NAUTILUS DETECTORS TIPS & TECHNIQUES
EMAIL US: Clyde@RelicHunterSupply.com
Myself being an avid user and fan of Nautilus detectors, I feel a need for this page. Nautilus detectors
are a hand built detector specifically designed with the relic hunter in mind. They are made of the
best components available. I've seen too many people that have purchased them get rid of them
before they had a chance to understand and appreciate how great of a detector that they had
because they didn't understand them. J.L. Sims Jr. Wrote the helpful tips below.
COIN & JEWELRY HUNTING WITH THE NAUTILUS DMC IIB and DMC IIBa
The Nautilus is not your average hobby detector. It allows more precise adjustment of the machines
features and requires some working knowledge by the operator to achieve maximum results. The
learning curve is a little longer, but the results can be very rewarding.
The ON-OFF switch is self explanatory. A word of warning.....the last thing you should do before
storing your Nautilus is check to make sure you have not bumped this toggle type switch to the ON
position or you will start your next days hunt with dead batteries.
The MODE SELECTOR has two positions.....NON MOTION DISCRIMINATE......and.....GROUND REJECT
DISCRIMINATION. The vast majority of your detecting will be with this toggle switch in the GROUND
REJECT DISCRIMINATION mode. This brings into play both the ground balanced all metal mode and
the motion discrimination mode. Operating with your earphone switch in the STEREO position, you
will get a low tone all metal sound in one ear and a high tone motion discriminate sound in your other
ear and can adjust the volume to each ear. Sort of like detecting in stereo with full sound effects. If
you place your earphone switch to the MONO position, you will hear both modes in both ear sets.
Hunting in MONO is about the same tone-on-tone system known as MIXED MODE on some other
machines. I prefer using STEREO with the all metal signal coming in the right ear and the
discrimination mode coming in the left ear The low tone sound from the all metal mode in your right
ear will allow you to judge a targets SIZE, SHAPE, DEPTH and CONDUCTANCE. The higher pitched
beep from the motion discriminate mode in your left ear will alert you to the fact that your coil is
passing over a target which you have not discriminated out. Being able to hear and compare signals
from both modes at the same time provides you with the information you will use to identify the more
The red RE-TUNE BUTTON is used to re-set your threshold sound as necessary and also to DE-TUNE
the all metal mode when pinpointing. The threshold sound will be a slight low pitched hum in your
right ear coming only from the all metal mode. The discrimination mode is set up as a silent search
motion mode and will signal only when an accepted target is encountered. To make your original
THRESHOLD adjustment, hold in the RE-TUNE button and turn the threshold adjustment clockwise
until you hear a slight hum. This slight hum will be your constant reference point from which you will
be able to determine the all metal audio characteristics of each target encountered.
The Nautilus's all metal mode is a threshold based mode. You hear a slight threshold hum in your
right ear at all times and that sound increases to indicate targets as you pass your coil over them.
The threshold sound decreases or goes quite to indicate an increase in non-conductive minerals.
The all metal mode doesn't cull anything, you will hear a change in threshold sound for everything in
the ground......and that includes a change in ground minerals. .
The Nautilus allows you to adjust the amount of voltage applied to the transmitter coil of your search
coil with the knob marked TRANSMIT POWER. This is a feature you wont find on most other
detectors and is one of the reasons the Nautilus is known as a very deep detector. The 6 volt
position of this control approximately equals the transmit power of an average detector. As you turn
the control on up toward the 44 volt position, you increase depth and sensitivity of the Nautilus. This
is not a linear control as far as depth is concerned, In other words, position 12 on the control is not
twice as deep as position 6. You can experience instability, indicated by a wavering threshold sound,
if you try to run this control too high at some sites. As a general rule, don't try to over-power a site,
just adjust as high as you can go while maintaining a stable detector.
Both modes of the Nautilus have their own SENSITIVITY control. The sensitivity control on the left
side of the control box is for the motion discrimination and the one on the right side is for the all
metal mode. The recommended sensitivity settings is 9 for discrimination and 3 for all metal. At
these settings, comparing the audio of the two modes will allow you to determine the quality of a
target. At these settings, the discrimination mode is deeper than the all metal mode. Having
separate sensitivity adjustments makes for a very versatile detector as you learn to make these
adjustments to achieve the results you wont.
The Nautilus DMCIIBa does not provide external sensitivity adjustments and it is my understanding
that its internal sensitivity settings are permanently set at 9 and 3 respectively.
Set the GROUND BALANCE adjustment at 65 prior to adjusting the search loop balance. I don't know
that this is necessary, it is just something I do as 65 represents a setting for average ground
Set the AUTO TUNE switch to the OFF position prior to adjusting search loop balance. You can also
perform the search loop balance procedure with the auto-tune switch turned ON but I think it is more
accurate to do this procedure with auto-tune turned OFF.
The Nautilus is the only machine I know of that has the SEARCH LOOP BALANCE feature. The
transmit and receive windings of a coil are precisely placed and epoxied into permanent positions. If
either coil is moved out of position, a signal will be created that can interfere with proper operation of
the coil. The contracting and expansion of the coils physical structure due to changes in
temperature can cause these minuscule changes in the coils operation. This can be happening to all
detector coils but seems to be a somewhat minor effect that it is ignored in other detector designs.
The electronic components in a coils circuits can also change value due to aging over a period of
time. The R and C controls of the SEARCH LOOP BALANCE system allows us to finely tune the search
loops coil to insure more precise operation.
Hold the search coil up to about waist level while performing search loop balance. This insures that
you are balancing the coil only and is not being influenced by targets or ground minerals.
Check that all metal mode sensitivity is set at 3
The Transmit Power Control can be set anywhere between 6 and 44 as long as you can maintain a
steady threshold sound. If threshold becomes unstable at higher settings, lower the transmit voltage
until you can maintain a stable sounding threshold.
Check AUTO TUNE switch turned OFF
If necessary, reset threshold by holding in the RETUNE push button and adjust threshold .
Adjust R and C controls to approximately 12:00 position
Turn SLB (SEARCH LOOP BALANCE) switch ON
Turn either R or C control to the left or right from their center position until the threshold tone
disappears (if you have trouble getting the threshold sound to disappear, lower transmit power.
After the threshold tone nulls out, temporarily depress the RETUNE button to bring back the
threshold sound. Do not re-adjust the threshold, just punching the retune button should bring back
your original adjustment.
Repeat the above procedure until the tone no longer disappears but just starts to rise.
Stop adjusting at this point. Now if you turn the R (or C) control just a small amount left or right you
will hear a small dip or null in the threshold volume. The objective is to have the smallest and lowest
sounding null you can get. Leave the R or C control to this nulled position. You can now adjust your
transmit power to a higher setting if desired as long as you can still maintain a stable threshold
sound after doing so. Turn SLB switch OFF. Search loop balance should be checked every 15
minutes for the first hour until the search loop has reached ambient temperature. (for example:
taking detector out of car which has temperature of 70 degrees into an environment of 30 degrees).
The R and C controls can be adjusted the next day from the point they were last set, assuming they
have not been accidentally moved. SLB should be checked after every 10 degree change in
Adjusting the SLB with the AUTO-tune turned ON is a little simpler. You don't have to keep manually
retuning after each adjustment of the R or C control because the auto-tuning will be automatically
returning threshold to where you originally set it. Simply turn the R and C controls either left or right
until you reach a point where the threshold temporarily nulls out. Once you have located that nulled
spot, adjust back and forth until it sounds like you are in the center of the nulled area. This null point
should be anywhere between the 9:00 position and the 3:00 position. If the coil adjusts out of this
range, the coil is going bad and needs repair.
Special care should be exercised in setting and maintaining a proper GROUND BALANCE. Ground
balance allows the detector to ignore ground minerals in order to reach greater depths and have
maximum sensitivity to all targets. Ground balance simply tunes out the sound of the ground
minerals and allows better sounds from targets. Keep in mind that the ground minerals are still
there, they have not "disappeared". They are still there and limiting your detecting depth and,
depending on the degree of mineralization and the type of minerals, can cause erratic detector
operation. At some sites, it may be necessary to lower coil voltage and sensitivity to stabilize
detector operation. The ground balance control of the Nautilus is very precise with an eight turn
vernier control and a wide adjustment range calibrated from 0 to 100. Since the Nautilus all metal
mode is threshold based and you will be listening to that threshold sound in one ear at all times, you
will immediately be made aware of changing ground minerals and can adjust accordingly. Simply
pump the coil up and down from about 12 inches over a section of ground which otherwise has no
targets, and you can frequently check ground balance as you hunt. You can ground balance with the
AUTO TUNE turned ON or OFF.
Ground balancing with the AUTO-TUNE turned OFF is probably more accurate but requires you to
retune threshold sound as necessary after each adjustment.
Set THRESHOLD to slight hum.
Locate a section of ground that is clear of all targets. Pump the coil from about 12 inches high to
within l inch of the ground and listen to the effect on threshold sound. If threshold sound increases,
you will have to adjust the ground balance control down (counterclockwise). If threshold sound
decreases, you will have to adjust the ground balance control up (clockwise).
Raise the coil, make a very slight adjustment up or down as necessary, hit the retune button to
return threshold to its original setting and lower the coil to the ground to re-check for effect.
Continue making small incremental adjustments until the sound of your threshold is the same with
the coil at 12 inches high as it is with the coil 1 inch from the ground. Retuning will be necessary after
each ground balance adjustment.
You may prefer to ground balance with the auto tune switch turned ON so that retuning the threshold
is not necessary. The purpose of the auto tune circuitry is to maintain the all metal threshold volume
to your original volume setting. Any increase or decrease in threshold sound will automatically be
tuned out and threshold returned to original volume. This requires you to have the coil in continuous
motion in order to hear targets. It effects only the all metal mode and creates, in effect, a MOTION
ALL METAL MODE. To ground balance with auto tune turned ON:
Set THRESHOLD to slight hum.
Locate a section of ground that is clear of all targets. Pump the coil from 12 inches high to within 1
inch of the ground and listen to the effect on threshold sound. The threshold volume should be the
same at 12 inches as it is at 1 inch. While continuously pumping the coil at the ground, increase or
decrease the ground balance control setting until proper ground balance is achieved. Manual
retuning is not required since auto tuning is taking place but you do have to keep the coil moving up
and down fast enough while pumping the coil to overcome the auto tune effect.
With the excellent GROUND BALANCE control of the Nautilus, there is no excuse for not maintaining
a proper ground balance at all times. As the ground minerals change, a new ground balance will be
required. Most sites will have very little mineral change but why take chances? Check ground
balance often as you hunt by finding a section of ground without targets and pump the coil at it and
reset ground balance as necessary. Some sites can have variable ground minerals to such a degree
that ground balancing may be required every few feet. The ground balance setting effects both the
all metal mode and the discrimination mode. You can get much more accurate and cleaner sounding
discrimination with proper ground balance. If a change in ground minerals results in a negative
ground balance on the Nautilus, it can cause falsing sounds in the discrimination mode. Think of a
ground balance as being the reference point from which all the other circuits work and you will
realize the importance of maintaining proper ground balance. Keep the ground minerals balanced
out and you will get the maximum depth and sensitivity to all targets. You can judge the degree of
mineralization by where the ground balances out. Above 65 is higher than average minerals, below
65 is milder ground. Settings higher than 65 is an indication of more non-conductive minerals. If the
setting goes too much below 65, it is indication that your ground has low mineralization.
The DISCRIMINATION control of the Nautilus is an 8 turn vernier control calibrated from 0 to 100.
Because of its wide range of adjustment, you can get very accurate with your degree of
discrimination. The discrimination setting that discriminates a certain item can vary depending on
site conditions. A setting that discriminates a specific target at a dry ground site will not be the same
as a setting for a high moisture site. The same applies to low and high minerals. Set your
discrimination to eliminate audio over the lowest conductor item you don't wont to dig and then
gradually adjust as you hunt to take into consideration the site conditions. It is best to keep adjusting
the discrimination down until you start digging more trash than you wont..... then turn it up just a tad.
If you wont to just use the Nautilus as a single tone motion discriminator, turn the all metal sensitivity
to Zero and you will no longer hear the all metal signal. This is your old familiar "beep/dig" or "no
beep/no dig" type of detecting and will not provide you with all the target information as the full
fledged Nautilus Dual Mode System.
With the Dual Mode system where you are listening to both the all metal mode and the discrimination
mode at the same time, it is best to use very low discrimination settings and then let your ears do
the discriminating. The discrimination mode allows you to hear the range of conductive targets you
have selected while the all metal mode audio helps determine the targets SIZE, SHAPE, DEPTH, and
CONDUCTIVITY. Any target you cannot define as "bad" should be dug. You will dig lots of trash to
begin with as you learn the Nautilus audio system but with time and experience, your good target to
bad target ratio will improve. My experience has been that many of the targets that I could not
identify as positively bad turned out to be something good. For example, I recently heard a signal that
had some indications of rusty iron but also some indications of higher conductance. My guess was a
small rusty iron item but since I couldn't positively identify the target as bad, I dug it. The target was
a large mans silver ring snuggled tightly to a rusty bottle cap. A couple of days ago, a beautiful
braided 14K gold ring popped out of the ground even though I was convinced I was probably digging
the ring off of a ring tab with the beaver tail broken off. I dig lots of those ring tab rings because it is
difficult to tell the difference between a jewelry ring and ring tab ring That pull tab ring reads pull tab on
a metered detector. After gaining experience with the Nautilus, you will realize that its all metal
audio, combined with discrimination, combined with your decision making ability, can be very
accurate and will often get you targets that have been missed by other detectors.
The auto-tune switch allows you to choose between a true all metal mode with manual retune and
an all metal mode with automatic tuning. In TRUE ALL METAL MODE (Auto tune switch turned OFF)
passing your coil over a target will cause an increase in threshold sound in your right earphone. If
you stop the coil over the target, the target will continue to sound off as long as the coil covers the
target. In this mode, the strength of the low tone signal gives some indication of DEPTH and
CONDUCTIVITY. The SIZE of the target is indicated by the length or width of the target sound as your
coil passes over it. By careful DE-TUNING over the target area, you can determine a targets SHAPE.
This mode has less sensitivity to the more conductive targets and will indicate them with weaker,
more narrow hits. Lower conductive targets give a louder wider sounding hit. In this mode, your
original threshold setting may sometimes "drift", becoming lower or higher volume than you
originally set it. You can return to original threshold at any time by punching the re-tune button with
the coil held about knee high above the ground or over a section of ground that does not contain any
targets. You can use the retune button for PINPOINTING while in true all metal mode by simply
punching the retune button while the coil is over the target area. Punching the retune button a few
times and DE-TUNING over the target area will "shrink" the target signal until the target sounds off
only in the very center of the coil, giving you a very accurate pinpoint. True all metal mode is best
used at sites where targets are not located close together and all "long", large, and very loud
sounding targets should be DE-TUNED and investigated.
AT trashy sites it is better to use the AUTO-TUNED ALL METAL MODE. In this mode, any increase or
decrease in threshold sound will be automatically tuned out as auto-tuning attempts to maintain a
steady threshold sound. This, in effect, makes the Auto tune mode a motion mode because the coil
must be kept in motion to hear the targets. If the coil is stopped over a target, the sound of the target
will be tuned out as threshold is returned back to it's normal low volume. The purpose of auto tuning
is to maintain a steady threshold sound, ignoring small volume changes caused by variable ground
minerals, sloppy coil movements by the operator, and uneven ground surfaces. This feature allows
actual target sounds to be more easily recognized against the background sound of a steady
threshold. Different manufacturers have different speeds of auto-tuning. The Nautilus has a fast
auto-tune and will quickly tune out the sound of most targets in approximately one to two seconds
depending on target depth and size.. It does, however, rapidly retune to normal threshold sound after
it passes over a target so that it can quickly sound off on another target located nearby. This fast
recovery from target to target allows us to hear individual targets located close together similar to
the fast target recovery being heard from the discrimination mode. You do not, however, get as
much audio information from your targets in this mode unless you maintain very good coil
discipline. If Coil movement over a target is too slow, the sound of the target is being tuned out
before you get enough information to determine its size, shape, depth, and conductance. This mode
requires a certain coil sweep speed to get good audio information from a target, not too fast, not to
slow. Practice your coil sweep speeds over both good targets and trash targets laid out on a target
free section ground. The proper coil sweep speed will make each type target sound the same each
time you pass over it. This is critical as these are the sounds that will help you classify each target.
Iron will be the widest sounding targets. Targets of coin size and similar conductance will sound
narrow with weaker volume. Targets of mid-conductance range like pull-tabs and brass will sound a
little stronger and wider than coins but not as wide as iron. Without going into detail about all the
audio information you can get from targets in the auto-tuned all metal mode here, it is important to
note again that coil sweep speed must be co-ordinated to auto-tuning speed in order to hear a
targets audio characteristics.
PINPOINTING in the Auto tune mode can be done best by raising the coil approximately 6 inches
and moving back and forth over the target to locate it as it beeps only under the very center of the
coil. You will be hearing both the all metal sound in your right ear and the discrimination sound in
your left ear as you pinpoint in this manner. You can get some DEPTH, SIZE and CONDUCTANCE
information about a target by pinpointing with a raised coil. Small, higher conductive targets signals
will fade rapidly in both signal strength and width as the coil is raised. Most less conductive targets
and larger targets signal strength will not fade as rapidly as you raise the coil and tend to keep
reading wider than coin type targets at this raised coil height.
The Nautilus is an excellent motion discriminator with great depth and sensitivity. Simply turn the all
metal sensitivity adjustment to the 0 position to shut off the sound of all metal mode and all you will
hear is the high tone of the discrimination mode. Switching your earphones from Stereo to Mono will
give you the discrimination beep in both ears. It is important to remember though that the
discrimination mode depends on the ground balance of the all metal mode as a reference point for
proper circuit operation and continue to make ground balance adjustments as necessary. False
signals from the discrimination mode is an indication that re-balancing to ground is necessary.
RANDOM THINKING ON METAL DETECTING IN GENERAL AND THE NAUTILUS
IIB AND IIBa IN PARTICULAR
COIL DISCIPLINE............Proper coil movement is important with any detector but is even more so with
the Nautilus. Most detectors make the decision for you to dig or not dig by simply a discrimination
beep, or a meter, number, or graph indicator. Since the average detectorist does not want to dig any
more trash than necessary, most detectors are electronically biased toward indicating the most
probably good targets. Not so with the Nautilus. It gives you very good audio signals from which you
make the dig/no dig decision. You, as the detector operator, are intimately involved in the decision
making process. How you move your coil over the targets determines the quality of the audio that
you will use to make those decisions.
Slow coil sweeps work well on the Nautilus. It is capable of giving you a clear discrimination signal
at very slow coil movement. This discriminate beep is well defined with slow coil movement and can
be accurately used for pinpointing if desired by crossing the target and digging at the center of the
Faster or slower sweep speeds will change the sound of a target. You wont to develop a sweep
speed that will make the same type of target sound the same to you each time you pass over it. After
you have approximately pinpointed a target, you can make faster and slower and higher coil passes
in an attempt to gain more audio info but a relatively slow steady sweep speed is necessary to first
recognize a good sounding target.
Some rusty iron stuff, especially if it is round like a bottle cap or a washer often sound good in
discriminate mode at normal sweep speeds but will have a wide all metal sound to help identify
them as iron. They can be further identified by making a short fast sweep directly over the
pinpointed target and that will cause the rusty iron stuff's discriminate signal to deteriorate or
completely go away. If a short fast sweep makes the discriminate signal sound better, it usually
means a target thats more conductive than rusty iron and should be dug.
After you pinpoint a target, compare the audio of a ground level sweep to a raised coil sweep about 6
inches above ground. The more conductive targets like coins will sound fairly weak and relatively
narrow at ground level and tend to fade a lot with a raised coil while less conductive targets do not
fade as fast.
VOLUME MASKING is a term I made up myself. Whether it is technically correct or not, I don't know
or care, as long as it helps me understand what happens in the all metal mode with the AUTO-TUNE
SWITCH TURNED OFF. If two relatively shallow targets are close enough together so that the coils
magnetic field is lighting up both targets at the same time, you get a high volume "long" sound as
you pass from one target and on over the other target. Once the threshold goes to full volume over
one target, it will just continue that high volume over the next target. This mode of operation cannot
recover quickly from one target to indicate another target. If you re-tune your threshold over the long
target area, you give yourself a lower volume threshold as a new reference point and can move your
coil around and keep retuning until you can locate both targets.
Every time you re-tune your threshold using the true all metal mode (auto-tune turned OFF) the re-set
threshold assumes a new reference point, depending on what is under the coil as you re-tune.
Retuning with the coil in the air is your basic threshold sound and the reference against which you
will compare all targets, including ground minerals. If you re-set over a target free area of ground,
your new reference point represents that particular section of ground including whatever type of
minerals it contains. If you re-set over a target area but not exactly centered over the target, your
new reference point contains ground mineral information plus partial target information. If you reset
exactly over a target, you tune out the sound of the target and the threshold sound then represents
only that section of ground between your coil and the target. If you re-set directly over a target, you
will no longer be able to hear sounds from other targets that are located deeper than the referenced
target. With proper re-tuning of threshold sound, you can shrink the sound of targets in an area so
that you can locate and separate individual targets. If you accidentally tune out the target while
attempting to pinpoint, move you coil about one or two inches to the side, re-tune, and you have a
new reference point that will locate your target. Proper use of this feature is like poking your finger
into the ground and feeling around.
A long sounding target can be just that, a long target, or it can be more than one target located within
a coils diameter of each other. Coin spills containing multiple coins can sound this way. Multiple
targets can be determined as described above. Long targets can be determined by de-tuning and
tracing out the shape of the target. With proper detuning, you should be able to recognize the size
and shape of a 8 penny nail. It will read long one way and short the other. With a smaller coil, you can
even determine the shape of elongated items smaller than an 8 penny nail. Some backyard practice
is needed to perfect this skill. The all metal mode can make any target sound long with a very slow
coil sweep. And a very fast sweep just gets you a short sounding beep. You have to practice your
sweep speeds until the same type of target sounds exactly the same way every time you pass over
it. Think of your coils electromagnetic field as an extension of your forefinger and visualize yourself
as poking your finger into the ground and feeling around. The dual mode system of the Nautilus can
connect you to whats in the ground like no other machine if you, the operator, do your part. Think
about the targets size, shape, depth and conductance as compared to the sounds you hear. With
time and experience, its kind of like osmosis, the knowledge and proper techniques will just "seep"
into you and become automatic but that requires some effort up front by you. Soon, you wont have to
think about what to do, it will just become automatic.
With experience you will be able to make a good guess at a targets depth as you also determine its
size, shape and conductivity by maintaining good coil discipline and techniques. Some people just
think of the coil as something you swing back and forth and it will do magical things for you. That
may be true to some extent but it is much more enjoyable to learn to use it as an extension of your
brain, arm and hand.
Summing up the ALL METAL with AUTO-TUNE turned OFF mode. This mode provides you with the
most easily recognized mineral and target information. Proper coil manipulation by the operator is
necessary to receive maximum benefit from this mode. Sloppy coil work gets sloppy results.
Intelligent re-tuning technique adds to your ability to maximize this mode. Once you learn the target
audio sounds of this mode using just one of your sense's, your hearing ability, you can feel totally
connected to the ground and whats hiding in it. No meters, tones, ding-dong bells, whistles, or
smear graphs to distract you. This mode, however, may not the best to use in sites with numerous
targets, trashy conditions, or variable ground minerals. For sites like that, you use auto-tuned all
AUTO-TUNE is a type of filter circuit to eliminate inadvertent sounds that would interfere with hearing
and recognizing a good target sound. Ground with fast changing minerals and mixtures of hot and
cold rocks would create a lot of background noise without auto-tuning. The same thing applies to a
very trashy old home site where the trashy sounds would override or make unrecognizable the sound
of wanted targets without auto-tune. Hunting over uneven ground would effect the threshold sound
by making the coil appear to be moving up and down in relation to the ground surface. Under bad
hunting conditions, auto tune provides a relatively smooth steady threshold hum as a reference point
and allows you to more easily recognize wanted target sounds.
Auto-tune overrides the "volume masking" described above. With auto-tune turned on, the threshold
is being re-tuned so fast that recovery from target to target allows you to hear separate signals from
two targets located fairly close to each other. Lay two targets about 6 to 8 inches apart on the
ground, pass over them in sequence, and notice the effect of fast and slow sweeps. Volume
masking can still take place depending on how fast you sweep in the auto-tuned all metal mode.
You can pinpoint with auto tuned all metal as long as you move the coil in a north/south, east/west
crossing pattern and dig at the beep of the crossing point. The higher toned beep of the
discrimination mode will be beeping in unison with the auto tuned mode to assist in pinpointing on
targets that are producing clear discrimination signals.
You can use auto tune to judge depth but you got to think fast to do it cause the auto tune works fast.
After you pinpoint, raise the coil about 6 inches and you will hear the auto tune quickly go silent before
tuning back to normal threshold. How long did it take to tune back to threshold? If it re-tuned
immediately, thats a relatively deep target. If it took a little longer, thats a shallow target. If you
missed that on the upward movement of the coil, simply put the coil back down on the center of the
pinpointed target. A shallow target will take longer to tune out, a deeper one will tune out
immediately. Some very shallow coins or very large targets will not tune out with the coil at ground
level which gives you another depth indication.
Since auto tune so precisely maintains the threshold setting where you set it, you can play some
tricks with it. You can adjust the threshold down into the silent area and the auto tune will hold it
there just exactly where you set it. Even though you are no longer continuously hearing the all metal
hum in one ear, it is waiting there to pounce out at you when your coil passes over a target. If you set
the threshold just barely into the silent range, you will still get a sound over just about every target
you pass over except a few very weak and deep targets and those extremely small foils and small
low conductance jewelry items. Those type signals will be just too weak to climb out of the silent
zone into the audible zone. You will be cutting off just a little bit of the targets front end and rear end
sound. You can adjust just a little farther into the silent zone to rule out the sounds of some more of
the shallow stuff if you are hunting for something that you are sure is large enough to create a signal
strong enough to climb out of the silent zone into the audible zone. That would be "surface blanking"
of some targets and amounts to another form of discrimination. Remember, we are talking only
about the threshold of the auto-tuned all metal mode. It is something to play around with. I
sometimes hunt for coins with the threshold just barely adjusted into the silent zone when I'm pretty
sure there is not much jewelry around. Lots of relatively valuable jewelry will only sound off very
weakly in the all metal mode and not at all in the discriminate mode that is set to discriminate small
iron. The best threshold setting is just barely a hum, so that you can recognize that tiny little zip
sound that some jewelry (and lots of foil) make. The Nautilus is surprisingly sensitive to tiny low
conductance jewelry items.
You can determine the shape of a medium to large sized target with the auto-tuned mode by poking
around at the target from all directions to sort of outline the target. Even an 8 penny nail can still be
recognized as long in one direction and short in the other with proper coil movement.
So far, I have been ignoring the DISCRIMINATION mode. That is because there is so much more audio
information to be gained from listening to the all metal mode. There is some audio info in the
Discrimination mode but not much. Nautilus recommends you set the discrimination mode at 9, just
short of 10, which is maxxed out. At this setting, what you get is a very strong discriminate beep
without much nuance to it. This beep doesn't start loosing strength on my Nautilus until targets are
around the 5 to 6 inch level so it doesn't give us much depth info. On the IIB's you can decrease this
sensitivity which will loose you some depth but begin to sound a little more nuanced. The IIBa has
fixed sensitivity settings for both modes, 9 for discrimination and 3 for all metal. The advantage of
the IIBa, other than having automated loop balance, may be these two fixed sensitivity settings. You
cant change them so they will always provide the same signal comparisons. There is something to
be said for consistency and working from fixed reference points. On the other hand, the IIB's
adjustable sensitivity settings give more versatility which allows different settings for adapting to
different site and hunting conditions.
Discrimination on the Nautilus Dual Mode system depends on the instantaneous comparison of the
discrimination mode and the all metal mode. For full effect, set discrimination to discriminate only
small iron and then compare the two modes. One mode sounds off in one ear and the other mode in
the other ear if your earphones are set to STEREO. If you set the earphones to MONO, you get the
tone-on-tone effect like mixed mode on a few other detectors The discriminate signal simply tells
you one thing: you are passing over a target that you have not discriminated out. Compare that to the
all metal signals which indicate size, shape, depth and conductivity and then you make the decision
to dig/not dig depending on how you read these signals.
Robert Sickler, who wrote "Detectorist", a great reference book about metal detecting, describes
the Nautilus method of audio discrimination; "If the all-metal signal is heard long before and louder
than the motion signal, the target will likely be large and ferrous in content. If the all metal audio
signals shortly before the motion signal with about the same strength, the target will likely be brass
or lead. When both signals sound nearly in unison, the target will be higher in conductivity and more
likely a coin. Should the all-metal signal be greatly weaker in comparison to the discriminate audio,
the coin could be very deep and made of silver." I might add that this is with discrimination at 9 and
all metal at 3. Changing your sensitivity settings will alter your audio sounds.
At the Nautilus recommended settings, the discrimination mode will go deeper than the all metal
mode. The all metal mode at this lower setting will give you more descriptive audio information about
targets. Increasing all metal sensitivity will alter target audio from that mode. Targets can not only
sound louder but also broader than they do at the recommended setting of 3. That appears to be the
reason that the IIBa has a fixed sensitivity of 3. At some sites, using the IIB, I experiment by lowering
my all metal sensitivity to as low as 2.
The ground balanced all metal mode has less sensitivity to the more conductive targets such as
coins and silver jewelry. Less sensitivity simply means it wont hit as hard on these type targets or
read them as deep. These type targets hit softer in the all metal mode and also signal mostly in the
very center of the coil with very little "width" of signal. The compact, symmetrical and consistent
shape of these type targets seem to also influence the narrow sounding hit. An oddball shaped high
conductance target may hit softly but sound wider. So if you get the discriminate beep accompanied
by a fairly soft sounding narrow all metal hit, you have a higher conductance target of approximately
the same size as a coin. A common way of saying this is that both modes tend to hit at the same
time. Something like a dime at a little depth will hit so narrow and softly on the all metal side that the
discriminate signal will strongly dominate. Quarters hit softly but being larger, have a wider hit than
the dime but can be recognized by the softer hit which fades rapidly as you raise your coil and
re-sweep. With a little practice you will quickly learn to recognize these type targets. You can
emphasize the softness of the weaker hits by lowering all metal sensitivity from 3 to about 2.5.
The sound of the more conductive targets, being weak to begin with, will weaken rapidly as you
raise your coil and re-sweep them. If you get a good sounding signal at ground level, get a second
opinion by raising the coil about 6 inches and re-sweep. You get bonus points for doing this as
raising the coil often improves discrimination and pinpointing.
Targets with mid-level conductivity hit a little harder and wider. As you pass over a pull tab, you will
hear the all metal tone coming on before the discrimination hits. A penny and a pull tab are very
close in conductance and sound similar but the penny will fade faster as you make a higher coil
pass. The ring of a pull tab with the beaver tail broken off is just a little bit more conductive than the
complete pull tab and is even harder to tell from the penny. The narrow "width" of the more compact
coin hits help distinguish them from wider sounding aluminum trash targets, especially with the
raised coil pass.
The operating frequency of the Nautilus is such that it hits hard on targets in approximately the
same conductance range as nickels. The same trash target, like the beaver tails broken off of a ring
tab, that fooled your metered ID machine, may fool you and the Nautilus also. Breaks of the game.
Good solid hits in both modes that are distinct enough to alert you to something in this range has to
be dug because of the rings and other desirable targets that fall in this conductance range. Nickels
tend to fade a little faster than some trash targets with the raised coil pass and give a more
compact sounding hit. Jewelry items, depending on size and conductance can vary some in width of
signal but tend to fade fast on the raised coil test. If you have iron discriminated out, some very small
jewelry items can be heard as a weak kind of "zip" sound, only in all metal. So does some small
pieces of foil but if you are hunting a site where you expect to find jewelry, check out the zip sounds.
Iron reads widest of all, usually wider than the coil. You can start getting an iron signal before the
leading edge of the coil reaches it and the signal can hang on for a short distance after the coil
passes over it. Hunting with the auto-tune turned off allows you to "feel" and "poke" around a target
to determine its characteristics. An 8 inch coil can give you a 10 inch wide signal over iron. An
honest iron signal is easy to recognize. Unfortunately, all iron is not honest and it can give off erratic
signals ranging from iron to coin. Steel bottle caps are really bad about this because of their similar
size and shape to coin type objects which allows them to simulate some coin characteristics such
as sometimes having a tighter more narrow sounding hit than iron on your first coil pass. Still, you
will usually hear something in the signal to raise your suspicions and cause you to make the two
standard tests for rusty iron stuff. First, double check the width of the target to verify a wide signal
and next, make a short fast coil sweep right exactly over the center of the target to see if the
discrimination signal deteriorates or goes away completely which indicates rusty iron. If your
discrimination signal sounds better as you make the fast coil sweep, it may indicate something a
little more conductive than rusty iron or steel bottle caps. Not always, but it pays to gamble and dig.
Bottle caps made by different manufacturers have different combinations of metals in them and
some can be hard to distinguish from a coin. In my area, Shiner Bock Beer bottle caps indicate
nickel on two different meter and tone ID machines. Sounds like a nickel on my Nautilus too. And
make a short fast pass over those suckers with a Quantum XT and they read high coin every time
and show just one or two pips on the smear graph.
It is hard to accurately talk about the sounds targets make on the Nautilus with the written word but
the Nautilus has an outstanding language of its own that you will learn to speak. With the right
operator technique you can coax it to tell you some secrets. What does a good target sound like? As
one old timer said, "You will know it when you hear it."
The shape and size of a target has a lot to do with their sound characteristics. Solid compact items
have a more definite solid sound and tend to give a more narrow signal. Rings provide an ideal
directed circuit path for current to flow and create a good signal. Irregular shaped items like ring
tabs tend to give a more scattered, or wider, signal. Square tabs however, being compact and about
coin size and made of only one metal, give a good sounding coin type signal but they don't fade out as
fast as you raise your coil like a more conductive coin does.
.On the Whites machines with signagraphs, a sort of graph was presented of a targets audio
characteristics. It is a great tool but with the Nautilus you have the same ability while concentrating
with only one of your five senses, your hearing.. Compact targets such as coins or rings only raised
one or two pips on the graph. On the Nautilus, you hear that as a narrow hit. Your indication is just as
accurate as the graph. Iron on the signagraph was represented as a wide "smear", raising many
pips across the conductivity range. On the Nautilus, you hear that wide sounding smear for iron. On
the signagraph, a target pip was shown on a referenced background of a conductivity scale. On the
Nautilus, the simultaneous discriminate and all metal sounds tell you basically the same thing. On
the Nautilus, you have both modes in stereo working at the same time to poke around at the target
and get some more target info. The electronics of some metered type machines are so strongly
biased against trash that they tend to ignore doubtful targets. With the Nautilus, you should dig more
of those doubtful targets, dig a little more trash but get some more goodies. The Nautilus system
invites you to gamble and take a chance. Preset meter ID systems are designed to keep their
operators happy by a strong bias against doubtful targets so they dig less trash. You will often be
able to find stuff a metered machine and less experienced operator passes over.
Many targets have more than one metal in them. Gold rings are not pure gold but mixed with silver,
copper, etc. The less conductive the mixture of metals, the "wider" the targets sound but the fade
rate over rings is faster than most trash items and you can learn to recognize them. Your detector
tends to "average" out the conductivity of what it sees under its coil. A quarter and a pull tab laying
within an inch of one another at the same depth often reads zinc penny, an average between the
metals. If we are not digging those annoying zinc pennies, we are now minus a quarter. A quarter
and a nickel are both good coins that we would like to have but if they are closely co-located, they
can read ring tab or square tab. If we are hunting with high discrimination with tabs discriminated out,
we would have lost 30 cents. Now we are 55 cents in the hole. The Nautilus tends to average closely
co-located items too but the result usually doesn't sound exactly like what either of the two targets
would sound like by themselves. In my experience, the more conductive item will dominate. All the
more reason to dig those targets that you cannot definitely define as bad by their audio sound. Thats
is how I got the big silver ring that was snuggled tightly to a rusty bottle cap. And this in an area that I
know I had been over numerous times with about 4 different detectors. Even the Nautilus
discrimination mode didn't make a good enough dig signal over that target but in all metal it didn't
read as wide as iron and it faded out almost as fast as a coin when I raised the coil. I can only
attribute that to the Nautilus "averaging" the two targets and giving me a hint that something wasn't
Ring tabs can consist of four different metals. There is the ring of one particular aluminum alloy. The
beaver tail tab seems to be of a much stronger metal, possibly more like tin or steel. Then there is
the rivet that holds the two parts together. And last but not least, the inside of the beaver tail is
coated with something which is probably metallic in nature. Add in the fact that different
manufacturers may be using different metals. This mixture of metals cause's a little bit of a
smearing sound, wider and louder than a coin hit and it will not fade out as fast as a coin or most
jewelry items with a raised coil pass. Coins fade out fast compared to a complete pull tab which
continues to sound off wider and stronger from a greater hight. The beaver tail separately reads just
like a nickel on the vast majority of detectors, including the Nautilus. The ring part of the tab
separately reads higher conductance than a complete ring tab and sounds very similar to a penny.
Lots of idiots got nothing better to do than sit around breaking the beaver tails off of the rings and
throwing them around. With practice, you will feel confident in recognizing most complete pull tabs
but once the two parts are separated, you may often get fooled into digging the ring as a penny and
the beaver tail as a nickel. Breaks of the game. I still dig every thing I'm not sure of and thats how I
got the 14 Karat braided gold ring. Grumbling and mumbling, absolutely convinced I was digging
another ring part of a pull tab. Best looking pull tab I have found lately.
Adjusting the all metal sensitivity upward changes the audio characteristics of the targets, making
them sound louder and also wider. The electromagnetic field around your coil not only gets deeper, it
also gets wider, picking up some irritating noise from fringe targets off to the side of your coil. For
coin or jewelry hunting under average conditions, I don't recommend any all metal settings above 3.
With the discrimination sensitivity at 9, it will be providing good depth while the all metal mode at 3 or
even less, will provide the quality of audio you need to help you identify targets. On the IIBa, those
settings are fixed so you have no choice. On the IIB at very trashy sites, I often turn discrimination
sensitivity down to about 6 and the all metal sensitivity as low as 2.5. The IIB allows you to adapt both
modes sensitivities to a sites hunting conditions. If you try to overpower a site with sensitivity too
high you do more harm than good. For coins and jewelry, you wont to adjust for cleaner sounding
and more accurate discrimination. You still get very good depth at these settings and can more
cleanly pick the good targets from the trash.
If the amount of trash is not just overpowering, discrimination should be set between 15 and 20, just
enough discrimination to eliminate audio over nails and small iron. You will have to listen to a lot of
discriminate and all metal signals but lower discrimination combined with audio discrimination is
very effective in picking the good stuff out of the trash targets and iron. At this low discrimination
setting, small iron and the ground are the only things masking targets and have a minimal effect.
Everything below your discrimination setting has a negative effect on everything above it. The less
you discriminate, the better your chance of getting good clean signals on all targets that you are not
discriminating. If you adjust the discrimination up past square tabs to where you get a signal only
from coins you have added foil, bottle caps, nickels, ring tabs and square tabs as discriminated
items, just to mention a few. With that high discrimination setting, you have declared that everything
in the ground is trash except coins and a few other high conductance items. The nickel doesn't like
being called trash and it can retaliate against you for treating it so rudely. You may think you are
getting all the good coins now but if you lay a nickel beside a quarter and check for signal, you wont
get a discrimination tone. The nickels influence on the quarter causes your detector to average the
two items out to somewhere in the pull tab range. No beep for you. Wont to feel really bad? Lay a
nice gold ring beside a quarter. No beep again? Too bad. Serves you right for calling nickels and gold
Your threshold setting can be used as a sort of discriminator in the AUTO-TUNED all metal mode. On
my Nautilus, a discrimination setting of 17 is just right for discriminating out most nails and small
iron. I hate to set it any higher than that for fear of loosing some tiny jewelry even though at some
coin sites the foil signals can really be bothersome. If I increase discrimination to get rid of the foil, I
am beginning to get into my jewelry range. One of my test targets is a very thin low quality gold
plated ring. It is about as low quality piece of jewelry as I care to find. With that ring buried at a hunt
site about 3 inches deep and the ground stomped down tight over it so that my detector is looking at
some ground minerals as well as the ring, I adjust my threshold below normal threshold
(AUTO-TUNE MODE) into the quite zone until a signal from the ring goes away as I am passing my coil
over it at the normal coil hight I hunt at. Then I adjust threshold back up until I just barely start getting
the ring signal again and stop there. Now any foil that is of lower conductance than that ring cant
come out of that quite little hole I have put it in. I am now hunting with a quite threshold but I am still
able to hear the ring and all other targets that are of a higher conductance than the ring. I may have
just a little less depth and sensitivity to the deepest and weakest targets with this setting but at coin
and jewelry sites, depth is not what I need.
Keep experimenting with settings on the Nautilus and see if you cant discover some different
settings that will do some different chores for you. Let your imagination run wild. You have the right
detector to experiment with because you are in full control. For coin and jewelry work, setting the all
metal sensitivity below 3 can give you some interesting results. At settings between 2 and 2.5, you
loose almost all sensitivity to the higher conductivity stuff like coins. Then if you get a good strong
discriminate signal and little or no all metal signal its coin stuff. At a certain setting, anything below
the conductance of coins will sound off fairly strong in all metal while coin type targets are very soft
and weak. This works good for skimming quarters and dimes from play ground and school areas.
A good way to familiarize yourself with the Nautilus as a coin hunter is to adjust the discrimination
mode up to where you will get the high tone only on coins. Turning the Discriminator all the way up to
100 on my machine drops out everything from zincs and screw caps and below, leaving only copper
pennies, dimes and quarters. Most silver jewelry can still hit also. Discrimination sensitivity at 9
(experiment with lower settings) and all metal at 3 or just slightly lower. Get familiar with the sounds
you get from all metal mode at the same time you get a coin hit in the discrimination mode. Later,
you will recognize these dual mode sounds for coins when you decide to lower discrimination. Once
you are familiar with those sounds, drop your discrimination down to accept the zincs and screw
caps and practice listening to the zinc penny sounds. The next step is to drop discrimination down
low enough to accept square tabs but still discriminate ring tabs. Square tabs and pennies hit very
similar but with practice you can learn the difference. Then drop your discriminator all the way down
to 30, well below the nickel reading (approximately 40) to practice listening to the ring tabs and
trying to distinguish the sounds of the nickels and other coins. Dig everything that sounds good or
"iffy", study your results and your trash to treasure ratio will improve. There are lots of good coin
and jewelry targets lurking in that aluminum trash area that most other hunters have just
discriminated or "notched" out and it will surprise you the degree of accuracy you can reach by just
listening to the audio of each target. Don't burn yourself out while learning. You can always kick the
discrimination back up like most people do and just skim for the better coins. But while hunting at
these higher settings, learn to concentrate on the sound of the all metal mode. You are going to get
the high tone discriminate sound anyway and you cant miss that high tone beep so learn to
concentrate on the sounds from your all metal mode. Throw a nickel on the ground and listen to its
sound from the right ear phone, the all metal mode. Dig all nickel sounding targets from the all metal
mode side as there is some good stuff in that range. You can do this even as the discrimination side
is beeping away only on Quarters, Dimes, and Pennies. Practice listening to the all metal sounds of
good and bad targets. While hunting for coins with the discrimination side, you can still hunt for the
better sounds from the all metal mode. I once dug 30 "nickel" sounding targets from the all metal
side while hunting coins from the discrimination side. I only got one nickel but when I ran those 30
nickel sounding items past the coil of an IDX Pro, about 15 of them would have been recognized as a
nickel by that machine or flirted with the nickel reading These were items like galvanized fence
staples, beaver tails, 22 bullet (unfired), metal guitar finger picks, etc. No jewelry items in that
particular experiment, but since then, I have recovered some jewelry items while hunting in this
manner. It is surprising what you can hear about targets from the all metal mode. Never judge a
target with a ground level pass only, raise the coil 6 to 8 inches and recheck the targets "fade" rate.
Different targets fade out at different rates in both audio strength and width of signal. As an
example, a full sized un-mutilated pull tab will keep its width and strength of sound at a much higher
coil hight than the more conductive coins.
Raising your coil from ground level to 1 inch above ground decreases the ground mineral effect on
your detector. The ground mineral effect decreases even more at 2 inches above ground. And of
course. The more you continue to raise your coil, the less the ground minerals are effecting your
detectors circuits. You can improve the quality of discrimination signals by raising your coil and
passing back over the target because you have eliminated some of the negative effect of ground
minerals. This effect is more noticeable in ground with higher levels of non-conductive minerals. At
some such sites, it often pays to hunt with the coil 2 to 3 inches above ground and also to ground
balance at that level. You may be giving up some depth but improving your chances of hearing
targets being masked by minerals. This is almost exactly the same thing as going to a smaller coil to
eliminate some of the ground effect that hinders your detectors ability to discriminate.
Some sites will prevent you from running high sensitivity and high coil transmit voltage. If you have to
back down either of these two adjustments, opt for decreasing sensitivity before you decrease
transmit voltage. The reason is that a higher sensitivity setting will not only give you more depth and
audio from the target but will equally increase ground noise, internal circuit noise, and any radio
frequency noise in that area. Increasing coil transmit voltage does not lead to the same amount of
problems with internal circuit noise or radio frequency noise. On sites with a lot of trash, you can
often improve the discrimination and the audio sounds of targets by lowering your sensitivity and
coil voltage. Remember that you are hunting by audio signals only and the adjustments you make
should always be made to improve the targets audio characteristics.
Copyright © 2004, J. L. Sims Jr.------USED WITH PERMISSION & MANY THANKS!!
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Metal detecting with the DMC-IIB or IIBa on saltwater beaches requires different techniques. When hunting the dry sand above the high
have to hunt in the non-motion discrimination mode. In this mode you can cancel the salt wet sand out by using the Discriminate vernier
dial control. Make sure you have balanced your coil before proceeding. Make sure the autotune switch is off when balancing to the wet
balance the ground balance set up but use the Disc. control. Each time you let the coil to the ground, turn the disc. one line at the time, it is
up turn control up. This mode works backwards than does the ground balance side. Normally on the ground balance side you would turn
to the ground your tone will hardly change, this is when it is set.
Remember, each time you turn the disc. control and let the coil to the ground, push the red pushbutton and reset the threshold tone to
normal. In the non-motion disc. mode the ground balance control is completely out of service, it could be set at 10 or 100, it does not
After the machine is set to the sand you now can cut the autotune switch back on, but remember if you stop over the target it will retune
the audio as if there were nothing there. In this mode the threshold tone will rise on a good target and the tone will go down or dead on a
bad target. You will not get the beep in this mode to tell you it is a good target, just the tone rising.
You will notice some change in the setting of the tone the closer you get to the drier sand but it is easy to pick out a target because it will
be a sharper response. When I hunt the wet sand I usually set up the machine as close as I can to the water without being in the water
and hunt parallel to it for a couple hundred yards and then move up about five feet and hunt back. I have found that most of the time the
targets would be in a streak about the same distance from the water and usually I have found the bigger rings down closer to the water
after a storm mixed in with the fishing weights. I have noticed if you find a lot of fishing weights in an area there will be a ring or two in that
Remember when you get back into the dry sand you can switch back to the ground reject mode.
By Don Turlington, Nautilus Factory Technician