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...

[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,...

[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...

[Panchito]

Hi, this is my first post, although I've been reading these forums for some time.



I thought I understood the basic principles of a vlf metal detector. You provide an alternating voltage in one coil and read the induced voltage on a secondary coil. You measure the phase shift...

[Tibuck19]

Hi everyone, I am getting tired of digging up pulltabs and nails haha as you can all relate too im sure, I contacted silverdog to see if he had any kits that do discrimination (board and all the components ) as of now, he does not, I have made a few fully working Surf Pi's and a minipulse plus, I...

[SasuG]

Hello, I tried to understand how can discriminate in this schematics and i don t understand very well, I have the article that was put on this forum, I studied it but i didn t understand exactly what it works.[COLOR=rgb(33,33,33)] If anybody who can explain me in a few words how can discriminate this...

[giuhalftrack]

Hi, anyone have the wilson 710 schematics ?

I have search this forum but i have collect only some picture of originale PCB without part list.

I'm willing to build this machine and post results on this forum.

needed:
part list
pcb

or at...

[alcalde55]

Hello,
I am currently changing my career and starting a new company, for which I need funds so I am selling things I will not use anymore. That is why I wanted to ask you guys if anyone new the market price of a used ABEM WADI VLF instrument (aprox. 20 years old). Any information would be helpful,...

[pelanj]

I need to search a relatively small piece of land to find small silver and copper coins amongst larger pieces of iron (nails, screws, horseshoes). The easy ones have been picked up already by others. I think there are some more, not necessarily deep. Nobody likes to dig iron, me neither. Someone mentioned...

[david]

Hi, everybody,

I am a new guy in this field of hand-held hobby-type metal detectors. I have some shallow knowledge about the units. I think that VLF metal detectors is easier to understand than PI. The VLF metal detector often has two coils, which are named as TX and RX. The circuit...

[FreezonePK]

Hello Geo Community,

I am an young engineer in training in North America and decided to tackle my first metal detector. Me being nieve, I chose to use VLF detection. I have encountered a few roadblocks in building a coplanar coil. I am on my third attempt on nulling and tuning the coil...