DIY TGSL STEP BY STEP BUILDING AND TESTING

[Ozoz_xba]

you have to know if you put a copper into a coil then the inductivity of coil will decrease. its famous effect much people do not
understand (whole their school time was wasted on the girls) and do not want understand. so if you will measure a coil you get wrong data.
we have the table with data of manufactured coils but all that is MEASURED DATA, NOT REAL.
if you see '5.5mH' there you have to do 6mH.
it is simple rule you have to follow for VLF coil.

also, if you put ferrite core inside a coil you will get INCREASING of inductivity, you see - THAT IS MIRROR EFFECT to above with copper.

I have now a new 2 coils and hope that them work..tx is about 6.180mH and rx is 6.5mH

https://ibb.co/qJ1r5qJ

https://ibb.co/cbMqHLw

By the way if i put a copper inside a tx if the signal on scope dont change?

[Ozoz_xba]

I put now the coil tx and rx my frequency in tx is 17.8khz and rx 17.4khz....the tx signal is not prefect maybe as i see from scope... is the tx and rx khz normal or should i take some wire from tx?in previous i put tx and rx ib mHenry.
At this frequency i get max (after max nulling arranging GB)1 coin at all mode 20cm 16cm prefect noise..what to do ... is possible to get 1 coin from 30 cm at good noise in all mode?

https://ibb.co/HY12h7G

https://ibb.co/fSSN7dv

[Ozoz_xba]

I cant measure the 14.5khz frequency on tx.it was 17.8khz and after calculation i need about 7nf more in to get 14.5khz frekuency .i put an 6nf parallel to 22nf but frequency gone just 16.8khz or something like that...what to do to change it any help please...on lrc metter my tx is 6.180 mH ....(after putting the capacitance pallalel and trying to nulling rx ,the rx not on board looks like had 0.9vac it was not more millivolts)was that normal?

[Ozoz_xba]

My coils also is 13.7 cm one of them, both it makes 23-24cm ,maybe maybe should i make my coils at last both 35cm to get deph at 35 cm 1 coin?
Also 1 coil should be 6.2mH?or 8 or 9mH for 35 cm both coils?

[Ozoz_xba]

I have make a coil and tx i have arranged it to 14.6khz ...but i cant arrange the rx...as i trying to arrange the 16.1khz but after nulling the s8gnal is not so good to get the frekuency.....should i arrange rx frequenxy before nulling ,tx and rx in board away from each other?1 have 1 chanel scope only... another question the discriminate 100k pot is for sensivity arrangment or not????
Any reply will be helpfull thx

[dbanner]

The Rx frequency will be same as tx frequency when it is connected to the circuit.
The 16.1khz is the calculated RESONANT frequency with Rx coil inductance and 15nf cap.
You must measure the Rx inductance and make appropriate calculation of capacitor value for 16.1 khz resonant frequency.( You may add or subtract from 15nf according to the calculation. Remember to measure the ACTUAL inductance of the Rx. Do not trust number of turns.
However, the signal the Rx actually receives when it is working in the circuit will be the same as the TX frequency(14.5khz)

[dbanner]

Step 1: measure Rx coil inductance
Step 2: use resonance calculator to get value of capacitor needed for 16.1khz resonant frequency.
Step 3: choose a capacitor closest below calculated value, adding small values in parallel to get closest to calculated value.
Step 4: proceed to balance coils.

[dbanner]

To measure the resonant frequency of your receiver coil, you must make small coil tester circuit. But it is not necessary. Once calculation is correct, there is no problem.

[kt315]

Step 2: use resonance calculator to get value of capacitor needed for 16.1khz resonant frequency.
---
in the arsenal of possibilites we have the especial LC coil tester. it gives resonant frequency directly.

https://www.geotech1.com/forums/showthread.php?24500-coil-generator-tester-of-coils

[Ozoz_xba]

Thx all for helping me.i have build the concentrix coil .first rx and puting it in tx arranged at 13.9khz.after made tx at 14.6khz with buvking coil.in air i can get 1 euro at 29 cm.rx is about 9cm diameter and tx 30 cm.

https://vimeo.com/350350919

Thx in advance...
I will think about shielding...but how?

[nonkapo]

Quick question about the coil. Is there on the market coils for this detector(originalor aftermarket) as I'm overloaded at the moment and prefer to order one online, rather than spending time in experimenting and setting up? Also what about their cost? I google but seems only for the newer Tesoro models there are coils available or most of the time no one sell coil only but complete setup. Thank you.

[dbanner]

Quick question about the coil. Is there on the market coils for this detector(originalor aftermarket) as I'm overloaded at the moment and prefer to order one online, rather than spending time in experimenting and setting up? Also what about their cost? I google but seems only for the newer Tesoro models there are coils available or most of the time no one sell coil only but complete setup. Thank you.

There are a bunch of tesoro coils on eBay right now, most of which are compatible.

[nonkapo]

Thank you. I have one more question. Will BF256B work here instead of BF245C? I've compared them and see only a bit of difference in the ON characteristics, but as on the board is printed exactly BF245C i have some doubt?!?!?

[dbanner]

Any FET which cross references to NTE 133(use NTE cross reference online). Can be used. Any general purpose Nchannel FET.
So yes, bf256c can be used.

[nonkapo]

Huh, just before i solder them i check the polarity and despite all the datasheet showing source in the middle, these one are with the drain in the middle (pin2)?!?!?!?. Good that i verify...