What towed metal detector were you using? Was this true for any size steel ship? Old wooden ships would not have much large metal content except for anchors and chain.

A metal detector has a sensitivity proportionally depending on the mass of metal and inversely proportional to the fourth power of the distance. THis is a physical rule applicable to any insturment using an ACTIVE electromagnetic technology.
A magnetometer has a sensitivity proportionally depending on the mass of ferrous material and inversely proportional to the third power of the distance. This is the rule for a PASSIVE electromagnetic technology detecting a dipole.A target looking like a monopole (e.g. a pipeline) changes the third power to the second power, wwhich makes them detected at even larger distances.
That means that a mag is able to detect targets of given mass at a much larger distance than any metal detector if the material of the target is MAGNETIC, which is mostly the case of old wrecks and their cannons and anchors.

Go there and you will find a PPM unit with a good performance/price ratio : http://users.skynet.be/fa352591/index.htm

Willy

Hi Willy,

Your PPM Mag looks great. Congratulations. Look forward to hearing of more results of the Underwater Mag project.

My interest in the boat towed underwater metal detector is looking for non-ferrous objects such as an aluminum aircraft wing.

It's great device and very useful for present and future reference work. I'm excited to use this detector for my personal use.



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