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For the compensation of the crest factor multiply the displayed read-
ing by a correction factor. A flat factor of 10 offers a good approxi-
mation
13
.
Often you will find different telecommunication services performing
at the same time. With the help of the audio analysis, you will be able
to estimate how much of the total value shown is caused by such
high crest factor signals.
Depending on the proportion to the total signal, please apply the fol-
lowing “rules of thumb” for corrections:
Slightly audible portion of “high crest factor signals”: multiply dis-
play reading by 2.
~“Fifty-fifty”-ratio:
multiply display reading by 5
Dominating “high crest factor signals”:
multiply display reading by 10.
This adjusted measurement value can now be recorded or compared
directly to the building biology recommendations. Taking into ac-
count the multiple external factors of measurement uncertainty, this
approach is perfectly adequate for an assessment of the total pollu-
tion. The use of a frequency filter and service specific correction fac-
tors will allow an increased accuracy.
14
Please note: In the combination of the settings "VBW Maximum",
"Range: min"
and
"Peak hold" the the background noise level can
sum up to a value of 1.00 or more on the display
15
. In order to reach
lower levels you can use the preamplifier HV10.
For obvious reasons the use of a correction factor only makes sense
for readings above the noise level.
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 only be detected every couple
of seconds, for a few milliseconds. This requires special measure-
ment technology.
For an acoustic identification of a radar signal (a short “beep“ which
in extreme cases is only repeated approx. every 12 seconds),
please proceed as follows:
Select setting “VBW Maximum”. Set signal switch to “Peak hold” and
direct the LogPer antenna towards the signal emitting source. Wait
tor. For practical reasons one can nonetheless use the convenient "Peak hold" set-
ting, as with "VBW standard" the readings for RMS and Peak won't differ signifi-
cantly for the signals in question.
13
Even if the standards of these radio services specify far higher crest factors, the
industry is striving for crest limitation for economic reasons, so that in the longterm
the resulting correction won’t exceed a factor of 10.
14
For the time being with a pure LTE signal (very rare) a factor of 20 may still occur
at the peak. For TETRA a factor of 2, and for WLAN (“standby-rattling”) a factor of 4
will be enough.
15
Inherent to the system: The higher the video bandwidth, the higher the displayed
noise level.
Summary of Contents for HF59B
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