Adding tones to Raptor

[h9361]

You've already found that increasing a gain can cause stability problems. To compensate for that, you might also have to reduce the bandwidth.

I have no idea how the Relic Striker is getting better depth. Maybe they are running a much higher TX current, you could try that by reducing R1. The big coil also helps, use a 40+ cm coil on the TGSL. Finally, the relic striker runs at 4.8kHz and using a lower frequency will help with high conductors.

Getting more depth out of a circuit isn't easy. If it was, the person who designed it would have already done it.

I tested TGSL for lower frequency, but my audio tone will be changed and it is not good.
Do you have a solution for this ( i want to use 4.8KHz)?

[Carl-NC]

Add a separate audio oscillator like Raptor has.

[h9361]

Add a separate audio oscillator like Raptor has.

Thank you.
Is it possible to see attached and tell me your opinion?

[Qiaozhi]

I also built TGSL project, it also has a low sensitivity.
I remember that i tested the relic striker metal detector, its sensitivity is very very high! I think the Relic schematic is like Raptor or TGSL ( analogue mode).
I tested a coin from 41cm using its 18x15 coil. In addition, i tested it with a Steel tray (45cm diameter), it detects from 195-200cm distance!
None of Raptor and TGSL can reach such depth!
I attached TGSL schematic, is it possible to suggest me some point for palying it?
In TGSL schematic, i increased both 470K to 1.5M. My sensitivity increased but not such Relic. I also tested it with two 2.2M, but its stability was very very bad.

When you state that the TGSL and Raptor have low sensitivity, I think you really mean the detection distance is less the the Relic, which is not the same thing. The Tesoro-type detectors both have excellent depth, iron rejection, and target separation.
I highly suspect that these are air tests, and the reality will be somewhat different when tested on real ground.

[h9361]

When you state that the TGSL and Raptor have low sensitivity, I think you really mean the detection distance is less the the Relic, which is not the same thing. The Tesoro-type detectors both have excellent depth, iron rejection, and target separation.
I highly suspect that these are air tests, and the reality will be somewhat different when tested on real ground.

Thank you dear Qiaozhi.
Yes, high Air distance and high penetrating to ground are completely different.
Dear Qiaozhi, a question has engaged my mind.
I tested many Commercial VLF detectors.
According to my result, there is a big difference between TGSL/raptor and the Commercial detectors in Target detection speed!
Do you have any idea for increasing the lower speed?

[Qiaozhi]

According to my result, there is a big difference between TGSL/raptor and the Commercial detectors in Target detection speed!
Do you have any idea for increasing the lower speed?

What do you mean by "speed"?
Do you mean the speed of sweeping the coil,?

[h9361]

What do you mean by "speed"?
Do you mean the speed of sweeping the coil,?

Reactivity or recovery time.

[Carl-NC]

Recovery speed depends on the BW of the circuitry AFTER the demod switches. For example, the differentiators in Raptor have a roll-off at 10-11 Hz. Try speeding these up by reducing the caps. However, this can reduce depth and make the detector noisier.

[h9361]

Recovery speed depends on the BW of the circuitry AFTER the demod switches. For example, the differentiators in Raptor have a roll-off at 10-11 Hz. Try speeding these up by reducing the caps. However, this can reduce depth and make the detector noisier.

thank you.
Is the cap that you mentioned?

[Carl-NC]

C14,15,24,25

[h9361]

C14,15,24,25

Thank you dear Carl.
I have a request, Is it possible to guide me how to add a threshold Audio pot in TGSL schematic?
I think it should be near R43/R44, but i do not know how add it.
Thank you.

[h9361]

C14,15,24,25

I added Threshold pot (attached), do you think it is correct?

[Carl-NC]

That will work but I think it will only add a fake threshold level and will not help with sensitivity. TGSL is designed for silent-search disc-only, there is no all-metal channel to drive the audio which is what you need for adding an effective threshold. The Bandido II circuit is a good example. If you have ITMD3, then the VLF-Disc design also shows how to do this, and it also shows a way to do 2-tone audio.

[h9361]

That will work but I think it will only add a fake threshold level and will not help with sensitivity. TGSL is designed for silent-search disc-only, there is no all-metal channel to drive the audio which is what you need for adding an effective threshold. The Bandido II circuit is a good example. If you have ITMD3, then the VLF-Disc design also shows how to do this, and it also shows a way to do 2-tone audio.

Thank you dear Carl for your schematic.
Has the Bandido II schematic any PCB design?
I am going to build it and to compare them.
Thank you.

[Carl-NC]

I don't have a PCB design, maybe there is one on the forum.