RADAR, AIRBORNE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600210267-3
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 10
• Document Creation Date: December 22, 2016
• Document Release Date: June 23, 2011
• Sequence Number: 267
• Publication Date: March 1, 1949
• Content Type: REPORT

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50X1-HUM
DATE
PUBLISHED
LANGUAGE'
PUBLISHED Monthly periodical
WHERE
PUBLISHED Moscow
..,~a.'',145SIFt .& ON
CENTMAL INTEL.i_IGENCE AGENCY -
CONFIDE!ITlrw
MUNTRY ;- a
SUBJECT aiboa-ir.e
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a'mOO$T$O000100.000n00b0Me00010101
n011xo ;W Y!. .000001000101 001t0 MVW 0000 a 10 100101101.
April 1948
Russian
1u TRW 11 O"a 0 5MleY VoR. U 000%* um s~nsw~ 000001.0
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Teatnik Vordushno k lots
rbques ed.,
The purpose of this article is to describe briefly the following three
radar. (1) Radar in the interceptor, (2) Fader to warn of dangers in the
rear, (3) Radar for identifying aircraft,
1. Hadar in the Interceptor
The success of fighter planes in action in World War II was lergsly
determined by use of radar. Ir daytime, fighters were aided by groom]-based
radar which located friendly and enemy aircraft; ground-based radio We
friendly aircraft detailed instructions concerning the course to follow to
meet the enemy. At night, however, such orientation was insufficient; to
facilitate attack under night oonditiode, another instrument in the fighter
was required to enabla the pilot, after ruching the enany area, to amemo s
favorable attaoklW position and to close on his opponent; at progvr range.
Such devious, called interceptor radar. were built and installed in
two-seater fighters. It vas the radar operetor'a duty to give the pilot neces-
sary directions for contacting the enemy.
The basic units of radar are transmitter, receiver, coarser, antenna,
and pow-, imf t .
The trena fitter generates short, high-frequency pulses which are
radiated from a transmitting anccenna in hemispherical wave fronts; are reflected,
then eiVlii'ied by the receiver and finally delivered to the indicator.
No IL, 1948 (m J
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L.et us now examine how I.nt',-ecpt.e*- radar determined the polar
co^r-'irates of the target. Figure 1 thcve the snt?enna system and other radar
webs on the plena. Tvo re-.O-ring tor "soei {., ;l,etermine the eleva-
tion angle. One antenna ]e^ placed H.bovs the wing nu---ieee, the other under-
neath, The directional lobos from the upper ant lower =term are such that
the echo pulses reflected from e rcraft .bore the line of flight, are received
more strongly by the upper antenna, vhi15 three from aircraft, beneath the line
of flight are .received more strongly by the least antenna (Figure 2,a),
Signals reflected fr= the. targci?:ter: m3ceived by the antennae are
brought through a switch to the re.eiae ant thence to the elevation indicator
(Figure 2, c). By means of the owit;h, the upper and. 1cver antennas are
connected eltarn.tely with the recr17Ar, There are aler. switches in the indi-
cator by means of which incoming signals from the upper antenna produce on the
indicator screen pulse pipe directed upwards from the axial line, while mooning
signals from the lower antenna produce impulse pipe directed downwards. The
intensity of these signala received by the antennas depandren the position of
th? target which a fecte the amplitude of the reflected echo pulses. The great-
or the , dl-flectian of the pulses upwa-rde from the axial line, for example, the
nlO!t:r cue target's position.
Pulses from three planes in the same position in relation to the line
of Plight an those in Figure 2,a a shown on the elevation indicator in Figure
2,b (distance to the first plane, one kilometer; to the second, 2 kilometers;
end to the third, 3 kilometers).
The azimuth of the target is calhulated in the same manner an the
elevation anglea by wwane of two antennae placed on the right and, left olds of
the plane. Directional lobe, of these antennas are shown in Figure 2,0.
The three planes shown in Figure 2,b are projected on a horizontal
plane an shown in Figure 2,o. Figure 2,d shove the echo pulses from these
planes on the azimuth indicator.
To eumnarize the obeerratione from the elevation indicator ana the
acinrath indicator: it may be said that plans 2 is on the right and above the
line of flight at a distance of 2 kilometers; plane 3 to to the left and below
at a distance of 3 kilometers; and plane 1 to one kilometer in fiont of the
fighter.
Let no examine a radar net the marker of which has two indicators.
Th.r- are also radar markers with a larger number of indioatore, but they are
not widely used because they make the work of the operator too complicated.
Practical use has been made of markzre that permit eimiltaneously
scanning the field of view on ^nlv one indicator. In particular, use has
beep made of markers an indicators n which the plane appears in the form of a
ring of l anus dicta (Figure 3). To brightness of the warioss parts of this
ring Is not uniform and depends on the position of the 'c vsted plane in rely-
tiun to the course of the fighter, If the airplane is exactly in front of the
fighter, it will appear as a ring of uaifarsn brightness (Figure 3,9). Any
deflection of the plans from the axis of the fighter's flight will decrease the
brightness of the ring an the side opposite to the airplane's deflection
(Figure 3,b). The r5dius of the ring determines the target re'ge.
The advantage of this arloar as compared with thoe6 examined earlier
is that the operator needs to watch only ow screen.
other tipee of indicator, are also used in interceptor radar. Ve shall
touch upon them is describing more modern appetatus.
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Figure 4 shows interceptor radar in which the trc imitting antenna is
placed on the nose of the plaza; the elevation angle antennae are located on
the left outer panel end the azimuth antennas are located on the right and
left sides of the fuselage. There hale been other methode of placing the re-
ceiving antennas. One, in particular, is to install all four receiving anteams
on the right and left outer panels. Another method is to put the whole antenna
system in the nose of the plane (P'gures >? and 5)? All these ante -me are very
large and seriously impair the a.. Ayaamic properties of the airplane.
The first interceptor radar operated on a nave length from one meter
to one decimeter. With these rather long eaves it was not possible to obtain
a sufficiently wide field of search because of the narrow direotinal lobes and
because of limitations in the over-all dimensions of antennae permissible in
aircraft . Thi a type of antenna emit j pulses in a wide beam and a considerable
part of the radiated energy falls on the earth's surface. At distances greater
than the fighter's altitude, the signals reflected from the earth completely
meek the echo signal from the target (Figures 2 and 3). Hence, the range of
detection depends on the altitude. To eliminate this dependence, narrower
directional lobes were necessary. This was accomplished by employing centi-
meter wares.
The antenna of radar operating on centimeter waves is a half-vane radar
horn located at the focus of a ruebolic reflector. The smaller over-a.11 di-
mansions of the reflector nuke it :iseible to install the antenna inside the
nose of the fuselage. The directional lobe of this type of antes Is a narrow
beam, only a few degrees wide. But it is difficult to detect a target with such
a narrow beam since it covers only a small part of the forward hemisphere. In
order that a large part of the fie?:d may be scanned by radar, the antenna is
rotated.
In this case (Figure 6), the mi..ker indicator has a radial arm or
cursor which rotates synchronously with the angular rotation of the antenna
beam, Usually the arm is not visible on the indicator; but when echo signals
are reooived from the +-vget, a bright spot at s certain point, corresponding
to the distance from the target, will be formed on the arm. When the target
is eoanared by a rotatia beam, luminous points emerge in a mueber of contiguous
radial arms and thus form a small luminous arc. The width of the arc is deter-
mined by the amount of the target's divergence from the line of flight. The
greater this divergence from the antenna ails, the narrower the arc, since the
been rotates and remains on the target only for a short time. If the fighter
is folloring its target, the target is exposed to radiation throughout the
entire rotating sweep of the beam and thus a closed ring vill appear on the
indicator.
For convenience in observing the target at short ranges an the
fighter, the scale of the indicator begins a escort spaob from the center and
forms a luainone ring of s?sall diameter (first reading ring). The Indicator
in Figure 6 also above the so-called altimeter ritag, which Is fo ne& by the
reflection from the earth's surface of the seal,. undirected aide lobes radiat-
ing from the radar ante=&. Soho signals from the earth's surface produce
light spots on the eoreen. These spots do not nateriwlly affect the range oZ
radar detection.
Intercepvor .,radar, which his appeared sins' World War II, is now much
improved. Weight and over-all air-melons have been decreased and they are more
reliable and simpler to operate. ?nong the most important iagpa'areaaento ar'e
as*tcwtRtio tranidag in - "aok and an ino,reneed scanning field.
Autcsactic radar tracking greatly increases reliability of aircraft
interception under all atmospheric conditions and also decreases probability
of missing the target, Increased range makes it possible for the crew to be
well. prepared for attack.
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50X1-HUM
This never radar is installed on the plane in the following positions;
antenna, transmitter, and high-frequency parts of the receiver are in the nose;
i:,d.teatcr, manual search song-^' e.-O various other control and auxiliary
apparatus, near the operator; on the pilot's panel are indicator and devices
that show target range and velocity of approach.
The radar antenna is a'half-nave dipole, located at the focus of a
parabolic reflector. The lobes of rna imum power emitted'by the antemma are
slightly to the sides of the axis. Beoarse of tho rotation of the dipole, the
radar armnoing field is enlarges and the axis of t iuuin antenna emission
describes a cone. In the prrocess of scanning, the antenna reflector tares
slowly to the right and left. This increases the radar field of scanning to
the sides.
While scanning, the operator examines the air situation by an. of
his indicator, on which he seen the pulses from all planes within his field of
search (Figure 7). Azimuth angles arr measured on the "mdioatos alaog the
horizontal axie, and target ranges are measured along the vertical axis. A
faint vertical band Indicates the angle of deviation of the antessa from the
axial line, The band. rotates on the screen proportionally to the`sn2s of the
antenna reflector.
During search, no targets at all are seen on the isdlcatca is the
aoont; ani.y the horizon line is to be seen (Figure 8). The posttiaa of the
noriaon line shown ,be. mint him plane Is movements an upward or 8avssrard
deflection of the hoiacn Ins trcoc the horiscantndl.t a below the were Udi-
oatee tl'tt the airpjAus to pitching or diving; an Inclination to left or right
denotes left or right banking.
After selecting his target before attack, the operator first detarainee
the position of the entena in relation to the target by manual ecutrol and then
shifts to automatio target tracking botL for direotiom and range.
After the automatic target-treok3ng derice is switched in, the target
silhouette of the airplane appears on the pilot's indicator (Figure 8). The
position of the center of the silhouette shows the pilot the amount of the
target's deflection.
Switching devices show simnltansonsly the target range and the velocity
of approach. By watching his instruments, the pilot establishes all aspects of
flight and directs his plane in such a tanner that the center of the silhouette
coincides with the center of the indicator.
The span of the silhouette increases in proportion to the proximity of
the erieny. The pilot opens firs rt the mcoent when the wing tips reach the
vertical mart on the.asiai lines of the indicator.
Tnteroeptrr rear can be used for purposes other than their prinrry
task. They may servo to guide an airplane to its a.rdraos and also to permit
blind loadings.
q. l-adar Devices to Warn of Danger in the Hoar
enemy
For rear hemisphere observation and for warning the crew of
app meoh, so-called rear-warning radar is used. 1' a sec lc inatal3 d, both
on fighters era bombers. There are two types, one for passive and one for
active warning.
Devices for passive warning consist of a receiver and transmitter an
op*rate only after exposure to the enemy interceptor radar. Such instrument;
are very simple, but their use demands knowledge of the freou.noy of the easy
int,rc ptor radar. For this reason, the devices for passive warning are rarely
need.
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Rear-warning sets for active warning are radar sets which detect an
enemy by echo signals,
Their basic units are: transmitter with amodu]etor, receiver,, antenna,
inulcator, and power unit (Figure 9).
An antenna installed on the wing is employed for simml and trarumd.esion
reception.
The method of signalirw the crew differs with the type of inetrunesat.
The following eigoaling methods are in use: sounding of electric buzzers; audio
signals through the intercommunication system (SFU); flashing signals, and indl-
cations on cathode-ray tubes.
For greater reliability in warning the crew, combinations of several
types of signaling are sometimes used,
The instruments used in intercom annd. the cathode-ray tubes are the only
warning devices that indicate in some way the distance of the approaching hostile
aircraft..
The defects of the rear-waarming devices in use are their small rsemge and
inability to identify detected targets.
In view of the fact that the lobe width of the beams radiated from the
antenna of rear'w rningdevices is rather large, strong refleotioas.fro the
earth's surface can be observed on the instruments. Rigmle boarcing from the
earth unfortunately register on the rear warning instruments and may thus mis-
lead the crew. Hence, the range of these devices must t,m intentionally restricted
so that they can be employed even at low altitudes.
To protect the rear hemisphere of heavy bombers, more ocsplioated In-
struments are used. These do not merely -mrn, but also aid in'cooriinating fire
from the guar. We call such instruments "radar shooting eights." Some of
then operate entirely on optical sights and are employed to determine the target
range. They carry out automatic target-tracking according to distaaoe. The
data supplied by them are fed into a mathematical oomputor.
3. 7isdar Devices for Identifying Aircraft
Success in the tactical employment of radar entirely depends upm the
ability to identify quickly and positively any target appearing within the
radar station's field of scanning, B %&r e~.cione without special equipment
for identifying aircraft would be completely unable to 8istinguish friendly
aircraft from enemy craft. The aircraft in first Judged by type, its flight
course, and by data from observation posts. To facilitate further Identifies-
tion of friendly aircraft, various mane-mere are executed by t:!e plans. For
examle, following acusande from the ground station, the airplane to be idedti-
fied (if friendly) must execute scale specific maneuver which has been previously
recorded for reference on the radar plotting board or even directly m the indi-
cator. tThus, the airplane may fly in a square, or weave, etc.)
None of these methods of identification is very-satisfactory, because
they are indefinite and ',ims oonsuming. Besides, it is not slsuayx possible to
employ them. Therefore, it is necessary to construct and 1.nstc.1l apperatur as
the planes themselves which will cause its presence to be immediately registered
on friendly radar indicators.
The earliest of these airborne xericas ward a simple antenna tvasd t:~
radar frequency. With aid of a special switch, the antenrr, was altersstely
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connected and disconnected so that it produced, a periodic pettorn in the ampli-
tude of the echo signals. by the presence or absence of these echo-pulse code
patterns in the radar indicator, friendly aircraft can be distinguished from
hostile craft. But this system of identification has many serious defects and
w,,n never very widely used.
An iasLroved apparatus made its appearrnce after this ode. Instead of
the antenna, a transceiver was used, which was a type of airborne beacon for
radar signals.
As long as the airplane is not exposed to radar waves, this transceiver
a?ta as a receiver. When the airplane is exposed to radar waves, the radar
pulses are received and then amplified by the receiver and finally cause the
transmitter automatically to emit radar identification signals (beacon signals)
on a frequency equal to the radar frequency and with an aaplitads *=what
greater than that of the echo signals. The beacon signaa are preps tad
Immediately after the echo signals and, therefore, appear on the radar iadi-
oator, along with the original echo pulses, in the form of pulse pipe with an
amplitude slightly greater than that of the echo signals (Figure 10).
So that ordinary refleoted pulses may b? differentiated from beacon
signals, the identification apparatus is so constructed, that it does not tr+emit
reply or beacon eiLj? on every pulse but skips a certain number of palace.
Thee, unlike echo impulses, the beacon signal pulses alternately appear and,
disappear (fl cker). To prevent the enemy from imitating beacon sig=ns, the
apparatus has a coding device which makes it possible to olaage both the durs-
tion of the Impulses and their successive alternations woorAin to a fisod
schedule. Thus, aircraft identification is carried mt, not only through the
presence or absence of signals but also through coding.
Such a system we call "point identification." Detection and identifi-
cation are here carried out on the same wave. These devices one designed to
permit cooperation between radar stations, airborne or ground-based, which
differed only slightly An their operational frequencies. With the continual
development of radar and the Psppearence of many stations operating on s greet
variety of wave lengths, the construction of existing derides had to be changed
in order to enlarge their frequency bands.
0
Tice system is completely eneatis"aotory from the standpoint of uui-
versality. Thus, with the use of raw wave lengths in radar, it :s necessary
oonstalaxtly to increase the weight ant volume of airplane equipment, which is
obviously Limited.
The system I. extravagant in operation. Thus, the identification
device operates during the whole period of exposure of the &I.-.plane to radar,
although only a vary few reply ulgwls are needed for identification.
Because the saw ,rave length is used in deteotia and identification,
the beacon signals from adjacent aircraft can a feet the operation of these
devices.
In semi-autonomous beacon systems a partial separation has been .wade
between detection waves and identification waves. This was effected bl, tuning
the aircraft receiver to the rada.' wave; but the Transmitter monde identifying
signals on a frequency different from that of the radar apparatus. Special
receivers are supplied to receive signals by radar.
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coi+F.In2rlar, .
The semi-aut s beacon system eliminatee the defects oc noted with
the possibility of confusion with interrogators but all the ether defects in
the "Joint identification system" also occur in the send-autonomous system.
Immediately after the semi-autonomous systems, the autanomms bosom
eystems made their appearance, in which independent (autosomous) tregnenoy
ranges were used.
The absolute assignment of a certain band to be used m1w ter identifi-
cation made it possible to eliminate the chief defect of the previuas y,
mentioned systems and to install a great number of identification devices on
aircraft. To semi reply signals by the autonomous system, there is `astalled
on each pane a device, the "resposader," which answers the "intorro tor:
But for all radar apparatus, whether an the ground or in aircraft, there are
also special attachments the interroi tore or ohellengers.
The principle on which the autonomous beacon cystesa operates is shown
in figure 11.
After a target bee been detected by radar, the inWITOGator is then
switched in. The interrogntor is considerably lees powerful than the raes-r
apparatus, but is powerful. enough .to emit Inquiry pulses which strike the
plane to be identified. But since the pules,of the interrojptorare cam-
siderably, weaker than noz l radar pulses, their reflectiosr liar the fuse-
lage fade rapidly eaAcaannot be detected by an interrogator.
The.respomier operates only when the interrogator is switched in.
In autonomous systems this eliminates the defect connected with the protracted.
operation of interrogators used in joint identification systems.
,figures follow]
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Directional lobes emitted
from upper and lower
antennas for measuring
eletatfion angles
Directional lobes of
right sixi left asim t3
ione
1(0)
of Rem of h
T.wnraa:tter elevation angles ,?
pulase \ ~ e..~`
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Befledtlone from earth (by
eohm pu.Zaea)
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Reflection
from earth
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~1Y f
C.e
Direct rMor BiE* &
+ echo si~oial.
Direct Signal
I/-I of .aterro?nto .._
- HeF19 eitml of "eePoOder
sat rnas t,laa Uho sipal
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