help on the sand

[Spencer M]

Hi All
im new to this so have been doing some beach searching while trying to get some permission inland (much harder to get than I thought it would be) anyway I think im sorted on the stones 90% of the time if I get a decent beep I find something normally tin foil or a bottle top but at least im finding something, but on the sand i get false alarms every couple of steps, am i doing something wrong, do I need to change my settings my sensitivity is on about half way or is it just because I have a cheap starter detector ( terratek TTMD18CM)
Any help you guys can give would be great

[Koala]

Most likely just the beach you are on.


Where about are you ?

[moggers]

It is called falsing .. certain detectors just cant handle wet sand because of the mineralisation. You need a detector with ground balance to be able to handle this and these are usually more expensive. Another option would be to get a pulse induction or PI detector but these dont descriminate the iron trash out so you dig a lot of holes. CScope CS4pi is a nice cheap PI machine, I have one and even though I own a CTX3030 I still get out regular with my cscope.

Hope this helps.

[sweepstick47]

Hello 'Sprencer M' Just thought I'd jot down a line or two as you are 'new to this'.

I have no electronics training and this is purely my own take on the causes of 'falsing'!

You appear to have a basic model, which is probably TR/IB in design (2 coils within the search-head). There's nothing wrong with that if it's a 'motion' machine and operates in the 'VLF' RF Band of 3 Hz to 30 Khz. 'VLF' is better placed to penetrate mineralised ground.

These machines can be operated on salt wet sand, (not easily and with only limited success) but the discrimination setting (if there is one) needs to be be set 'higher' than is normally recommended (resulting in the loss of some low conductive but desirable targets, thin section gold rings, chains etc). The sensitivity/gain setting can be lowered to further limit the 'falsing effect'.

The 'falsing' you're experiencing, is caused by the imbalance created between the transmit and the receive coil which occurs when there is even a slight change in the height of the search-coil whilst 'swinging' above conductive wet sand. Dry sand comprises both negative and positive minerals but when sea/saltwater is present, it becomes positively charged (conductive) to indicate a 'good' sounding but 'false' target response.

In reality, the task of maintaining an accurate coil height when searching wet sand with such a machine, is generally accepted as unworkable if not impossible. Multi-Frequency or Pulse Induction detectors are considered to be the best operating system for detecting on wet sand.

More technically capable members will hopefully point out any errors in the above.
Wishing you well - Regards ss47