Andrew 174100 Installation and Maintenance Manual

INSTALLATION AND MAINTENANCE MANUAL

for

MODEL 174100

ASR 11 S-BAND ANTENNA

MANUAL No. 79680

REVISION AD

22 October 2003

ANDREW CANADA INC.

606 BEECH STREET, WHITBY

ONTARIO, CANADA

L1N 552

79680.AD.DOC

2

LIST OF EFFECTIVE PAGES

Dates of original issue and revisions are:

Original ........... A........... 26 January 1997

Revision .......... B .......... 19 February 1998

Revision .......... C ........... 9 March 1998

Revision .......... D........... 28 May 1998

Revision ......... F ........... 19 JUNE 1998

Revision ......... F ........... 16 JULY 1998

Revision .......... G .......... 9 NOVEMBER 1998

Revision .......... H........... 01 DECEMBER 1998

Revision ......... J ............ 23 DECEMBER 1998

Revision .......... K........... 13 APRIL 1999

Revision .......... L ........... 04 JUNE 1999

Revision .......... M .......... 13 OCTOBER 1999

Revision ......... N........... 05 JANUARY 2000

Revision .......... P ........... 24 MARCH 2000

Revision .......... R ........... 30 JANUARY 2001

Revision .......... T ........... 26 FEBRUARY 2001

Revision ......... U........... 04 OCTOBER 2001

Revision .......... V........... 21 MAY 2002

Revision .......... W .......... 29 JULY 2002

Revision ......... Y........... 15 JAN 2003

Revision .......... Z. .......... 30 APRIL 2003

Revision .......... AA. ....... 14 MAY 2003

Revision ......... AB ........ 05 AUGUST 2003

Revision .......... AC ........ 07 October 2003

Revision .......... AD ........ 22 October 2003

PAGE REVISION

Title Page AD

List of Effective Pages AD

Safety Summary AD

Table of Contents AD

Section 1 - General Description and Theory of Operation AD

Section 2 - Equipment Receipt, Unpacking and Lifting AD

Section 3 - Installation Procedures AD

Section 4 - Maintenance AD

Section 5 - Other Equipment AD

Section 6 - Optional Equipment AD

3

SAFETY SUMMARY

GENERAL:

READ THE INSTRUCTION THOROUGHLY BEFORE ASSEMBLY. FOLLOW THE

SEQUENCES FOR PROPER. ASSEMBLY AND OPERATION.

NOTICE:

THE INSTALLATION, MAINTENANCE OR REMOVAL OF THE ANTENNA REQUIRES

QUALIFIED, EXPERIENCED PERSONNEL. ANDREW INSTALLATION INSTRUCTIONS HAVE

BEEN WRITTEN AND ILLUSTRATED FOR SUCH INSTALLATION PERSONNEL. THIS SYSTEM

SHOULD BE INSPECTED ONCE A YEAR BY QUALIFIED PERSONNEL TO VERIFY PROPER

INSTALLATION, MAINTENANCE AND CONDITION OF EQUIPMENT. ANDREW DISCLAIMS

ANY LIABILITY OR RESPONSIBILITY FOR THE RESULTS OF IMPROPER OR UNSAFE

INSTALLATION OR MAINTENANCE PRACTICES.

220 VAC, THREE PHASE POWER IS USED IN THE OPERATION OF THIS EQUIPMENT THAT IS

DANGEROUS AND MAY BE FATAL IF CONTACTED BY PERSONNEL. EXTREME CAUTION

SHOULD BE EXERCISED WHEN WORKING WITH THIS EQUIPMENT. WHILE EVERY

PRACTICABLE SAFETY PRECAUTION HAS BEEN INCORPORATED IN THIS EQUIPMENT, THE

FOLLOWING RULES MUST BE STRICTLY OBSERVED.

KEEP AWAY FROM LIVE CIRCUITS:

Operators and maintenance personnel must at all times observe safety regulations. Do not change plug-in

components or make adjustments inside the equipment with high voltage supply on. Under certain conditions

dangerous potentials may exist in circuits with the power control in the OFF position due to charges retained

by capacitors. To avoid casualties always remove power, then discharge and ground by use of a ground rod,

prior to touching any parts.

- Do not remove covers or access plates on the equipment unless you are authorized to do so.

- Do not work on electronic equipment unless there is another person nearby who is familiar with the

operation of the equipment and is trained in administering first aid.

- To prevent electrical shock or damage to the equipment, do not operate it until you thoroughly understand the

operation and function of all controls, indicators and connectors.

4

FIRST AID

In case of electrical shock:

 Do not try to pull or grab the individual.

 If possible, turn off the electrical power.

 If you cannot turn off the electrical power, pull, push, or lift the person to safety using a dry wooden pole, a

dry rope, or some other insulating material.

 Send for help as soon as possible.

 After the injured person is no longer in contact with the source of electrical shock, move the person a short

distance away and immediately administer first aid and artificial resuscitation as required.

5

TABLE OF CONTENTS

Paragraph Title Page

1 General Description and Theory of Operation................................................................ 9

1.1 Scope .............................................................................................................................. 9

1.2 Purpose of Equipment ..................................................................................................... 9

1.3 Equipment Supplied ........................................................................................................ 9

1.4 Physical Description ...................................................................................................... 9

1.4.1 Antenna ........................................................................................................................... 9

1.5 Functional Description .................................................................................................. 10

1.5.1 Antenna Unit ................................................................................................................. 10

1.5.1.1 Reflector ....................................................................................................................... 10

1.5.1.2 Dual Feed Assembly ..................................................................................................... 10

1.5.2 Polarization and Beamswitch Box ................................................................................ 10

1.6 Theory of Operation ..................................................................................................... 11

1.6.1 Dual Feed Assembly ..................................................................................................... 11

1.6.2 Reflector ....................................................................................................................... 11

1.6.3 Detailed Circuit Analysis .............................................................................................. 11

1.6.3.1 Antenna Unit ................................................................................................................. 11

1.6.3.2 Azimuth Antenna Pattern ............................................................................................. 12

1.6.3.3 Elevation Patterns ......................................................................................................... 12

1.63.4 Other Antenna Specifications ....................................................................................... 12

1.6.3.5 Antenna Reflector ......................................................................................................... 12

1.6.3.6 Reflector Mounting and Tilt Adjustment ...................................................................... 13

1.6.4 Dual Feed Assembly ..................................................................................................... 13

1.6.4.1 Feed Assembly.............................................................................................................. 13

1.6.4.2 Circular Polarization Generation .................................................................................. 13

1.6.4.3 Transmitting Circularly Polarized Signals .................................................................... 14

1.6.4.4 Receiving Circularly Polarized Signals ........................................................................ 14

1.6.4.5 Transmitting and Receiving Linearly Polarized Signals .............................................. 15

1.6.4.6 Feedhorn Assembly ...................................................................................................... 15

1.6.4.7 Polarizer/Feed Assembly Mechanical Operation.......................................................... 15

6

2 Equipment Receipt, Unpacking and Lifting................................................................. 21

2.1 Receipt ......................................................................................................................... 21

2.2 Unpacking .................................................................................................................... 21

2.3 Lifting .......................................................................................................................... 24

3 Installation Procedures ................................................................................................. 25

3.1 Introduction .................................................................................................................. 25

3.1.1 Overview ...................................................................................................................... 25

3.1.2 Recommended System Assembly Tool List ................................................................ 27

3.2 Standard Torque Values for Assembly ........................................................................ 29

3.3 Summary of Installation Sequence .............................................................................. 30

3.3.1 Installing the Base Interface Kit ................................................................................... 31

3.3.2 Installing the Fixed Feeds Unit to the Reflector Base .................................................. 34

3.3.3 Installing the Ladder Kit .............................................................................................. 36

3.3.3.1 Access Ladder General Climbing Procedure ............................................................... 40

3.3.4 Installing the PSR/SSR Interface Mount ..................................................................... 43

3.3.4.1 Installing the SSR Tilt Scale Bracket ........................................................................... 44

3.3.5 Lifting the Assembly .................................................................................................... 46

3.3.6 Leveling the Antenna Assembly .................................................................................. 50

3.3.7 Installing the Polarization and Beamswitch Control Box ............................................ 51

3.3.8 Installing the AC Junction Box .................................................................................... 51

3.3.9 Adjusting the Antenna Azimuth .................................................................................. 51

3.3.10 Installing the Waveguide ............................................................................................. 51

3.3.11 Installing the Coaxial and Electrical Cables ................................................................ 56

33.11.1 PSR Coaxial and Electrical Cables .............................................................................. 57

3.3.11.2 SSR Coaxial Cables ..................................................................................................... 59

3.3.11.3 Grounding Cable .......................................................................................................... 59

33.12 Performing Final Readiness Check .............................................................................. 62

33.12.1 Antenna Feedhorn Alignment Check, ......................................................................... 62

3.3.12.2 Contour Damage Check ............................................................................................... 63

3.3.13 Installing the Feed Counterweights to the Fixed Feeds Unit.. ..................................... 64

33.14 Installing the Antenna Counterweights ........................................................................ 64

4 Maintenance ................................................................................................................. 68

4.1 General Procedures ...................................................................................................... 68

4.1.1 Maintenance Precautions ............................................................................................. 68

4.1.2 Standard Maintenance Procedures ............................................................................... 69

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4.2 Preventive Maintenance ............................................................................................... 70

4.3 Disassembly Procedures ............................................................................................... 72

4.3.1 Disassembly of the Dual Feed Assembly ..................................................................... 72

4.3.2 Polarization and Beamswitch Control Box (174170)

Removal and Replacement Procedure .......................................................................... 74

4.3.3 Removal and Replacement of Antenna Ladder Slides ............................................... 74d

5 Other Equipment ........................................................................................................... 79

5.1 Test Antenna Kit ........................................................................................................... 79

6 Optional Equipment ...................................................................................................... 82

6.1 Obstruction Lighting Kit .............................................................................................. 82

6.2 Radome Kit ................................................................................................................... 84

LIST OF TABLES

Table Title Page

2-1 Weights of Major Antenna Components ................................................................................. 24

3-1 Installation Kit (174225) ......................................................................................................... 26

3-2 Shipping and Support Stand Kit .............................................................................................. 27

3-3 Installation Equipment ............................................................................................................. 27

3-4 Standard Torque Values for Assembly .................................................................................... 29

3-5 Base Interface Kit Materials (174198) ................................................................................... 32

3-6 Fixed Feeds Unit-to-Reflector Base Installation Materials ..................................................... 34

3-7 Ladder Kit Installation Materials (174180) ............................................................................. 36

3-8 PSR/SSR Interface Mount and Tilt Scale Bracket Installation Materials ................................ 43

3-9 Antenna Lift Kit Installation Materials (174245) .................................................................... 46

3-10 Rotary Joint-to-Dual Feed Waveguide Installation Materials (174247) .................................. 52

3-11 Coaxial and Electrical Cable Installation Materials ................................................................ 56

3-12 Telescope Mounting Installation Materials ............................................................................. 62

4-1 Common Support Equipment .................................................................................................. 69

4-2 Line Replaceable Units (LW) and ........................................................................................... 78

Preventative and Corrective Maintenance Kits

5-1 Test Antenna Kit ...................................................................................................................... 79

6-1 Obstruction Lighting Kit ......................................................................................................... 82

6-2 Radome Kit .............................................................................................................................. 84

*

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LIST OF ILLUSTRATIONS

Figure Title Page

1-1 Typical Antenna Pattern, Azimuth .......................................................................................... 17

1-2 Typical Antenna Pattern, Elevation ......................................................................................... 18

1-3 Polarizer Schematic ................................................................................................................. 19

1-4 Antenna Schematic Diagram ................................................................................................... 20

3-1 Complete Antenna Installation ................................................................................................ 22

3-2 Shipping and Support Stand .................................................................................................... 23

3-3 Base Interface-PSR Base Assembly ........................................................................................ 33

3-4 Fixed Feeds Unit Installation ................................................................................................... 35

3-5 Ladder Kit Installation ............................................................................................................. 42

3-6 PSR/SSR Interface Mount Installation .................................................................................... 45

3-7 Antenna Lift Kit Installation .................................................................................................... 49

3-8 Waveguide Installation ............................................................................................................ 54

3-9 Waveguide Hanger Installation ............................................................................................... 55

3-10 Coaxial and Electrical Cable Installation ................................................................................ 60

Polarization and Beamswitch Control Box Installation ........................................................... 60

AC Junction Box Installation................................................................................................... 60

3-11 SSR Coaxial Cable and Tilt Scale Bracket Installation ........................................................... 61

3-12 Antenna Feedhorn and Tilt Alignment and Contour Check .................................................... 65

3-13 Antenna Azimuth Alignment ................................................................................................... 66

3-14 Counterweight Installation....................................................................................................... 67

4a Polarization and Beamswitch Control Box Location on Antenna ........................................... 74

4b Polarization and Beamswitch Control Box Close Up ............................................................ 74b

4c Lower Antenna Ladder Slide ................................................................................................ 74f

4-1 Polarizer ................................................................................................................................... 76

4-2 Polarizer Motor Replacement .................................................................................................. 77

5-1 Test Antenna Kit ...................................................................................................................... 81

6-1 Obstruction Lighting Kit ......................................................................................................... 83

*

9

SECTION 1

1. GENERAL DESCRIPTION and THEORY OF OPERATION

1.1 SCOPE

This instruction book contains theory of operation and information for the installation, operation and

maintenance of the Primary Surveillance Radar S-Band Antenna (ASR 11).

1.2 PURPOSE OF EQUIPMENT

The S-Band reflector type antenna, called the Primary Surveillance Radar (PSR) Antenna is used in

transmitting and receiving RF energy for Air Traffic control and for supporting a Large Vertical

Aperture (LVA) Secondary Surveillance Radar (SSR) Antenna.

1.3 EQUIPMENT SUPPLIED

The antenna assembly consists of the equipment, subassemblies and kits listed in Table 3-1. Figure

3-1 shows the complete Antenna assembly.

1.4 PHYSICAL DESCRIPTION

The antenna assembly uses materials, coatings and finishes inherently resistant to corrosive

environment. Intended as the strongest link in the radar system, the antenna requires minimum

maintenance. It is designed to facilitate removal and replacement of any faulty portion except the

reflector and pedestal with equipment furnished as part of the system.

1.4.1 Antenna

The antenna unit, having no standby assembly, is designed to be highly reliable and capable of

withstanding adverse weather conditions. Aluminum construction is used throughout, except the

base, feed support, horn radomes, etc., that require other materials. Special paints are used to give the

assembly maximum life, even in regions where air is heavily polluted.

10

1.5 FUNCTIONAL DESCRIPTION

The antenna radiates a beam 1.5 degrees in azimuth and shaped in elevation to produce coverage up

to approximately 32 degrees above the horizon to provide a map-type presentation of aircraft within

55 nautical miles of the airport terminal. Major assemblies of the antenna are described in the

following paragraphs. This section gives only a brief description of the function performed by each

without regard to functional operation. A detailed analysis of functional operation is contained in

Section 1.6, Theory of Operation.

1.5.1 Antenna Unit

The antenna unit consists of Reflector, Dual Feed Assembly, interconnecting waveguide, cables and

wires. The antenna produces a rotating antenna pattern having a 1.5 degree azimuth beamwidth and a

shaped elevation pattern allowing radar coverage up to 32 degrees above the horizon. Polarization of

the radiated energy can be remotely switched to either linear or circular polarization. Special

equipment includes a test antenna and a telescope used to check antenna alignment.

1.5.1.1 Reflector

The reflector has a modified parabolic shape designed to produce an approximately cosecant-squared

beam in the elevation plane. The reflecting surface, covered with expanded aluminum screen, is 16.1

feet wide and 9 feet high. The horizontal and vertical contour plates are fabricated using numerically

controlled equipment to ensure the required high degree of accuracy. Wind loads are transferred to

the reflector support through the base of the reflector and the back structure which consists of welded

aluminum tubes and channels.

1.5.1.2 Dual Feed Assembly

The dual feed assembly includes two identical polarizer/feed assemblies. Each polarizer/feed

assembly contains a square waveguide section with the necessary motor and gearing to generate

either linear or circular polarization as selected by the radar operator. The antenna feedhorn, which

mounts on the polarizer, provides impedance matching between the waveguide system and free

space, and produces the desired feed pattern to illuminate the reflector. A radome over the horn

aperture excludes moisture and foreign matter, and provides a pressure seal.

1.5.2 Polarization and Beamswitch Control Box

The Control Box mounted on the feed support provides for interconnection between the antenna unit

and the Rotary Joint connections.

11

1.6 THEORY OF OPERATION

The theory of operation for the antenna contains theory of operation for microwave and electronic

circuits and provides detailed circuit descriptions explaining circuit arrangements in the order of

operational or signal sequence. Functional operation of mechanical assemblies is provided as needed

and as related to electronic circuits and system operation.

1.6.1 Dual Feed Assembly

The dual feed assembly allows remote selection of linear or circular polarization and provides two

secondary antenna patterns displaced approximately 3.5 degrees in the elevation plane. (Secondary

patterns are those produced by the reflector, using primary patterns produced by the feedhorns.)

Under normal operating conditions linear polarization of the radiated signal will be used since it

provides higher level target returns. Under inclement weather conditions circular polarization can be

selected to reduce the radar sensitivity to clouds and precipitation.

Both feeds in this assembly are identical in construction. The normal or active feed (Low Beam) is

located above the passive feed (High Beam) to produce a secondary active beam directed more

toward the ground than the passive beam. The transmitted signal is radiated by this lower beam.

During the high ground clutter return period, the first 10 or 15 nautical miles, signals from the upper

beam (lower feed) are coupled to the receiver by means of a beam select switch located in the

receiver. This arrangement reduces the ground level returns without reducing returns from targets at

higher elevation angles.

1.6.2 Reflector

The reflector focuses RF energy to provide beams approximately 1.5 degrees in azimuth and shaped

in elevation to produce coverage up to approximately 32 degrees. The reflector surface has a circular

opening at the center for mounting a test antenna. The top of the reflector has provision for

supporting an LVA SSR antenna.

1.6.3 Detailed Circuit Analysis

1.6.3.1 Antenna Unit

The antenna, rotating at a rate of 12.5 r/min, scans an area with a radius of 55 nautical miles, using

two beams approximately 1.5 degrees in azimuth with shaped elevation patterns to provide coverage

up to 32 degrees. By selecting returns from the higher beam during the first part of the receive

period, ground clutter is reduced while good sensitivity is maintained for the rest of the coverage

volume. Each subassembly is discussed in the following paragraphs.

12

1.6.3.2 Azimuth Antenna Pattern - (See Figure 1-1 for Typical Azimuth Pattern.)

In the principal azimuth plane the antenna has a minimum azimuth beamwidth of 1.35 degrees at the

-3 dB power point and a maximum beamwidth at the -20 dB power point of 4 degrees; sidelobe level

is -24 dB for the Lowbeam and -22 dB for the Highbeam. For the Lowbeam at 30 degrees above the

elevation peak of the beam, the -3 d13 beamwidth is 1.35 degrees minimum and 5.5 degrees

maximum at the -15 dB power point; the maximum azimuth sidelobe level is -16 dB. For the

Highbeam at 28 degrees above the peak of the beam, the -3 dB beamwidth is 1.35 degrees minimum

and 6 degrees maximum at the -15 dB power point; the maximum sidelobe level is -15 dB. At a point

on the ground side of the peak of the passive pattern that is 20 dB below the maximum power point,

the -3 dB azimuth beamwidth is 1.1 degrees minimum and 3 degrees maximum at the -10 dB power

point. The maximum backlobe power level is -32 c113 for both beams at all elevation angles.

1.6.3.3 Elevation Patterns - (See Figure 1-2 for Typical Elevation Pattern.)

The elevation patterns have a 4.8 degree minimum -3 dB beamwidth and approximately a cosecant

squared power pattern up to 30 degrees above the peak of the normal pattern and 28 degrees above

the passive pattern. On the ground side of the peak-of-beam the pattern is down more than 20 dB

relative to the peak power point of each respective pattern at an angle of 4.1 degrees (active) and 5.1

degrees (passive) below the lower -3 dB elevation pattern power point With the antenna set so that it

is horizontal mechanically, the peak of the normal and passive beams are at approximately 2.0 and

5.7 degrees respectively. The two values will vary slightly from antenna to antenna.

1.6.3.4 Other Antenna Specifications

The peak-of-beam antenna gain is 33.5 d13 (Lowbeam) and 32.5 (Highbeam) above an isotropic

source. The principal elevation and azimuth plane ICR (rain clutter rejection) is 22 dB minimum.

The input VSWR of each feed is better than 1.3:1 over the entire operating frequency range of 2700

to 2900 MHz. The antenna is capable of operating in winds up to 85 knots and will withstand winds

up to 130 knots non-operational.

1.6.3.5 Antenna Reflector

The reflector is formed by contour plates riveted together to form a support structure onto which a

reflecting surface of expanded aluminum is welded. The basic accuracy of the reflecting surface is

determined by the contour plates which are fabricated by numerically controlled machines. A welded

backstructure, consisting of aluminum tubes and channels, aids in transferring windloads into the

reflector support. A section of screen in the center of the reflector is removable so a test antenna can

be mounted to check electrical characteristics of the dual feed. Three discs attached to the reflector

form targets used to check feed location. The top of the reflector forms a mounting pad for the LVA

SSR antenna.

13

1.6.3.6 Reflector Mounting and Tilt Adjustment

The reflector is mounted directly on the reflector support which is attached to the pedestal by two

hinged joints and two elevation tilt screws. The dual feed assembly with its associated waveguide

and related hardware is supported on a feed support which is mounted to the antenna base, causing

both the reflector and the dual feed assembly to tilt as necessary to achieve the desired elevation tilt

angle for the rotating beam. Adjusting the tilt screw is a manual operation, requiring only a few

minutes at the antenna platform. Antenna tilt is adjustable so that the peak of the main beam can be

set at any angle between 3.0 degrees below and 5.0 degrees above the horizontal. A pointer and

scale, marked in increments of 0.1 degree, indicate the elevation angle of the beam peak to an

accuracy of 0.2 degrees at the center of the frequency band. If an accuracy better than 0.2 degrees is

required, the use of an inclinometer is recommended for a more accurate reading of antenna tilt

adjustment. A tilt instruction plate mounted on the reflector support near the tilt screw provides

antenna tilt correction data as a function of frequency.

1.6.4 Dual Feed Assembly

Dual feed assembly (Figure 3-4) consists of two identical polarizer assemblies, transducers,

transitions to type >N=, two feedhorns, two radomes, and associated supporting hardware. Both

feeds are held in place by a mounting frame. Feed positioning is established during pattern testing

by Andrew. After positioning, locating pins are installed to permit proper realignment if field

disassembly/reassembly of the feed assembly is required. The dual feed assembly is attached to the

feed support arm of the reflector support by three large diameter threaded rods. All but the top three

nuts, which are self-locking, are pinned after antenna test to ensure proper location of the dual feed

assembly. Removal of the top three nuts is required to remove the dual feed assembly.

1.6.4.1 Feed Assembly

Figure 3-4 shows the relative positions of the subassemblies in one feed assembly. These are a dual-

mode transducer, a phase-shift section, a feedhorn and a transition.

1.6.4.2. Circular Polarization Generation

To obtain a circularly polarized signal the linearly polarized input signal is split into two equal,

orthogonally polarized (polarized perpendicular to each other) components. One of the signals is

then shifted in time 90 degrees relative to the other. The phase-shift section (polarizer) provides the

differential 90-degree phase shift for circular polarization and 0-degree phase shift for linear

polarization. Phase-shifter orientation with respect to the transducer (approximately 45 degrees)

determines relative amplitude of orthogonally polarized signals.

14

1.6.43 Transmitting Circularly Polarized Signals

A linear vertically polarized signal enters the transducer vertical port. The signal then passes through

an impedance matching section in the transducer and enters the phase shift section. The phase shifter

is rotated approximately 45 degrees about the longitudinal axis of the waveguide run. At this point

the signal can be considered to consist of two orthogonally polarized signals, each polarized parallel

to the walls of the square waveguide. As the dielectric vanes are moved in the phase-shift section,

the phase of the E-field component perpendicular to the plane of the vanes is unchanged; however,

the orthogonal component is changed in phase. By positioning the dielectric vanes approximately 0.9

inches from the waveguide wall, a 90-degree phase differential is created between the two signals,

producing circular polarization. The circularly polarized signal passes through the feedhorn,

illuminating the reflector which forms the desired radiation pattern.

1.6.4.4 Receiving Circularly Polarized Signals

Returns resulting from precipitation are reverse-sense circularly polarized. They enter the polarizer,

pass through the phase-shift section, and enter the dual-mode transducer as horizontally polarized

signals. These signals are coupled through the dual-mode transducer horizontal port via a transition

to type >N= and a coaxial cable to a Beamswitch. The Beamswitch allows either the low beam or

high beam precipitation return to be lead to the weather channel of the antenna. Precipitation returns

are thus diverted from the regular return path. Desired returns are circularly polarized in the same

sense as the transmitted signal. They are converted to vertical polarization by the phase-shift section

and enter the dual-mode transducer vertical port. These signals then pass through connecting

waveguide to the receiver.

The above applies when the antenna is operated in the circular polarization mode. One of the features

of this antenna is that in the linear polarization mode (see Section 1.6.4.5) a small circular component

is also transmitted together with the vertically polarized signal. This small circularly polarized signal

is approximately 11 dB below the linearly polarized signal. It is used to provide weather channel

output (attenuated by 11dB) for linear mode operations.

15

1.6.4.5 Transmitting and Receiving Linearly Polarized Signals

To produce linear polarization, signals from the transmitter enter the dual-mode transducer vertical

port and the phase-shift section. In this case, however, the dielectric vanes are positioned

approximately 0.2 inches from the waveguide wall. Both orthogonal signal components receive

exactly the same phase shift. Since no differential phase shift exists between the orthogonal

components, the two signal components exit from the phase-shift section linearly polarized. The

signals pass through the feedhorn, illuminating the reflector and resulting in a linear vertically

polarized beam. As in circular polarization, desired returns pass from the reflector through the

feedhorn to the dual-mode transducer. Vertically polarized signal returns pass unchanged through the

phase-shift section and the waveguide run to the receiver. The antenna actually has a linear signal

with a small circular component (11db linear mode axial ratio). This is achieved by introducing a

small differential phase shift.

1.6.4.6 Feedhorn Assembly

The feedhorn attached to the active phase-shift assembly properly distributes the outgoing signal over

the antenna reflector for all polarizations. Both the Lowbeam and Highbeam horns collect signals

from targets. A radome over the mouth of the feedhorn provides an airtight seal without degradation

of signal strength.

1.6.4.7 Polarizer/Feed Assembly Mechanical Operation - Refer to Figures 1-3, 4-1 and 4-2

Two dielectric vanes inserted from one wall of the square waveguide section produce the phase shift

required for circular polarization. These vanes are moved to a position near the waveguide wall to

restore linear polarization. Proper limits of travel between maximum and minimum penetration are

set during calibration at the manufacturer=s test range and should not be disturbed elsewhere. Each

dielectric vane is supported by two dielectric rods that pass through matching clearance holes in the

square waveguide sidewall and are anchored in a single movable mounting plate. A button mounted

on an adjustable extension from the movable mounting plate serves as a bearing for the motor-driven

vane cam. This cam drives the movable mounting plate between its limits. Maximum depth of vane

insertion (circular polarization) is determined by the height of the button. The highest point of the

cam is a constant radius section to ensure proper vane penetration even if the cam does not stop in

exactly the same position every time. Minimum depth of vane insertion (linear polarization) is

determined by two adjustable screws that serve as stops for the movable mounting plate. In linear

position the button completely disengages from the cam and the mounting plate is spring loaded

against the linear stops. A second cam on the shaft operates four micro switches that control motor

operation and readback information.

16

1.6.4.7.1 A bearing pressed into the moving mounting plate travels up and down on a guide shaft

pressed into the waveguide housing. This ensures that the vanes do not tilt in the waveguide. A

guide cantilevered from the mounting plate rides on a post located under the motor to keep the

moving plate and vanes from rotating about the guide shaft, ensuring that the vanes are properly

oriented in the waveguide.

1.6.4.7.2 Figure 1-3 is a schematic diagram that includes both the normal polarizer (8A2A1) and the

passive polarizer (8A2A2), together with the interconnection provided by cables CA1 and CA2. The

circuit configuration is shown for circular polarization. The circular select signal (220 Volts AC)

applied at 8A2A1-.11-L and 8A2A2-J1-L has already driven both motors to the point at which the

switch cam removes power through switches 8A2A1-S4 and 8A2A2-S4. At the same time, status

ground (SG) signal at 8A2A1-J1-E and 8A2A2-J1-E is applied through switches 8A2A1-S2 and

8A2A2-S2 respectively to produce the Circular Status for Low-beam (CSL - for normal polarizer at

8A2AI-Jl-H) and the Circular Status for High-beam (CSH - for the passive polarizer at 8A2A2-J1-

H). At this time, the vanes are inserted at maximum depth in the square waveguide section and

operation is in the circular polarization mode as indicated at the system control panels.

1.6.4.7.3 If a linear select signal (220 Volts AC) is now applied at the polarizers both motors will run

once more and drive to the linear positions of the cams. When each polarizer reaches its preset

position, the switch cam will operate S3 to remove power from the motor and Si to complete the

readback circuit. Thus,

a. motor power will be removed from parallel-connected motor circuits;

b. status ground (SG) signal at 8A2A1-J1-E and 8A2A2-J1-E is applied through switches

8A2A1-S1 and 8A2A2-S1 respectively to produce the Linear Status for Lowbeam (LSL - for

normal polarization at 8A2A1-.11-F) and the Linear Status for Highbeam (LSH - for the

passive polarizer at 8A2A2-J1-F);

c. vanes will be inserted at minimum depth in the square waveguide section;

d. operation will be in linear polarization mode, as indicated at the system control panels. A

circular select signal applied now at 8A2A1-.11-L will cause the motor to drive once more to

the circuit configuration shown in the schematic diagram.

1.6.4.7.4 A capacitor connected across the ac input for each motor provides phase shift for the motor

winding. Capacitor C2 and back-to-back zener diodes that are connected across the motor

windings reduce the generation of transient spikes when the motors are switched off.

17

Figure 1-1 Typical Pattern, Azimuth

18

Figure 1-2 Typical Pattern, Elevation

19

Figure 1-3 Polarizer Schematic

02/08/2016 SDR-ASR11-052

TI 6310.59

20

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Andrew 174100 Installation and Maintenance Manual

Andrew 174100 Installation and Maintenance Manual

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