Making a Bigfoot?

[bklein]

I want to make a Bigfoot coil, for an excal to start with, later other detectors.
I’ve been searching and collecting data on them, but let me start out by asking a basic question: what is the best way to optimize the design of the TX coil? Each model detector has its unique frequency and drive characteristics - how do you tweak the coil design to match it best? Something you look at with a scope? Resonance you tweak with added passive components? Sense with a remote sensor of some sort? I have the test equipment to make various measurements, see current waveforms, etc. to compare with a standard coil but I want to know how its done when you are starting from scratch.

[kt315]

a basic answer.
exal is elite in schematic, same. a coil has preamp board inside. this board is not released. you got primary info to run.

[bklein]

I have seen threads that show a preamp circuit that supposedly allows making your own coils with it for the excal/sovereign. I want to do the same for the CTX and Equinox but those I may have to try removing the board from a Minelab coil as they probably use a micro for security. So those will be worked on later. The board circuit does fullwave rectification of the tx to develop power for the RX preamp circuit. I imagine my question stands for whether you want a TX coil for a single frequency or multi frequency detector. Like if you were ambitious and wanted to do a coil to sense small gold, how would the TX coil design change if at all?

[kt315]

multi frequency detector
---
do we have to open new dispute club again that there is not multik pultik frequency? lying. or we believe every marketing way ML does for idiotic people without
electronics base knowledge to get the overprofit? for every cent of profit a capitalist will chump the throat of a competitor.

[bklein]

How about answering my questions about optimizing a TX coil for a detector?
I don’t care which you use for an example except don’t make it a pi (for now).

[kt315]

ready optimizing. just must get it for the autopsy in my hands.

[bklein]

Two different coils in your photos though, correct? The “slice” photo looks like a cut of the middle as you can see the missing shaft tang in the distance. Making me think I will never be able to salvage a board from an equinox or CTX coil. Even the “autopsy candidate” excal coil I have is epoxy-saturated like yours.

[kt315]

you need my archive. i see that guy. you can do fantastical things then.

[kt315]

epoxy-saturated
---
ahaha! direct hands only amigo! DIRECT RIGHT HARD HANDS! you are looking for just the causes to do nothing. Tolianych must give you American people all those secrets! LOL!!!

[Hyena]

Now - I doubt that this is an opamp, divider or some other specialised IC, because then will be too easy to reproduce those super secret coils, where is half of electronics in coil (as greedlab claims) or it is just some simple & cheap but not readable PIC/Atmega?

[kt315]

russkie rebiatushki did draw a schematic of this secret board. opamp in 5 pin case. chipo at left is a micro. set this board in terra box, do a coil
with only preamp and you do not need ML coil never.

[Hyena]

Do you have a link please? Its hard to beleive that chip is there only to fool people like me

[Carl-NC]

That looks like an XTerra board, they have a micro embedded. Sov/Excal do not.

I want to make a Bigfoot coil, for an excal to start with, later other detectors.
I’ve been searching and collecting data on them, but let me start out by asking a basic question: what is the best way to optimize the design of the TX coil? Each model detector has its unique frequency and drive characteristics - how do you tweak the coil design to match it best? Something you look at with a scope? Resonance you tweak with added passive components? Sense with a remote sensor of some sort? I have the test equipment to make various measurements, see current waveforms, etc. to compare with a standard coil but I want to know how its done when you are starting from scratch.

Excal is a simple square-wave drive but with a fundamental of 3kHz, so I would expect the critical thing is to keep the TX coil resistance low. There is no resonance cap for TX, and surely not for RX either. Somewhere there is a schematic for the coil PCB.

[Qiaozhi]

Somewhere there is a schematic for the coil PCB.

Please see attachments.

[Carl-NC]

I was thinking of the Sov/Excal coil PCB, there is a schematic floating around.

In the Xterra schematic "LTC6" is a top mark and probably is "LTG6", which is an LT6202 and a very appropriate choice for a preamp.