TERMALINE® LOAD RESISTOR
SERIES 8251
©Copyright
2012 by Bird Electronic Corporation
Instruction Book Part Number 920-8251S Rev. G
Termaline® is a Registered Trademark of
Bird Electronic Corporation
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 uninterruptible 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.
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.
Safety Symbols
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.
i
This symbol indicates that a shock hazard exists if the precautions in the
instruction manual are not followed.
The caution symbol appears on the equipment indicating there is important information in the instruction manual regarding that particular area.
This symbol indicates that the unit radiates heat and should not be touched
while hot.
This symbol indicates that the item must not be discarded but instead
managed according to the collection and recycle of waste electrical and
electronic equipment (WEEE) as outlined in Directive 2002/96/EC of the
European Parliament and of the Council of 27 January 2003 on waste
electrical and electronic equipment (WEEE).
Note: Calls attention to supplemental information.
Warning Statements
The following safety warnings appear in the text where there is danger to operating and maintenance personnel, and are repeated here for emphasis.
Caution Statements
The following equipment cautions appear in the text and are repeated here for emphasis.
ii
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.
iii
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.
iv
CONNECT INTERLOCK TO TRANSMITTER/GENERATOR/AMPLIFIER BEFORE
OPERATING.
BRANCHER LE VERROUILLAGE À L’ÉMETTEUR/GÉNÉRATEUR/
AMPLIFICATEUR AVANT EMPLOI.
CONECTE EL INTERBLOQUEO AL TRANSMISOR/GENERADOR/
AMPLIFICADOR ANTES DE LA OPERACION.
VOR INBETRIEBNAHME VERRIEGELUNG AM SENDER/GENERATOR/
VERSTÄRKER ANSCHLIESSEN.
PRIMA DI METTERE IN FUNZIONE L’APPARECCHIO, COLLEGARE IL
DISPOSITIVO DI BLOCCO AL TRASMETTITORE/GENERATORE/
AMPLIFICATORE.
v
About This Manual
This instruction book covers the following models:
8251 8251N 8251D 8251D7-16
8251T-230 8251T-300
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 manual, please send your comments to our Solon,
Ohio factory. This manual may be periodically updated. When inquiring about updates to this
manual refer to the part number and revision on the title page.
Definitions
Measure Match Mode - The Match Measurement mode shows the resonant frequencies
for an antenna or filter. It also confirms that there are no impedance problems in the nonresonant components such as cables, connectors, lightning protectors, and jumpers.
Fault Location Mode - The Fault Location mode shows the location of any problems in the
antenna system. This is shown in either feet or meters from the cable end connected to the
Site Analyzer.
Cable Loss Mode - The Cable Loss mode shows the insertion loss of a coaxial cable. By
comparing this with the manufacturer’s specs, it confirms that there are no problems with the
cable.
VSWR - VSWR units used to be the preferred way to measure an antenna system. A good
antenna has a VSWR of less than 1.5:1 at its operating frequency.
Return Loss - Return Loss measures, in dB, how much of a wave is reflected back to the source. It is
now the preferred method for measuring antenna systems. A good antenna will have a return loss of –14
dB or less at the operating frequency. The more negative the reading, the better the antenna.
Markers - Markers are used to show the exact value at one point on the graph. In Measure
Match and Cable Loss modes, the marker displays the frequency and loss (or VSWR). In Fault
Location mode, the marker displays the distance and loss.
Run / Hold - When HOLD is displayed, the unit makes a new sweep every few seconds, and
displays the latest sweep. When RUN is displayed, the unit will only make a single sweep. The
display will not update if the Site Analyzer is disconnected or if the cable is jiggled. This is usually preferred.
vi
Table of Contents
Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i
Warning Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Caution Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Safety Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Changes to this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vi
Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Items Supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 2 Theory of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Coolant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Thermal Interlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Chapter 3 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Installing Thermoswitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Connecting RF Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Using a “QC” Connector Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Using a 13-30 Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Using a Swivel Flanged Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Using a Unflanged Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 4 Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Normal OperationNormal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Operating Under Abnormal Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Shutting Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Emergency Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
DC Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Coolant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
RF Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Rear Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Storage and Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Storing the Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Shipping the Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Customer Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Available “QC” Type Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
. . . . . 18
vii
viii
Chapter 1 Introduction
WARNING
6”
(151 mm)
8.5”
(216 mm)
18” (455 mm) nominal
Connector dependent
15”
(380 mm)
5/”
(130 mm)
1
8
3.5”
(89 mm)
(4) MTG.
HOLES
VENT PLUG
INTERLOCK
THERMOSWITCH
(OPTIONAL)
Bird 8251 Series Loads are portable, general purpose 50 ohm coaxial RF transmission line terminations. They are
accurate, dependable, and low reflection, dissipating up to 1000 watts of RF power. See Figure 1 on page 1 for frequency ranges.
The load has a coolant chamber surrounded by radiator fins. A handle is recessed in the radiator fins. The front and
rear fins form mounting flanges which can be used as supports for freestanding use or as brackets for fixed mounting. A vent plug at the top of the unit relieves internal pressure from coolant expansion. The load’s simple and rugged design minimizes maintenance requirements.
Applications
Use an 8251 load:
• As a substitute antenna for tuning transmitters under nonradiation conditions or for making routine tests
and adjustments.
• As a substitute for any circuit loading element.
• To measure, with a suitable meter, the power output of coaxially transmitted signals.
Items Supplied
• Load Resistor: Pre-filled with coolant at the factory
• Shipping Plug
• Vent Plug
• Instruction Manual
Figure 1 Outline Drawing
Connector Frequency Range
8251 Female LC DC – 2400 MHz N/A
8251N Female N DC – 1000 MHz N/A
†
8251D
8251D7-16 7/16 IEC 470 – 860 MHz N/A
8251T-230
8251T-300
‡
‡
* Optional thermoswitch kit (P/N 2450-129) available.
† Requires bullet (P/N 4712-020) – not included
‡ Bullet included
1-5/8” EIA Swivel 470 – 860 MHz N/A
1-5/8” EIA Fixed Flanged DC – 2000 MHz 230 ºF (110 ºC)
1-5/8” EIA Fixed Flanged DC – 2000 MHz 300 ºF (149 ºC)
Thermoswitch
Temperature
*
*
*
*
1
2
Chapter 2 Theory of Operation
O-ring seal
O-ring seal
Load Resistor
Bird 8251 series loads consist of a thin-film-on-ceramic resistor immersed in a dielectric coolant. The resistor, individually selected for its accuracy, is enclosed in a special housing. When surrounded by the coolant, this produces a
uniform, practically reflectionless line termination over the specified frequencies.
Coolant
The load is cooled by natural fluid and air convection currents. The coolant, chosen for its dielectric and thermal
characteristics, carries heat from the resistor to the walls of the cooling tank, where radiator fins surrounding the
tank transfer the heat to the air.
When the coolant is heated, thermal expansion causes an increase in the internal pressure. An expansion tank on
the upper rear of the load allows for coolant expansion due to the rise in temperature, and is equipped with a vent
plug to relieve this pressure while protecting the opening from dirt or other contaminants.
Thermal Interlock
Loads can be supplied with an optional passive overtemperature thermoswitch. Normally closed, it opens at either
230 or 300 °C (110 or 149 °F), depending on the setting, turning off transmitter power. The interlock system will not
permit use of the transmitter until the load has reached a safe temperature.
Figure 2 Shipping Plug
Figure 3 Vent Plug
3
4
Chapter 3 Installation
This chapter provides information for on-site requirements, unpacking, inspection, and preparing the load for use.
Unpacking and Inspection
1. Carefully inspect shipping container for signs of damage.
2. Do one of the following:
• If the shipping container is damaged, do not unpack the unit. Immediately notify
the shipping carrier and Bird Electronic Corporation.
• If the shipping container is not damaged, unpack the unit. Save shipping materi-
als for repackaging.
3. Inspect unit for visual signs of damage.
Note: If there is damage, immediately notify the shipping carrier and Bird Electronic Corporation.
Setup
Note: Before first using the load, get a resistance baseline for future maintenance. Refer to "DC Resistance"
on page 12 for details.
1. Remove the shipping plug from the load.
2. Replace the shipping plug with the vent plug. Refer to Figure 1 and Figure 2 for pictures of the plugs.
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to
do so could result in an explosion or severe burns.
Mounting
Place the load in a dry, dust and vibration free environment. Do not use outdoors or in areas of condensing humidity.
For operation above 300 W, allow at least 6" (15 cm) of clearance on all sides of the load.
CAUTION
This load is designed for operation in a horizontal position only, with the vent plug up. Do not use in any other
manner.
The load is equipped for either portable use or fixed installation. The mounting brackets on the front and rear faces
have four mounting slots arranged in a 5
eter max.
1
⁄8” x 15” rectangle (130 x 381 mm). Use a screw with a 1⁄4” (6.4 mm) diam-
5
Installing Thermoswitch
RF CONNECTOR
TEMP. SET SCREW
DO NOT ADJUST!
TERMINALS
COVER
SCREW
COVER
SCREW
Bird 8251T loads are identical to the 8251 except for a factory-installed interlock thermoswitch. It is normally closed,
opening at either 230 or 300 °F (110 or 149 °C), depending on the model. The terminals are rated for 10A @ 120 Vac
and 5A @ 240 Vac.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized from multiple sources.
The potential for electric shock exists.
CAUTION
The thermoswitch has a factory preset temperature adjustment screw. Do not adjust this screw.
1. Unscrew the cover screws and remove the thermoswitch cover.
2. Thread the interlock wires through the grommet on the side of the cover.
3. Wrap the interlock wires around the terminals and clamp them in place with the terminal nuts.
Note: Do not apply more than 10 in.lb. (1.1 N-m) of torque to the terminal nuts.
4. Replace the cover.
5. Check the requirements of the transmitter interlock and make connections as
required.
Figure 4 Thermoswitch
Connecting RF Power
Note: After installing the load, the RF transmission line can be attached using standard coaxial line cou-
pling kits.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF power is being
6
applied. Leaking RF energy is a potential health hazard.
Using a “QC” Connector Coupling
BOLT BULLET LOADRF COAXIAL LINE
RF COAXIAL
LINE
CLAMPING
BANDS
CONNECTOR
SLEEVE
BULLET
LOAD
Use a 50 ohm coaxial cable such as RG-218/U or -220/U (-17A or -19A), appropriate for the frequency and power
level of operation.
Note: Use a cable connector which will mate with the one on the load.
Using a 13-30 Coupling
Use 50 ohm coaxial cable such as RG-8A/U, RG-9U, RG-213/U, or equivalent with a male 13-30 plug.
Using a Swivel Flanged Coupling
1. Insert the center bullet.
2. Push it in until it is fully seated.
3. Connect the coaxial input in a straight line
4. Push, carefully, on the center conductor to close.
Note: The swivel flange on the load makes connection independent of the
orientation of the fixed flange on the coaxial input outer conductor.
5. Insert the bolt sets and tighten evenly all around to transmission line manufacturer’s
recommended torque.
Note: Use all of the bolts.
Figure 5 Swivel Flanged Coupling
Using a Unflanged Coupling
1. Insert the center bullet
2. Push until it sets the midpoint nibs.
3. Position the outer sleeve, with clamping bands, over the input connector.
4. Set the transmission line snugly against the coupling stops.
5. Position the clamping bands evenly about 3/4” from the ends of the sleeve.
6. Tighten the clamping bands.
Figure 6 Unflanged Coupling
After the transmitter has been connected to the load, proceed according to the transmitter manufacturer’s instructions. When reconnecting the antenna, it may be necessary to slightly readjust the transmitter due to differences in
VSWR between the load and the antenna system.
7
8
Chapter 4 Operating Instructions
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do so could result in an
explosion or severe burns.
Normal OperationNormal Operation
Bird 8890 series– 300 loads have no indicators or operating controls. They require no special operating procedures or surveillance when their performance limits are not exceeded. Follow the instructions for the specific transmitter equipment.
Operating Under Abnormal Conditions
The load can be moderatly overloaded for short periods.
CAUTION
Make sure the interlock is properly connected when overloaded to prevent damage to the load.
Shutting Down
Note: These loads are passive devices, so have no way of being turned off. Turn off RF power at the source.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF power is being applied.
Leaking RF energy is a potential health hazard.
Emergency Shutdown
Turn off RF power at the source.
Note: If the interlock thermoswitch is properly connected, RF power will be automatically turned off when
the coolant temperature reaches an unsafe level
9
10
Chapter 5 Maintenance
This chapter covers cleaning, inspection, trouble-shooting, and specifications for the Bird 8251 series loads.
Troubleshooting
The table below contains troubleshooting information for problems which can occur during normal operation. This
manual cannot list all malfunctions that may occur, or their corrective actions. If a problem is not listed or is not corrected by the listed actions, notify a qualified service center.
Problem Possible Cause Correction
Leaking coolant Loose clamping band Tighten the clamping band
Defective or improperly installed
front O-ring
Defective or improperly installed
rear O-ring
Replace the O-ring
(See “Load Resistor” on page 15)
Replace the O-ring
(See “Rear Seal” on page 14)
High or low DC
resistance
Overheating radiator RF power too high Lower RF power (See “Specifications” on page 17
Loose RF input connector Tighten connector
Faulty RF input connector Models with “QC” type connectors: Replace
connector (See “RF Connector” on page 13)
All other models: Return the unit for service
Faulty resistor Replace the resistor
(See “Load Resistor” on page 15)
for maximum RF power)
Coolant level too low Check the coolant level. Add coolant if necessary
(See “Coolant” on page 12)
Coolant degraded Replace the coolant
(See “Coolant” on page 12)
Faulty resistor Replace the resistor
(See “Load Resistor” on page 15)
Maintenance
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF power is being
applied. Leaking RF energy is a potential health hazard.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized from multiple sources.
The potential for electric shock exists.
11
Cleaning
The outside surface of the instrument should be wiped free of dust and dirt when necessary. Excessive dust on the
cooling fins will interfere with heat dissipation. Clean the RF connector, both metallic and insulating surfaces, with a
dry, non-residue forming solvent.
Inspection
Inspect the unit every six months. Check for coolant leakage around the clamping band and the thermoswitch. Also
check for corrosion.
DC Resistance
Measuring the DC resistance between the inner and outer conductors of the RF connector shows changes in the
load over time, a good check of the load resistor’s condition. Under normal operating conditions, the resistor should
provide at least 5,000 hours of operation before requiring any additional service. DC resistance tracking must start
before the load is put into service, and should be measured annually.
Perform the following steps and record the value for future comparison. Make sure that you have an ohmmeter with
an accuracy of ±1% at 50 ohms and that the load temperature is between 20 and 25 °C (68 to 77 °F) before starting.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF power is being applied.
Leaking RF energy is a potential health hazard.
1. Turn off the RF power and interlock circuitry.
2. Disconnect the RF line.
3. Connect the multimeter test leads to the center and outer conductor of the load
resistor.
4. Compare the measured value with the previous measurement and with the baseline
resistance, measured when the load was put into service.
Note: If the new value differs from either of these by more than 1 ohm this
could indicate a failing resistor.
Figure 7 Measuring Resistance
Coolant
Coolant lifetime will vary greatly depending on operating conditions. For heavy use (full RF power for long times,
high ambient temperature), check the coolant every 500 hours. If the load has only had light duty (fraction of full
power, low ambient temperature), then coolant inspection may only be necessary every 2,000 hours.
Note: Correct any coolant leakage before inspection.
12
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized from multiple sources.
The potential for electric shock exists.
CAUTION
Use only Bird coolant, P/N 5-1070, to prevent damage to the load.
1. Remove the load resistor (Refer to “Load Resistor” on page 18).
CAUTION
Use only Bird coolant, P/N 5-1070, to prevent damage to the load.
2. Inspect the coolant.
• The coolant should be clear, with a faint yellow tinge, and have a slightly sweet
smell. If it is black with a burnt or acrid smell, drain it and add about 2.9 gal (11
L) of coolant.
• With the load still on end, the coolant level should be 4
below the top surface of the resistor assembly mounting ring, at ambient temperature.
3. Add coolant if necessary
Repair
3
⁄4 to 5 inches (125 mm)
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized from multiple sources.
The potential for electric shock exists.
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do so could result in an
explosion or severe burns.
RF Connector
The Bird 8251 and 8251N have a special Bird “QC” connector which allows easy changing of the RF connector. This
does not disturb the coolant seal or affect the electrical continuity of the load. To change the connector, proceed as
follows:
1. Remove the four screws at the corners of the RF connector.
2. Pull the connector straight out.
3. Push the new connector in.
4. Ensure that the center pin on the connector is properly seated in the mating socket
on the load.
5. Replace the screws.
Note: If not using the connector normally supplied, frequency and power must
be limited to the capabilities of the connector.
13
Rear Seal
TUBE
NUT
EXPANSION
TAN K
CLAMPING
BAND
ESCAPE
TUBE
REAR
COVER
If the coolant has not been drained from the load, stand the unit on end with the RF connector down before disassembly.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized from multiple sources.
The potential for electric shock exists.
6. Unscrew the four screws at the corners of the guard cover.
7. Unscrew the tube nut from the tank nozzle, using a small wrench if necessary, and
pull the nozzle free.
8. Unscrew and remove the clamping band.
9. Remove the rear cover, including the attached escape tube and the diaphragm seal.
10. Inspect the diaphragm seal and replace it if it is not pliable or has surface cracks.
11. To reassemble, reverse these steps.
Figure 8 Rear Seal
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do so could result in an
explosion or severe burns.
14
Load Resistor
1. Remove the vent plug.
2. Install the shipping plug.
3. Stand the unit on its back, with the RF connector up.
4. Brace the unit to prevent it from tipping over.
5. Unscrew and remove the clamping band.
6. Lift the load resistor assembly out of the tank and allow any coolant to drip back into
7. Replace the entire load resistor assembly.
8. Put the clamping band in place and tighten it.
9. Remove the shipping plug. Install the vent plug.
Storage and Shipment
Storing the Load Resistor
the tank.
Note: The O-Ring should be free of twists and positioned evenly around the
flange of the resistor housing. If the O-ring shows signs of deterioration (e.g. is
no longer pliable or has surface cracks) replace it.
Note: It cannot be further disassembled.
• Cover the Load before storing to keep out dust and dirt.
• It is not necessary to install the shipping plug.
• Store in a dry, dust-free environment where the ambient temperature will remain between –40 and +45 °C
(–40 to +113 °F).
Shipping the Load Resistor
1. Remove the vent plug.
2. Install the shipping plug.
3. Wrap the vent plug with padding and tape it to the side of the load for protection.
Note: With the shipping plug installed, it is not necessary to empty out the
coolant.
4. Wrap the connector in padding.
5. Pack and brace the load in a sturdy wooden crate for shipment.
15
Customer Service
Any maintenance or service procedure beyond the scope of those in this chapter should be referred to a qualified
service center.
If you need to return the unit for any reason, request an RMA through the Bird Technologies website (link shown
below). All instruments returned must be shipped prepaid and to the attention of the RMA number.
Bird Service Center
30303 Aurora Road
Cleveland (Solon), Ohio 44139-2794
Fax: (440) 248-5426
E-mail: bsc@bird-technologies.com
For the location of the Sales Office nearest you, visit our website at:
http://www.bird-technologies.com
16
Specifications
Frequency Range
Power Rating 1000 Watts continuous duty
Impedance, Nominal 50 ohms
Operating Position Horizontal only – vent plug up
VSWR
Connectors
Thermoswitch Temperature
Ambient Temperature –40 to +45 °C (–40 to +133 °F)
Cooling Method Oil dielectric and convection currents
Dimensions 18”L x 6”W x 8.5” H
Weight, Nominal 25 lb. 8 oz. (11.6 kg)
Finish Gray Powder Coat
8251
8251T
8251N
8251D, 8251D7-16
8251N
8251D, 8251D7-16
*
8251
8251T
8251
8251D
8251D7-16
8251N
8251T
8251T-230
8251T-300
DC – 2400 MHz
DC – 2000 MHz
DC – 1000 MHz
470 – 860 MHz
1.10
1.065
1.10, DC – 1000 MHz
1.20, 1000 – 2000 MHz
1.30, 2000 – 2400 MHz
1.10, DC – 800 MHz
1.20, 800 – 1000 MHz
1.30, 1000 – 2000 MHz
“QC” Type, Female LC
1–5/8” EIA Swivel Flanged
7/16 Jack, IEC
“QC” Type”, Female N
“QC” Type”, 1-5/8 EIA Fixed Flanged
110 °C (230 °F)
149 °C (300 °F)
(455 x 151 x 216 mm)
* VSWR Measured using a female N connector.
Replacement Parts
RF Load Resistor:
8251D
8251D7-16
All other models
Resistor O-Ring 1 5-230
Clamping Band Assembly 1 2430-055
Plug
Vent
Shipping
Thermoswitch Kit
149 °C (300 °F)
110 °C (230 °F)
Description Qty Part Number
1
8892-015
8890A050
8890A050
1
2450-094
2450-049
1
2450-129-1
2450-129-2
17
Coolant, 0.75 gal (2.84 L) 1 5-1070-2
Optional Bullet, 8251D Only 1 4712-020
Available “QC” Type Connectors
Connector Part Number
BNC-Female 4240-125
BNC-Male 4240-132
C-Female 4240-100
C-Male 4240-110
HN-Female 4240-268
HN-Male 4240-278
LC-Female
LC-Male 4240-025
Open Term. # 10-32 Nut 4240-080
LT-Female 4240-018
LT-Male 4240-012
N-Female
N-Male 4240-063
SC-Female 4240-090
SMA-Female 4240-336
SMA-Male 4240-334
7/16 Jack, IEC Type 169-4 4240-344
7/16 Plug, IEC Type 169-4 4240-363
Mini UHF-Female 4240-346
UHF-Female 4240-050
UHF-Male 4240-179
1-5/8” EIA Fixed 4240-096
1-5/8” EIA Swivel 4240-208
7/8” EIA 4240-002
TNC-Female 4240-156
TNC-Male 4240-160
*
†
4240-031
4240-062
18
* Normally supplied on the 8251
† Normally supplied on the 8251N
Limited Warranty
All products manufactured by Seller are warranted to be free from defects in material and workmanship for a period
of one year, unless otherwise specified, from date of shipment and to conform to applicable specifications, drawings, blueprints and/or samples. Seller’s sole obligation under these warranties shall be to issue credit, repair or
replace any item or part thereof which is proved to be other than as warranted; no allowance shall be made for any
labor charges of Buyer for replacement of parts, adjustment or repairs, or any other work, unless such charges are
authorized in advance by Seller.
If Seller’s products are claimed to be defective in material or workmanship or not to conform to specifications, drawings, blueprints and/or samples, Seller shall, upon prompt notice thereof, either examine the products where they
are located or issue shipping instructions for return to Seller (transportation-charges prepaid by Buyer). In the event
any of our products are proved to be other than as warranted, transportation costs (cheapest way) to and from
Seller’s plant, will be borne by Seller and reimbursement or credit will be made for amounts so expended by Buyer.
Every such claim for breach of these warranties shall be deemed to be waived by Buyer unless made in writing
within ten (10) days from the date of discovery of the defect.
The above warranties shall not extend to any products or parts thereof which have been subjected to any misuse or
neglect, damaged by accident, rendered defective by reason of improper installation or by the performance of
repairs or alterations outside of our plant, and shall not apply to any goods or parts thereof furnished by Buyer or
acquired from others at Buyer’s request and/or to Buyer’s specifications. Routine (regularly required) calibration is
not covered under this limited warranty. In addition, Seller’s warranties do not extend to the failure of tubes, transistors, fuses and batteries, or to other equipment and parts manufactured by others except to the extent of the original manufacturer’s warranty to Seller.
The obligations under the foregoing warranties are limited to the precise terms thereof. These warranties provide
exclusive remedies, expressly in lieu of all other remedies including claims for special or consequential damages.
SELLER NEITHER MAKES NOR ASSUMES ANY OTHER WARRANTY WHAT-SOEVER, WHETHER EXPRESS, STATUTORY, OR
IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS, AND NO PERSON IS AUTHORIZED TO
ASSUME FOR SELLER ANY OBLIGATION OR LIABILITY NOT STRICTLY IN ACCORDANCE WITH THE FOREGOING.
19
20
Loading...