Boltek NexStorm Lite User Manual
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Lightning Detection Software, Version 1.0
Why differentiated night time ranging is useful
Lightning detectors such as the Boltek StormTracker and LD-250 are subject to radio signal propagation laws.
When a lightning strike occurs it will emit an radio signal pulse, a wave, that will propagate towards the
detector antenna both as a ground wave and a sky wave. A sky wave is basically a wave that was “bounced
off” the Earth's ionosphere at least once. This will enable the wave to propagate much further than it would if it
were a ground wave.This phenomenon is well known among amateur radio enthusiasts, enabling them to
communicate across great distances when conditions are favorable.
The ionosphere consists of several layers called D, E, F1 and F2, where the D-Layer will absorb sky wave
signals in certain frequencies during daylight hours. The F1/F2 layers, commonly referred to as the F-layer, is
in effect reflecting these waves, bouncing them back towards earth with minimal attenuation. Shortly after the
sun sets, the D-Layer will begin to dissipate and this will allow the higher F-layer to reflect those waves that
were previously being absorbed by the D-Layer. Under certain conditions and especially during night time
hours, lightning signals from very distant thunderstorms can therefore “sky-hop” their way to your antenna by
bouncing between the F-layer and the ground one or more times. This is generally not a problem during the
day because the majority of the lightning signals are ground waves, the sky waves being effectively absorbed
by the D-layer.
Occasionally you may therefore observe more or less well defined storms appearing relatively close to your
location while the actual thunderstorm that is generating the lightning is located much farther away, often
outside the range of the map. If you see this phenomenon then the most probable explanation is that the
atmospheric conditions are favorable for sky wave propagation
The Nighttime ranging upshift can partially or fully compensate the incorrect ranging that occurs with some of
these distant thunderstorms but you should not expect it to be accurate all the time. The NexStorm ranging
formula becomes more error prone at greater distances because of the reduced amounts of captured
lightning signals, but there are also other factors which will influence the performance of the Nighttime ranging
upshift feature, such as daily and seasonal variations in atmospheric conditions and/or surrounding terrain.
The ranging upshift will activate at sunset and gradually be applied until full effect is reached around 30
minutes after initial activation. Similarly, after sunrise, the upshift effect will be gradually reduced and reach
minimum/switch off level after around 30 minutes. If the latitude, longitude and UTC offset are all set correctly,
the times at which Nighttime ranging upshift activates and deactivates will correlate rather well with the
dissipation and formation of the D-Layer.
The optimal values for Range shift and Boundary will be different for different locations but may also vary for
the same location on different days.
Edition: 5/L1
2007-09-02
© 2007 Astrogenic Systems
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