VLF or PI ?

[jackdetect]

Hallo fellows,
If we highly increase transmit power in VLF metods with serial LC transmit coil (of course with different coils arrangement), can we get similar detect depth, like in Pi detectors?
I think, we still can keep in use ground balanse and discrimination.
Any experience?
Where can I find concrete informations about dual voltage technology? Any pattent?
Help Me !

Salute,

Jackdetect.

[Reg]

Re: VLF or PI ?

Hi Jack,

There have been attempts to raise the voltage or power into the coil to increase depth. The TEK ST did that, the Treasure Baron has an add-on board that allows the voltage to be increased. I have been informed that the Nautilus does something similar.

I owned the Tek ST and the TB, both of which could increase the power. I found I could hear targets a little better in the all metal mode, but really didn't see any depth increase in the disc mode. I suspected the reason there was no obvious depth increase was because of the extreme mineralization where I was trying them. My guess is they would work much better in low mineralized areas.

Now, increasing the power into the coil does increase the signal strength but it does it for all things including the ground signal. So, it will be tougher to ground balance as the power is increased.

Also, it takes a significant power increase for each inch increase in depth. If I remember correctly, one would have to basically double the power to add 1 inch. Now to add another inch, the new power would have to be doubled again, etc, etc. As one can tell, it doesn't take long before it takes a "huge" battery to get any more increase.

As for a patent on the dual voltage technology, I would just scan through the ML patents here on Carl's website. I think one of the later ones does refer to it.

Also, there was a brief discussion on the PI forum about it a while back. I think Eric mentioned the different voltages involved between the two pulses used on the ML PI's. So, you might do a search over there also.

Hope this helps.

Reg

[Beachcomber]

Re: VLF or PI ?

The new Tejon's and Shadow X-3's and X-5's also run higher transmit voltages to attain thier greater depths.

I hunt in lower mineralized areas and when the ST's high voltage section was activated I did get more depth in Disc mode as well as in All Metal. This increase in depth was on the order of 4-5 inches when cranked all the way. In my area I was able to run the ST at full power. It was an awesome machine. Geroge Payne really knows how to make a detector! I wish he was still designing detectors for the hobby!!! Then we probably wouldn't have so many repackaged old detectors coming out as new right now!!!!


HH

Beachcomber

[jackdetect]

Re: VLF or PI ?

Hi Reg,
Thanks for information.
Problem of drastic drooping Em field is the same for Vlf and for Pi.
Vlf detectors usually sends couple of mA into transmit coil. This means max. 100mW transmit power.
If we send more power, I think we will have big problems with null balance in standard search coils.
On my experience, standard metal detectors work only 60 cm deep in ground (with search coils until 40 cm diameter). If you count grass, bumpy terrain and ground noise, range become much worse.
I think that most owners of metal detectors, ignore the truth about detection range in ground.
I read much rhetorical telling on the forums, but not much usefully information. I think, many variations on the same theme.
If we want construct efficient detector, I think we must change concept of search head.
I try to construct something between classic metal detectors and Em geophysical locators.
But I still have dilemma: Vlf or Pi ( Frequency domain or Time domain ).
I think Vlf concept have more advantages than Pi, of course if we use more transmit power. But I am not sure.
Lets make something like 3 box detector!

Patent with interesting ideas:

http://www.thunting.com/geotech/pages/metdet/patents/US5039946.pdf

Is somebody trying some similarly?

Salute,

Jackdetect.