Isolation Test Procedure
Materials:
 Transmit Antenna to be used in the chamber
 Function Generator
 Spectrum Analyzer
 Dipole or other omni-directional antenna
 Low Loss Cables
 Step Latter
 Tape Measure
Chamber Diagrams
Door
Figure 1: Door side of chamber with measurement locations
TX
Figure 2: Transmit end of chamber with measurement locations
Figure 3: Back side/Top of chamber with measurement locations
DUT
Figure 4: Device under test end of chamber with measurement locations
Procedure:
1. Set up transmitting antenna in center of chamber. Connect Tx antenna to function
generator.
2. Set up spectrum analyzer outside chamber and connect Dipole antenna.
3. 50 measurements will be taken in total. Each measurement will be taken twice, once
with the door open, once with the door closed. Each measurement will be taken 1’ away
from the outside chamber per NSA Specification NO.94-1061
4. The first measurement will be taken outside the chamber a distance of 2’ away from the
transmit antenna (per NO.94-106). This will be used as a baseline
5. The next 13 measurements will be taken on the side with the door (measurements are
the red + symbols in Figure 1).
a. 2 measurements at each top corner.
b. 4 measurements at each corner of the door
c. 1 measurement 4’ down from the top at 4’ from the left on the joint
d. 3 measurements 8’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
e. 3 measurements at the right edge at 1’ up from the bottom, center, and 1’
down from the top.
6. The next 3 measurements will be taken at the Transmit end of the chamber
(measurements are the red + symbols in Figure 2).
a. 3 measurements 4’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
7. The next 14 measurements will be taken on the side of the chamber opposite the door
(measurements are the red + symbols in Figure 3).
a. 2 measurements at each top corner.
b. 3 measurements at the left edge at 1’ up from the bottom, center, and 1’ down
from the top.
c. 3 measurements 4’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
d. 3 measurements 8’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
e. 3 measurements at the right edge at 1’ up from the bottom, center, and 1’
down from the top.
8. The next 12 measurements will be taken on the top of the chamber (measurements are
the red + symbols in Figure 3).
a. 3 measurements at the left edge at 1’ up from the bottom, center, and 1’ down
from the top.
b. 3 measurements 4’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
c. 3 measurements 8’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
9.
10.
11.
12.
13.
d. 3 measurements at the right edge at 1’ up from the bottom, center, and 1’
down from the top.
The next 7 measurements will be taken at the DUT end of the chamber (measurements
are the red + symbols in Figure 4).
a. 2 measurements 2’ down from the top, 2’ from the left, and 2’ from the right2.
b. 3 measurements 4’ from the left at 1’ up from the bottom, center, and 1’ down
from the top on the joint.
c. 2 measurements 2’ up from the bottom, 2’ from the left, and 2’ from the right2.
With all 41 measurements recorded in a spread sheet, first subtract the measurement
from step 4 from each of the measurements in steps 5-8, this will give the reduction of
the chamber at each location.
Average all of the “door open” measurements together then subtract the measurement
from step 4. This will give the average reduction of the chamber with the door open.
Average all of the “door closed” measurements together then subtract the
measurement from step 4. This will give the average reduction of the chamber with the
door open.
Subtract the result from 11 from the result from 12, this is the isolation of the chamber.
1. A small change is made to the NSA NO. 94-106 as the transmitting antenna is fixed in the center
of the room. This means the antenna is 3’ away from the testing point for the sides, top and
bottom of the chamber, and 5’ away from the testing points for the ends. The measurements
for the isolation of the chamber will be edited to account for the E&H waves traveling these
distances in free space. Or using (1), the power at the inside measuring point for the sides, top
and bottom will be the power radiated from the transmit antenna- 38.1 dB and for the ends the
power transmitted- 42.55 dB
4𝜋𝑅
)
𝜆
𝑃𝐹𝑆𝐿 = 20 log (
2. Measurements taken due to holes drilled through the chamber
(1)