Coil Frequency

[Danno]

I was listening the other day to C-Scope talking about the new Evo-6000. They said they opted for single frequency operation with the coil set for one frequency as it is better as it resonates at it's design frequency, in this case 17khz. They did say there will be option coils to change the frequency higher or lower but this will mean purchasing a new coil to change frequency.

Is this truly the best way to achieve the best sensitivity at a given frequency or are they just holding on to old tech.

There are other makes of detector that you can change frequency with the same coil (Deus, ORX, Kruzer, Anfibio, Nox etc) do these machines have a set resonate frequency matched to the coil which offers best performance and do they lose sensitivity if you change frequency? Or is there a way of making the coil sensitive to a range of frequencies.

Just wondering why they chose to go a different route to others on the frequency selection?

[SilverSurfer17]

I’m no expert by any means but from what I read I know they make the MD’s for all around use not a specific metal that’s why they have sweeping ranges but can be tuned to what you are looking for I’m in Illinois I don’t ever expect to find gold coins but a lot of silver I’ve read that 5 kHz is for silver so I’ll build mine around that

[Carl-NC]

There are other makes of detector that you can change frequency with the same coil (Deus, ORX, Kruzer, Anfibio, Nox etc) do these machines have a set resonate frequency matched to the coil which offers best performance and do they lose sensitivity if you change frequency? Or is there a way of making the coil sensitive to a range of frequencies.

There is an argument that, for a given frequency, there is an optimum coil inductance (or, rather, optimum parametrics that result in that inductance) that will produce the best sensitivity. But in reality, a broad range of inductances (or parametrics) will produce practically equal results. Consider all the single-frequency detectors being made and what a vast difference in coil parametrics they all have, yet they all have very comparable depth.

The last select-a-coil detector was the Minelab X-Terra series. They have now been replaced by the Equinox and Vanquish series, both of which have selectable frequencies using a single coil yet still outperform the X-Terra. In detectors like the Equinox & Vanquish that are also multifrequency there is no coil resonance, it is square-wave driven. In the XP, the coil is resonated but when you change frequencies it switches in a different cap to change the resonance.

[SilverSurfer17]

Nice explanation !