Gamma all metal vs discrimination mode

[steve1357]

I have the Gamma as well as other detectors. I thought the Gamma would have more depth in all metal mode vs discriminate mode as other detectors but I haven't been able to notice any difference in air tests or the test garden. Tried different number of tones also.

Did I miss something?

 

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[steve1357]

Surely I'm not the only one with a Gamma.

And don't call me Shirley.

 

[Ausgoldhunter]

The Gamma in All Metals does actually get more depth, the key is threshold.. You won't get a beep, just a twitch in threshold...

 

[steve1357]

Can you elaborate?

I see no difference in depth between the two modes, all the other detectors I own go 30-40% deeper in all metal compared to disc mode.

 

[ToddB64]

Hi Steve

There are many factors that determine depth and I will try to address a few of them. I am by no means an expert on metal detector circuitry and all the nuances involved. I'm just going on memory of what I've read and hope this might help.

Something to keep in mind though is that all modes of the Gamma 6000 share the same Sensitivity setting. This is confirmed in the Manual, last paragraph, bottom of page 11. If we take this paragraph literally, that would mean Discriminate, Pinpoint, All Metals and Ground Grab mode. So unless you would change the Sens. setting each and every time you change modes, the Sens. will stay either on the default or on the last setting you made, and this could alter depth test results, i.e. keeping the depth in All Metal the same as in Discrimination mode, all other factors being kept the same between tests.

The Sensitivity setting is largely responsible for the visual and audible reporting ability of a metal detector. In addition, we know that the metallic ingredients and siize of a target (or the amount of surface available for eddy current production) is another important factor. Unless you know ahead of time that the ground beneath your coil is highly mineralized and have ground balanced and set your detector appropriately, it's best to start with Sensitivity set at maximum and then if you are getting erratic beeps, due to high mineralization, EMI interference, or both, lower the Sensitivity until the detector settles down.

We know that, as Sensitivity is increased toward the higher end of it's range, a metal detector must deal with the response from ground minerals as it tries to separate these from target response. It doesn't just punch through the mineralization.

Maybe Dave Johnson will drop by and contribute more.

ToddB64

 

[steve1357]

Thanks Todd

But all of my other Fisher detectors, let's say the F5. Set the sens at 50% or max, doesn't matter, the all metal mode or auto tune whatever it's called, will find targets significantly deeper than your best efforts in discrimination mode. Where a quarter in discrimination mode is 7 inches max, switch to no discrimination and you might get 11-12 inches running single tone.

Dave says no discrimination goes deeper.

http://fisherlab.com/hobby/davejohnson/sensitivity and depth.htm

I tried again, I just can't get any more depth with no discrimination on my Gamma. It's like the discrimination mode doesn't disengage when I switch to all metal single tone.

 

[ToddB64]

Thanks Todd

But all of my other Fisher detectors, let's say the F5. Set the sens at 50% or max, doesn't matter, the all metal mode or auto tune whatever it's called, will find targets significantly deeper than your best efforts in discrimination mode. Where a quarter in discrimination mode is 7 inches max, switch to no discrimination and you might get 11-12 inches running single tone.

Dave says no discrimination goes deeper.

Discrimination mode “Sensitivity” and “Depth”

I tried again, I just can't get any more depth with no discrimination on my Gamma. It's like the discrimination mode doesn't disengage when I switch to all metal single tone.

Steve......First I want to thank you for the Dave Johnson essay hyperlinked in your post. Great information ! I copied that to my computer documents file for reference.

Well, after carefully reading Dave's essay, it does appear that he is saying AM goes deeper than Disc. mode, so your opening post raises a good question.

Perhaps, as Ausgoldhunter says in post #3, "the key is threshold", but I don't recall the Gamma manual referring to "Threshold" perse. Maybe one of the TONES or VOLUME settings, on page 14 of the Manual, would be related to Threshold.

The other possibility is that your machine is somehow malfunctioning and needs factory repair.

Maybe a phone call to Teknetics and discussion with Dave J. would be the quickest way to settle your issue.

Good luck !

ToddB64

 

[steve1357]

Thanks Todd

Fisher has a lot of Dave's papers

http://fisherlab.com/hobby/dave-johnson-essays.htm

 

[liftloop]

it said in the link above how fisher and first Texas instrument go hand and hand together

 

[vet67coupe]

Well what was it....lol....thinking on getting the gamma....BiLL

 

[Massieville Mike]

Mine seems to be more sensitive/deeper in all metal mode, by a pretty good margin. When preparing to ground balance my gamma, I normally scan for "clean" dirt/ground in disc mode. When I find a "clean" spot, I check that spot again in AM mode. Quite often there is metal there that was not "seen" by my gamma in disc mode. This would be may main basis for saying mine seems to be quite noticeably deeper in AM mode. I do sometimes hunt in AM mode, but not often as my gamma seems to be plenty sensitive enough in disc mode for the hunting I do.

 

[supertraq]

remove,double post

 

[supertraq]

Just ran mine over a buried silver $1.00 and in all metal and disc where the same,no difference but the depth is deep enough either way. 12.5" is all i want to dig.