Why are TX and RX coils in many VLF IB designs not tuned to the same frequency?

[searchbear]

There is a fundamental question that I haven't been able to answer so far: Why are there so many designs in which the TX coild and RX coil aren't tuned to the same frequency? For example Tesoro double D: TX: 14.5 kHz RX: 16.1 kHz. Why is that? The phase shift created by metal objects could be detected...

[cristiano.sar]

Today I opened the bottom of my Tesoro Widescan 11"x8" coil
I removed a layer of a rubber like material (I'm not sure if its resin, but if it is, it is a little flexible) and between this layer and the other (the harder one that contains the coils), there is a thin layer of a carbon...

[cristiano.sar]

Does someone has a printable image/document with the shape with the exact dimentions of the TGSL DD coils?
Thanks!

[americanelliott]

I am designing a metal-detector for a senior project in electrical engineering. For the coil, I went with the VLF DD design in the Inside the Metal Detector book. We have an oscillator circuit that delivers 500mA at 10kHz (square wave) to the coil. The detection circuit amplifies the receive signal...

[mustafayilmaz]

Hi all,


I know it is difficult to make handmade coils with copper wire.


I am thinking of making a two layer pcb coil, I think the capacitive effect will be too much.


Coil dimensions will be 250x250mm and ~ 350uH. Serial and parallel connection...

[Jester]

Hi everyone. I was just wondering if anyone has any info on aluminium search coils?
Will they perform roughly the same as copper if the resistance and inductance is the same?
Any insight would be great.
Thanks.

[bishop_slayer]

I've looked at a few designs such as the surfmaster PI and they invariably use 12V. Is this purely due to convenience?
If a lower voltage of say 7.5V were used, according to electric laws the govern the rise of current in a coil, the MOSFET switch can be switched on longer in order to reach the...

[bishop_slayer]

Hi, I am planning to build a mono coil for a surf PI that has a diameter of around 10 inches. Are there any key factors that influence the depth? I am aiming for a coil inductance of around 400uH. Should I try and maximise or minimise the coil resistance? i.e. should I use thin or thick enamelled wire?...

[Polymer]

Thanks for posting this Carl! It supports what I am looking into. Made an extra thread as not to muddy green?s thread.

https://www.geotech1.com/forums/show...coil-at-Tx-off



Given a PI salt water coil ... hooked up to the MPP E. Mono Tx, figure...

[Tommy_sx96]

Hi there, I've recently built Baracuda PI, and it works very well with a mono coil I've built, 23 cm diameter with 0.5 mm insulated copper wire, 22 turns, about 392 uH, but I know this awesome circuit can give more. 😎

For now, I'm obtaining a sensitivity of about 10 ? 12 cm for...

[Polymer]

Wondering if my reasoning makes sense of maybe only having to shield the Rx coil?

Any thoughts, experience with this ... Thanks.

[Polymer]

I have measured two different coils @20 windings each.
One has "normal" insulation the other a very thick insulation.

I am somewhat puzzled by the results.
The measurements were made via resonant frequency.


Thin insulation:
650kHz with 150pF...

[Polymer]

I have looked at many ESD shielding sticky tapes in various widths.

One of them has a specified resistance of only 10? to 10E4 (1 to 10k).

The others all have very high resistances in comparison.

Might this be interesting for shielding a PI coil,
has someone...

[manhunt47]

Hello to all
I have some questions that I would like to thank for help


In general, there are two Rx coil coupling structures that are:


1) Parallel tank resonance circuit (TGSL and ELDORADO and RAPTOR devices)
2) series Tank resonance circuit (CIBOLA,...

[Alexismex]

a coil software practicle and also for Pcb
http://coil32.net/

[Tibuck19]

White's 8Inch Coil, its in Good condition, Selling for the price I paid. 75$CAN + Shipping






...

[Tibuck19]

Offering a Whites Bluemax 256 10inch widescan coil, New old stock in Box with hardware still in sealed bag. I'm basically selling for the price I paid for it. Asking 75$ CAD plus shipping.







...

[Tibuck19]

Personally I like this idea a lot for coil wrapping especially flat coils Share your thoughts.




https://www.youtube.com/watch?v=KP2G4fE0ssI...

[ionut_mtb]

Can someone clear this things up for me, please...

We need to know SRF of the coil only to find out the right dumping resistor OR we just use dumping tool with potentiometer and oscilloscope? With oscilloscope you can see also how fast it is.
Knowing SRF of a coil - is it good for...

[Polymer]

Found this picture of a RF? choke on the coil cable of a metal detector on the bay.

Since I have not seen this on coil cables before I am wondering if this
might help cutting down on EMI - or is it just wishful thinking?

Here's the pic: ...

[inductor]

hello,


i am looking for any information \ documentation on some older whites metal detectors.
i have a few units that i am trying to recondition and have found it hard to find technical information.


for example: digrams, the tuning pots on the circuit boards,...

[Tibuck19]

hey guys, could you all help me understand coil Uh more, say we have a 10 inch coil , what difference would a 300uH be compared to a 500uH will a 500Uh detect deeper?? or less?? or faster or slower? or will it just drain batteries faster? I know its a loaded question but not knowing has been eating...

[Tibuck19]

Happy Sunday, I thought I share a video I stumbled onto, may or may not be relevant to metal detector but still an interesting spider coil video nonetheless.


https://www.youtube.com/watch?v=H_cOD1QlUwA

[Tibuck19]

Coil shielding , opinions on MG Chemicals, Nickel vs Silver vs Carbon, Which would make the better shielding coating, for both PI and VLF coils. I know there is a lot of talk about scotch24 shielding tape but it is rather hard to get a hold of.

https://www.amazon.ca/MG-Chemicals-Con...

[Tibuck19]

Good evening Ladies and gentlemen, As some of you know I was tinkering with the Barracuda and also Polished off the Surf PI 1.2 that works like a charm with a fast 10inch coil, Now on too the MMP REV-D, I would like to make this one a GOLD hunter not only gold rings but more like a tinny gold nugget...