Help to diside to build a 25 khz coil

[Henrikras]

Hey guys..
I've (just) got this Deeptech Vista Gold ( 25 khz ), and I got both coils you can buy to this Detector. (11"rund and 8"x11"elliptical). If it possible I would try to build a 13" or 11"x13" coil, but I don't know where to start.
The resistor measureing with a universal instrument is; TX 2,7 ohm and the RX 2,1 Kohm...
I just wonder the 2,1 Kohm.! Is must Be a very long and thin cobber wire inside this coil. !
Any good adwise where to start... I got a osciliscope but not a tone generator, If that is needed.
Thanks in advance.
Henrik.

[Davor]

If your searching the web did not yield any idea, go to your dentist and negotiate best price for having an x-ray of your coil.

[Henrikras]

Thanks Davor.... In that case Maybee try to open one of my coils, If that is possible with a heather.
It could Be that there is some Electronics in the coil, likely minelab 705, and Thats the reason this 2,1 kilo ohm i measured.
Henrik

[Davor]

Don't risk it, go for some cheap x-ray. There is a chance you'll spoil balance of your perfectly good coil in a process of opening the coil.

[Henrikras]

You so correctly Davor. It just open it and it was Very Nice made, with a board and on that a 8 pin IC, some resistors and capacitor...
A small ekstra coil to finetune the TX, and all glued together. I take it as learning and properly in 4-5 years I can make a coil.
The TX was 2,4 ohm with 0,63 mm wire and the RX 17,2 ohm with 0,30 mm wire. If I am really lucky, the board still works, and I can try to make a coil. Thanks.
Henrik.

[Henrikras]

Trying had to do this. Allso to post pictures right...

[Henrikras]

I could take it apart, so the board came out...

[Henrikras]

Any idea or a guess what I should measure. ?
Coil inder diameter 145 x 215 (DD) and TX 2,4 ohm with 0,60 wire ?
And RX the same size 145 x 215 mm - RX 17,2 ohm with 0,30mm wire ?
It would Be a big help, If somebody has an idea what appoxly I should measure.
My plan is to build a larger coil, (13") the stock coil is 11", and I think that to get the same uH or mH, I must use one size up in thickens of cobberwire...RX 0,35 / TX 0,70 or stay 0,60. ! is that what you allso would do ?
If I dont got a instrument to measure the uH / mH, but I got a tonegenrator and a osciliscope, Anybody with a help to this LC formula to count out this...

I know that I am a newbie .. But trying hard to learn.
Thanks.

Henrik

[Biogas]

Hi Henrik! Have you issue whit the Depetech coil? If ok, please write me here, or pm! Thank you!

[Henrikras]

Oh my god this was written long time ago.. I've learned so much after that thread was written.
To your Questions I can answer a big NO but allso a little YES. - This is only concerning the Deeptech Vista GOLD - 25 khz.
The Round coil 10.5" and the large eliptical coil - AWESOME and working perfect. A little unbalance disc. at the eliptical at the front and the back... But that no Big deal. If you what the full depht the round one is it, and the eliptical is so sharpe.
The little NO is only concerning the small eliptical coil, but I'm not sure If my problem is the coil or something else ! Rosi is informed and I think he is looking in to this... My problem is - Coil perfect without Booster, but with Booster turned on, everything is iron after some few minuts searching out... Strange thing, indoor at 20-21 degrees ist not making the problem so fast. It got something with temperature to do. Low Temp. out side and 30 sec. the disc. system isn't working! Another new coil is excatly the same. Because nobody else got this small eliptical coil problem, I guess its my Vista Gold there got to much TX power.. Just Strange that both my Big coils are working Very nice, and I've have been out a lot with this Detector and done some Very good finds allso.
Hope that gave you some answers.
Henrik.

[Biogas]

Hello Henrik! Many thanks yours response! Can you give me the technical parameters the good coil? And what can you do whit the PCB? You build yourself a new, or, you build whit the factory PCB? Can you share photo about your coil? Thanx & Regards Biogas

[Henrikras]

Its long time ago this coil project. And only got what I can Remember. The 13" coil I tryed to make didn't work because I didn't knew enough about coil work at that time. To day I'm Very happy with the Stock coils and got no reason to make another coil to my VG.
So Sorry can't help you with any data. But If I should make a VG coil, the PCB from a Stock coil would Be needed, and to get that the 10.5" coil would the must easy way to get that.
Good luck with you project.
Ps. If you never had tryed the 10.5" coil, it a good idea.. Deep and Very stable. Less hotrocks signals and with Booster and full sens. no chattering.. But its a ugly coil, looks like its made in chech.rep. or east Germany in 1970..
Henrik.