logical approach "
strategy," but I guess you could. I like 'simple' and I also like 'logical' or 'practical' [size=small]
(which can sometimes be the same or they can be different endings)[/size] and it was very 'simple' to reach a 'logical' conclusion as to what it would take to search an open area and have a chance at a signal on all the older,
typical US coins there, especially to include older USA silver coins.
For one, you can't just hurry along at a rapid-sweep pace, using broad sweeps, and expect a search coil to cover all the ground associated with it's size. Yes, a smaller-size search coil [size=small]
(which I have used the majority of the time since summer of 1968 )[/size], and I use smaller coils most of the time ....
with the exception of when I want to "clean out" an area.
Yes, I like, and prefer, to search for the older coins [size=small]
(especially silver)[/size], trade tokens, buttons, and other neat old keepers. I concentrate on some of the oldest sites I can find, and most often they are quite littered, especially with nails and other forms of iron debris. I use smaller-size search coils, keep my Discrimination
very low, and search an area slowly and methodically. That is my 'strategy' and it is a 'simple' and 'functional' way to achieve 'performance' and favorable results.
If you want to search urban type sites that are well dated and have the potential to hold older coins and other keepers, then your approach will be a little different. I am referring to places like wide-open grassy parks and sports fields and the like. The best 'strategy' means you have to analyze the site environment ([size=small]
check for open areas as well as places that impede and thorough search like trees, brushy areas, structures, etc.)[/size] and first work around, in and amongst all the brushy areas, near trees and structures and obstacles so you will be ready to methodically search a remaining wide-open area.
That's the easy part, but will keep you busy for a while top get started because you will need a smaller-size coil to get in, around and close to structures, especially metal poles, pipes, etc. Take the same approach as you should for the open areas by using an All Metal mode or a Discriminate mode with minimal rejection and --- clean the area out! All the good stuff and all the trash, making sure you re-scan all areas to see if any good targets had been masked by a just-removed piece of junk.
Once you have
'strategically' cleaned out all of the areas in and around the borders of the open grassy park or field, you are then ready to switch to a larger-size [size=small]
(stock)[/size] search coil to thoroughly work the open site. If you want
all the older coins and good stuff ... and if you guess that most of the older targets might be a little deeper than modern losses for some reason ... and you want to be as thorough as possible ---- then the best
'strategy' is to:
1.. Plan to recover ALL targets, good and bad, shallow and deep, as you very patiently sweep the search coil in a direct side-to-side path and not arc the coil.
2.. Sweep back-and-forth not one direction, but both ways [size=small]
(I usually make three passes over an area I scan)[/size] to ensure you don't miss a target that might be canted or too close to some offending/masking/obscuring object.
3.. Keep each side-to-side sweep a limited length so as not to make an ineffective sweep coverage, and mine are usually about 24-30 inches side-to-side, and no more than 3 feet in sparse-target environments.
4.. Remember to overlap the search coil as effectively as possible. For 'average' modern coin losses that might be about a 50% overlap of the coil's former search path. To be very thorough, however, the smallest or narrowest portion of the EMF should not advance more thqn the diameter of the smallest common-size coin we are looking for, and even at that one could be missed. So the coil ought to be advanced, after 2-3 sweeps over the same search path, no more than ½-the-diameter of the smaller common coin.
Here in the US that would be the 10¢ Dime which has a diameter of .705 inches, so the coil should only be advanced half that distance, so only .353 or about ⅓ of an inch in order to have the best chance to not miss a deeply located dime.
5.. Be sure not to get carried away with a too-fast sweep speed as that can hamper small or deep target detection. On the racer 2 in a large park type setting, I would purposefully use the Deep mode and a slower, methodical sweep that might take 2 seconds from left-to-right, a second to pause and reverse direction, then another 2 seconds to cover the very same sweep route from right-to-left. So it would take about 5 seconds to make a 2-direction sweep that covered a 30" path.
6.. Try to make a very useable grid of the area to ensure total coverage.
Dave_E said:
I found a local park that was established in about 1890. It's about 300 yards long and 150 yards wide.
That's good to have an older dated park to search, and hopefully it had ample activity in its earlier days.
Now, let's presume the park is all flat ground and grassy, and doesn't have any tress, brushy areas, playground or other obstacles to hamper a thorough search of this area.
Let's see now:
300 yards long = 10,800 inches
150 yards wide = 5,400 inches
If you divide the width into 30 inch grids, that will make 180 gridded lengths to search.
If you figure three ⅓ inch sweep paths per inch of the grid length, that will be 32,400 individual 'sweep paths' per grid length.
Next let's calculate the time to thoroughly cover one 300 yard/10,800 inch gridded length, and that is 5 seconds to make a side-to-side sweep both directions. 5 seconds per sweep path X 32,400 individual sweep paths = 162,000 seconds.
162,000 seconds = 2700 minutes, and 2700 minutes = 45 hours.
So, it is a strategic calculation [size=small]
(strategy)[/size] to figure 45 hours of non-stop, continuous coil motion searching to work one of the 30" wide grids the length of the park. Well, a 45 hour search of 1 grid length X 180 grids = 8,100 hours of non-stop, total coil motion searching.
8,100 hours = 337.[size=small]
5[/size] total 24 hour days, non-stop!
Next, factor in the following:
A.. Adding time for target recovery and getting back up to begin where you left off.
B.. Battery drain creating down-time to change batteries.
C.. Cost for a search team crew to spell each other off for sleep and food and a mother nature moment, but being there to immediately step in and not interrupt the search coverage of each grid.
D.. Weather conditions in the 337+ days that could make hunting this site to clean it out a real challenge, or being impossible should there be snow and/or ice, or terrible storms like a hurricane, tornado or electrical storm.
Seem impossible? Yes, it certainly is, and that's why we still have coins and jewelry and other keepers out there to be found even after over fifty years of metal detecting hobbyists started working parks and other locations.
Dave_E said:
Is there a strategy to get under all of the modern targets and trash to find old targets, other than simply digging all of the junk and modern stuff out first?
Nope, can't be done. Target masking is just that, and you have to remove the junk to get ALL of the desired finds. It's time for the good old-fashioned
'Beep-DIG!" approach to thoroughness and cleaning a site out.
Dave_E said:
I have a Makro Racer 2 with standard and OOR coils. What would your approach be with the detector settings and coils available? (ie...Big coil first with settings X,Y,Z then small coil with settings A,B,C).
More or less answered already, but I use my Racer 2 with the smaller coil most of the time in dense trash, and do so in the 3-Tone mode with a high Gain setting, if tolerable, and low Discriminate setting.
In modest trash areas where junk isn't so crowding, I might opt for the 5½X10 DD coil and use similar settings, but search in the 2-Tone mode.
If it is a very open area and targets are pretty sparse, then it is time for the standard 7X11 DD coil, use of the 2-Tone or Deep mode, and all the Gain I can handle with the most limited Discrimination I can tolerate.
Monte
