field test unit no 001 "model T"

[Aziz]

....
In my opinion, Spiral, basket and spider are just methods to obtain lower capacitance, nothing more, and are probably more suitable for the low Q coils used in most projects here.

Now forget the lower capacitance and Q-factor Robby_H.
Does a bundle coil or the Moodz coil will induce a stronger magnetic field?
Does a bundle coil or the Moodz coil will induce a stronger target response?
^

[robby_h]

The potting resin has a dielectric that varies between 2.8 and 4.5 whilst solid Teflon is 2.0 ... Foam being lower depending on type and density. So Kev has a good point.
However I will also add a caveat that what has not figured in all these discussions is that coil q is far more Dependant on ac ESR than any single factor. Since some here are so good a googling ....of you go now to look this up. LOL

Some might think your coil could have similar capacitance to a bundle wound coil if the dialectric was high enough.

It's worth noting that Doug never queried the dialectric or DC resistance or insulation or any effect the shield might have on a relatively flat winding. He promoted your coil simply because you are a member of his forum. If you were a member of 4umer he would have torn your design to shreads and I can imagine his questions if someone from 4umer made the same claims he made for JS's coil. He would demand a truck load of proof, six videos, 5 onus's and at least 4 reviews by Pierre.

Doug has turned this argument re Q into a farce. PI theory as taught on this forum requires a low Q tx coil to supposedly ensure that switch on eddy currents don't cancel those generated at switch off. Minelab use a high Q tx coil in part to ensure a substantially linear coil current growth, and a low Q DD rx coil for transformer coupling to the target. A high Q tx also gives best bang for your buck in that we can get a higher field strength with lower voltage. In my opinion, Spiral, basket and spider are just methods to obtain lower capacitance, nothing more, and are probably more suitable for the low Q coils used in most projects here.

[robby_h]

Granted Robby, this is undoubtedly true in a number of situations.

This NF though gets the little ones so the decay must be fast enough, and the ripple is taken care of by matched damping. It is not particularly noisy in bad ground but.......the caveat is spelled out below.
I believe it is the dielectrics performance of the foam former they use, combined with sufficient loop/shield space that is the critical part that makes this coil so good.

Fully pot a high Q coil (4.5+) though and it will most likely no longer work on a Minelab.
Fully potting Moodz coil may also hobble its performance markedly.

The caveat is poor or offset ground balance in highly magnetic ground.
Thankfully where I detect there's not much of it because while ground balancing, the 4500 groans and moans like an 80 year old woman clawing her way out of bed in a morning.
Moodz I believe, has a "new" method of GB which could negate this major hurdle in using a Higher Q coil?

Kev.

There is nothing worse that wandering around suffering ground noise with a supposedly magic 3rd party coil only to discover the noise doesn't exist with a properly made coil. Most people don't even know this problem exists and usually blame the detector.

Some "apparent" ground noise is caused by ripple and in another case eddy currents induced in the coil itself. Testing for coil eddy currents isn't always easy because of ML's high gains but it can be a bit easier in Enhance or FG because these timings compensate for other noise also caused by changes in inductance.

If the coil is okay then you should get very little or no response if you pass a suitable sample of non-VRM magnetite or ferrite over the coil. Some ground noise can't be cancelled though because the response is unpredictable.

Moodz's method appears to measure changes in the coil's properties. If so then this has been tried many times before. I think it also has been suggested that auto damping can some how help cancel the ground response but this isn't possible.

[moodz]

The potting resin has a dielectric that varies between 2.8 and 4.5 whilst solid Teflon is 2.0 ... Foam being lower depending on type and density. So Kev has a good point.
However I will also add a caveat that what has not figured in all these discussions is that coil q is far more Dependant on ac ESR than any single factor. Since some here are so good a googling ....of you go now to look this up. LOL

[Kev]

The most sensitive coil isn't always the best though if that sensitivity is because the decay curve has ripple at the first sampling point.

It is interesting to note that one manufacturer's early coil shows no obvious ripple but their latest does! Very sensitive but noisy on bad ground.

Granted Robby, this is undoubtedly true in a number of situations.

This NF though gets the little ones so the decay must be fast enough, and the ripple is taken care of by matched damping. It is not particularly noisy in bad ground but.......the caveat is spelled out below.
I believe it is the dielectrics performance of the foam former they use, combined with sufficient loop/shield space that is the critical part that makes this coil so good.

Fully pot a high Q coil (4.5+) though and it will most likely no longer work on a Minelab.
Fully potting Moodz coil may also hobble its performance markedly.

The caveat is poor or offset ground balance in highly magnetic ground.
Thankfully where I detect there's not much of it because while ground balancing, the 4500 groans and moans like an 80 year old woman clawing her way out of bed in a morning.
Moodz I believe, has a "new" method of GB which could negate this major hurdle in using a Higher Q coil?

Kev.

[Aziz]

Coil Model Exported To Antenna Modelling Software (NEC)


Is this looking better now?


The NEC-file:
CoilCMP4-mono-spider6-18inch.nec.zip

Forgot this nice feature... *LOL*
^

[Aziz]

Hey guys,

have you collected enough donald duck bucks to fund the results yet?
I want to flee to Australia next time. I need lots of bucks...
*LOL*
^

PS: I need more bucks for the lots of barrels of tarr and feather too... collect more please...

[Aziz]

I just had a email from a bloke who has known Aziz for years. He says every time Aziz puts a "LOL" in his post it means he has no idea what he is talking about. Suits Aziz to a T

This is from Aziz old post on antenna design in Turkey

*LOL*
^

[Aziz]

Hey Ufox, I'm using WARP 9 electrons!!! *LOL*

Remember the quiz-game. So what is better?
^

[PATCHES JUNIOR]

I just had a email from a bloke who has known Aziz for years. He says every time Aziz puts a "LOL" in his post it means he has no idea what he is talking about. Suits Aziz to a T

This is from Aziz old post on antenna design in Turkey