Wanted "ADMIRAL"

[Deghbar613]

There is a rx 50k pot. Yes, you can fine-tune the ferrite from there. You know it will increase the depth

where put it it's not clear

[Deghbar613]

new PCB let's give it an other try

[Deghbar613]

... I have to admit that you guys caught me in a very strange but still good mood in that new year, so to be so active here, and to be inclined to share my humble experience, related to what I have accumulated as practical knowledge until now, related to VLF-portion of that hobby???
Rely on the same attitude from your end, if someone achieve the better results than mine... Deal?

DEAL

[getsa]

And, as an additional comment:
This MD works in the same way with Tx coil wound 45 turns - in that case the capacitor in paralel need to be 330nF to keep the same frequency.
Rx coil will also work pretty well with less turns - 125-130 windings. In that case maybe the coil will be less noisy, and less senzitive toward the soil? The only component that need to be adjusted is the capacitor 47 nF (in parralel of 15k resistor, connected to the Rx coil), so the point of the ground ballance potentiometer to be in the middle of the pot range (between 33nf and 68nf).

[getsa]

... I have to admit that you guys caught me in a very strange but still good mood in that new year, so to be so active here, and to be inclined to share my humble experience, related to what I have accumulated as practical knowledge until now, related to VLF-portion of that hobby???
Rely on the same attitude from your end, if someone achieve the better results than mine... Deal?

[getsa]

On one hand I can`t remember what exact wire diameter I have used for all of my admiral - and related to it clonings back in time. On the other hand - I only pay attention the wire for each search head`s coil to be: for Tx - 0,38-0,45 (the current is not serious), and for Rx - 0,25-0,28 (to be comfortable for soldering to the cable....). I realize that it is of a grat importance regarding the coil parameters, that have significant impact, such as wire diameter, the the amount of copper and the conductivity of the wire, the quality and number of insulating layers of the wire, the degree of tightness of the coil after winding, that result in inductance and Q value of the coils. One need to pay attention on that when make the search coil. But I`ve made the coils with a wire, taken from either transphormators, or from degaussing coils of TVs/monitors and the results were good (the older is the scrap - the better is the wire quality ). Not to forget the cable quality to be taken under consideration, as well as not to hurry when the blank/shell with the coils is poured with resin - it need to be done patiently, graduatelly, constantly controlling the signals on TP1 and TP2 (to keep the right signal amplitude/keeping the ballance, not allowing the oscillogrames to go into saturation.). Something like that - very practical and non-scientific advice...

[Op04]

Here you are - my custom PCB, who wants to repeat it and show results here.

Thank you

[gurdal]

I intentionally depicted the signals on TP1 and TP2 on the schematic I posted above - if you missed these details just see for reference.
On tl072 pin1 you have to see repeated Tx sine wave, with less amplitude, as a result of the coils ballance.

140 turns are relevant for 28 sm coil plastic shell - it referred to the diameter of the circle/circumference, on which one wind the coils (both coils), and diameter encompassed by the nails you use for frame the windings (for example) need to be 20 sm, so the coil to be accomodated in the shell normally. I haven`t measured the inductance - it depends on several factors. You just need to wind 140 turns on 20 sm blank for winding (same applies to the Tx coil, only need to be wind 60 w), after that the coil need to be tightened with thick thread and tape, as well as to be covered with aluminium foil for shielding (leaving a gap at about 1 sm foil uncovered coil space, avoiding short). Humble, simple, practicle explanation - hope I`ve been of help...
Of course, there are other important subtleties, that might have significant impact on the the overall performance of the device, but it is another story...

hello getsa,
What is the coil wire thickness you use for Tx and Rx?
Thank you

[getsa]

Here you are - my custom PCB, who wants to repeat it and show results here.

[Op04]

I intentionally depicted the signals on TP1 and TP2 on the schematic I posted above - if you missed these details just see for reference.
On tl072 pin1 you have to see repeated Tx sine wave, with less amplitude, as a result of the coils ballance.

140 turns are relevant for 28 sm coil plastic shell - it referred to the diameter of the circle/circumference, on which one wind the coils (both coils), and diameter encompassed by the nails you use for frame the windings (for example) need to be 20 sm, so the coil to be accomodated in the shell normally. I haven`t measured the inductance - it depends on several factors. You just need to wind 140 turns on 20 sm blank for winding (same applies to the Tx coil, only need to be wind 60 w), after that the coil need to be tightened with thick thread and tape, as well as to be covered with aluminium foil for shielding (leaving a gap at about 1 sm foil uncovered coil space, avoiding short). Humble, simple, practicle explanation - hope I`ve been of help...
Of course, there are other important subtleties, that might have significant impact on the the overall performance of the device, but it is another story...

A full detailed answer, I will pay attention to TP1&2. Your explanation will help a lot...many thanks!!

[getsa]

I intentionally depicted the signals on TP1 and TP2 on the schematic I posted above - if you missed these details just see for reference.
On tl072 pin1 you have to see repeated Tx sine wave, with less amplitude, as a result of the coils ballance.

140 turns are relevant for 28 sm coil plastic shell - it referred to the diameter of the circle/circumference, on which one wind the coils (both coils), and diameter encompassed by the nails you use for frame the windings (for example) need to be 20 sm, so the coil to be accomodated in the shell normally. I haven`t measured the inductance - it depends on several factors. You just need to wind 140 turns on 20 sm blank for winding (same applies to the Tx coil, only need to be wind 60 w), after that the coil need to be tightened with thick thread and tape, as well as to be covered with aluminium foil for shielding (leaving a gap at about 1 sm foil uncovered coil space, avoiding short). Humble, simple, practicle explanation - hope I`ve been of help...
Of course, there are other important subtleties, that might have significant impact on the the overall performance of the device, but it is another story...

[Op04]

At first glance everithing seem ok, instead the signal on tl072_pin1. There you should have pure sine wave.
Besides - what the signals on pins 4 and 15 /4053 look like? See what I mean on the schematic - TP1 and TP2.
Do you have a constant tone with the threshold potentiometer turned to maximum? - it depends on 100k trim setting.
My version of the board I'm currently playing with is different, but this is for experimentation...

Dear Getsa,
Thank you for sharing, I saw the video your result is very good,, can you tell us more spesific 140 turn at what diameter? TX RX inductance value? Will you share your current board? many thanks

[Deghbar613]

Unfortunately, based on your oscilloscope pictures, captured on tp1 and tp2, I am difficult to define correctly whether there is an objective reason you to unable achieving normal results with this MD (digital oscilloscopes do not quench the return beam, and I cannot estimate your particular setting conditions, based on the picture you posted). First you need to achieve clear sinwave on the first OpAmp. You might over ballanced the coils, trying to get minimal residual voltage. Unballance a bit until before the saturation point is reached and try how it behaves. For the proper schematic reaction and behaviour, you need to make sure by looking at the oscilloscope that the response to the ferrous target is phase, and to non-ferrous target is amplitude (check this on TP1 and TP2).

thank you gesta , I appreciate your help.
can you share with me some photos from your oscilloscope TP1, TP2, tl072 pin1 to make it as a reference

[getsa]

Unfortunately, based on your oscilloscope pictures, captured on tp1 and tp2, I am difficult to define correctly whether there is an objective reason you to unable achieving normal results with this MD (digital oscilloscopes do not quench the return beam, and I cannot estimate your particular setting conditions, based on the picture you posted). First you need to achieve clear sinwave on the first OpAmp. You might over ballanced the coils, trying to get minimal residual voltage. Unballance a bit until before the saturation point is reached and try how it behaves. For the proper schematic reaction and behaviour, you need to make sure by looking at the oscilloscope that the response to the ferrous target is phase, and to non-ferrous target is amplitude (check this on TP1 and TP2).

[Deghbar613]

At first glance everithing seem ok, instead the signal on tl072_pin1. There you should have pure sine wave.
Besides - what the signals on pins 4 and 15 /4053 look like? See what I mean on the schematic - TP1 and TP2.
Do you have a constant tone with the threshold potentiometer turned to maximum? - it depends on 100k trim setting.
My version of the board I'm currently playing with is different, but this is for experimentation...

hi getsa thx again and thx too to bonchev2 for videos in youtube i fellow its step by step but finally i need more videos to finish this admiral.i need your experiences ...
gesta i have constant tone with the threshold .
TP1

TP2

no lucky

please any help
Regards