Tarsos detector vlf turkey

[mehdi]

A 20" diameter coil is 508mm in metric. This means the coil radius is 254mm not 500mm, as you have entered in the dialog box.

oh bad mistake
any way; again:

10'' coil:
Tx=60 turn of .25 mm wire = .176mH
RX=90 turn of .25mm wire = .375mH

and for 20'' coil:
Tx= 38 turn of .25mm wire= .176mH
Rx= 57 turn of .25mm wire= .379mH

TRUE?!!

[Qiaozhi]

Hi Don
thanks a lot.
kt316=2n4920
kt817=2n4923
kt315= cant find it, please help
what is this? ((Tx coil = 2.5 nF Rx coil = 5 nF)) since the calculate software dont need those!!!?
please see the image, is it true for 20'' DD coil?!
RX=14.128mH
tx=6.87mH

A 20" diameter coil is 508mm in metric. This means the coil radius is 254mm not 500mm, as you have entered in the dialog box.

[mehdi]

You can use the values below and calculate backwards for a 20" coil size.

Tx coil = 2.5 nF
Rx coil = 5 nF

With the above values, you will need 65 nF to tune your Rx coil.
(I think that my Rx coil is actually 4.6nF.) It doesn't matter that much though, as long as you get close to 5nF and tune your Rx coil with a correct capacitor value .

Hi Don
thanks a lot.
kt316=2n4920
kt817=2n4923
kt315= cant find it, please help
what is this? ((Tx coil = 2.5 nF Rx coil = 5 nF)) since the calculate software dont need those!!!?
please see the image, is it true for 20'' DD coil?!
RX=14.128mH
tx=6.87mH

[dfbowers]

Hi dear Don
do that please and calculate 20'' coil for me if it is possible and give me the formula of calculate. other thing; can i use polyester to make the loop substitute epoxy?
and can i use any other transistor substitute KT315 , JT816 , KT817; because i cant find them!!
thanks a lot
mehdi

Mehdi,

You can download and use Qiaozhi's coil calculator here:
http://www.geotech1.com/forums/showthread.php?t=15678

Let me know if you can get it to work.

I already posted a full parts list with substitutes for KT315, KT816 abd KT817 in post # 121 of this thread, so please take another look.

You can use the values below and calculate backwards for a 20" coil size.

Tx coil = 2.5 nF
Rx coil = 5 nF

With the above values, you will need 65 nF to tune your Rx coil.
(I think that my Rx coil is actually 4.6nF.) It doesn't matter that much though, as long as you get close to 5nF and tune your Rx coil with a correct capacitor value .

As far as using polyester, I have no idea what you have there. It might work. BUT if it's a fast cure resin it will probably shrink and spoil your coil null!!

Also if it's fast cure, it will most likely get very hot with a large mass!!! AND.. can melt your coil shell!!! (I already made that mistake)

It could very easily ruin you entire coil project so it would be best to go with a slow cure potting compound.
You can get details on potting epoxy here:

http://www.geotech1.com/forums/showthread.php?t=16651

Good luck!
Don

[mehdi]

Hi dear Don
do that please and calculate 20'' coil for me if it is possible and give me the formula of calculate. other thing; can i use polyester to make the loop substitute epoxy?
and can i use any other transistor substitute KT315 , JT816 , KT817; because i cant find them!!
thanks a lot
mehdi

[dfbowers]

Hi mehdi , dfbovers, porkluvr, ...
i want to build a metal detector for finding treasure underground so what is better for this; volksturm sm or delta pulse or surf pi?
delta pulse is hard to build and if volksturm can almost rivalry with it so it is better for me. wath is your opinion?

I have a lot of respect for the Surf PI. Depending upon your level of experience, your odds of being successful are definitely with the Surf PI, especially if you can aquire a "kit" from Silverdog. Plus, making the coil is much more forgiving and offers a lot lf flixibility in terms of coil size!

Volksturm is quite a challenge when it comes to building a coil for sure! It works wonderfully though with the GB addition.

Maybe one of the other guys can answer your question about te Delta Pulse as I have not built one (yet)..

[dfbowers]

Hi dfbowers
how can make 20'' DD coil?( turn and wire dia ) and how tune it for more depth detection for big object?
is it true for 20'' coil:
TX - 30 turn .25mm wire
RX - 45 turn .25mm wire?
regards
mehdi

I think that it is possible to make a 20" coil " but take into consideration that an IB coil must be made extremely rigid or you will get false signals when it flexes. AND, it would be very heavy! If you are really serious about building one, I can measure the inductance of my 10" coil and you can calculate what you would need for a 20" coil.

[silver]

Hi mehdi , dfbovers, porkluvr, ...
i want to build a metal detector for finding treasure underground so what is better for this; volksturm sm or delta pulse or surf pi?
delta pulse is hard to build and if volksturm can almost rivalry with it so it is better for me. wath is your opinion?

[mehdi]

Hi dfbowers
how can make 20'' DD coil?( turn and wire dia ) and how tune it for more depth detection for big object?
is it true for 20'' coil:
TX - 30 turn .25mm wire
RX - 45 turn .25mm wire?
regards
mehdi

[dfbowers]

for example 1m*1m metal!!
and big coil for sm ...?
thanks a lot

Not sure.. But I would imaging that you could make a large DD coil, like 18" or so.
Would not a PI detector with a 1M x 1M frame do the same thing? The Volksturm SM is just a single channel anyway, so best to just GB and run all metal.

[silver]

for example 1m*1m metal!!
and big coil for sm ...?
thanks a lot

[dfbowers]

how much maximum depth can detect volksturm for big object?
can we use mono coil for this project?
and how can make big coil for volksturm sm?
thanks

What is a "big" object? Soda can or car?
No, you cannot use a mono coil since this is IB.

[silver]

how much maximum depth can detect volksturm for big object?
can we use mono coil for this project?
and how can make big coil for volksturm sm?
thanks

[mehdi]

thanks a lot Don and Porcluvr for your help. i understand and i will use your geb mod in my project dear Don.
regards
mehdi

[dfbowers]

Hi dear Don
thank you very much for help me.

****...There are capacitors on the parts placement diagram that do not show on the schematic. If you have been building for a while you will recognize them as bypass capactors on the OP AMPS. You can use 10n or 100n, I can't remember which ones I used,)))
where are those capacitor?!
there are two shematic of geb version; your geb addition and kt315 geb addition. please see the below shematic and my pcb: can i use this two addition together on my project ?
regards
mehdi

Yes, you can add both GEB mods to your project but you only need one. I could not get the proper range of adjustment with KT315s GEB mod so I added my own.[/quote]

Mehdi,

The bypass caps do not show on the schematic but show on the parts placement. When you begin to populate your PCB you will find pads with nothing to match on the schematic and no values listed. I was a little confused at first when I built m project as well. (I built 3 pcbs!!) In doing a little reading elsewhere I concluded that they were bypass caps (as you will find on many other projects). In researching, I found that 10n - 100n are common values used.

Hope this helps.

Don