User Manual

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I1b09911A:\ISDIR\8340S.IS
INSTRUCTION SHEET
FOR
8340 SERIES
TENULINE
®
ATTENUATORS
Series 8340 TENULINE
®
Attenuators are low reflecting resistance
networks designed to reduce RF power by known and controlled amounts.
Each is a self-contained, dry, air-cooled device that is useful for
lowering RF power to a level suitable for an oscilloscope or frequency
counter. There are three basic models available for maximum RF powers of
25, 40, and 100 watts and each model can be s upplied with 3, 6, 10, or 20
dB of attenuation. Models 8340 and 8343 are convection air cooled with
built in radiators while Model 8341 is conduction cooled and must be
bolted to a suitable heat sink. Details on the dimensions, weights, and
operating parameters are given in the table of specifications.
TENULINE
®
Attenuators are electrically symmetrical "T" pads with the
power distribution on the legs being different. A "T" configuration is
used to provide equal input and output impedance for a 50 ohm line. The
input resistor is joined to the "T" leg joint in a housing designed to
produce the proper input impedance, and the output resistor is so enclosed
as to return the characteristic impedance to 50 ohms.
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* C A U T I O N *
* *
* If the Model 8341 is used without heat sink, its maxi- *
* mum power rating is reduced from 40 W to only 15 W. Do *
* not exceed this| *
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These attenuators do not require any external source of power or
additional equipment to function. The exception to this is the 8341
group. They must be bolted to a flat aluminum heat sink of at least 400
square inches and 1/8 inch thickness. Prior to mounting the unpainted
side of the attenuator to the heat sink, both surfaces should be
carefully cleaned of any burrs or foreign particles. Then coat the
joining surfaces with a thin and uniform layer of a high conductivity
heat transfer compound such as Wakefield "120" compound. The heat sink
must be previously bored with four 13/64 to 7/32 inch diameter holes set
in a 1-45/64 x 1-1/4 inch rectangle. Fasten the attenuator tightly to the
heat sink with 10-32 x 1-1/2 inch machine screws, nuts and lockwashers.
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