BIRD 4308 User manual

INSTRUCTION BOOK
RF DIRECTIONAL
THRULINE® WATTMETER
MODEL 4308
©Copyright 2011 by Bird Electronic Corporation
Instruction Book Part Number 920-4308 Rev. E
Thruline® and Termaline® are registered trademarks
of Bird Electronic Corporation

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i
Safety Precautions
The following are general safety precautions that are not necessarily
related to any specific part or procedure, and do not necessarily appear
elsewhere in this publication. These precautions must be thoroughly
understood and apply to all phases of operation and maintenance.
WARNING
Keep Away From Live Circuits
Operating Personnel must at all times observe general safety
precautions. Do not replace components or make adjustments to the
inside of the test equipment with the high voltage supply turned on.
To avoid casualties, always remove power.
WARNING
Shock Hazard
Do not attempt to remove the RF transmission line while RF power
is present.
WARNING
Do Not Service Or Adjust Alone
Under no circumstances should any person reach into an enclosure
for the purpose of service or adjustment of equipment except in the
presence of someone who is capable of rendering aid.
WARNING
Safety Earth Ground
An uniterruptible earth safety ground must be supplied from the
main power source to test instruments. Grounding one conductor of
a two conductor power cable is not sufficient protection. Serious
injury or death can occur if this grounding is not properly supplied.

Bird 4308 Thruline Wattmeter
ii
Safety Symbols
The caution symbol appears on the equipment indicating
there is important information in the instruction manual
regarding that particular area
 Note: Calls attention to supplemental information.
WARNING
Resuscitation
Personnel working with or near high voltages should be familiar
with modern methods of resuscitation.
WARNING
Remove Power
Observe general safety precautions. Do not open the instrument
with the power on.
WARNING
Warning notes call attention to a procedure, which if not correctly
performed, could result in personal injury.
CAUTION
Caution notes call attention to a procedure, which if not correctly
performed, could result in damage to the instrument.

iii
Warning Statements
The following safety warnings appear in the text where there is dan-
ger to operating and maintenance personnel, and are repeated here
for emphasis.
Refer to page 7.
Caution Statements
The following equipment cautions appear in the text whenever the
equipment is in danger of damage, and are repeated here for emphasis.
Refer to page 7.
WARNING
Leaking RF energy is a potential health hazard. Never attempt to
connect or disconnect equipment from the transmission line while
RF power is being applied. Severe burns, electrical shock, or death
can occur.
CAUTION
Do not drop the Thruline Wattmeter equipment or submit it to hard
blows. The voltmeter circuitry or microammeter, even though it is
shock mounted, may be damaged by severe impact.

Bird 4308 Thruline Wattmeter
iv
Safety Statements
USAGE
ANY USE OF THIS INSTRUMENT IN A MANNER NOT
SPECIFIED BY THE MANUFACTURER MAY IMPAIR THE
INSTRUMENT’S SAFETY PROTECTION.
USO
EL USO DE ESTE INSTRUMENTO DE MANERA NO
ESPECIFICADA POR EL FABRICANTE, PUEDE ANULAR LA
PROTECCIÓN DE SEGURIDAD DEL INSTRUMENTO.
BENUTZUNG
WIRD DAS GERÄT AUF ANDERE WEISE VERWENDET ALS VOM
HERSTELLER BESCHRIEBEN, KANN DIE GERÄTESICHERHEIT
BEEINTRÄCHTIGT WERDEN.
UTILISATION
TOUTE UTILISATION DE CET INSTRUMENT QUI N’EST PAS
EXPLICITEMENT PRÉVUE PAR LE FABRICANT PEUT
ENDOMMAGER LE DISPOSITIF DE PROTECTION DE
L’INSTRUMENT.
IMPIEGO
QUALORA QUESTO STRUMENTO VENISSE UTILIZZATO IN
MODO DIVERSO DA COME SPECIFICATO DAL PRODUTTORE
LA PROZIONE DI SICUREZZA POTREBBE VENIRNE
COMPROMESSA.

v
SERVICE
SERVICING INSTRUCTIONS ARE FOR USE BY SERVICE -
TRAINED PERSONNEL ONLY. TO AVOID DANGEROUS
ELECTRIC SHOCK, DO NOT PERFORM ANY SERVICING
UNLESS QUALIFIED TO DO SO.
SERVICIO
LAS INSTRUCCIONES DE SERVICIO SON PARA USO EXCLUSIVO
DEL PERSONAL DE SERVICIO CAPACITADO. PARA EVITAR EL
PELIGRO DE DESCARGAS ELÉCTRICAS, NO REALICE NINGÚN
SERVICIO A MENOS QUE ESTÉ CAPACITADO PARA HACERIO.
WARTUNG
ANWEISUNGEN FÜR DIE WARTUNG DES GERÄTES GELTEN
NUR FÜR GESCHULTES FACHPERSONAL. ZUR VERMEIDUNG
GEFÄHRLICHE, ELEKTRISCHE SCHOCKS, SIND
WARTUNGSARBEITEN AUSSCHLIEßLICH VON
QUALIFIZIERTEM SERVICEPERSONAL DURCHZUFÜHREN.
ENTRENTIEN
L’EMPLOI DES INSTRUCTIONS D’ENTRETIEN DOIT ÊTRE
RÉSERVÉ AU PERSONNEL FORMÉ AUX OPÉRATIONS
D’ENTRETIEN. POUR PRÉVENIR UN CHOC ÉLECTRIQUE
DANGEREUX, NE PAS EFFECTUER D’ENTRETIEN SI L’ON N’A
PAS ÉTÉ QUALIFIÉ POUR CE FAIRE.
ASSISTENZA TECNICA
LE ISTRUZIONI RELATIVE ALL’ASSISTENZA SONO PREVISTE
ESCLUSIVAMENTE PER IL PERSONALE OPPORTUNAMENTE
ADDESTRATO. PER EVITARE PERICOLOSE SCOSSE
ELETTRICHE NON EFFETTUARRE ALCUNA RIPARAZIONE A
MENO CHE QUALIFICATI A FARLA.

Bird 4308 Thruline Wattmeter
vi
RF VOLTAGE MAY BE PRESENT IN RF ELEMENT SOCKET - KEEP
ELEMENT IN SOCKET DURING OPERATION.
DE LA TENSION H.F. PEAT ÊTRE PRÉSENTE DANS LA PRISE DE
L'ÉLÉMENT H.F. - CONSERVER L'ÉLÉMENT DANS LA PRISE LORS
DE L'EMPLOI.
HF-SPANNUNG KANN IN DER HF-ELEMENT-BUCHSE ANSTEHEN -
ELEMENT WÄHREND DES BETRIEBS EINGESTÖPSELT LASSEN.
PUEDE HABER VOLTAJE RF EN EL ENCHUFE DEL ELEMENTO RF -
MANTENGA EL ELEMENTO EN EL ENCHUFE DURANTE LA
OPERACION.
IL PORTAELEMENTO RF PUÒ PRESENTARE VOLTAGGIO RF -
TENERE L'ELEMENTO NELLA PRESA DURANTE IL
FUNZIONAMENTO.

vii
About This Manual
This manual covers the operating and maintenance instructions for
the following models:
Changes to this Manual
We have made every effort to ensure this manual is accurate. If you
discover any errors, or if you have suggestions for improving this man-
ual, please send your comments to our Solon, Ohio factory. This man-
ual may be periodically updated. When inquiring about updates to
this manual refer to the part number and revision on the title page.
Literature Contents
Chapter Layout
Introduction —Describes the features of the 4308 Wattmeter, lists
equipment supplied and optional equipment, and provides power-up
instructions.
Theory of Operation —Describes how the 4308 Wattmeter works and
Installation —Describes how to set up and prepare the 4308 Wattme-
ter for use.
Operation - All instructions necessary to operate the equipment
appears in this chapter.
Maintenance —Lists routine maintenance tasks as well as trouble-
shooting for common problems.
4308

viii
Table of Contents
Safety Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Warning Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Caution Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Safety Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
Changes to this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Chapter Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Purpose and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 2 Theory of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Travelling Wave Viewpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Travelling Wave vs Standing Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Coupling Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Chapter 3 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Portability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Installing in a 50 Ohm Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Zero Adjust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Range Switch and Power Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 5 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Repair and Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Line Section or Element Coupling Circuit . . . . . . . . . . . . . . . . . . . . . . . . . 15
Meter Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Line Section and Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Connector Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Element Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Element Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Meter Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Calibration Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Customer Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

ix
Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Available “QC” Type Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

x

1
Chapter 1 Introduction
Purpose and Function
The Model 4308 Thruline Wattmeter is a portable multi-range RF
wattmeter. It is a device which requires no external power source or
batteries for operation. It is used to measure RF power when inserted
into a transmission line of 50 ohms impedance. When operated in this
manner, it is used to determine power flow and load mismatch in coax-
ial transmission lines. It may be used to make measurements of CW,
FM, or PM (Plane Modulated) RF Power.
Performance Characteristics and Capabilities
On the front face of the unit, there are four power ranges which are
controlled by a selector switch. Each position of the selector switch
corresponds to a power range on the read-out meter, refer to the Spec-
ifications. There is also a “TRANSIT” position to be used when trans-
porting the unit. This position effectively shunts the delicate meter
movement to avoid damage from harsh blows.
The meter, line section, and related circuitry of the instrument are
contained in a rugged aluminum housing. This housing is equipped
with a carrying strap, four rubber bumper feet on the bottom, and four
rubber bumper feet on the back. These bumper feet allow the unit to
be used in a standing (vertical) or flat (horizontal) position.

Bird Model 4308 Wattmeter
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3
Chapter 2 Theory of Operation
Travelling Wave Viewpoint
The operation of the Model 4308 wattmeter is based on the
travelling wave concept of RF transmission. As RF power is
applied to a transmission line, there is a forward wave travelling from
the transmitter to the load and a reflected wave travelling from the
load back to the transmitter. The closer the line termination, or load,
is matched to the line impedance, the smaller the reflected wave will
be. To determine the number of watts dissipated in the load, it is nec-
essary to determine both the power of the forward wave and the power
of the reflected wave. The difference between the two will indicate
effective power dissipation.
Travelling Wave vs Standing Wave
The interference between the forward and reflected waves, produces a
standing wave in a coaxial system. In the standing wave concept, VSWR
(voltage standing wave ratio) is a widely used tool. There is a simple rela-
tionship between forward power, reflected power, and VSWR.
 Note: Where Wf = forward power; and Wr = reflected.
VSWR
1Wf
Wr
--------+
1Wf
Wr
--------–
----------------------=

Bird Model 4308 Wattmeter
4
Figure 1 Model 4308 Outline Drawing
Power
Since there is a definite relationship between the standing wave ratio
and the forwardreflected power ratio, the forward and reflected pow-
ers may be read from the Thruline Wattmeter and converted to
VSWR. The charts are furnished in this Instruction Book.
4240-156
440-960 MHz
4308-1
50 W
ELECTRONIC
1.5
5
15
50
TRANSIT
1-5/16
RUBBER FEET (4)
3-3/8
3-5/8
3-29/32
(33mm)
(99mm)
(92mm)
(86mm)
4"
(101mm)
6-7/8
(175mm)
1-3/4
(44mm)
Q.C. CONNECTOR
RUBBER FEET(4)

Bird Model 4308 Wattmeter
5
Coupling Circuit
The coupling circuit which samples the travelling waves is in the
Plug-In Element. The circuitry of the element and its relationship to
the other components of the Thruline Wattmeter are illustrated in the
schematic diagram, see figure 2.
Energy will be produced in the coupling circuit of the element by both
mutual inductance and capacitance from the two travelling RF waves
in the line section. The inductive currents will flow according to the
direction of the travelling waves producing them, whereas the capaci-
tive portion of these currents is independent of the direction. There-
fore, in either position of the Plug-In Element, the coupling currents
produced from the waves of one direction will add in phase, and those
produced from waves of the opposite direction will accordingly sub-
tract in phase. The additive direction is indicated by the arrow.
The electrical values of the element circuits are carefully balanced and
designed so that the inductive current produced from the reverse wave
will cancel its portion of the capacitive current almost completely. The
result is a directivity greater than 25 dB, which means that the ele-
ment is highly insensitive (i.e. produces little or no signal) from the
reverse direction wave. By being so highly directional, the Detector
element is sensitive at either one of its settings, but to only one of the
two travelling waves. Thruline Wattmeter measurements are also
independent of their position along the standing waves.

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6
Figure 2 Schematic Diagram
RF Coaxial Line
XMTR
or
LOAD
LOAD
or
XMTR
Directional Coupling
Detector Element
Diode
Meter
DC Contact
Circuit Board

7
Chapter 3 Installation
Portability
The Model 4308 is a portable instrument, and the housing is not
designed for fixed mounting. A strap is provided for carrying purposes.
To protect the meter movement during periods of transit, put the
range switch in the “TRANSIT” position. This effectively shunts the
meter movement and dampens the pointer action.
Connections
Installing in a 50 Ohm Line
1. Attach the transmission line to the connectors on either side of the
wattmeter housing.
CAUTION
Do not drop the Thruline Wattmeter equipment or submit it to hard
blows. The voltmeter circuitry or microammeter, even though it is
shock mounted, may be damaged by severe impact.
WARNING
Leaking RF energy is a potential health hazard. Never attempt to
connect or disconnect equipment from the transmission line while
RF power is being applied. Severe burns, electrical shock, or death
can occur.

Bird Model 4308 Wattmeter
8
 Note: It makes no difference which sides the RF power
source and the load are connected.
 Note: Use of a short length of 50 ohm cable fitted with the
appropriate mating connectors may be useful when inserting
the wattmeter in the transmission line.
2. Rotate the element so that the arrow points in the direction of
power flow.
 Note: If coaxial cables other than 50 ohm impedance are
used, a mismatch will occur which may cause serious inaccura-
cies in the readings.
Figure 3 Element Direction
To Load To Transmitter
To Load To Transmitter
Forward Power Measurement
Reflected Power Measurement