Towing a magnetometer fish directly beneath a small inflatable.

[Jolly Mon]

I have an old J.W. Fisher's proton 3 mag and was thinking that it might be possible to drag the fish directly beneath a small inflatable with a 9.9 hp outboard. The depth of drop for the fish would vary, but I am primarily interested in relatively small targets in shallow water, so 10 to 15 feet from the bottom of the inflatable to the fish would be ideal.

I can keep the amount of ferrous material on the inflatable to a minimum, but obviously the outboard is the big bugaboo.

Will the error introduced to the mag from the outboard remain relatively consistent during slow straight runs?

Will it greatly affect the sensitivity of the mag?

I actually got the idea from the method JW Fishers recommends for pinpointing in the Proton 3 manual.

I love the idea of being able to tow the fish directly beneath the boat for obvious reasons and was wondering if anyone has ever tried this method or anything similar.

 

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[lukdiver]

Whenever we're magging we tow the fish 50'+ behind the boat. Hard 180-degree turns will cause a acylation of the fish and trigger a false hit. We just mark it on the gps and make sure we pass over it again to eliminate it. This was on a recent search in 10-15'(often less) of water weaving amongst breaking rocks. Quite thrilling. Normally in deeper water we pull a 'mag bouy' behind the boat (its one end has the lead-weight trailing directly behind bouy. When we have a hit we want to mark we simply release the boat end and weight drops to the bottom while line runs thru the bouy. This puts the bouy almost directly over the top of the hit. Because of magnetic field tilt we usually drop when we hit the null. Hopefully I've explained this but I'll reply to any questions you may have. Most of our recent magging is West Coast of US and often in highly geologically-disturbed areas.

 

[Jolly Mon]

Well, I found the answer to my own question on page 73 here:http://www.3hconsulting.com/Downloa...ques Theoretical Study Final Report Rev 2.pdf

I would delete the original post but I think the answer to the question is very interesting.

 

[Jolly Mon]

Whenever we're magging we tow the fish 50'+ behind the boat. Hard 180-degree turns will cause a acylation of the fish and trigger a false hit. We just mark it on the gps and make sure we pass over it again to eliminate it. This was on a recent search in 10-15'(often less) of water weaving amongst breaking rocks. Quite thrilling. Normally in deeper water we pull a 'mag bouy' behind the boat (its one end has the lead-weight trailing directly behind bouy. When we have a hit we want to mark we simply release the boat end and weight drops to the bottom while line runs thru the bouy. This puts the bouy almost directly over the top of the hit. Because of magnetic field tilt we usually drop when we hit the null. Hopefully I've explained this but I'll reply to any questions you may have. Most of our recent magging is West Coast of US and often in highly geologically-disturbed areas.

Love the "mag buoy".

 

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[ARC]

Why not... ?

 

[xaos]

Normally in deeper water we pull a 'mag bouy' behind the boat (its one end has the lead-weight trailing directly behind bouy. When we have a hit we want to mark we simply release the boat end and weight drops to the bottom while line runs thru the bouy.

In deeper water? Mag hits are easier to locate in deep water....Towing a buoy in deep water to drop on a target??

I think you meant towing a buoy in shallow water....

 

[NOLLIDER]

Tow the mag being the boat under a "Dutchman Bouy "

PM me if you want a drawing or details on how to rig a "Dutchman Bouy"

 

[Red_desert]

Whenever we're magging we tow the fish 50'+ behind the boat. Hard 180-degree turns will cause a acylation of the fish and trigger a false hit. We just mark it on the gps and make sure we pass over it again to eliminate it. This was on a recent search in 10-15'(often less) of water weaving amongst breaking rocks. Quite thrilling. Normally in deeper water we pull a 'mag bouy' behind the boat (its one end has the lead-weight trailing directly behind bouy. When we have a hit we want to mark we simply release the boat end and weight drops to the bottom while line runs thru the bouy. This puts the bouy almost directly over the top of the hit. Because of magnetic field tilt we usually drop when we hit the null. Hopefully I've explained this but I'll reply to any questions you may have. Most of our recent magging is West Coast of US and often in highly geologically-disturbed areas.

Maybe somebody on the forum here could explain setting up a computerized mag for eliminating hot minerals.

 

[Red_desert]

What is the difference between a differential magnetometer and computerized, or are they the same thing?

Here is link on differential info.


https://tf.nist.gov/ofm/smallclock/Differential_Magnetometer.html


We have developed a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over that of single-channel operation. The design is well suited to wafer-level mass production of chip-scale devices.


We have developed a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over that of single-channel operation. The design is well suited to wafer-level mass production of chip-scale devices.