in line trace basics we showed you the fundamentals of operating the receiver
and using it to trace a signal in this segment we'll demonstrate some advanced
tips and techniques that will help you get more out of your equipment here's a
technique that can help you evaluate a signal for distortion we'll demonstrate
this technique using the same location and connection point we used in line
trace basics will acquire the signal sender the tracing line and align the
receiver with a signal just as we did before there are a few basic questions
we want to ask as we look at the display first is the depth reading in a
reasonable range for this utility at this location is the tracing line sharp are
the tracing line and guidance arrows centered at the same time when we sweep
across the target signal do the tracing line and guidance arrows track smoothly
the depth does seem reasonable for this location but the tracing line is a bit
fuzzy the tracing line and guidance arrows moved smoothly across the screen
but they're not centered at the same point so it looks like we definitely
have some amount of distortion we're close to the transmitters leads and the
line turns after just a few feet both of these things are sources of interference
so we'd expect to see some distortion to get a feel for how much signal
distortion we're dealing with we'll look at where our display readings place the
signals location we'll start with the guidance arrows in this case we can
Center them by moving the receiver just a few inches which is a good sign
next we'll focus on the proximity signal and the signal strength we're looking
for the point where each reading is highest we're also looking for agreement
between these two readings in between these readings and either the tracing
line or guidance arrows
these two readings agree with each other and with the guidance arrows which means
we have 3 independent readings that are in substantial agreement with each other
as a final check we'll lift the receiver by a foot or so to see if the depth
increases by the same amount which it does let's summarize what we've just
observed three of our signal readings largely agree with one another
the fourth is only off by a small amount and when we raise the receiver the depth
increases by an appropriate amount based on these observations we can conclude
that the signal is only mildly distorted if we were marking this utility we'd
first try to minimize the signal Distortion if we couldn't we would base
our marks on the 3 readings that agree
when the utility you're tracing makes a sharp turn like it would at a tea or an
elbow the signal can become distorted at that point causing the tracing line to
lead you outside the utilities actual path this effect can vary but you'll
generally find that it's more pronounced at higher frequencies and on sharper
turns rather than on sweeping turns which can often be traced normally
here's an easy technique for marking sharp turns
as you approach the turn the tracing line will rotate significantly this is a
good indication you're dealing with a sharp turn rather than a sweeping turn
let the tracing line guide you around the turn once you're past the turn stop
and pinpoint the signal with a guidance arrows proximity signal and signal
strength dot the line and then go back and get the other side of the turn using
the same technique to mark the turn find the point where the two legs of the line
intersect
the sr20 sophisticated audio system provides feedback to help make locates
fast and intuitive the audio pitch is tied to the proximity signal it
increases when the proximity signal increases
and decreases when the proximity signal decreases the audio clarity reflects
signal distortion detected by the tracing line when the tracing line
appears sharp the audio will sound clearer
when the tracing line is fuzzy the audio will contain static the guidance arrows
also have special audio tones associated with them when the signal is on your
right you'll hear the normal audio tone
when the arrow passes over the crosshair you'll hear a double bead and when the
signal is on your left you'll hear a pinging tone along with the normal audio
these tones let you work without having to keep your eyes glued to the display
with the sr20 you can follow a signals path even when you're not directly over
it just point the receivers mask towards the signal and keep the tracing line
roughly centered on the display now you can follow the signals path safely from
the curb and only step into the street when it's safe to do so so you can
verify the signal and place your marks
in addition to tracing signals that are actively applied with a seektech
transmitter the sr20 receiver can trace passive signal energy that originates
from sources like powerlines radio and television broadcasts and electronic
devices passive locating is generally regarded as a last resort means of
locating a line and is often used to conduct blind sweeps of an area when
there are no topside indications that a utility may be present passive tracing
with the sr20 is easy you'll use the same signal readings as you do for
active signals and they work the same way
types of passive locating modes the passive power mode can be used to locate
the narrow range of frequencies produced by power transmission lines
simply select 60 Hertz power mode from the frequency menu and you're ready to
go the sr20 has several different frequency options for power mode or
details on these options refer to your operators manual
the second type of passive locating mode uses patented broadband technology to
search for signal energy within a range of frequencies the sr20 has three
broadband ranges the lowest range covers frequencies below 4000 Hertz and the two
radio frequency or RF ranges cover four thousand to fifteen thousand Hertz and
fifteen thousand Hertz and above the sr20 also has a special broadband mode
called omniseek when set to Omni seek the receiver will search for signal
energy in all three broadband ranges simultaneously and display a tracing
line for each range that has a usable signal the signal range that's closest
to the receiver takes precedence the range will be displayed above the Omni
seek icon on the receivers display and the bold tracing line and other display
readings will reflect that signal with Omni seek blind searches are fast
because you're looking at all three broadband ranges simultaneously when you
see evidence of multiple signals you can switch to the individual broadband
ranges and trace each one separately
after performing an active locate you can use the sr20 s omniseek passive mode
as a final check to see if additional utilities may be present in this example
our technician is marked gas and power lines that share a common trench as a
final check he'll switch to omniseek mode and sweep the locate area outside
the trench
he picks up a signal a few feet to the left of the trench
the signal is in a high RF range so he'll switch to that range and begin
tracing the signal
although there's some distortion the signal is solid and he's able to trace
it right up to the building
by gaining access to the building he is able to energize the phone line with an
active signal and then perform an active trace through the locate area to verify
its position