Gigahertz Solutions HF58B, Инструкция по эксплуатации

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Properties of HF Radiation…
Across the specified frequency range (and beyond), HF radiation
can cause any of the following effects on the materials exposed to
it:
1. Partial permeation
2. Partial reflection
3. Partial absorption.
You may, therefore, come across various extremely differing field
distributions within one building, with strong peaks at individual
spots (so called “hotspots”).
Minimum Distance
In order to measure the quantity of HF radiation in the common unit
“power density” (W/m²), a certain distance has to be kept from the
HF source. The distance depends on the frequency – the higher the
frequency the lower the distance. The transition frequency between
so called far field and near field conditions is not determined ex-
actly, but here are some typical distances:

27 MHz from approx. 27 meters

270 MHz from approx. 2.7 meters

2700 MHz from approx. 0.27 meters
That means the distances are inversely proportional to the frequen-
cies.
Polarization
When HF radiation is emitted, it is sent off with a “polarization”. In
short, the electromagnetic waves propagate either vertically or hor-
izontally. Cellular phone technology, which is of greatest interest to
us, is usually vertically polarized, or at an angle below 45°. Due to
reflection effects and the many ways in which a cellular handset
can be held, we also observe other polarization patterns. Therefore,
it is always strongly recommended to measure both polarization
planes, which is defined by the orientation of the antenna.
… 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 equally 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”. Major changes in exposure levels can, for instance, al-
ready be caused by a transponder only being tilted down by a few
degrees (e.g. during installation or repair works on cellular phone
transmitters). In particular, however, the worldwide extremely rapid