© Gigahertz Solutions GmbH
17
Made in Germany
Audio Analysis of Modulation
The audio analysis of the modulated portion of the HF signal helps
to identify the source of a given HF radiation signal. There is a se-
lection of audio samples on our homepage (under RF and EMF Me-
ters/ High Frequency).
Important:
For the audio analysis please set the switch on the right
of the display to “Pulse” in order to eliminate acoustical markings
(“rattling” with 16 Hz) of unpulsed signals.
How to proceed:
For audio analysis, simply turn the volume knob of the speaker at
the top of the case all the way to the left (“-”). If you are switching
to audio analysis while high field strength levels prevail, high vol-
umes can be generated quite suddenly. This is especially true for
measurements which are to be taken without audio analysis. The
knob is not fastened with glue to prevent over winding. However, if
by accident you should turn the knob too far, simply turn it back
again. No damage will be caused.
Sounds and signals are very difficult to describe in writing. The best
way to learn the signals is to approach known HF sources very
closely and listen to their specific signal patterns. Without detailed
knowledge, the
characteristic signal patterns
of the following HF
sources can be easily identified: 2.4-GHz telephones as well as cel-
lular phones, the signal patterns of which can be divided into “a live
connected phone call“, “stand-by mode“ and especially the “es-
tablishing of a connection“. The typical signal patterns of a cellular
phone base station can also be identified this way. For comparison
reasons you are well advised to take measurements during high-
traffic times, as well as some times during the night, in order to
familiarize yourself with the different noises.
The volume can be controlled with the “audio” knob. Note: The
power consumption of the speaker is directly proportional to the
volume.
For a quantitative differentiation of the various radio services, we
can offer selective frequency filters.
Analysis of the modulated / pulsed signal compo-
nent (Full/Pulse)
The little switch at the right of the display allows to distinguish be-
tween the complete signal including the pulsed part and its pulsed
or modulated part only.
As most of the presently used signals have a modulation of 100%,
there is mostly only little difference between the two switch set-
tings. Especially in the case of very low field strengths (only few
µW/m²), we recommend to use the “Pulse” setting as the instru-
ment noise is more than a factor 10 lower in this setting than in the
“Full” setting.
Marking of CW signals
Un-pulsed signals by their very nature are not audible in the audio
analysis and therefore easily missed. For that reason they are
marked by a uniform “rattling” tone, with its volume proportional to
Содержание HF58B
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