Shadow VLF Metal Detector

Eugene52

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Teknetics , Fisher , Discovery3300 and TIANXUN 19 kHz VLF Metal Detector

	Re: Shadow VLF Metal Detector « Reply #20 on: February 14, 2009, 09:35:32 pm »

	Quote:	Posted by oldsparks
Hello The same circuit somewhat altered appeared in the December 1980 mag. With some mistakes corrected in later issues of ETI.

In the September 1980 issue of the U.K. "ETI" Magazine are the corrections we need . Unless someone posts the article here , I suggest you build a different project , like a Tesoro or a P.I. from our "Tech Talk" area !!..............Regards..............Eugene52

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	Re: Shadow VLF Metal Detector « Reply #21 on: February 17, 2009, 01:49:26 pm »

Thanks for recommending search coils for the Altek Shadow.

I built that unit years ago (in 1996 from the date on the pcb) but the home made coils were no satisfaction. Altek used a very particular arrangement of the tx and rx coils.

Incidentally I came across a cct for a tesoro that caught my eye. the tx and rx are similar to the shadow. so is the waveform shaping section as well as the osc. the integrator and signal processing I assume is an improvement.

Any idea what coil config are used?

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Eugene52

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Teknetics , Fisher , Discovery3300 and TIANXUN 19 kHz VLF Metal Detector

	Re: Shadow VLF Metal Detector « Reply #22 on: February 17, 2009, 02:20:34 pm »

	Quote:	Posted by oldsparks
Thanks for recommending search coils for the Altek Shadow. I built that unit years ago (in 1996 from the date on the pcb) but the home made coils were no satisfaction. Altek used a very particular arrangement of the tx and rx coils. Incidentally I came across a cct for a tesoro that caught my eye. the tx and rx are similar to the shadow. so is the waveform shaping section as well as the osc. the integrator and signal processing I assume is an improvement. Any idea what coil config are used? [/quote A coplaner is used , not a widescan DD. See the attachment I posted . The crooks at Altek wanted you to buy the search coil and not build it yourself . That is why they posted the article , to sell you something !! The article only speaks of the 180 degree phase advance needed for proper discrimination . A tesoro coil will work with some changing of the circuit capacitor. Just build a Tesoro metal detector project , and you will be very happy of the results.................... ..........................Eugene52 Linkback: You are not allowed to view links. Please Register or Login http://www.thunting.com/smf/index.php/topic,3325.msg24522.html#msg24522

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	Re: Shadow VLF Metal Detector « Reply #23 on: February 18, 2009, 12:30:28 pm »

Thanks for the info. For one thing it has solved a long outstanding question regarding the third coil.

I might do as you suggest. I?m beginning to like the idea. Thanks.

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	Re: Shadow VLF Metal Detector « Reply #24 on: February 23, 2009, 10:39:30 pm »

I use an old Whites v/Sat, i get a decent signal at about 10 inches, would it be better to just go bigger than the stock coil if im mainly shooting for small nuggets, or should i stay with the small coil for that?

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Teknetics , Fisher , Discovery3300 and TIANXUN 19 kHz VLF Metal Detector

	Re: Shadow VLF Metal Detector « Reply #25 on: February 23, 2009, 11:25:47 pm »

	Quote:	Posted by OregonGold
I use an old Whites v/Sat, i get a decent signal at about 10 inches, would it be better to just go bigger than the stock coil if im mainly shooting for small nuggets, or should i stay with the small coil for that?

Hello OregonGold and welcome to the "New and Great" Thunting.com Forum !!! Up-grading to a larger search-coil means you will increase the magnetic field deeper into the ground but you will decrease the magnetic field closer the surface , missing small targets that you would have detected before on your smaller coil , and deeper targets must be bigger than before to get the recieve coil to register !! In other words , bigger coils are good for bigger targets , not small coins deeper !! Shocked