Depth parameter of Detectors

[angel_09]

Depth is a parameter most detectorist always ask. It is their assurance wether their detector will be able to meet the expected requirements in the field. Is there a way in improving detectors depth capability?

 

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[angel_09]

Besides changing the coil?

 

[m bryan]

1.Keep coil low to the ground
2. Use headphones
3.Hunt wet ground
4.Minimum discrimination are a few things.......

 

[sniffer]

use a larger coil or a DD coil

 

[Tom_in_CA]

Some here have given the age-old admonition of switching to larger coil sizes, to get more depth. This is true, but there is always the "gotcha", or downsides: There is a "point of diminishing returns" to this rule of thumb, for coin-sized targets. At some point (usually at 9 to 12"-ish inches diameter), you no longer get coin-sized items deeper, but only larger items deeper. The exact point, for each exact machine, is up for debate. Some machines, like the Sov, can go up to 15" wot coil size, and ... yes: continue to get coins deeper all the way up to that size. Other machines will not get deeper on coins, once you've gone beyond about their 10" coil size. You simply see more ground (more coverage scope), but fail to get coins any deeper. Only big items (jars, cans, etc...) are more deeply detected. And you will loose sensitivity on smaller objects, the bigger your coil size is (although probably not a factor for coin-sized items, but would be for grain-of-rice sized items, for instance).

Other factors to consider is you add to the masking problem, when you switch to larger coil sizes. Maybe not a problem on the wide-open clean beach, where targets are spread out. But you might go crazy in an urban demolition or ghost town site, etc... with a larger coil. Depth becomes a non-issue in some areas, as you would simply null out and have no target separation ability. So what good did your "depth" do you there? None.

Also pinpointing gets warbly and funky when you get to larger coils. Ground minerals can also start to be more pronounced with larger coils, since you're "seeing" more ground.

Thus while it's true that larger coils go deeper, there is several counter points to keep in mind.

 

[luvsdux]

Tom in Ca is right on. Most of the locations I typically coin shoot have enough trash that the larger coils are actually a detriment rather than a help. In several, even the standard coil around 8 to 9 inches is difficult to work through the trash. In these situations I much prefer a coil in the 5 to 7 inch range even though the depth and ground coverage suffers a bit.
luvsdux

 

[angel_09]

Metal objects (coins, silver etc) retrieved by detectorist sometimes are within the layer of 6 to 10 inches deep. But there are some coins and objects that were burried deeper in lower strata, and if the detector is limited, say for example - 12" max, then anything below will not be sensed. What I'm thinking is, is there a way a detector's depth capability can be extended a little bit deeper without sacrificing the sensitivity? (Excluding changing with a bigger coil)

 

[U.K. Brian]

Double D coils will perform worse than concentrics except on mineralised or "busy" sites. You may be better to raise the coil to reduce the effect of mineralisation rather than lower it in some circumstances.

Suit filtering to site type.

Look beyond motion type machines to ones with an all metal primary search mode with just ferrous/non ferrous I.D.

Check out detectors that are not limited to 7 or 8 volts through the coil. Some can be adjusted to 44 or even 66 volts.

If buying a detector from a dealer air test a few of the same model, pick the best then try swapping the coils around. The best coil could gain you an inch in depth and the best machine another inch. I have seen depth differences between identical new models of four inches. You do need a friendly dealer !

Have several sets of headphones. My best phones with one detector will be the worse with another.

 

[Tom_in_CA]

angel_09, as Brian suggests, to get more depth, you'd have to content yourself with much less discrimination. If you're content to just have guestimates of iron vs non-iron (and have no other idea of highs verses low conductors) you can go a little deeper. Or ...... heck ..... if you REALLY want to "go deep", then simply go in all-metal mode. There are VLF all-metal non-motion pinpoint modes on a lot of machines, that would have no problem picking up coins over a foot deep, all day long. Heck, you can get some nugget prospecting machines that can pick up coins at nearly 2 ft. deep The problem is, you'll hear every staple, push-pin, birdshot, nail, etc..... You'd go crazy in most all land sites not having at least iron disc.

So the answer to your question is: No. There is no magic formula for increasing depth on your detector, barring the pro's and con's of switching to larger coils. Because think of it: if there WERE a magic way to increasing depth, don't you think the manufacturer's would already have been "all over themselves" to incoorporate it into their own machines, already?

 

[angel_09]

Thanks Guys. Your comments are all appreciated.

 

[U.K. Brian]

You could use a "Depth Doubler". Works with any detector because it just puts a current into the soil and that allows deeper detection.
Re detecting wet ground I did a bit of experimenting with this years back and dry or very wet ground would cut depth so damp ground should be best though there's some machines that don't seem to be affected as much by arid conditions and they all seem to run at very low frequencies (1 kHz).

 

[angel_09]

Hi Brian,

It seems I'm not alone on that idea. But i want to experiment more with the aid of scope.

 

[White Feather]

I took my White's Surfmaster to Bonaire a few years ago. I was walking the beach and got a hit. It was wet sand. The target kept reading as I dug deeper and deeper. At elbow depth, about 18 or 20 inches I found a single mercury dime. It was badly corroded and the date was not even visible. Later I got several hits while diving in about 70 feet of water that I had to give up on because I was limited in bottom time. Sometimes shallower is better.

 

[Tom_in_CA]

angel, I'm not so sure Brian's suggestion of the depth doubler device (which is like an electrical current that persons sometimes use to bring worms to the surface for fishing bait) is a workable idea. I tried one, back when they were first advertised, and I'm not so sure it's the "cat's meow" for magically increasing depth.

Despite how well it sounds on paper, and how good the ads looked, they faded from memory. Here's my take on the product. Scroll down on this thread to where I posted "I tried one", to see what my results. Others may have had some different results, but these were mine anyhow.

http://members5.boardhost.com/MetalDetecting/msg/1286321219.html

 

[Frankn]

Notes: Yes the Surfmaster PI goes deep I have pulled targets from 2'.
Some detectors actually get no increase in dept from a larger coil because you are putting the same transmitt power in a larger area. Some detectors have power adjustments for larger coils.The newer whites even have adjustments for specific coils. Check before you buy. Some dealers will also let you try out coils for coin tests.

​

 

[U.K. Brian]

Tom, your post does really agree that you can obtain more depth using the "Doubler". Just not double. My post was the one above on the forum at that time. Unfortunately that forum started to become a little silly with all theory and little fact and the spate of racist attacks that the moderator didn't do anything about meant that discussion and test results on "Doubler" type machines, halo effect etc moved on to other forums in Europe.

From what I remember the test results came in with improvements of between one and four inches with different users on different soils. If on bad ground thats pretty good results. I used a twenty year old test bed where ground effects meant most machines in iron discrimination maxed out at six to seven inches on a copper coin the size of a quarter. A Doubler added a fraction under two inches which was a useful improvement. Going to a larger coil size meant more ground effect pickup and with many larger coils a drop in sensitivity to small items so wasn't really an option.

Doubler type devices would be of little use to most people but could be of use on specific sites.

 

[Silver Searcher]

Depth, Depth, Depth......no matter how much we get, we all want more were will it end there will always be finds beyond our depth, be gratefull for what you get

SS

 

[U.K. Brian]

That sounds like the mantra of those who work ploughed ground and pick the finds from near the surface. Much of the U.K. is hills/mountains and rarely if ever see's a plough.
Depth is all, with discrimination a secondary consideration. The plus side of no ploughing = no plough damage.

 

[Silver Searcher]

That sounds like the mantra of those who work ploughed ground and pick the finds from near the surface. Much of the U.K. is hills/mountains and rarely if ever see's a plough.
Depth is all, with discrimination a secondary consideration. The plus side of no ploughing = no plough damage.

To true Brian...but how far down in those hills are the lost finds buried, way beyond nearly all detectors.

How many fall under National Trust, and covered with forrest. And why go to these hills, when like you say there are ploughed fields(and still plenty untouched) to search.
I actually thought about concentrating more on pasture, but that meant a new machine and the learning curve that goe's with it, perhaps in the future

I wonder how many of the Great pieces in the British or any outher Museum, have come from your hills, to many people get hung up and depths and air tests, your first priority is location, find a good area and the goods won't be far away

SS

 

[U.K. Brian]

Or find a good location and you can't get on it as the farmer/landowner has two or three people knocking on his door every week seeking permission.

I've followed three Americans who have followed their dream of retiring and moving to Britain to detect full time and the one who did best lasted under a year. Though they all seemed to have very good pensions they could not cope with the cost of living and soon realised that the finds made hardly covered the full costs in searching for sites. Which is why they are prepared to pay a couple of thousand for a weeks detecting with arranged sites (and try not to worry if the site has been salted or not).