These signals are illustrated as vertical bars on the display. Our previously deter-
mined rule applies here too: the higher the
signal strength
, the higher the bar.
More precise information about the individual bars is shown from left to right as
markers
in the upper part of the display. On the left,
marker 1
(the leftmost bar)
indicates a frequency of 16.7Hz at -63dBm. In the centre,
marker 2
(second bar
from the left) indicates 50Hz at -23dBm. Finally,
marker 3
(the rightmost bar) dis-
plays 350Hz at -42dBm.
Remark: the configured
frequency range
is constantly being analysed. Thus,
the display will keep changing all the time. This process is called
sweeping
.
What information did we get from the entire process?
1.) In the entire frequency range from 0 to 400Hz there are 3 main signal
sources.
2.) The frequencies and signal strength of all 3 signal sources are exactly
known.
As the exact frequencies of the signal sources are now known, it is now
easy to determine the actual entity or service emitting the signal by using
a so-called frequency table (see also the frequency table on page 56, or the
more exhaustive frequency tables on the Aaronia homepage).
Using these frequency tables, we can determine the source of our 16.7Hz
signal as follows:
16,7Hz = Traction power
In other words, we are dealing with an overhead line or similar railroad
installation.
Firmware V 1.0 / © 2005-2013 by Aaronia AG, D-54597 Euscheid, www.aaronia.com
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19.0 Spectrum analysis basics
