ARTILLERY COLLECTION: THE USE OF ANTIRADAR MORTAR SHELLS TO CREATE PASSIVE JAMMING OF ENEMY FIELD ARTILLERY RADAR SETS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A029500460001-4
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 26
• Document Creation Date: December 22, 2016
• Document Release Date: January 13, 2012
• Sequence Number: 1
• Publication Date: May 14, 1962
• Content Type: MEMO

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CENTRAL INTELLIGENCE AGENCY
WASHINGTON 25. D. C.
1 4 MAY i)oL
-MEMORANDUM FOR: The Director of Central Intelligence
SUBJECT : ARTILLERY COLLECTION: "The Use of Antiradar
Mortar Shells to Create Passive Jamming of
Enemy Field Artillery Radar Sets"
1. Enclosed is a verbatim translation of an article which
appeared in a Soviet Ministry of Defense TOP SECRET publication
called Information Collection of the Artille (Informatsionnyy
$bornik Artillerii).
2. In the interests of protecting our source, this material
should be handled on a need-to-know basis within your office.
Requests for extra copies of this report or for utilization of
any part'of this document in any other form should be addressed
to the originating office.
4
Richard Helms
Deputy Director (Plans)
0 SE RET
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Original: The Director of Central Intelligence
cc: The Director of Intelligence and Research,
Department of State
The Director, Defense Intelligence Agency
The Director for Intelligence,
The Joint Staff
The Assistant Chief of Staff for Intelligence,
Department of the Army
The Director of Naval Intelligence
Department of the Navy
The Assistant Chief of Staff, Intelligence
U. S. Air Force
The Director, National Security Agency
Director, Division of Intelligence
Atomic Energy Commission
Chairman, Guided Missiles and Astronautics
Intelligence Committee
The Deputy Director of Central Intelligence
Deputy Director for Intelligence
Assistant Director for National Estimates
Assistant Director for Current Intelligence
Assistant Director for Research and Reports
Assistant Director for Scientific Intelligence
Director, National Photographic Interpretation Center
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COUNTRY : USSR
SUBJECT : ARTILLERY COLLECTION: "The Use of Antiradar
Mortar Shells to Create Passive Jamming
of Enemy Field Artillery Radar Sets"
DATE OF INFO : 1958
APPRAISAL OF
CONTENT : Documentary
SOURCE : A reliable source (B)
Following is a verbatim translation of an article entitled
"The Use of Antiradar Mortar Shells to Create Passive Jamming
of Enemy Field Artillery Radar Sets" which appeared in Issue
No. 46, 1958 of the Soviet military publication Information
Collection of the Artillery (Informatsionnyy Sbornik Artillerii).
This publication is classified SE-TOP ET by the Soviets and
originates with the Artillery Headquarters of the Ministry of
Defense. According to its preface, it is designed for generals
and officers from commander of artillery of a corps, commanding
officer of an artillery division (commanding officer of an
engineer brigade), and higher.
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The Use of Antiradar Mortar Shells to create Passive
Jamming of Enemy Field Artillery Radar Sets
Radio electronic equipment considerably increases the capabilities
of modern weapons. The rapid introduction into the armed forces of radar,
radio communications, radio remote control, radio navigation, and military
television is having a considerable influence on the methods of con-
ducting troop combat operations. At the present time, Without the use of
radio electronic equipment, effective combat operations by aviation,
the navy, artillery, especially antiaircraft and missile artillery, and
other arms of troops are impossible.
The success of a modern operation depends to a great extent on
how accurately and how reliably the complicated radio technical devices
for the control of weapons and combat equipment will function. Therefore,
to create difficulties for enemy reconnaissance and disorganize the con-
trol of his troops, combating enemy radio electronic equipment assumes
particular importance. This includes a number of measures collectively
known as "radio countermeasures". By radio countermeasures is meant
the conducting of a wide range of measures directed toward the des-
truction (neutralization) or reduction of the effectiveness of enemy
use of radio technical equipment such as radar, radio communications,
radio remote control and radio navigation.
Among the measures included in radio countermeasures
(radioprotivodeystviye), or radio electronic countermeasures (radio
elektronnaya mere), as they are called in the Armed Forces of the U.S.A.,
are the destruction of radio technical equipment, the creation of radio
interference (radiopomekha), and antiradar camouflage of troops and in-,
stallations.
The destruction of radio technical equipment can be accomplished
by artillery fire, air strikes, and sabotage groups.
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SE ET
For the destruction of this equipment, depending on circum-
stances, the importance of the targets, and their distance from
the main line of resistance, tube, heavy rocket, and missile
artillery may be used.
Radio jamming (radiopomekha) of enemy radio technical sets may
be created by jamming transmitters (active interference) or special
antiradar reflectors (passive interference).
Antiradar camouflage is achieved with the aid of corner re-
flectors which create on the screens of radar sets blips of e+cn-
siderably greater intensity than the blips from real targets, and
this permits the alteration of the configuration of the radar pattern
of the ground in the area of the camouflaged installation and also
makes it possible to create false targets on the screens of radar sets
and to camouflage the real ones. Antiradar camouflage is employed
with the object of concealing from enemy radar intelligence the move-
ment oit location of troops and equipment (artillery, tanks, etc) vr
installations (airfields, railway junctions, bridges, crossings., etc).
In order that radio countermeasures would have maximum effec't
and would not interfere with the work of our own radio technical,*
equipment, the planning of radio countermeasures, as a rule, should be
done in a centralized manner at frcnt(army) level and carried out in
close coordination with the combat actions of all arms of troops
participating in the operation.
Some of the problems of reconnoitering enemy ground radar sets
and of combating them by artillery fire were dealt with in Artillery
Information Collection No. 43, which also gives a description of the
features of individual radar stations to which we shall be referring
in this article.
This article examines the problems of creating passive radio
jamming of enemy field artillery ground radar sets. The main object
of these sets is the reconnaissance of mortar (artillery) batteries
which are firing and the correction of artillery fire.
-3-
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The determination of the coordinates of firing positions with
the aid of radar sets (Sketch 1) is done, as is known, by means of
detecting and tracking the mortar shell (mina) during the ascending
sector of the trajectory of its flight with the subsequent extrapo-
lation of the sector located by intersection of the trajectory down
to ground level (the assumed location of the mortar that is firing).
In order to deny the enemy the possibility of radar detection
of the mortars which are firing, it is necessary to prevent or hamper
his detection and intersection of mortar shells during the ascending
sector of their trajectory. This task can be fulfilled by setting
up passive jamming through the use of antiradar reflectors (chaff or
fiberglass) in the zone being reconnoitered by these radar sets.
Chaff or fiberglass can reflect electromagnetic energy in the
same way as mortar shells.
The scattering of antiradar reflectors (dipoles) in the area
covered by enemy radar reconnaissance sets can be done through the
use of aircraft or of special mortar shells filled with these re-
flectors.
The creation of passive jamming of field artillery radar sets
by scattering antiradar reflectors from aircraft entails definite
difficulties in connection with the dependence of aircraft flights
on meteorological conditions, the difficulty of organizing co-
ordination between these aircraft and the mortar subunits, etc.
Therefore, it is most advantageous to create passive jamming
of field artillery radar sets with the aid of antiradar mortar shells.
The maximum reflection of electromagnetic energy from the
antiradar reflectors, and, consequently, the most effective inter-
ference, will be achieved when the signal strength (uroven signalo v)
reflected from the antiradar reflectors in the direction of the radar
is several times greater than the signal strength reflected from the
mortar shell in the same direction.
-4-
S RET
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4 SE&RET
This is achieved by using a large quantity of reflectors
scattered at one point in space. The length of the reflectors
(dipoles) must be equal to approximately half the wave length of
the enemy radar set which is sweeping and against which the inter-
ference is being created.
Under these conditions, the blips from antiradar reflectors
attain great intensity and considerable size. Consequently, the
observation of the mortar shell on the screens of the radar sets
becomes impossible, and the possibility of determining the loca-
tion of the mortar that is firing is excluded.
Let us examine this problem more closely.
Antiradar reflectors (dipoles) scattered by the mortar shell
fly in all directions forming the so-called cloud of reflectors.
Thus, for example, the cloud of reflectors at the burst of a 120mm
caliber antiradar mortar shell reaches the size of 30 meters in
depth and 3 to 6 meters in width. The cloud of reflectors gradually
expands because of the action of air currents, descending at the
rate of 1 to 2 meters a second and, at the same time, drifting in
the direction of the wind.
With a wind speed of 8 to 9 meters a second, the size of the
cloud of reflectors reaches the size of 900 meters in width,
500 meters in height, and 30 meters in depth, and 3 minutes later
the sizes increase accordingly to 1000, 1500 and 400m.
The quantity of reflectors that must be scattered for the
reliable concealment from radar reconnaissance of a mortar shell
trajectory is determined by the fact that in the elementary re-
flecting impulse volume (elementarnyy otrazhayushchiy impulsnyy
obyem) the intensity of the signals from the dipoles must be
greater than the intensity of the signals from the mortar shell
being concealed.
-5-
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The term elementary reflecting impulse volume means
the volume in space which is occupied by the impulse
radiated by the radar set, inside which impulse all tar-
gets reflect radio waves simultaneously and cannot be
observed separately by the radar (Sketch 2).
The quantity of reflectors (N) necessary to create an
interference signal, equal in intensity to the signal from
a mortar shell when the orientation of the reflectors coin-
cides with the polarization of the electromagnetic waves
radiated by the set, can be approximately calculated by the
formula:
CrM
dosr
(1)
OFp maximum effective reflecting surface of the
mortar shell (cm2);
C(osr mean effective reflecting surface of one
dipole reflector (cm2).
The effective reflecting surface of a mortar shell
(target) can be measured or calculated by the formula:
d,_X Sts
where
Sts the density of electromagnetic energy in-
cidence on the target;
Sg the density of electromagnetic energy from
the target at the receiver input (na vkhode
pr iyemnika ) .
The effective reflecting surface of the target (mortar
shell) depends on its size, shape, and direction from which the
target is scanned.
-6-
RET
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)E6RET
S
A diagram of the reflection from a mortar shell has a lobe
shape (lepestkovyy kharakter) with the maximum radiation being
created by its side surfaces. Consequently, the scanning of
the mortar shell from the direction of its side surface presents
the best conditice for its detection and for locating it by
intersection on its trajectory.
The mathematical calculation to determine the effective
reflecting surface of a mortar shell is extremely complicated,
and therefore it is usually determined by experimentation, by
comparing the magnitude of the signals reflected from the mortar
shell with signals from standard reflectors, the m#4Fiti4*.%oA whose
effective reflecting surface is known. For example, the effective
reflecting surface of standard metallized balloons (spar-etalon)
put in free flight nay be easily calculated and measured with a
sufficient degree of accuracy.
When tracking a mortar shell the radar receives a certain
averaged magnitude of the scattered electromagnetic field
(usrednennoye znacheniye rasseyannogo elektromagnitnogo polya).
When calculating the quantity of reflectors essential for
the reliable concealment of a mortar shell in its trajectory, it
is essential to give the maximum,and not the averogeyvalue to
the effective reflecting surface of the shells.
Sizes of maximum effective reflecting surfaces of mortar shells
of various calibers are shown in Table 11.
Table 1.1
Caliber of mortar
shell in mm
Msximum magnitude of the effective
reflecting surface in cm2
With a wave length
With a wave length
of3cm
ofl0cm
82
1100-1200
800-900
120
7000-8000
6000-6500
160
17,000-20,000
8000-10,ooo
7-
SE ET
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The effective reflecting surface of one dipole will be at
its maximum when its axis is oriented parallel with the vector
cf pclarization of the electromagnetic wave radiated by the
radar set. It can be calculated by the formula:
Ootrm - 0.86 2
Ootrm
(3)
maximum effe tive reflecting surface of the
dipole in cm ;
X - length of the working wave of the radar.
When the axis of the dipole does not coincide with the
polarization of the electromagnetic wave, the effective re-
flecting surface of the dipole decreases in relation to the
absolute size of the angle between its axis and the vector
of the field strength.
Thus, when the angle between the axis of the dipole and
the vector of the field strength is 900, the effective reflecting
surface of the dipole will be zero.
In determining the quantity of antiradar reflectors
necessary to create reliable interference, it is essential to
consider the average,and not the maximum,value of the effective
reflecting surface of the dipole, which for the case of uniform
and equal probability orientation of dipoles in space can be
calculated by the formula:
Cosr = 0.15;.2
During the burst of a mortar shell, it may happen that
part of the dipoles will be damaged or will stick together and
part of them will be outside the limits of the reflecting im-
pulse volume of the set.
Fr kPT
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In consideration of these factors, the quantity of reflectors
calculated by formula (1) must be increased by a certain co-
efficient K. Coefficient K is determined by the formula:
K = K1
K2 x K3
K1 - signifies the necessary amount by which the signal
strength from the dipoles must exceed the signal
strength from the mortar shell;
K2 -- signifies the degree of scattering of the dipoles;
K3 -- the degree of damage to the dipoles.
The value of coefficient K depends on the type of radar
set and whether it has equipment for defense against passive
interference.
To create reliable jamming of radar sets not fitted with
equipment for defense against passive interference, it is sufficient
to raise the level of interference signals to double the level of
the signals from the target (K1 = 2).
Coefficient K2 is assumed to be 0.3; and coefficient K3
is assumed to be 0.2. Under these conditions K = 33.4.
Taking coefficient K into consideration, formula (1)
will assume the form:
N = K
4Tosr
It has been established by experiment that to create
effective passive jamming of radar sets not fitted with
an attachment (pristavka) to select moving targets, it is
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sufficient to scatter on the trajectory one quarter of a
standard package of chaff (fiberglass).
When creating passive jamming of radar sets fitted
with attachments for defense against interference, the necessary
quantity of reflectors is increased in proportion to the weaken-
ing of the interference signal by the defensive equipment (apparatura
zashchity).
The nomenclature of chaff and fiberglass and also their
dimensions, quantity and weight are given in Table 12.
Table 12
Chaff strips
No.4 for cre-
ating jamming
of sets in
Fiberglass
l0cm band.
DOS-50 to DOS-15 to
create create jamm-
jamming ing of sets
of sets in in 3cm band
100m band
Length of chaff strip
(Fiberglass) in mm
50
50 15
Width of chaff strip
2
- -
in mm
Quantity in a package
20,000
50) 000 800"000
Weight of a package,
440
50 90
in grams
`# SE ET
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_ r SECRET
Concealment of a mortar shell trajectory from enemy radar
reconnaissance will be most effective when the operator of the
radar set is unable to observe the signal from the mortar shell
against the background of signals from the antiradar reflectors,
i.e., when the interference will appear on the screen of the
set as one solid blip (odna sploshnaya otmetka).
The mutual distance of two or more bursts of antiradar
shells, ensuring the creation of a solid blip on the screen of
the radar set, depends on the resolution (razreshayushchaya
sposobnost) of the set and its distance from the mortar being
concealed.
The most probable angles of displacement of the plane of
observation of the enemy radar sets in relation to the plane of
fire during radar reconnaissance of mortar firing positions
under practicable conditions, should be considered to be
angles on the order of 450 to 850. Therefore, for complete
illumination (sploshnoy zasvet) of the screen of the enemy radar
set, it is essential that the distance between the bursts of anti-
radar shells should not exceed the magnitude of the bearing re-
solution of the set, at the given distance of the set from the
plane of fire of the mortar.
The bearing resolution of a radar (Sketch 3), as is known,
depends on the width of the antenna radiation pattern and can
be calculated by the formula :
MQ = R I!ni R- (6)
57.3
R
- distance between the radar and the target (in meters);
A f3
-- width of the radiation pattern of the radar antenna
(in degrees).
AS SE ET
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SECRET
Table 13 gives numerical values for the distances between
bursts of antiradar shells (Ajd) ensuring the creation of
effective jamming of the American AN/MPQ-10 set to
conceal a firing mortar, under varying distances of the sets from
the target (R).
Table 13
R in km
I
E 5
:1
6
7
8
9
10
=
in meters
435
520
600
690
760
870
To conceal the trajectory of a mortar shell from radar
reconnaissance by the British FA No.1 M1 set, which has an
antenna radiation pattern 1.50 wide, the distance between
bursts of antiradar shells must be approximately those shown
in Table 14.
Table 14
R in km
5
6
7
8
4L'fo-= s
in meters
130
156
182
208
In concealing the trajectory of a mortar shell, when
radar reconnaissance is conducted in the direction coinciding
or almost coinciding with the plane of mortar fire, the distance
between the bursts of antiradar mortar shells also must not ex-
ceed the bearing resolution of the radar. Moreover, in this
CF~cpFT
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AdSkRET
case the deviation of the cloud of reflectors from the tra-
jectory of the concealed mortar shell in the plane of fire
must not exceed the range resolution of the set at a range of
(,A r), which is mainly determined by the pulse duration of
the radar (Sketch 4) and may be approximately determined by the
formula :
Or
C -Z-
2 ,
(7)
C - the speed of radio waves (assumed to equal the
speed of light - 300,000 km a see);
Z - pulse duration of the radar set, in micro-
seconds (mksek).
In the case of concealing a mortar shell trajectory
from reconnaissance by an AN/dP -10 radar set (T-0.8 micro-
seconds), the distance between the plane of fire and the cloud
of reflectors must not exceed 300 meters; and in the case of
concealment from a FA No. 1 NMI radar set, this distance must not
exceed 40 meters.
The length of the interval between bursts, and the number of
bursts of antiradar shells on the ascending sector of trajectory
which are needed for reliable concealment of the firing position
of a firing mortar, will depend on the range of fire and on the
minimum section of the trajectory of the mortar shell necessary
for the radar to determine the coordinates of the firing position.
The minimum length of sector of the trajectory of the
mortar shell (4 observation )*, from which a radar set can determine
the coordinates of the firing position, is determined by the operat-
ing time of the computer and the speed of flight of the mortar
shell.
* (-Q nabl) in original
-13-
RIFT
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sEc
The operating time of the computers of modern radar sets
is approximately 3 or 4 seconds. When the speed of flight of
a mortar shell is 150 to 180 meters a second, the minimal
sector of the trajectory required to get a fix on a firing
mortar will be 450 to 540 meters.
To prolong the time that the cloud of antiradar reflectors
will remain large enough to ensure concealment, it is necessary,
to displace the point of burst of the antiradar mortar shell upward
and in the direction opposite to the direction of the wind~in
relation to the flight trajectory of the mortar shell being
concealed. The amount of this displacement will depend on the
speed of the wind, the rate of descent of the dipoles, and on
the bearing resolution of the radar against which the conceal-
ment is carried out.
The burst of antiradar mortar shells must be carried out
at such a distance from the flight trajectory of the mortar
shell being concealed which would not exceed the magnitude of
the bearing resolution of the enemy radar.
The lateral displacement of the cloud of reflectors in
relation to the concealed plane of fire may be calculated by
the formula:
ILW sin (D.,
(8)
i\ ~ - the bearing resolution of the radar (in meters);
to -- the lead time of burst of antiradar mortar shells
(in seconds) (includes the time of flight of the
mortar shell being concealed up to the cloud of
reflectors and the time needed for the formation
of the cloud itself);
W wind speed (meters a second);
0 - the direction of the wind relative to the plane of
fire (in degrees).
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AMO"ET
The vertical displacement of the cloud of reflectors in the
plane of fire being concealed may be calculated according to the
formula :
SV =Ae + Vovtu
(9)
Ale - the bearing resolution of the radar (in meters);
Vov - the rate of descent of the antiradar reflectors
'- (in meters per second);
to - lead time of the burst of antiradar mortar shells
(in seconds).
For example, if the distance of an AN/MFQ-10 set from the
mortar that is firing is 6 kilometers, 0R= 520 meters, the rate
of descent of the dipoles Vov 2.0 meters a second, the wind
speed W= 15 meters a second., and cD = 90 , then the bursts of anti-
radar mortar shells should occur 20 seconds before the mortar
shells being concealed are fired (rate of fire, l0 seconds): with
displacement: in direction Sb = 280 meters: in height Sv = 560 meters.
Because the rate of descent of the cloud of reflectors is
considerably lower than the speed at which it is displaced by
air currents, the duration of effectiveness of passive Jamming
of the radar set will also basically depend on the wind speed.
This time may be calculated approximately by the following formula:
tD = 2 0X + to ? (10)
W sin cD
For example, when (&-e = 520 meters, W = 10 meters a second, and
0 = 900, the duration of interference, t 2 minutes; and if
0 = 450, 1 = 160 seconds.
Therefore, the rate of fire with antiradar mortar shells will
be determined first of all by the duration of passive jamming
of the enemy radar set.
-15
50X1-HUM
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Passive jamming of enemy field artillery radar sets,
created with the aid of antiradar mortar shells may be "point"
(tochechnyy), random (raspredelennyy), or grouped (obyemnyy).
"Point" interference may be created by means of periodic
bursts of antiradar mortar shells at one point on the ascending)
phases (veto) of the trajectories of not more than one or two
firing mortars. This interference is most effective when the
mortars are firing at ranges at which the heights of the tra-
jectories do not exceed 1000 to 1200 meters. In this case,
passive interference does not hinder the detection of mortar
shells in their trajectory; but it also does not allow the
possibility of determining the coordinates of the firing posi-
tions of the mortars that are firing, because the automatic
tracking of the mortar shells during their flight in the ascend-
ing phase of the trajectory is precluded.
For example, when firing with single mortars in order to save
antiradar mortar shells, the intervals between bursts of these mortar
shells may be permitted to be twice the magnitude of the bearing
resolution of the radar set.
In this case the blips from the mortar shells may be observed
on the screen of the radar set in the intervals between the blips
from passive interference created by the clouds of antiradar re-
flectors. However, the tracking of the mortar shell and the determin-
ation of the coordinates of the firing position of the mortar that
is firing with the aid of the radar set becomes impossible.
When creating "point" interference, the cloud of reflectors
made by the burst of an antiradar mortar shell takes place in the
middle of the ascending sector of the flight trajectory of the
mortar shell being concealed, as observed by the radar.
The sectors of the trajectory below and above the cloud of
reflectors are not sufficient to determine the coordinates of the
firing position of the mortar that is firing, because the working
time of the computer of a radar set is limited.
-16-
SGRET
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SECT
To conceal the firing position of 82mm or 120mm caliber
mortars that are firing, the heights of burst of antiradar mortar
shells should be approximately 700 to 800 meters; and for 160mm
caliber mortars, approximately 1000 meters.
The fixing of firing mortars by AN/I'Q-10 type radar sets,
in the presence of "point" interference, becomes possible if
the cloud of reflectors is located more than 200 meters away in
range, and not less than 0 -- 60 in direction, from the trajectory
of the mortar shell being concealed. If the cloud of reflectors
is located at shorter distanee+sfrom the trajectory of the mortar
shell being concealed, then the above-mentioned radar sets, after
starting to track the mortar shell, will, as a rule, lose the
mortar shell as it passes near the cloud of reflectors and will
lock on to the signal from the passive interference.
The detection of firing mortars with the aid of the above-
mentioned radar sets, under standard conditions (pri tablichnykh
usloviyakh) of fire, becomes possible approximately 1 to 2 minutes
after the creation of passive interference, and the determination
of the coordinates of the firing position of the firing mortar in
2.5 to 3 minutes.
When the trajectory of the mortar shell is more than 600 meters
above the cloud of reflectors, it is possible to track it by radar
and to determine the coordinates of the firing position of the mortar,
In this case, however, the errors in determining the coordinates are in-
creased by approximately 40 to 50 meters owing to insufficient accuracy
in extrapolation of the initial sector of the trajectory by the set's
instruments.
To create "point" interference during a wind with an average speed
of 15 to 20 meters per second, it is necessary to create a cloud of
reflectors approximately every 2 to 3 minutes, for which a rate of fire
of 30 seconds is assigned, firing antiradar mortar shells after each
five or six conventional mortar shells.
To create the most effective "point" passive radio interference,
it is advisable to fire the antiradar mortar shells from the mortar
whose trajectory is being concealed.
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SE
The effectiveness of "point" interference is considerably
reduced when the crew operating the radar set has had experience
in working under conditions of interference, particularly when
tracking manually.
Random interference is created by a burst of antiradar
mortar shells at several points along the ascending sector of the
trajectory. In this case the distance between bursts must not
exceed the magnitude of the bearing resolution of the radar.
The lower cloud of reflectors should be positioned at a
height of about 500 to 600 meters. The height of the upper
cloud is determined by the height of the flight trajectory of the
mortar shell being concealed. Therefore, the total number of
intermediate bursts depends on the height of the trajectory. When
the height of the trajectory exceeds 1000 meters, it is necessary
to create radio interference at two or three points along the
ascending sector of the trajectory.
The duration of radio interference and, consequently, the
rate of fire with antiradar mortar shells, is determined, as in
the case of "point" interference, chiefly by the speed and the
direction of the wind. With a wind speed of 9 meters a second and
its direction 500 to 60? to the plane of fire, the rate of fire should
be approximately 20 to 30 seconds. With an increase in the wind
speed, the rate of fire should also increase.
Random radio interference renders it impossible for the
radar sets not only to determine the coordinates of the firing
positions of mortars that are firing but also to detect the mortar
shells in trajectory. Thus, random interference is much more
effective than "point" interference and may be used more success-
fully to conceal the fire of mortar batteries.
Grouped radio interference may be used to conceal the fire
of a group of mortars.
In firing with a group of mortars in one direction, the
necessary dimensions of the volume of space (depth, height, and width
along the front) to be concealed from enemy radar reconnaissance may be selected
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beforehand, depending on the conditions for firing, the relative
disposition of the mortars and the enemy radar sets, and also on
the speed and the direction of the wind in relation to the plane
of fire. This type of interference may also be created during
adjustment of fire by mortars on several targets at different ranges.
When creating grouped interference, the bursts of antiradar
mortar shells must be distributed by range, width, and height. The
distance between the bursts must be approximately equal to the
bearing resolution of those enemy radar sets from whose reconnaissance
the fire positions are being concealed.
The number of mortars employed to create grouped interference
is determined first of all by the magnitude-of space to be concealed.
The "interfering" mortars and the mortars being concealed are,
as a rule, located at a single firing position.
The duration of grouped interference is somewhat longer than
that of the types of interference described above, and lasts approxi-
mately 2.5 to 3 minutes. At the expiration of this period it is
necessary to supplement the cloud of reflectors in the space being
concealed.
Ordinary leaflet mortar shells filled with antiradar reflectors
may also be used, besides the special antiradar mortar shells, to
create passive radio interference.
To make enemy radar reconnaissance of firing positions of firing
mortars more difficult, various organizational measures may be carried
out in addition to the destruction (neutralization) of the reconnais-
sance radar sets by artillery fire and the creation of active and
passive radio jamming of them. Among such measures are fire
of roving mortars from decoy positions, salvo firing by mortar batter-
ies, and many others.
This article contains some preliminary considerations on the
creation of passive jamming of radar sets engaged in reconnais-
sance of firing mortars (guns).
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MWSE ET
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The suggested methods of creating passive interference re-
quire testing in practice by troops and further development.
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~ do SEL~RET
The sector of the trajectory being
determined by the radar
c~!;.
The sector of the
trajectory being deter-
tt,mined by calculation
(e/Ctra tion )
Sketch 1: The use of a radar set to determine the
firing position of a mortar that is firing.
_SF('QFT
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SEC ET
Elementary reflecting
impulse volume of the
radar
SKETCH 2: The possibility of observing separate
targets on the screen of a radar set
Editors comment: Ts stands for Russian word Tsel -
target.
SECRET
Ts 3
- -
\1iprom
To 1 and To 2
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SKETCH 3: Bearing resolution of a
radar set (61)
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C F(~I? FT
Screen
4h: l~L
SKETCH 4: Range resolution of a radar set
(LIr)
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Trr jectory of a combat
morta shell
antiradar reflectors
a jectory of antiradar
\,~iortar shell
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