GPX start-up and tuning procedure

[FlakMagnet]

Here is a question.

What is the best way to set all the controls on the GPX

to insure you are getting the best out of the auto-tune process?

Here's what I do;

After I turn on the GPX and let it 'warm up' for a couple of minutes,

on the front panel I switch to tracking and sensitive,

on the back panel I turn the gain all the way up.

Then I hit the auto-tune button.

I do this to make the detector as sensitive as possible so that

the maximum interference is taken into account during the auto-tune.

Is there a better way to do this?

Or, is this just b.s. and I could just turn the detector on and auto-tune

and get the same results at the end of the tuning procedure.

Interested...

Thanks to anyone who has an opinion.

and Happy Thanksgiving to all...

Flak

[montana]

Flak . You could try Michael Hashkas tuning procedure for bad interference. Switch to patch mode first if it is still programmed with the factory presets. It is really hypersensitive. Hit the tune button and let it complete its cycle and then switch back to your usual detecting setting. This gives you super smooth threshold but it doesn't seem to hold smooth for a long time. I usually turn on and ground balance first then set the detector box on the ground with the coil propped up on a bush in my usual settings. Hit the button , then light up a cig. or get rid of some coffee while it does its thing. As I detect, sometimes the interference starts creeping back in after a while. I'll retune before making any adjustments. If there is still too much chatter, I'll drop the gain a notch or tweek the manual tuning.----Bob

[FlakMagnet]

Thanks Bob,

I'll give that a try the next time I'm out.

With all the possibilities this detector offers,

starting out with the best auto-tune possible

hasn't been talked about too much.

Have a nice Thanksgiving.

Flak

[Jonathan Porter]

Thanks Bob,

I'll give that a try the next time I'm out.

With all the possibilities this detector offers,

starting out with the best auto-tune possible

hasn't been talked about too much.

Have a nice Thanksgiving.

Flak

This might sound odd, but any sort of ping or pop in the audio (something that is random) is only going to confuse the auto tune process. So with that in mid I would recommend you have the detector set up as you would like to detect and then auto tune from there. Once the auto tune is finalised then go into the manual freq tune control and make fine adjustment to get the threshold smoothed out as much as possible.

I also recommend you place the coil flat on the ground (sometimes this can be tilted if you are detecting on a hill side so will not be at 90 deg) and do not move or touch anything while the tuning process is going on as any sort of spurious noise will upset the process at the point this occurs.

I would say the biggest problem in the US is EM that is coming from more than one source which is notoriously hard to get rid of especially if the freq is changing all the time. I really do feel sorry for you guys sometimes as this must be very frustrating.

JP

[montana]

JP/ Flak. I tilt the coil while tuning because in our terrain which is rough and ever changing, we seldom are detecting with our coil parrellal to the horizon. It seems to work. I set the detector on the ground to keep it motionless as you recomend. I might retune as many as ten times a day, but a slight adjustment with the manual tuner will often take care of increasing interference and is quicker than repeating the tuning process. It's interesting to have the numbers on the screen to refer to . Often the auto tuner will stop on one end of the spectrum, then an hour later after retuning it stops on the other end. This indicates to me that the interference is ever changing in our highly electronic environment. It's easy to interprate what the detector is telling you in this case . If interference levels increase, re-tune. You know when you've done it right if your threshold is smooth. If it doesn't smooth out , then you will have to look at your audio settings , or your motion settings , or your gain setting. Quiet audio is exactly what it says. It goes a long way toward cutting out EM noise. The slower motion settings also will reduce EM noise to a great extent. Gain settings also have an effect , but reducing gain below 7 really starts to reduce performance. I'd much rather leave the gain at 8 or more and adjust the audio or motion settings. Just about any interference can be controlled with the GPX except lightning strikes. In some ways the tuning may be the least important part of start up. It doesn't increases sensitivity or depth or overall performance of the detector. It only makes the signals easier to hear by reducing spurious background noise. An analogy would be trying to carry on a quiet conversation in a crowded, noisy pub. You will often miss part of the conversation that would easily be heard if the conversation was being carried on out in the desert.----Bob

[nuggethunting]

Hello Flak and All,

I think this is a good thread, because this question is brought up very often. When I'm out conducting field instructions, many prior Minelab owners ask about the "correct procedure" to auto tune a Minelab PI.

I've personally had the best results from all the Minelab PI's by just leaving the searchcoil on the ground and then reaching around and hitting the "auto tune" button. While the detector is tuning, I won't move the searchcoil, but keep it completely on the ground until the tuning process is complete.

I've had much better results using this technique on all the PI's, rather than holding the searchcoil out in the air or rotating 360 degrees to find the worst interference.

I normally only auto tune once in the morning on the GPX-4000 and then use the manual tune control for fine adjustments when there might be planes or other temporary interference around.

I've found in most places the tune works miracles, while in others spots it don't matter, the interference is too powerful to adjust out.

Hope this helps a bit,

Rob Allison

[FlakMagnet]

Thanks all,

the input seems to have a common thread

and I've been pretty close to the median.

I like the idea of making the detector as sensitive as possible before auto-tuning

but

also like the idea of tuning it with the settings that I'll be using.

Interesting food for thought.

Thanks,

Flak

[Paseclipse]

Flak . You could try Michael Hashkas tuning procedure for bad interference. Switch to patch mode first if it is still programmed with the factory presets. It is really hypersensitive. Hit the tune button and let it complete its cycle and then switch back to your usual detecting setting. This gives you super smooth threshold but it doesn't seem to hold smooth for a long time. I usually turn on and ground balance first then set the detector box on the ground with the coil propped up on a bush in my usual settings. Hit the button , then light up a cig. or get rid of some coffee while it does its thing. As I detect, sometimes the interference starts creeping back in after a while. I'll retune before making any adjustments. If there is still too much chatter, I'll drop the gain a notch or tweek the manual tuning.----Bob

Hi Bob, after reading this post last week I decided to give this a try over the weekend in a place I know has a lot of interference. The area is in between two cell phone towers, parallel to some train tracks (trains come every 15 minutes), and a busy freeway. Additionally there are planes that constantly fly over (comercial and private), however I'm not sure if this is a flight path. Either way this place has A LOT OF INTERFERENCE!

After thinking about this for a little bit, I figured I'd try to expand expand on it some. Instead of using the Patch Mode factory presets, I cranked everything up in Patch Mode to have the worst possible interference. Here's the settings I used-

Audio- Deep

Gain- 15

Motion- Fast

I was setting my coil perpendicular to the ground pointed in the direction of the most interference. Then I hit Autotune and let it do it's thing. Once it's finished I flip it back to General Search Mode.

So essentually what I'm doing is using Patch Mode for interference tuning with everything cranked up.

After trying this out I noticed a big difference in the threshold smoothness and amount of interference. In fact, this smoothed the threshold out so much I had to use my throwdown to see if the detector was still working! The threshold seemed to stay smooth for 1/2 - 1 hour on average.

Thanks for the tip! I'm definately using this more in the future.

Del

[FlakMagnet]

Hi Del,

I tried the tuning settings Bob and you suggested today out in the El Paso's.

I think they work well.

The El Paso's are, as everyone here probably knows,

one of the most mineralized, windy and generally weird places to try to achieve

a stable threshold with a GPX (or any detector).

I re-tuned about four times in five hours and I was quite happy

with the threshold stability - it wasn't perfect, but it was as

good as it has ever been for me out there.

When I have more time, I'm going to compare these settings

with auto-tuning with my specific settings dialed in - as JP suggested -

to see if I can decern if one or the other methods has an edge.

fwiw,

Flak

[Paseclipse]

Hi Del,

I tried the tuning settings Bob and you suggested today out in the El Paso's.

I think they work well.

The El Paso's are, as everyone here probably knows,

one of the most mineralized, windy and generally weird places to try to achieve

a stable threshold with a GPX (or any detector).

I re-tuned about four times in five hours and I was quite happy

with the threshold stability - it wasn't perfect, but it was as

good as it has ever been for me out there.

When I have more time, I'm going to compare these settings

with auto-tuning with my specific settings dialed in - as JP suggested -

to see if I can decern if one or the other methods has an edge.

fwiw,

Flak

Flak I didn't know you hunt the El Paso's! I guess I assumed you lived in Az. Where are you located? I've been heading out the the El Paso's recently trying to figure the place out because I'm a little burned out from trying to hunt Randsburg. That basalt out there sure is a pain in the butt!

Yeah after reading this thread, I gave it a try and this trick works pretty good. I'm planning on doing this everytime I head out to the field now.

Del

[montana]

Flak and Del. Switching to patch to tune does work when in horrible interference areas. JP has responded several times when I mentioned this desperation tuning trick, and says that it can't do any good. As we know, it works very well, but apparently JP won't try it or doesn't have an area with extreme interference to try it on. I haven't tried it by power lines, but it sure works in areas with high aircraft traffic. The problem in the El Pasoes isn't caused by power lines but is located smack dab between a Marine air station and an Airforce base with hundreds of training flights with every imaginable type of aircraft a day passing overhead. There is no way he can duplicate the conditions anywhere on the Australian continent, nor could the Minelab techies. By reading Australian forums and seeing the settings they use it is obvious they have no concept of what we endure. I wish just once the Minelab techies would come over here and spend a day with me. They would think all the detectors sent to the U.S. had been damaged in shipping. Thankfully , either by design or by accident they gave us some settings with the GPX that make detecting tolerable even in the worst places. Some things, like the tuning in patch mode we had to stumble on ourselves. We can't use the patch mode with the factory presets because it is so erratic, but we found another use for it.---Bob

[FlakMagnet]

Bob,

Yes I've been reading their posts and yours on that forum

over there...very interesting stuff.

Agreed, the Patch mode works as a tuning mode for sure.

I am going to try it in another area next week that also is

known for the fits it gives detectors.

I'll post when I do.

I also think the idea...which is not new by any stretch...of putting different

"favorite" settings in the other two modes General and Deep has

interesting possibilities.

You would have laughed if you could have seen how tiny the

lone flake I found out there was.

It didn't even make the scale move.

I probably should be embarrassed except that in this case

it took some concentration to tune right and hear the signal,

so I was actually happy.

The skunk just sneered as headed for the exit.

Flak