FISHER RESEARCH LABORATORY
200 West Willmott Road
Los Banos, California 93635
Tel 209.826.3292 Fax 209.826.0416
www.sherlab.com email:info@sherlab.com
Q U A L I T Y
Fisher detectors are renowned for their quality.
Each detector is hand crafted in the USA with pride.
PERFORMANCE
Treasure Hunters worldwide rely on Fisher.
Our detectors are durable, dependable, and search deeper..
REPUTATION
Fisher produced the rst patented metal detector in 1931. For
over 70 years, the Fisher logo has been a mark of excellence.
5 - YEAR LIMITED WARRANTY
Fisher believes in the products they produce and backs this be-
lief with a 5 year limited warranty. Warranty may vary outside of
the United States. See your dealer for details.
S E R V I C E
Fisher is committed to providing their valued customers, with
superior service. Each and every instrument is rigidly tested and
carefully inspected during assembly and before shipment.
Should you have any questions or problems, contact:
FRL#870352-K
Gemini-3
Operating Manual
Deep Search, Two Box Metal and Mineral Detector
F I S H E R R E S E A R C H L A B O R A T O R Y
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CONTENTS
About Your Gemini-3 ...............................................................pg. 3
Basic Theory of Operation .......................................................pg. 4
Depth .........................................................................................pg. 5
Transmitter .................................................................................pg. 6
Receiver ....................................................................................pg. 7
Searching...............................................................................pg. 8
Narrow Scan Inductive Search ...............................................pg. 8
Set Up -Narrow Scan Inductive Search ..............................pg. 8
Tuning -Narrow Scan Inductive Search ..............................pg. 9
Operation -Narrow Scan Inductive Search ........................pg. 10
Wide Scan Inductive Search ...................................................pg. 12
Set Up -Wide Scan Inductive Search ..................................pg. 12
Tuning -Wide Scan Inductive Search ..................................pg. 12
Operation -Wide Scan Inductive Search ...........................pg. 13
Tracing .......................................................................................pg. 14
Inductive Tracing ..................................................................pg. 14
Set Up -Inductive Trace ........................................................pg. 14
Tuning -Inductive Trace ........................................................pg. 14
Operation -Inductive Trace .................................................pg. 15
Conductive Trace .....................................................................pg. 15
Set Up -Conductive Trace ....................................................pg. 15
Tuning -Conductive Trace ...................................................pg. 16
Operation -Conductive Trace .............................................pg. 16
Prospecting Tips ........................................................................pg. 17
Mapping ................................................................................pg. 17
Locating Placer Deposits ......................................................pg. 17
Sources of Error......................................................................pg. 18
Battery Replacement ...............................................................pg. 19
Treasure Hunters’ Code Of Ethics ............................................pg. 20
Where To Use Your Metal Detector In The U.S. ......................pg. 21
Specications ...........................................................................pg. 22
23
Notes
1. Subject to improvement or modication without notice.
2. Approximate.
3. Voltage Controlled Oscillator. Volume and pitch
both increase as target is approached for easier, more
accurate pinpointing.
4. With optional ground plate assembly.
5. Optional stereo/mono headphones.
6. Use of headphones will signicantly increase battery life.
Fisher Research Laboratory does not warrant suitability to
specic use. Fisher Research Laboratory shall in no event be
liable for any direct, incidental, consequential or indirect
damages.
SPECIFICATIONS
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3
ABOUT YOUR DETECTOR
Two-box metal detectors have long been used by
prospectors, geologists, treasure hunters and public utility
companies to locate large, deep objects, ore vein, pipes
and cables. Fisher Research Laboratory is the recognized
leader in the eld, in fact, they were granted the rst two-box
metal detector patent over 60 years ago.
You might think it would be difcult to improve on a product
that has been in a constant state of development for so many
years. But the fact is, the GEMINI-3 is probably the biggest
leap forward in two-box design since it replaced vacuum
tubes with transistors back in the 1950s.
The new GEMINI-3 goes 10 to 20 percent deeper than its
predecessor. It will trace most pipes and ore veins at least
50 percent farther, and the new crystal controlled circuitry
is rock stable. The old metal-rim antenna is gone and so
are the hard-to-get batteries. The GEMINI-3 is easier to use,
two pounds lighter, & features Voltage Controlled Oscillator
(VCO), audio target response for precision pinpointing.
Your Fisher GEMINI-3 is a high quality, precision instrument
engineered by the oldest and proudest name in metal
detectors. Treat it right, read this instruction manual thoroughly
and practice often. Who knows, with skill, patience and a
little luck, you may nd the BIG ONE.
Drop us a line if you have any questions, comments or
exciting GEMINI-3 stories. In the meantime . . .
Happy hunting,
FISHER RESEARCH LABORATORY
22
SPECIFICATIONS
Dimensions
Length on handle ............................................................49 1/2 inches
Transmitter-Receiver Box Assembly
.................................................9 1/4 x 12 x 6 inches(23.5 x 30 x 15 cm)
Weight
Complete ...........................................................................7 lbs. (3.2 k)
Transmitter ........................................................................2.4 lbs. (1.1 k)
Receiver ...........................................................................2.9 lbs. (1.3 k)
Handle ..............................................................................1.7 lbs. (.75 k)
Frequency
RF Search and Trace ............................81.92 KHz Crystal Controlled
................................................. Audio Target Response (VCO)
Operating Modes
Search
1. Narrow Scan, Inductive
2. Wide Scan, Inductive
Trace
1. Inductive
2. Conductive
Target Response
Meter ......................................................2 1/4 x 1 3/4 inches, Analog
Speaker ............................................................2 1/4 inches, 100 ohm,
Moisture Proof Cone
Headphones ..........................................1/4 inch Jack, 8-16 ohms,
............................................................................................Stereo/Mono
Batteries
Receiver .............................................................................. (8) AA 1.5V
Transmitter .......................................................................... (8) AA 1.5V
Life ...........................................Carbon Zinc ............................30 Hours
.................................................Alkaline .................................... 50 Hours
2
3
4
5
62
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4
BASIC THEORY OF OPERATION
The GEMINI-3 was engineered to detect conductivity
changes in the earth over which it is carried. Hence, a positive
response by the GEMINI-3 indicates the presence of a metal
object, ore vein or mineral that is more conductive than the
surrounding rock or soil.
The function of the GEMINI-3 Transmitter is to send a radio
frequency (RF) signal down to a conductive object and
generate an electromagnetic eld around that object.
When used in any of the Inductive modes, the RF signal
travels through the ground to the object. When used in
the Conductive Trace mode (see page 13), the signal is
transmitted directly through a wire attached to an exposed
portion of the object.
The function of the GEMINI-3 Receiver is to locate the
object by detecting the electromagnetic eld around it and
responding with audio and visual signals.
21
National Forest and Federal Lands—Metal detecting is allowed
only by special permit acquired from the federal government.
Each area has a district ofce.
Corps of Engineers, Lakes, Shorelines and Lands—Permission has
been granted only on predisturbed sites, such as beaches and
attached swimming areas. New Corps lakes and lands must be
okayed by the main ofce of the Army Corps of Engineers. Each
area has a district ofce.
State Parks and Lands—Some state parks are open to metal
detecting, but some are not. Always check with the park ranger
before attempting to use your detector.
Bureau of Land Management (BLM) Lands—Some areas are
open for metal detecting, and some are not. Always check with
the district ofce.
City or County Park Lands—Most are open to metal detecting
unless notice is given by a sign or city ordinance. When in doubt,
always check with the city’s Parks and Recreation Department.
Public School Grounds—Most are open to metal detecting unless
notice is given by a sign, city ordinance, law enforcement ofcial,
or school employee. You should always check with the school
ofce rst.
Privately Owned Lands (Private Property)—Permission required. It
is always best to have the permission in writing.
Historically Marked Lands or Sites—Metal detecting is not
allowed. Don’t even think about it.
Where To Use Your Metal Detector In The U.S.
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