I need to know

[detectorandy]

I just got back from the beach this past weekend, I use a White's spectrum xlt. Set on the beach settings and all other settings every time I got close to the water or detected on wet sand and hit the head of the unit on the sand it beeps, in dry sand it works fine. I wsould like to ask, why does it do this ( is it broken) and what is a good beach detector (price dosn't matter)?
Thanks All

 

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[detectorandy]

Thanks to everyone who gave me advise, I am looking in to all that was given and weighing out my options. Please keep your advise comming.

 

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[Rudy(CA)]

The machine is transmitting a rectangular current pulse at some pulse repetition frequency.
All machines do that.

What happens was explained by a French mathematician (named Fourier) many years ago.

Basically, that repeating rectangular current pulse is made up of a "fundamental" frequency,
given by the pulse repetition frequency, plus a series of harmonic frequencies of decreasing
amplitudes. So, what Minelab is doing is using multiple detectors tuned to the fundamental
and some of the harmonic frequencies and analyzing the target response at those frequencies.
Here is a graphical examlpe of a Fourier series in action.

 

[detectorandy]

Thank you Rudy, but all that is way over my head.

 

[Monty]

Uh....yeah, what Rudy said! That's what I meant. Well put Rudy! (Don't want everyone to know I'm as ignorant about those things as I really am) Like I said in another post, electricity is invisible, tasteless and odorless but it's still there, but it really is just plain old magic. So if someone asks me a technical question I always have the right answer.......It's magic! JIM

 

[Rudy(CA)]

Ok, so not everyone here is a E.E.

Let me rephrase.

The transmitter sends a pulse of current to the transmit coil at some given repetition rate.

The energy in that current pulse can be mathematically described as a set of many different frequencies.

The lowest frequency and the one that has the most energy is called the fundamental and it is equal to the
pulse repetition rate. In this case, 1.5 KHz (or 1,500 cycles per second).

The other frequencies are called harmonics and are multiples of the 1.5KHz. For example, 3KHz, 4.5KHz, ....

The hooker is that as the harmonic frequencies get higher, the amount of energy in them decreases. As everyone
here knows, the lower frequencies are hot on silver and the higher frequencies are hot on gold (that is why gold
machines usually run at higher frequencies), so this tends to comensate the fact that the detector is transmitting the higher frequencies with lower energies.

Most detectors analyze the target in what is called the time domain. In other words, a pulse is transmitted, this induces a current in the target and depending on the conductivity of the target, this induced current decays at some rate. The net effect is that this changes the signal received by the received coil and detection is made.

What makes the Minelab unique is that instead of analyzing the target decay response in time, it is looking at the decay response at several of the frequency components that the transmit coil generated (remember Fourier?). The claim is
that this provides a more accurate and deeper assessment because different targets will react differently.

Hope this was a little easier.

 

[detectorandy]

I can say that I now understand. I was told that I need to get me a White's PI. Is this a good machine?

 

[Bill(de)]

Hi Randy,
Since your using an XLT at a Salt water beach i'm assuming your not a dedicated beach hunter and if thats the case i would forget a PI machine of any brand. If you occasionally hunt the salt beaches and want a great detector for land and beach get a Sovereign or a Fisher CZ unit. you will have fun on land and at salt beaches with either. The Sovereign is the land version of the Excaliber and the CZ land unit is same as CZ 20 only that they can't get wet.The reason your getting a beep when you touch the coil to the wet sand is the XLT reads the salt as a metal and i think it's close to 00 reading on the XLT.Whatever you choose i wish you luck . HH Bill

 

[neilo]

Best using minelab Sovereign or Excalibur on the beach I have both and wether in wet or dry sand or as they call black sand you will get clear signals.The Excalibur is a full time underwater detector which can be heavy on land to use but there is a harness available for hip mounting made by minelab this takes the load off.Both detectors work on the same circutry the only difference is the sovereign has an additional notch discrimator as well as the normal dicriminator.I have used both of these for years and have found countless goodies with them.Best effort fourteen rings in four hours, four of them gold .
new to this forum from down under neil o