ATPRO with different Coils and Depths? How about Negative / Positive Bias?

Hey all,

Looking for anyone with experience with Depths and Hunting techniques with the 5"x8"DD and 4" (Puck) coils... I''m about to purchase a 5"x8" coil and was wondering how others found them to function when hunting.. I'm constantly amazed how well the 4" works when in REALLY trashy areas, but haven't found very good depth with it and still have not used it in - or + Bias yet.. The 8.5"x11" is a great coil, but I have a feeling it may be 'blanking out' or having a tough time ID'ing moderately deep coins in some of my Iron infested sites. These are sites where nails are 'sometimes found', but more often they have 'mostly disintegrated', leaving nasty 'Halos' behind instead and making hunting quite difficult.

I was also wondering if others were using a Negative or Positive Bias while hunting and how they found it worked for them... I find the negative bias reads targets about 2 to 4 digits higher on my machine (depending on level of Bias). I rarely use the Positive Bias as I find that theres not a lot of worthy 'lower Conductors' up here where I live (It's RARE to find Musketballs or similar..), but having said that, does anyone notice the benefit with water hunting for GOLD JEWELRY or other Items that I may not be thinking of using a positive (+) Bias?

I've tried setting up a Test Garden in one of my yards, but there's just a bit too much EMI from the School next door and a few surrounding houses to get accurate results, thus my reason for asking here...

Any and all comments are welcome!

Cheers,



Edited 1 time(s). Last edit at 04/01/2013 08:36AM by Peacemaker.

I hunt with the 5x8" coil and love it it hits hard on high and low conductors and depth is close to the stock 8.5x11" coil!!

Peacemaker, I may have postyed this elsewhere and if I am repeating myself....forgive me. But I thought I should share it: the other day it was pouring rain outside. I was in between reading a book, and, well, plainly, was just bored. So I grabbed my AT Pro with stock coil. I set it up in a room with little to ne EMI and did some air testing.
I placed a plastic ruler (with graduations in INCHES) and placed it at the bottom of the coil so as to measure air depth. Ground balance was set at 76 which is what it was set at when I last used it outdoors. I ran a quarter back and forth and full sensitivity....normal sweep speed. It was hitting the quarter at around 10 inches. I then lowered th ground balance to 60. I then swept the quarter back and forth and was able to easliy acquire the quarter at 11.5 inches. More important than my 'less than precise' measurements, is the solid fact that I DO see an increase in depth when ground balance was lowered. But how this plays out in the ground......I don't know. But maybe it's a little helpful. Kevin

88junior Wrote:
-------------------------------------------------------
> I hunt with the 5x8" coil and love it it hits hard
> on high and low conductors and depth is close to
> the stock 8.5x11" coil!!


Hey Junior, Good to know!
I'm VERY interested now in getting the 5x8" coil and trying it with a - (negative bias)!! I think it will be interesting to see how it reacts in depth both before and after... Gotta' get one now!



Kevin B Wrote:
-------------------------------------------------------
> Peacemaker, I may have postyed this elsewhere and
> if I am repeating myself....forgive me. But I
> thought I should share it: the other day it was
> pouring rain outside. I was in between reading a
> book, and, well, plainly, was just bored. So I
> grabbed my AT Pro with stock coil. I set it up in
> a room with little to ne EMI and did some air
> testing.
> I placed a plastic ruler (with graduations in
> INCHES) and placed it at the bottom of the coil so
> as to measure air depth. Ground balance was set
> at 76 which is what it was set at when I last used
> it outdoors. I ran a quarter back and forth and
> full sensitivity....normal sweep speed. It was
> hitting the quarter at around 10 inches. I then
> lowered th ground balance to 60. I then swept the
> quarter back and forth and was able to easliy
> acquire the quarter at 11.5 inches. More
> important than my 'less than precise'
> measurements, is the solid fact that I DO see an
> increase in depth when ground balance was lowered.
> But how this plays out in the ground......I don't
> know. But maybe it's a little helpful. Kevin


Kevin, always good information, Thanks. I see you are also interested in finding a 5x8" coil and I'm super pumped about getting the same coil for these horrendously 'trashy hunting sites' that I have in mind!

On a separate note, I went out today with into a moderate to heavily trashy area using a -(negative) bias and was able to pick out a 1908 5-cent piece from just over 7" (real-time hunt). It was a 'tiny bit' scratchy, but nice and clear and quite obvious and my guess is that I could have hit it another 1" to 2". Not sure if I mentioned, but these Canadian 5-Cent pieces are a mere 1.16 grams, 15.5mm and very thin...(quite a bit smaller than a dime). I'm also hitting old .32 caliber @ almost 9" and .22 shorts @ 7-8".
I'm looking forward to trying out the 5x8" with mine and the 8.5x11" on a buddies ATPRO to see how they compare in 'Real Digs'.

Cheers,

Thanks to Keith Southern (he showed me an Ebay store who had them in stock) I bought one and received it (folk...they were FAST!!!) and have it mounted on the All Terrain Pro. With some juggling of my schedule tomorrow....I am going back to the site that has produced some old finds. By the way, I performed the same air test on my 5x8 coil today!!! And with a ground balance of 76, I was getting ten inches on a silver dime. When I lowered the ground balance to 65....I was getting the silver dime with repeatable midtones at 11 inches. Now...this is in the air and as we all are well aware, air test don't really tell us much. BUT.....they DO tell me (or at least I think they do) when I have a hot or cold unit. This is my fourth AT Pro and the air test depths of the last three have been pretty much the same....excellent. The first AT Pro was a new one with the coil problems.....it would false when ya swiveled it in the air fairly vigorously....and it would false more frequently when hitting a small sapling while detecting in the woods. The last three units have been GOOD TO GO!!!! To GO metal detecting that is. Good luck Peacemaker!!! Hope ya find something OLD and RARE!!!! The main thing is....find some peace and quiet...for it is worth it's weight in gold these days!!!! These AT Pros are really a working man detector!!! I proudly use mine!!! Well, I proudly use all mine. (but just one at a time)

Good Stuff!
I'm on it, I want that Coil!

I got one this winter and haven't set it up yet, thanks for the reminder, it still on the kitchen table, wonder why the wife hasn't thrown it away, haha, I have a back yard full of trash I could test it on, stay tune