CD42 Pipeline Pig Location & Tracking System
Page 57
With the antenna perpendicular to the pig, an exact location can now be determined. The waveform
signals will now be the reverse of a parallel orientation. As the operator moves the antenna closer to
the pig the signal strength drops until reaching the null (Figure 84), or point of little or no signal,
when the antenna is directly over the pig. Move the antenna back an inch or two, and the signal
strength will rise. Move farther away and the signal will disappear altogether. With this technique, the
operator can pinpoint the exact location of the pig.
Figure 84 Nulling the transmitter
As a side note, be aware that the operator must have already located the general vicinity of the pig using
parallel orientation of the antenna. Transmission range is severely limited with a perpendicular
orientation and is not suitable for random pig location.
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