The FuGe 25A is the well known set which has been installed
in every German aircraft since about the beginning of 1942 and
which had also been used for Egon control(see A.D.I.(K)
357/1945). It was often referred to as the Erstling.
36. It was a responding transmitter receiving on 2.40 m.(the
original Freya frequency) and re-transmitting the pulses
received on 1.90 metre. A morse signal repeated roughly every
two seconds was superimposed on the re-transmission, six
alternative codes being available. It was claimed that an
advantage of using a morse letter as recognition was that it
could easily be read by ear through the operator's headphones
and that this was easier than following the recognition C.R.
tube by eye.

ERSTLING-ROT.
37. In the early part of 1945 the G.A.F. began to introduce a
form of FuGe 25A known as the Erstling-Rot. It was designed to
deal with recognition difficulties occurring with ground radar
of the automatic sweeping type such as Jagdschloss.
38. The Erstling-Rot separated the morse signals by a dash of
six seconds duration - a period sufficient to ensure that the
ground radar swept the target. It embodied an improvement in
that it permitted of 18 different morse recognition signals
being superimposed on the re-transmission instead of only six as
in the case of the original Erstling.
39. Originally it was to have a more powerful transmitter but
this requirement was allowed to lapse when it was realised that
the factors limiting range were the sensitivity of the FuGe 25A
receiver or the power of the ground interrogator. A project for
a more powerful ground interrogator called the Gross Kuh was
considered, but as the ranges obtained with the normal Kuh were
thought to be adequate this idea was abandoned.

ERSTLING GRÜN
40. The G.A.F. signals staff realised that the use of a single
frequency for recognition purposes exposed them to the danger of
Allied R.C.M. In view of this a version of the FuGe 25A
operating on a new frequency was produced which was known as the
Erstling-Grün. The wavelengths used were to be 2.52 metres for
interrogation and about 2.00 metres for the response.
41. The small shift in wavelength was dictated by the need to
avoid new ground equipment. With the relatively small frequency
change the Kuh and Gemse were capable of being adjusted to the
new frequencies by the field "S. und I" (maintenance and repair)
teams, and so an economy was effected.
42. Erstling-Grün was never used operationally as Allied
jamming of the original Erstling frequency was never
experienced.

NEULING.
43. The FuGe 226, usually referred to as the Neuling, was to
have been available for installation in operational aircraft by
December 1944, but owing to difficulties encountered during the
trials carried out at Rechlin it was not yet ready at the time
of the capitulation. Lorenz were responsible for its production
and Dr. KRAMAR of that firm was considered the expert on its
technical aspects.
44. The Neuling, which was considered to be a good solution to
the identification problem, was designed to overcome previous
difficulties and to provide new facilities. The tactical
requirement originally called for were:-
(a) Continuous presentation of I.F.F. signals on all types
of early-warning radar including panoramic radars
such as Jagdschloss.
(b) Twelve alternative pairs of frequencies for I.F.F.
(later reduced to six pairs) - each pair to consist
of an interrogating and response frequency.
(c) Air to air recognition between German aircraft.
45. This ambitious programme was not fulfilled when the
FuGe 226 was tried out in the later part of 1944 at Rechlin, but
the experts who carried out the trials believed that the main
requirements could be met by sacrificing half the pairs of
frequencies, thereby limiting the set to six frequency pairs.
46. To meet requirement (a) and provide continuous presentation
of the recognition signal on the ground radar, and at the same
time permit the simultaneous use of a number of different
frequencies, the responder and transmitter were to sweep very
rapidly through the selected band which was believed to be 125 -
167 mc/s.
47. The receiver and transmitter sweeps were synchronised a few
megacycles apart, so that the response was always on a slightly
different frequency to that of the interrogation. This sweep was
to be carried out sufficiently rapidly for the blip on the
recognition tube of a ground set interrogating on one of the
frequencies to appear continuous to the eye of the operator.
48. Presumably, even allowing for after-glow effects, the
frequency of sweep must have been extremely high. It was not
known exactly what repetition rate was used, nor what technical
method was employed to obtain such a high rate of sweep through
the band.
49. Great importance was attached to requirement (a) as it
allowed ground controllers to obtain continuous recognition on
Jagdschloss type P.P.I. tubes and so distinguish between
friendlies and hostiles. It also greatly assisted the control of
friendly fighters by Freya stations.
50. The requirement (a) for continuous presentation of the
recognition signal appeared to have precedence over the
requirement (b) for twelve alternative pairs of frequencies
since in order to meet (a) Rechlin decided that the number of
channels available would have to be cut from twelve to six
pairs. It was found by Rechlin that squeezing twelve separate
frequencies for response (which could not overlap with
interrogation frequencies) into the swept band caused the band
width of the individual responder frequencies to be so narrow
that the recognition blip became too thin and indistinct on the
ground radar recognition tube.
51. It was hoped that requirement (b) - the provision of
alternative frequencies - would prove a safeguard against
possible Allied R.C.M. It was also believed that it would aid in
mitigating clutter on the recognition tubes of Freya etc., since
interrogation would be spread over a number of frequencies.
Wandering blips resulting from neighbouring ground radars which
triggered off other aircraft obscured the tube and caused this
clutter.
52. Efforts had also been made to overcome this trouble by
building an arrangement into ground radars which prevented
interrogation being carried out continuously as was often the
undesirable habit of operators. By means of this arrangement
power was cut off from the Kuh aerials about a minute after the
interrogation switch had been depressed and this device also
prevented interrogation until a further short period had
elapsed.
53. Requirement (c) was only third in importance. The air to
air I.P.F. facility, however, entailed a disadvantage which was
regarded as a serious one, namely that when being used for that
purpose the Neuling was no longer capable of responding to
interrogating by other radar apparatus on the ground.
54. The tactical application of the Neuling must be considered
in relation to the defence problems which the Allied bomber
forces set Germany in 1944. The Germans regarded it as essential
for the defence and more particularly for night defence that
they should be able to obtain an absolutely clear picture of the
air situation and identify Allied bomber streams unequivocally
and at a glance. The P.P.I. presentation of ground radar like
Jagdschloss and Forsthaus was beginning to be appreciated and
attempts were being made to control directly from these
panoramic displays.
55. It will be remembered too that German night fighter Gruppen
operating under the Verbandsflug system flew together in loose
groups or patrolled in the area of a selected beacon. It was,
therefor, considered essential that these aircraft should be
immediately identified as friendly on the P.P.I. tube and not
confused with a bomber stream. It was also held to be of great
value to ground controllers to have a means available for
identifying one Gruppe from another with equal immediacy.
56. To attain these requirement one of the six interrogating
frequencies available was allotted to early-warning radar and
the remaining five were to be given to different night fighter
Gruppen or Geschwader. The Neuling in each aircraft was then so
switched that it could receive and respond to two of the six
Neuling frequency pairs, viz. the early-warning frequency and
the frequency allotted to the Gruppe to which the aircraft
belonged.
57. For Jagdschloss panoramic ground equipment a complete
continuous identification picture divided into friendlies and
hostiles could be obtained by interrogating on the earlywarning
frequency.
58. By simply training a knob the transmitter and receiver
could be switched to the frequency pair of a particular
operational Gruppe and this presented no technical difficulty
with Breitband aerials. Aircraft of that Gruppe could then be
identified immediately in the over-all picture on the P.P.I.
tube. This facility was considered a great advance both from
the point of view of I.F.F. and of ease of ground control of
night fighters.
59. P/W who claimed to have seen a ground P.P.I. display
during the Neuling trials stated that the recognition blip came
up on the tube as an extension of the reflected blip at
slightly greater range and that it subtended a greater angle in
the display. He described it as a "sausage rather longer than
the aircraft blip and sitting on it".
60. Reference has been found in a document to a Neuling
covering the band 1,000-1,500 mc/s. The P/W who was responsible
for the formulation of radar requirements stated that he had
never heard of a Neuling on this frequency, but suggested that
it might be for use in responding directly to the beam of 25
cm. ground radars such as Forsthaus F. This suggestion appears
unlikely, however, as it seems to involve a departure from the
Neuling principle.

FRISCHLING.
61. In view of the introduction of highly beamed 9 cm. ground
radar such as Forsthaus Z and Jagdschloss Z, it had been decided
to depart from the principle of using a separate interrogation
frequency and to employ the search beam to trigger off I.F.F.
For this purpose a special attachment to the airborne Erstling
called Frischling had been planned. This was a receiver on 9 cm.
which converted the frequency to that of the Erstling so that it
responded on 1.90 metres.
62. With the planned introduction of the Neuling, consideration
was given to a modification of the Neuling whereby a Frischling
attachment would be built in for the purpose of converting the
frequency and so trigger off the Neuling in the same manner. P/W
was not clear whether this would only apply to one frequency of
the Neuling, nor did he know what technical method would be used
to accomplish it.
63. Frischling was to be produced by Telefunken but was still
in course of development when the ear came to an end.

AIR-TO-AIR I.F.F.
64. For some reason as yet unexplained, the German interest in
air-to-air recognition only became great enough for suitable
equipment to be designed during the last stages of the war.
During the year preceding the termination of hostilities,
captured night fighter crews consistently maintained that
some improved form of I.F.F. which would allow recognition
of friendly aircraft was expected but no attempt appears to
have been made to adapt the FuGe 25A for this purpose.
65. The present P/W assert that so long as I.F.F. and airto-
air search operated on metric wavelengths and could not
be sharply beamed, the problem of air-to-air recognition
could only be half solved, as a range identification only
was obtained. It was realised that with a dense bomber
stream there would be so many aircraft comparatively near
to the fighter that recognition by range only was not very
valuable. Nevertheless the Neuling FuGe 226, which was
shortly to be introduced, was to have provided air-to-air
I.F.F. facilities.
66. In the beginning of 1945 the Germans tackled this
problem for centimetric search gear and proposed to depart
from their original principle of separating search and I.F.F.
interrogation. The search beam of centimetre equipment was to
be received by the Frischling attachment to the airborne
I.F.F. set and the centimetre frequency so converted that the
I.F.F. net was triggered off.

NEULING.
67. In the Neuling, which has been described above in
detail, it was planned to provide air-to-air I.F.F.
facilities by the use of a special switch which, when
depressed, reversed the roles of the receiver and responding
transmitter. The interrogating aircraft could then trigger
off the I.F.F. set of neighbouring aircraft and receive its
response on the receiver portion of the Neuling.
68. The response was to be fed through to the SN 2 or other
set in use and the presentation of this recognition signal
was to take the same form as in the Freya, i.e. a second
time base carrying the I.F.F. signal was to appear to one
side of the main time base.
69. During this operation no I.F.F. response could be made
to interrogating ground stations, and this caused some
apprehension. To discourage excessive use of air-to-air
interrogation, the switch in the aircraft was to be awkwardly
placed and inconvenient to operate – a typically German solution
to a problem of aircrew training.

FRISCHLING.
70. The night fighter search apparatus – the Berlin N.1.A.
and the Bremen 0 on 9 cm, and later probably the München on
3 cm were to go into service some time in 1945 as will be
discussed in a future report in this series.
71. To provide air-to-air I.F.F. facilities the
Frischling, mentioned in paras. 61-63 above, was to be
attached to the FuGe 25A and later built into the Neuling
as a modification. It was to convert the centimetric beam
transmission of air-to-air search apparatus to the
frequency of the Erstling FuGe 25A so that the latter was
triggered off directly by the searching beam.

FALTER WITH GÄNSEBRUST.
72. As early as 1940, experiments had been made with infrared
homing on to aircraft exhausts using an infra-red
telescope of the Bildwandler type called Spanner. This met
with only limited success on account of restricted range and
the dependency of infrared on clear weather conditions but the
idea was never completely dropped.
73. With the introduction of night fighter commentary and the
Verbandsflug tactics in 1944, it was required that night fighter
units should fly in groups and keep as close together as
possible.
74. It was, therefore, proposed to introduce an aid in the
shape of some form of infra-red navigation lights to be viewed
through an infra-red telescope. The latter, which was a form of
Spanner, was named Falter. As, however, the field of view of
this telescope was confined to about 15° it soon transpired
during trials at Werneuchen that it was not a practical
proposition.
75. In 1944 the idea of using infra-red for recognition
which had long lain dormant was once more evoked by the
discovery that British bombers were carrying en infra-red
recognition light. It was, therefore, proposed that German
night fighters should home on to the infra-red lights by means
of the Falter.
76. For mutual recognition between night fighters an infrared
lamp termed "Gänsebrust" was also planned. It was hoped that
Gänsebrust might not only allow recognition between German
aircraft but possibly afford some protection from British night
fighters which might become uncertain in their recognition of a
German night fighter if the Gänsebrust was flashed intermittently
even though the British code in use for the night were
not known.
A.D.I.(K)and S.D. Felkin
U.S. Air Interrogation. Group Captain
2nd August 1945"

[Allan125]

Thanks Bruce, these continue to be fascinating reading, nice to see the other side of the hill, so to speak. Getting Court Martial proceedings against you in absentia, not good, hope nothing happened to the relevant families.

cheers

Allan