Air-Coupling - RIDGID SeekTech ST-33Q+ Operator's Manual

Air-Coupling

Any transmitter in Inductive Mode generates a field
through the air around it; including the ground under-
neath. If within air-coupling range of the ST-33Q+, the
receiver will measure this field instead of the target con-
ductor. Air-coupling will distort readings and misconstrue
the location of the target conductor.
Air-coupling effects can dominate the received signal
over a wide range (greater than 20 m [70 ft]) if the in-
duced utility is deep and poorly grounded. Very weak in-
duction and deep utilities will result in greater air-cou-
pling distances. Always confirm the detection of utilities
and the readings of depth measurements.
Air-coupling does not depend on the output power of the
transmitter and cannot be reduced by turning down the
power. Air-coupling only depends on the ratio of the field
from the transmitter compared to the induced field in the
target utility.
The effect of air-coupling can vary continuously so be
aware of the difference between the transmitter's field
and the induced field of the utility being traced. While
both will have the same frequency, the transmitter's field
is only strong enough to obscure the utility's signal in the
region around the transmitter itself.
Be sure to look overhead for power lines that could also
confuse the locate.
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Testing for Air-Coupling
To test for air-coupling, tilt the locator at a 45 degree
angle towards the ST-33Q+ and ensure the lower an-
tenna of the receiver touches the ground. Afterwards, tilt
the receiver 45 degrees away from the ST-33Q+ and ob-
serve the depth reading. If the depth reading changes
significantly, air-coupling may be affecting the accuracy
of the locate.
Alternatively, test for air-coupling by standing 6 m [20
ft] away from the ST-33Q+. With the lower antenna on
the ground, take note of the indicated depth measure-
ment on the receiver. Raise the receiver vertically 45 cm
[18 in] and observe the change in the depth indication. If
the receiver only reads the conductor, the depth should
increase accordingly. If the receiver is air-coupling, the
depth indication will not change by 45 cm [18 in], but will
change disproportionately.
Using the Kick Stand in Inductive Mode
In Inductive Mode, the kick stand can be used to aim the
output field and maximize the intersection with the con-
ductor, while also reducing the field's intersection with a
nearby known conductor.
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