Whites GARRETT GOLDMASTER 24k User manual

Original GM24k detector
USER MANUAL

Assembly................................................................................................ 3
Batteries................................................................................................... 5
GM24k Quick Start Guide................................. 6
Controls ....................................................................... 8
Sensitivity Control..........................................................8
Sensitivity Adjustment................................................8
Volume / Threshold Adjustment ..........................10
Hot Rocks ............................................................................11
Variable SAT Speed Control.....................................11
SAT Adjustment...............................................................11
Target ID...............................................................................12
Audio Modes.....................................................................12
Iron Cancel (Discrimination)....................................13
Iron Cancel Adjustment.............................................13
Ground Balance Controls / XGB............................14
TracLock/Ground Grab...............................................15
Ground Scan......................................................................15
Searching....................................................................16
Pinpoint Techniques.....................................................16
Headphones .....................................................................17
Field Use and Tuning Tips .........................................18
Information.........................................................................................23
Proper Care.........................................................................23
Warranty ..............................................................................24
Goldmaster 24k Contents
2Garrett Metal Detectors
e Garrett Goldmaster® 24k (originally produced
by White’s Electronics) is a high-frequency induc-
tion-balance gold nugget detector. e GM24k
features a 54% increase in coil voltage over the
prior White’s GMT model, resulting in increased
sensitivity to small nuggets.
While testing this machine in Brazil, this was
shown in a tiny, 0.4 grain crystalline nugget found
encased in quartz. In some cases this much power
canbe challenginginareaswithheavilymineralized
soil. Even at lower gain settings, the GM24k is an
extremely “hot” machine on small gold and spec-
imen nuggets.
Experienced prospectors know more sensitivity
is not the only answer to increasing the odds of
success. A machine’s ability to track and cancel the
ground is oen the biggest challenge faced in the
search for gold. at’s why the Goldmaster® 24k
features a special ground tracking system called
“XGB” (Xtreme Ground Balance). It works with
multiple ground points to ensure stable operation.
e GM24k also features Iron/Hot-Rock cancel-
lation in both audio modes, which expands the
ground range even more for quiet operation in the
most challenging ground.
When the nuggets are few and far between, pros-
pectors sometimes have more success at sluicing,
panning, or dry washing. e GM24k Ground
Scan feature can help successfully track and mark
black sand or other mineral deposits in stream
beds, washes, or even under ground (where the
backlight comes in handy).
Other key features such as Variable Self-Adjusting
reshold (vSAT), Ground Grab, TracLock, and
adjustable audio options help users to set up the
machine as desired, based on ground conditions
and personal preference. Garrett believes in giving
the ability to adjust a machine for a wider variety
of conditions, hopefully resulting in more gold in
your pouch.
Reading this guide is a great way to get started
with your GM24k, but there truly is no substitute
for time spent out in the eld with the machine.
Maximize your success by learning the features of
the detector and also its language. With a combi-
nation of patience, research, and a little luck, you’ll
get your GM24k’s coil over gold.
Good luck and happy hunting!
Introduction

GM24k Assembly
Goldmaster 24k User Manual 3
Assembly Instructions
1. Remove all parts from the shipping carton and
check the image on the next page to make sure all
parts are present.
2. Unlock “S” stem camlock and insert the
reduced end of the middle stem into curved “S”
stem so that stainless steel spring clip buttons line
up and lock into the holes in the curved “S” stem.
Turn camlock to secure.
3. Fit the rubber washers between the lower
stem and searchcoil ears. Use only non-metallic
washers, ber bolt, and thumb nut, to secure loop
to the lower stem. en insert into middle stem
so that stainless steel spring buttons line up and
lock into one of the adjustment holes in the middle
stem. Turn camlock to secure.
Assembly
3
4
1
2
5
Garrett GM24k contents:
1. S-shaped stem
2. Middle stem
3. Lower stem
4. Searchcoil
5. Control box
6. Armrest with armrest strap
7. 8x AA holder
6
7
Detail on
Step 3

4Garrett Metal Detectors
4. Unravel the cable and wind it around the stem
assembly. e rst revolution should be OVER the
top of the stem with a small amount of slack. is
is done so that the searchcoil can be paddled back-
wards toward the stem without putting a strain on
the cable. Wind cable rmly all the way to the con-
nector on the back of the control box.en plug
connector into control box and turn lock ring to
secure. To secure cable, wrap Velcro cable retainers
around stem and cable, one near the searchcoil and
one near the handle.
Optional: prevent scraping your detector box by
adhering the included pair of peel and stick rubber
feet to bottom side of box.
5. Grip the detector by the handle, with your
arm in the elbow cup with strap secure, and
sweep the coil over the oor. If the detector
t feels uncomfortable, adjust the elbow cup by
removing and repositioning the bolt and install-
ing in one of the optional positions. If necessary,
readjust clevis/lower stem length with the spring
clip buttons so that the search coil can be held near
the oor without requiring stooping over.
6. 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.
7. Install battery with plastic tab and steel contacts
facing toward inside of battery compartment. e
24k ships with a set of eight rechargeable batteries
that may require charging before use.
8. e detector may not work as expected indoors
due to the high degree of metals (nails, pipes, etc.)
used in modern construction and the presence of
electrical interference. It is best to tune and prac-
tice outdoors to ensure stable and more predictable
results.
Headphones subject
to change
Not shown: warranty card
and quick art guide
GM24k Assembly
Lower and middle stems
Washers, nut, bolt
Rubber feet
Headphone adaptor
Velcro cable retainers
Headphone jack du cover
AA battery
recharging kit with
universal adaptors
12v charger cables
for car or battery

GM24k Batteries
Goldmaster 24k User Manual 5
Batteries
Rechargeable vs Alkaline
1. e standard battery holder holds eight “AA”
cell batteries. Garrett includes eight NiMH re-
chargeable batteries and a recharger with the
GM24k. During normal searching conditions,
you can expect about 20 hours of hunting time
from fully charged batteries.
2. Alkaline batteries can also be used in this hold-
er. During normal searching conditions, you can
expect 15 to 20 or more hours of hunting time
from one set of eight alkaline batteries.
3. Headphone use prolongs all battery life. Bat-
tery life will vary a great deal with temperature,
number of target signals, battery type, brand,
and shelf life. When traveling far from home
it is always a good idea to carry eight (8) extra
AA alkaline batteries, plus an extra empty bat-
tery holder.
4. Four bars on the battery icon (see above, right)
indicates fully charged batteries. Replace the bat-
teries when there is only one bar remaining. e
GM24k detector will maintain full performance
with only one bar remaining, but when the volt-
age remaining becomes too low for proper oper-
ation, the battery icon will begin ashing. Once
the batteries get to 8 volts, the machine will turn
itself o to keep from over-discharging the cells.
5. e battery compartment opens by pressing
on the two buttons on the side of the battery box,
releasing the catch and hinging open the door.
Using the Battery Holder
1. Slide open the battery holder lid (decal side of
battery holder) by applying gentle upward pres-
sure on the tab of the door so that it unlocks. Slide
the door away from the battery box exposing the
battery positions.
2. Remove batteries from the holder. Note the (+)
and (-) positions of each cell and the (+) and (-)
for each position marked inside the cell tray. Use
the charger shipped with the GM24k to recharge
the eight AA batteries, or install new alkaline AA
batteries.
Carefully note the correct (+) and (-) positions
when installing AA batteries. If the batteries are
installed incorrectly, the detector may require
service by an Authorized Service Center.
3. Slide the door closed so that it snaps securely.
4. Insert the battery holder into the detector with
enough force to hear the double “click” from the
battery retention clips inside.
Above: battery icon
Left: battery holder

6Garrett Metal Detectors
GM24k Quick Start Instructions
Target ID #
Higher number,
Better chance of gold
Beep Mode On
Iron Cancel On
Volume Level
SAT/reshold Level
Audio Mode
SAT +/-
Volume +/-
reshold +/-
Iron Cancel
Disc LO/HI
Visual Target ID
Ground strength in
Ground Scan mode
Backlight On
TracLock On
Sensitivity
Power On/ O
Backlight
TracLock
Ground Scan
Sensitivity
Adjust other settings
Ground Grab/Exit Setting Selection
Pinpoint (non-motion)
GM24k Interface
NOTE: Regular text = button TAP, Italic text = button HOLD
Battery Condition Indicator

GM24k Quick Start
Factory Reset
Hold when turning on the detector. Press and
hold button when “Fd” is on screen to reset
the machine to factory default.
Goldmaster 24k User Manual 7
1
2
3
4
5
6
7
8
9
10
*
If you attempt to demonstrate or test the
GM24k by waving targets in the air in
front of the search coil, it is ESSENTIAL
to have the GROUND BALANCE toggle
in the LOCKED setting.
is is necessary, for when the GM24k is
in the XGB setting, the searchcoil must
SEE ground while it is passing over the
target or it will think that the target IS
ground and will attempt to track it out.
is is the case whether you are demon-
strating with or without Iron Cancel.
You may, however, demonstrate the fast
ground balancing feature of XGB or
GRAB by waving or pumping a mineral-
ized rock in the air in front of the search
coil.
us, testing the GM24k with targets
while in XGB mode must be done in or
on the ground.
SPECIAL NOTICE
Quick Start
Instructions
With the GM24k properly assembled and the
batteries installed, follow the instructions below to
start nding nuggets.
Turn the GM24k on by pressing the POWER
button.
Set the VOLUME to your preference (tap
Speaker icon, use Up and Down buttons).
Set the THRESHOLD to a faint hum (hold
Speaker icon, use Up and Down buttons). For
silent search, turn this all the way down.
Set the SENSITIVITY to a level that ensures
smooth operation (Up and Down buttons).
Set the SAT (Self Adjusting reshold) to
get a stable threshold (hold Music button, use
Up and Down buttons).
Select your preferred AUDIO mode (tap
Music button). With the Music icon displayed
you are in Beep mode. With no icon, you are
in Zip mode.
Enable IRON CANCEL if you experience
dicult ground conditions, hot and cold
rocks, or iron trash (tap Nail button).
Lower the search coil to the ground, then
“pump” the coil up and down a couple of
times and XGB (Xtreme Ground Balance)
will automatically balance or track out the
ground mineralization. Or you can Lock the
tracking (Lock button) and perform a ground
grab (Bullseye button).
Start swinging the search coil in wide
sweeps that overlap each other.
If you experience false signals or constant
beeping or popping, turn SENSITIVITY
down a bit, adjust the SAT up, or enable
IRON CANCEL.

GM24k Controls
8Garrett Metal Detectors
Current
Sensitivity
Level
Sensitivity
Increase
Sensitivity
Decrease
Controls
Sensitivity Control
With the SENSITIVITY control, you increase the
signal strength coming from the ground. You might
expect increased signal strength to always nd more
nuggets at greater depths. However, high ground
mineralization will “bounce” the signal back and
mask good targets. erefore, adjust SENSITIVITY
to give the maximum allowable sensitivity without
masking targets or overloading the circuit. At the
same time, this allows you to operate the detector
with a constant threshold hum so that faint signals
can be detected.
is is where the GM24k can help you out. When
ground mineralization is too high for the current
SENSITIVITY control setting, the display shows
you a series of lines along with an audible “alert”.
Reduce the SENSITIVITY until the overload warn-
ing ceases. On occasion, while searching, you might
go over a very large or very shallow target. is will
result in the same type of behaviour. Liing the coil
higher may reveal some information on the target.
You still might want to dig it up!
Sensitivity Adjustment
1. e UP and DOWN buttons control the SENSITIVITY. Each press on the UP button increases from a
minimum level of “0” to a maximum level of “10”. Please note that levels 0-9 adjust the system gain, and
that setting 10 enables an Audio Boost for maximum sensitivity.
2. Average ground conditions will generally allow for settings of 5-7 on the SENSITIVITY setting. In mild
ground you may be able to run as high as 10. In extreme ground, you may need to lower the sensitivity
to under 5. If the GM24k overloads, your sensitivity is set too high.
3. One way to look at the SENSITIVITY control is like the accelerator in your car. Sometimes you have to
ease o for better control, and other times you can go “full throttle” for maximum performance.

GM24k Controls
Goldmaster 24k User Manual 9
7. e use of the VSAT (Variable Self-Adjusting
reshold) control will also help to maintain a
smooth THRESHOLD “hum” and will be covered
in a later section.
8. While using a steady slow searchcoil sweep speed,
advance the control towards “10” while main-
taining a quiet smooth background THRESHOLD
“hum”. If ground noises are still a problem, reduce
SENSITIVITY.
9. e TARGET ID capability of the GM24k functions
more accurately when the SENSITIVITY is set at
a level which allows for smooth operation. Too
much gain can cause bad ground to distort the
proper identication of iron and non-iron targets.
10. Just as a slow, broad searchcoil speed will maintain
smooth threshold, it will also allow the searchcoil to
get clear o of the target with each pass, insuring
that the GM24k “sees” ground as well as target. is
is essential for the accurate operation of Target ID.
Sensitivity Adjustment (cont’d)
5. e object of increasing the SENSITIVITY is to get the maximum available depth from the detector
WITHOUT causing the overload message to appear, which indicates an overload of the circuit.
6. In addition, any increase in SENSITIVITY adjustment should NOT BE at the expense of maintaining
a smooth and constant THRESHOLD “hum”. False signals, beeps and bops from bits of mineralization,
erratic behavior, and lapses in THRESHOLD all can be results of running with too much SENSITIVITY.
With the right combination of sensitivity, SAT, and
patience, your GM24k can nd gold down to the sub-
grain size .

GM24k Controls
10 Garrett Metal Detectors
Volume,
reshold
Level
Volume Adjust
(tap)
reshold Adjust
(hold)
e VOLUME control on your GM24k only
adjusts the sound level of target sounds and
conrmation beeps. It is used in conjunc-
tion with the THRESHOLD to give you the
most control over the dynamic range of your
detector. is control is adjusted by tapping
the SPEAKER icon and then using the UP and
DOWN buttons to adjust it louder or quieter.
Note that holding the SPEAKER button adjusts
the threshold, which will display the letters “th”
on screen. Adjust the THRESHOLD so you can
hear a faint hum. is allows for best perfor-
mance on small targets.
For example, with a low THRESHOLD and a
high VOLUME, there is a large range of sig-
nals you might hear. Some will be just above
the threshold; others will bang out loud and
clear. You can adjust VOLUME and THRESH-
OLD to your preference, but in general the best
range of target sounds will be available with
a high volume and low threshold. At volume
levels 9 and 10, you will see “b1” and “b2” on
the display as these two levels enable consecu-
tive audio boosts for low signals.
External Speaker or Headphones?
Volume/reshold Adjustment
ere are advantages to running your GM24k with headphones. Battery life will be increased and it will be
much easier to hear the faintest signals. Wind especially can cause issues with using the external speaker
on a gold detector, as the bueting in your ears can mask small target sounds.
However, in snake country or in hot and humid conditions, headphones may not be an option. e GM24k
has independent volume settings, meaning that you can adjust the volume for the external speaker as well
as the headphones. ese settings are saved when you power the machine down. e GM24k automatically
senses when headphones are plugged in, and the machine will switch to the saved headphone volume level.
It then returns to the saved speaker volume level when the headphones are removed.

GM24k Controls
Goldmaster 24k User Manual 11
SAT Level
SAT adjust
(hold)
Hot Rocks
Hot rocks are mineralized rocks that can
be heard because they are dierent in min-
eralization than the surrounding matrix or
body of ground. Negative hot rocks, such
as magnetite, tend to give a “boing” sound
when the searchcoil is passed over them.
e greater the dierence between them
and the ground, the louder the “boing”.
Positive hot rocks, such as maghemite tend
to sound just like any other metal target,
such as a nugget and can give a zip-zip
sound. Positive hot rocks will test any pros-
pectors patience. e GM24k will reduce
the eect and help to identify many hot
rocks. (More on page 19)
SAT Speed Control
e variable SAT (Self Adjusting reshold)
speed control adjusts the speed that the GM24k
recovers its threshold hum when the searchcoil
passes over changes in mineralization. is set-
ting is adjusted by holding the MUSIC button
and then adjusting the SAT up or down between
0 (o), 1 (medium), or 2 (fast). e letters “Sa”
will display when adjusting SAT.
SAT Adjustment
e Initial Setting is 1(medium), appropriate for
mild-to-moderate ground mineralization. When
you encounter fast changes in ground minerali-
zation or deeper, larger hot rocks, you may either
get false signals (positive ground) or lapses in the
THRESHOLD hum (negative ground). Increas-
ing the SAT control setting to 2will speed up the
auto adjustment of the THRESHOLD “hum” and
reduce this interference. At the same time, you
should slow down your sweep speed to help SAT
do its job to maintain a smooth threshold.
Remember, overall depth will be diminished
with a faster SAT speed, but if the ground is too
noisy to separate a good target from a false sig-
nal, it is better to operate with a little more SAT
speed than to lose a target altogether. is is
the same logic that was used in describing the
SENSITIVITY control. Lowering the gain will
reduce overall depth, but by doing so you can
also improve your performance and nd more
nuggets in the long run. For best results, set your
SAT speed JUST high enough to cancel out false
signals from ground mineralization and set the
SENSITIVITY control JUST high enough to
maintain maximum depth without having false
or erratic behavior.

GM24k Controls
12 Garrett Metal Detectors
Audio Modes
Tap the Audio Mode button (the music note icon)
to toggle between two dierent audio modes. With
the Audio Mode icon ON, the GM24k is in “Beep”
Mode, meaning it will produce 2 distinct beeps,
one high and one low, for dierent types of tar-
gets. e higher tone has a better chance of being
a non-ferrous target (gold, aluminum, silver, brass,
etc.), and the lower tone has a better chance of
being ferrous (iron, hot rocks, etc.).
With the Audio Mode icon OFF (music note icon is
not displayed), the GM24k will produce a standard
VCO (voltage controlled oscillator) “zip” sound on
targets, where both audio pitch and volume rise as
signal strength increases. is “Zip” mode is gen-
erally preferred by experienced prospectors due to
the nuances of the sound and perceived sensitivity
to small targets.
All settings (SAT, Volume, reshold, Iron Cancel,
etc.) have the same eects in both audio modes.
is allows maximum exibility for dierent users.
Target ID #
Higher number,
Better chance of gold
Visual Target ID
“Beep” Mode
Audio Mode
Selection
Target ID
e GM24k features two types of Target ID. e
most obvious is the large numbers displayed in the
center of the screen when the coil passes over a
target. ese two digits represent a scale from 0 to
99, with higher numbers equalling a higher chance
that the target is non-ferrous.
In challenging ground, or when gold is located in
host rock, it’s important to dig every questionable
signal. Sometimes very small gold can produce
a low Target ID number, or in the case of sub-
grain-sized nuggets, no number at all. is is why
many electronic prospectors hunt mostly based on
sound.
In addition to this, the topmost bar of the screen
displays a general scale of targets. You can see that
gold has a large range, due to the many dierent
sizes, shapes, and consistencies of gold nuggets.
When in doubt, dig it out.

GM24k Controls
Goldmaster 24k User Manual 13
Disc Setting
(2 bars)
Iron Cancel (tap)
Disc. Adjust (hold)
Iron Cancel (Discrimination)
When detecting for gold nuggets, it is oen
best to “dig it all.” Gold can have various sizes,
shapes, and be embedded in iron rock, so it is
nearly impossible to account for every nugget
in the ground and only dig gold. However, in
challenging conditions the electronic prospec-
tor may need to adjust the GM24k to cancel out
unwanted targets or heavy ground mineraliza-
tion.
is is done at the expense of full sensitivity,
but in extreme conditions the amount of sig-
nals can overwhelm your senses, causing “ear
fatigue.” In these cases the real battle is in nd-
ing good targets, not raw depth. Situations
where you might need to use Iron Discrimi-
nation are: rapidly changing ground minerals,
high concentrations of hot or cold rocks, old
mining camps with iron trash, and highly vari-
able ferrous ground conditions.
Iron Cancel Adjustment
To enable Iron Cancel in either Beep or Zip mode,
tap the Nail Icon. is will engage the Iron Cancel
feature at the default setting. You can adjust this
setting up or down by holding the Nail Icon, then
using the Up and Down buttons to set the discrim-
ination range. Best practice is to only use what is
required for smooth operation of the GM24k, as
too high of an Iron Cancel setting will decrease the
detector’s sensitivity to small gold nuggets. Again,
this is a trade o—it is up to the operator to pick
the balance between a smooth threshold and max-
imum sensitivity. If you are getting a lot of high
signals from hot rocks, tap the LOCK button while
in the Iron Cancel adjustment mode. is will
block out a range of signals from 94-99.
Please note that unlike coin detectors, the thresh-
old will not go silent over discriminated targets
in the “Zip” (VCO) audio mode. is is to ensure
smooth operation and combat ear fatigue. You may
nd that it is best to detect with Iron Cancel o,
and then toggle it on to check a target. Very small
gold will oen report a very weak Target ID num-
ber, or none at all, so this setting is best used as a
last resort in only the most challenging conditions.

GM24k Controls
14 Garrett Metal Detectors
Gold is usually found in mineralized
ground, and the GM24k has XGB en-
abled by default when the machine is
powered on. is makes it easy to get
started prospecting, as the machine
automatically cancels out unwanted
mineralization so you can focus on
listening for targets.
However, there are times when you
may want the option to LOCK the
ground balance control, or even
display the ground information on
screen. e comprehensive ground
options on the GM24k allow you to
do both of these things quickly and
easily, without menu-diving.
XGB
e original Goldmaster® featured a revolutionary ground lter system that was quick to respond to min-
eralization changes. XGB is the automatic ground tracking method used by the GM24k, and features an
all-new method and algorithm. For users this means that they can use this detector in a wider variety of
ground conditions with more stable operation and less ground noise. When coupled with the Iron Cancel
and SAT settings, you have a truly versatile set of tools to combat nasty ground.
XGB is the default setting on the GM24k, and is recommended for most users in most conditions. It has
the ability to track a wide range of ground, from ferrous to alkali, and features an increased tracking speed
over previous models without hurting sensitivity to small nuggets. e arrows above and below the LOCK
icon indicate whether XGB is tracking up or down in values.
e algorithms used in XGB also give the GM24k an edge due to the ability to track multiple ground points
simultaneously. In highly variable grounds this is a huge benet, as you may encounter wide enough swings
in ground phase to render other machines almost unusable.
Even though XGB is the suggested ground setting, advanced prospectors know that there are times when
more control over the ground settings can equal more gold in your pouch. Details on these settings follow.
Ground strength
in GroundScan
TracLock ON
TracLock ON (tap)
Ground Scan (hold)
Ground Grab
Ground Phase
in Ground Scan
Ground Balance
Controls

GM24k Controls
Goldmaster 24k User Manual 15
TracLock ON (tap)
Ground Scan (hold)
TracLock
TracLock on the GM24k is the locked, “manual” ground setting. It functions similar to the original GMT.
To LOCK the ground tracking to the current setting, TAP the LOCK button. A padlock will display on
the screen. is will put a hold on XGB and lock the current ground phase and strength setting. is can
be useful in those cases where you may nd extremely tiny gold, or when you have located a faint target.
In some cases automatic ground balance has the potential to track out tiny nuggets as you zero-in on your
target. You may nd it useful to enable XGB while searching, and then LOCK the tracking right aer you
get a target.
Ground Grab
While the tracking is locked, you can press the CROSS HAIR button to perform a Ground Grab. is
updates the ground setting to what is currently under the coil. With a combination of LOCKED tracking
and Ground Grab, you can easily update the ground balance point as you swing.
When you perform a Ground Grab, the current ground phase reading will briey display on the screen.
is is a good way to keep track of the type of mineralization you are walking over. More ferrous soils tend
to produce a larger ground number, whereas more alkali soils will produce a smaller number.
Ground Grab will also display the ground phase when the GM24k is in XGB (automatic) mode, but does
not interrupt the automatic tracking processes.
Ground Scan
Ground Scan is enabled by holding the LOCK button. e display will change to display the ground
strength on the top bar, increasing from right to le. Full bars equates to very strong mineralization, and
one ashing bar alerts you that no ground information is present.
e two-digit numbers displayed are the ground phase. Solid ferrite will read around 81, and alkali will
read between 50 and 30, but you may encounter any range of phase numbers depending on the area you
are in.
In Ground Scan you can also set a ground oset by using the UP and DOWN arrows. is selection will
aect the ground oset in normal search mode whether using XGB or locked settings.
Ground Scan is very useful in prospecting dry washes or creek beds for black sand deposits. One trick
you can use is to carry some landscaping ags with you, placing one down where the mineralization is the
strongest about every 10 feet. at is where you would want to process material through a sluice or dry
washer.
To return back to the regular search mode, tap the LOCK or CROSS HAIRS.

16 Garrett Metal Detectors
Searching
Pinpoint Technique
Due to the wide scan nature of elliptical search-
coils it can be dicult to locate small targets un-
der the physical center of the loop. Use an “X”
marks the spot technique as shown in the diagram
to identify the portion of ground the nugget is in.
Because most nuggets are too small to isolate to an
exact location as in coin or relic hunting, remove
the soil under the center of the “X” until the target
is no longer in the hole, but in your pile of dirt.
Techniques for examining the pile of dirt are dis-
cussed later in the manual. (page 21)
Again, the procedure is to sweep over the target
from side to side noting the side to side center (see
step 1 in diagram). en turn 90 degrees and sweep
the coil side to side noting the center from this new
direction (see step 2 in diagram). “X” marks the
spot that you need to dig (see step 3 in the diagram). You can practice with a small pieces of lead or gold
on top of the ground to become acquainted with the technique. It’s a good idea to have a magnet handy,
preferably in the handle of your digging pick, to pull iron out of the dirt pile. It will speed up your recovery
time. It will work on small almost invisible hot rocks, too.
Non-Motion Pinpoint Mode
In addition to this traditional pinpointing method, the Goldmaster®24k also features a non-motion
pinpoint mode. is is engaged by holding the crosshairs button (large button in the middle of the key-
pad). With this button held down, the detector will sound o on targets whether the searchcoil is in
motion or not. Non-motion pinpoint mode disengages the XGB ground tracking, Iron Cancel, and SAT,
so in very challenging conditions you may nd that this pinpoint mode struggles to counteract minerali-
zation. But it can be very useful in sizing targets under the coil and giving you an idea of their shape. For
example, nails can oen pinpoint as an oblong shape with a stronger sound on the at head.
While in non-motion pinpoint mode, the screen will display the signal strength using the two bottom
“swoop” segments as well as the two-digit numeric display. e numeric display reads from 0-30, with 0
representing a target close to the surface and 30 a target at the edge of detection. Due to the various size,
purity, and mineral content of gold nuggets, this scale is not capable of giving absolute depth readings and
should only be used as a reference point for signal strength. It also may give strong readings for extremely
large iron items that can surprise you with how deep they really are. e opposite is also true—very small
nuggets may read as weak targets. So it is best to look at the readings and sound of the non-motion pin-
point mode as a signal strength, and not a depth reading.
1 2
3
GM24k Searching

GM24k Searching
Goldmaster 24k User Manual 17
Headphones
e headphone jack on the GM24k is located on the
rear of the battery box. ere is a dust cover for the
headphone jack (in your parts kit) that should be used
when not running headphones. Most prospectors
prefer high quality stereo headphones so the GM24k is
wired for stereo sound. In addition to the volume con-
trol headphones included with your detector, an 1/8” to
1/4” headphone adaptor is included. Plug this adaptor
into the headphone jack to allow the use of other 1/4”
size headphones.
1/8” to 1/4” headphone adaptor
Headphone jack du cover
In choosing headphones, make sure they have a VOLUME CONTROL. is is an important comfort and
safety issue. Remember that you want the faintest THRESHOLD “hum” possible but a strong comfortable
target signal. With headphones you will be able to work with a lower THRESHOLD “hum”, hear fainter
target signals, avoid bothering others with a “beeping” box, and save on battery life. Many high quality
headphones from full ear enclosure to lightweight summer models that oer a bit more safety in snake
and bear country are available on the market. Higher impedance headphones (60 Ohms or greater) give
the most sensitivity and are better for hearing the tiny targets most likely to be heard while prospecting.
Properly balanced impedance is important as well as low distortion.
Headphone Volume
Since the GM24k has a volume control (accessed by tapping the speaker button and adjusting the audio
volume up or down), certain sets of headphones with in-line volume control oer you added adjustment.
is is due to the fact that the GM24k’s volume control only aects signal sounds, not the threshold level.
For a maximum range of audio sensitivity, a user would set their GM24k volume at the maximum level,
and then adjust the in-line headphone volume to suit their preference. is will allow for both very subtle,
quiet signals as well as very loud signals, giving you a wide range of target volumes.
For a more moderate range of audio sensitivity, a user would set their GM24k volume at a medium level
and adjust the in-line headphone volume up. is will make quieter signals seem a bit louder and give less
dynamic range, which may aid in target acquisition for some users.

18 Garrett Metal Detectors
GM24k Searching
Field Use and Tuning Tips
Putting it all together:
Once you have achieved the initial ground balance,
you are ready to start searching. Move the coil just
over the ground and listen for the distinct zip-zip
sound produced by a target. It is wise to plant a
nugget just under the soil to practice on in order
to learn to recognize what it will sound like. If you
don’t have a nugget, use a nickel or piece of lead
(sinker or bullet). A very shallow bird shot sounds
just like a tiny piece of gold.
You can practice with dierent sized nuggets and at
dierent depths. Remember, planting a target dis-
turbs the ground mineral, which usually reduces
the depth it would have been found in undisturbed
ground. It will take practice to determine the prop-
er search speed and technique. Do not go too fast.
Try to overlap your sweep path so that you won’t
miss the tiny and deeper nuggets. When you hear a
zip-zip, perform the “X” pinpoint technique or use
the non-motion pinpoint feature (page 16) over the
loudest portion and eyeball the center.
Rather than concentrating on all of the controls of
the detector, think of the detector’s systems as an
extension of your senses that are working together
to tell you what is below ground. You will be tun-
ing yourself to the search area. e SENSITIVITY,
the GROUND BALANCE, the VSAT speed, the
THRESHOLD, the IRON CANCEL, all working
together at the same time. Soon the detector will
not even be noticed and your senses will take over,
painting a mental picture of what lies below.
Dig ALL Metal Targets at rst then Reject Iron:
At rst, dig all targets until you get used to the
sound of various items. As with other VLF
detectors, a nail or oblong piece of iron laying
horizontally will produce a double beep. A “good
target” is considered anything that is not IRON. You
want to detect lead, brass, copper, aluminum and
silver. Any of these metals can simulate the sound
of a gold nugget and must be dug. Keep a particu-
lar lookout for the tiny lead bird-shot so common
in mining areas. If you are detecting these tiny
targets, you are doing everything right and will
eventually nd gold.
Locked GROUND BALANCE tuning for very
small nuggets:
While the XGB automatic ground balance
makes nugget hunting easy for prospectors of all
experience levels, a LOCKED ground balance can
greatly improve your odds of nding gold in some
situations.
e reason for this is simple—the smallest nuggets
can produce only a slight threshold raise, and oen
vary only a few phase degrees o of the ground due
to their tiny size. If small gold is your gold, locking
the ground tracking allows those faint variances to
push through the ground balance point and create
a target signal for the GM24k.
However, in challenging ground conditions this
is not always an option. is is where using the
Ground Grab feature is useful, as you can manu-
ally update the ground balance at any point as you
detect.
Another option is to run the GM24k in XGB mode,
and aer hearing a faint target signal, immediately
locking the ground balance. Now you can double
check the target from dierent angles without the
XGB “tracking out” that target. is provides the
best of both worlds—automatic tracking but the
option to freeze it aer acquiring a signal.
If hot rocks are driving you crazy, you can also
ground balance directly over the hot rock, then
lock the tracking. If the rest of the ground matrix
does not give you a false signal aer doing this, you
have successfully cancelled not only the ground
but also hot rocks!

GM24k Searching
Goldmaster 24k User Manual 19
Backlight and Battery Life
With a short tap of the power button, the GM24k’s
backlight will turn on, giving increased visibility
in low light conditions. In bright sunlight it will
not be obvious this backlight is enabled, so there
is a light bulb icon to indicate the status as well
(icon on = light on). is light consumes extra
power, so it is best used only when necessary.
is backlight is on for a few seconds when pow-
ering on the GM24k, but only to allow for those
situations when the unit is turned on in total
darkness. It will turn itself o aer a few seconds
and the icon will disappear until the backlight is
enabled or the detector is powered back on again.
Operating GM24k in Extreme Mineralization:
anks to its XGB ground balance, SAT, and
Iron Cancel, the GM24k can operate in a wider
variety of conditions than many other VLF detec-
tors. However, it takes some knowledge of how to
use each setting to combat bad ground, and the
dierences between types of ground.
In very strong mineralization, such as heavy iron
stone or serpentine, it will be necessary to low-
er the sensitivity. ere is enough voltage at the
search coil to cause the GM24k to overload in bad
ground, so take some time to nd a good setting
for sensitivity before making other adjustments.
To check the ground strength you can enable
Ground Scan by holding the LOCK button.
Another issue you may run into is highly variable
ground mineralization. In these conditions you
will not get an overload response, but will have
to contend with lots of false signals with your coil
sweep. is is a result of the ground phase shiing
rapidly under the coil. e rst step you should
take is to increase your SAT setting by holding the
Music Note button, and then tapping the Up but-
ton to set the SAT to a higher setting. is will
allow the detector to adjust more quickly to the
rapid ground changes.
As a last resort, enable the Iron Cancel feature (the
crossed-out nail button). is will not allow those
low-range signals to break through the threshold
in either audio mode. Only in the most extreme
conditions should you adjust the Iron Cancel (by
holding the crossed-out nail button) to higher set-
tings.
Problems from Low Ground Mineralization:
e GM24k is designed to work in an environ-
ment of heavy iron mineralization. In some
cases, there may be so little mineralization that the
search-coil will never go quiet as it approaches the
ground. In other words, there never seems to be
any change or only a faint increase in hum as the
coil is pumped. In this instance, lock the ground
balance (lock button) and perform a ground grab
before detecting.
Hot Rocks
e ever-present “hot rock” has caused frustra-
tion with almost every electronic prospector.
Most large ones are on the surface and can be
kicked aside when identied. You will soon learn
what they sound like. e “overshoot” or “boing”
sound will soon become familiar. XGB is really a
good option when they are plentiful. We nd it
best to tune to the majority of the ground matrix
and learn what a “hot rock” sounds like. e XGB
of the GM24k will recover quickly upon leaving
the vicinity of a “hot rock” and will remain sensi-
tive to gold nuggets. Since there are dierent kinds
of “hot rocks”, it is almost impossible to eliminate
all of them with one setting. Some will be identi-
ed by the Target I.D. system as if they were iron.
In every instance, practice makes perfect.

GM24k Searching
20 Garrett Metal Detectors
Field Use & Tuning Tips (cont.)
Negative Hot Rocks:
Negative hot rocks are ones that sit below the
ground balance point of the GM24k. ey
actually produce a null or no sound when directly
under the coil, making a sound once the coil pass-
es them. is sometimes sounds like a “boing”
when the ground mineral and the rock mineral
are far apart in mineral TYPE, making them easy
to recognize. At any rate, these are usually black or
grey in color and usually magnetic. When hunt-
ing in LOCKED ground balance, they can oen
be tuned out by performing a Ground Grab right
over them and then proceeding to search with the
GM24k “over tuned” to the ground. When using
this procedure, be sure to search slowly and keep
the coil close to the ground and level. is will
eliminate the bother of such “hot rocks.”
In some parts of the world these specic types of
rocks are called “cold rocks,” since they ring up
beneath your current ground balance setting.
ey are usually easy to identify thanks to the
“boing” sound and diculty in pinpointing them.
If the ground is littered with these negative hot
rocks, not just an occasional one, the XGB will
track near the hot rock balance point, lowering
the GM24k’s response. You may be forced to dial
in more SAT speed and/or reduce SENSITIVITY
to keep a workable THRESHOLD “hum”.
Positive Hot Rocks and Alkali:
Positive hot rocks are usually red or various
shades of red to almost black. ey sit above your
current ground balance point. ey are some-
times as small as BB’s and sound just like nuggets.
ese positive “hot rocks” are dicult to tune out
and ring up very low on your Target I.D. scale.
ey actually give a positive signal like metal and
that is why they are so hard to dierentiate. e
XGB will track some of these out automatically.
Using a higher SAT setting can also decrease your
GM24k’s response to these positive hot rocks.
Using a Double D coil on the GM24k will allow
the detector to operate amongst hot rocks better
than a concentric. And as a last resort, the Iron
Cancel feature should all but silence any remain-
ing hot rocks.
Wet alkali washes can be extremely dicult to
work due to the sensitivity of high frequency gold
detectors to conductive dissolved salts and their
similarities with the responses of small gold. But
you can use the same techniques for alkali as you
use for positive hot rocks.
Adjusting SENSITIVITY with XGB:
If while searching with XGB you experience
erratic behavior such as false signals or con-
stant beeping and popping, you may be using a
SENSITIVITY level which is too high for the
ground mineralization. is is oen the easiest
thing you can do to increase your ability to hear
gold in bad ground. Simply tap the down but-
ton to lower the sensitivity on your machine. Try
searching again. Continue this until you can hunt
without having erratic signals. Your detector is
cancelling ground mineral as you sweep, so you
may notice a slight uctuation in the threshold
hum as the various ground minerals are tracked
out.
Even though it may seem counter-intuitive, ad-
justing the sensitivity down in tough ground
conditions can actually increase your chances of
nding a nugget. is is due to the fact that your
ears are an extension of the metal detector. Hear-
ing one faint signal against a smooth threshold is
much easier than hearing a medium signal against
hundreds of smaller ones.
Even though the GM24k comes with advanced
features like SAT, Iron Cancel, and XGB, don’t
overlook the rst step you should take on any
outing—nding the right sensitivity level for the
ground your are walking over.