Kelly Co director of sales sent me my 4th SEF coil....overnight:stars:.

[burlbark]

I was able to talk to the director of sales at Kelly Co. He was very sorry and told me that he would test and overnight a coil to me. I got it and guess what...... It is bad. 2 guys tested it at Kelly Co but I guess they did not know what to look for. I cannot run the gain up beyond 6 without it falsing into oblivion. The third coil they sent me was a black one for the m6 and dfx/mxt. This coil performs well except I cannot run single frequency 22.5 above 3-4 on the gain. With the white coil I am seeing a signal of 69% and a noise of 4%. The black non-v rated coil gives me a 38% and works 5x better.

Why I cant get a good coil for my v3i from Kelly Co I do not know. They sent a tag in the box telling me it was tested by a salesman and the director of sales, but I am afraid they dont know how to check a coil.

Here is how you do it. Please keep in mind that you want to keep the coil away from anything metal and in an area of low emi which may be impossible in a commercial building.

When in the user menu go to sensitivity and press zoom/view. There on the right you will see signal and noise percentages. Increase the gain using the side to side arrows when on the highlighted or darkened area and you will see these percentages increase. If the coil goes above say 38% in the signal with the gain at 15 you reject the coil. Whites coils go to 15 and allow tx boost at the same time on a vast number of them.

If the coil does not have a good signal number it will false signal the detector through all its range and no amount of tuning and tweaking will stabilize it. The v3i is a very sensitive machine and I have been using mine going on 3 years and have 4 Whites coils for it. Of those coils I have had 2 go bad and be replaced by Whites.

I now have to send back a 4th coil to Kelly Co.... Do I dare to try again? I have seen that 2 of the users on here have received good coils and one posted screen shots of their signal numbers. I just want a good one

 

[norbyx]

After reading your post I went to check my white detector and see what it was doing with the original d2 coil. I have no problem whatsoever to increase the sensitivity to the maximum in any of the frequencies, still if the I used a three frequency mode I get more or less the same numbers I seen the picture you posted. So I don't understand ecstatically what your problem is with the Coils you are using, unless that picture isnt your detector.

 

[burlbark]

After reading your post I went to check my white detector and see what it was doing with the original d2 coil. I have no problem whatsoever to increase the sensitivity to the maximum in any of the frequencies, still if the I used a three frequency mode I get more or less the same numbers I seen the picture you posted. So I don't understand ecstatically what your problem is with the Coils you are using, unless that picture isnt your detector.

You are getting a 69% in your signal with your d2 while it is in the air not around any emi? If so you need a new coil on your detector, talk to your dealer.

My Whites coils give me on average a signal of 25 with the gain cranked to 15. If you are seeing anything above 35-40 with your gain turned up to 15 than your detector is acting erratic and falsing on non existent targets. This is going to cause you tremendous grief and you are going to battle it till you replace the coil or force you to run a lower gain. In my case with the white coil I would have to run a gain of less than 6.

I dont know if you can understand this but this is a bad thing, really bad for metal detecting to have false signals.

When you say "white detector" is this a v3i? I assume so when you say original d2 coil. Your post doesnt make a whole lotta sense....

More or less the same numbers.... I am glad you seen the pictures I posted.

Here is another one..... This is a black sef that overloads at a signal of 89% in the 22.5 frequency but still operates okay running in 3 frequency. It has a signal of 38% in 3 frequency, this means that if it gets warm it will start going crazy, my whites coils read at 25% and stay stable until they get really hot and then I may have to back the gain down.

 

[norbyx]

Ok no I don't get it... My test was done in my house so there might be EMI arround but let me try to understand. Isn't signal and noise the famous Signal to noise ratio (I am ham operator) so the higher the signal and the lower the noise the best?
On the other hand if you crank up the sensitivity the signal has to go up correct? And the noise should go up but just a little bit...

I will have to test in an open area to see the difference and maybe I will understand better.

Also since in the manual there is no explanation on what this numbers really mean is there some other place I can search and read?

 

[burlbark]

For comparison here is my d2 inside my house with the gain turned up to 15. That is a signal of 7.6 and I was surprised to see it that low. My 5.3 works flawless yet gives me a signal of 25.

 

[norbyx]

Yeah I went to the whites forum and I found the explanation. Signal % is the % lost in the signal in the ground, evidently I have a hi emi in my living room just went to test it again and since I live in a condo at the last floor I opened the window and put the detector outside compleately (even a bit scared to let it fall down) anyhow the signal was 22 with a noise of 3% so not all that bad. If I used the TX boost it went to 50% with a noise at about 5-7%. I undestand it now. Well I am quite new to the V3i so obviously I still have to learn how it works.
Anyway thanks for the information and the time taken to let me know what is right and wrong.

Now the question since aparently the signal and noise would have to be ideal on 0 and 0 to get a better response in a certain ground than the best performance would be from the highest obtainable number from the signal divided the noise?
So for example if I crank the sensitivity up to 15 (just in example) and get a signal of 30 and a noise of 3, s/n rateo would be 10
But if I lower the sensitiviti and get a signal of 10 and a noise of 0.5 than the s/n would be 20
The second case would give me a better performance of the detector?
If so I don't understand the sense of the TX boost since it will increase the signal% lost by a lot.

 

[burlbark]

The first number in percentage is signal being lost to the coil or ground, the 2nd number is emi or interference.

You want both of them to be low and the lower the better. It is no the same rating as radio components where you want the higher numbers.

 

[burlbark]

Yeah I went to the whites forum and I found the explanation. Signal % is the % lost in the signal in the ground, evidently I have a hi emi in my living room just went to test it again and since I live in a condo at the last floor I opened the window and put the detector outside compleately (even a bit scared to let it fall down) anyhow the signal was 22 with a noise of 3% so not all that bad. If I used the TX boost it went to 50% with a noise at about 5-7%. I undestand it now. Well I am quite new to the V3i so obviously I still have to learn how it works.
Anyway thanks for the information and the time taken to let me know what is right and wrong.

Now the question since aparently the signal and noise would have to be ideal on 0 and 0 to get a better response in a certain ground than the best performance would be from the highest obtainable number from the signal divided the noise?
So for example if I crank the sensitivity up to 15 (just in example) and get a signal of 30 and a noise of 3, s/n rateo would be 10
But if I lower the sensitiviti and get a signal of 10 and a noise of 0.5 than the s/n would be 20
The second case would give me a better performance of the detector?
If so I don't understand the sense of the TX boost since it will increase the signal% lost by a lot.

With tx boost your increasing the output power but you can lower the gain to see less noise. Dont bother trying to determine signal to noise ratio by calculating mathematically. You just need to turn your gain up as high as you can until you notice falsing from mineralization or you start getting multiple false positives from ferrous items. As you get more time with the detector you can experiment with setting span in 3 frequency to eliminate some of those falses and then use the filters to target different metals(along with frequency changes if you chose). If I start to get fatigued with audible blips from deep nails I will turn down the gain to 8 or so, I like to run 12.

The sef coil is really a game changer as it has a much narrower detecting field than the d2 and still has greater coverage. Unfortunately they have destroyed their reputation with me and Kelly Co has left me confused..... I will be calling them in the morning.

 

[Rob (IL)]

As I have posted read the VX3 manual. It has the best explanation of theory. The VX3 and V3i have the same electronics except for the user interface.

In most cases you should adjust the Rx Gain to maintain a residual Signal of no more than 30-40%. VX3 will overload at 60%, so it

 

[Rob (IL)]

I would have given up already. maybe I have a collectors item, one that works.

I would have to ask what they consider a good coil. They claim optimized for the V3i, but they don't make anymore claims. Am I correct? How many guys have one that works as it should? As you saw I have one.

[attachment 238666 2012-07-17_143629.jpg] One with boost and one without.

 

[burlbark]

I would have given up already. maybe I have a collectors item, one that works.

I would have to ask what they consider a good coil. They claim optimized for the V3i, but they don't make anymore claims. Am I correct? How many guys have one that works as it should? As you saw I have one.

[attachment 238666 2012-07-17_143629.jpg] One with boost and one without.

Rob.... Would you like to sell your coil? How much.... just name your price.

If I did not have knowledge as to how the coil should read and what to expect from it and a solid control to measure it against I might not be the wiser. I would just run the gain at 4 and find things 2" deep in my mineralized ground.

I would have given up on these coils if it where not for the 3 raving reports we have had here on them. Unfortunately I have not received one like what you guys have.

I spent nearly 30 min on the phone with Gene the director of sales at Kelly co discussing this problem. They tested it in their test garden but may have not been familiar enough with the v3 series of detectors. They really thought the coil they sent me was good. I explained that yes it may see a quarter at 6" but with the constant falsing and the self adjusting threshold going I will never see a deep target. I dont think they really knew how bad a falsing coil effects performance on the v3 series of detectors, it makes it go completely crazy.

They really have tried and I was told that this issue with SEF is going to be resolved and they are going to investigate this and contact SEF. They are happy to give me a complete refund or give me credit till the next batch of coils comes in. I dont know what to do and I have a work trip to Southern California till next week and am going to bring my detector. When they get a new batch of coils in or test one that is good I would be more than happy to purchase it.

I will have to post a new thread for this one upon return.

Could you imagine buying directly from SEF and having to deal with sending them to Bulgaria everytime!!!! Kelly CO has payed for shipping both ways every time now since the first one. I am sure they have a new policy for shipping and checking the sef coils for the v3i, Gene was adamant that my customer satisfaction was foremost. Hopefully I will have a new properly nulled 10x12 sef white coil before long.

 

[norbyx]

Well thank you for your information on the sef coils, I wouldn't want to have all that trouble over a coil that is for sure. Hope you get a good one soon...

 

[Rob (IL)]

I'm glad you got the refund and didn't incur the shipping costs. The D2 is a super coil as you see by your numbers.

In reality, It is a little quieter on the ground noise, 2 more inches in coverage and a little deeper than the D2. I can't be exact probably in the range of an inch. This was verified by someone who's name I don't want to use. Probably it would be hard to see a difference in the field compared to some of the better black ones which had no problem running RX12. A good White one would have less noise.

There is not a lot of difference between RX12 and RX15. The rule of thumb is that, to gain another inch of depth the gain must be doubled. This means that increasing the gain from 14 to 15 will not improve depth much at all whereas, increasing the gain from 2 to 4 should gain another inch. So 4 to 8 gains another inch and 8 to 16, oops there is no RX16, gains another inch. So don't get crazy on setting the RX at the upper levels because it provides diminishing rewards. In some cases the added noise will actually negate the increase. So in my opinion, higher RX and more noise and signal loss would be about the same as lower RX with less signal loss.