field test unit no 001 "model T"

[Doug2]

Been Googling again Doug. Resonance???? Are you talking about PI and the coil in circuit????

What happened to your parrot cartoon here? How would you measure a Pi detector coil Q?

[Paul99]

The mathematical definition of Q of a circuit is 2pi times the ratio of the maximum instantaneous energy to the energy dissipated over unit of time corresponding to one cycle. ie Q=2pi X energy stored/energy dissipated per cycle. At the instant the max energy stored in the inductance of a resonant circuit the amount of energy stored can be expressed as1/2L(Imax)^2 where I= current and L= inductance . The amount of energy dissipated per cycle in the circuit resistance then is the product of R and the sq of the rms current times the period T of one cycle. Ie R(Imax/sq root2)^2/F since T=1/f Q may them be calculated purely in terms of impedance ie Q=Omega L/R. Note however that the real value of L can only be calculated when the distributed capacitance of the inductor is taken into account. It should be noted that reducing the distributed capacitance and the proximately effect not only increases Q but results in improved antenna efficiency which is exactly one of the benefits of spider wound coils compared to bundle wound coils something the parrot is obviously unaware of!

Been Googling again Doug.

Resonance???? Are you talking about PI and the coil in circuit????

[Doug2]

Is that the Q-factor of the coil you are talking about the following relationship? Q = XL/R = w*L/R = 2*pi*f*L/R, where f = 1 kHz (measurement frequency), L = coils inductance R = coils resistance Q = 2*pi*1000 * 300 µH/0.4 Ohm = 4.7 (Yep, it must be.) ^sif

The mathematical definition of Q of a circuit is 2pi times the ratio of the maximum instantaneous energy to the energy dissipated over unit of time corresponding to one cycle. ie Q=2pi X energy stored/energy dissipated per cycle. At the instant the max energy stored in the inductance of a resonant circuit the amount of energy stored can be expressed as1/2L(Imax)^2 where I= current and L= inductance . The amount of energy dissipated per cycle in the circuit resistance then is the product of R and the sq of the rms current times the period T of one cycle. Ie R(Imax/sq root2)^2/F since T=1/f Q may them be calculated purely in terms of impedance ie Q=Omega L/R. Note however that the real value of L can only be calculated when the distributed capacitance of the inductor is taken into account. It should be noted that reducing the distributed capacitance and the proximately effect not only increases Q but results in improved antenna efficiency which is exactly one of the benefits of spider wound coils compared to bundle wound coils something the parrot is obviously unaware of!

[Doug2]

I see you are doing your usual and never answering any questions put to you Doug, and as usual your reply is a question.

What happened to your parrot cartoon here?

[Aziz]

... but he was talking about making ~40 per day and selling the things for 100 bucks each on Doug's forum.

40/day * 100 bucks = 4000 donald ducks/day (stress, stress, stress -> making expensive)
8/day * 500 bucks = 4000 donald ducks/day (you have less stress)

You fire yourself and hire 5 ducks ->
8/day * 5 ducks * 500 bucks = 20,000 donald ducks/day (you are going to make the donald duck dynasty)
Not bad... I should go this way rich *LOL*

^sif

[Aziz]

Is that the Q-factor of the coil you are talking about the following relationship?
Q = XL/R = w*L/R = 2*pi*f*L/R, where
f = 1 kHz (measurement frequency),
L = coils inductance
R = coils resistance

Q = 2*pi*1000 * 300 µH/0.4 Ohm = 4.7
(Yep, it must be.)
^sif

[Paul99]

Can you list the commercial coils have you measured the Q of and what the Q value was? Can you then tell us which of these coils will or won't run on the various ML models? Basket or spider wound coils are more efficient rx antenna;s than an equivalent sized bundle wound! The reasons should be obvious to you!!!!!

I see you are doing your usual and never answering any questions put to you Doug, and as usual your reply is a question.

[Doug2]

Doug, Does Q as measured with an RF Q meter indicate if a damped PI coil will work and does this figure truly represent Q for a damped PI coil? Do you know how JS measured Q? And Doug, look at Kev's figures for the Minelab stock DD. TX-Q= 5.29, RX-Q= 0.152 Note the very low Q for the higher resistance RX coil?? Where does this leave your argument regarding high Q basket weave being a better RX antenna for PI?

Can you list the commercial coils have you measured the Q of and what the Q value was? Can you then tell us which of these coils will or won't run on the various ML models? Basket or spider wound coils are more efficient rx antenna;s than an equivalent sized bundle wound! The reasons should be obvious to you!!!!!

[robby_h]

You would not have known this if Kev had not told you!!!! LOL!

Doug,
Does Q as measured with an RF Q meter indicate if a damped PI coil will work and does this figure truly represent Q for a damped PI coil? Do you know how JS measured Q?

And Doug, look at Kev's figures for the Minelab stock DD.

TX-Q= 5.29, RX-Q= 0.152

Note the very low Q for the higher resistance RX coil?? Where does this leave your argument regarding high Q basket weave being a better RX antenna for PI?

[Doug2]

I quoted you Kev because I know the 3.9 figure doesn't universally apply, but Doug obviously doesn't now this.

You would not have known this if Kev had not told you!!!! LOL!

[Doug2]

This may have been the case with early GPs and the 5k but it is not necessarily so with the 3k5, 4k and 4k5. Some Q's for you Minelab stock DD TX-Q= 5.29, RX-Q= 0.152 Coiltek 14x9 Goldstalker Mono Q= 4 Coiltek 18x12 Goldstalker Mono Q= 3.78 Nugget Finder 14x9 Mono Q= 5.5 (yes that's right 5.5 and its a fantastic coil!) That 14x9 Nugget Finder is the most sensitive coil I've ever owned, it will get gram+ bits deeper than the 18x12 Coiltek and smaller sub gram bits deeper than the Coiltek 14x9. Often 0.05g bits up to an inch in caliche. I have built coils up to a Q of 5 and they have worked very well, not as good as the NF though. I aim for a Q of 4.5 to 4.8 Because Moodzs detector is not a Minelab he can engineer whatever coil parameters he so desires Kev.

Kev the coil I tested worked fine on a 3000,3500 and some SD's and another person ran it OK on his 4500.

[robby_h]

This may have been the case with early GPs and the 5k but it is not necessarily so with the 3k5, 4k and 4k5.

Some Q's for you
Minelab stock DD TX-Q= 5.29, RX-Q= 0.152
Coiltek 14x9 Goldstalker Mono Q= 4
Coiltek 18x12 Goldstalker Mono Q= 3.78
Nugget Finder 14x9 Mono Q= 5.5 (yes that's right 5.5 and its a fantastic coil!)

That 14x9 Nugget Finder is the most sensitive coil I've ever owned, it will get gram+ bits deeper than the 18x12 Coiltek and smaller sub gram bits deeper than the Coiltek 14x9. Often 0.05g bits up to an inch in caliche.

I have built coils up to a Q of 5 and they have worked very well, not as good as the NF though.
I aim for a Q of 4.5 to 4.8

Because Moodzs detector is not a Minelab he can engineer whatever coil parameters he so desires

Kev.

I quoted you Kev because I know the 3.9 figure doesn't universally apply, but Doug obviously doesn't now this.

The shape of the coil decay curve at the first sampling point determines if a coil will or won't "work" (fire up) when connected to a fixed TX/RX circuit and I think most here know what can influence this shape. The Q is only an indicator if the designer considers the capacitance, something you would do but a novice might not.

One 3rd party 14" mono has 0.6 ohms resistance and yet it was everyone's favorite until other sizes appeared and another not so successful coil had 0.9 ohms resistance. Some coils had metal screens and were very noisy and others dropped the TX coil inductance. These all "worked" on ML detectors.

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.

Moodz's detector appears to rely on excess ripple thus breaking pulse induction's main rule and so of course he can engineer whatever coil parameters he so desires and that would be okay... but he was talking about making ~40 per day and selling the things for 100 bucks each on Doug's forum.

[Kev]

I should give up but....
I don't know what the coil Q was but was told it was substantially more than the miserable 3.9 you quote (a member here said Q higher than ~3.9 won't work, how did you address this?)
You should wear floaties when you jump in the deep end Doug.

This may have been the case with early GPs and the 5k but it is not necessarily so with the 3k5, 4k and 4k5.

Some Q's for you
Minelab stock DD TX-Q= 5.29, RX-Q= 0.152
Coiltek 14x9 Goldstalker Mono Q= 4
Coiltek 18x12 Goldstalker Mono Q= 3.78
Nugget Finder 14x9 Mono Q= 5.5 (yes that's right 5.5 and its a fantastic coil!)

That 14x9 Nugget Finder is the most sensitive coil I've ever owned, it will get gram+ bits deeper than the 18x12 Coiltek and smaller sub gram bits deeper than the Coiltek 14x9. Often 0.05g bits up to an inch in caliche.

I have built coils up to a Q of 5 and they have worked very well, not as good as the NF though.
I aim for a Q of 4.5 to 4.8

Because Moodzs detector is not a Minelab he can engineer whatever coil parameters he so desires

Kev.

[Aziz]

Stupidity before malice! It is stupidity and fear that rules the world, not malice and bad intentions.

That is really interesting Davor.
Do you really think, that the coil designers were totally stupid? *LOL*
^

[Aziz]

I got it this time!!!!!! A simple proof!!!!! The spider wound coil must go deeper! There is an apparent depth advantage visible!!!!
Yeah!, I'm smart! I'm ultra-ultimate super smart!!! I'm super-duper genius!!!! I'm a real coil guru!!! *LOL*

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^²

Ok guys,

forget the above so-called "depth advantage". That was a nice trivial joke of course.

Assume, that we have the same vertical thickness for both coils. So no apparent depth advantage will be there anymore. For the sake of fairness and to make Robby_H happy of course.

That's a very interesting case now.
Which coil will do better?

^sif