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JW Fishers Proton 4 Magnetometer with 150' Cable Metal Detector

Sku: 569-20
Retail: $12,995.00
Now Only: $11,899.00
The Most Powerful Boat Towed Metal Detector for Ferrous Metals

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JW Fishers Proton 4 Magnetometer with 150' Cable Metal Detector
The Most Powerful Boat Towed Metal Detector for Ferrous Metals

The Proton 4 is the ultimate detector for iron and steel targets. It has a one nano-tesla sensitivity, which is the maximum practical sensitivity for a towed magnetometer. It's maximum range capability of 1500 feet on each side (3000 foot total swath) lets you search a wide area quickly and completely. The mag is also a good choice to locate a variety of smaller targets such as pipelines, anchors, chains, cannons, dredge heads, etc. It is especially useful when objects are buried in the bottom and can't be found with sonar or video search systems. The detection range is unaffected by the medium between the magnetometer and the metal target. Performance does not change whether detecting through air, water, silt, sand, or solid coral. It's extremely large detection area make this magnetometer the ideal choice for both commercial operations and professional wreck hunters. The Proton 4 is in use by military units, law enforcement agencies, and commercial diving companies world wide.

This high performance marine magnetometer is ruggedly built and easy to operate. The topside console has both audio and visual alarms for target detection. Connect a GPS and position coordinates with mag readout data can be captured with the optional Tracker software. The control box has an adjustable sensitivity switch that lets the operator select maximum sensitivity for open water searches or a lower sensitivity setting to work in rivers or harbors where steel structures may be nearby. A cycle time switch lets the operator choose a 2, 3, or 4 second cycle time. An adjustable audio alarm lets the operator decide how much of a change in the baseline reading will cause the alarm to fire. When searching for small targets, low alarm settings alert the operator to small changes in the readout. Higher alarm settings cause the alarm to fire only when a significant ferrous metal object is detected.

When a target is detected, the readouts and coordinates change color so the operator can quickly see when and where a target is detected. At the bottom left of the screen is a graphical representation of the last 1 minute to 1 hour of mag readouts. When a target is detected a spike or deep V is drawn on the graph. In addition to the mag and GPS data, other information displayed are the boat's speed, compass heading, and the sensitivity setting selected by the operator. The Tracker map can be exported as a image with a KML file to allow it to be easily overlaid on other mapping programs (as shown at the right). All data can be stored on the PC hard-drive or disk.

The Proton 4 system includes the towfish, 150 feet of Kevlar reinforced and urethane coated cable providing a strong tow member, and a top-side control unit. The control unit features easy to read LCD display, audio alarm, and variable sensitivity switch (for pinpointing targets). The complete system is powered by two 12 volt batteries with a total power consumption of only 40 watts.


  • Warranty : 2 Year UNCONDITIONAL
  • Depth : 1,500 ft. Detection Range
  • Construction : Commercial Grade
  • Sensitivity : One Gamma Sensitivity
  • Tow Speed : 1 to 10 Miles Per Hour Tow Speed

Factory Included Accessories:
  • Tow Fish
  • Top-Side Control Unit
  • 150' of Kevlar Reinforced and Urethane Coated Cable

Additional Information

Not currently available.

JW Fishers Proton 4 Magnetometer with 150' Cable Metal Detector

Proton 4

The Proton 4 is a fourth generation proton magnetometer from JW Fishers. It is a top performing microprocessor driven marine magnetometer detection system. With a one gamma sensitivity, it has the maximum usable sensitivity for a towed magnetometer. A two second cycle time gives a strong return signal and is fast enough to detect even small iron/steel targets. The PROTON 4 features a triaxial noisecancelling sensor that allows omnidirectional towing without heading error or dead zone. The system is fully digitized and displays it’s output on an easy to read 5 digit LCD that is backlit for night operations. An alarm informs the operator when the readout changes.

The base system includes a 200 foot depth rated towfish, 150 feet of cable, and topside control box. Target position is displayed and recorded on the computer.

The Fish has excellent hydrodynamic characteristics moving smoothly through the water at tow speeds up to 10 knots. A 2-3 knot tow speed is recommended for small targets. With the optional Altimeter, precise distance off the bottom can be maintained. For deep water towing, the Fish is towed behind a downrigger. The Fish can be towed at almost any speed, but should be towed slow to locate small targets or when towing the Fish deep. A sensitivity switch allows easy pinpointing of targets. Modular construction allows easy field repair, should it ever be necessary.


Magnetometers are precision electronic instruments that measure and display the strength of the earth’s magnetic field in an area. If ferrous metal is present, the earth’s magnetic field is altered and the readout of the magnetometer changes accordingly.

Since the 1940’s, almost every major wreck find was made with a magnetometer. Metal hulled ships and barges are easy targets and can be detected hundreds of feet away. The Spanish galleons laden with gold and silver (metal not detectable by magnetometer) were also found with mags by detecting the ship’s anchors, cannons, cannon balls, or ballast stones (magnetite was often used as ballast).

Proton Magnetometer

In the 1960’s, the proton magnetometer (as we know it today) was invented. Since that time the proton magnetometer has dominated the field, both in the scientific community and in salvage work. It is both a rugged and sensitive instrument. The claim to fame of the proton magnetometer is, unlike flux-gate mags, the orientation of the sensor head does not alter the out-put reading. Once this mag is tuned to an area, no further adjustments are necessary.

Proton 4

The PROTON 4 is a proton magnetometer that was specially designed for underwater salvage work. The system consists of a Control Box, a150-1,000’ cable and a towfish.

Fish : The Fish is 52 inches long and has a watertight compartment that contains the sensors and the electronics necessary for processing the signal before sending to the control box. The Fish has four fins for stability and is weighted for negative buoyancy. The materials used in the construction of the Fish were specifically selected for high impact resistance and low maintenance.

Cable : The 150-1,000’ tow cable consists of multi-paired and coax cables encased inside a braided polypropylene rope. The combination results in a highly abrasion-resistant tow cable.

  • Readout : A five digit LCD readout displays the gamma reading. The readout is backlit for nighttime viewing.
  • Sensitivity Switch : A four position switch allows the sensitivity to be reduced once a target area is located, so the target can be accurately pinpointed.
  • Pol Time : A three position switch controls the cycle time. 2.5 ,3, or 4 seconds can be selected.
  • Alarm : A seven position switch sounds an alarm if the readout changes beyond the selected gamma amount.

Operation and Use

When you receive your Proton 4, it has been tuned at the factory and is ready to operate; all you need are two 12v batteries (car or marine type) for power. Included with the Proton 4 is a large world map. The map shows the gamma reading for different parts of the world; e.g. 61,000 for the North Pole area (magnetic field is strongest), to 24,000 in Ecuador, S.A. (magnetic field is weakest). You check the map for the reading in your area; e.g. Boston, Mass. = 55,000; Miami, Florida = 48,000. The tuning switches in the Fish is set to the position that covers this frequency (each switch position covers a broad band of frequencies). At this point, the Proton 4 is “tuned” and ready to go. The Power On switch on the Control Box is turned on and the unit automatically begins cycling. The gamma reading and LORAN or GPS coordinates will be printed. With the optional RS232 output interface the information can be output to any computer or software program.

NOTE : In most areas of central South America (i.e. Brazil) the magnetic field is so weak that operation of a magnetometer is not reliable. Contact the factory if you plan on using the mag in SA. When towing the Fish, as you approach a ferromagnetic (steel) target, the readout number will decrease; the amount of decrease will depend on the size of the target and how close the Fish passes to it. A change of several thousand can be expected for a very large target. The Proton 4 can easily pinpoint wrecks.

The Proton 4 is backed by JW Fishers exclusive, UNCONDITIONAL TWO YEAR WARRANTY.

Technical Specifications:

Detection Ranges

ObjectNear RangeFar Range
1 Gallon Can - 2 Gamma at 12’
5 Gallon Can - 2 Gamma at 18’
55 Gallon Can - 2 Gamma at 45’
Small Plane 25 Gamma at 20’ 2 Gamma at 50’
6'' Pipeline 200 Gamma at 20’ 2 Gamma at 100’
12'' Pipeline 350 Gamma at 20’ 2 Gamma at 175’
Large Anchor 500 Gamma at 50’ 2 Gamma at 200’
Medium Ship 1500 Gamma at 100’ 2 Gamma at 1000’
Large Ship 2000 Gamma at 100’ 2 Gamma at 1500’
  • Performance / Descriptions
    • Fish : 52” L x 6” D (48 lbs)
    • Control Box : 14” L x 10” W x 6” H (5 lbs)
    • Carry Case - 59” L x 18” D x 22” H (80 lbs)
    • Tow Line : .375” D x 150' -1,000' (15 to 100 lbs)
    • Total Shipping : 59” L x 18” D x 22” H (170 to 350 lbs)
  • Dimensions / Weights
    • Tow Speed : 1-10 MPH
    • Power Consumption : 400 Watt
    • Input Voltage (two car batteries) : 24 VDC
    • Maximum Detection Distance : 1,500 Feet
    • Cycle Time (switch adjustable) : 2-4 Seconds
    • Sensitivity (switch adjustable) : Resolves 1 Gamma
    • Maximum Operating Depth (standard unit) : 200 Feet
  • Materials / Color
    • Control Box - High Impact Case / Black
    • Fish : High Impact PVC, Stainless / Yellow
    • Cable : 10 Conductor with Kevlar Strength Membrane / Yellow


  • Warranty : 2 Year UNCONDITIONAL
  • GPS Output
  • Commercial Grade Construction
  • Depth : 1,500 ft. Detection Range
  • Construction : Commercial Grade
  • Sensitivity : One Gamma Sensitivity
  • LCD Gamma Readout and Target Alarm
  • Tow Speed : 1 to 10 Miles Per Hour Tow Speed
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