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Polarization
When HF radiation is emitted, it is sent off with a "polarization". In
short, the electromagnetic waves propagate either vertically or
horizontally. Therefore, both planes of polarization ought to be
checked in order to identify the one applying to the object in
question. Please note that the antenna supplied with this instru-
ment measures the vertically polarized plane if the upper surface
of the meter is held horizontically.
... and Consequences for the Execu-
tion of Measurements
When testing for HF exposure levels in an apartment, home or
property, it is always recommended to record individual meas-
urements on a data sheet. Later this will allow you to get a better
idea of the complete situation.
It is important to repeat measurements several times: First,
choose different daytimes and weekdays in order not to miss any
of the fluctuations, which sometimes can be quite substantial.
Second, once in a while, measurements should also be repeated
over longer periods of time, since a situation can literally change
"overnight".
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.
WLAN access points, also from neighbours).
Furthermore, you should be aware that taking measurements in-
doors adds another dimension of testing uncertainties to the
specified accuracy of the used HF analyser due to the narrowness
of indoor spaces. According to the "theory", quantitatively accu-
rate 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 expo-
sure levels. In order to keep system-immanent measurement un-
certainties 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 sub-
stantial fluctuations in measurement values. (This effect is even
more prevalent here than in the ELF range). It is suggested that
exposure assessments are based on the maximum value
within a locally defined area even though this particular value
might not exactly coincide with a particular point of interest in, for
example, the head area of the bed.
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