King Cobra PCB

[ivconic]

ok guys, let me know which detector has a "very low air test performance" and i will buy it!... and set it aside in test with the ones that i have Troy x3, Golden Mask 5, Aka Signum and i consider buying a Deus now. I want to find a detector that has really low air test performance and great soil depth detection. My soil is pretty much as Serbian (i live just across Danube river 100 km from Serbia, as well not that far from Bulgaria). Ground is really highly mineralized and difficult to detect...but differs.
So i want to buy it at put it to some tests with the ones above...
best regards

I don't think that you will find such detector!
What a coincidence; before i bought Deus i had and used Troy Shadow X5 for quite some time!
Are we true neighbors or what!
I guess i will be damn annoying to say this; but i remember my last Fisher 1265 (had few of those) was pretty disappointing in air tests... while it positively surprises me each time on the soil!
XP Deus will detect single coin in air from 35 to 44cm (smaller 22.5cm coil). I tested it few times on 1e coin. But i really don't remember right now the distance.
And i don't want to be again accused as being liar by some pathetic miserable idiot who randomly stumbled here on forum. I'll just say "from 35 to 44cm".
Point is that same coin will be detected in soil at significantly lower depth than that. Nothing to be surprised about. It's the common case at all similar detectors.
But there is also interesting fact to be at consideration; detectors with better balanced coils will show less difference between distances in air and soil.

[steaua581]

ok guys, let me know which detector has a "very low air test performance" and i will buy it!... and set it aside in test with the ones that i have Troy x3, Golden Mask 5, Aka Signum and i consider buying a Deus now. I want to find a detector that has really low air test performance and great soil depth detection. My soil is pretty much as Serbian (i live just across Danube river 100 km from Serbia, as well not that far from Bulgaria). Ground is really highly mineralized and difficult to detect...but differs.
So i want to buy it at put it to some tests with the ones above...

best regards

[Artyom]

A greater range in the air is possible in consequence of the phase shift toward the copper. But if in the instrument the scale of metals is not shifted and the coil is correctly balanced, then there is no overcompensation.

[ivconic]

Hi Ivica..

its really confusing this "capitol" of AIR TESTING and ground detection. Now if a detector detects in air a coin at 10 cm in ground it will detect it at 40 cm? And what is the basis of that?
It seems that all detectors that do well in air do well in ground as well unless there is mineralization which does not let us increase sensitivity, gain to maximum.
If so then how can we test a detector to get its true capabilities? if not by air testing?
What i understand is that magnetic field is really important and how its "concentrated in front of that coil..
perhaps is there a detector that has such low air detection and then does such great ground detection? then we shall test it and see whats going on...
all this is very confusing...
PS: now i regret i have dismantled a Radio Shack metal detector i had bought long ago which had an air test for a coin at 5 cm maximum 10 cm ... i remember i tried detecting my car and could not pick it up at more then 20 cm...whats going on?

Usually it is problem related to residual offsets.
Residual voltage left after balancing on RX side and RX front end internal hum.
I suspect that coil is not balanced well because there is certain "echoing" in detector response after some distance.

[steaua581]

No, like i said it's bad coil balance. "Overbalanced" coil.
Your analogy is not true, it does not apply in this case.
It's the "air" signal that causes such "detections".

Hi Ivica..

its really confusing this "capitol" of AIR TESTING and ground detection. Now if a detector detects in air a coin at 10 cm in ground it will detect it at 40 cm? And what is the basis of that?
It seems that all detectors that do well in air do well in ground as well unless there is mineralization which does not let us increase sensitivity, gain to maximum.
If so then how can we test a detector to get its true capabilities? if not by air testing?
What i understand is that magnetic field is really important and how its "concentrated in front of that coil..

perhaps is there a detector that has such low air detection and then does such great ground detection? then we shall test it and see whats going on...

all this is very confusing...

PS: now i regret i have dismantled a Radio Shack metal detector i had bought long ago which had an air test for a coin at 5 cm maximum 10 cm ... i remember i tried detecting my car and could not pick it up at more then 20 cm...whats going on?

[ivconic]

Yes, but when its 1/3 more in air then it should be 1/3 more in soil too.
I mean the TGSL can do 35 cm in air, but this detector does 50cm.
Whats the difference? Is it just a better coil?

No, like i said it's bad coil balance. "Overbalanced" coil.
Your analogy is not true, it does not apply in this case.
It's the "air" signal that causes such "detections".

[BKY1337]

Yes, but when its 1/3 more in air then it should be 1/3 more in soil too.
I mean the TGSL can do 35 cm in air, but this detector does 50cm.
Whats the difference? Is it just a better coil?

[ivconic]

Is this the King Cobra? https://www.youtube.com/watch?v=emDkCWHaUSM

I think i can never reach 50cm with a euro coin with my TGSL.

It is only the "air response" not real detection. It will not perform well on targets in soil.
It will hardly achieve 1/3 of such "depths" in soil.
I guess that's the "phase" we all were passed through in our works.
I was also delighted to see such "depths" in air once in the past, when i started with building the detectors.
The moment you take it outdoor on real soil; you'll realize the bitter reality!

[Nandor]

It's not the King Cobra. It's a Hungarian made metal detector, there is a guy at Budapest who makes them. Search for "Cobra fémkereső"

[BKY1337]

Is this the King Cobra? https://www.youtube.com/watch?v=emDkCWHaUSM

I think i can never reach 50cm with a euro coin with my TGSL.

[kt315]

guys, this is a money from Egypt i did bring up.

http://ipic.su/img/img7/fs/CIMG6047.1490464315.jpg

Egypt friends must be enjoyed.

[kt315]

thank you for new wave of interest to GMT. i still have 5pcs board from batch ready to send.

[BKY1337]

Ah ok , thanks!

[kt315]

gmt has two tones and notch filter. left is same.

[ivconic]

Why has the GMT a higher depht as the TGSL EDU?
--
i never said it. really i do not know how depth on tgsl. if you see same generator tx, same current in coil,
same coil, same opamp, same filters, thats mean something has one circuit, for me.
ivcinic began to do tgsl just see i began to share info on gmt while gmt COVERS all tesoro similar schematics.

Correct!
There is no significant differences between circuits. Both should be close in depths too.
Smaller differences in depths could be related only on size of a coils used.
GMT seems a bit refined design than TGSL.
Despite the fact that TGSL is my "baby"; i would rather vote for GMT, because it looks more interesting to build.