Whites tdi depth while prospecting for gold

[Smigo]

I know absolutely nothing about any of the Tesoros. I don't even know if the Tejon is a PI. Increasing the voltage only benefits pulse-induction machines. Does nothing for VLF detectors. But VLF's can benefit from switching to rechargeable li-ion batteries, but only because they're rechargeable, and you don't have to buy batteries.
Jim

Tejon is VLF. I own a Garrett 24k VLF. It has increased Voltage to the coil, around 50%, but that does not equate to 50% more depth. It just gives a bit more stability and sensitivity. Increase in depth is minimal. But it does give some more sensitivity to small gold. And I mean small, speck stuff. But, it is a great VLF and id venture to say probably the top of the heap VLFs these days.

 

[Odanscoils]

Tejon is VLF. I own a Garrett 24k VLF. It has increased Voltage to the coil, around 50%, but that does not equate to 50% more depth. It just gives a bit more stability and sensitivity. Increase in depth is minimal. But it does give some more sensitivity to small gold. And I mean small, speck stuff. But, it is a great VLF and id venture to say probably the top of the heap VLFs these days.

Thanks Smego.
Yup that 24k is really interesting me
I'm also looking for a pi machine for retirement.
We all wanna see that rainbow sitting in that big oll pot of gold.
This new Tejon I picked up eats batteries..
8 of em at a time.
Actually a little surprised at thst.
My other Tesoro seems to run forever compared to it. The Tejon goes quite deep fo what it is.
I was just thinking about the 18650 battery change back. 8 of those could run for a week anyway.
Though instead of 12 volts. It would be 14.8 volts.
I just don't want to damage it as Tesoro is longer with us.
Man I wish someone would pick up that line.

 

[vlad]

I just recently bought a whites TDI sl and wanted to take it out while prospecting. Any ideas of what size coil would work better than others, or should I just stick with the stock 12 or 7.5 coil ? Is this a good Pulse machine to use ? Thanks for reading my post

Jimmy Sierra had a small loop that was getting a lot of good reviews.

 

[Nater]

I just bought the NF 14x9 evolution coil from Nugget finder.

How did that coil work out on the tdi sl? I am thinking about getting one. Was the coil to sensitive and giving signals all the time? thx!

 

[Odanscoils]

If he won't buiuld you one, I can, but not until winter closes down my prospecting, and farm and home chores.
Jim

Jim.
Is it possible to teach me how to build coils ?
I have most all the test equipment minus a spectrum analyzer. Now that I'm retired I have the time to experiment. I have a coil design I'd like to try.

 

[MattBullSummerville]

There’s some pretty good videos on you tube about coil building. PI mono coils are simpler to make than VLF and DDs. Coil housings can be had from a few sources. I’ve even watched videos on vacuum forming and considering try to make my own. Here’s a couple size charts I have come across.

 

[Jim in Idaho]

Jim.
Is it possible to teach me how to build coils ?
I have most all the test equipment minus a spectrum analyzer. Now that I'm retired I have the time to experiment. I have a coil design I'd like to try.

Actually, building mono coils for the TDI's is fairly easy. I don't recall offhand, but you can measure the inductance, and DC resistance of a factory coil, and match those characteristics with the coil you build. I built a 24" for mine, but rarely use it do it being too cumbersome, though it worked fine for larger relics. I just made a round form out of ABS plastic, and wound the wire on that, and glued up a mount. There are some steps that can be taken to improve performance, that I did not take, but the basic coil is easy. Somewhere on the forum I posted a pic of the connection at the box. Also, you have to research the wire size you need to balance the DC resistance with the inductance. Greater wire length, of a given size, increases resistance, and more turns increases inductance. You should, if you haven't yet, do a bit of research on inductance in coils, especially as it applies to various shapes. On a side note...one coil I made that did not work worth a hoot was a 9" x 18" elliptical. You can scratch that one from your list.....LOL
Another thing I did was make a round form for winding the coils out of a sheet of plywood, and wooden pegs. I drilled holes in the plywood for the pegs. I made some wooden washers, though plastic store-bought would have worked, to slip over the pegs to hold the wire above the plywood, so I could get string around the coil bundle, at each peg to make the coil a whole. Winding is easier if the pegs tilt outwards. The inductance, as I recall, didn't change much by shape. If you know the perimeter length of an elliptical you want, you can wind it as a circle, and then form it into the elliptical shape after.
Jim

 

[Odanscoils]

Actually, building mono coils for the TDI's is fairly easy. I don't recall offhand, but you can measure the inductance, and DC resistance of a factory coil, and match those characteristics with the coil you build. I built a 24" for mine, but rarely use it do it being too cumbersome, though it worked fine for larger relics. I just made a round form out of ABS plastic, and wound the wire on that, and glued up a mount. There are some steps that can be taken to improve performance, that I did not take, but the basic coil is easy. Somewhere on the forum I posted a pic of the connection at the box. Also, you have to research the wire size you need to balance the DC resistance with the inductance. Greater wire length, of a given size, increases resistance, and more turns increases inductance. You should, if you haven't yet, do a bit of research on inductance in coils, especially as it applies to various shapes. On a side note...one coil I made that did not work worth a hoot was a 9" x 18" elliptical. You can scratch that one from your list.....LOL
Another thing I did was make a round form for winding the coils out of a sheet of plywood, and wooden pegs. I drilled holes in the plywood for the pegs. I made some wooden washers, though plastic store-bought would have worked, to slip over the pegs to hold the wire above the plywood, so I could get string around the coil bundle, at each peg to make the coil a whole. Winding is easier if the pegs tilt outwards. The inductance, as I recall, didn't change much by shape. If you know the perimeter length of an elliptical you want, you can wind it as a circle, and then form it into the elliptical shape after.
Jim

Thanks Jim.
Where'd ya get those charts ?

 

[Jim in Idaho]

What charts?

 

[Odanscoils]

What charts?

Those images you posted.
Though I can't read all of it.
Anything on impadence ?

 

[Jim in Idaho]

To wind the coils, you need to balance the correct inductance and the correct DC resistance. To do that, you need to look up the wire size and resistance charts on the 'net. Then do a search on inductance, and that should get you to some formulas for inductance vs number of turns of wire. You need to know that first. Once you know how many turns of wire you need in your coil, to match the correct inductance, you can determine the total length of wire. Then figure how what wire size you need, for that length of wire to get the correct DC resistance. It's been awhile since I did any of this, so I don't remember where I found all that info, but the 'nets full of it. On the charts...those weren't posted by me.
Jim

 

[Nater]

Thanks Smego.
Yup that 24k is really interesting me
I'm also looking for a pi machine for retirement.
We all wanna see that rainbow sitting in that big oll pot of gold.
This new Tejon I picked up eats batteries..
8 of em at a time.
Actually a little surprised at thst.
My other Tesoro seems to run forever compared to it. The Tejon goes quite deep fo what it is.
I was just thinking about the 18650 battery change back. 8 of those could run for a week anyway.
Though instead of 12 volts. It would be 14.8 volts.
I just don't want to damage it as Tesoro is longer with us.
Man I wish someone would pick up that line.

I have a whites gmx sport 24k for sale, it’s the waterproof version of the 24k and it’s awesome. I only used it a couple times and I bought covers for the screen and battery pack so it’s nice. I’ve found gold with this detector the first time I used it. I bought a new PI otherwise I’d keep it. Let me know if you’re interested in buying it.

 

[Odanscoils]

I have a whites gmx sport 24k for sale, it’s the waterproof version of the 24k and it’s awesome. I only used it a couple times and I bought covers for the screen and battery pack so it’s nice. I’ve found gold with this detector the first time I used it. I bought a new PI otherwise I’d keep it. Let me know if you’re interested in buying it.

Send me a link ...

 

[Nater]

Send me a link ...

Whites GMX Sport 24k $725

Whites GMX Sport 24k metal detector. Waterproof, used only a few times in excellent condition, great gold detector and the last one made by whites. Comes with 6” concentric coil, battery tray, adapter for headphones, detector cover. $725 PM me or email: natehagon@gmail.com Or Call: 805-636-5950 a...

www.detectorprospector.com

 

[bobinyelm]

I know this is an OLD thread, albeit with a few recent posts, but I also recent acquired a Series 1 TDI but it came only with the Jimmy elliptic
Dual Field Mono Coil about 6X10.

I am looking for an optimal coil for small gold (1 gr up to 1gm) in mineralized Arizona desert washes where I'd like to be able to punch through moderate overburden (a few inches or so) to bedrock, or around the edges on dry wash boulders and into crevices in exposed bedrock

I understand the Sadie is the BEST for $230, but I can get a Razorback TDI Mono 81/2 X 11 for half the price, but I haven't seen that one tested anywhere. There's also a Whites Super Pulse 6 1.2 round coil for about the same price of Sadie.

Opinions?

Bob

 

[Jim in Idaho]

Get the Sadie. I like the 8 x 11 for general work, but the Sadie is more sensitive. If you can't afford a Sadie, and given that some people don't like the dual-field coils, in my testing the Whites 7 1/2" DF is a very near-equal to the Sadie on tiny gold.
Jim

 

[bobinyelm]

Get the Sadie. I like the 8 x 11 for general work, but the Sadie is more sensitive. If you can't afford a Sadie, and given that some people don't like the dual-field coils, in my testing the Whites 7 1/2" DF is a very near-equal to the Sadie on tiny gold.
Jim

Thanks, Jim.
Saw your post on the other Forum and realized it was you up this thread commenting on various coils.

I pulled the trigger on a Sadie 6X8 I found on ebay, and the 6X8 got very positive comments in a few posts. That size seemed about right for the small
washes I frequent, though I'm sure the 8X11 Sadie punches a bit deeper.

I paid $200 for the new coil (hadn't found a used one). They seem to be fairly obscure, and the seller had only one left for sale. I figure $200 (+tax/shipping)
is among the cheapest acquisitions I am likely to make in pursuit of my new 'hobby'/pastime in my new location (I was previously in WA State).

I may also borrow the Razorback 8.5 X 11 for comparison when the Sadie arrives, as if it's as good/better it can be had for $100 if I like it. I don't think I will ever be able to justify a used GPX5000 as practical purchase especially if the TDI suits my needs, but my understanding that the coils will also fit that machine, plus I can always resell what I don't want as there seems to be a market for coils. The way I see it, in places where the gold has been hit really hard, unless one has a darned decent detector capable of seeing better/deeper than most of the competition, one almost might as stay home, or face likely failure and frustration that would temper my enthusiasm.

As far as affordability, "It's only money," and as I told my detecting friend (mostly uses a Gold Bug 2) recently when he learned I'd bought the TDI, I told him that I've been a penurious type all my life, and at this point at age 75 I have a LOT more thousand dollar bills left than I do years left on the planet, so what the hell?

 

[Jim in Idaho]

Bobby, I'd say you've thought it out pretty good. I've been very conservative about money, all my life, too. And like you, I'm nearing 75 myself, so might as well live a little...LOL. I'm still not splurging on detectors, though. You'll like that Sadie. Hope you make some good finds, and will post when you do.
Jim

 

[autopilot42]

If you can buy and afford go ahead there is no looking back

 

[Michaeldoc2u]

Jim in Idaho, the use of higher voltage batteries is an area I am willing to explore. It may give the SL a bit more depth. Thanks to a local poster in Australia, XLOOX. I have blatantly copied his design for a higher powered battery holder using 4 x 18650 cells. Again full credit goes to him. When we explore the depth of the Tdi SL it is seems well established by users that 16 volts is both safe and highly sought after.
Just one image to show you where I'm at.. not finished yet, waiting for carbon fibre sheet etc. But everything fits and it works.. Dremel the guts out of a White's battery tray, use flat 18650 cells, the nipple ones don't fit. Keep the front connects and use a copper connection at the rear. Very tight fit with solid connections. A picture tells a thousand words.
All the best,
Karelian

I like my SL version a lot! From al the tests I've read, one of the top rated coils is the Nugget Finder Sadie 8 x 6. I use one myself. I also really like the Dualfield 12". I have a Miner John 5 x 9, and it works OK, but the Sadie is better. The Whites 7.5DF is just OK. I haven't found it to be any better, on small gold, than the 12"DF, and you lose some depth on bigger stuff. The Sadie is a pretty good compromise. I've also tested, and proved to myself, that the 4 cell 16.8v Li-ion battery pack gives a decent improvement on both depth and sensitivity. If you have the TDI, or Pro, you already have that pack. The SL comes with 12v pack.
Jim

Power upgrade is certainly very interesting, there is an increase in depth. I did a quick are test between the Orange pack with 3 x 18650 cells at 12.38 volts and the 4 x 18650 pack at 16.48 volts. Then compared them to the results with a Tdi Pro. TDI SL MAX gain, 10us, GB off. Tdi Pro had gain at 5. Gb Off, 10us.

12.38 volts give 6cm on a 1 grain ingot, 24cm on a half gram gold coin, 32 cm on a gold Half Sovereign, a US Quarter came in at 27cm.
16.48 volts give 8cm on a 1 grain ingot, 26cm on a half gram gold coin, 35cm on a gold Half Sovereign, a US Quarter came in at 30cm.
Tdi Pro gives 8cm on a 1 grain ingot, 27cm on a half gram gold coin, 36cm on a gold Half Sovereign, a US Quarter comae in at 33 cm.

So with 16.48 volts and at max gain, the SL is close to the Pro when is is on gain of 5.. in the air.. at least. I'll need to go out and play some more.

All the best,
Karelian

Will

I like my SL version a lot! From al the tests I've read, one of the top rated coils is the Nugget Finder Sadie 8 x 6. I use one myself. I also really like the Dualfield 12". I have a Miner John 5 x 9, and it works OK, but the Sadie is better. The Whites 7.5DF is just OK. I haven't found it to be any better, on small gold, than the 12"DF, and you lose some depth on bigger stuff. The Sadie is a pretty good compromise. I've also tested, and proved to myself, that the 4 cell 16.8v Li-ion battery pack gives a decent improvement on both depth and sensitivity. If you have the TDI, or Pro, you already have that pack. The SL comes with 12v pack.
Jim

Will a 6x8 sadie coil from a Minelab be compatible with the TDI SL. I have heard some Minelab coils are. Acquaintance tells me it’s for Minelab …? I will find out which one he was talking about.