SPP HICCUP

[old hand]

Roscoe OK sorry about that the NF had a better response on the gold I also tried a 11 mono commander but the nf had the best response the mark I was referring to is the triangle factory settings on the gain go below that and the gold could not be heard thanks john

 

[Guest]

Old hand how all is the gold your using to test?

 

[old hand]

The bit I was using today was found today by another detector operator using a 5000 just weighted it and it was 0.3 of a gram

 

[Guest]

Unless it's very porous you should get a response with near any coil even at half the gain iv got a .25 & 3 grain here I'll test

 

[old hand]

No I think we are getting our wires crossed all the coils picked the gold up, just that the NF was by fare the best ,coils are not the problem its certain ground that creates the hiccup I found a rock today ever time I went over it hiccup regards john

 

[Guest]

Oh yes no worries maybe keep a rock that causes it and if you send it to me I'd like to test as I have a few in my collection that are very common in Australia and I'd like to send them to Reg for testing as such but iv goto look into the laws for sending rocks over seas if there is any?

 

[Reg]

You get a hiccup when you move the coil up and down, but do you get the same hiccup when you hit a target?

Reg

 

[old hand]

Its there when sweeping at times worse in some areas than others ,when hitting a target its OK it not there and you can get it pumping the coil up and down doing the ground balance thanks john

 

[Roscoe]

Its mostly got to do with the coil breaking contact with the ground or the machine thinks that the coil is coming away from the ground ie. a sudden mineral change in ground, a depression, going over rock etc. I don't think the rock had any thing to do with it as per its mineral content, but just the action of Oldhand breaking the coil away from the ground will cause it.

I have come up with a more consistent ground balancing procedure. Although this doesn't stop the hiccup it does give a more consistent balance to the ground from what i have seen. I raise the coil slowly about 4-6 inch above the ground and pause for a second or so and then slowly lower the coil until it touches the ground and listen to what tone is given. Adjust GB until balance point is achieved. The key is the pause at the top to allow the auto tune to stabilize and then lower. Try this and let me know how it goes with your SPP.

 

[Reg]

Thanks guys,

Your info helps paint a better picture. Now, a target us usually a slightly sharper signal and most likely triggers the blanking circuit I mentioned before. So, it there is no hiccup on it, then the blanking probably stops that signal.

In the case of a very weak signal, it might not be big enough to trigger things. If that is the case, then there is no blanking and as such, the signal probably from the ground sneaks through.

So, now I need to figure out a way to simulate it.

Just for fun, try going over a target such that the signal is extremely weak. Ideally, the target should be something that is very close to the ground in where it balances out.

Reg

 

[Roscoe]

Reg, you said there is a blanking system that stops the SPP from giving a trailing tone after a target is passed over. Is this blanking systems easily modified or removed from the system? The SPP doesn't come with a Conductivity switch or pulse delay so if a trailing tone was allowed just like ML and Garrett machines it would not bother me the slightest. The operator would still know if its a High or Low conductive target by the first part of the signal. This type of system seems to be a whites thing, so as they can give people the conductivity switch for predominately Relic hunting purposes. Because the SPP lacks the Con. switch and Pulse delay maybe its time they focus on a pure gold machine and the SPP would be a great little machine to experiment on and maybe by allowing a trailing tone it might eliminate the Hiccup effect as well?

 

[ronniecruisin]

Well said Roscoe!. You may have stumbled upon something there methinks.

 

[Reg]

The blanking circuit is something Eric Foster designed many years ago and put in the GS5. White's simply copied it and modified it a little. So, it isn't a White's thing at all.

As for the conductivity switch, well that is my design that I found very useful not only because I could use it to coin hunt, but because it reduced the noise quite a bit.

If you want to disable the blanking ckt that eliminates the half of the signal then you can by adding a jumper across D9 or C56 and both should be close to U12. Adding a jumper across either of these two parts should inhibit the signal that shuts off the blanking of half the signal.

Now, I don't think this will cure the problem and you may end up with even more signals, so let me know if you try a jumper and what happens.

If you want to study the circuitry, you can go to the Geotech1 forum and search for the GS4 and GS5 schematic. Both have this circuitry. obviously, the part numbers are not the same as those on the SL.

Reg

PS: I forgot to mention, the SPP is very smooth and quiet compared to the TDI and this comes from the special noise reduction circuitry. Now, this noise reduction design complicates things quite dramatically even though it is a simple design. So, I am not sure just what type of signal or signals you will get by eliminating the blanking circuitry.

Because the noise reduction circuitry sort of rectifies the signal, you may not hear the the back half of the signal even with the blanking inhibited and the hiccup may stll remain.

If you do short either part mentioned, please let me know what happens.

 

[Roscoe]

Reg, Thanks for that information mate and your time on this hiccup thing. I am going to make a video of the hiccup effect this week and email the video clip to you. It must be frustrating for you as you cannot see or hear the problem.

 

[old hand]

Roscoe I noticed today when GB the hiccup was only on the up stoke of the coil ,but still getting it on the sweep is most annoying ,I will be out tomorrow morning and I will try your suggestion regards john

 

[old hand]

Roscoe when you make a video can you put on here just so I can make sure we are all looking at the same problem thanks john

 

[Reg]

When I first designed the noise reduction circuitry, I had a false signal if the coil raised too quickly. Otherwise the detector was very smooth and easy to ground balance. Now, my design was inadequate and I know that now. What was done by Carl Moreland was to add more circuitry in the other channel and add a resistor in the ground channel. This seemed to eliminate the signal when the coil was raised quickly, but did make the detector a little touchier to GB. Fortunately, over here in the US, the GB being a little touchier didn't cause a problem and the noise was gone.

Now, I realize that all mods didn't eliminate the problem but made it seem to disappear until now. So, it appears the noise just got moved back until the ground signal became intense enough and is now rearing its head again.

Reg

 

[Roscoe]

I have come to the conclusion that the Hiccup is going to stay and although it can be a bit annoying at times i think i can live with it. I think because how quiet this machine runs in areas that were off limits to other PI detectors i forgot just how noisy my other PI detectors were in the locations that i run the SPP. I have operated the SPP in areas that made my other PI's warble that bad i had to put a DD coil on and run in cancel mode. But, the SPP can run with a mono coil in these areas no problem.

Reg, You mentioned in one of your other posts that the EMI is still there and that although we cannot hear it is still effecting the detector. listening to the SPP's threshold run so smooth its easy to forget that your surrounded by so much EMI and the SPP's electronic circuit is in fact doing a mighty job filtering all that noise out and still allowing a small target signal to come through.

 

[Reg]

Well, I remembered I had some special rocks from OZ that sound off with a strong signal. So, I tried testing with them and what I found is it appears the problem isn't so much the circuitry but rather too much gain. Why do I say that? Well, the greater the gain, the more obvious it becomes that the GB signal is not accurate over the entire up and down range of the coil. In other words, it might be ground balanced at 2" from the ground, but it isn't at 1".

Add this condition with the fact that some areas the ground signal is so intense, it causes a response at maximum gain no matter what a person does. Perfect GB gives the least error so works best. Regardless, the error signal is intense enough to be heard.

Can anything be done? Maybe, but it is going to take some thought process. Fortunately, I still have a few ideas I need to try. The problem is finding the best solution that is also the easiest to do.

In the mean time, reducing the gain doesn't reduce the depth capability that much once the gain is above the level when you hear small gold. In other words, try some testing to see just what is gained or lost. Don't just turn full on or full off. You may find that detecting a 2 grain nugget may not change depth wise when the gain pot is half way and max.

Better yet, test a small nugget for depth at the setting where the hiccup is gone and then at maximum gain, and finally something in between where the hiccup isn't a problem or much of a problem, but better than where the hiccup doesn't exist.

Reg

 

[old hand]

Reg I total agree the more gain the more hiccup
I have noticed the hiccup is only on the up stroke of the coil no matter where the GB is, even if the GB is spot on some ground the hiccup occurs
With the gain on the factory pre-set mark there is still a slight hiccup still annoying at times
If I back the gain off anymore I cannot get a signal on a 0.03 gram at a 1 inch. If I cannot get that what may I be missing at a depth on just a murmur in the threshold
regards john