Digital High Frequency Analyser HF W 35C
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany
Revision 4.7 (October 2007)
Page
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by ten and compare this value with limits or
recommendations.
Please note that there are Radar systems
that are operated at even higher frequencies
that can be measured with this instrument,
yet possibly not the full intensity.
Quantitative Measurement:
Identify where the radiation enters a struc-
ture
As a first step eliminate sources from within
the same room (e.g. cordless phones, wire-
less routers, etc.) Once this is completed, the
remaining radiation will originate from out-
side. For remedial shielding it is important to
identify those areas of all walls (including
doors, windows and window frames!), ceiling
and floor, which are penetrated by the radia-
tion. To do this one should not stand in the
centre of the room, measuring in all direc-
tions from there, but monitor the permeable
areas with the antenna (log.-per.) directed
and positioned close to the wall
2
. That is be-
cause the antenna lobe widens with increas-
ing frequency. In addition reflections and
cancellations inside rooms make it difficult
and often impossible to locate the “leaks”
accurately. See the illustrating sketch below!
wall
antenna
wall
antenna
potentiell
durchlässiger
Bereich
wrong!
right!
potentially HF-permeable
part of the wall
The uncertainty of localization with HF-antennas
2
Please note: In this position the readings on the LCD
only indicate relative highs and lows that cannot be
interpreted in absolute terms.
The shielding itself should be defined and
surveyed by a specialist and in any case the
area covered by it should be much larger
than the area of incidence.
Limiting values, recommenda-
tions and precautions
Precautionary recommendation
for sleeping areas with pulsed radiation
Below 0.1 µW/m²
(“no anomaly” according to recommenda-
tions to the standard of building biology
measuring technology SBM 2003)
for indoor areas
below 1 µW/m²
(according to: Landessanitätsdirektion
Salzburg, Austria)
The official regulations in many countries
specify limits far beyond the recommenda-
tions of environmentally oriented, critical
doctors, “building biologists” and many sci-
entific institutions and also those of other
countries. They are vehemently criticised, but
they are nonetheless “official”. The limits de-
pend on frequencies and in the HF range of
interest here they are at 10 W/m² for the fre-
quencies considered here, far beyond 10
million times the recommendations. Official
limits are determined by the potential heat
generation in the human body and conse-
quently measurements of averages rather
than peaks. This ignores the state of envi-
ronmental medicine. The “official” limits are
far beyond the range of this instrument,
which is optimized for accurate measurement
of power densities targeted by the building
biologists.
The standard SBM 2003 cited above classi-
fies power densities of below 1 µW/m² as “no
anomaly” for non pulsed radiation in sleeping
areas, and for pulsed radiation one tenth of
that.
The cerebric pulsing found in the Alpha fre-
quency range (about 10 Hertz), as for in-
stance used by WLAN, are considered espe-
cially active.
Effects on human health have
already been observed at values far below
0.1 µW/m²!
The "Bund für Umwelt und Naturschutz
Deutschland e. V." (BUND) proposes 100
µW/m² outside buildings. In view of the
shielding properties of normal building mate-
rials, far lower values exist inside buildings.
In February 2002 the Medical Authority of the
Federal State Salzburg, Austria, recommends
to reduce its “Salzburger Precautionary Rec-
ommendation” from 1 000 µW/m² to 1 µW/m²
inside buildings and 10 µW/m² outside.
These limits are based on empirical evidence
over the past few years.
The ECOLOG-Institute in Hannover, Ger-
many made a recommendation only for out-
side areas, namely 10000 µW/m². This is well
above the recommendation by building bi-
ologists and aims at getting consent also
from the industry. This would possibly enable
a compromise for a more realistic limit than
the government regulations cited above. The
authors qualify their recommendation in
