User manual

Digital High Frequency Analyser HF58B-r
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany Revision 4.5 (Febuary 2006) Page 8
In everyday measurement practice this func-
tion has great value. The peak value is re-
lated to the actual signal situation. This is
important because the immission situation
can change rapidly with time, direction of the
radiation, polarization, and the points of
measurements.. The “Peak Hold” mode
guarantees that you do not miss single
peaks.
The tone signal works independently of data
collection in the peak hold mode. Its sound is
proportional to the actual value measured. It
helps to identify the location, direction, and
polarization of the maximum field strength.
You can chose the (inevitable) droop rate, at
which the held peak value decreases over
time. Set the switch below the signal evalua-
tion switch (recessed in the casing) to “Slow”
or “Fast”. In “Slow” mode it takes about 20
minutes to run out of tolerance, but in order
to get an accurate reading the display should
be checked frequently. If very short signal
peaks occur then the holding capacity of the
function needs some recurrences to load
fully.
Setting:
LF-Processing - Video Bandwidth
The video bandwidth defines the minimum
duration of short pulses that still can be
measured by the meter without being dis-
torted.
For measurement of exceptionally short
pulses (e.g. Radar) or specific signals like
UMTS/3G an extremely high video band-
width is needed for accurate readings. The
HF58B-r allows for 2 MHz video bandwidth,
an unparalleled high value which guarantees
the best accuracy available on this sector.
Use the setting “TPmax” only
for measur-
ing radar and UMTS/3G signals, as along
with the high video bandwidth comes a
higher noise level as illustrated in the picture
below.
low Noise
UMTS (3G) and
Radar readings
displayed too small
higher noise
ideal for Radar
and UMTS (3G)
"low"
(e.g. 30 kHz)
Video-
bandwidth
"high"
(e.g. 2 MHz)
The standard setting therefore is “TP30kHz”.
Only if a Radar signal or UMTS (G3) signal is
detected, by means of the audio analysis,
the “Tpmax” setting is used.
Some technical background
The circuits processing the incoming high
frequencies are only a small fraction of the
total circuitry. Their output is a signal propor-
tionate to the power density in the frequency
of the modulations or the pulses of the in-
coming HF signal, i.e. an LF signal in the
broadest sense.
The video bandwidth is important for the po-
tential as well as the limitations of an instru-
ment. Your HF analyzer allows you to select
between two settings of bandwidth, depend-
ing on the objective of the measurement:
- TPmax (Radar):
With this setting the full 2
MHz bandwidth is at your disposal. Select
this when you have identified Radar or a
UMTS/3G signal by audio analysis. Please
note that with this setting not only the
UMTS/3G and the Radar signals are
measured, also any signals from other
sources in this frequency range. With this
setting TPmax and
the range selector
“fine” the noise can be up to a value be-
tween 30 and 120 digits. The tolerance
level of bandwidth and associated noise is
wide, but the bandwidth is beyond 2 MHz
minimum. A high noise level indicates an
even higher bandwidth of the instrument
6
.
Please note
: In view of the unavoidable
higher noise associated with the high video
bandwidth one should not use TPmax as
standard setting.
- TP30kHz (Standard): This should be the
standard default setting for general pur-
pose use of the instrument. The video
bandwidth is about 30 kHz, which will rep-
resent the shortest continuously pulsed
signals (e.g. DECT) without distortion. At
the same time, even with the range switch
on “Fine” the noise is significantly less than
with TPmax.
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When the setting “Tpmax” and “Peak Hold – slow” is
chosen the reading on the display will at first rise for a
few second or even minutes, as also minute stochastic
peaks will be picked up and retained, which in normal
processing would be just “averaged out”. After some
time some slightly varying state of equilibrium will be
established.