X-Terra 50 + 18.75kHz coil + gold rings = WOW!!!

[Digger]

I just got the 18.75 Khz coil for my X-Terra 50 late yesterday afternoon. It is 34 degrees and misting here this morning. But it is suppose to be sunny and temps in the upper 40's tomorrow. God willing and the creeks don't rise, I will be able to get out and do an actual field hunt with it tomorrow. So far, I am very impressed with what it has been able to accomplish in my old test garden. Although I found the numeric display to be a bit "off" from the target readings on the 7.5 Khz coil, it is still within a range that I would know what I was digging. One target that did disappoint me is a dime I have buried on edge, between a nail and a pull tab. The 7.5 Khz coil will separate it out easily. But, for reasons I haven't figured out yet, the higher frequency coil has not separated it to a point that I would probalby even notice it was there. Maybe it is the sweep speed? Or, I might need to make some adjustments to the sensitivity and see if that helps. The most impressive results were on a 14K yellow gold men's band. 8-inches of wet dirt and 5 inches of air still produced a solid, steady tone. With just an airtest, another men's yellow gold band hit a solid 14 inches with visual ID. Now before some of you go off telling me about how air tests don't mean squat, let me say I generally agree. I don't believe airtests prove anything when comparing different detectors. However, I have found that even airtests are a good way to make comparisons between different coils on the same detector. And, in comparing the 7.5 coil to the 18.75, the gold jewelry I have checked is detecting 20 - 30% deeper with the higher frequency coil. Hopefully I am able to get out tomorrow and put it through its paces. HH Randy

 

[Ralph Bryant]

Hi Randy,

Sounds like the 18.75 will be the ticket for gold jewelry hunting. I'm interested to know, using the 18.75 coil, if you can hear anything significant in the audio response between a pull-tab and a gold ring that I.D.s within the same segment ? Or is it like most other machines in that you just have to take your chances when dealing with the tabs without relying too much on the audio variations ?

Thanks,

Ralph

 

[Digger]

It is still misting here, and temps are in the 30's. So, I have resigned myself to further testing the coils in my shop. To specifically answer your question, I cannot tell the difference in some trash items and some gold items. For example, round pull tabs read a 15 on both coils, and I have a small gold initial ring that also reads 15. Sweeping them both back and forth over each coil, I can't hear any differences. I know some guys say that they can hear the differences in clad and silver, but I can't. Just too many years listening to 1000 ~ on communications switching equipment.

I found the visual IDs to vary between the coils. Half dollars read 45 on the stock 7.5 Khz coil, but read 42 on the higher freq 18.75 coil. Quarters read 42 on the stock coil and 39 on the higher freq coil. Clad dimes read 36 on the stock coil and 33 on the higher coil. Oddly enough, nickels and zincs are the same on each. In all instances, as I increased the sweep speed and increased the depth, numeric readings became less consistent. Slowing the coil down to what some other Minelab hunters might consider normal, will not respond to some of the smaller targets. The X-Terra must be swept fairly quickly to maximize the potential.

Round tabs read 15 on each coil. Small square tabs read 27 on each coil. But, as I increased the depth, the numbers became jumpy and fluxuated from 24- 27. Larger square tabs read 24 on both coils. Screw caps read anywhere from 18 - 27 on the high freq coil and those tested read solidly as 27 on the stock coil. An old 2 cent piece read 33 on the stock coil and 30 on the higher coil. Several IH cents that read a consistent 27 on the higher freq coil gave readings of 27 and 30 on the stock coil. Silver dimes read one of 30, 33 or 36 on the higher freq coil (depending on the specific dime). But were each one notch higher on the stock coil with readings of 33, 36 and 39. A large men's gold ring read 18 on both coils. Depth between the two was similar at 12 - 13 inches of air. A very small lady's gold ring read 15 on both and the higher freq coil did have a slight edge in depth of detection.

What do I make of all this???? It seems to me that, once you get target numeric readings of 30 or more, the stock coil will provide a reading "one notch higher" than the higher frequency coil. In other words, 45 on the stock coil became 42 on the higher freq coil. 42 became 39. 36 became 33. But, once you got to 30 and below, they were pretty consistent with each other.
The coin depth "edge" goes to the 7.5 coil. Without exception, the stock coil achieved approx. 20% more depth with each coin target. More with dimes. But, less with jewelry.
Sensitivity to small gold jewelry gave an edge to the higher frequency. Not the big rings, but the smaller ones for sure. And, according to the experts, the higher frequency should be more sensitive to smaller targets.

This may turn out to be an excellent coil for those who like to hunt the beaches for jewelry. Large enough to cover a lot of sand. But small enough to not wear you down. I don't know how it will respond to wet sand, as we don't have beaches here. I do know that it responds very solidly to the gold jewelry that I tested with today. And, as I said before, if the mist stops and temps warm up a bit tomorrow, I intend to take it out for a hunt. HH Randy

 

[plugger]

n/t

 

[Dan-Pa.]

Unfortunately older machines had these audio variances and have a Tesoro Golden Sabre Plus(circa 1985) that will beat the pants off anything on the market rel audio variances gold rings versus trash to cut down the odds...of course newer units go much deeper and have fancy meters and bells and whistles that make them outstanding units..
Judging by Digger's tests seems like the new higher frequency coil is a winner and will grab some darn deep gold rings..By the way saw my buddy grab two gold high school rings with an Explorer from the 20's and 30's. at 7-8 inches So Minelab continues to make outstanding units...

 

[Ralph Bryant]

Hi Randy,

Your results are about what we should expect in changing between frequencies. It is akin to the frequency/VDI shift between 3 and 15 kHz on the DFX, acting as it should without normalization being brought into play. The lower frequency signaling better on coins and the higher frequency signaling better on lower conductive gold and nickels is also to be expected. The nickels and zincs are probably located within their individual segment VDIs in such a way that they are shifted within the segment, but not enough to jump to a different number. Unfortunately I think we will end up finding that the higher frequency is noisier on the wet salt sand as well for the same reasons.....it is just more sensitive to wet conductive salt.

Ralph

 

[bill(de)]

just ordered an X-Terra 50 and feel real good about it. I had a DFX and remember reading about Whites adding the VDI normalization circuit to read same VDI as 6.59 detectors due to frequency differential.Just wondering if there is a normalization cirquit.

Perhaps the dime is masked due to the higher frequency having more
propensity for the pulltab.

I agree with your airtest explanation as i did that using a zinc penny buried at 5" with a Modified IDX Pro and pre modified Classic ID and could see the dramatic difference post classic ID mod with 950 coil.

Just wondering Randy if you tried or could try rejecting all low end and high end targets and just zone in on likely gold targets to see if there is a depth difference on the 14K Gold Ring

That higher frequency sure appears to like the yellow metal.

Thanks again Randy and look forward to your insightful posts. HH Bill

 

[John(Tx)]

n/t

 

[Digger]

I should have stated that I was running in all-metal mode. My gold jewelry comes in all over the low - midrange area. But, I suppose I could reject all the notches below 9 and all above 30 and see how it effects the readings????? HHHMMMMM. I will try that tomorrow and let you know. thanks.

Randy

 

[Digger]

I don't know how much they will cost yet, either. I will let you know as soon as I find out. HH Randy

 

[wpaxt]

We've got negative tides out here all weekend so I will be out with the new coil on the beaches. Also intend to try a park or two if time permits.

It should be interesting to see how the higher frequency coil runs on the wet sand.

Look for a post or 2 from me toward the end of the 3 day weekend, and Happy New Year, buddy!

Bill (S. CA)

 

[Digger]

Keep those of us who are "land locked" posted on your finds. From what I can tell so far, I think this coil will be a good one for jewelry. Happy New Year to you and yours. HH Randy