coil confusion

[TomW]

Hello all!
I'm considering one of the new coiltek coils for xterra705. However there are so many variables Im not sure which frequency to get.
A little info about my area...I live in the Amador county area in northern CA. When I set up.the machine the ground balance is usually low around 14-20's. I like the idea of the 3khz coil. Im currently using the HF DD. I really don't hunt anything specific, just whatever I can find.
Any suggestions or questions that can help me decide on the proper coil?

 

[Old Longhair]

A little more information is necessary to be able to recommend a coil for you.

I assume that when you say you have an HF DD that you're referring to the 5x10" Gold Pack coil and not the 6", so going from there I need to know what it does not do that you need a different coil for?
Are you looking for more depth? Is metalic object density such that better separation is desired? Are you after something that hits harder on high conductors like brass, copper, and silver, but will be less accurate/stable on low conductors like gold, lead, and nickel? How accurate do you want the TID to be, or do you mostly listen for good tones? It may seen irrelevent (trust me it's not), but how far are you from the coast? Was there any minning in the area, and if so what for?

With answers to these sorts of questions we can point you in the right direction,

 

[Mtnmn]

A couple of things to consider: First off I imagine that you are interested in a low freq. (3 KHz.) coil because of wanting to find more silver. If not, then you should be considering a higher freq. coil. The problem with using low freq. coils is that they are not the best freq. coil to use in areas with higher levels of ground mineralization like what you apparently have (14-20's). Both Digger and Coiltek itself mention that fact in their write-ups on the 3 KHz. coils. Another thing to consider about the 15" Coiltek coil is how trashy or junk-ridden are the sites you hunt in? The 15" coils go so deep and cover so much area that they just don't do well in sites where there are too many targets under the coil at any one time. Minelab's 9" LF (3 KHz.) concentric coil hits hard on silver, but works best in mild ground, not the kind of mineralization that you have. As you know Coiltex also makes a small 6" DD LF coil (3 KHz.) and while the DD design works best in higher materialized ground and in high trash areas, you will not be able to cover much ground with it due to its small size and if you are going to be around water it is "not" waterproof. If you still have your heart set on acquiring a 3 KHz. coil for your 705, then it comes down to how much trash do you hunt in, if junky then without a doubt Coiltek's 6" DD coil would work best, if a low trash area then you might be able to get by with the 15" DD design as the DD's do better in higher levels of mineralization as compared to a concentric. Although under normal circumstances a higher freq. DD coil would probably give you better performance in your type of ground, its your call...

 

[Old Longhair]

The problem with using low freq. coils is that they are not the best freq. coil to use in areas with higher levels of ground mineralization like what you apparently have (14-20's).

This is a sticky area.
What I've personally noted is that the two types of mineralization both need to be considered. Where there are high levels of Magnetic minerals a higher frequency is a distinct benefit over a lower one. But, in areas where there is a lower level of Magnetic mineralization but a high level of Conductive minerals a LF will work just fine, even with lower overall GB numbers. This is why I asked about his proximity to the coast. Salt is highly Conductive, but has no Magnetic property. Inversly, where I am in iron country, we deal with more Magnetic minerals and have fewer Conductive mineral concerns.

That said, the LF coils are my favorite if not hunting gold, lead, pewter, and/or nickel. I do have some places that the LF simply doesn't do well, and at those sites the 7.5 DD is the coil of choice. Being primarily a coinshooter, my HF coils see the least use. The 15" is going to get a lot more action than the smaller HF offerings now though, because of it's size it looks enough deeper than the smaller ones, but I'll still avoid high iron trash sites when using it.

In the end, the 15" MF All Terrain might be the best choice, as it is the most honest and a "middle of the road" frequency, but it again boils down to what the user is expecting to gain from where they are.

 

[Mtnmn]

That is the problem I've run into when buying different frequency coils for the XT's, you never truly know how good a coil is going to perform in your area until you can actually try it out for yourself. The one coil that does perform very poorly in my area is the MF concentric, while the DD's seem to work just fine no matter what the frequency. Go figure...

 

[Old Longhair]

That is the problem I've run into when buying different frequency coils for the XT's, you never truly know how good a coil is going to perform in your area until you can actually try it out for yourself. The one coil that does perform very poorly in my area is the MF concentric, while the DD's seem to work just fine no matter what the frequency. Go figure...

Well....the reason for that is one that is largely a matter of search patter shape. The concentric coil is effected by all the ground's features over it's total volume of it's search pattern, which on a 9" coil is approximately 28

 

[TomW]

Hey all. Sorry for the delay in responding. A huge thanks for all the info you've sent my way. Now I'll try to answer some of the questions.
I do use the HF DD elliptical. It came with the detector. The soil here is magnetic. They use to do a lot of gold mining in this area. In fact this area is called the Motherlode. Hard rock mining has started again in one of the old mines here. At one time there were thousands of people here. They also left tons of trash ie: square nails, hinges, axe heads and other tools etc, etc. I would like more depth because people have been crawling around here with detectors for years. I like the idea of a.low.frequency coil because of all the silver coins. I've never found any gold~sigh~. We are a good.distance from the ocean. We are in the foothills of the sierras. You had mentioned TID stability. I've never had real stable numbers. They bounce around a lot. Unless they're close to the surface ie: 1-2"'s from the surface. Any deeper and they get a little jumpy.
I hope I've answered all the questions satisfactorily. Thanks again for taking the time to help me out.
Tom.

 

[Old Longhair]

Cool!
If sorting through trash is important, and silver/copper/brass/bronze is what you're after, then one of the two new Coiltek 3kHz coils might be just what the doctor ordered. The different frequency may not be of benefit over what you already have, but the difference in response to targets is huge. In dense iron trash areas the 6" "Digger" is great! I've been waiting for a trash sifter for quite a while, and they've finally given us one. It isn't good on lower conductors. As a matter of fact, anything below 36-38 is likely trash or tiny, and anything below 28-30 can't be trusted to be at all accurate unless it's rock steady, and even then it will be a higher TID than you're used to by a notch or two.

If the trash density isn't too high, and if you're looking for all of the depth you can get, then the 15" All-Terrain is it! Even here, where its glacial moraine south of the mines, I'd rather have a short shovel than just my Lesche digger. I've been using it places that have been pounded by everything up to and including CTX's and I don't find anything that isn't 8-10"deep or deeper......but I always find something.

As a side note:
Yesterday I took the Digger to my proving ground park. As I normally do, my hunt started at my van which was parked almost directly under the power lines at the road. After noise cancelling I GB'd @ 9. The threshold was stable with the sensitivity turned all the way up to 28, so I started swinging. I hit a few targets as I worked my way out into the park (and away from the powerlines), but about 20yds or so away from the powerlines I stopped and re-noise canceled and re-GB'd @ 32. I noticed that the machine had picked an entirely different noise cancel channel than it first had. I continued my hunt but periodiclly checked to see where the GB Tracking was, and it stayed in the 30-44 range the rest of the hunt.
My point is, that many things can effect GB numbers, and apparently not all are in the ground. If you experience low GB numbers, don't be afraid to re-cancel or re-GB from time to time at a site. it may suprise you.

 

[TomW]

Great responses! I wasn't considering the "Digger" until now. I think I'll start with that one and see how it goes. I think it will bring a lot more patience to my hunts as well. Also it is much more affordable. Shame its not waterproof but that's what silicone is for!
Thanks again for the guidance. People I talk to don't understand that this hobby can be complex.at times.
Regards all and HH!
Tom

 

[Old Longhair]

People I talk to don't understand that this hobby can be complex.at times.

To me, that's part of the beauty of this hobby.
A complete non-tecnical type newb can get started with a beep and dig, do pretty well, have fun, and may never see the need for anything else. And within the same hobby, a tech-head that wants to understand the science involved, can get a machine that's advanced enough to be a challenge to extrapolate all of the information it provides.

The e-book that Randy wrote is an excellent learning tool for the tech-head Xterra owner. It puts a lot of things into understandable perspective while being readable, unlike a boring textbook-like tech manual. The real-world examples, explanations, and illustrations tie everything together very well.