Seite 18
ROM-Elektronik GmbH
are registered correctly. When we consider the frequency range 600 MHz
to 2600 MHz, the uncertainty of measurement is still within ±6dB. In practice
this means that, in all-pass operation (= broadband), 3G (UMTS) and WLAN
signals can be somewhat undervalued, therefore a measured value is dis-
played which is too small.
We can counter this situation through the use of the built-in filters! The HFR-3
has frequency-specific calibration factors for every filter. Through this, it is
possible to consider an individual calibration factor in operation with selec-
ted filter, which influences the entire frequency response.
In other words: As is clear from the above graphics, the sensitivity decrea-
ses somewhat in all-pass operation (red curve) in the WLAN frequency ran-
ge. If the filter is now switched on for WLAN, the actual, true measured
value is displayed, which can be significantly above the value that was de-
termined in all-pass operation.
Do not be surprised if, for example, you measure a pure WLAN signal and,
in case of activated WLAN filter, a higher measured value is displayed than
in all-pass operation. A similar effect can possibly also be observed with
DECT and 3G (UMTS) signals.
Reverse attenuation
Reverse attenuation is indicated for every filter, with reference to the trans-
mission loss.
The reverse attenuation thus indicates how frequencies are strongly sup-
pressed, at least outside of the pass band.
For example, the damping of the GSM900 filter is 64 dB in the pass band
and 35 dB in the reverse attenuation range. Frequencies in the reverse at-
tenuation range are therefore decreased by 29 dB more than in the pass
range. The reverse attenuation is 29 dB.
The reverse attenuation applies for frequencies with sufficient separation
from the respective mobile communications frequency range.
Table 4 shows typical reverse attenuations of the filter up to 2.5 GHz. The
Filter
Reverse
attenuation
Elec. field strength
remaining display
Power flux density
remaining display
At least
At most
At most
GSM900
29dB
3,5%
0,13%
GSM1800
34dB
2,0%
0,04%
DECT
40dB
1,0%
0,01%
3G (UMTS)
16dB
15,8%
2,51%
WLAN
24dB
6,3%
0,40%
Table 4: Reverse attenuation of the filters to 2.5 GHz
Seite 35
ROM-Elektronik GmbH
now be saved (see later).
Change of mode:
It is possibly to carry out a "change of mode" from field
strength to power flux density and vice versa, only during an on-going mea-
surement. The programming of the HFA3 measuring device requires this. For
this, it should also be ensured through the user that the measuring device is
in Mode E (field strength, display V/m) before the first measurement with the
HFA3 1.0 software.
Reference:
Some adjustments in the menu bars or selection lists (e.g. filter,
automatic system mode) are effective only after the measurement has
been started.
Alternatively a measurement can be stored by klicking
this symbol. This symbol is only active in long term stora-
ge.
Alternatively a measurement can be opened by
klicking this symbol. This symbol is only active in long
term storage.
Menuleiste
Alternatively, the terminal display can be selected by
clicking this icon.
Alternatively, the indication display can be selected by
clicking this icon.
Alternatively, the recording display can be selected by
clicking this icon.
Alternatively, a measurement can be started by click-
ing this icon.
