Threshold Challenge

[Gaz]

....I checked my threshold today out of interest when I did the ETrac/XTerra video. My ears must be better than I thought as I could just here it on a setting of 2.......

Gaz.

 

[S505]

Actually, I was hoping for more suggestions that I should try to demonstrate some of these other uses for threshold but I agree with everything you say Digger. I have not looked at threshold or any other function on the 505 with the intent of comparing it to any other model and I understand the 505 does not have the capabilities of the 705, but the threshold sections in the manuals read very similar, implying they work similarly. The variables you bring up are of huge importance when trying to duplicate anything but I can only work with what I have. This is why it is more meaningful if someone who has actually experienced a specific behavior be the one to duplicate it. They have the equipment, know the settings, conditions, targets etc and have a much better chance of success. Even if you or Turnmaster duplicated what you describe and posted the exact settings, I still may not be able to duplicate it, but you would have given me a very good starting point to look. If I can reproduce it, then I have learned much more rapidly than I would by reading the manual and attempting with only the manual's guidance. If I am unable to reproduce it, it means absolutely nothing other than my detector may not be capable in my conditions. Chances are good though that there are others out there who have your coil, detector, etc and they will be able to duplicate it and use it to their benefit. So far that is a moot point because no one has posted that they can reproduce size discrimination using threshold. I am not saying it does not work but so far it looks to be so transient that it may as well not exist for me or anyone else.

Hey Gaz, enjoyed your video. Thanks for posting it.

Cheers,
S505

 

[Heelgrasper]

I don't know that Heelgrasper even has an X-TERRA as the post he made in this string is the only post he has made on Findmall.

I could have mentioned it but I figured it was implied: I use an X-Terra 70, mostly with the elliptical 18.75 kHz coil. As the 70 and the 705 are very popular here in Denmark the best use of the machine has often been talked about in the Danish forums but I've never heard anyone mention that you would miss targets by having the threshold simply put on 0 (no tone).

Recently for instance there was a coin fragment uploaded to one of the forums, found with the 70 with the elliptical 18.75 kHz coil with threshold of 0 (would had been said if it was anything different). The fragment weighed in at 0.06-0.07 grams, less than 1/10 of that 3 cent. The main interest here (when it comes to coins) is to find coins with a weigth around 1 gram and very often cut in half or quarters. For certain periods the coins even go as low as 0.2-0.5 gram.

So I find it a bit strange if no one here had figured out that you should put your threshold up at for instance 5 not to miss the small targets.

 

[Digger]

Thanks for your comments, and welcome to the X-TERRA forum. I am always interested in what folks from other parts of the World are finding with their X-TERRAs. Especially those areas with the smaller silver coins and partial coins. Thanks again for posting. HH Randy

 

[argyle]

Coinhunters never really did understand the true use of a threshold.

It's use is for listening for a very slight dropout of threshold. Those are the true deep targets. That's the reason threshold was put into detectors. For a rise and drop. A rise without signal is a target not quite as deep as the dropout. Set too high you won't hear the variation, set too low you won't hear the variation.
You can find the correct threshold setting by using one of the only two reasons you should do an air test, which are threshold and headhone range.

 

[argyle]

So we can stop beating this dead horse called threshold I propose someone demonstrate the X-terra's threshold doing something other than turning off when a target is detected. Our goal should keep the following passage from the X-terra 305/505 manual in mind.

"The Threshold volume should be set to the
preferred level. It is important to note that
small surface objects, as well as large deep
objects, will produce very small changes in the
Threshold sound. It is therefore important to
set the Threshold control correctly to ensure
that these targets are heard."

Here are a couple ideas but feel free to come up with your own: show threshold change in pitch or volume just by passing your coil over a target. Show a target's audible beep change in some way (eg. volume, beep's presence/absence) just by changing the threshold setting.

Here is the rule:

1. Your demonstration must be reproducible. This means you must be able to do it at will and you must be able to clearly explain to the rest of us how we can reproduce your demonstration. This includes all detector settings, target id, target depth, ground matrix type / or in air, etc.

For the record, I think the manual is worded poorly and misleads as a result but there are users who claim threshold does as advertised. I also like my 505 and this is not an attempt to bash this detector or any other. I (and I think all of us) want to be sure targets are not being missed because threshold is set wrong. So, if you know how to make threshold work, do us all a favor and demonstrate it!

Cheers,

S505

Firstly we all should get one point straight, there is no such thing as a negative or positive threshold. There is only low to high threshold.

The explanation on the threshold and it's purpose in the 305-505's manual, while sounding like an explanation from one of Minelab's gold VLF's from 20 years ago, is actually quite accurate.
Very small close to the surface targets, and deep larger signals, do make a change in the XTerra threshold. And not just in the quick threshold-blank-signal-blank-threshold when in notching.
If you run in all metal, with the correct threshold level set, (The Dane was close but a touch low), a very small mid to surface target, or a larger (coin size and up) deeper target than the unit will produce a signal with, will produce a very quick and repeatable Click/Spasm. You have to be within 2 steps either side of the correct ground balance to hear it.
It comes in load and clear, but much better on two of our coils.

Notching on all three units, or Auto and tracking balance on the 705 will not allow the sound to be heard. To notch will produce a cover, and auto will smother.

You need amplification to hear it, and with any threshold based unit you should be running an amp anyway. Two makes of amps in-particular are a brilliant match.
While Minelab placed the threshold on the XTerra's for the purpose of utilizing a dropout of notched out targets, it can still serve another purpose. You just got to make it work for you.

If anyone has even gleaned a smidgen of info from those few paragraphs, could you do me a couple of favours.

First: Stop making out the XTerra's to come across as some sort of crazy like FBS unit with too much technical and theoretical mumbo jumbo about them. They are so simple to master, and the purist form of single frequency (they were made to match the 7.5khz, the other two frequency's were afterthought's) discriminating VLF made to date, and new users thinking of buying them are being put off, thinking a masters degree is required to operate them.

Second: For godsakes stop whining about the coil selection. We have 2x 6"coils in an 18.75khz DD and a 7.5khz concentric. 3x 9" concentrics in 3khz 7.5khz and 18.75khz. 1x 10" DD elliptical in 18.75khz. 2x 10.5" DD in 7.5khz and 18.75khz, plus an excellent 14.5" DD round in the 7.5 frequency.

Besides.... There is a new coil coming out. They already have the size and specs.
Soooo....you better not laugh, you better not cry, you better not doubt cause I'm telling you why ...Santa Clause is a come come coming to town.

 

[Digger]

Firstly we all should get one point straight, there is no such thing as a negative or positive threshold. There is only low to high threshold.

But there are negative and positive Threshold values.....
[attachment 244827 threshold7050001-Copy.jpg]

 

[argyle]

Hi Randy. How have you been keeping.

Yes, and you are quite correct. In the world of our digital incretment XTerra's, we see a - negative value for the less than audible setting from O to below. We also see where the 0 setting is said to have "disabled" the threshold. A misuse of a word, as the threshold sound merely kicks in at the next incretment.
On the older threshold based units, we heard the same thing happen in the same range. In the main they would not kick in till the knob was at 1/3rd turn. They correspond directly to what they have done with the digital settings, ie: one increase or decrease is the same as a slight turn lower or higher.
They have to use the terms negative/positive threshold simply because of the digital control aspects of the units, but they still mention low/high threshold.

A small example of how new terms can make it confusing. It brings it too close to a true term, like negative/positive ground balance.
But, there will only ever be low to high threshold.

Personally I've always liked the Minelab manuals. They've been quick, clear and precise. A few funny and misleading pics here and there, but in the main very good.

Now I'm trying to decide if I have made a negative/positive post, or a low/high one.