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Nokta Explanation Of Impact Gen(d) And Sta(d) All Metal Modes


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There is a previous thread with a lot of speculation about just what is going on with a couple of the Nokta Impact all metal modes, the Gen(D) and Sta(D) modes. The thought was that they are mixed modes - in other words modes that are running both all metal and disc in parallel.

The speculation garnered attention and we have now been provided this explanation directly from Nokta Software Team Leader Alper Tozan regarding these 2 modes: 

''I read a lot of comments about Gen (D) and STA (D) modes in some forums and firstly, I want to thank you about all your positive thoughts. On the other hand, I want to clarify one thing. In some forum discussions, these modes are defined as ‘’mix modes’’. These modes are not mix modes as mix modes typically result from at least two different software algorithms or hardware circuits working at the same time for decision making to discriminate and detect metals. These mix modes also show characteristics of two or more different modes at the same time including handicaps of each signal processing. 

Gen (D) mode, on the other hand, is a true threshold based all metal mode with motion that can discriminate metal without needing any other hardware or higher order software process level. So it always behaves like a classical true threshold based all metal mode but with iron tone and tone break.''

Frankly, for me that raises almost as many questions as it answers. Is an all metal mode that discriminates an all metal mode? Is it not instead a different kind of ferrous/non-ferrous discrimination mode? Whatever it is, it is unique, and that's enough for me! So I will do what I normally do and ignore what is going on under the hood and pay attention to just what it is these modes actually achieve by way of useful results in the field. More on that at a later date.

From Nokta Impact Owners Manual, pages 12-13:

Static Mode (STA)

This is a non-motion mode. In other words, the device will generate an audio response when you hold the coil stationary without swinging over the target. The audio response increases in volume as the coil approaches the target. This mode is recommended for larger and deeper metals.

In the STA mode, the device will generate the same audio tone for all metals and it will display the target ID on screen. At the same time, the ID scale will fill up to the right in proportion to the signal strength.

Target ID range is 00-99. 00-40 are ferrous and 41-99 are non-ferrous metals. You can discriminate out all IDs below a certain ID by using the Disc. setting and simply avoid these metals in the field.

When the device detects a discriminated metal, it will not produce an audio response or an ID. However, the ID scale will fill up to the right in proportion to the signal strength.

The threshold in this mode is internal and cannot be adjusted by the user. Changes in the ground and temperature may lead to drifts in the threshold. Threshold drifts will be reflected in the ID scale either in the positive way (right side) or the negative way (left side). The device may emit an audible response in the positive drifts but not in the negative ones. When the threshold drifts, pull the trigger once to retune the detector. Retuning periodically while searching in this mode is recommended.

IMPORTANT! For a more stable operation, try keeping the coil consistently at the same height above the ground where you retuned the detector.

IMPORTANT! If you retune the detector over a target, the threshold will drift to the negative side and the device will no longer detect the target until the detector is retuned. In addition, the depth of the detector will also decrease.

If the drifts are substantial and retuning does not improve the situation, increase the iSAT setting in the Expert Settings to a level where the drifts are eliminated (for detailed information on iSAT please refer to page 24). As the iSAT is increased, the device may detect weaker signals but will not be able to detect the targets anymore if you hold the coil stationary or sweep back and forth over the target. If the drifts still continue frequently, drop the gain to 39, decrease the iSAT and re-ground balance.

Static Delta Mode (STA (D))

In principle, it works the same as the static mode. The difference is that the static delta mode will generate the same tone for ferrous and non-ferrous targets at fringe depths but it will discriminate the shallow ferrous targets by emitting a low iron tone. Also, Disc. setting is not available in this mode.

Please refer to Table 2 at the end of the manual for different settings used in STA and STA (D) modes.

General Search (GEN)

Different than the other modes, this mode features a threshold tone which is continuously heard in the background.

General Search (GEN) mode is used in 2 different ways in the IMPACT: 1) with the Disc. setting disabled at 0 2) with Disc. enabled (non-zero). When the device is first turned on, Disc. setting will be off. When the Disc. is set at 0, the device does not discriminate targets and detects all targets (metals, mineralized rocks etc.). ID of the detected target is shown on the display (except for negative hot rocks) and the same audio tone is provided for all targets. The audio tone increases in pitch as the coil approaches the target. This is the typical All Metal mode found in most detectors.

When using the Disc. Setting in this mode, the device will emit a low ferrous tone for all targets below the Disc. Setting, and a higher tone for all targets above the Disc. setting which changes in pitch as the coil approaches the target. Let's say you set the Disc. to 20. The device will generate a low iron tone for all metals with 0-20 ID and a higher tone for all targets with 21-99 ID. Upon target detection, the threshold will momentarily go silent and only the target audio response will be heard. The duration of the threshold's silence is directly related to the level of the iSAT.

Gain, threshold and iSAT settings in this mode are optimized to provide the best performance on different terrains. You can modify these settings based on ground conditions.

We recommend using the GEN mode when discrimination is not important and not using it in heavy trash areas or areas containing many hot rocks.

Audio Boost in the General Search Mode
This feature is not included in the settings on screen.
Boosts the sound of weak signals received from small or deep targets making it easier for you to detect those uncertain targets. It is recommended that audio boost should be used on a temporary or as-needed basis because it will not only boost the target signal audio but it will also boost the volume of ground noise and false signals along with the threshold hum.

Audio Boost consists of 5 levels (b1-b5). At start up, the Audio Boost level is set to low (b1). To increase the Audio Boost level, pull the trigger and press the minus (-) button simultaneously. Audio Boost will only work in the GEN mode.

General Search Delta (GEN (D))

In principle, it works the same as GEN mode. The difference is that the Gen (D) mode will generate the same tone for ferrous and non-ferrous targets at fringe depths but it will discriminate the shallow ferrous targets by emitting a low iron tone. 

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Steve, do you ever sleep? Really don't know where you find the time to write such detailed posts on a regular basis.

Using the Impact at the beach, I was easily able to identify rusty bottle caps in Gen D mode, just going by the sound. Very cool hunting this way, like gold prospecting on white sand :biggrin: Some of the deeper and smaller targets would only produce the faintest of threshold changes, so would definitely recommend headphones. 

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