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phone networks (LTE, 5G) as well as wireless LAN hotspots have a
considerable impact on the exposure levels.
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 building,
and also potential HF sources inside the building (e.g. cordless
phones, also from neighbours).
Furthermore, you should be aware that taking measurements indoors
adds another dimension of testing uncertainties to the specified ac-
curacy of the used HF analyser due to the narrowness of indoor
spaces. According to the “theory”, quantitatively accurate HF meas-
urements 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 preva-
lent here than in the ELF range.)
It is suggested that exposure as-
sessments are based on the maximum value within a locally de-
fined area
even if this particular value should not exactly coincide
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 performs 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 repre-
sentative for the assessment of HF exposure.
The descriptions in the following mainly refer to
immission
measure-
ments, i.e. to the definition of the total power flux density relevant for
limit value comparisons.
In addition, this device can also be used to identify the source of ra-
diation, and – most important – to determine appropriate shielding
measures. The logper antenna which comes with the meter is pre-
destined for this aim. The procedure to determine appropriate shield-
ing methods is described at the end of this chapter in a separate sec-
tion.
Preliminary Notes Concerning the Antenna
The supplied logarithmic-periodic antenna (or
aerial), has exceptional
directionality
. Thus it becomes possible to reliably locate or “target”
specific emission sources in order to determine their contribution to
the total HF radiation level – a fundamental prerequisite for effective
shielding.
Important
:
As the LogPer
Antenna provided with this instrument is shielded
Summary of Contents for HF59B
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