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Interrogation of Baron Von Schalcky CIOS File 24-15

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

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
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
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
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

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
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
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