Husqvarna Automower 420 Technical Manual page 13

The strength of the loop signal varies depending on
the distance to the wire. The strength of the signal is
high right next to the wire. The strength subsequently
diminishes the farther away from the wire you get. The
Signal quality reading determines whether the signal
from the boundary wire is strong enough for the mower
to be in working order. Signal quality should always
be 100% for satisfactory function. Outside the wire the
signal is negative and its strength diminishes more rap-
idly. The signal from the boundary wire is designated
the A signal. See the illustration below for examples of
high and low signal strengths
The strength of the A signal also varies along the
boundary wire depending on the proximity to other
parts of the loop. The strength of the signal is affected
by the size of the working area, islands, headlands,
passages and corners. The signal can also be affected
by magnetic objects in the ground or in nearby walls
and buildings. The signal is weakened in these areas.
Examples of magnetic objects are iron fences, iron gird-
ers and reinforcement bars. Grass areas laid on con-
crete roofs can therefore receive a weakened signal.
When the signal is reinforced or weakened, it is normal
that both low and high signal strengths are not always
available along the entire boundary wire.
The loop signal's reception and amplification in the
mower can also vary by +/- 10% from one mower to
another. This means that at the same point in an instal-
lation, one mower can display A=90 and another one
A=100. The charging station's circuit board and the
mower's loop sensor can also give certain variations
between different machines.
See 2.2.1 Info for more information on how the loop
signal can be read in the mower's display.
1. FUNCTION
160
100
40
Cable
100
80
60
15 m
English - 13