What accessory coils r there for Whites TDi?

[tvanwho]

I heard Whites has a 5 x 10 elliptical coil for TDi but cannot find any listings/prices for it on their website or any comments on the forums. I prefer an elliptical coil for gold nugget hunting,easier to maneuver around trees,rocks, and such and get into tight places. Will the Coiltek coils work as well, jjust wish they weren't so pricey and were waterproof?

-Tom

 

[Reg]

Hi Tom,

Jimmy Sierra has this elliptical coil made by Whites for him. Normally, any Whites dealer can get them, so you might check with your local dealer.

If no dealer is nearby, you might want to contact Jimmy Sierra Inc in CA. I didn't see the coil on their website, so a call will probably be the best way to find out much about it.

I just got one and it works very well.

Reg

 

[tvanwho]

And what size is it? Is it a DD coil or concentric? How do I pinpoint with it? Is mono the same thing as concentric? I get confused by all this techno mumbo jumbo. Are you located in Arizona per chance? I hope to be out that way this spring, would love to meet some local gold hunters to go out with?

-Tom,email me at tvanwho@yahoo.com

 

[Reg]

Hi Tom,

Here is a link to a pic of the coil. If I get a chance, I will take a better pic and post it later, but I need to get some sleep first since I am working nights and just got off. The elliptical coil called the Jimmy is a mono coil and the size is 9" by 5".

http://tdi.invisionplus.net/?mforum=tdi&showtopic=249

You might want to read some of the posts on the TDI tech forum since some of them do have pics of gold they have found with the TDI. Plus, this forum is primarily for the TDI.

Reg

 

[tvanwho]

I am hoping to be out there to visit my folks on the north side of Phoenix and gold hunt too, just don't want to be in there in early June again like in 2004 for my High school class reunion. Heck, they say its a DRY heat? It was hot as hell heat !! I went up in the mountains north of Pleasant Lake with a local guy in his 4x4 Dakota truck.We could barely stand to be detecting more than 10 minutes at a time and had to get back in to the AC in the truck to cool off and get our brews. Leaving at 6am in the morning didn't help much either. So, is it too hot in May as well? Just wondering where to draw the line on desert heat and exploring? Which fall months are good to detect, need to watch that monsoon season too? My niece and her new hubby made a trip to Phoenix and they got stalled out in a wash with 2 foot of water in Phoenix while driving a rental car. His first time in the state and not a good one.

-Tom

 

[Reg]

Hi Tom,

I will try to get the TDI coil pic posted tomorrow if possible. I got tied up today. Now, as for nugget hunting in AZ, I have hunted from late October through late March at different times and different years. It really gets too hot for me after late march or earlier than about mid October. So, I usually go in late Feb or early March in the spring and late October to mid November in the later months.

If I go early this year, it will be next month.

Reg

 

[tvanwho]

" Hi Tom. Yes we do make the JIMMY coil for the TDI. It is the same shell size as the 6x10 coil for the GMT. It is a Mono coil as DD coils are not recommended for the TDI. It retails for $249.95 Mike at Whites of the Great Lakes should carry it. He is the distributor for your area. You can reach him by using whites 800 number 547 6911 "

Reg,

Why is Jimmy saying that DD coils are not good for the TDi? I thought DD coils were the ones to have in HOT ground?
I see Steve H has the full line of Coiltek/TDI coils listed again on his website under Minelab Accessories. just not sure about the DD versions after what Jimmy told me?

-Thanks,

Tom,
ps, the Tonto NF in central Arizona says I can gold pan and metal detect and pick up mineral specimens over there BUT I cannot cause any surface disturbances or use a shovel and if I metal detect I must only look for recent coins.If I find a nugget, I have to leave it sit there? Whatever happened to the 1872 Mining law and the CF228 rules that they are sposed to abide by that do allow surface disturbances and hand tools for prospecting? I can't seem to get a reply out of them yet? In Prescott NF, you can use all the hand tools you want and dig and detect and keep mineral samples, but NO motorized gear ,just fill your holes afterwards.

 

[Reg]

Hi Tom,

DD coils work just fine on the TDI, However, it is believed that mono coils normally go deeper and, as such, are the preferred choice. Contrary to all the hype about how bad the ground is in AZ, the ground really isn't that bad in most places and I have hunted a lot of different areas across the state. Some of the worse ground is the red clay around Rich Hill and that can be hunted just fine with a mono coil so there is no major need for a DD.

Normally, the DD is used because the coil has some natural ground rejection capability and used in areas where the ground is really bad. So, the ground reaction is generally less when using a DD. Also, the DD isolates the transmit from the receive. Finally, the actual windings are smaller on a DD when compared to a typical mono with the same shell size. Since the windings are smaller, there is less potential depth capability, but is usually quieter because the smaller windings mean they are smaller noise antennas.

Keep in mind that our ground here in the US is no where near as bad as that in OZ and the GS 5 equipped with a mono coil works just fine in most places over there. So, if the detector will work with a mono in OZ, it will easily work with a mono here in the US. Now, since the GS 5 and the TDI are quite similar, then the TDI reacts basically the same with a mono or a DD.

The DD does have some advantages and one is the ability to detect smaller gold because of the heightened sensitivity across the overlap zone. So, a larger DD still works quite well when searching for small gold. Also, if a person fully understands the signals from a DD and how it relates, then one can use the fact that ferrous objects near the coil generate a different response.

Reg

 

[Reg]

Here are the three coils available for the TDI. From left to right, the 12" std coil, the 9" by 5" elliptical, and the 7 1/2" round coil. All are dual field.

Reg

 

[tvanwho]

" Hi Tom,

I called Jim at Whites of Calf. They do have them in stock ( 6 x 9 TDi coils-$249 retail ). They just didn't get around to putting them on the web site yet. You can get a hold of them by calling 1-800-457-0875 "

 

[crowbar]

Here are the three coils available for the TDI. From left to right, the 12" std coil, the 9" by 5" elliptical, and the 7 1/2" round coil. All are dual field.

Reg

Hi Reg, nice set of coils...What is the smallest gold nugget that can be detected with each coil and at what depth? Of course I'm asking to just place the nuggets on the ground. For test samples I suggest something around 0.05, 0.5 and 1.0 grams. My main interest is in the Jimmy Sierra "Jimmy Loop" search coil, but I'm sure there's people out there that would like to know what the TDI can do with each of the coils.

I'm not a big fan of the standard 12" round coil that comes with the TDI and think White's should have made it elliptical. I won't speak of a cover needed as this with an open spoke design just collects debris depending on the area being detected. Thanks, Reg.

whiskey

 

[Reg]

Hi whiskey,

Your question is really hard to answer because gold is such a variable and the adjustments on the detector can have a significant impact. One may detect a 1 grain nugget an inch or so depth wise that comes from from one location but struggle to detect a 3 or even a 5 grain nugget from another area. It all depends upon the gold characteristics and how you adjust the machine. I have detected 1 gram test nuggets buried in the ground at depths approaching 9" to 10" but more consistently in the 5" to 7" range, depending upon various factors. Now, a 3 grain nugget is .2 grams and a gram is about 15.4 grains so one can extrapolate other sizes if they only know one or the other means of measurement.

I have not tried to make a lot of comparisons between my SD and the TDI but what little I have, I find the TDI to be competitive on the 1 gram and smaller nuggets. I really haven't made and direct tests on larger ones because of lack of ML coils. It is hard to compare apples and prunes which is what one is doing when they try to compare two different detectors that don't have similar size and type coils.

As a general rule, the TDI will detect nuggets down to the 3 grain range (approximately .19 grams) consistently but could detect some even smaller given the right conditions. The depth will vary again because of the nugget itself. A relatively safe expected depth of detection could be an inch or two on the smaller size. Keep in mind there will be exceptions both ways. A perfect example is the testing of two "invisible nuggets" I have weighing over over a half gram or more each that can't be detected even when together by most PI's including the TDI without tweaking it.

The smallest nugget that can be detected is dependent upon the minimum delay setting, the noise level, the ground conditions, or more specifically the setting of the ground balance control and, of course, the nugget itself. If a person uses the single tone mode, there is a lower noise threshold which will generally allow the depth of detection to increase. Now, if the ground conditions are ideal and one can turn off the ground balance, that will also help with the depth capabilities.

Now, it is also difficult for me to give you more exact answers because my TDI has been tweaked by me so the minimum delay is less than normal. This helps with the detection of small gold but only at the expense of other factors.

Right now I have two of the coils put away but if I get time I will pull them out and try to run a little comparison. Personally, about the best I expect to see would be the smallest round coil do the best on the detection of smaller nuggets, then the elliptical and finally the largest coil. I don't expect to see much more than an inch or so difference under the right conditions on the smaller nuggets. On the real small stuff, delay is more of a critical factor in my opinion.

Sorry I can't be more specific at this time.

Reg

 

[goldbrick]

Hi Tom,

DD coils work just fine on the TDI, However, it is believed that mono coils normally go deeper and, as such, are the preferred choice. Contrary to all the hype about how bad the ground is in AZ, the ground really isn't that bad in most places and I have hunted a lot of different areas across the state. Some of the worse ground is the red clay around Rich Hill and that can be hunted just fine with a mono coil so there is no major need for a DD.

Normally, the DD is used because the coil has some natural ground rejection capability and used in areas where the ground is really bad. So, the ground reaction is generally less when using a DD. Also, the DD isolates the transmit from the receive. Finally, the actual windings are smaller on a DD when compared to a typical mono with the same shell size. Since the windings are smaller, there is less potential depth capability, but is usually quieter because the smaller windings mean they are smaller noise antennas.

Keep in mind that our ground here in the US is no where near as bad as that in OZ and the GS 5 equipped with a mono coil works just fine in most places over there. So, if the detector will work with a mono in OZ, it will easily work with a mono here in the US. Now, since the GS 5 and the TDI are quite similar, then the TDI reacts basically the same with a mono or a DD.

The DD does have some advantages and one is the ability to detect smaller gold because of the heightened sensitivity across the overlap zone. So, a larger DD still works quite well when searching for small gold. Also, if a person fully understands the signals from a DD and how it relates, then one can use the fact that ferrous objects near the coil generate a different response.

Reg

Hi Reg,
I must have missed your explanation of how to use a DD to discriminate ferrous targets near the coil more effectively. Could you please post a link?
Thanks,
Merton

 

[Reg]

Hi Tom,

Actually, I don't know where the link is where I discussed the DD coils. It isn't hard to determine though and it works best with round coils.

When a ferrous object is close to a DD type coil, the signals reverse, meaning, the signal will go negative when the object is close to the center of the coil, while a non ferrous object will cause a positive response. Unfortunately, this condition only exists for objects close, maybe 3" to 4" max.

This shows up in both an air test and when the object is buried, so one can run a quick test if similar size by different type coils are available.

Reg

 

[goldbrick]

Thanks for the info Reg, I will have to do some testing.
L8tr,
Merton

 

[Foxesgold]

Temperature wise April and early May isn't so bad if that is the only time you can go.

 

[tvanwho]

How is the weather in mid Feb in the Superstitions? We may be out there for the Phoenix gold show then.My TDi broke ,local guy was unable to fix, had to send her in to Mr White. Whatever you do, don't drop your TDi in the field while hunting like I did.It got real erratic after that and the tech thinks there is a short somewheres but could not find it. Would it help to wrap the control box in soft foam for field use? Kinda hard not to drop the detector in an emergency or by accident at times?

-Tom

 

[prospector 55]

Most of the coils for the Minelab PIs will work on the TDI!!! I just purchased an older 18in mono coil for a Minelab SD GP series PI and it fit my TDI and worked perfectly! there are alot of after market coils made for the Minelab PI units that will work very well with your TDI and they come in alot of different sizes ellipticles 6x9s monos and DDs and just about every size you can think of, the TDI is a very versitle machine, so if you are looking for coils you might want to check out the minelab units.
Rick

 

[au4greg]

Since the TDI is optimized using Mono Technology, the Wide Scans or DD coils can actually cot you some depth. Jimmy Sierra Loops are carried by most Local Jimmy Sierra-White's Dealers.

 

[Reg]

Hi Greg,

To be honest, I don't see that much of a depth loss when using a DD coil if you match transmit coil sizes. By this I mean that the DD coil is smaller than the same housing mono, but test against a mono winding close to that of the DD transmit winding and the two depths are quite close, especially when testing on the more typical smaller targets.

What is different is the width of the target signal, which can make the mono signals appear larger or stronger since the signal is there longer. DD's, on the other hand have a relatively narrow response zone plus any response on either side of the center line overlap is a signal that is normally opposite to that of the overlap area. This type of response works best with a nice slow sweep speed. So, if swept too fast, then the DD can appear to be worse than it really is.

The key reason the TDI and the GS 5 generally are equipped with mono coils is because the ground balance system works well over an extremely wide range of ground conditions. As such, there is generally little or no need to reduce the overall ground signal which does happen when using a DD type coil.

Generally, DD type coils are used to help reduce the ground signal, thus making it easier to separate weak targets from ground responses. Now, usually a DD is quieter, noise wise for a couple of reasons with the first being the windings are smaller, thus the antenna effect is less. The second reason is on the DD, the receive coil is not directly connected to the transmit circuitry, which reduces the overall noise level.

So, in many instances, a DD coil is or can be quieter. Because it is quieter, it is easier to hear the very weak signals better and this can help reduce any depth advantage a mono might have.

Reg