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Instruction Book
with
Parts List
January 1, 1996
TERMALINE® LOAD RESISTOR
MODEL 8833-300
Bird Electronic Corporation
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© Copyright 1996 by Bird Electronic Corporation
Instruction Book Part Number TO-nnnn-nn-nnn-nn
Termaline® is a registered trademark of
Bird Electronic Corporation
30303 Aurora Road
Cleveland (Solon), Ohio 44139-2794
Page 2
LIMITED WARRANTY
All products manufactured by Seller are warranted to
be free from defects in material and workmanship for
a period of one (1) 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 (transportationcharges 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. 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 WHATSOEVER, 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.
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RF Load Resistor Model 8833-300
Page 3
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.
Keep Away From Live Circuits
Operating personnel must at all times observe normal
safety regulations. Do not attempt to replace parts or
disconnect an RF transmission or any other high
voltage line while power is applied. When working
with high voltage always have someone present who
is capable of rendering aid if necessary. Personnel
working with or near high voltage should be familiar
with modern methods of resuscitation.
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.
The following will appear in the text of this publication
and are shown here for emphasis.
Warning
Before placing the unit into operation, remove the
shipping plug at the top of radiator, near front, substitute with the specially shielded breather plug. Use
a 3/4 inch flat wrench for this purpose - do not lose
the O-Ring seal. This vent hole must remain open at
all times when the unit is in operation or cooling.
Failure to do this could result in damage to the
equipment and endanger the operator’s safety. The
use of the vent plug also protects the filler opening
against intrusion of foreign material while allowing
unobstructed venting of the tank. The shipping plug
(with O-Ring seal) should be put back in place
whenever the unit is to be transported. Be sure to
check this plug.
Warning
Never attempt to disconnect RF equipment from a
transmission line while RF power is being applied.
Leaking RF energy is a potential health hazard.
Warning
Provide adequate ventilation and observe normal
precautions when using dry cleaning solvents. Many
dry cleaning agents emit toxic fumes that may be
harmful to your health if inhaled.
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Introduction5
1.
Purpose and Function5
Description5
RF Input5
Coolant5
Vent5
Items Supplied5
Specifications5
Component Location6
Installation7
Mounting7
Table Of Contents
Orientation7
Vent7
Installing Vent Plug7
Thermoswitch7
Checking the DC Resistance8
Theory of Operation9
General9
Dielectric Coolant9
Radiator9
Operating Instructions10
Load Resistor Connection10
Load Resistor Operation10
Maintenance11
General11
Checking DC Resistance of the Load Resistor11
Removing the Load Resistor11
Installing the Load Resistor11
Preventing Coolant Leakage12
Checking Coolant Level12
Pressure Vent12
RF Input Connector12
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RF Load Resistor Model 8833-300
Page 5
Introduction
1.1 Purpose and Function
The Model 8833-300 Termaline Load Resistor is
designed as a low reflection and nonradiating termination for coaxial transmission lines. It is a useful aid
in the tuning and troubleshooting of transmission
equipment within its rating.
1.2 Description
The Model 8833-300 RF Load is fully self-contained.
No additional equipment or outside power source is
required. Attached to the front and rear panels of the
rhombic-shaped radiator are mounting flanges.
These flanges act as supports for free standing use
in portable applications, or as mounting brackets for
optional fixed installation. There are mounting slots
provided in the flanges for this purpose, see Section
2 - Installation. Convenient carrying tabs are also
provided at each end of the radiator.
1.3 RF Input
The RF input connection is on the lower front face
of the unit. The Model 8833-300 is designed for use
with coaxial cable using large LC or LT connectors.
A female LC connector is installed at the factory, a
female N connector is also supplied. Bird Quick-
Change “QC” connectors, and how to change them,
are described in Section 5 - Maintenance.
1.4 Coolant
The load unit is filled with a specially selected dielec-
tric coolant chosen for its desirable thermal characteristics and dielectric properties.
1.5 Vent
The coolant inlet, when capped with the vent plug,
relieves internal pressure resulting from expansion of
heated coolant.
1.6 Items Supplied
Model 8833-300 RF Load Resistor
Female LC Connector (installed)
Female N Connector
Shipping Plug with O-Ring Seal (installed)
Vent Plug with O-Ring Seal (attached by chain)
Coolant (installed)
Interlock Thermoswitch (optional)
1.7 Specifications
Refer to Table-1 for operational specifications.
Table - 1
Specifications
Power Rating 1000 W continuous duty
RF Input Impedance 50 ohm
Input Connector Bird “QC” type, female LC normally supplied installed. Female N supplied as an
accessory.
Frequency Range DC - 2.5 GHz
VSWR
dc-1 GHz
1-2.5 GHz
1.10:1.0
1.25:1.0
Ambient Temperature -40°C to +45°C (-40°F to +113°F)
Dimensions 21-45/64"L x 7-1/8"W x 17-3/16"H (551 x 181 x 437 mm)
Weight 54 lb 10 oz (24.8 kg)
Finish Light navy gray (MIL-E-15090C)
Cooling Method Liquid dielectric and natural air convection
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1.8 Component Location
Refer to the following Outline Drawing, Figure- 1, for
dimensions and component location.
2.
Installation
2.1 Mounting
The Model 8833-300 Load Resistor is equipped for
either fixed installations or portable use. The load is
Figure - 1
Outline Drawing
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RF Load Resistor Model 8833-300
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free standing or can be attached to a bench, etc.,
Refer to Figure-1, Outline Drawing, for location of the
two mounting brackets and four mounting holes.
Attach the load using four suitable fasteners.
2.2 Orientation
This equipment is designed for operation in an up-
right position only, as shown in Figure-1, Outline
Drawing. Do not attempt to operate in any other
position.
2.3 Vent
The coolant filler inlet is capped with a shipping plug,
Figure-2, during transport from the factory. The shipping plug must be removed and replaced with the
vent plug, Figure-3, before operation. The vent plug
must also remain installed during cooling.
2.4 Installing Vent Plug
Warning
Failure to properly vent the radiator during operation
and cooling can result in equipment damage and
personal injury.
thermoswitch assembly, P/N 2450-056, is an available option. When installed in the radiator, it will
prevent damage from accidental transmitter power
overload or equipment malfunction. Being normally
closed, the thermoswitch opens at a maximum safe
temperature. Connected in series with the transmitter
interlock, it cuts off transmitter power if load temperature exceeds this value. The assembly consists of
the thermoswitch body, P/N 2450-040, with coupling
jack, P/N 2450-018, attached.
Thermoswitch Installation
Place the unit on its back, with the connector end
up. This position prevents coolant spillage.
Use a 9/16 allen wrench to remove the socket plug
on the front face of the radiator.
Replace the plug with the thermoswitch. Use an
acceptable pipe sealing compound sparingly, on the
external threads only, of the thermoswitch. Do not
contaminate coolant with pipe sealing compound.
Observe closely for coolant leaks upon completion.
Connecting the Thermoswitch, see Figure-4
Remove the shipping plug using a 3/4" flat wrench.
Ensure the o-ring seal stays in place on the shipping
plug.
Ensure the o-ring seal is in place on the vent plug.
Install vent plug.
2.5 Thermoswitch
Figure - 2
A
Shipping Plug
Unscrew the knurled ring-nut [A] at the lower end of
the coupling jack assembly. Pull it off the thermoswitch jack [B].
Unscrew the small knurled cover fitting [C] from the
base plug [D] of the connector to release the base.
Thread the interlock wires through the clamp [E] (with
washers [F] inside) and with its threaded fitting in
p
Figure - 3
Vent Plug
l
a
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Note: Be sure that the knurled ring nut [A] is in place over the base plug [D] with the knurled end
outward (towards face).
Screw on the cover ring [C].
Fasten the cable clamp [E], and tighten the two yoke
screws [H] on the cable.
Push the plug back on the thermoswitch, and tighten
captive knurled connecting ring.
Do not attempt to
operate the equipment without interlock attached.
2.6 Checking the DC Resistance
VSWR and RF Impedance are the true benchmark
of a quality dummy load. Checking the dc resistance
is simply used to measure a change in the condition
of the resistor over a period of time. If the application
requires such measurements, follow the steps below
to obtain a benchmark value before the unit is put
into service.
Preparation and Tools Required
Be sure the vent plug is installed, see paragraph 2.4.
Tools: Resistance Bridge or Ohmmeter with accuracy
of ±1% @50 ohms.
Temperature of the load is 20° to 25°C (68° to 70°F).
Normally the dc resistance of the load will be a
nominal 50 ohms. Stabilization of the resistive film or
temperature can cause a change in the dc resistance.
Check the resistance of the load periodically, according to use, and compare this resistance with the
original reading. If the values vary more than 2 ohms
this could be an indication of a failing resistive element.
3. Theory of Operation
3.1 General
The Model 8833-300 RF Load consists of a film-onceramic resistor immersed in a dielectric coolant. The
resistor, which is individually selected for its accuracy, is enclosed in an exponentially tapered housing,
providing a reduction in surge impedance directly
proportional to the distance along the resistor. When
the resistor unit is immersed in the dielectric liquid,
the characteristic impedance will be 50 ohms at the
connector end and graduate to zero ohms at the rear,
where the resistor joins the housing forming the
return conductor of the coaxial circuit. This produces
a uniform, practically reflectionless, line termination
over the stated frequencies of the load resistor.
Procedure
Using the resistance bridge or ohmmeter, check the
dc resistance of the load before it is put into service,
see Figure-5.
Record the value and keep for future use.
Figure - 4
Thermoswitch Assembly
Dielectric Coolant
3.2
The dielectric coolant, a low volatility, high flash point
synthetic oil, is chosen for its desirable thermal characteristics and dielectric properties, to which the
diameters of the resistor housing are matched. A
synthetic rubber o-ring around the outside of the
r
e
s
Checking DC Resistance
Figure - 5
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RF Load Resistor Model 8833-300
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istor housing mount furnishes a seal for the radiator
opening. A beveled flange retains the o-ring. The
o-ring is pressed against the radiator face by the
action of drawing up of radial V-band clamp around
the enclosing beveled flanges.
3.3 Radiator
When input power is applied, the resistor generates
heat which is absorbed by the surrounding dielectric
coolant. By convection, the heated oil flows through
holes in the coaxial shell to the walls of the radiator
tank. This radiator is a fabricated single-unit construction, and is carefully designed of heat-sink sections
on a unique vertical rhombic form. This provides a
very high efficiency of heat transfer from the dielectric
coolant into the surrounding air.
4. Operating Instructions
Load Resistor Connection
4.1
Warning
Provide adequate ventilation and observe normal
precautions when using dry cleaning solvents. Many
dry cleaning agents emit toxic fumes that may be
harmful to your health if inhaled.
The Model 8833-300 RF Load Resistor is very rugged and simple requiring little routine attention. The
load will operate for a long period of time if its power
handling capabilities are not exceeded.
Warning
Provide adequate ventilation and observe normal
precautions when using dry cleaning solvents. Many
dry cleaning agents emit toxic fumes that may be
harmful to your health if inhaled.
The outside surface of the unit should be wiped free
of dust and dirt when necessary. Clean the RF input
connector with an aerosol type contact cleaner or dry
cleaning solvent on a cotton swab stick. Take special
care to clean the metallic contact surface and the
exposed faces of the teflon insulator.
5.2 Checking the DC Resistance
VSWR and RF Impedance are the true benchmark
of a quality dummy load. Checking the dc resistance
is simply used to measure a change in the condition
of the resistor over a period of time. If the application
requires such measurements, follow the steps below
to obtain a benchmark value before the unit is put
into service, then periodically according to use.
Clean all conductors and insulator surfaces on the
transmission line face and check the RF input connector. Use an aerosol type contact cleaner or any
dry cleaning solvent on a cotton swab stick, if necessary.
Attach the Model 8833-300 Load Resistor to the RF
line with a 50 ohm coaxial cable such as RG-218/U
or RG-220/U (-17A or 19A) with a suitable plug
attached. Check that all coaxial power line connections are properly tightened. Avoid the use of adapters and elbows whenever possible.
4.2 Load Resistor Operation
Warning Never attempt to disconnect RF equipment
from a transmission line while RF power is being
applied. Leaking RF energy is a potential health
hazard.
Proceed according to the instructions pertaining to
the specific transmitting equipment. There are no
operating controls or adjustments for the Model 8833300 Termaline Load Resistor.
Due to the difference in VSWR between the dummy
load and the transmitter’s antenna, readjustment of
the transmitter may be required when returning to the
original antenna.
5. Maintenance
5.1 General
Preparation and Tools Required
Be sure the vent plug is installed, see paragraph 2.4.
Tools: Resistance Bridge or Ohmmeter with accuracy
of ±1% @50 ohms.
Temperature of the load is 20° to 25°C (68° to 70°F).
Procedure
Using the resistance bridge or ohmmeter, check the
dc resistance of the load before it is put into service,
see Figure-6.
Compare the value to benchmark value obtained
during installation.
Normally the dc resistance of the load will be a
nominal 50 ohms. Stabilization of the resistive film or
temperature can cause a change in the dc resistance.
If the values vary more than 2 ohms this could be
an indication of a failing resistive element.
5.3 Removing the Load Resistor
The load resistor assembly is not field serviceable.
In the event of a failure, the load resistor assembly—complete—must be replaced.
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Place the unit on its back, with the connector end
up. This position prevents coolant spillage.
Remove the clamping band by loosening the 10-32
x 1-1/2 inch screw on the clamping band.
Slowly lift the load resistor assembly out of the tank
allowing the coolant to drip back into the tank.
Check that the o-ring seal is in good condition, free
of twists, and positioned evenly all around the beveled flange of the resistor housing. If the condition is
questionable, or coolant has leaked around a securely-tightened clamping band, install a new o-ring
seal.
5.4 Installing the Load Resistor
Reverse the procedure described in paragraph
5.3.1—Removing the Load Resistor.
Tighten the clamping band securely, ensure the band
is fully seated, retighten the clamping band screw.
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band for coolant leakage. If leakage is observed:
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RF Load Resistor Model 8833-300
Tighten the clamping screw if required. If the coolant
continues to leak, proceed to step (b).
Remove the load resistor following instructions start-
Replace the resistor housing o-ring seal. Follow in-
ing in paragraph 5.3.
structions for removing and installing the load resistor
in paragraphs 5.3 through 5.4.
At room temperature the coolant level should be
4-3/4 inches (121 mm) below the top surface of the
5.6 Checking Coolant Level
load resistor assembly mounting ring.
The dielectric coolant level should remain constant
under normal operating conditions, but should be
checked periodically.
Place the unit on its back, with the connector end
up.
Note: The unit is filled at the factory— to the level described in step (c)—with 2.9 gallons (11 liters)
of specially selected dielectric fluid. Do not use any other coolant.
Add amount of coolant, p/n 5-030, required to bring
coolant up to the level described in step (c).
Install the load resistor following instructions starting
in paragraph 5.4.
5.7 Pressure Vent
When the coolant oil is heated, thermal expansion
will cause an increase in internal pressure. The vent
plug—when properly installed in the coolant inlet of
the radiator tank—provides a vent to relieve this
pressure and prevents dirt and other contaminants
from entering the radiator.
Ensure the vent plug is in place and free from
obstruction during operation and cooling.
5.8 RF Input Connector
The input connector on the Model 8833-300 is a Bird
Quick-Change or “QC” connector. As the name implies, changing the connectors is easy and quick.
Figure - 6
Checking DC Resistance
Connectors can be changed without disturbing the
coolant seal or interfering with coaxial continuity of
the load resistor input.
Replacing the RF Input Connector
Remove the four 8-32 x 5/16 inch round head ma-
chine screws from the corners of the RF connector
flange.
Pull the connector straight out.
Reverse the above procedure to install new connec-
tor, making certain that the projecting center contact
pin of the “QC” connector is carefully engaged and
properly aligned with the mating socket of the load
resistor.
The “QC” connector may be replaced with other
standard AN type connectors if obtained from Bird
Electronic Corporation. At the full power and fre-
quency capability of this model, only type LC or LT
(Female or Male) or 7/8 inch EIA (air line) connectors
will be adequate. For any other connector type, input
power must be limited to the specifications of the
selected type.
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5.9 Replacement Parts List
ItemQuantityDescriptionPart Number
11RF Load Resistor 8205-002
21 Resistor Housing O-Ring Seal, (included in item
1) 8110-039
31Clamping Band Assembly (2430-043 & Screw)
2430-055
42Shipping / Vent Plug O-Ring Seal 5-504
51Vent Plug 2450-094
61Shipping plug 2450-049
71Over Temperature Thermoswitch Assembly 2450-
056
81Thermoswitch Body (included in item 7) 2450-040
91 Thermoswitch Jack (included in item 7) 2450-018
102.9 gal.
(11 liter) Dielectric Coolant 5-030
111Radiator Assembly 2450-301
5.10 “QC” Type Connectors
N-Female*4240-062LT-Female4240-018
N-Male4240-063LT-Male4240-012
HN-Female4240-268C-Female4240-100
HN-Male4240-278C-Male4240-110
LC-Female*4240-031UHF-Female (SO-239) 4240-
050
BNC-Female4240-125UHF-Male (PL-259) 4240-179
BNC-Male4240-1327/8" EIA Air Line 4240-002
*Normally supplied
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