Best 5x10 coil for TDI SL?

[goldchaser3]

Has anyone done a direct comparison between the 5x10 DF Jimmy coil and the 5x10 Mono Razerback coil? (Not the folded 8 RB).
I have the 7.5DF but looking to add a narrower elliptical for my TDI SL for prospecting in the California Gold Country and don't know which one to get. I've heard that White's (Jimmy Sierra) may be better quality and/or "tuned" (whatever that means) to the machine, but I also own one RB coil (10x14 Mono) which goes very deep and is very light and has worked great for me. All comments appreciated. Thank you!!!

 

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[Hard Prospector]

The Jimmy Sierra TDI specialty coils are no longer being made. The Whites engineer who was making them as part of Jimmy Sierra products became suddenly ill and passed away recently. The man was an electrical genius and built great coils with rugged durability,quality and attention to detail. The DF 7.5 and 12" Whites coils that come with the machine are good but the Jimmy Sierra TDI specialty coils(4x6, 6x10 and 8x14) take the machine to another level as far as locating gold. I used the TDI 8x14"Digger" Mono and the Sierra 6x10 DF Mono this winter in the desert swinging for 100"s of hours and they produced very well. When I called Jimmy Sierra Products several months ago to order extra loops is when I heard about what had happened and that Whites is still undecided on which TDI specialty coils it may pick up for production. That's when I heard stock was limited and bought all that I need to make sure I had spares of all sizes. Interestingly, the TDI 4x6 "Mini Jimmy" shooter coil was never advertised and it has found the tiniest pieces of gold every bit as good as my GMT. I only know of one guy who uses the 5x10 Razorback on his TDI and said it works well, also heard on this forum that Razorback is under new ownership.

 

[goldchaser3]

Thank you for the info, Hard Prospector! Could you please tell me when and how you decided to use the 8x14 Digger vs. the 6x10 Jimmy? And what was your experience regarding their depth? Obviously the 6x10 will pick up smaller nuggets, and the 8x14 is bigger and heavier but should be able to pick up larger and deeper gold. Since both are oval and somewhat close in their width, I was wondering what percentage of time did you find that the tip of the 8x14 tip was really too big to go where the 6x10 would go. I already have a Digger coil and don't want to spend needlessly.
Thanks so much for your knowledge and advice!

 

[Hard Prospector]

If the terrain is mostly flat or rolling hills, I most always start with the 8x14 coil and have found very small gold with it too. But as you know the width makes it tough to use the tip as a pin pointer and in steep rocky ground keeping the coil parallel with the ground(false tones) becomes an issue. That's when I get out the 6x10 or 4x6 coils which are easier to work in such areas. Sometimes when I've gone through an area where I found gold with the 8x14, I will go through it again with the smaller coils and usually find more smaller stuff. Something else I've noticed is that I can usually run the gain very high to maxed with the smaller TDI coils no matter how nasty the soil is. To make switching out quicker, I carry all 3 of these TDI coil sizes pre-mounted so that all I have to do is change out the lower rod and reconnect the power. The rod cost isn't bad and makes it quick not having to mess with that nylon nut/bolt or much cord wrap. I would have to say that adding a 6x10 coil would be well worth the money in what it could do for you. Hope this helps...Rob

 

[63bkpkr]

HP & G3, interesting thread and information. Which version of the TDI do each of you prefer and Why? Do not own one but I am curious about them. Thank you.....................63bkpkr

 

[Hard Prospector]

HP & G3, interesting thread and information. Which version of the TDI do each of you prefer and Why? Do not own one but I am curious about them. Thank you.....................63bkpkr

I needed a PI machine but it had to be able to run on disposable batteries. Most PI machines use these large, powerful, rechargable battery packs( which helps give them their extreme depth capability.) The TDI SL uses the same battery tray( 8 AA alkaline) as the GMT. The SL is also the newest of the TDI series, lightest, has a very stable threshhold even at high gain and isn't difficult to ground balance. It has worked very well for me especially with the TDI specialty coils. Oh, I almost forgot, its been dropped several times when I slipped on rock or ice and has survived fully functional.

 

[goldchaser3]

Hi 63bkpkr, I had a TDI Pro but the constant warbling of the threshold was driving me crazy. I had to lower the gain to around 5-6 here in the northern CA gold country in order to get a semi-level threshold. When the TDI SL came out I took my TDI Pro to my local White's dealer, Greg at Golden State Metal Detectors, and we went to a local park and tried out the two detectors and a couple coils on real buried junk in the park. The TDI Pro could signal targets about 1/2-1 inch deeper, HOWEVER, that's when we knew there was a target there and knew to listen for it. (like most of the videos posted - and always passing the center of the coil over the target, too) If you are out in the field a very faint target could easily sound like just one of the warbles, on the TDI Pro. So knowing that I could run the TDI SL on max gain combined with the silky smooth threshold I determined that in the real world when you don't know where the targets are, I could hear targets equally deep with the TDI SL as the TDI Pro. And the smooth threshold meant that I could prospect for a long time without all the noise fatigue. The TDI Pro would wear me out - that's because you have to focus extremely intently to hear a target through all the warbling, and that is tiring.
Now add in that it is much lighter and I can use extremely cheap AA's as back-ups, and it was a very clear choice for me.
That was my experience. Hope this helps.

So Hard Prospector has convinced me I need a 6x10 - so my question still remains - hoping to find someone who has tried and compared both brands.....

 

[63bkpkr]

HP - who has not fallen with the detector in hand! I'm surprised my box is still rectangular and the 'S' rod is not a double 'SS'.

G3 - so you are in the Bay Area or close enough to drive in and visit with Greg?

And thank you both for your inputs as they are quite helpful!

Today I've been checking out my backpacking/prospecting equipment, fixing a few items and sorting the gear to see what to leave behind IF I get to go out in late August. I'm finding it rejuvenating and just seeing some of the pieces brings back memories of days spent hiking/digging/panning/detecting and such endeavors. Very similar to discussing various types of detectors, just in case I need the information. Good stuff!...................63bkpkr

 

[goldchaser3]

OK, I buried a 4 gm nugget in my backyard and re-tested my 7.5DF, 10x14 RB and Digger coils. I already knew the 10x14 would be the deepest detecting, so that was not a surprise.
The 7.5 and Digger were close, but here's the part that helped me make up my mind on which 6x10 to buy..... At depth, the Digger coil's responses were a little broken up - kind of like on a cell phone. Hard to describe but I hope you can get the idea. They were also lower in volume. Since I knew that the Jimmy and the Digger were made by the same people(s), I made my decision to buy the RB 6x10. Being a single mono vs. DF I am expecting it to go deeper than the Jimmy regardless, plus with the above results I think the RB coil is my best bet. I have confidence in Miner John, the new owner.
63bkpkr, I'm in the north Bay.

 

[Hard Prospector]

Interesting results, thanks for sharing and good luck with your new coil. You should try to have some beers with 63bkpkr, that guy has got to have some great stories.

 

[Reg]

By design, the dual field (DF) coil should not go quite as deep on larger gold. However, on smaller gold, less than 1/8 oz the DF should begin to do better. Your 4 gram nugget is about the crossover size. Keep in mind that a 4 gram nugget is about 62 grains and a lot if not most of the nuggets found are much smaller than this size.

Keep in mind the basic design was to provide the depth of a mono coil but enhance the signal strength on smaller more common gold, thus the DF design worked for large gold while making it easier to detect the smaller gold also.

BTW, one can hunt for smaller gold with a DD coil but you have to sweep slower for the best results. Tests performed by AZO indicated the DD coil did a little better on smaller gold in the few grain size, but the coil didn't go quite as deep on larger gold when compared to a similar size mono. A DD coil can be a little quieter because the transmit is isolated from the receive plus the receive coil is a little smaller than a similar size diameter wise mono coil.

As mentioned, the DF coil was designed by a White's engineer named Dan Geyer. I was truly saddened to hear that he passed away. Dan was a great guy and a brilliant engineer who loved nugget hunting. I was fortunate enough to have met him a few years ago and I can honestly say, I enjoyed my talks with him.

On a different note, the SL does operate on AA batteries, but can run on LI Ion rechargeable types also. RNB makes a Li Ion battery pack that works very well.

My recommendation is to change the AA batteries well before the warning light comes on. As they diminish in voltage, the detector will begin to lose depth and can become a little noisier. Fortunately, or unfortunately, the noise reducing design makes it difficult to hear the noise increase. In any case, as the noise increases, the depth is lost. This depth loss isn't much but it is there and any depth loss when hunting gold can be detrimental.

My recommendation is to use the high/low conductivity switch and hunt initially in the low conductor mode. Most gold found will be found in this mode. Also, depending upon the gold purity, even a lot of the larger gold will be detected in this mode. Very pure gold will cross over from the low conductor to the high conductor mode at somewhere around a 1/4 oz size. Less pure gold may never cross over even in the oz + size range.

On another different note, I have to thank two people, Steve Hershback and George Baker for giving me the idea which caused me to develop the conductivity switch idea. I installed it on a GS 5 prior to the TDI's existence. Fortunately, White's elected to add that feature to the TDI. I also have to thank Steve for his information about the gold conductivity in Alaska. From what he mentioned, I conducted several tests plus searched for technical information on what happens to gold and how its conductivity changes as the purity changes.

There used to be a website that displayed how the conductivity gold changes from a very high conductor to a very low conductor simply be changing the purity of the gold by adding something as common as silver and/or copper to the gold. Since this commonly happens in nature, a gold nugget can respond as a high conductor, much like aluminum to a very low conductor similar to lead. This is why it is important to know more about the gold in the area one is hunting. In simple terms, knowing more about the gold nature can mean in some areas one only needs to hunt in the low conductor mode and not miss any gold, but be able to ignore most iron junk. In areas where the gold is pure, then one will have to use the all mode or detect an area using the low conductor mode and then go over the area in the high conductor or all mode.

Why use the low or high conductor mode and not the all mode? Simple, to reduce the noise level on the TDI and the SL for that matter. Also, a person can search an area again in the all mode or the high conductor mode if they are worried about missing anything.

As for the coil question as to which is best, the answer lies in what a person expects to find in terms of size of gold. A DF does better on the smaller gold down in the few grain size. A foldback design does well also if the coil is built properly. Basically, the foldback design gives you the depth of a similar size mono plus enhanced response to small gold when under the fold back area.

BTW, for those interested, the foldback design is something I developed shortly after the DF coil was introduced as an alternative to the DF. Reference to this foldback design can be found on the Geotech 1 forum for those interested. Since the DF was patented, any duplication by anyone selling coils would be infringing on the patent. The foldback is a totally different design, but does have a similar ability to detect smaller gold.

Here is the link to my DF idea. Just go down to my post and open the pic to see the basic design.

http://www.geotech1.com/forums/showthread.php?15585-Coax-for-duel-field-coil&highlight=dual+field

Again for those interested, Jason elected to build the foldback design and he referenced where he got the idea way back when he mentioned on his forum he was going to build coils.

One last note, I have a couple of new ideas are in the works including a different coil idea. Actually, the coil is only different to a PI. If wired a little differently, special low noise parts can be used, thus reducing the noise even on the TDI. Add this feature to a simple mod or two to add the noise reducing design and the TDI becomes a different detector. All of this takes time so don't look for it right away.

Reg

 

[Hard Prospector]

Great stuff Reg, man I was hoping one of the experienced gold detecting "All-Stars" of this forum would take an interest in this thread. It has always been in the back of my mind that by the time the low power warning light came on, machine performance had already began to suffer. To mitigate this issue, I bought a couple of portable battery charge indicator gauges(Radio Shack) and they work well. I check each AA battery before I load it into the clam shell and I recheck after every two hours of swinging. If anyone of the 8 is so much as "creeping out of the green" I slide in a fresh battery pack and swing on (I carry four). In my garage I have a shoe box full of "slightly used" AA batteries for TV/video remotes, kids toys and other less important crap.

 

[Reg]

The SL battery light is specifically designed for Ni Mh types but does work on Alkalines also. By the time the alkaline batteries get down to 8.5V they are fairly well shot. The battery light comes on at 8.5v or so.

The SL draws about 500 ma or so and at that rate, the battery life for quality Alkalines is less than 3 hours before it becomes quite obvious something is changing. The battery light should come on at about 3 to 3 1/2 hours actual run time. This calculation is based upon the information on the Energizer's site for AA Alkaline batteries. Ni Mh types should be in the same run time depending upon the quality of the batteries.

The 2900mah RNB Li Ion batteries will maintain over 11V for a run time of 4 1/2 to closer to 5 hours before the battery should be changed for best results. Now, I suspect a person could run to maybe between 5 1/2 hours and 6 hours continuous run time before the light comes on or the battery shuts down. RNB uses quality Panasonic Li Ion types and their specs indicate they should hold up to very close to their rated output, thus 2900 ma at a 500 ma rate indicates close to 6 hours before the battery is exhausted and needs to be charged.

Personally, I don't recommend running any battery to the extreme limits, but people often do. Once a battery gets low enough the internal resistance of the battery can influence the detector and how well it works. When coin hunting, this isn't nearly as important as it is when gold hunting, where gold targets are rare to begin with.


Reg

 

[goldchaser3]

I received my new 5x10 mono Razorback coil today, and after a quick 20 minute test in my backyard have to report that I am very disappointed. First of all, it is not as sensitive as the 7.5 DF from White's. And I don't mean on very small items, which one would expect due to the smaller inner coil on the DF. It was about 1" less depth on both my 4 gram buried gold nugget and a nickel. Even though I was expecting it to be deeper, if it was as least equivalent I would have been ok since I was mainly looking for the narrow shape to help around all the rocks in the Gold Country here in northern California. And that was the small issue. The big issue was the falsing. I first noticed it when I was trying to wave it over my gold nugget - loud random signals every time I passed it over the ground. After some experimenting it was obvious that it was the cable. Even small wiggles of the cable near the coil caused loud falsing (I hope I am using that term correctly) sounds. I have sent MinerJohn an email and look forward to his response. I will probably opt for the 8-1/2x11 since I definitely do not want to give up so much depth, but if the cable issue isn't fixed this is a no-go.

 

[Hard Prospector]

It sounds like a manufacturing quality control issue, man that sucks because having confidence in your machine is so key. I have three TDI 4x6 Mini Jimmy mono loops(I think I bought the last 3 they had) and I could sell you one if it might help. I would suggest calling Whites and ask Jimmy for his input, that guy knows the TDI and he could suggest loop options. BTW, Oregon Bob recently bought the TDI 4x6 Mini and you could PM him for his impression on it. Good Luck...Rob

 

[goldchaser3]

I just heard from MinerJohn. He's going to replace it with an 8-1/2x11 for free. I'll update this once I receive that one and can test it.

 

[Reg]

There are different types of cable that can be used for coils. What usually is the big difference is the shielding type and one of the best is something called served shield. The more conventional shielding is more of a X or cross shielding that is often detectable while the served shielding is much finer wire wound around the inner core. Generally, this served shielding isn't detected by most PI's.

It sounds like the coil you have uses the X type shielding. If this is the case, then the cable should be run straight up the lower shaft at least a ways and be relatively snug near the coil to avoid detection. If you haven't sent the coil back, you may try this setup to see if the falsing is minimized.

I am puzzled by the depth difference. I would expect the 5 by 10" coil to be competitive with the 7 1/2" Whites DF coil. I wind my own coils and mine are quite competitive depth wise.

Reg

PS: Building coils for the TDI isn't that difficult and if they have the proper turns and good shielding then all that are relatively the same in size should have equal depth. Now, because noise can have a major impact, any comparison of coils should be done away from any noise sources if possible or at least done almost immediately in succession and not done on different days to avoid wide noise variations.

How much can noise influence a coil test? Well, I have tested the same coil with a nickel as a test target on different days and had as much as a 2" to 3" difference in air test.

 

[Hard Prospector]

Reg, you and a few others in this forum could make a bundle writing books on this stuff.

 

[goldchaser3]

Yes! 99% of what I know I learned from Reg! He's the best.
I've already shipped the coil back, but here's a very poor video of me trying to replicate the issue:

 

[Reg]

The TDI SL has a little trick built in that makes it a little more sensitive to small gold. Unfortunately, this same trick also makes the detector a little more sensitive to the coil design which includes the ability to detect the coil wire shielding.

You might try advancing the delay a little if you have a coil that appears a little too sensitive to the coil lead. Usually, an advancement of a microsecond or two is sufficient. Relic hunters will not notice any difference in performance, but gold hunters will notice a slight sensitivity decrease mainly to the smallest gold, down in the grain or two range.

Keep in mind that most 1 and 2 grain nuggets may not be detected to begin with, but there are some because of the chemistry of the gold and the size (thickness), some are.

This small gold detection thing is far more complicated than people realize. In fact, I have a couple of nuggets loaned to me by John Blennert that weigh about 8 grains that are not detectable by most PI's. The reason they can't be detected is because of their physical characteristics.

Reg