THIS DOCUMENT SHOW HOW RADIO WAVES ARE GENERATED FROM A WIRE CARRYING CURRENT, Essays for Wireless and Satellite Communication. Midlands State University
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THIS DOCUMENT SHOW HOW RADIO WAVES ARE GENERATED FROM A WIRE CARRYING CURRENT, Essays for Wireless and Satellite Communication. Midlands State University

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M

AIR FORCE SYSTEMS COMMAND

WRIOHT-f ATTERSON AIR FORCE BASE

OHIO

ram a

This document is a machine translation of Russian

text which has been processed by the AN/QSQ-l6(Af-2)

Machine Translator, owned and operated by the United

States Air Force. The machine output has been post-

odited to correct lor major ambiguities of meaning,

words missing from the machine's dictionary, and words

out of the context of meaning. The sentence word

order has been partially rearranged for readability.

The content of this translation does not indicate

editorial accuracy, nor does it indicate ÜSAF approval

or disapproval of the material translated.

FTD-MT- 65-58

EDITED MACHINE TRANSLATION

PRINCIPLES OF RADIO DIRECTION FINDING (CHAPTERS 9# 10, and 11)

By I I. S. Kukes and M. Ye, Star lie

English Pagesi 65

SOURCEi Osnovy Radlopelengatsll (Russian), Izdatel'stvo Sovetskoye Radio, Moskva, I962, pp. 517-541 and 636-640,

TMRRno^on

THIS TRANSLATION IS A RENDITION OP THI ORIGI- NAL PORIIGN Tf MT WITHOUT ANY ANALYTICAL OR EDITORIAL COMMENT. STATEMENTS OR THEORIES ADVOCATED OR IMPLIED ARE THOSE OP THE SOURCE AND DO NOT NECESSARILY REFLECT THE POSITION OR OPINION OP THE POREION TECNNOLOGY D|. VISION.

PREPARED BYi

TRANSLATION DIVISION FOREIGN TECHNOLOGY DIVISION «P-APt, OHIO.

FTP-MT- 6-58 DM> 6 Aug 1965

!

TABLE OF CONTENTS

u. 8. Board on Oeographlo Names Trana 11 tarnt Ion System,.,, , vl Designatlona of the Trigonometrie Functions,.. ,..,, vll

Preface , , ,, ^ Chapter 1, The Problem of Radio Direction Finding [RDF] , 5 Chapter 2, The Principles and Methods of RDF , 11

2.1. The Electromagnetic Field and Its Polarization , 11 2.2. The Principles of RDF , , 15 2.3. RDF Methods 20

Phase Methods of RDF II 2.4. Radio Direction Finder Errors , 'J 2.5. The S/N Ratio at the Receiver Output JH

Noise Strength at the Receiver Input., 'u

The S/N Ratio at the Output of the Linear Section of the Receiver • 41 The S/N Ratio at the Detector Output 42

2.6. Selection of Transmission Band , 44 2.7. Sensitivity During Audio Bearing Reading from the Minimum 48 2.8. Sensitivity of the Radio Direction Finder Using the Comparison

Me t hod 52 2.9. Sensitivity of Direction Finding by Minimum Percentage

Modulation 5$ 2.10. Sensitivity of Direction Finding by the Phase Method,, 6? 2.11. Sensitivity of a Two-Channel RDF ,. ,,, 66 2.12. Nolaeprooflng of RDF 69

Chapter 3, RDF Antenna Systems,,. ., 76 3.1. Vertical Antenna 77 3.2, Folded-Dlpole Antenna , , 87 3.3* Frame Antenna, , , 88

The EMF In a Small Frame The EMF In a Frame Consisting of Several Loops 92 The Influence of Nonunlform Cvrrent Distribution 94

3.4. Shielded Frames 97 3.5. Frames with Ferromagnetic Cores 99 3.6. Reception with Two Spaced Antennas 102 3.7. A System of Two Spaced Frames 105 3.8. Combined Reception on an Open Antenna and a Directional

System 109 3.9. Fixed Directional Antennas with a Coslnusoldal Directivity

Characteristic ,,... 113 3.10. A Goniometrie System of n Spaced Antennas.,,,, • 113

An Equivalent Circuit for Calculation 121 A System with Parallel Coupling of Adjacent Antennas,,. 131

3.11. Antenna Systems with Sharp Directivity Characteristic 13? The Use of n Antennas In a Row.... 132 Circular Antenna Systems with Sharp Directivity Charscterlstlc 140

-1-

3.12. Antennas with Logarithmic Structur« • IK 3.13. RDF Antenna System! for SHF...... 161 3.14. Parallel Operation of RDF Recelvere from a Common Antenna

System , , , , 16 »5 Chapter 4, Instrument Error 168

4.1, RDF Instrument Errors , , 16R 4.2, The Antenna Effect In a Rotatable Loop 168 4.3, Eliminating the Antenna Effect In a Rntatable Loop , 174 4.4, Instrument Errors of a System with a Rotatable Loop, 17fl 4.5, The Antenna Effect In a Oonlometrlc System 182 4.6, Errors In the Oonlometrlc System Ifl6 4.7, Oonlometer-Caused Errors 196 4.8, Instrument Errors of a Spaced-Antenna System 200 4.9, Error In the Spacing of a Oonlometrlc System of n Spaced

Antennas , , , 207 4.10, Adjustment Errors of a Oonlometrlc Spaced-Antenna System 216

Error In Antenna Orientation ,.,, 216 Inequality of the Level of the Basic Antenna 218 Inequality of the Radius of Antenna Positioning 219 Tilt of One of the Antennas 220

4.11, Balancing of the Circuit when Connecting the Antennas with Coaxial Cable 224 The Effect of Inequality of the Electrical Lengths or Cables In the Oonlometrlc System * 225 The Effect of Inequality of the Electrical Lengths of Cables In a Circular Antenna System with Sharp Directivity Characteristic., 231 The Effect of Inequality of the Electrical Lengths of Cables In an RDF with Cyclic HP Phase Measurement 233

Chapter 5, The Influence of Locale and Environment , 235 5.1, The Nature cf the Influence of Locale and Environment,.,, 235 5.2, The Shcre Effect 236

The Influence of Nonunlformlty 'f the ar un1 , 237 The Influence of Unevenness of the Or-und 242

5.3, The Influence of Nearby Objects on the RDF 244 5.4, Types of Back-Radiators 264 5.5, The Effect of an Antenna Located Near an RDF 265

Antenna Located in the Immediate Vicinity cf the RDF 265 Antenna Located Far from the RDF.,... • 272

5.6, The Effect of a Back-Radlatlng Frame 274 5.7, Deviation Caused by the Hull of a Ship 278 5.8, Deviation of a Ship and Airplane RDF 282

Chapter 6. RDF Errors Associated with Radlowave Propagation 285 6.1. The Influence of Abnormal Polarization of the Electrical

Field 285 6.2. Determination of Error Due to Abnormal Polarization of the

Electrical Field 286 6.3. RDF Systems Free of Polarization Errors 290

A Spaced-Frame System 290

-11-

A Spacei-Antennt Syitem. Various Connecting Clreultf.« 290 Syitemi with Pulsed Transmission*•• •.. } k

6.4. Lattral Deviations of Radlowaves of the 8V Range iOJ 6.5, Interference of Radlowaves of the SW Range ••.. 313

Coslnusoldal System.•• ••••••• •• • 3?^ An RDF with Cyclic HP Phase Measurement, 325

Chapter 7*

i

i

I

\

6,6. Features of Direction Finding on Various Wavebands and Selection of an RDF Antenna System • ••••#•• ••• 327 DF on Superlong and Long Waves (Frequency Less Than 100 ke), 327 DF on Middle Waves (Frequency 100-1500 kc) 326 DF on Short Waves (Frequency 1*5-30 He).,.., • ••••** 331 DF on Ultrashort Waves (Frequency 30-300 Me)••••••• 33^ Calculation of RDF Antenna Systems.•••••••••• 336

7.1. Preliminary Concepts. .••.••....••.•..•....... 336 7*2. Input Circuit Noise Factor • 339 7.3. Calculation of the Efficiency of a limed Frame..... 3^5 7.4. Calculation of the Efficiency of a Frame with Inductive

Coupling. ••••.••.•..•• ••••••• •••••••• 349 An Untuned Frame with Inductive Coupling. ..•• 3^9 A Oonlometrlc System with Closed Frames.....•....• • 35^

7.3* Calculation of the Virtual Height and Input Resistance of an Antenna System with Close Spacing of Vertical Antennas (Co- slnusoldal Directivity Characteristic). •• ••• 357 The Influence of the Number of Antennas.«•• 360 Calculation of the Virtual Height and Input Resistance of an Antenna-Feeder System Consisting of a Pair of Antennas« with Direct Coupling of the Antennas to the Feeders •......•..•••. 361

7.6. Calculation of an H-System • 367 Reception of a Vertically Polarized Field.. • 369 Reception of a Horizontally Polarized Field 371 Efficiency Calculation 37^

7.7. Calculation of a U-Syetem 373 7.8. Calculation of Transformer and Balanced Systems....« 378

Calculation of a Transformer System 378 A Balanced H-System with Feeders Directly on the Oround (Fig. 7.21a) 380 A Balanced H-System with Feeders Raised Above the Oround (Pig. 7.21b) 380

7.9. Matching Devices •«.««....«• 381 7.10. Calculation of the Input Circuit of a Matched Antenna System.. 389 7.11. Compensation for Antenna Effects 392 7.12. Calculation of the Elements to Compensate for Antenna Effects 398 7.13. Calculation of Unidirectional Reception • 401

System with Untuned Vertical Antenna and Tuned Frame 402 System with Untuned Vertical Antenna and Untuned Frame 406 Use of the Antenna Effect of the Frame, and Simplified Systems of Unidirectional Reception • 408 Use of the Grounded Point of Goniometer Field Colls In a System with Spaced Antennas •..•.«.«••••••«««« •.• 409

-111-

Chapter 8, Vltual RDF 411 8.1, Semlradlo Compaifoi • , ,, 411 8.2, Automatic RDF with Servo Drive (Radio CompaBaes) 423 8.3, A Two-Channel Automatic RDF with Visual Bearing Reading 428

Vlaual fleleetlvlty 433 Requirements of the Reception Channel!.,•,, 439 Balancing of the Modules of the Oaln-Factor Channels 446 Adjustment of the Oaln when Using a Pulsed Control Signal ,,., 449 Balancing of the Voltage Phase Shifts In the Channels 452 Obtaining a Unidirectional Bearing.,., ..,,,... 454

8.4, Single-Channel RDF 458 Direction Finders with Two-Tone Modulation (Method of Com- parison of Percentage M lulatlon of the Received Signal) ...*,,, 45^ Direction Finders with Alternate Swltchlng-ln of Antennas and the Indicator [Display Unit] 462 Two-Channel Display Receiver with Partial Grouping of Channels 462

8.5, RDF Instrument Errors Due to Phase Shifts In the Receiver 463 8.6, Phase-Meter RDF , 471

Direction Finders with Mechanical Rotation of the Radiation Pattern 472 Direction Finders with Electrical Rotation of the Radiation Pattern 478 Selection of the Rotation Frequency (Modulation) In Phase- Meter DlrectIon Finders 462

8.7, RDF with Large-Base Antenna System »..,,,,. 483 Amplitude Method of Direction Finding. , 483 Phase Method of Direction Finding 487 Pulsed RDF 498

8.8, RDF with Cyclic HF Phase Measurement ,.. 499 8.9, Automation of Reading and Averaging of the Bearing 510

Chapter 9. Tests of Radio Direction Finders [This Part Translated] 517 [1] 9.1. Laboratory Tests of Direction Finders with a Rotating Loop 517 [1] 9.2. Laboratory Tests of Direction Finders of a Goniometrie System.

Tests of Loops 524 [7] Testing of the Goniometer 525 [7] Test of a Radio Direction Finder as a Whole 531 [12]

9.3. Laboratory Tost» 01* Radio Direction Finders with Wide Antenna Spacing 53? [13]

9.4. Tests of Direction Finders In Real Conditions of Work 534 [Ik] Determining Instrument Error of a Radio Direction Finder 534 [15] Determining the Magnitude and Nature of L'C^l Errors 536 [16] Determining Oeneral Accuracy of a Radio Direction Finder 537 [17] Determining General Sensitivity of a Radio Direction Finder 538 [18] Determining the Directivity Pattern and the Directivity Factor 540 [ 19]

-iv-

Chapter 10. Different Applloationi of Radio Direction rinden fThli Part Translated] 542 [22]

10.1. Ship Radio Direction Plnder. Selection of Site 542 [22] Mounting of the Antenna Array of a Radio Direction Finder 544 f23] Taking the Curve of Deviation of a Ship Radio Direction Finder 545 [?5'\

10.2. Radio Direction Finder on an Aircraft 548 [27] 10.}). Compensation of Deviation In a Radio Direction Finder with a

Rotatable Loop 550 [28] Mechanical Methods of Compensating Deviation ...» • 550 [?9] Electrical Compensation of Deviation by Installing a Loop 552 [30]

10.4. Electrical Compensation of Deviation In a Goniometrie Radio Direction Finder 553 [31] Compensation of Quadrant Deviation D sin 2q • 553 [31] Compensation of Quadrant Deviation I cos 2q • •• 556 [33]

10.5. Land (Airport, Shore) Radio Direction Finder • • 560 [36] Chapter 11. Accuracy of Position Finding by Radio Bearings [This Part

Translated] 371 [43] 11.1. Methods of Estimating a Single Bearing 571 [43] 11.2. Ellipse of Error with n Radio Direction Finder 574 [46] 11.3* Region, Serviced by Two Radio Direction Finders... 589 [57]

Chapter 12. Plotting Radio Bearings on a Chart ••••••••••••••••• 598 12.1. Orientation of the RDF 598 12.2. A Short Description of Charts...., ••••• •••••• 599 12.3« Plotting Radio Bearings on a Chart ••••• 601 12.4. Automation In Site Determination • • 605 12.5. Azimuth Calculation«. ••••.•••••.••••.. 606

Appendix I. Calculation of Frame Parameters. • 609 Appendix II. Derivation of Formulas for Magnetic Fields In a Multlwlndlng

Goniometer ••... • ••• ••.•• •• 614 Appendix III. General Expressions for Parameters of an Elliptical Field...... 616 Appendix IV. Determination of the Direction of the True Meridian... 619 References • ••••••••••.• ••••••••• 622 Subject Index •.••••.. 632

-v-

'

U. S. BOARD ON GEOGRAPHIC NAMES TRANSLITERATION SYSTEM

Block Italic Transliteration Block Italic Transliteration A a A a A, a P P F P R, r B 6 B 6 B, b C c C c S, s B B $ V, v T T T m T, t r r r 9 G, g y y y y U, u A i n 9 D, d <t> ♦ 0 <p F, f E • E * Ye, ye; E, e* X X X X Kh, kh W w m M Zh, zh u u a H Ts, ts 3 • 3 9 Z, z H H H V Ch, ch H N H U I, i HI Ul m Ul Sh, sh ft A a ä Y, y m m m *H Shch, shch K K K K K, k •b % z> % II Jl ii n M L, 1 fal u hi u Y, y M M M M M, m b b b b i H H H H N, n 3 s 3 9 E, e 0 o 0 0 0, o 10 o K) JO Yu, yu n n n H P, P H Jl SI M Ya, ya

* ye initially, after vowels, and after -b, bj £ elsewhere. wH"en written as 6 in Russian, transliterate as ye or 8, The use of diacritical marks is preferred, but such marks may be omitted when expediency dictates.

FOLLOWING ARE THE CORRESPONDING RUSSIAN AND ENGLISH

DESIGNATIONS OF THE TRIGONOMETRIC FUNCTIONS

Russian

in COS

tg ctg sac cosac

h eh th eth eh csch

are sin are eos are tg are ctg are ae are cossc

are h are eh are bh are eth are seh are eseh

English

sin cos tan cot sae CSC

flinh eoah tanh eoth seen esch

sin"1 eos"1 tan"1 eot"^ sac"1 esc"1

sinh"1

cosh"1

tanh"-1

coth"1

sach"1

eseh-I

rot lg

curl log

MT-65-58 Prlnciplei of Radio Direction Finding,

"Soviet Radio" Publishing Home, Motcow, 196^.

Pages 1 517-5^1 and 636-640.

CHAPTER 9

TESTS OP RADIO DIRECTION FINDERS

List of Designations Appearing In Cyrillic

krH k8f - scaling factor

B • fair falrlead BUX - out - output

« • 1 • (definition undetermined)

K - comp compensating

MBKC max - maximum

H - load HC - asyn asynmetrlc

n - f - field coll

P, p loop

$ fd feeder

a - at - standard

a v - variometer

rcc sso - standard signal generator

3 ground

Preliminary tests of radio direction finders aiv performed In laboratories,

final ones are performed In real operating conditions of the direction finder.

9.1. Laboratory Tests of Direction Finders with a Rotating Loop

Separate parts of the direction finder (the loop, variometers, etc.) require

no special tests other than normal ones — measurement of Inductance, capacitance,

resistance, and coupling coefficient. We shall not dwell here on methods of

measurement of these magnitudes.

-1-

During laboratory testing of the direction finder as a whole by a generator of

standard signals there Is required, snslogously to normal measurement of receivers«

use of an equivalent antenna. A peculiarity of the given case Is that receiver-

direction finder Is fed simultaneously from two antennas t a loop and an open

antenna« where the virtual height of the loop changes In a wide range with change of

wavelength, and the phase of the emf Induced in It differs by 90° from the phase of

the emf In the antenna. Furthermore, ordinary generators of standard signals have

an asymmetric output (one pole usually Is grounded). Connection of output terminals

of the generator to the loop creates a symmetry of Its circuit, which may not

correspond to real operating conditions of the loop.

In Fig. 9.1 there Is presented the circuit of the equivalent of the antenna and

the loop, considering these peculiarities. Parameters of the circuits are selected

In such a manner that L p + L ^ « L0, where LQ — Inductance of the loop) L , C ,

R Cfftir "" Inductance, capacitance, and resistance of the antenna and capacitance

of Its falrlead. Under these -onditlona the receiver has normal load both from the

loop and from the antenna.

.11

Fig. 9.1. Diagram of equiv- alent of antenna and loop.

Then we select R » uL^i then the current

through winding L* with sufficient accuracy

(with error of i.%. If R > TooLj) can be

expressed

where E — output voltage of generator. i "

The emf Induced In colls L 2 and L ,«

will be

and voltage on resistance R , corresponding to the emf in the antenna. Is equal to

Coupling between colls L^ and L 2_i, Is made variable by sine law

M *' «n na«« MB §•

During real work the emf In the frame Is

the emf In the antenna Is £,B/EA,sin*.

«s-EV

-2-

We tquate I n - 1^, E l Ilo0p and ol - 1, wher« a - factor, whI-h ';:

convonlently Bolf'i.ml oqual Ln any rowl numlM.T (1, ?, »...l/^i V'» V1'» 'J'''-»)«

From thli w« find

•T-T&^-Ä '"diTP,,-fr- Slnct hj^ Is proportional to frequency h^ - ^ ■ ■"*ft| the late equality girSN ^

" J.10' Is realisable In the whole range of frequencies Proa It we find HIUJit after which,

given a, we find R, The reading on the divider dial of the generator of standard

signals, multiplied by a, gives field strength in microvolts/meter.

By this circuit we can perform the following testst

1. Determining sensitivity of the radio direction finder, i.e., the field

strength which is required to ensure possibility of direction finding with error

not exceeding a given value. For this, there Is determined that voltage from the

generator of standard signals at which bearing is read with the given accuracy. Prom

the voltage field strength Is calculated.

2. Check of exactness of determination of direction. Switching on the direction

finder, we find field strength E1 and Eg in two positions, corresponding to deter-

mination of the direction, with constant output voltage. Depending on the scheme

for determining direction these positions can be established either in the receiver

itself by turning the variometer, switch, and so forth, or by turning the loop. In

the last case in the test circuit turn of the loop Is replaced by turn of variometer t " EJ

L 2-L 2 from the position corresponding to »ftL to position -R--«» Relation •**

characterizes exactness of determination of direction.

5, Check of compensation for antenna effects. The problem is to determine the

relative emf of the antenna effect which can be compensated. It, obviously, is equal

to the maximum emf created by the compensator. To determine this value we determine

field strength E0, creating normal output voltage with the position of the compen- i "

sator, corresponding to zero emf of compensation. Then we turn variometer L «-L 2

until we obtain zero emf in the loop circuit and the place compensator in the

position, giving maximum compensation emf. In this position we again determine field EQ

strength E , giving the same output voltage. Ratio ■ ■ gives the value we Q{mr comp sought.

-3-

k. It It poialblt to chtek rwulnlng eharaotarlstlei of th« roctlvtr

(••loctlvlty, fidelity, and so forth),

Toitlng by th« tvo-algnal aethod li Meoapllthod with two •qulvaltnts, whos«

inputs aro eonnoetod to two ganaratori# and outputs ars parallsl-connaoted.

Raaistancaa and raaetanoas of th« «qulvalant should b« doubled.

Another asthod of laboratory testing consists of placing the loop In a magnetic

field, which Is created by current In a horizontal rectilinear wire (line) (Fig. 9.2).

This test should be conducted in a shielded chamber, since during tests with

the loop connected (and not with its equivalent, as in the preceding method) external

Interferences hamper tests a great deal. At a certain distance d from the chamber

celll! ; we stretch a rectilinear wire, which at one end le joined by a shielded

cable to the generator of standard signals, and on the other through resistance R

to the metal wall of the chamber.

•Ur

^

ii JiwuUMr iHMaurln^ UM

Matlv.p

loop

rtc

2 Shl«ld«d booth Fig. 9.2. Measuring line for testing a direction finder.

t» t«mlnU «r PM.lv.r "ranntet •nt.nn»"

Fig. 9.3. Voltage divider.

The purpose of resistance R is to

provide in the wire a traveling wave of

current. In traveling wave conditions current in wire, and, consequently, magnetic

field strength around it depends little on frequency. Magnetic field strength in

these conditions also does not depend strongly on shift of the observation point

along the wire.

Under wire there is placed the loop direction finder being tested. With

rotation of the loop the minimum emf is Induced in it at the time when its plane

is perpendicular to the wire.

Magnetic and electrostatic fields of a rectilinear wire at a small distance

from this wire do not have rs simple a relationship to one another as in the zone

of radiation. Therefore, use of the open antenna of a direction finder in its

normal position can lead to a relationship of emf's induced in the antenna and loop,

absolutely different from the relationship in real conditions. For testing it is

necessary to use as the antenna a special section of rectilinear conductor, located

in parallels to the test line. The length and distance of this conductor from the

-4-

lint will be ielectad in luoh a way ai to ensure a nomal relationship of emf »s In

the antenna and loop. For feed of the antenna circuit It Is also possible to use a

voltage divider (Pig, 9.3).

First of all It is necessary to select such a reslntance R that In the line

there Is established a traveling wave« Wave Impedance of a single-wire line with

diameter 2r at distance d from the conducting plane in equal to

f-iaiii^. (9.i)

By this formula there can be found the approximate value of resistance R - p.

Traveling wave conditions In the line are verified by one of the known methods. In

this case It Is convenient to use the fact that impedance of a line, loaded on wave

Impedance, Is equal to the wave Impedance, Due to this, connection to the generator

of standard signals of a line, loaded on resistance R, If R pf will Influence the

generator the same as connection of the actual resistance R (will cause the same

decrease of Its output current). By several tests It Is possible to deflnitlze

magnitude R, Initially found by the formula (9,1). Traveling wave conditions must

be verified In the whole range of frequencies of the direction finder.

Line calibration, i.e., determination of the field strength corresponding to

the given output voltage of the generator. Is produced by a comparator. The antenna

of the comparator should be loop-type and of approximately the same dimensions as

the loop of the direction finder.

If generator voltage is U, and field strength Is E, then k . '* ff ls called the

scaling factor, determination of which Is the purpose of calibration.

Calibration should be performed at several frequencies within the frequency

range of the direction finder. Independence of the scaling factor from frequency

Is confirmation of the fact that In the line there have been established traveling

wave conditions.

If Is necessary also to produce calibration for different distances of the

center of the loop from the line.

If there Is no comparator, calibration can be produced by a loop, whose

geometric dimensions are known exactly. Die erf on terminals of the loop should be

measured by a voltmeter with a very large Input Impedance. As such voltmeter we use

receiver with supply of voltage to the cathode grid of the first tube. The receiver

is calibrated from a generator of standard signals.

-5-

If maxlBxn «mf in the loop !• Emaxi «nd voltag« fron the generator le U,

*.-%• (9.2)

where ha li the calculated effective height of the loop.

For eeleetion of an auxiliary antenna or ipeclflcationi of the divider feeding

the antenna circuit, we ehould know the effective height of the open antenna of the

direction finder h^.

The emf introduced into the antenna circuit of the direction finder in real

conditions is equal to

^e-E*..

When testing under a line with the help of a divider this emf is equal to

Prom this we find

C B

The sum of capacitances C. + C« should be equal to the capacitance of the antenna

C . Formula (9*3) gives the possibility of determining C, and Cp»

•Ca-C.Mr.. i9tk)

4—CtCl-MnJ. (9-3)

Testing under a line permits determining the same parameters of a direction

finder as testing with the help of an equivalent antenna. Furthermore« testing

under a line permits checking the sharpness of minima and the magnitude of errors

depending upon frequency, field strength and other factors.

For checking selectivity by the two-signal method there is stretched a second

line, perpendicular to the first and fed by a separate generator. Frequency and

field strength of the disturbing radio station are established on this second

generator.

It is necessary to note that neither the first nor the second method of

laboratory testing corresponds fully to real conditions of work and, therefore, they

can give results, differing from results of tests in operational conditions.

Nonetheless, laboratory tests are very desirable, since thanks to the easy of shifting

frequency, change of amplitude of the fed voltage, etc., tests can be conducted more

widely and deeply than during tests on real work. Here, there can be revealed defects

which would be passed over during performance tests.

-6-

Of the two methods described, obviously, the second corresponds more closely

to real conditions of work of the direction finder, but carrying It out is somewhat

more complicated than for the first.

9.2, Laboratory Tests of Direction Finders of a Qoniowetrlc System

Tests of Loops

Besides normal checking (determination of inductance, self-capacitance, damping,

and so forth) for loops of gonlometric systems it is very important to check the

magnitude of mutual inductance between them. Absence of mutual inductance simulta-

neously confirms their mutual perpendicularity. From smallness of permissible

magnitude of mutual inductance (permissible coupling coefficient is of the order of

0.2-0.4£) normal bridge and resonance methods are insufficiently exact.

A measuring circuit, permitting a reading, with the required degree of accuracy,

Is presented in Fig. 9.4. B is a variometer with very small inductances of windings

(considerably smaller than inductance of loops), but with a fairly strong maximum

coupling between them (K - O.U to 0.6). The high coupling coefficient permits

sufficiently accurate calibration of the variometer.

One of the windings of the variometer, series-connected

with one of the loops, is fed from the generator; the

other winding of the variometer and the second loop are

also coupled In series and are Joined to the cathode

grid of the first tube of the receiver. Audibility on

the receiver output turns Into zero when the coefficient

of mutual inductance of the variometer is selected equal

to the coefficient of mutual inductance of the loops.

The generator and receiver, and also the variometer must be shielded, and all

wiring is carried out in such a way as to exclude spurious couplings between circuits

of the two loops.

Testing of the Ooniometer

In the goniometer all its electrical parameters — Inductances and distributed

capacitances of all colls and maximum coupling coefficient between each of the field

and the searcher coils — are to be checked. It is necessary also to check the

coefficient of mutual inductance between the two field coils. This measurement can

be made by the same scheme as analogous measurement for loops.

-7-

Fig. 9.4. Measuring circuit of small mutual inductance.

nit aoit Important ttit of a gonlootter Is dtttrmlnatlon of tht trror curvt.

Mftiurtmtnt of trro« can bt taktn at high and low froquonclti.

For checking at high frequency we compare the tested goniometer with a standard

one, connecting them as shown In Fig. 9.5. Let the rotor of the standard goniometer

turn about the first coll of the stator at angle

6a*a Assuming that the standard goniometer Is

absolutely exact we can present the emf's Induced

HwdM« IMI*I in stator colls In the form «llllMtt«P «nt«Mt«p

^.-y^cos*,. Fig. 9.5. Comparison of goniometer with a standard £, W TT^ sioI,. one.

where M^ — maximum mutual Induetancej

ZJ — Impedance of rotor of standard goniometer;

E — feed voltage.

Currents In stator colls will be

where Z +, Z , and Z g "" Impedances of stator colls of the standard and Investigated

goniometers.

Normally Impedances of two stator colls are equal to one another, i.e..

If the searcher of the tested goniometer Is turned an angle 0 , then the emf

Induced In It will be

where M- — maximum mutual Inductance between field and searcher colls of the tested 2 goniometer.

nils emf turns Into zero when 6 • 0 . + 90°. Thus, setting the rotor of the

standard goniometer at some angle € ., we should obtain disappearance of audibility

upon setting the rotor of the tested goniometer at an angle 0 + + 90°. The diffeience

between this angle and the angle of setting, at which we obtain real disappearance

of audibility, directly gives error of the goniometer. In an analogous way we can

test a goniometer with three or four field coils.

The circuit of other method of testing at high frequency is presented in Pig.

9.6. If we select resistance so that R^ « cjuLf, where Lf — Inductance of field coll,

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'

R^ — Impedance of the divider, voltage division depend! exclusively on the magnitude

of resistances. Thus, voltage on one of the field colls will be

and on the other field coll,

etc., where R^, ftp, ..., Rj. — resistance from beginning of divider to the corresponding

tap.

Analogously to the preceding we find the emf In the searcher coll, assuming the

goniometer Is free from errors. Thus, with coupling of field colls Into taps R. and

R, we obtain

where M — maximum mutual inductance of the field and searcher colls of the goniometer.

Ri The emf turns into zero when tan 6 R3

If the goniometer gives error, then disappearance of audibility will occur at

another angle 9. Error of the goniometer will be equal to

Thus, attaching the ends of field coils to varies terminals of the divider

and determining the position of the searcher corresponding to vanishing of audibility

in the telephone, we can determine the error of the goniometer at different angles.

It is possible to have a comparatively small number of taps in the divider (3-4), in

order to obtain sufficiently closely located points for construction of the error

curve.

Shielding of the generator, receiver, and divider, thoroughness of location of

wiring in this method are as necessary as in the method of a standard goniometer.

The divider itself should be made inductlonless and

non-capacltlve, possess a small skin effect, which is

necessary for preservation of constancy of the ratio

of resistances during change of frequency. One should

make it with the same care as, e.g., attenuators of

generators of standard signals.

nie circuit for checking a goniometer at low

frequency is shown in Pig. 9.7. In it R^ and R- -

Fig. 9.6. Testing a goniometer by a divider.

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prtoltion railitane« box«ij L^ and L2 - fltld colls of gonlomettri L, - Ita •archer coll| T - talaphona (low-railatanca).

The circuit la fad frca an af ganarator 0. Raalatancai R1 and R2 should ba

takan conaldarably larger than Induced resistance of field colls with frequency of

measurement cu, i.e., R^ » ul.1 and R2 » cuLg, In thla case currents I1 and I2 are

determined by equalities

Zf the goniometer was made absolutely exactly, the emf Induced In the searcher

coll would ba ?

Rotating the searcher coll until audibility disappears in the telephone, we

obtain angle 6 from equation

4mAfatate:4aAfeotl»0 or

*•-*&

If the goniometer has error, audibility will disappear at another angle $ -

6 + A, where A — degree of error. The method of checking consists In establishing

ratio «i conforming to angles 6 - 0°, 10°, 20°, etc., R2 and determining angle 9 at which sound disappears

in the telephone. Difference

#—arctg&sA

directly gives error of the goniometer. To each K

ratio Pig. 9»7« Circuit for checking of goniometer at low frequency. w- there correspond two angles differing

approximately by 180°, at which audibility vanishes.

TtiVM, the goniometer is checked from 0° to 90° and from 180° to 270°, To check the

second half of the dial the ends of one of the field coils are connected, which

corresponds to a change of sign in formula (9.6). During work it is necessary to

watch to see that the generator does not directly influence the searcher coil, and

that current in the telephone does not Influence the field coils.

Analogous circuits can be easily composed for testing multiwinding goniometers.

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'imwrater or

•tnndorü

Flg. 9*8. Diagram for checking syronetry of goniometer.

So that In the gonlometrlc system there Is no antenna effect, it Is necessary

to ensure complete symmetry of field colls of the direction finder. Check of

symmetry of the goniometer can be performed by the circuit In Fig. 9.8, Voltage

from the generator of standard signals Is brought to the field coll through a

symmetric transformer (see § 4.3) and a potentlometrlc circuit of resistances.

The searcher coil is connected to the receiver. In switch position A voltage

acts between ends of the field coll, which corresponds to reception of a two-phase

wave. In switch position B the emf acts between both ends of the field coil and the

"ground" (i.e., the frame of the goniometer, cathode of the first tube of the receiver

and its frame), which corresponds to reception of a single-phase wave. A completely

symmetric goniometer in the second switch position will not transmit voltage to the

searcher coll.

In practice measurement is performed In the following way. Setting the switch

in position A, tuning the receiver and turning the searcher coll to the position of

maximum coupling with the tested field coll, we regulate the voltage of the generator

of standard signals to obtain a conveniently read receiver

output voltage U, Let us assume that here the voltage of the

generator of standard signals is equal to E^,

Then we shift the switch to position B, Increase output

voltage of the generator of standard signals and turn the

searcher coll to obtain maximum receiver output voltage. Let

us assume that voltage of the generator of standard signal»,

necessary for production of the same receiver output voltage Ü, In this case Is equal

Pig. 9.9, Circuit of asymmetric loading.

to Eg. Then the relative degree of asymmetry of the goniometer is characterized by El ratio «r-, E2

In carrying out tests it is necessary to ensure symmetry of the transformer,

equality of potentials at points a and b, and also to avoid any asymmetry of the

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gonlooeter (for Initanet, becaus« of «syMMtrlc poiltlon of wlrtf to tht switch),

Ntatur«B«nt of aiymmetry by anothtr aothod Is earriod out with th« help of an

hf raslitano« brldgt, Aayametry la caustd by unequalnaaa of capacltlve or In

ganaral, any lapedancts batwaan tarmlnali 1 and 2 of load Zloftd (In this case tha

gonlonatar) and tha ground. In Fig, 9.9 thasa Inpadtncaa are designated Z and Z ,

The asynmetry pareaater Is equal to

Ve take three measurements of admlttencest

1) between point 1 and grounded point 2 (Y1)|

2) between grounded point 1 and point 2 (Y2)i

3) between short-circuited terminals 1 and 2 and ground (Y,))

r»- jft, » Y*mm-nr; Y*~ rf • It Is easy to see that

Both methods of measurement of asymmetry are applicable also to measurement

of asymmetry of the Input of the receiver and of other elements.

Test of a Radio Direction Finder as a Whole

To test a loop radio direction finder of a gonlometrlc system In laboratory

conditions there can be employed the seme two methods as for testing a direction

finders with a rotating loop« i.e., testing with an equivalent and testing with the

help of a line. The equivalent presented In Fig. 9*1 gives the possibility of feeding

emf only to one of the field coils. The remaining field coils of the goniometer

should be closed to the same equivalents with closed input terminals.

When testing by the two-signal method there can be uaed a second field coil,

to which there is fed an emf from a second generator through an antenna equivalent, '

In the case of an external system of two spaced antennas it is also possible

to compose an equivalent. Its circuit is presented in Fig. 9.10. Here Ca, Cfd, C,

Cfalr — capacitances of apaced antennas« feeder, auxiliary antenna and its fair^-lead;

L and L. — inductances of the auxiliary and the spaced antennas. Selection of

magnitudes R, R. and M is analogous to the preceding case. It should be stressed

that testing by an equivalent has meaning only for those systems, for which natural

waves of antennas considerably differ fron working waves.

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ft—J—l*—_<* 9.5« Laboratory Ttita of R>dlo Direction Finders with Wldt An-

tenna Spacing "^"^

Pig. 9.10. Circuit of the equivalent for a system of speed antennas.

Separate component parts of the radio direction

finder (hf transformers« time delay line, switching

circuits. Indicators# etc.) are checked by usual

methods•

The antenna system of a radio direction finder

with wide spacing antennas consists of a large

number of antennas. In which there are induced emf's of Identical smplitu'io, bun v/J th

different phases in accordance with geometric location of the antennas (§ 3,11).

Antennas are connected to an antenna switch or a

reception-indicator.

During laboratory tests of a radio direction

finder it is necessary to be able to introduce to

Inputs of the antenna switch (or reception-Indicator)

voltage of identical amplitude, the phase of which

varies by a given law. For this there Is used a

special antenna equivalent. In Fig. 9.11 there Is

presented the circuit of the equivalent for labora-

tory testing of a radio direction finder with a

circular antenna system. It consists of a natural

or artificial long line, fed by a generator of

standard signals and loaded on an impedance, equal

to wave impedance. The section of long line is

designed In such a manner that on terminals of the long line of the equivalent a, b,

c, etc., voltages have identical amplitudes and phases, equal to phases of the emf

of corresponding antennas.

Phases of voltages are calculated for the case when there is produced reception

of a radio station from a definite direction.

Between terminals of the long line and the ground there are coupled resistance

R^-Rg such magnitude that R^ » R2 and Rg - pfd, - where pfd wave impedance of

feeders leading into the antenna switch (matched loading of feedars from the antennas

is assumed).

Fig, 9.11. Circuit of the equivalent of a circular antenna system with wide spacing.

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Thui, on the output terminals of the tqulvalent i, 2, }, ..,, n there ere voltegee

of Identical eaplltude with phaeee, corresponding to pheees of emf antennes. Output

reslstancee on these terminals are equal to pfd. Application of decoupling

resistances R^ removes Influence of loads of the antenna switch on the amplitude

and phase of voltagee at points 1, 2, "}, .,., n.

The antenna equivalent permits cheeking the overall efficiency of equipment,

determining instrument accuracy for fixed directions and sensitivity. Instrument

accuracy le determined connecting the output of the equivalent 1« 2, 3« ..., n first

to terminals 1 , 2 , 3 , ..., n of ths antenna switch. Here« on the antenna ewitch

during direction finding there should be read an angle, corresponding to that bearing,

for which the long line is calculated. Then the output of equivalent 1, 2, 2, ..., n

are switched to terminals 2,3«***«n,l of the antenna switch, 3,4, ..., n ,

1,2, etc. Each switching corresponds to displacement of the direction of bearing

an angle, equal to the angle between the antennas. The difference between readings

on the bearing Indicator of the radio direction finder and calculated bearings

corresponds to Instrument errore. To determine sensitivity it is necessary to

preliminarily find coefficient k of transmission of voltage from input terminals of

the equivalent to its output terminals 1, 2, 3, ..., n with connected loads.

If to the equivalent's input there is fed voltage U, then E IA. ' , where h **

is the effective height of the antenna.

With an unmatched loading of feeders Instead of pfd it is necessary to couple

in at each frequency its own Z , corresponding to input Impedance of the antenna

and feeder together.

By this method we also determine the directivity pattern of the antenna system.

9,4. Tests of Direction Finders in Real Conditions of Work

When testing a direction finder In the place of installation it is necessary to

check separate parts of the antenna-feeder device (single angennas, feeders, etc.)

and correctness of their geometric location. Tests are performed by methods,

described in [9*3]•

Tests of a radio direction finder have the goal of determining! Instrument

error of the direction finder, magnitude and nature of local errors, general accuracy

of the direction finder, general sensitivity of the direction finder, the character-

istic and coefficient of directivity of its antenna system.

-14-

Dtterminlng Instrument Error of a Radio Direction Finder

It If not possible to determine Instrument error for all systems of direction

finders. Thus, direct determination of Instrument errors for 'Uroctlon finders with

a fixed outdoor system Is Impossible, If the latter Is too bulky. In these cases It

Is necessary to be limited to analysis < f separate sources of Instrument error on

the basis of laboratory tests and tests, which are described In the following point.

Instrument error Is most exactly and simply determined for gonlometrlc direction

finders, for which structure and dimensions of the outdoor equipment are such as

permit rotation of It In the process of testing. For this purpose the external

device of the direction finder Is set on a special machine, permitting us to turn It

at known angles. Tuning to some station, by rotation of the goniometer we find its

bearing. We then turn the outdoor system a certain angle (for Instance, 10-15°) and

repeat fixing. The new reading on the goniometer should differ from the first by

the angle of rotation of the outdoor system. Performing such tests for several

angles from 0° to 360° and at various frequencies, we can obtain a sufficiently full

Judgement of Instrument accuracy of the direction finder.

Special difficulties are presented by tests of direction finders with calculation

of polarization errors. Thus, to determine standard polarization error one should

place the direction finder In an electromagnetic field with a known slope of the wave

front and angle of polarization. For creation of such a field a local generator Is

placed at a considerable height (on a mast, ballon, etc.) and Is equipped with a

radiating dlpole, which la set at such an angle as creates a field with the necessary

turn of the plane of polarization.

Distance from the direction finder to the generator should be sufficiently great.

For direction finders of short waves this distance Is practically of the order of

100 m or more. To create an angle of Incidence of 450# corresponding to conditions

of test of the error of a standard wave, height of lift of the generator should also

be near 100 m. This causes evident practical difficulties, because of which In most

cases we are limited to smaller height of rise of the emitter. So that p .arlzatlon

error is not small, the angle of rotation of the plane of polarization 7 is made

greater than 45°.

If the sngle of inclination of the wave front is very small, to satisfy the

shown condition angle 7 should be close to 90 • Inconvenience of such a condition

of tests is the small magnitude of the vertical component of field strength and,

consequently, the weak reception power,

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