AKA Metal Detector,Anyone Using One

[jimz49]

I think the ability to adjust the sorex for any condition that I might encounter. But that has also been the slowest to get my head around. Fortunately there is another forum on the net that has a wealth of freely shared information. Although I'm new to the AKA brand, I'm determined to keep at it until it all starts to click.

 

[After-1-]

From what I think I understand is that setting the GB is very important with the AKA machines,it means a lot with my other detectors, but more so with the AKA!!!!!! Like any detector with a lot of adjustment on settings, you need to put the time in and remember what you do. My thoughts.------------after1------------------

 

[Sven]

Just give it time, they operate a bit different than what your used to. Kind of like switching from a VLF to a PI machine, you have to relearn how this type of detector operates and the controls interact with each other.
Once it starts to click................worth the time and effort to become proficient.

 

[azsh07]

Let me very clear on the importance of a proper GB, Please please read this and understand it completely. This is the single most important step to the detector....PERIOD>!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Understand this first fact...the GB DIRECTLY AFFECTS the accuracy of the VDI. Get the GB offset wrong and you WILL LOSE SILVER...PERIOD...NO EXCEPTIONS.

O.K...so you got that last sentence so here is why.

Now I forgot some of the deep details on exactly what all goes on but it is not necessary to know all the physics. But when we GB the machine it also sets the lookup table so to speak for proper VDI angle at that respective GB offsett. The detector...like many is set or calibrated to ferrite. Any GB offset from that will affect VDI accuracy directly proportional to the degree the GB is off and not corrected.

Say...what....? Simple....if the current ground signal would GB at a specific value but your machine is GB at say a value 6 degrees off then your VDI will be off by exactly 6. Which way it is off depends on whether you are positive or negative off from a neutral GB. The detector takes into consideration the influence of the ground minerals effect on the signal VDI and compensates accordingly and corrects the VDI. But...you have to GB the machine properly or you will screw it up...royally. You won't ruin anything as you just have to GB again but you may not know it until you wonder why no silver targets.

So I tell EVERYONE to take a quarter with you and after you GB toss it on the ground and make sure it reads 80-82. Now the frequency of the coil will affect the VDI slightly with a 14 KHZ coil reading about 2-4 lower VDI...this IS NORMAL.

If you set your GB offset positive then the VDI moves positive....set the GB offset negative and the VDI moves negative and it is almost a 1 degree GB to one VDI angle correlation.

If you set your GB too negative you will pull hotrocks back from -90 into the high 88 range and get falsing.

Remember the VDI wraps...if you do not knopw this. After +90 it wraps over to -90...so a target that would normally read say +86 like large silver will wrap over into -88 if you positive offset by +6 since you pushed the VDI above 90 and it wraps over into now the - range starting -90.

You must understand this period.

To get this concept the best method is to get a piece of ferrite or a piece of red brick. Set the detector on a metal free surface and GB by using the ferrite or a large red brick. Brick is close enough to ferrite. This is THE ONLY ACCURATE METHOD to air test a coil..period. Well there is another way but thats next.

Now scan your coins to get an idea of proper VDI especially on say a quarter a penny and nickel.

If you want now go set your GB offset like 8 degrees positive and see what happens now.

There is a second method using a CD disc. You DO NOT GB to the disc. Rather you will set the GB offset manually WITHOUT performing an GB at all until the CD gives a 0 (zero) VDI reading. This is a cheat but will give you a proper offset for air testing coins.

ALSO....BEFORE YOU SWAP COILS!!!!!!!!!!!!!!!!!!!!!!!! find a patch of clean ground first. Because as soon as you turn the machine on it will want or require you to GB after it does it's ORP calibration. If you try and GB on ground with metal in it you will COMPLETELY screw up the coil calibration and have to do the ENTIRE calibration again. Not a problem but you can't just re ground balance if you screw the pooch on a GB while calibrating a coil. This info will spare you great pain and suffering that I had to learn the hard way.

So....Read it..learn it..live it.!!!!!!!!!!!!!!!!

 

[jimz49]

Thanks for the great advice azsh07!! I've been getting pretty accurate VDI readings, so I'm assuming my GB is probably okay. Never really thought about the wrap around effect caused by the GB being offset too much one way or the other, but it sure makes sense. Your suggestion of double checking with a coin after GBing is sound advice.

 

[Sven]

Thanks for the info copied and saved it to doc file.

That's really great info, when I first got my new Berkut, had some ground balance and ID issues as you mentioned. Mainly I forgot what I learned having not used
a Berkut for a year. Silver dollars wrapped around to iron. ID's were way off etc. I managed to get it right but, your post clarified how and why it happened.
I also found if you don't adapt the coil correctly, you'll end up in a similar situation. You can't ground balance properly and targets will not be picked up.
I kept a little ferrite rod handy and with a bit of help from Igor. At first I thought I had gotten a bad coil, knew that was failed thinking as the coils were factory set-up
for my detector. My Berkut GB's like a charm now, a few bobs and away I go.

Here's something I did last weekend using the 6" 14khz coil. Somehow I was not paying attention when I turned the detector on and pressed the GB button with gloves on, didn't notice
but edited the Berkut into thinking it had a 6" 7khz coil on. It ran pretty quiet, I was still finding stuff. Noticed my error after shutting down to get out of the rain then turning it back on after the rain passed.
With the correct coil entered 6" 14khz, still seemed quiet but ran deeper and ID's were better. So I just have to be careful when I turn the detector on and go to GB.

Keep the info coming.
I was too keene on the 6x10 20khz coil I tried a few weeks ago. Thought I liked the 14khz better. After my evening on bench testing and tuning that produced a Berkut that ran 1000% better the next day,
it would be in my best interest trying it again with a proper running detector. So I decided not to sell it.

 

[After-1-]

azsh07---Thanks for explaining the way to GB, I will use your method for the air test. From what I think I remember, when I GB at the area I'm going to hunt, I'm looking for a very straight vertical line in the center of the screen?-------------after1--------------

 

[azsh07]

azsh07---Thanks for explaining the way to GB, I will use your method for the air test. From what I think I remember, when I GB at the area I'm going to hunt, I'm looking for a very straight vertical line in the center of the screen?-------------after1--------------

Actually a Horizontal line indicates a neutral GB relative to the ground signal.

You can set it slightly pos or neg if you like. Nothing wrong with that BTW. Most of the time I set mine slightly Pos. A slight offset will not move the VDI much if at all.

I would do the GB procedure. Then go to the manual GB function ( varies a little between the three machines on how to access it but operates the same) now while in manual GB I would sweep the coil side to side and make sure the GB line was horizontal.

When you do the auto GB sometimes the trace happens pretty fast so I double check in manual GB adjust. It is just easier to see the line when you sweep over clean ground in manual GB adjust. I have seen areas or times when the auto GB function would want to GB way too negative. These coils are very sensitive especially the stock monster coil so it can get skewed in ground that is hard to find a large patch of clean ground.

Anyway even after using these detectors for so long I always did the manual GB sweep check after a GB. Became second nature.

And if you ever get in a situation where you have a flunky acting coil first thing is re do the entire coil cal procedure.

Also remember that like the Nautilus temps will affect the coil cal. SO if you coil cal at a temp way off from what you are using it at another day...do it again. I mean a decent extreme especially when down around 30-40 degrees. If you are using it from 50-90 not so much an issue but when you go from say 35 to 70...do it again..or vice versa...going from very warm to cold.

 

[jimz49]

azsh07, what can you tell me about Lt Bound? I've read the manual, but not much help. Read some posts on another forum, and even watched a youtube about it, but I'm still confused.

 

[azsh07]

If you are running in discrimination mode then the left border sets the VDI where targets fall below this setting will not respond. Or depending on the mode all metal you can set this for where the low tone for iron falls. They can call it it Low Tone Border or boundary if using it as an audio ID for the lowest tone or left discriminator border or boundary.if using disc mode where it acts like any other disc setup where the audio gives no response.
Any target falling in the negative VDI range is considered left boundary or border. Generally all iron falls here...foil is usually just above 0 depending on size...but there are targets in small gold that can fiddle around the 0 VDI either slightly above or below that depending on ground signal influence and also coil frequency. Remember coil frequency will slightly change a targets VDI even when properly ground balanced.

 

[jimz49]

according to the manual it's an audio adjustment. Quoting from the manual....This option allows you to move the sound border of nonferrous low tone (LT) to the iron sector by the required value. It then goes on to try to explain what that means, but I find their explanation very confusing.

 

[azsh07]

Right....it simply moves the boundary ( actually think the VDI number) where the machine gives the lowest tone for iron. If you set the LT boundary at -10 then from -10 to -90 is the lowest tone. Set it to 0 then 0 to -90 is the lowest tone. Thats all there is to it. Its really just adjustable iron audio...similar to say some Teknetics etc...

I mentioned the other boundary as it is displayed the same way and works in a similar way but sets where the machine stops making a sound on ferrous targets. Was not sure which one you were actually thinking of. Just depends on what mode you are in.

But again yes the LT boundary just sets where ( what VDI number) the low tone kicks in for iron.

The manual kind of goes on and on about why you should set it to different values and probably makes it more confusing. For me...I set it at-10.

 

[jimz49]

So, if you're a coin hunter like I am, then setting it at zero should be good....right?

 

[azsh07]

Would be fine. There is not much at or around 0 that is a keeper for coin guys... Even small gold rings are usually 10 or higher. It is just a personal preference...if you coin hunt then there is nothing at 0 or below worth while.

 

[Sven]

Would be fine. There is not much at or around 0 that is a keeper for coin guys... Even small gold rings are usually 10 or higher. It is just a personal preference...if you coin hunt then there is nothing at 0 or below worth while.

That's what I am finding with the Berkut. Digging a lot of those just to learn and see for myself what they are. But, those that live in countries with steel cored composition coins, you need to pay attention.
If a signal bounces from a neg to a positive and the numbers are similar it could be one of the newer $1 and $2 coins and or the clad coins on edge.
-26 seems to be the coins on edge. Yesterday dug a lot of trash, amazing how deep some of those small pcs if foil can be found. Probably dug
100 trash targets. Anything from 0 to +45 was trash, the 37 and up range will generally be gold rings, so I will dig those targets to be sure.

Got lucky yesterday only one penny............

 

[jimz49]

I found the following and thought it might be useful or at least promote further discussion.

LT (Low Tone) bound is an audio setting. LT bound has no affect on the target's VDI. This setting applies to the sound border of iron and the non ferrous zones. Everything to the left of the LT Bound setting will be sounded as iron, everything to the right will be sounded as non ferrous metal. For instance, when the LT bound is set on -20 all the signals from -20 to +90 will sound as non ferrous and all the signals from -90 to -20 will sound as iron. Passing over tiny gold objects that produces a VDI of -9, will be sounded as a non ferrous object with LT bound set on -20. As we know, low conductors, especially tiny low conductors, could hide in the iron zone and this setting helps us by identifying them with a non ferrous sound.

The metal detector's ability to differentiate iron from non ferrous metals depends a lot on the frequency of the coil. Therefore, LT bound should be adjusted with the frequency of the coil in mind. Also, it's a matter of taste when making this adjustment. Someone might prefer setting LT bound on zero and digging all the signals from -36 to +90. In this case you will need to pay attention to every iron signal and decide what should be dug and what should be left alone.

The following are LT bound suggestions for different frequency coils:

LT bound for 3 kHz Coils

-40 to -38

LT bound for 7 kHz Coils

-36 to -26

LT bound for High Frequency (12 kHz, 14 kHz, 18 kHz, 20 kHz) Coils

-26 to -16.

Note; high frequency coils differentiate iron from non ferrous metals much better, especially the 14 kHz,18 kHz and 20 kHz coils. It's less likely to have non ferrous signals in the iron zone with a higher frequency coil.

 

[Sven]

I found the following and thought it might be useful or at least promote further discussion.

LT (Low Tone) bound is an audio setting. LT bound has no affect on the target's VDI. This setting applies to the sound border of iron and the non ferrous zones. Everything to the left of the LT Bound setting will be sounded as iron, everything to the right will be sounded as non ferrous metal. For instance, when the LT bound is set on -20 all the signals from -20 to +90 will sound as non ferrous and all the signals from -90 to -20 will sound as iron. Passing over tiny gold objects that produces a VDI of -9, will be sounded as a non ferrous object with LT bound set on -20. As we know, low conductors, especially tiny low conductors, could hide in the iron zone and this setting helps us by identifying them with a non ferrous sound.

That's how it works on the Berkut. Plus I have an equalizer that I can adjust the volume of each sector. So I can set LT to 0, anything below will be low tone. Now if I want to be alerted when a good low tone target 0 to lets say -22, passes under the coil. I can keep that volume sector high and turn down all other iron sector volumes. When I hunt in 10 tone and LT to -22, the tone is higher than what I like. So I can play around a bit more with audio than the Sorex.

 

[After-1-]

With the Sorex do I need a volume control for my head phones ? Mine do not have a control ------------after1---------

 

[Sven]

With the Sorex do I need a volume control for my head phones ? Mine do not have a control ------------after1---------

 

[After-1-]

I ordered the Sorex Pro with the 6x10 14khz coil and the machine will be put in the mail on Monday.--------after1------------