question on 4" coil

[scotrod]

my 4" coil arrived this morning so i air tested it on my tracker iv at first i passed the coil over a penny slowly and it picked it up at approx 4" but then i found when i passed over the same penny at faster rate my depth pretty much doubled my question is why did i get more depth at a faster speed then a slow speed thanks

 

[mwaynebennett]

My guess would be auto ground balancing. If you passed the coil over the target at a VERY slow speed, it may not detect it at all. The BH looks for anomalies, things that are different from the "background." If you swing slowly, the electronics detect the target as part of the background and tries to adjust itself to account for such.

Does that make sense?

Mark

 

[scotrod]

mark i kind of understand but wouldn't the opposite occur that auto balance would not be fast enough to distinguish at a fast speed

 

[capt.]

Different detectors work better with different swing speeds. Finding how fast to swing your detector is a key to getting the most from it. I can tell you that you will really like that small coil. I love mine on the 505 for the parks and tot lots. On the 505 in disc mode it will identify up to 5 and 1/2 inches and in all metal it will pick up coins up to and past 8 inches. It is a great addition to your arsenal.

capt.

 

[BDCC13]

I've been advised by my club not to read to much into air testing. If you want a good test make a garden. Go out and bury different items at different depths. The soil composition and dampness will give different readings. not to mention the halo effect. I've tried the air tests, said my 505 won't read accurately past 5-6". Been digging solid signal dimes at 8". Hope this helps ya out. Go out and set your machine at max sensitivity and no discrimination, dig everything and learn how your machine reads stuff.

HH.

 

[scotrod]

thanks for the feedback i hunt mostly ghost towns and their loaded w/trash so from reading good things about this coil though i give it a try just as soon as this three feet of snow melts come on spring

 

[salmonriverhotrock]

On my BH 505, it is very rare I bother with the depth indicator (if it did not have one, I would not miss it either) and as a rule of thumb, most coins will be found on the surface to at or about 4 inches deep.

You will love that 4" coil in trashed out areas, getting in closer to metal posts or fences and sheds, finding smaller items, and searching in soils with more mineral content.

Air testing can be helpful in learning a machines various responses to metals but the real education begins when hunting Old Mother Earth. And any of these machines with all the Bells and Whistles can be fooled because they are pretty much set up for the most sought after metal alloy contents that make up coins for instance and soils that would be most encountered. But if a piece of metal has about the same alloy make up as a coin, don't be surprised to dig up some foils when the machine said it was a silver coin. Not all bottle caps or pull tabs detect or display the same either. All my detectors but the BH 505 are hunted by sound only, no identifying tones or depth, but I keep a small collection of various things I've found through time that did not Tone Identify or Discriminate correctly. I keep a small Tackle Box with my smaller metal detecting stuff in it. Even for my Gold Machines, I have Hot Rocks I've saved and even made up a zip-lock bag full of black sand for my testing.

The best thing you can do is make a Test Garden and map it but first making sure there are no other metallic objects in it. And to make it interesting, put a nickle under a Hot rock or place a pull tab by a copper penny. In the real world of detecting, not every coin is going to be found free of other things around it or from being under the coil at the same time. Set up a garden that will drive it almost nuts.

 

[capt.]

I need to add that my test measurements were in a brand new coin garden, with out any halo or trash. I have also dug deeper targets with my 505 "in the field".