Mixed Mode

[kac]

In a mixed mode do you lose the slight edge in depth that you normally get in AM mode or does it depend on the detector?

On my Tejon even though it is analog, if I set disc 1 to AM and disc 2 for disc mode (clicked out of AM mode) I can hear a faint target but if i toggle to disc2 that sound will be trimmed out even if it is in the metal response range but happens to be on the fringe.

Lastly how accurate would that VID be if in AM mode? I am assuming there would be some sort of filtering for the digital signal processor to be able to display the correct vid based on target response?

[Chase Goldman]

13 hours ago, kac said:

In a mixed mode do you lose the slight edge in depth that you normally get in AM mode or does it depend on the detector?

I think it does depend on the detector.  I think in the pure audio mixed mode implementations that Mike was referring to as the more traditional mixed mode implementation, you do no lose anything.  AM on the F75 is AM and the AM audio is unaffected even though you do get a visual target ID.   The issue arises regarding whether the detector in "All Metal" is truly giving a raw, unfiltered all metal audio signal or simply processed audio but devoid of any "discrimination" filtering.  In other words, no discrimination "pseudo All Metal" does not necessarily equate to "true All Metal" where no signal processing/filtering is occurring.  In the former, even though there is no discrimination filtering occurring, there may be other signal processing/filtering going on.  I think the Equinox is a good example of this as well as the Deus, where a true all metal audio output is more a voltage controlled oscillator (VCO) audio that is proportional to signal strength (volume) and phase shift (pitch) of the target signal.  The Equinox does not do this when all discrimination is removed (even in the pseudo VCO audio of gold mode) and with the Deus, even though a VCO output is provided in Gold Field mode (perhaps the closest thing on the Deus to true all metal) the signal is still processed through various signal processing filters.

[GB_Amateur]

1 hour ago, Chase Goldman said:

In other words, no discrimination "pseudo All Metal" does not necessarily equate to "true All Metal" where no signal processing/filtering is occurring.  In the former, even though there is no discrimination filtering occurring, there may be other signal processing/filtering going on.

Filtering is something I, for one, am confused about.  Take the Fisher F75.  There are two "all metal" modes:  motion and non-motion.  From my understanding, non-motion mode is used by many detectors when they are put in pinpoint mode.  On the F75, the detector's sensitivity (and I prefer to use this term as a result or consequence as opposed to a control, i.e. 'gain') is stronger when in non-motion.  Does this mean that motion all metal mode is actually resulting from some filtering?

[Chase Goldman]

24 minutes ago, GB_Amateur said:

Filtering is something I, for one, am confused about.  Take the Fisher F75.  There are two "all metal" modes:  motion and non-motion.  From my understanding, non-motion mode is used by many detectors when they are put in pinpoint mode.  On the F75, the detector's sensitivity (and I prefer to use this term as a result or consequence as opposed to a control, i.e. 'gain') is stronger when in non-motion.  Does this mean that motion all metal mode is actually resulting from some filtering?

That is a good question.  The "auto-tune" feature that enables a detector to not have to be constantly retuned is a convenience feature that resulted in the boon of motion based induction balance detectors in the 80's.  Detectorists were enamored with not having to futz with re-tuning their detectors to provide the ideal threshold level which was easily thrown off by various things including drift in the detector circuitry to changing the height of the coil above the ground or changes in ground characteristics.  This ultimately resulted in silent sweep detectors where the threshold was eliminated completely.  The problem with auto tune was that the coil DID have to remain in continuous motion in order to hear the target otherwise the auto tune circuit would cancel out the target signal.  Having a true threashold and non-motion detection without the benefit of autotuning results in the most sensitive detector overall.  So the autotune circuit does tend to reduce sensitivity because it manipulates the output requiring swing motion vs. a true all metal, non-motion mode, but not because signal processing filtering is going on, in the strictest sense of what "filtering" means.

Steve's article on Threshold Autotune, Sat, and V/Sat explains the background on how induction balance detectors evolved from primarily non-motion mode to motion mode, a lot better than I did here.

[GB_Amateur]

Thanks for that explanation and double thanks for linking to Steve's excellent article (original from 2010?).  Even though I had read it before I had forgotten about it AND it hadn't really sunk in.  Both are common for me these days.  🙄