Hameg Instruments HZ530 Manual Del Usuario página 42

42
lines which are significantly above the noise level. Of course, the
spectrum display will be different at each location depending on
the relative distance of transmitters. Even in rural areas cellular
telephone lines must show the absence of which would show that
the probe has insufficient sensitivity at the higher frequencies.
Measurement
of the Ambient
Spectrum.
Figure 8
The measurement of the ambient spectrum serves not only to
determine probe sensitivity. If the measurements are not perfor-
med in a shielded room, the ambient signals can also serve as a
reference to recognize the most important frequencies which do
not originate from the EUT.
To perform the measurements, the EUT is set up, without the
additional shield, at a minimum distance of 0.5 meter from the
probe. Then the EUT is rotated in azimuth to find the maximum of
the radiation from the EUT. At this point the data is recorded as
shown in Figure 9.
EUT RFI
Characteristics
without
Additional Shield
Figure 9
Comparison of Figure 9 with Figure 8 shows that RFI is radiated up
to a frequency of 1GHz. The maximum of the radiated power occurs
at frequencies between 250 to 350MHz. The strongest signal is at
the marker frequency of 275MHz at a level of 42.8 dBm.
Next, the same measurement is performed with the additional
shielding around the EUT. Again the EUT must be rotated in azimuth
Änderungen vorbehalten / Subject to change without notice