Coils for the QED

Ok, it sounds like somethings up with either the detector or the coil. Ill pop back to Wiltronics this week - fingers crossed it its an easy fix.

It sounds like there is a problem somewhere besides the ground. Such a high GB does not seem normal. Using a Sadie in my area usually requires a mode of 3 whereas my 12" x 6" X coil is very happy on 1. I can also run gain much higher than with the Sadie. The response on my test speck (.1 gm) with the Sadie is slightly better than the X coil, but the X coil has far better depth on larger bits. What really surprised me was the response of the 15" round X coil on the speck, which was very positive, and on a 20 cent piece the 15" X was only a fraction less effective than a GPZ with the 14" standard ML coil. Tests were in ground and not air tested.

Mark, whats your null?

Id start off by doing a factory reset. Run your B at null for the interim. A at 50. Start off with a mode of about 5. Do a ground balance. Keep in mind the QED only likes a nice SLOW up/down from just above the ground to about 150-200mm above. Now you can work toward bringing back your mode and gain till where it draws the line in being stable. Bring back up the gain till its quiet or the next mode. Re ground balance. With your A at 50, you should be able to drop your B a few steps easily. Actually when you get to this point recheck your null. Find how far either side of null your A of 50 will allow. It should be a reasonable number. Iff you go too far either side of null, it will be noisy. Most of the time i run my A up around 70-80. Less if i want to get further away from null. A at 50 should give you another notch or two with your B. After 15-20mins recheck your GB and null. Its not unheard of for the unit to change its null or GB.

Waiting for good videotests :Y:

markrich73 said:

Ok, it sounds like somethings up with either the detector or the coil. Ill pop back to Wiltronics this week - fingers crossed it its an easy fix.

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How'd you get on with this Markrich?

The AGB often goes way too far, especially if you lower the coil too much or too fast. I believe this has to do with the recovery time of the detector.

I never AGB - only manually ground balance. 291 is crazy high but Ive seen AGB result in a number like that when I moved the coil too close to the ground - this results in a very wrong GB.

Keep in mind that this is a fundamentally different kind of detector than minelab - not necessarily better or worse, but it just operates in a different way and with very different settings. You need to operate it in the QED way just like you operate a minelab in the minelab way.

Another vote to do a factory reset and then MGB if you havent gotten to your brick and mortar shop yet...

Your dealer will help you out regardless, great customer service for the QED and a very capable machine.

Aussiedigs, I am in the process of putting together a test patch on my property (on which I have detected gold) and will be able to post some comparisons with not only different coils, but also different detectors. I will post results as they become available.

Just a quick update on my misbehaving QED. Howard very kindly took a look at it during the week and found a dry joint on one of the components on the Rx side of the PCB. He resoldered it and the machine is now behaving properly - I haven't had to ground balance above 170 in any of the spots I've been to since and I'm now digging the shotties I missed over the last couple of weeks (but no more gold sadly). Many thanks to Howard - he was super generous with his time, energy and know-how!!

markrich73 said:

Just a quick update on my misbehaving QED. Howard very kindly took a look at it during the week and found a dry joint on one of the components on the Rx side of the PCB. He resoldered it and the machine is now behaving properly - I haven't had to ground balance above 170 in any of the spots I've been to since and I'm now digging the shotties I missed over the last couple of weeks (but no more gold sadly). Many thanks to Howard - he was super generous with his time, energy and know-how!!

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Good result Markrich!
Bet that Sadies a tad more sensitive now :Y:

Howard has a heart of gold, a genuinely nice gentleman, and a bloke who has integrity.

I still haven't got the EMI situation sorted out on the Sadie. I can't seem to calm the wobbling threshold and spurious spikes in the areas I've been detecting regardless of mode, gain and SMR settings. This has quite an impact on its sensitivity to small gold. How do the Coitech Commander 8" and 11" Elite compare? Are there any other coils less susceptible to EMI?

I just went out into my home paddock (street power lines 25m away & HV transmission lines 200m away) and with GB 125-130, THSB null, THSA 60 Gain 8 mode 1 for Sadie & gain 6 mode 2 for 14 x 9 evo, The Sadie was very usable - just a spike every 30 sec or so & the Evo was sl chattery & spike every 15 sec or so. Still usable, just not perfect. Both picked up 1 grain no prob.

For EMI rejection a bundle wound coil like Sadie should be better than than full spiral wounds ( Elite, Evo). Also the bigger the coil the better the antenna so all else being equal a 6x8 should pick up less EMI than a 8 round or 11..... and way less than a 20

Are you sure it is EMI? - If you have set THSB null and THSA say 30 & hold the detector rock steady coil on ground or horizontal ie coil way above ground does it still carry on ? If still spurious noises then ok, sounds like EMI. Do you have powerlines very nearby? If not then Hmmm....

I wouldnt be looking for the solution in a new coil just yet. Do you have any remoter spots that you would be sure have no EMI that you can check out ?

Is SMF at the preset of 50?
SMR preset of 107?
If not reset them to the preset values & try again.
The QED is fairly EMI resistant as far as PI detectors go but not totally immune to it.
With a small coil & no abnormal EMI you shouldn't need to play with those settings much if at all.

A big coil/big swings may need some SMF adjustment or if near off frequency 50hz power lines, microwave towers, 2 way radio transmissions or similar EMI sources then some SMR adjustment may reduce them.
Unfortunately neither is a magic bullet in rejecting bad EMI & won't help at all against natural/atmospheric sources i.e. lightning storms that could be hundreds of km's away.

If EMI is indeed the cause & SMR adjustments do not help then I doubt a change of mono coil will help.
You could try a DD coil or anti interference coil but they also come with some loss in sensitivity. Back to square one.

I doubt that the issue is with the coil. Either you have a nearby EMI source that SMR isn't helping with (electric fence, phone tower, air traffic, HV powerlines etc.) or there could be further issues with it?

Hmmmm..... something still sounds squiffy. SMF was at 50 and SMR at 107. No powerlines, electric fences or air taffic close by today, but there were a few houses within a 1 km radius. I did about 10 factory resets to try and figure it out, but the threshold warbled all over the place regardless of what I did. I was in a valley last night where it ran slightly quieter, but it still didn't give a clean threshold.

I'm hitting smaller targets than I was previously, but it's tough going!

Is it possible that your mobile phone and/or pinpointer are causing the interference?

I've been turning my phone off and I don't have a pinpointer.

Wish I had another coil to test - one of those X Coil 6x12"s would be just the ticket right now.

SMR - preset is 107 as you know. I have played with that a bit and have found that in my area setting it at 100 is better. I can't remember which but 104 or 105 makes it go nuts. Worth making your way through a few numbers to see if anything helps.

What is your Null markrich?

And what are you running your Gain at? I had issues getting my Gain beyond 2 or 3 before it went mental. Sent back to Howard (stupidly I waited for too long before doing that). He re-did all the solders and it fixed it perfectly. Can run Gain 6-10 now depending on coil and where I am.

Cheers, N.E.

Thanks Northeast - it's great to hear you got it sorted. Null on my machine is 45. I was running gain 5, mode 1 today, although it didn't seem to matter if I raised or lowered gain or mode - it ran super noisy in all of them. I'll see if Howard might have another looksee...

Mark, are you sure your null is at 45? Not impossible but does seem to be a little low. Too far below null will give you noise. Recheck GB and null after 20 mins of run time.

Hey Aussiedigs, yeah null is definitely 45. Howard recalibrated a few things last week after resoldering the dry joint and it changed from 50 down to 45 in the process. I'll ask him to bump it back up to 50 if he's got the time. It's not a huge issue, but the usable window of THS B values has narrowed, so I now need to be quite precise when setting it. I've been constantly checking null as I'm going.