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About the new 15" coil.....

Posted by BuckeyeBrad 
About the new 15" coil.....
April 21, 2011 02:53AM
Late last week Mike Scott called me about several things and since he was going to continue to be tied up at trade shows for awhile, he offered to send me his personal new 15” DD Fisher coil to check out. I obviously and graciously accepted. Unfortunately, I’ve had pretty much nothing but bad weather here since but I have done some air testing and a very short field hunt. I need to get it out in the field more before I mention anything about my observations about the in field performance but I can at least share what I’ve seen with the air tests. Actually, I updated Mike earlier today and asked if he wanted me to wait until I sent him my written opinion on the coil or if he minded if I started to mention some of the details online before that. His reply was “Your call on what you want to do”. I specifically mention this because some folks have the suspicion that these initial tests are always scripted and or at least approved by The Company. I hope all can see that this is not the case. Once again, FT has a good grip on what they have with this coil and they’re willing to let the chips fall. Along the same lines, I am obligated to send this coil back to him so it’s not “a freebie” for me, as if that would influence my thoughts or something. NOT!

Before I get into any of the numbers, I want to mention some boiler plate info and general initial usage opinions on the coil. As has already been mentioned, it is physically huge and definitely heavier than the stock 11” DD BUT it can be managed as mentioned below. It comes supplied with one rubber spacer washer and that needs to be used to secure the coil and help keep it in place when the mounting bolt is tightened. There is no floppiness felt or perceived. I’ve used large coils from other companies and that is not always the case. Keep in mind that this is a new mold and it bears no resemblance to the stock coil. It is build very solid with much thicker members for its support legs and mounting tabs. The following may be “old hat” to those that have used large coils previously but for those that haven’t, I’ll mention a few more suggestions. When using this coil, you’ll expend the least amount of effort if you do two things. Adjust the overall length in order to position the coil as close to your toes as possible and if you can, given the terrain, let the ground do some of the work by partially resting the coil on the ground as you swing it. Since you will be running the coil closer to your feet and the fact that this coil definitely has a larger field, you should definitely consider not using shoes that have any metallic eyelets.

For the air testing I used my F-75 LTD and for simplicity and in an attempt to get as much apples to apples as possible, I only used BP, both in discriminate and all metal. Rather than try to run it hot in order to see “what it could really do”, I wanted to run both coils at whatever settings were necessary to get totally stable performance. I have a ton of RF at my location but by doing whatever it takes to run stable, at least in my opinion, it makes the results more meaningful and hopefully folks will agree that it can only get better. Additional setup detail was discrimination at 5, and sensitivity at 25. In all metal, I could run the sensitivity at 45. Before I started, I assumed that the large coil would probably not be able to run as hot as the stocker, but I was surprised to see that was not the case. In fact, the 15”er could be run about 10 points hotter in all metal but when I discovered that, I decided to run the big coil to the lowest common denominator, that being the sensitivity required by the stock coil. I also initially varied GB settings but depth was only minimally affected from one extreme to the other so I just settled on 70.

I checked 4 targets of each common category, relics, coins, and jewelry. For relic targets I used 62, 50, and 32 cal round balls as well as a ½” diameter flat button. For coins I used a quarter, dime, penny, and a silver three cent piece. For jewelry I used a medium gauge and sized men’s gold ring, another men’s gold ring about the same size but much lighter gauge, a very small toddler’s gold ring, and a hollow linked gold bracelet.

Rather than rattle off all the results, I’ll just mention one example from each category. For example, the flat button using the stock coil at the previously mentioned settings hit at 13.5” in disc and 15” in all metal while with the 15” coil did better with 16.5” and 19” respectively. With the 3 center, and in the same order, depths were 10.5”, 11.5”, 12.5” and 14”. Keep in mind that is 14” on a quite small coin and at greatly reduced sensitivity setting!! The largest gauge gold ring yielded 12”, 14.5”, 14.5” and 17”.

All other comparative results were pretty similar across the board, so this new coil definitely isn’t target size dependent like a lot of other larger than stock ones are. It also offers definite, and if I may so bold as to say, significant increases in depth across the board and not just improved coverage. From what I’ve seen so far and comparing the performance this coil to all the other large coils I’ve used in the past, I’ll definitely be getting one of my own!!
Re: About the new 15" coil.....
April 21, 2011 06:13AM
Brad, thanks for the preliminary write-up.smiling smiley


Can they do something about the color.............let's say..........Black.
Re: About the new 15" coil.....
April 21, 2011 06:18AM
Thanks for the review, it sounds promising. Now, if only mine would get her in time for my next day off.
Re: About the new 15" coil.....
April 21, 2011 08:50AM
Thanks for the review! Looking forward to more field tests!
Re: About the new 15" coil.....
April 21, 2011 11:33AM
Thanks Brad , your air test seem close to some T2 tests i read a few weeks ago.
2 inches on small targets with bigger gains on larger targets.
If the big coil can hold that edge in the dirt it will be well worth it.
Re: About the new 15" coil.....
April 21, 2011 12:22PM
Dirt results will be (somewhat) different...........as to be expected.
Great report, Brad!
April 21, 2011 05:04PM
You are very good at testing and being impartial. Thanks for all your effort.

Scully
Coil color was discussed early on
April 21, 2011 05:08PM
And Fisher engineers felt that a black coil would absorb unwanted sunlight heat. I also asked why the mounting ears were not in the center, as opposed to offset, and was told they tested that as well. Putting them in center did not imporove balance any.

I cant wait to try these new coils.

Scully
Re: Coil color was discussed early on
April 21, 2011 06:27PM
Scully Wrote:
-------------------------------------------------------
> And Fisher engineers felt that a black coil would
> absorb unwanted sunlight heat. I also asked why
> the mounting ears were not in the center, as
> opposed to offset, and was told they tested that
> as well. Putting them in center did not imporove
> balance any.
>
> I cant wait to try these new coils.
>
> Scully


Scully interesting that you mention their reasoning about the color, because Dave J was all secretive about this on another forum, like it was a matter of national security smiling smiley

At any rate, that makes sense. It would be nice if Dave wouldn't be so paranoid sometimes and just share some info with the people that support their company, it would go a long way to building good will and PR.
Re: Coil color was discussed early on
April 21, 2011 06:51PM
Thanks for the info, Gene! Makes perfect sense too. Honestly, I never asked about either because I trust that they know much more than I ever will and certainly have their reasons. I used to ask a lot more questions but I found out quickly that "Dayum, they got this covered!" grinning smiley BTW, been meaning to email you and congratulate you on some of your late winter/early spring recoveries! You've been flat tearing it up Dude!! Congrats on the sweet finds!!!
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