F75 w/5" DD vs. EXII w/6" EXcelerator

I just picked up a nice, clean used 6" EXcelerator, which is a popular coil for the Minelab, and wanted to see how it stacked up against my 5" DD fitted to my F75 in my test bed. I set my F75 to D-0, Mode-De, 4h and Sens~80 yielding a light to moderately noisy (crackly) threshold. I set the EX to no discriminatin except for nails and crowncaps with Gain=7, Fast and Deep both set to OFF and AUTOSENS=28. The background threshold on the EX was a constant low hum, as usual.

Both units easily ID'd a 4" zinc penny, 4" nickel, and a 6" silver dime. The EXII easily found my next target, a 7" silver dime, with good audio and ID. The F75,however, gave a very weak signal that disappeared after repeated sweeps in any direction. I would have passed by that target with my F75. The next target, a 8" silver dime, gave a poor visual ID on the Explorer and a very marginal signal that I probably would have examined further in clean ground, as it repeated in all directions. Surprisingly, the F75 hammered the dime with a nice high tone and perfect ID! Why the difference between the 7" and 8" dime using the F75... I don't know.

My next target is a dime buried at 4", 4" away from a nail buried at 1". Both units picked the target from any direction, a target that both detectors missed (from any direction) with stock coils (including the EXII w/Pro coil).

My next target is a crown cap buried at 4". The EXII nulled out or gave a very clipped signal that I would not dig. The F75 gave a strong signal with wildly different tones after each swing, a classic sign of a screw cap.

My next target is a silver dime buried at 4" with four nails buried at 1", equadistant and 4" from the center of the dime. The EXII nulled constantly from all directions after hitting the nails and missed the dime altogether, even at extremely slow sweep speeds. The F75 gave a good audio signal at most swing angles, but more surprisingly, gave a good visual ID at nearly every angle. Both stock coils mounted on the respective units missed this dime.

Conclusions:

1) The performance of each coil was surprisingly deep, and barely any less, judging on quality of tone and visual ID, compared to the stock coils. I'd recommend using these coils initially as a beginner as the effects of nulling and target averaging are greatly reduced. The EXcelerator 6" coil may be a little deeper than the Fisher 5" coil simply due to its size, but the EXII electronics are 'deep' regardless of coil.

2) My complex target with four nails highlighted the advantage of the 5" coil over the 6" coil but the effect of the electronics is uncertain. Had I had a 5" coil on the EXII (which DOES exist), I might have seen the target.

3) Smaller coils obviously give up a lot of sweep area and the 5" coil is at a 16% disadvantage compared to the 6" coil. Using these small coils puts the user at a 50%+ sweep area disadvantage compared to using the bigger, stock coils, but the unmasking capabilities cannot be disputed.

Some may believe that my red clay SC soil gives a slight advantage to the EXII however testing of both units in my test bed using stock coils shows about equal depth.

If anyone has a 5" EXcelerator coil that I might borrow, please PM me as I left a few questions unanswered.

And soon I will repeat the test using a F75 LTD running in the new, hot BP mode.

in this situation of your test.."My next target is a dime buried at 4", 4" away from a nail buried at 1". Both units picked the target from any direction, a target that both detectors missed (from any direction) with stock coils (including the EXII w/Pro coil)."

Try the 75/stock coil with the same settings except use BC, slow your sweep speed down and see if it can give you an indication the dime is there. If your test scenario happened in the field, you'd know that the target was fairly shallow, so you might want to experiment with different coil heights also. I've done this and I just want to see if you get similar results.

I just shipped my F75 to a friend in Germany who's White's Eagle went kaput. I'll have to wait until the LTDs arrive to re-do that test.

I can say with certainty that the F75 missed that target using all other modes when using the stock coil and normal swing speeds, as I tried all the other settings. When approaching the target from the coin side, I could see the silver if only the tip of the coil was over the coin, but when both targets were under the coil, the signal turned into a low nail grunt. (Same with the EXII).

The EXII sometimes produced a brief high tone if you did the Minelabe wiggle across the targets with the center of the coil over the coin (and the nail off to the side but still under the coil), but the signal was so infrequent that chances are I'd never hear it. I would never hear the high tone using a normal, slow sweep speed.

I don't often have good things to say about the F75 because in comparison to other units I've used, it's been unnecessarily noisey and in the places where it would excel AT "0" disc (iron laden homes), it's been unusable because of EMI. At 6 disc the tones become more choppy and the sound of a dime on edge or next to a piece of iron sound similiar to iron falsing. The benefit of the Explorer models is you can turn "deep" and "fast" off and the high tones become extended a bit so the choppy falses remain choppy and the good sounds are elongated. I brought this up here once before and Tom thought it was a bad idea to add such a filter to the F75 because it would give an unrealistic view of what's in the ground. I still disagree.

That being said, I have found the F75 with the 4X6 to be unbeatable - getting outstanding depth while reducing EMI to a level allowing 99 sens, "0" disc, and OFTEN JE processing in the same location that the 11" DD can't come close to those settings. I can see where those of you that can operate at max setting with the 11" DD are in love with this machine.

About a year ago, I went over a home site with my Explorer II and the pro coil, and found a few modern coins and one old token. The problem was it null'd a great deal (a 10" plug would have 4 modern nails in the top 3" and 4 square nails below) so I tried the site with ferrous tones and a wide open screen. After getting abused by iron tones for an hour, I had dug one barber dime and several square nails.

The F75 was nearly unusable (inner-city home) with the 11" DD. Soemthing made me try the 4X6 and I was blown away. 3 silver coins, 2 indian heads, and 3 wheats later (and several nails of course), I was sold on keeping this machine for at least this type of work. I can only hope the LTD will fix this "0" disc susceptibility to EMI when using the 11" DD.



Edited 1 time(s). Last edit at 09/16/2009 02:16PM by Shambler.

The 4x6" elliptical is the equal to the 5" DD as its depth is equal, or a little deeper at the center, and almost equal to the 11" DD, and rejects bottle caps and iron with ease. The 5" may be a little tighter but the "bigger" 4x6 offers a 20% increase in coverage. I'm keeping that coil pending usage on the LTD.

Nice report.
Thanks for taking the time to post this. I've been trying to make up my mind on which one of these coils I'll buy and this report will help a lot. So far I'm leaning towards the 4x6".
Mike

Thanks for the kind words; it's my Engineering background creeping through.

Does anyone have a 6" EXcelerator coil that I might borrow for testing on my Etrac in the nest month?

...Or where I might find a nice used one for sale?

You may want to look at the 8x6 SEF coil it's attributes could put the others in the shade.

E-Trac now eh? That's great because here is something I'm paying attention to with mine and I'd be curious to hear the following component reported on as you do further testing. I regrettably didn't consider this enough when I had my XS, II, SE, and SE Pro and used them in comparison situations. The E-Trac graphically shows what the computer is doing to the sensitivity in real time (vs your setting) when you are in auto with its dual sensitivity gauges so I wonder what yours will do in this aspect when you are actually doing the test the next time. In other words, even though you are trying to "coax" the detector to run, say at 23, when in auto, it seldom actually will be and as such what is it actually running at when you are sampling the target(s)? Of course, even if you are running auto 23 +3 for example, it may typically blow off your intentions and go to a much lower setting. I've been noticing and seeing with mine just how much the computer typically "throttles it back" (sometimes EXTREME!) but the detector still hears a target usually pretty well, right? Makes me wonder just how much I'm missing, or perhaps more correctly, failing to audibly comprehend, with a fixed (and proportunately much higher) sensitivity on my other detectors? I suspect AT TIMES, that can be THE culprit moreso even than the specific detector/coil. Back on your original test, and just a "what if"......what would have happened if you'd have turned the F-75 progressively down while over that problem dime? Would there have been, and if so, what would the optimum "unmasking and defining" sensitivity setting have been? As folks do any comparo tests with a Minelab Exp XX or E-Trac particularly when using auto, against a user set fixed sensitivity detector, whasss really happenin'?

Rick,


Kellyco has that coil on sale for $110. right now.
I do have a SunRay X-5 you may use though, p.m. me.

Aaron

Hmmm... the X-5 might be a better choice... exact same size as the Fisher coil.

Good post Brad.