5988 RadioScan Spectrum Analyzer
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5.7 Spectrogram View
The default view of the RadioScan program is the Spectrogram view. The Y axis represents the
amplitude of the radio energy on any frequency across the X axis.
The cross hair cursor
shows information as you move it around the screen.
The crosshairs of the cursor show the frequency across the X axis, the amplitude of the point
where the cursor is on the Y axis, the density of that frequency, the current amplitude reading
of that frequency, and the average, and maximum amplitudes over the previous two minutes,
for that frequency.
Although the Spectrogram is two dimensional, color provides a third dimension of analysis. The
color of the Spectrogram describes the density of radio energy on each frequency. Density is
described as
the percentage of time a specific amplitude of radio energy was measured on a
specific frequency during the immediately preceding two-minute period. Density can be
expressed as colors, like the chart on the upper right side of the RadioScan Spectrogram View
screen. Density is an important tool in analysis of the broadcast spectrum.
Blue designates a radio signal of short duration, like a frequency hopping radio, and means the
frequency has been utilized less than 6.25% of the time during the last two minutes. This may
signify a radio signal of high amplitude, but very short duration, like wireless DMX. Cyan
designates the frequency was used slightly more of the time, with green, yellow, and orange
progressing to higher usages of time over until reaching red, which shows the frequency was
used more than 50% of the time over the two previous two minutes. This is a rolling two-minute
calculation that updates automatically as conditions change.
Generally, when looking for a suitable place to put a broadcast, look for areas with more blue and
less red. Areas of high amplitude and high density should be avoided. An area of low amplitude
and high density represents a noise floor that your signal would need to overcome to be
successful.
Spectrogram view often changes over time. By dragging the scan bar at the bottom of the
screen, you can scroll back through your scan to quickly see changes in the environment. This is
valuable in diagnosing the source of broadcast problems.