Gigahertz Solutions HF58B Instruction Manual page 9

Digital High Frequency Analyser HF58B
Most manufacturers of professional testing
equipment, however, do not share this view.
In general, it is well accepted that
exposure limit comparisons should be
based on the maximum value emitted
from the direction of the strongest
radiation source.
But the details of the situation need to be
considered! For example, if a 2.4-GHz tele-
phone inside the house emits a similar level
of microwaves as a nearby cellular phone
base station outside the house, it would be
helpful to first turn off the 2.4-GHz telephone
in the house. Now measure the exposure
level originating from the outside. After hav-
ing measured the emission of the 2.4-GHz
telephone on its own, the sum of both meas-
urement values could be used for the expo-
sure assessment.
There is no "official regulation" nor clearly
defined testing protocol, because according
to German national standard-setting institu-
tions, as described earlier, quantitatively reli-
able, targeted and reproducible measure-
ments are only possible under "free field con-
ditions" but not in indoor environments.
Cellular phone channel emissions vary with
the load. The minimum HF level occurs,
when only the control channel operates. It is
suggested that measurements should be
taken at different times during the day / week
in order to find out the times of highest traf-
fic.
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany
Quantitative Measurement:
Special case 1: UMTS / 3G
(Universal Mobile Telecommunication Sys-
tem, also known as the third generation of
mobile phones.) This technology is designed
to process huge amounts of data and has a
narrowly meshed network.
With LogPer aerial and in "Peak " mode iden-
tify the main direction of the signal and
switch to " Peak Hold – long"
Now "gather" the highest value without mov-
ing the meter ( use a wooden tripod ) for at
least 2 minutes in the same position. This is
important as because of the signal character-
istics of the UMTS/3G signal fluctuations by
the factor +/- 6 are common.
To hear samples how a UMTS/3G signal
sounds in the audio-analysis please check
our website for links to MP3 files.
Please note:
- UMTS signals can be underrated by as
much as 5 times even when using the sug-
gested switch setting combination "Peak
Hold" and "Full". Gigahertz Solutions of-
fers the HF58B-r and HF59B RF analysers,
to measure the complex UMTS signals
- When measuring UMTS/3G you should not
use the combination of switch-positions
"Average" and "Pulse" .
Quantitative Measurement:
Special Case 2: Radar
For air and sea navigation a radar antenna
slowly rotates around its own axis, thereby
emitting a tightly bundled "radar ray". Even
with sufficient signal strength, this ray can
Revision 4.5 (December 2006)
only be detected every couple of seconds,
for a few milliseconds. This requires special
measurement technology.
Please use the following procedure to ensure
correct readings:
Setting: Signal Evaluation – "Peak". With the
help of the audio analysis (a very short
"Beep" every couple of seconds), one can
clearly identify a radar signal. With this set-
ting and the LogPer antenna you can identify
the direction of the source of the signal.
Switch to "Peak Hold - Fast" and direct the
LogPer antenna towards the signal emitting
source. Wait for several circles of the radar
ray, move the instrument a little left and right
in order to get the relevant maximum read-
ing.
The long delays between pulses may con-
sume a great deal of time trying to detect
signal direction with a LogPer aerial. The fol-
lowing drawing shows the connection:
Depending on the type of radar, the average
level can be up to 10 dB or 10 times lower
than the actual peak power density, some-
times even more. To be on the safe side one
should multiply the radar peaks (i.e. peak
minus background radiation between pulses)
by ten and compare this value with limits or
recommendations.
The HF58B-r and HF59B HF Analyzer's con-
tain patented circuitry specifically designed
Peak Hold - Fast
Radar Signal
Peak Value
Page 9