Gigahertz Solutions HF59B Instruction Manual page 7

Digital High Frequency Analyser HF59B
Measurements for a Quick Overview
This is helpful to gain insight into the overall
situation. Since the actual number values are
of secondary interest in this phase, it is usu-
ally best to simply follow the audio signals
which are proportional to the field strength.
(Set" On/Off" switch ("Mode" to:
turn down the audio analysis knob to low).
Procedure for the
Quick Overview Measurement:
The HF analyzer and antenna are to be
checked following the instructions under
"Getting Started."
First set the measurement range ("Range
Selection") switch to "Coarse". Only if the
displayed measurement values are persis-
tently below ca. 0.10 mW/m², change to the
measurement range "Medium" (199.9µW/m²)
or to "Fine" (19.99 μ W/m²).
Set the "Signal Evaluation" switch to "Peak"
HF radiation exposure can differ at each
point and from all directions. Even though the
HF field strength of a given space changes
far more rapidly than at lower frequencies, it
is neither feasible nor necessary to measure
all directions at any given point.
Since this is not an accurate quantitative
measurement, but a quick overview assess-
ment, the antenna can be removed from the
top end of the HF analyzer, for convenience.
Holding the antenna at its very end as de-
scribed in "Getting Started", the polarization
plane (vertical or horizontal) can easily be
changed with a turn of your wrist. However,
you can just as well use the HF analyzer with
the antenna attached to it.
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany
Since there is no need to look at the display
during an overview measurement, you only
need to listen to the audio signal. It is very
easy to walk slowly through in-door or out-
door spaces in question. In doing so con-
stantly moving the antenna or the HF ana-
lyzer with attached antenna, in each direc-
, and tion. This will provide you with a quick over-
view of the situation. In in-door spaces, an-
tenna movements towards the ceiling or the
floor will reveal astonishing results.
Note: When switching from „19,99mW/m²" to
„199,9µW/m²" the audio signals gets much
louder; Between
„19.99µW/m²" there is no difference in loud-
ness.
As already mentioned above, overview
measurements are not meant to provide
accurate results, but to identify those
zones within which local peak values are
found.
Quantitative Measurement:
Settings
After having identified the relevant measure-
ment points following the instructions in the
previous section. The actual testing can be-
gin.
Setting:
Measurement Range Selection
Select the appropriate switch settings as
described under "Quick Overview Measure-
ments". Basic rule for measurement range
selection:
Revision 4.5 (December 2006)
„199,9µW/m²" and
- As coarse as necessary, as fine as possible.
Note:
To allow for as wide a range of power densi-
ties to be read out without using an external
attenuator, a factor of 100 lies between adja-
cent ranges. That means for example an ac-
tual value of 150 µW/m² will be displayed as
150.0 µW/m² in the range "Medium" and as
0.15 mW/m² in the range "Coarse". Due to
technical reasons the tolerances of the in-
strument are relatively high in this overlap-
ping 1% of the next higher range
Rules of thumb for the interpretation of
the results
Readings in the two adjacent sensitivity
ranges "Medium" and "Coarse" use the
one with the higher value.
Numbers below 0.05 mW/m² shown in the
range "Coarse" are within the range of its
potential zero bias. Use the reading shown in
range "Medium".
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Power densities of a few hundred µW/m², displayed
as 0.01 up to about 0.30 mW/m² in the setting
"Coarse", are those with the highest measurement
uncertainties as % of the actual values. On the other
hand setting the switch to "Medium" activates an inter-
nal amplifier, which brings with it an additional wavi-
ness of up to +/- 1 dB, depending on the actual fre-
quency analysed. Worst case combined to worst case
could absorb almost +/- 3 dB, the maximum tolerance
of the instrument. For very small readings in "Coarse"
that could result in a factor of 4 difference of the corre-
sponding reading with setting "Medium". Numerical
example: In "Medium" you read 150.0 µW/m². In
"Coarse" you could read up to 0.6 mW/m² or down to
0.03 mW/m² in an extreme case. Normally the differ-
ences shown will be much smaller.
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