15x12" SEF (Butterfly) Search Coil

[Canman]

15x12" SEF (Butterfly) Search Coil

Has anyone tried the 15x12" SEF (Butterfly) Search Coil on the Fisher F70 or 75 .I would like to know how it performs.Maybe how it performs on other machine compared to there stock coil.

 

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[Lowbatts]

Re: 15x12" SEF (Butterfly) Search Coil

Hey Canman,
Watched all the videos I could stand on this ginormous coil and just thought it too ungainly to wield on the stick. Seeing others post notes on negligible to no gains on the 10 * 12 SEF I discounted that as an option also.

But as I have been unable to find any coin or coin target over 8" deep with the F70 using the 11" DD coil, I fell into that old muscle car mindset. You know, there's no replacement for displacement.

So I pulled the trigger on the ginormous butterfly from Kellyco. 15 * 12 inches of coilistic joy on the way now. I have some ground I expect it to work well with, and I don't think swinging it will be a problem, as if the old muscle car addage is true on coils too, I'll spend much more time digging.

Given a few days to get it, it will hit the dirt within hours of arrival at pre-determined sites where it should be applicable. I'll let you know.

 

[Lowbatts]

Re: 15x12" SEF (Butterfly) Search Coil

Got that big SEF coil the other day. Had it out a couple times going head-to-head with the 11" DD coil on my F70. Here's my notes on it:

Mechanics:
Tried it out this morning and it was not good. It fit loosely on the shaft and the nylon bolt could not be tightened enough to steady it from up/down motion. It did not rattle or flop, side-to side though. The coil connector on the coil had a loose strain relief. The plug did fit the control housing just fine with no wobble.

Operational Attributes: (Test unit F70 at factory presets, and with adjusted optimal settings for test site)
Ground Balance: Good: Did fine with the Fast Grab procedure for the F70. Gave nearly identical GB settings as F70 with 11" DD coil. This would seem to indicate a properly tuned coil.

Target ID: Very Poor. Using random in-situ targets undug and unknown, compared to 11" DD coil. Also terrible with known targets using air test method with coin(s) on surface compared to 11" DD coil. The unit could not lock in a target range for either condition when using the SEF coil. This makes target identification impossible and does not aid in dig/no dig decision process.

Target Pinpoint: Good. Did indicate targets at point along center axis to the rear of shaft connection assembly for both known and unknown targets.

Target Depth. Very Poor: When using this 15 X 12 SEF coil, not only was there no gain in depth, there was loss of depth on some marginal targets when compared to the 11" DD coil.


Conclusion: The 15 X 12 SEF coil performed poorly. No consistent or useful target info on any tested targets. Only one of ten targets came close to proper ID, a piece of shredded aluminum, or can slaw at 4" which read just above nickel range consistently. Less depth on some unknown in-situ targets resulting in no target information. Targets under 3" did not read proper depth, the depth read remained at 3" for all coin-sized targets between 3" and surface.

All in-situ targets remained undug until after both the 15 X 12 SEF and 11" DD coils were used on the same machine. Coil passes over each target with each coil were done from multiple sides and angles. Using the 11" DD coil first, targets were estimated based on id and depth values from the first pass. Targets composition was established when dug, the 11" DD coil simply outperformed the SEF coil in ID, depth read and pinpoint. The SEF coil at best merely indicated good pinpointing on targets.

 

[Lowbatts]

Re: 15x12" SEF (Butterfly) Search Coil

Just got back from the last ditch effort to prove the ginormous 15" X 12" SEF butterfly coil on my F70.

No dice. I really wanted to get some aftermarket option that might get my rig to hit the 10" coin mark. Hadn't done this yet with the 11" DD coil. So today was spent hitting two sites and comparing the results at optimal (highest chatter-free) settings and reduced settings. Again the 11" DD coil won the day and as if by some act of Dr. Fisher himself the last coin I dug was a wheatie at 10", which could only be detected/id'ed with the 11" DD coil. I must add the SEF coil saw the coin in At mode but gave no indication w/regard to numeric value.

Again today the SEF coil failed to id clad quarters from surface to 6" no matter how small and tight I got my sweep around the target. The Fast Grab ground balance seemed to be in line with the 11" DD coil again and pinpoint worked alright, but ID was not even close.

As far as depth, a clad quarter read easily by the 11" coil to 8" after that it became unstable or too slight, except in SL mode where it hit to 10". This done while air testing the unit over ground I had checked for other targets and cleared.

The same quarter in the same place and position could not be read accurately using the larger coil until it was within 3" of the coil.

Gonna box it up and send it back Monday.

On the good side of course the last target did turn out to be a wheatie at 10" so I guess the rig did it's job with the 11" DD coil and I remain happy with it. Now I gotta find some better coins.

 

[Streak!]

Re: 15x12" SEF (Butterfly) Search Coil

I Feel pretty much the same about the coil as you do lowbatts. Absolutely No improvement in performance, and its a big ungainly floppy heavy expensive mistake. I've had mine for about a year now (got mine way before they were comercially available to Test, and NO, I didnt have to pay for it) , and its spent 363 days of that year hanging on the wall collecting dust. The stock 11" coil is deeper, quicker, lighter, ID's better and separates better. I feel sorry for anyone that falls for the hype and wastes $$ in this coil. It does seem to find BIG deep iron better...but unless you spend all your time looking for artillery shells, that aint much use to anyone. Having said THAT though, I have seen big improvements on some Whites machines with this coil, and have a number of friends that use it on their machines (Whites) with great sucess. About all I can get from that fact is that the stock coil on the F75 is hard to beat, while the Whites stock coil CAN be improved upon.
Anyway.....your right on in your assessment.

 

[U.K. Brian]

Re: 15x12" SEF (Butterfly) Search Coil

This is a really useful thread....lets hope it doesn't get deleted as a similar one on another forum was.

The truth is they can be an improvement depending on the detector used as Streak says. M6 and MXT don't have the greatest stock coil so you can justify the cost of a SEF. With Explorers the best performing one (pre Pro coil) I ever tried had a SEF fitted. So if I had an old Explorer I would get a SEF coil. If I had a later Explorer with the Pro coil I don't think I would bother with a swap as the gain doesn't warrant the price.

The only thing re the results quoted is that for coins I would not go above the 10x12 size. The design doesn't solve the age old problem of large coils losing sensitivity to smaller items as many suggest. A large SEF will still pick up small items as the reviews state but they don't mention that its at lower depths. With my T2 the larger SEF not only had me in fear that the handgrip would soon part company with the main shaft (creaking alarmingly at every sweep) but lost depth on small hammered, equalled it on medium and only provided a real gain (about two inches) on Viccy pennies (one and a quarter inches wide) and similar large coins.