Comparison of the Tesoro Sand Shark and the Nokta Fors CoRe on dry, sandy soil
A plot approximately 10 foot by 10 foot was defined in a back yard setting. The soil had not been disturbed for a minimum of 12 years. The Sand Shark was used to locate targets, which were marked with uninflated balloons. Once all targets were located by the Sand Shark, the Nokta Fors CoRe was used to rescan the plot. New targets that had not been located by the Sand Shark were marked with a different color balloon. The Fors CoRe found 7 targets that had not been located using the Sand Shark. These targets were then rescanned with the Sand Shark to see if they would give a signal. One target did not signal at all, one gave such a faint signal that I would not have dug it, two targets gave very faint but repeatable signals, two gave medium loud signals and one gave a loud signal.
Once I was satisfied that all targets identifiable by these detectors had been found, both detectors were used to rescan the targets and notes were made as to signal sound, loudness, and ID # where applicable. The Sand Shark is a PI detector, thus has only one mode to test. It has a 10 inch round coil and the pulse width was set at the factory default, with the threshold set to a low constant hum. Battery test gave 7 beeps, thus battery strength was good. The Nokta has four modes, and all modes were tested using the same ground balance, factory default settings except for ID mask, which was set at the minimum value that would give a reasonably stable signal. The factory standard DD coil was used. The battery meter indicated full battery power. Headphones were used for both machines. On the Nokta, the GEN mode (all metal) was used to initially locate targets, as this mode is the most sensitive to targets under these conditions, and most comparable to a PI detector.
A note about targets #1 and #2: The first target actually dug was the #2 target, as it had the best signal of the two. I made the assumption that the target must be deep, as the Sand Shark is sensitive to small targets and was having trouble catching this one. I gave up searching for this target in frustration but in looking back at the size of some of the targets that were found, I believe there was a target there but it was very small and got lost in the deep digging. Chalk it up to poor technique on my part. Target #1 may have been the same problem or possibly some mineralization.
My starting premise was that the PI detector would be deeper seeking and that is why I chose to use it to initially locate targets. However, it was quickly evident that the Nokta was deeper and more sensitive under these conditions. After I had located all targets in the search area, I rescanned some of the area with the Nokta in Gen mode and the sensitivity at 90 and quickly had multiple repeatable signals that the Sand shark did not hear at all. Wow! Now I am even more curious how the two detectors compare under the challenging conditions of a saltwater beach.
I am confident that my Nokta is deeper than my Sand Shark on dry land in sandy soil (ground balance 65), so I no longer feel I might be missing out if I park hunt with the Nokta and leave the Sand Shark at home. So now the question is, how do the modes of the Nokta compare to each other?
Sand Shark Fors CoRe
GEN DI2 DI3 COG target depth
1 ** No signal 14,16,17 quiet No signal - Low weak - Low weak No target found
2 ** Very faint signal 16,17,18 medium loud - Low - Low - Low No target found
3 Medium , clean 17,47,50 loud 20,25,30 low 28 mixed 20 low Rusty roof nail 4”
4 Loud, clean 47 very loud 47 high 47 medium 47 high 1 x 3” foil 2”
5 Loud. clean 19,20,28,32 medium loud 20 low 20 low 20 low 1 x 1” foil 2”
6 ** Very faint 14,16 quiet - Low - Low - Low ¼” fine rusty wire <1”
7 Medium, clean 51,58,62,72 medium 58 high 57 medium - Low Small aluminum nail 2 “
8 Medium quiet, clean 12,14,15 medium loud 15 low - Low - Low, quiet Rusty BB <1”
9 Very loud, clean 86,89,92 overload 86,88 high OL 88 high 88 high Matchbox car 1”
10 Loud, clean 60 loud 60 high 60 medium 60 high Modern pull tab ¼”
11 faint 54,55,65 medium 54,55 high - Medium - High Small aluminum nail 3”
12 ** Medium, clean 51,55,60 medium loud 54 high 50 medium 51 high Foil bottle seal 3”
13 Medium, clean 18,19,20 loud 19 low 20 low 20 low 3” rusty nail 3”
14 ** loud, clean 19,20 medium loud 20 low 20 low 20 low ¼” foil ball 3”
15 ** medium, clean 50,53 medium 41,46 high - medium - High Small aluminum nail 4”
16 ** Faint, barely repeatable 35,45 medium 35,43 high - Medium - High Deformed .177 pellet <1”
17 Medium, clean 13,14 medium quiet 18,19 low 17 low 16,17,18 low ¼” chunk of iron 2”
18 Medium, double 17,18 medium quiet 16,18 low 19 low 19 low Same target as #19
19 Loud, clean 20 loud 20 low 20 low 20 low 2” rusty nail 1”
20 Loud, clean 19,20 medium 19,20 low 19 low 19 low ½” heavy duty staple ¼”
21 Loud, clean 19,20 medium 39,45,52 high 22,53,83 broken 20,65,85 mixed Mangled steel ¼”
22 Medium, double 19,20 medium loud, double 19 low 19 low 19 low ½” rusty wire ¼”
23 Medium, clean 18,20 medium 29,32 mix, broken 23 mixed - low Rusty roofing nail 3”
24 Medium, clean 19,20 loud 23 low 20 low 20 low Same target as # 23
25 Medium loud, clean 19,20 loud 20 low 19 low 20 low 2” rusty finishing nail 3”
26 Medium, clean 18 medium quiet 19 low - low 20 low Same target as #25
27 Medium, clean 18,19 medium quiet 19 low - mixed - mixed barbed wire piece 3”
28 Medium, clean 19,20 loud 19 low 20 low 20 low 2” thin rusty wire 2”
29 Medium, clean 19,20 loud, double 20 low, double 20 low 20 low More rusty wire 1”
30 Medium quiet, clean 40,52 medium 42,47 high - medium - high 1” aluminum nail 1”
31 Medium quiet, double 19,20 medium - Low - low - low quiet Very rusty nail 4”
32 Medium loud, clean 19 loud 19 low 19 low 19 low Rusty nail 4”
33 Loud, clean 19 loud 19 low 20 low 19 low Bent rusty nail 3”
** target was not initially located with the Sand Shark
Notes about the information in the table above:
Numbers in the left-most column are identifiers for the targets located. They are listed in the order in which they were
located by the Nokta.
Descriptions in the column under Sand Shark are related to the sound heard when the coil was swept across the
target, both in terms of quality and volume.
Descriptions under the heading GEN are ID numbers displayed followed by the loudness of the sound heard when
sweeping the coil over the target.
Descriptions in the column under the heading DI2 are ID numbers followed by the tone that was audible as the coil
swept over the target.
Descriptions in the column under the heading DI3 are ID numbers (“-“ is no ID displayed) followed by the tone that
was audible as the coil was swept over the target.
Descrptions in the column under the heading COG are ID numbers displayed followed by the tone that was heard as
the coil passed over the target.
Information in the column under the heading Target are brief descriptions of the target found.
Numbers in the right-most column are the depth in inches at which the target was found. These are estimates, as the
ground was very dry sand covered with grass and therefore not easy in which to get exact depths.
Nokta settings for the various modes:
All modes were run at a ground balance of 65 and with the factory standard DD coil
GEN mode Sensitivity 50 ID mask 00 stable and quiet
DI2 mode Sensitivity 50 ID mask 10 chirpy but tolerable
DI3 mode Sensitivity 50 ID mask 00 stable and quiet
COG mode Sensitivity 50 ID mask 06 stable and quiet
The first thing that I note is that not only is Gen mode the most sensitive, it also gives ID numbers the most often compared to the other modes. In fact, for these targets, GEN mode gave ID number information every time. The next best mode for target ID numbers was the DI2 mode. The DI3 and GOG mode were about equal to each other for providing target ID numbers. In terms of target sound, DI2, DI3 and Cog mode all identified target composition well.
Next thing to note is that in factory default, all these targets were located and identified in every mode. In other words, in this test, all targets would have been identified regardless of the mode you happened to be running, under these conditions, with these settings. I think the next time I have a desire to experiment, it will be using the different modes to get deep as possible to see how they compare.
An interesting note was three signal pairs that shared actual targets but appeared as separate targets with both detectors -18/19, 23/24, and 25/26. In all three cases the targets were rusty iron. I am guessing this was a case of halo effects. These targets were within inches of each other. Sorry, I didn’t do a scientific plot of position-would have been interesting but in all three cases, once the target was located and removed, the area of both marked locations was rescanned with the detector and was found to be silent. Also, in all three cases, actual location versus indicated location were different, with the actual location of the target biased towards one indicated location or the other. I suspect this was influenced by the shape of the object, orientation in the soil and differential in degree of corrosion over the surface of the object.
Now to address the missing of targets with the Sand Shark; I was trying to be very thorough with the sweep of the Sand Shark’s round coil but obviously I fell short. Of the seven targets not initially identified with the Sand Shark, only one was not heard when rescanned (target #1). My intention was to overlap coil sweeps by at least 75% so as to maximize my coverage. My understanding of the detection field of this design coil is that 75% overlap is needed to cover about 90% of the maximum depth of the coil. Now, the question this brings to my mind is, if I wasn’t able to do that on a 10 foot square plot, then how could I do it on the beach. It is boggling my mind to think of how much stuff I must have missed! The DD coil of the Nokta has a detection field that runs on the axis heel to toe and about the same depth throughout. This means it scans pretty thoroughly with minimal overlap of sweeps –I try to overlap my sweeps about 20-30%. I am not saying that the Sand Sharks failure to find those targets was its “fault”. I am saying that a round coil requires better technique and greater attention to detail to maximize its coverage, evidently beyond my current abilities.
Another anomaly to be addressed is the lack of a signal for target #1 on the Nokta in DI2 mode. I find it very unusual that there would be a signal in DI3, which is supposed to be slightly less sensitive than DI2. I don’t have any idea the answer to this lack of a signal. I tried a number of times to get it in DI2 mode without success. I probably should have tried again before digging the targets but I did not.
My general impressions are that the Nokta is really a great detector. Very sensitive to very small objects, good depth, excellent ID, and although I still am not comfortable with the use of the DD coil yet, I am really happy with its coverage and depth. It is really nice to have both the audible target information as well as ID numbers. The purists say every target should be dug, and I agree to the merit of that philosophy but sometimes you just want to have the best chance of digging up desirable targets. Let’s face it, park hunting where you are going to dig every target would be better accomplished with a shovel and a screen, in most cases. Also, much as I hate to see it, public areas open to metal detectorists are becoming fewer, and if you want to keep up the hobby, hunting private property will become more necessary. The ability to be selective in your targets will be a good selling point to getting permission to hunt.
I hope this little experiment provides you with some valuable information. I know it did for me!
A plot approximately 10 foot by 10 foot was defined in a back yard setting. The soil had not been disturbed for a minimum of 12 years. The Sand Shark was used to locate targets, which were marked with uninflated balloons. Once all targets were located by the Sand Shark, the Nokta Fors CoRe was used to rescan the plot. New targets that had not been located by the Sand Shark were marked with a different color balloon. The Fors CoRe found 7 targets that had not been located using the Sand Shark. These targets were then rescanned with the Sand Shark to see if they would give a signal. One target did not signal at all, one gave such a faint signal that I would not have dug it, two targets gave very faint but repeatable signals, two gave medium loud signals and one gave a loud signal.
Once I was satisfied that all targets identifiable by these detectors had been found, both detectors were used to rescan the targets and notes were made as to signal sound, loudness, and ID # where applicable. The Sand Shark is a PI detector, thus has only one mode to test. It has a 10 inch round coil and the pulse width was set at the factory default, with the threshold set to a low constant hum. Battery test gave 7 beeps, thus battery strength was good. The Nokta has four modes, and all modes were tested using the same ground balance, factory default settings except for ID mask, which was set at the minimum value that would give a reasonably stable signal. The factory standard DD coil was used. The battery meter indicated full battery power. Headphones were used for both machines. On the Nokta, the GEN mode (all metal) was used to initially locate targets, as this mode is the most sensitive to targets under these conditions, and most comparable to a PI detector.
A note about targets #1 and #2: The first target actually dug was the #2 target, as it had the best signal of the two. I made the assumption that the target must be deep, as the Sand Shark is sensitive to small targets and was having trouble catching this one. I gave up searching for this target in frustration but in looking back at the size of some of the targets that were found, I believe there was a target there but it was very small and got lost in the deep digging. Chalk it up to poor technique on my part. Target #1 may have been the same problem or possibly some mineralization.
My starting premise was that the PI detector would be deeper seeking and that is why I chose to use it to initially locate targets. However, it was quickly evident that the Nokta was deeper and more sensitive under these conditions. After I had located all targets in the search area, I rescanned some of the area with the Nokta in Gen mode and the sensitivity at 90 and quickly had multiple repeatable signals that the Sand shark did not hear at all. Wow! Now I am even more curious how the two detectors compare under the challenging conditions of a saltwater beach.
I am confident that my Nokta is deeper than my Sand Shark on dry land in sandy soil (ground balance 65), so I no longer feel I might be missing out if I park hunt with the Nokta and leave the Sand Shark at home. So now the question is, how do the modes of the Nokta compare to each other?
Sand Shark Fors CoRe
GEN DI2 DI3 COG target depth
1 ** No signal 14,16,17 quiet No signal - Low weak - Low weak No target found
2 ** Very faint signal 16,17,18 medium loud - Low - Low - Low No target found
3 Medium , clean 17,47,50 loud 20,25,30 low 28 mixed 20 low Rusty roof nail 4”
4 Loud, clean 47 very loud 47 high 47 medium 47 high 1 x 3” foil 2”
5 Loud. clean 19,20,28,32 medium loud 20 low 20 low 20 low 1 x 1” foil 2”
6 ** Very faint 14,16 quiet - Low - Low - Low ¼” fine rusty wire <1”
7 Medium, clean 51,58,62,72 medium 58 high 57 medium - Low Small aluminum nail 2 “
8 Medium quiet, clean 12,14,15 medium loud 15 low - Low - Low, quiet Rusty BB <1”
9 Very loud, clean 86,89,92 overload 86,88 high OL 88 high 88 high Matchbox car 1”
10 Loud, clean 60 loud 60 high 60 medium 60 high Modern pull tab ¼”
11 faint 54,55,65 medium 54,55 high - Medium - High Small aluminum nail 3”
12 ** Medium, clean 51,55,60 medium loud 54 high 50 medium 51 high Foil bottle seal 3”
13 Medium, clean 18,19,20 loud 19 low 20 low 20 low 3” rusty nail 3”
14 ** loud, clean 19,20 medium loud 20 low 20 low 20 low ¼” foil ball 3”
15 ** medium, clean 50,53 medium 41,46 high - medium - High Small aluminum nail 4”
16 ** Faint, barely repeatable 35,45 medium 35,43 high - Medium - High Deformed .177 pellet <1”
17 Medium, clean 13,14 medium quiet 18,19 low 17 low 16,17,18 low ¼” chunk of iron 2”
18 Medium, double 17,18 medium quiet 16,18 low 19 low 19 low Same target as #19
19 Loud, clean 20 loud 20 low 20 low 20 low 2” rusty nail 1”
20 Loud, clean 19,20 medium 19,20 low 19 low 19 low ½” heavy duty staple ¼”
21 Loud, clean 19,20 medium 39,45,52 high 22,53,83 broken 20,65,85 mixed Mangled steel ¼”
22 Medium, double 19,20 medium loud, double 19 low 19 low 19 low ½” rusty wire ¼”
23 Medium, clean 18,20 medium 29,32 mix, broken 23 mixed - low Rusty roofing nail 3”
24 Medium, clean 19,20 loud 23 low 20 low 20 low Same target as # 23
25 Medium loud, clean 19,20 loud 20 low 19 low 20 low 2” rusty finishing nail 3”
26 Medium, clean 18 medium quiet 19 low - low 20 low Same target as #25
27 Medium, clean 18,19 medium quiet 19 low - mixed - mixed barbed wire piece 3”
28 Medium, clean 19,20 loud 19 low 20 low 20 low 2” thin rusty wire 2”
29 Medium, clean 19,20 loud, double 20 low, double 20 low 20 low More rusty wire 1”
30 Medium quiet, clean 40,52 medium 42,47 high - medium - high 1” aluminum nail 1”
31 Medium quiet, double 19,20 medium - Low - low - low quiet Very rusty nail 4”
32 Medium loud, clean 19 loud 19 low 19 low 19 low Rusty nail 4”
33 Loud, clean 19 loud 19 low 20 low 19 low Bent rusty nail 3”
** target was not initially located with the Sand Shark
Notes about the information in the table above:
Numbers in the left-most column are identifiers for the targets located. They are listed in the order in which they were
located by the Nokta.
Descriptions in the column under Sand Shark are related to the sound heard when the coil was swept across the
target, both in terms of quality and volume.
Descriptions under the heading GEN are ID numbers displayed followed by the loudness of the sound heard when
sweeping the coil over the target.
Descriptions in the column under the heading DI2 are ID numbers followed by the tone that was audible as the coil
swept over the target.
Descriptions in the column under the heading DI3 are ID numbers (“-“ is no ID displayed) followed by the tone that
was audible as the coil was swept over the target.
Descrptions in the column under the heading COG are ID numbers displayed followed by the tone that was heard as
the coil passed over the target.
Information in the column under the heading Target are brief descriptions of the target found.
Numbers in the right-most column are the depth in inches at which the target was found. These are estimates, as the
ground was very dry sand covered with grass and therefore not easy in which to get exact depths.
Nokta settings for the various modes:
All modes were run at a ground balance of 65 and with the factory standard DD coil
GEN mode Sensitivity 50 ID mask 00 stable and quiet
DI2 mode Sensitivity 50 ID mask 10 chirpy but tolerable
DI3 mode Sensitivity 50 ID mask 00 stable and quiet
COG mode Sensitivity 50 ID mask 06 stable and quiet
The first thing that I note is that not only is Gen mode the most sensitive, it also gives ID numbers the most often compared to the other modes. In fact, for these targets, GEN mode gave ID number information every time. The next best mode for target ID numbers was the DI2 mode. The DI3 and GOG mode were about equal to each other for providing target ID numbers. In terms of target sound, DI2, DI3 and Cog mode all identified target composition well.
Next thing to note is that in factory default, all these targets were located and identified in every mode. In other words, in this test, all targets would have been identified regardless of the mode you happened to be running, under these conditions, with these settings. I think the next time I have a desire to experiment, it will be using the different modes to get deep as possible to see how they compare.
An interesting note was three signal pairs that shared actual targets but appeared as separate targets with both detectors -18/19, 23/24, and 25/26. In all three cases the targets were rusty iron. I am guessing this was a case of halo effects. These targets were within inches of each other. Sorry, I didn’t do a scientific plot of position-would have been interesting but in all three cases, once the target was located and removed, the area of both marked locations was rescanned with the detector and was found to be silent. Also, in all three cases, actual location versus indicated location were different, with the actual location of the target biased towards one indicated location or the other. I suspect this was influenced by the shape of the object, orientation in the soil and differential in degree of corrosion over the surface of the object.
Now to address the missing of targets with the Sand Shark; I was trying to be very thorough with the sweep of the Sand Shark’s round coil but obviously I fell short. Of the seven targets not initially identified with the Sand Shark, only one was not heard when rescanned (target #1). My intention was to overlap coil sweeps by at least 75% so as to maximize my coverage. My understanding of the detection field of this design coil is that 75% overlap is needed to cover about 90% of the maximum depth of the coil. Now, the question this brings to my mind is, if I wasn’t able to do that on a 10 foot square plot, then how could I do it on the beach. It is boggling my mind to think of how much stuff I must have missed! The DD coil of the Nokta has a detection field that runs on the axis heel to toe and about the same depth throughout. This means it scans pretty thoroughly with minimal overlap of sweeps –I try to overlap my sweeps about 20-30%. I am not saying that the Sand Sharks failure to find those targets was its “fault”. I am saying that a round coil requires better technique and greater attention to detail to maximize its coverage, evidently beyond my current abilities.
Another anomaly to be addressed is the lack of a signal for target #1 on the Nokta in DI2 mode. I find it very unusual that there would be a signal in DI3, which is supposed to be slightly less sensitive than DI2. I don’t have any idea the answer to this lack of a signal. I tried a number of times to get it in DI2 mode without success. I probably should have tried again before digging the targets but I did not.
My general impressions are that the Nokta is really a great detector. Very sensitive to very small objects, good depth, excellent ID, and although I still am not comfortable with the use of the DD coil yet, I am really happy with its coverage and depth. It is really nice to have both the audible target information as well as ID numbers. The purists say every target should be dug, and I agree to the merit of that philosophy but sometimes you just want to have the best chance of digging up desirable targets. Let’s face it, park hunting where you are going to dig every target would be better accomplished with a shovel and a screen, in most cases. Also, much as I hate to see it, public areas open to metal detectorists are becoming fewer, and if you want to keep up the hobby, hunting private property will become more necessary. The ability to be selective in your targets will be a good selling point to getting permission to hunt.
I hope this little experiment provides you with some valuable information. I know it did for me!
. I'm hoping that I can find stuff that I missed, and hopefully deeper. But running the Fors Core in GEN mode is a beast! Lol
I hope you saw my humor. I have been so impressed with the Fors CoRe and especially in GEN mode, even with the stock coil, it is easily the BEST detector I have ever used to date in the depth and information department. Even my CW hunting buddies were very impressed with what I was pulling out of the ground with the CoRe, as I would often follow behind them and get what they missed!