Gamma. Air testing 5 coils, results.

[capt.]

Since I have started detecting again I decided to test all of my coils tonight to get an idea of what is going on with each and how they compare across the board. The reason I wanted to do this was because of 2 tests I did at 2 different sites in the last 2 weeks. The first was at an old neighborhood that has been demolished to clear space for the Little Rock airport to expand. Ground was very wet. I can honestly say I have never seen or heard so much iron on the ground or feedback through the headphones. Non stop noise with every swing. I picked a spot about 50 feet away and methodically worked my way there and back, trying to get a digable signal. Lots of falsing on the iron, a couple convincing enough to dig. No good targets came up. This was with the new Nel Sharpshooter coil. I switched to the stock 8 inch concentric and did the same thing in the same place, and dug one target. A 1972 lincoln cent. I later found a quarter about 80 away but this area was not as bad as the original test area. The second was in a park in Pine Bluff that at one time years ago had an amusement park type thing going on. I chose an area that has a good bit of iron and did another test. Ground was wet. Starting with the Nel sharpshooter again, I picked a tree about 75 feet away an again methodically worked there and back looking for digable signals. 3 bullets and 2 flattened screwcaps that passed the coil lift and front and back of coil swing test. Swapped to the stock 8 inch concentric and reworked the exact same area. I dug a copper penny, a quarter and a couple of bent pull tabs that hit consistently at 57. Since the stock coil seemed to be hitting on targets that for whatever reason the DD coil was missing, I wanted to see what they would do in side by side air test which led to testing all the coils.

I stopped at the depth that gave me a digable signal, repeatable both ways swinging across the bottom of each coil. I know this is not the same as in the ground. This was done to help ME learn more about my detector and each coil and since I have the info I figured I would share it here as there is not much out in internet land on the Gamma. I was surprised by these results.

Sensitivity was at 94 and disc at 10.

Stock 8 inch concentric coil
quarter - 10"
nickel - 9"
dime - 8"
copper penny - 8 1/4
gold wedding band - 10"

11" DD coil
quarter - 11"
nickel - 10"
dime - 10"
c penny - 10 1/4
wedding band - 11"

Nel Sharpshooter
quarter - 9.5"
nickel - 9.5"
dime - 8"
c penny - 8 1/4"
wedding band - 8.5"

Nel Tornado ... Sens down to 92 to quiet it down. This admittedly takes away from the performance but it was necessary to do the test.
quarter - 10"
nickel - 9"
dime - 8 3/4"
c penny - 8.5"
wedding band - 9"

5" DD coil
quarter - 8"
nickel - 7.5"
dime - 6.5"
c penny - 6 3/4"
wedding band - 7 1/4"

capt.

 

[Monte]

I have evaluated search coils since I started in this great hobby, and while I DO have some Double-D coils, and while I DO know that at times there might be a slight advantages to using them, my personal preference in search coil design is a Concentric. They work, work well, and don't have some of the operational glitches that we can associate with many Double-D designs.

I like the stock elliptical Concentric on the Omega, but after working it side-by-side with an 8", I favored the 8" coils benefits and the 8" Concentric is my main-use coil on the Omega. In trashier places the 5" Double-D comes in as my 2nd favorite coil. The only other Teknetics coil I like with the Omega is the 5X10 DD because it works okay and it is a solid-bottom coil so it doesn't hang-up in the short stiff brush I confront in many old homesteads and town sites.

For whatever reasons we might consider detector makers and detector users use to make search coil decisions, I still think the big deal 'trend' we have seen that past several years for Double-D coils is mostly based on hype, folks quoting suspected advantages we used to hear for coils used on older-technology detectors, and marketing. It like everyone thinks you HAVE to have a higher frequency detector to hunt gold nuggets, and MUST use a Double-D coil. In the late '70s and through the '80s we had a big surge in "Electronic Prospecting" when more people found how efficient a metal detector could be to find raw gold.

The focal point at the time was talking about Australia because it was a really big boom down there. They had vast areas of land without a lot of available water to use conventional methods for dredging, sluicing, high-banking or just panning, yet some very impressive amounts of gold. Gold in ample size to cause a detector to respond, and it meant having a detector that could work well and handle high ground mineral conditions, but also a detector operator who knew how to handle the detectors they used.

Even though it was based on the huge growth of electronic prospecting in that era when we learned of different search coil designs or operating frequencies that provided a little better in-the-field performance for seeking the usually tiny hunks of gold, it didn't obsolete popular detectors we were using for other hunting applications. Can you imagine making a decision to close your metal detecting shop in the USA and move to Australia with the intent of exclusively searching for native gold, family and all, with the plan to make enough to live and support that family? Plans to get ahead in life and be successful when it came to finding gold with a metal detector?

Well, if you knew metal detectors and metal detecting then you certainly had an 'edge' over the newcomer, so that would be in your favor. But can you imagine a fellow making such a commitment and investment of both time and effort and the capital to finance such an adventure making it down to a foreign country and ready to do his part using a VLF/TR-Disc. detector, naturally used in the VLF Ground Balance All Metal search mode? And imagine the detector he was using had the 'standard' type search coil and not a newfangled DD design, and it operated at 6.592 kHz and not a higher frequency like we have come to presume you need? You would not think that to be a smart decision, but that's what he used most of the time, and he hunted raw gold for ten years and, in the end was successful, to be sure.

I have done some gold nugget hunting through the years but haven't had the greatest success, partly because I wasn't always in the best locations, and partly because I had other work commitments and couldn't devote the time. I have found gold nuggets, most of which have been smaller, and I have hunted gold nuggets with detectors ranging in operating frequency from 6.59 kHz to 20 kHz, and used both round and elliptically shaped search coils, both of both Concentric and Double-D design.

My two biggest gold nuggets detected were a 5 dwt and 8 dwt, and that was when I was in California and using a 13.77 kHz detector with a round 8" Concentric search coil. Matter of fact, the majority of the gold nuggets I have found came when using a round Concentric search coil that was 6" to 7" in diameter.

Just looking at the photo you added to the post made me also think of not just the dollar investment in those two different shaped after-market DD coils, but the weight and balance, especially under poor health conditions. I appreciated the light weight design of my Omega over my other detectors back in September of 2010 when I was recuperating from a fall off a ladder. That happened in late June and left me with a severe concussion, fractured skull, ruptured ear drum, two cracked vertebrae in the neck, and the fall to a cement floor that broke ribs 5,6,7 and 8 on the right side.

I was in a neck brace for a little over a month, and with my age and crummy health anyway I was slow to mend, especially those blasted ribs. I have a bad back anyway so the fall didn't help anything out there, either. By the end of August I was able to move about, gingerly, and thought a little detecting might be a good way to get some moving and exercise for my mending back, but my XLT w/6½" or 8" coil, or MXT Pro w/6½" or 950 coil, or IDX Pro w/6½" coil, just didn't feel comfortable enough to last long. I wanted some visual info to help limit some over-effort to go after trash so my Bandido II µMAX w/7" coil was not a good pick.

My Omega was light and balanced well enough, but even with the 8" or elliptical Concentric coils, I still was bothered with too much pain in the back, as well as shoulder and neck. The only solution was to reduce the weight on the far end of the rod, so I mounted up my 5" DD on its own lower rod, and that felt workable. So outfitted on August 30th, I took on the task of using the Omega and 5" DD coil exclusively for the entire month of September. I hunted all the typical places I would go, plus some renovation work I encountered, and took a 3-day detecting journey with a couple of friends.

They used an Explorer II w/10"+ DD and Classic ID w/8", and she used her XLT w/8" and Classic ID w/6½". We searched a variety of sites to include big open grassy parks and grassy school grounds. The three of us compared our coin recoveries over that 3-day jaunt and we all had almost the same amounts. My totals put me in the middle, but between the two of them was only a difference of about twelve coins after three days .... and all I used was that 5" DD coil and my Omega. I tallied 895 coins for that month of September, and quite a few of them were much deeper than most average hobbyists might think a smaller-size coil can find stuff. Many were in the 5" to even 6" depth range.

So, I really appreciate your post and results of side-by-side comparisons. Yes, they were an 'air test' but that still kept everything fair. I mainly use Concentric coils, but I do have some DD coils, like the 5" for the Omega, but one thing I do NOT have, and that is any after-market search coil in my arsenal. I have had them to evaluate, and picked one or two up on trade, but I have never purchased an after-market search coil because what we have from the detector makers seems to work just fine for me.

I appreciated you post, and sorry to ramble.

Monte

 

[capt.]

Thank you very much for "rambling" Monte. I didn't write it in my original post BUT having read your posts extensively over the years and knowing that your coils of choice is the concentric is what led me to perform the tests at the sites in the first place. I knew you had your reasons and developed them after years of real world detecting. I had never really used the stock coil, and to see first hand the way it worked in that iron really surprised me and the air test was equally surprising. I still have a lot to learn but that is what keeps it interesting. Thanks for responding!

Capt.

 

[MarkCZ]

Here is a little test for you to try.
Take a coin (any coin) and arrange it so that is tilted somewhat, not totally edged but angled and run it by your coils and see if one coil or the other holds up any better.

Mark

 

[Pepa]

Capt., you said that "you stopped at a depth that gave you a dig able signal, repeatable both ways." Was that a digital and audio read out, or audible only signal? thanks..

 

[capt.]

Audible only. I wasn't looking at the face of the detector when doing this.

capt.

 

[capt.]

Sorry Mark, that is not possible now. I have liquidated my assets somewhat and am now down to 3.

capt.