Whites TDI BeachHunter User manual

Owner’s Manual
TDI
BeachHunter
White’s Electronics, Inc.
Sweet Home, Oregon USA
Building the World’s Finest
metal detectors for over 60 years.

2
CONTENTS
Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Batteries and Charger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
QuickStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Principles of Pulse Induction . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Controls
Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Power/gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Pulse Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Target Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Ground Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
TDI In Depth
Ground Balancing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Pulse Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Dual-eld coil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Dealing with Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Specications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Code of Ethics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Back Cover

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Cam lock
Clevis
Rubber washers (2), ber bolt
Search coil
Lower rod
Arm cup
Battery door
1. Remove all parts from the shipping carton and check assembly
diagram to ensure all parts are present.
2. Install black rubber washers on ber clevis/lower rod, insert
clevis lower rod onto loop ears. Use only nonmetallic wash-
ers, ber bolt, and ber thumb nut to secure loop/search coil
to clevis/lower ber rod.
3. Unlock middle rod cam-lock and insert clevis/lower rod into
middle rod so that stainless steel spring clip buttons line up
and lock into one of the adjustment holes in the rod. Turn
cam-lock to secure. The second or third adjustment holes are
suitable for average sized adults.
4. Wind the loop cable around the rod assembly, rst revolution
over the top of the rod, all the way to the top of the middle
rod, about ve revolutions. Use the black cable retainers, one
near the loop, and one near the top of the middle rod, to hold
the loop cable in place. Make sure the cable is wrapped all
the way to the front of the control box.
5. Grip the instrument by the handle, with your arm in the
elbow cup with strap and sweep the loop/search coil over
Assembly

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the oor. If the instrument t feels uncomfortable, readjust
clevis/lower rod length with spring clip button and cam-lock
so that search coil can be held near the oor without stooping
over.
6. Remove the protective paper from the two black arm cup
foam pads. Carefully align pads on the inside of the elbow
cup, one on each side of the center rod, and press rmly into
place.
7. Adjust the elbow cup strap so that it is loose enough for you to
slide your arm in and out without loosening each time you
want to set the detector down. The elbow cup strap provides
extra leverage and control. However, some prefer not to use
it.
8. Install the battery pack; see the next section for information
on batteries and charging.

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Batteries and Charger
The TDI-BH includes a rechargeable NiMH battery pack as
the primary power source, and a standard alkaline battery pack
as a backup. Fully charged, they supply a nominal 12 volts (the
NiMH may be slightly less) and will power the TDI-BH for
about 4-6 hours. The TDI will operate until the batteries drop
to about 8.5 volts, at which point the low battery LED will turn
on.
A drop-in charging cradle (Part Number 509-0036) is used
for recharging the NiMH battery. With the wall transformer
connected to the cradle and plugged into a wall socket, simply
drop the NiMH pack into the cradle. An LED indicates the
status of the charge cycle; when the LED turns off, the charge
cycle is complete and the charger will automatically switch to
a trickle mode. A typical recharge time of a depleted NiMH
pack is 1-2 hours. It is normal for NiMH batteries in storage to
slowly lose their charge over time; be sure to top off them off
before going out.
The alkaline pack is designed so that it cannot be used with
the charger, and trying to recharge alkaline batteries can cause
them to burst and leak. Individual NiMH batteries can be used
in the alkaline tray; it is recommended that the batteries be re-
moved and charged using the manufacturer’s charging system.

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QuickStart
1. Ensure machine is adjusted for comfortable t and use.
2. Set the Frequency offset to the midpoint.
3. Set the Ground Balance to 6-8.
4. Turn on the power and adjust the Gain to “2.”
5. Adjust the Threshold and Volume to achieve a faint back
ground hum.
6. With the coil on the ground (no motion) increase the Gain
until the audio begins to chatter. Back off slightly for a
reasonably smooth threshold.
7. Optional: adjust the Frequency offset to minimize the amount
of chatter.
8. Using a spot free of targets, bob the coil up & down and
adjust the Ground Balance control to minimize the audio
response.
9. In heavy salt or mineralization it may be necessary to adjust
the Pulse Delay to around 15-20us.

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TX
RX
Exponential decay
No target
Raw Response
The Pulse Delay control, which determines the point where
the decay is sampled, can be used to eliminate low conductive
targets such as thin foil. Further increasing the delay can knock
The use of high-powered impulses results in better ground
penetration than VLF, especially in highly mineralized soil. This
makes the PI detector the best choice for certain kinds of hunting
in bad ground where many VLFs simply won’t work.
There is no traditional discriminator in PI detectors, although
there is some ability to discern certain types of metals. The decay
response varies with target conductivity (plus other characteris-
tics) so that low conductive targets have a fast decay and high
conductive targets have a slow decay:
Low-conductive target, fast decay
High-conductive target, long
decay
Principles of Pulse Induction
Pulse induction (PI) detectors are very different from tradi-
tional induction-balance (VLF) designs. Instead of transmitting
a continuous-wave magnetic eld, the PI detector periodically
transmits brief impulses of magnetic energy. The PI receiver
then looks at the impulse decay for target (and ground) infor-
mation.
Pulse Rate

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out other minor trash targets at the expense of eliminating po-
tentially good targets such as jewelry, but this method is very
limited in the range of trash targets that are rejected.
Furthermore, the ground balancing method used by TDI has
a side affect with target responses. Target conductivities below
the ground balance point produce a positive response for which
TDI assigns a high tone. These targets are generally low con-
ductive such as small nuggets, jewelry, and small iron. Target
conductivities above the ground balance point produce a nega-
tive response for which TDI assigns a low tone. These targets are
generally high conductive such as silver coins, relics, and large
iron.
Low-conductive target
No target
High-conductive target
Ground balance point
Differential Response
The Target Conductivity switch can be used to eliminate either
class of targets, or to accept them all. Care should be used with
this feature as it is not always obvious as to how a target might
respond. Testing with known targets is the best way to learn the
responses.

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Controls
Threshold
The Threshold control sets the level
at which the background audio tone is
heard. In most cases, faint target signals
are easiest to hear when the threshold is
set to a low but clearly audible level. A
higher threshold level can result in audio
fatigue. Too low of a threshold level
means that a stronger target signal is
required to produce an audible change. Threshold is best deter-
mined at a low gain setting where there is no chatter.
The threshold can be set low enough to effect a “silent
search” audio. Some people prefer silent search to prevent audio
fatigue. If you choose to do this, increase the threshold to the
point where you can hear the threshold tone, then slowly back
off until it is barely inaudible. Reducing the threshold any more
than necessary requires stronger target signals to produce an
audio response. Other controls — including Gain, Ground Bal-
ance, and Frequency offset — are best adjusted with an audible
threshold.
Power/Gain
The Gain control increases or decreases the amplication of
the receive signal. Normally, this deter-
mines how deep the detector will “see”
a target.
However, increasing the gain not
only increases the amplication of tar-
get signals, but also that of ground
signals and electromagnetic interference
(EMI) as well. A common mistake is to
assume

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that higher gain will always give better depth. In air tests this is
generally true, but ground results can depend on the amount and
type of mineralization.
With the coil on the ground, increase the gain until the
detector exhibits chatter, then back off slightly for a reasonably
steady threshold tone. Use the Frequency offset control to help
deal with EMI-related chatter, and proper ground balancing will
minimize chatter due to mineralization.
The Gain control is also used to turn the detector on and off.
Pulse Delay
TDI transmits a pulse and then, after
a short time delay, samples the received
signal. Pulse Delay allows this time
delay to be adjusted from 10μs (micro-
seconds) to 25μs.
In response to a transmitted impulse,
all targets exhibit a response
with an exponential decay. Regardless of
conductivity, the response is strongest at low sample delays and
weaker at higher delays. However, targets of low conductivity
or that are thin will decay faster than highly conductive or thick
targets. See the Principles of Pulse Induction section for more
details.
Smaller gold nuggets fall in the former category, so nugget
hunters will want the Pulse Delay set as low as possible. Coin or
relic hunters may want to increase the delay to knock out thin
foil trash and still detect desirable targets. Most iron (especially
larger) responds with a long decay and is usually not very re-
sponsive to the delay setting.
Conductive salts also respond with a fast decay and can be
detected at low delay settings. If beach hunting in wet salt sand,
you may need to turn the delay up to 15μs to eliminate the salt
response. Dry salt is usually not a problem, so as you move out
of the wet sand into dry sand remember to turn the delay back
down to better detect small jewelry items.