Service manual

4 Agilent 382A Operating and Service Manual

Operation

Align Flanges The height of the 382A should be adjusted carefully so that precise

alignment will be obtained at the coupling flanges to prevent undue strain on

one flange while the other is unsupported. A screw at each corner of the base

will enable height and leveling adjustments to be made. When the

instrument is supported at both ends, as in permanent installations, the feet

or base may be removed altogether, if desired (K or R bands).

CAUTION Do not force dial stops. When setting attenuation do not force the dial

against the mechanical stops at the ends of the attenuation range. Forcing the

dial can change the calibration.

Setting Attenuation Attenuation is set by the knob and read directly on the dial. A white

background strip moves behind the dial window to select the range to read

(not on K, or R band). Read only the range with the white background. The

MAX setting gives the maximum attenuation of at least 70 dB at all

frequencies.

Principles of

Operation

The attenuator consists of three sections of waveguide in tandem. In each

section a resistive film is placed across the guide as shown in Figure 1. The

middle section is a short length of round guide which is free to rotate radially

with respect to the two fixed end sections. The end sections are rectangular

to-round waveguide transitions in which the resistive films are normal to the

E field of the applied wave. The construction is symmetrical and the device

is bi-directional.

Figure 1 Attenuation Principle