Coil frequency change

[Kerimov]

Hello, is it possible to take a common DD coil (e.g. of DeTech) and change it's resonance frequency to be able to be used with another metal detector brand? I mean an additional circuit between the coil and metal detector with connectors. E.g. I have MD1 witch DeTech coil1 with frequency 10 kHz and I want to use this coil with MD2 (18 kHz and other connectors).

[Carl-NC]

In very narrow cases, maybe. But in general, no.

[Kerimov]

And how are DeTech Ultimates in this cas? Ultimate coil1 with lower freq used for MD1 to be changed to higher freq to MD2.

[Silver Dollar]

It depends where the tuning caps are.

On Tesoro's the caps are in the control box so one coil can work on a 10khz a 12khz
or 14khz detector.

I modded a Tracker coil (original freq 7khz) to 10 khz to work on a Bandito but that
involved going into the coil housing and cutting the tuning cap on the TX.

So you have to know the schematic a bit to see if it's possible and be willing to open
the coil if there's a cap in there.

From the outside you can lower the frequency but not raise it (as the capacitance
is greater with lower frequency)...

On the DeTech Ultimate I imagine you order it for a particular MD and they
build it with the proper caps for that one detector. You would buy another
one to use on a different detector...

[Kerimov]

And what about a possibility to have a black box with a "compensation" circuit between detector and the coil without the coil opening? Can it be done?

[Silver Dollar]

Doubtful, a metal detector coil is tuned to resonance. There are very tiny signals returned.
Any form of artificial tuning network will take away from the delicate functioning of the coil.

Now if you had a coil for the higher frequency machine and wanted to use it on the lower
frequency one you could most probably make that work..

[Davor]

You can of course put a coil of proper inductance in parallel and get somewhat higher frequencies, but it will have to be cored and dimensioned for enough voltage at the working frequency, and with a good Q factor. I is also common to find more harmonics with cored coils, especially if dimensioned too close to the core material saturation.