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Seite 29
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Nevertheless, the “true” mean value is of great interest, too
10
:
-
The “official” limit values are always based on mean value exam-
inations. When analysing “official” measurement results, there-
fore, such as those for instance done for cell phone operators, it
may be useful to have a possibility of comparison.
-
Different radio services will never have an equal ratio between
mean values and peak values. DECT cordless phones, for in-
stance, can have a ratio of as high as 1:100, while for GSM the
ratio may vary from 1:1 up to 1:8.
-
Especially in the case of the new broadband modulated radio
services, such as LTE, the RMS value and – thanks to the crest
factor of max. 10 dB – also the arithmetical peak value can both
be reliably determined.
Users of professional spectrum analysers please note:
-
The value for pulsed radiation shown on the display of the Gigahertz Solutions
HF Analysers with the signal switch set to “Peak” corresponds to the equivalent
value in μW/m² resulting from the “Max. Peak” function of a modern spectrum
analyser (elder spectrum analysers had a similar function mostly called “posi-
tive peak”).
-
The switch setting “RMS” corresponds the “true RMS” setting of a modern
spectrum analyser (elder spectrum analysers have a similar function mostly
called “normal detect”, as well as a setting for the video bandwidth adapted to
match the pulse).
-
In broadband-measurement technology “Videobandwidth” (VBW) is under-
stood differently than in terms of spectrum analysis.
Setting: “Signal”
Peak hold
In the interior, local peak values are mostly subject to strong fluctua-
tions (caused by multiple reflections). In order not to overlook any
local maxima (so called hot spots), indoor measurements should,
therefore, preferably be done with the “Peak hold” setting.
Switching impulses can cause “pseudo peaks” which will appear on
your display. These can be deleted by pressing and holding the
“clear” button for several seconds (while keeping the “clear” button
pressed, the measurement will turn into a regular peak measure-
ment). Releasing the “clear” button will trigger the period during
which the maximum value is to be determined.
In the “Peak hold” mode, the sound signal remains proportional to
the currently measured power flux density. This helps finding the ab-
solute maximum within the measured area.
The droop rate, at which the held peak value decreases over time can be controlled
with the “+” and “-” switch. Even after several minutes, the value displayed is still
10
Users of meters produced by other manufacturers please note: The a.m. conclu-
sions are only feasible for recordings of the true mean value. They do not apply if
your meter shows the momentary value of the modulated HF signal only instead of
the mean value, which is the case for most meters on the market, even if their
specifications state that it will display the mean value.
Summary of Contents for HF59B
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