Digital High Frequency Analyser HF W 35C
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany
Revision 4.7 (October 2007)
Page
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lar value might 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 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 differ-
ent readings within 24 hours at exactly the
same spot. The maximum value across a
locally defined area, usually changes only if
the HF sources change, which is why the
latter value is much more representative of
the assessment of HF exposure.
The potential shifting of local maxima needs
special consideration when setting up WLAN
networks.
The following guidelines are meant for meas-
uring immissions in buildings, i.e. power den-
sity values for comparison with recom-
mended allowables.
A second application of this instrument is to
locate the source and strength of a specific
radiation (emission). The log.per antenna
coming with this instrument is best suited for
this. For defining counter measures and
shielding see separate section at the end of
this chapter.
Step-by-Step-Instruction to HF-
Measurement
Preliminary Notes Concerning the An-
tenna
Logarithmic-periodical antenna designs can
be optimized for two purposes:
•
Direction finding (narrow opening an-
gle sensitivity at the expense of
measurement accuracy)
•
Quantitative measurements (wide an-
gle sensitivity at the expense of direc-
tion finding.
Our antenna strikes a good compromise be-
tween the two, with very good accuracy with
still good direction finding. The direction to
the source can be determined with good ac-
curacy, a prerequisite for remedial action.
The readings from the instrument’s display
reflect the integral power density in the “an-
tenna lobe”. (ie., the antenna is most sensi-
tive, with a rounded peak, to radiation from a
direction parallel to its axis with the sensitiv-
ity tapering off rapidly with increasing angle
of incidence.)
The logarithmic-periodic antenna supplied is
optimized for the range 2.4 to 6 GHz 2400 to
6000 MHz).Its characteristic is compensated
by circuitry within the instrument over the full
range specified. This covers the following
services (some only in Europe /Germany
as of
Oct. 2006
):
2412 - 2484 MHz
WLAN b/g / Bluetooth
2450 MHz
Microwave oven
2700 - 2900 MHz
Airport Radar
2920 - 3100 MHz
Nautical Radar
3410 - 3494 MHz
WiMAX Low band
3510 - 3594 MHz
WiMAX High band
3600 - 4200 MHz
Beam radio
4200 - 4400 MHz
Aviation Radar
(height)
5030 - 5091 MHz
MLS
5150 - 5350 MHz
Wlan a/h BAND I
5470 - 5725 MHz
Wlan a/h Band II
5725 - 5875 MHz
WLAN
All of these are digitally pulsed and for this
reason considered of special biological rele-
vance by concerned physicians.
For monitoring of these critical sources of
radiation as conveniently as possible the fre-
quency band of the LogPer aerial supplied
together with the instrument has been limited
intentionally by its design to frequencies
above 2.4 GHz, i.e. frequencies below 2400
MHz are suppressed by the antenna design.
The suppression is additionally enforced by
an internal highpass filter at 2.4 GHz. This
reduces the disturbing impact of sources like
radio broadcasting, television stations, ama-
teur radio, cellular and DECT phones on the
measurements to a minimum.
Beyond 6 GHz the sensitivity curve of an-
tenna and instrument droop slowly. To make
use of this fading sensitivity no lowpass filter
has been built in.
In order to measure frequencies below 2.4
GHz Gigahertz Solutions offers a wide range
of instruments.
