Bird Technologies 8000 Series - Manual (Page 13)

Chapter 2
Theory of Operation
General
The resistive element, in these dry Termaline Loads, is indi-
vidually selected for its accuracy, and enclosed in a heat
sink housing. The housing is specially contoured inside to
provide the load with its unusually low reflection character-
istics throughout its entire frequency range. The housings
for the 25, 50, 100, and 150 Watt models are deeply slotted
and painted black with a lusterless finish to improve their
heat dissipation. Models 8173 and 8431 are fabricated with
sheet metal fins to more efficiently meet their higher heat
dissipation requirements.
5