northwest QED tips
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australian electronic gold prospecting forum.com  |  QED users  |  QED users (Moderator: bugwhiskers)  |  Topic: QED tips 0 Members and 1 Guest are viewing this topic. « previous next »
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GARY
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« Reply #20 on: Saturday February 23 2019 09:59:17 AEDT AM »

After watching a show on Facebook it was mentioned that when the ground is wet more depth penetration is possible with a PI detector even more so on wet ground at the beach.

In the past when I had encountered wet ground on the goldfield to me the detector became more prone to hot ground noise although I was using a 18" mono on a GPX at that time.

I have not had the opportunity as yet to operate the QED under similar wet conditions on the goldfield.

Therefore does wet ground produce more depth with a PI and has any other QED users detected over wet goldfield ground?

Gary.   
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Reg Wilson
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« Reply #21 on: Saturday February 23 2019 10:31:56 AEDT AM »

I think the wet ground thing is a bit of a fallacy. I've mostly found wet ground to be noisier.
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dasenator777
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« Reply #22 on: Sunday February 24 2019 09:47:16 AEDT AM »

i agree there reg have found it very noisy as well after a good down poor, even the next day or two if enough rain.  happy face
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bugwhiskers
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« Reply #23 on: Sunday February 24 2019 13:21:35 AEDT PM »

Water will dissolve any salt in the ground and make it conductive and therefore detectable.
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« Reply #24 on: Sunday February 24 2019 21:09:48 AEDT PM »

At the Coiltek test site near Maryborough a detector user did some depth testing using a Minelab detector, from memory, and was able to hear all targets. Some time later after heavy rain he returned to do more testing and found that using the same detector and coil he could no longer pick up the largest target which was lower down and therefore more saturated than the other targets.
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Doug
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« Reply #25 on: Monday February 25 2019 12:06:57 AEDT PM »

  
I think the wet ground thing is a bit of a fallacy. I've mostly found wet ground to be noisier.

I would agree. The more the conductive the mineral content of the soil the more noisy the ground becomes as it gets wet.
doug smile
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Goldman
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« Reply #26 on: Thursday March 14 2019 10:23:54 AEDT AM »

Hi everyone,

Just to state the obvious, always wait until the audio (fully) recovers before swinging back over a target. It is amazingly easy to swing back to soon and thus not get the expected signal response on the way back over the target.

Next time you are out, experiment with the above and you will see what I mean.

Cheers Goldman
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Goldman
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« Reply #27 on: Thursday March 14 2019 11:46:33 AEDT AM »

Further to the previous audio recovery tip,

it is very important to swing over the target in both directions and past the target so that the target is no longer under the influence of the coil.

This will also allow the double tone indicator or wire/nails to be heard.

Cheers Goldman
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Goldman
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« Reply #28 on: Thursday March 14 2019 12:42:15 AEDT PM »

Manual ground balance
Two things to remember when performing a MGB:
1) Always allow the audio to recover before moving the coil back down to the ground
2) MGB slowly; take your time and you will get a much more precise ground balance, for example, the minelab ground balance  (bobbing) speed is way, way too fast and you will probably not be able to ground balance. Slow it down; find the rhythm based on the audio recovery time and you will find the MGB works perfectly.

Cheers Goldman
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egixe4
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« Reply #29 on: Friday March 15 2019 08:38:01 AEDT AM »

Yes, spot on Goldman
And probably where most experienced ML users go wrong when using the QED.
The QED MGB is very, very good when used correctly.


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Doug
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« Reply #30 on: Friday March 15 2019 10:53:12 AEDT AM »

 Bugs I wonder is it possible to speed up the  audio recovery?
doug smile
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« Reply #31 on: Friday March 15 2019 12:18:09 AEDT PM »

  
Bugs I wonder is it possible to speed up the  audio recovery?
doug smile

It would be but at the expense of good EMI rejection.
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Goldman
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« Reply #32 on: Friday March 15 2019 12:42:48 AEDT PM »

  
  
Bugs I wonder is it possible to speed up the  audio recovery?
doug smile

It would be but at the expense of good EMI rejection.

I for one am very happy with the current setup, EMI whilst detecting is a pain.
Cheers Goldman
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GARY
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« Reply #33 on: Friday March 15 2019 19:55:42 AEDT PM »

  
Manual ground balance
Two things to remember when performing a MGB:
1) Always allow the audio to recover before moving the coil back down to the ground
2) MGB slowly; take your time and you will get a much more precise ground balance, for example, the minelab ground balance  (bobbing) speed is way, way too fast and you will probably not be able to ground balance. Slow it down; find the rhythm based on the audio recovery time and you will find the MGB works perfectly.

Cheers Goldman

Very good tips Goldman, keep them coming and thanks for sharing.

Gary.
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Goldman
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« Reply #34 on: Tuesday March 19 2019 20:40:46 AEDT PM »

Rising vs falling pitch targets
When determining a ‘dig target’ or a ‘non dig target’, the following is offered:
1) falling pitch with a high/large detection distance, then dig every time
2) rising pitch with a high detection distance would be suspicious as rising pitch targets are typically small, which would not normally offer a high/large detection distance

Food for thought!

Cheers Goldman

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Goldman
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« Reply #35 on: Tuesday March 19 2019 20:56:31 AEDT PM »

Rising vs falling pitch
Target shape/size determines either rising pitch or falling pitch target response

For example:
- 5 cent piece  - rising pitch
- $2 coin - falling pitch

Or:
- approx. below 2 - 4 gram gold target will mostly produce a rising pitch
- above 2 - 4 gram gold target will mostly produce a falling pitch

The above are indicative only

Then there is the detection hole where targets can be missed....

Cheers Goldman 
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GARY
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« Reply #36 on: Tuesday March 19 2019 21:32:39 AEDT PM »

  
Rising vs falling pitch targets
When determining a ‘dig target’ or a ‘non dig target’, the following is offered:
1) falling pitch with a high/large detection distance, then dig every time
2) rising pitch with a high detection distance would be suspicious as rising pitch targets are typically small, which would not normally offer a high/large detection distance

Food for thought!

Cheers Goldman


Definitely food for thought Goldman as both scenarios I have not thought about in those terms as you have described.
Will now try & use your tip for a dig-me or dig-me-not targets.

Cheers,
Gary.

 
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Goldman
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« Reply #37 on: Tuesday March 19 2019 22:30:27 AEDT PM »

  
  
Rising vs falling pitch targets
When determining a ‘dig target’ or a ‘non dig target’, the following is offered:
1) falling pitch with a high/large detection distance, then dig every time
2) rising pitch with a high detection distance would be suspicious as rising pitch targets are typically small, which would not normally offer a high/large detection distance

Food for thought!

Cheers Goldman


Definitely food for thought Goldman as both scenarios I have not thought about in those terms as you have described.
Will now try & use your tip for a dig-me or dig-me-not targets.

Cheers,
Gary.

 

Be suspicious, but be wary of not digging targets.

couple the rising pitch and high target response analysis with the double dip response normally associated with a ferrous object that’s long and thin (eg: a nail or piece of wire), bearing in mind that the double dip will occur when moving the coil along the length of the above object, single target reponse when moving at right angles to the length of the object. So test the suspicious targets from all angles. If rising pitch and high target response and a double dip, then be very suspicious.

take your time to evaluate the suspicious targets, then armed with your informed target analysis, either dig or walk away.

Of course always do a visual, it’s amazing what you can see when you really look; Tin, foil, etc are often just a look away. Next try the magnet (if you have one), then do as per the above.

Cheers Goldman
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GARY
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« Reply #38 on: Yesterday at 16:02 »

Found this question on Facebook.

Question: I always hear and read that you need to set the mode to suit the coil, how do you determine this?

Answered by Bugwhiskers: If the mode is too low for the coil then GB will be poor.

Gary.
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Goldman
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« Reply #39 on: Yesterday at 16:28 »

Detection Hole

The QED has a rising pitch for short time constant (TC) targets (one side of the detection hole) and falling pitch for long TC targets (the other side of the detection hole).
The hole typically occurs where the ground has a similar TC to the target, which will generate a poor or fluffy target response and a loss of depth.  

This can be simulated at home by using alfoil folded into a few layers and to end up at about 8” square. Put the detector on an outside table, with the coil in a vertical position and setup the detector as follows: MGB: 100; THS-B: 50; THS-A: 30; Gain: 1; Low Mode (e.g. the lowest Mode for your coil; I used 3 with my coil).



Bring the alfoil square up to the coil and note the response and detection distance. it will produce a falling pitch target response and I was getting about 14” with the 11” elite. If it produces a rising pitch, it’s too small, so start again and make your alfoil square larger.

Cut about 5 mm off of one end and retest. Keep doing this and at some point, the detection distance will start to fall and produce a wavering (fluffy) target response - this is the detection hole. Now cut off a very small portion and retest. Keep doing this until the target response once again becomes clear and positive, but this time it will be a rising pitch target response.

The QED detection hole is very narrow, but if you think that a target is in the ‘hole’, then change Modes and reground balance.

In the QED, changing the Mode moves the position of the detection hole (along the decay curve), thus will lift a fluffy sounding target out of the (previous Mode) detection hole.

A technique to ensure that nothing has been missed due to the ‘hole’ is to do a patch with a low Mode setting with a small coil, then switch to a large coil with a high Mode setting.

Most prospectors will never experience the detection hole, however if you do experience something akin to what’s described above, you now know what it is and how to deal with it.


Cheers Goldman


* alfoil test small.JPG (121.6 KB, 640x480 - viewed 29 times.)
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