SEF 18x15. Unimpressed! :shrug:

[Sir Shane USA]

I'd love to know I was doing something wrong but the depth is the same or maybe a half inch worse than the 950 I have on my White's DFX. And it seems to read trash as coins a lot. (too much digging) I buried a penny at 7" and both coils barely picked up on it. Had I been sweeping thru the area, I'm sure I would have missed it. You have to sweep the same area a few times to get some indication a coins there. Then it reads like a quarter. :angry: I also did an air test and both coils were pretty much the same. The SEF 18x15 was slightly better. I just feel it should be much better with depth. I did these test on coin mode only. So only advantage I see so far is coverage area per sweep. But I had heard great things about the depth of these coils, I just wonder if it's flawed or I'm just doing something wrong. Wish I could get someone to look at it to make sure its working properly. As it is now, anything below six inches is out of range for me as far as coins. Not good. (BTW. I bought it used with no manual. Would it help any having a manual about SEF coils?)

 

[burlbark]

You should get 12 inches on a quarter air testing with that coil and DFX. You should almost get that with the 950 also.

Have you tested the coil?

What are your settings with the DFX?

 

[Larry (IL)]

If you are using the factory settings, that is your problem. The factory programs are a bit lame for depth but good for stability. There are some programs on the DFX forum that will give you better depth. Unless your ground is very mineralized a SEF will not give you more depth than a concentric coil, but it will have better separation.

 

[ronhob]

Check your PAG setting. I used to run a dfx and it took me a while to figure out that the Pre Amp Gain setting dramatically affects your depth. It's pretty much like a magnifying glass. 10X for each 1 PAG number is the way I understand it. In very open areas it will run deep if you can get into PAG 3 setting. EMI may restrict you from this high of setting if you are around a lot of power lines in town. I could almost max mine out with a 12" DD excelorator coil in an open field on the edge of town. I would say your SEF coil will do much better than that, given the right AC and PAG setting. To run it really hot, you may need to take it to a remote area to test it. This will give you the best idea of how it performs as far as depth.

 

[ChrisK7UND]

I don't have a DFX, but was looking into the SEF coils for my machine. I have to disagree with the others on checking your settings. Your goal was to test the two coils and you did just that with the SAME settings. So if the coil was truly making a difference, then it should have been better with the SEF. There is no doubt you can change the settings on the machine to get more depth. I think the real question was did the SEF Coil make a difference. If you tweaked the settings for either test you would have tainted the results. I have to agree with Sir Shane here. Unless you got a bad SEF, I wouldn't be impressed either.

 

[Critterhunter]

As a general rule of thumb I always read/experienced myself that about 14" in max physical coil size in a DD was the limit in terms of still gaining depth on coin/ring sized targets. About 10.5 to 12" for a concentric in that respect too, in general, as DDs tend to hold onto small target sensitivity better as they increase in coil size. There comes a point where the size of a DD or concentric starts giving less depth on coin/ring sized targets. Bigger is not always better in that respect.

But, the other major factor as to max coil size for gains in coin/ring sized depths is the minerals you are in. In that case, I found the 15x12 did not get as good of depth as my stock 10" coil in my mineralized soils, and often gave better depth for it's self if I lowered sensitivity a good bit lower than what was max stable. Just sucking up too much ground stew I would think when ran too hot. Even the official field test of this coil shows at dime/sub-dimed target sizes the 12x10 takes the lead in depth. The 15x12 was a half inch or so deeper on say half dollar sized targets or bigger, which one would expect.

In my soil around a 12 to perhaps 13" coil size is the max in a DD to still see gains in depth on coin/ring sized targets. DDs also ride on my soils/sands better and give me more depth over a concentric due to a DDs smaller view of the ground matrix. Not even sure if a round 12" coil is not too big for gains in depth in my soils. The 12x10 is the deepest coil I ever used in my soil due to it's rather sharp focused less "fuzzy" field I would suspect, while another 12" round DD coil doesn't seem to get the same depths for me in comparison.

The 13" Ultimate might be the rule breaker though, and I suspect due to it's unique design that seems very different from "conventional" round DDs by both the looks of it and also it's traits in the field. I don't think it's deeper than the 12x10 in my soils or sands, but it might be as deep. Still contrasting that when I replace the loaner I had with one of my own to sit along side my 12x10. The 12x10 is my coil of choice for stability, depth, and fantastic left/right separation, but I do like the Ultimate for coverage in very large areas I want to grid faster, although the 12x10 is still a nice improvement in that respect over my stock 10" coil. The Ultimate may be big, but it's weight is lighter, like the 12x10, than my stock 10" coil on my machine. Won't wear me out in long grid searches in big open areas of fields or beaches.

While, depending on soil/sand types, the 15x12 might be borderline for some one way or the other on depth gains for coin/ring sized targets, for sure that 18x15 is well beyond the realm of that and is meant more for a cache or large relic coil, or for large area coverage where that is primary on coin/ring sized targets and depth is secondary.