Equinox Transmission & Reception

[cjc]

On 3/8/2019 at 8:22 PM, Chase Goldman said:

Congrats on the 50th here is a DP page with a number of resources that explain the basics, theory, physics and technology behind metal detectors.  HTH

 

Here is the Equinox Essential Information Thread:

 

Here is a link that explains Multi IQ

https://www.detectorprospector.com/magazine/best-of-forums/minelab-multi-iq-technology-details-explained/

Chew on that awhile and if you have more questions than check back.  TBH - As an engineer myself and tech geek, I think you may getting yourself into the weeds too soon on the theory of operation stuff and it appears you might have the wrong mental model of receive and transmit as far as a metal detector is concerned that may be a source of confusion for you.  You are looking at it more like RADAR and it is more closely coupled like a transformer (see discussion below) because we are talking about detecting small changes in magnetic fields not reflected radio waves where there is little influence between the transmitted and received signals.  I would separate your intellectual curiosity about how the detector works from understanding how to operate the detector save for a few basic concepts.  But to delve a little bit into this, the detector is basically acting like a big transformer with a transmit coil (which one "D" the left side of the coil loop) as the primary and a receive coil (the other "D" on the right side of the coil loop) as the secondary and the target acting as the "core" of the transformer and the most "sensitive" region of the coil loop being the center "spine" of the coil loop where the two "D"s overlap in a back-to-back fashion .  Different metallic makeup of the "core" (target) will cause the electric signal passing through the transformer system to be altered in ways that can be measured such that the target shape and electromagnetic properties such as conductivity and inductance can be inferred and passed on to the user as visual and audible target information.  The transformer analogy as I described is incomplete and imperfect but it gets the idea across, hopefully.

Multifrequency helps better cancel/account for ground effects and enable the different transmission and excitation properties associated with different frequencies to be simultaneously applied to the target.  Higher frequencies excite lower conductors like like gold, aluminum, brass, and lead and small targets better but cannot penetrate as deeply into the ground.  Lower frequencies penetrate deeper and excite high conductors like silver and copper and high mass objects  better than high frequencies.  Ferromagnetic targets like iron have different, known. response properties than non-ferromagnetic targets and can therefore be readily identified and discriminated.  There are drawbacks to multifrequency operation, two of the biggest being, minimizing transmission power loss to extent practical (the transmit energy has to be divided between individual frequencies if you are actually transmitting them separately and simultaneously, rather than using more elegent methods such as square waves, pulse width modulation, or other methods to take advantage of harmonics that are produced when two or more signals of different frequencies are combined) and the processing power required to extract the information from the received signal.

Equinox also brings adjustable, fast response to the table (known as recovery speed) which helps with being able to detect multiple targets in close proximity to each other.  But as is true with all aspects of detecting, there is no free lunch.  Run recovery speed too high and deeper target signals will begin to become clipped such that you may not be able to hear them with the practical effect that you are actually reducing detecting depth.  Run recovery too low in an attempt to increase depth, and you risk increasing ground noise because of the need to swing slower to get a good signal whichnis also counter optimal performance.  For the 800, the sweet spot for recovery speed is around 4 to 6 leaning a little on the high side.  There are more in depth discussions of recovery speed on the Equinox Essentials thread page I linked to above.

One of the mantras I use to optimize Equinox setup is to stay as close to the defaults as I possibly can and to maximize the signal to noise ratio.  Avoid doing things that raise the noise floor along with signal sensitivity (like cranking sensitivity too high or lowering recovery speed too low as mentioned previously).

Let me know if you want to go into the different properties of the various modes (Park 1/2, Field 1/2,. Beach 1/2, etc.) and what conditions and targets they are optimized for.

HTH to get you started.

Chase

Great rundown and instruction, Chase.  I especially like the part about letting the machine operate within its pre-set parameters.  Very good advice.  Thanks clive

[Chase Goldman]

1 hour ago, cjc said:

Great rundown and instruction, Chase.  I especially like the part about letting the machine operate within its pre-set parameters.  Very good advice.  Thanks clive

Thanks, Clive.  On my to do list this summer is cracking open your second Equinox book and getting a chance to put your advanced theory to practice at tge beach and elsewhere.

[cjc]

As much as M/L wants to portray the EQ as "turn on and go" these machines with a complex, highly processed (modulated) signal are finicky and there's a fair bit to learn in order to get consistent performance--especially around salt.  Keeping the Sens within a manageable range is the only way to really learn the machine.  Another good method is to crank it and get used to picking responses out--then when you turn it back down the audio is easier to recognize especially the faint range. cjc