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Made in Germany
expansion of the cellular phone networks (LTE, 5G) as well as wire-
less LAN hotspots have a considerable impact on the exposure lev-
els.
Even if you only intend to test indoors, it is recommended first to
take measurements
in each direction
outside of the building. This
will give you an initial awareness of the “HF tightness” of the build-
ing, and also potential HF sources inside the building (e.g. cordless
phones, also from neighbours).
Furthermore, you should be aware that taking measurements in-
doors adds another dimension of testing uncertainties to the spec-
ified accuracy of the used HF analyser due to the narrowness of
indoor spaces. According to the “theory”, quantitatively accurate
HF measurements are basically only reproducible under so-called
“free field conditions”, yet we have to measure HF inside buildings
because this is the place where we wish to know exposure levels.
In order to keep system-immanent measurement uncertainties as
low as possible, it is imperative to carefully follow the measurement
instructions.
As mentioned earlier in the introduction, even slight changes in the
positioning of the HF analyser can already lead to rather substantial
fluctuations in measurement values. (This effect is even more prev-
alent here than in the ELF range.)
It is suggested that exposure
assessments are based on the maximum value within a locally
defined area
even if this particular value should not exactly coin-
cide with a particular point of interest in, for example, the head area
of the bed.
The above suggestion is based on the fact that slightest changes
within the environment can already cause rather major changes in
the power density of a locally defined area. The person who per-
forms the HF testing, for example, affects the exact point of the
maximum value. It is quite possible to have two different readings
within 24 hours at exactly the same spot. The maximum value
across a locally defined area, however, usually only changes if the
HF sources are subject to change. This is why the latter value is
much more representative for the assessment of HF exposure.
The descriptions in the following mainly refer to immission meas-
urements, i.e. to the definition of the total power flux density rele-
vant for limit value comparisons.
In addition, this device can also be used to identify the source of
radiation, and – most important – to determine appropriate shield-
ing measures. The logper antenna which comes with the meter is
predestined for this aim. The procedure to determine appropriate
shielding methods is described at the end of this chapter in a sep-
arate section.
Preliminary Notes Concerning the Antenna
The supplied logarithmic-periodic antenna (or
aerial), has excep-
tional
directionality
. Thus it becomes possible to reliably locate or
“target” specific emission sources in order to determine their con-
tribution to the total HF radiation level – a fundamental prerequisite
for effective shielding.
Содержание HF58B
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