Loss of depth by using discrimination

[mts]

So I was doing some air tests with my Tesoro Silver µMax and noticed that the depth capability decreases as I raise the discrimination level.
There is about a one inch difference between no discrimination and full discrimination. I realize that air tests are not necessarily indicative of what you get out in the field but it got me to thinking. Basically, there could be situations in which the discrimination control would give you false information due to this phenomenon. Imagine a quarter sitting just at the threshold of the detection range. With the discrimination set at a normal hunting level (below nickels) I would pick up the signal. But as I rotate my discrimination control toward silver coins, the depth capability of the machine may decrease at a point to where the quarter could no longer be detected. Yet the discrimination control would not have gotten to the silver coin range. This would make me think that the coin was a penny or even a pulltab.

I tested my Vaquero and my BH Tracker IV and they don't suffer from this problem. Is this a common problem/behavior for beep and dig machines? I don't see this mentioned very often.

 

[mts]

Concerning the Silver u/Max 1" dime air test at max, this setting would likely only be used by people detecting new parks trying to get the most $$ quickly.

I was wondering what the Silver u/max air tests at on a dime when disc is set just high enough to reject pulltabs? Or high enough to reject zincs?

I had a Tesoro Bandido II u/max & set it to reject pulltabs to detect a park. I was using the 10x12 concentric coil. 3" deep dimes gave a broken sound. When I turned the disc down to just reject iron & planted a nickel 6" deep, it got it with a solid & pretty loud beep. My ground has moderate iron & hot rocks.

Some of the better newer designs won't lose any depth when rejecting pulltabs, in an air test. The Silver u/max gets pretty good in ground depth for the price, as long as disc is low. If you want deep silver dimes while rejecting pulltabs, it looks like a different detector would be needed.

I recently obtained a Garrett AT Pro & it air tests 9.5" on dime, solid beep, high tone, with tabs notched out ($595 new MAP price). I had a Fisher F5 ($499 new MAP price) air tested 8.5" on dime w/pulltabs & below rejected. Best wishes & HH, George (MN)

Thanks for the in-depth response George. Here is a chart with air test depths on a dime for the Silver µMax at the marked notches on the discrimination dial.

Silver µMax dime air test:
None: 7"
Iron: 7"
Foil: 7"
5¢: 7"
Tab: 6.5"
1¢ Zn: 6"
Max: 1"

As you can see it does pretty good up to the 1¢ Zn setting. After that it hits a point where it rolls off exponentially to 1". This point is around the midpoint between 1¢ Zn and Max.

I disagree that this setting would likely only be used by people detecting new parks trying to get the most $$ quickly (although that could definitely be the case). This setting is also useful for people like me who like to thumb the disc knob as a form of manual target ID. I normally hunt with discrimination set just above the foil mark on the dial. When I get a hit, I thumb the disc knob up toward max sensitivity to determine what type of target it is. It should be clear that in the past my detector was not giving me the full story on silver/clad dimes. These would likely have sounded instead like zinc pennies. Whether or not I would have dug those signals is another matter which was likely dependent upon my mood at the time.

The important take away from all of this is that it is imperative to know your detector. It would be very easy for someone in a trashy park to turn their discrimination up to max in an attempt to cherry pick as much silver as possible. With some detectors this might work very well. But with the Silver µMax, this would end in disaster.

I now know how to handle this issue: do not turn the discrimination knob up past the 1¢ Zn setting. But I don't think this is intuitive. Especially for new users that may not even understand how discrimination works in the first place. In fact, it makes you wonder why Tesoro didn't just cut the knob off at this point anyway. It's sort of like the whole "my amp's volume control goes to 11" gag. What's the point of higher discrimination setting if it isn't really that usable anyway?