ETS-Lindgren 5411 GTEM! Test Cell - Manual (Page 76)

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Radiated Emissions Test Performance of GTEM!
P
ERSONAL
C
OMPUTER
T
ESTING
The second test series involved comparison testing of two different small,
desktop personal computer systems. They were installed, secured to a piece of
plywood with the subsystem components and interconnecting cables strapped to
the plywood with nylon strapping. The strapping was firm since the entire EUT
installation would be rotated to allow three orthogonal axes voltage
measurements. Each personal computer system consisted of a system unit,
monitor, keyboard, parallel device (printer), mouse, and serial device (printer or
modem). These items were installed as shown in the figures distributed in
ANSI 63.4. These figures require the installation of the EUT on a 1-m x 1.5-m
table. In the testing described in this paper a 1-m x 1.5-m piece of 12-mm
plywood was used. The system unit was installed with the back end of the
chassis aligned with the back edge of the plywood base and centered. The
monitor was centered on the system unit. The printer (required parallel
peripheral) was installed to the right of the system unit at a distance of 10 cm.
The modem (required serial peripheral) was installed 10 cm to the left of the
system unit. The back edges of all of these units were aligned with the back edge
of the plywood. The keyboard was centered and aligned with the front edge of
the plywood. The mouse was installed 10 cm from the right edge of the keyboard
and aligned with the back of the keyboard. All items were secured to the
plywood. The plywood array was then transferred into the test volume of the
GTEM! used for this testing.
The three orthogonal measurement alignments are illustrated as indicated here:
 Personal Computer System Installed for V
xyz
Measurement as Seen From
Apex on page 77—shows the orientation for V testing
 Personal Computer System Installed for V
yzx
Measurement as Seen From
Apex on page 78—shows the orientation for V testing
 Personal Computer System Installed for V
zxy
Measurement as Seen From
Apex on page 79—shows the orientation of V testing
The relative position of the subsystem components is shown in each illustration.
Also shown are the calculated field uniformity contours for 1 dB, 2 dB, 3 dB, and
4 dB referenced to the center of the test volume. The illustrations are oriented as
viewed from the apex of the GTEM!. To maximize the measured emissions
values, the draping of the cable from the first position measured was preserved
for a minimum of 30 cm from the back edge of the table.