RELIC HAWK

[Max]

Hi,
still problems... with disc stuff... seems impossible to find a point where I can null iron!

Let me explain... I've made a number of tests changing the coil phase to look for the perfect balance of TX/RX phase to a value that will give the nulling on ferromagnetic component... till now nothing.

Now the stuff is even more interesting cause other stuff work... about as expected, but the dang disc still won't work.

I think this coil is a very critical piece... much more than others already made, something that need extreme care on details.

Kind regards,
Max

[Max]

Qiaozhi read this...

Hi Qiaozhi and all,
today I tested again for alignment between rx coil and tx coil to get right behaviour from geb/disc stuff...

Now I'm doing this way...

I'm monitoring the RX signal at output of preamp, and at same time the control signal at geb and disc gates.

I found that the middle of control pulse for geb occours at zero-crossing of RX signal in a particular position: this I've found at geb pot cursor at middle.
In this position of RX coil I couldn't get minimal voltage, but detector still works all-metal as always, as well as disc-mode about range.

In this, same, position of RX coil I get , when knob of disc pot is about at middle the middle of control signal of disc gate exactly at signal minimum, at top of back sinus, just before signal rise again.

Following usual thoughts the geb sample at zero-crossing... the disc sample at peak (negative peak in my case) of signal... all as expected... so maybe this is the right positioning for rx coil ???

TX/RX phase shift is about 180° at this position.

The effects: on ferrite toroid I get a strange behaviour: at few distance, 2-3cm I get absolutely no signal... but at 10-12cm I get broken beeps, not random ones but due to ferrite, always!
Can detect e.g. copper good way... so seems good about this.
Iron stuff, similar to ferrite, is often ignored on short distance... but give broken beeps and cracking sound when higher... also 15cm and more from coil (this with an hammer head, pure soft iron).

So... disc somehow works... but bad. Why all this complication about it ???
Problem is that the beeps on ferrite and iron signal there's a problem there , but where ???

I have to say that my coil is not exactly flat at this time...but RX coil is somehow bounced over the large TX coil... thus the plane of RX is tilted of at least 3° from the plane of the bottom TX.

What do you think ? Must trash it and buy a coiltek ???

PS: Qiaozhi... about sampling at zero-crossing you mean that middle of control pulse must happen to be when rx signal is just zero-crossing, right ? Or do you mean something different ? I ask you cause the pulse is about 180° wide... so it's a bit complex to say where it is sampling...

Kind regards,
Max

[Qiaozhi]

PS: Qiaozhi... about sampling at zero-crossing you mean that middle of control pulse must happen to be when rx signal is just zero-crossing, right ? Or do you mean something different ? I ask you cause the pulse is about 180° wide... so it's a bit complex to say where it is sampling...

Kind regards,
Max

Exactly correct. Since the output of the sample gate goes through a low-pass filter, the signal will be averaged over time. If the sample pulse is centered at the zero-crossing, then the result will be zero. Any metal that passes near the coil will cause a phase-shift that will produce an audio response.

[Alexismex]

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[Max]

Exactly correct. Since the output of the sample gate goes through a low-pass filter, the signal will be averaged over time. If the sample pulse is centered at the zero-crossing, then the result will be zero. Any metal that passes near the coil will cause a phase-shift that will produce an audio response.

Hi,
thanks for the answer, so I saw it right on the scope. What do you think of the broken beeps at higher distance ?

Could that be related to the odd shape of the coil ?

Kind regards,
Max

[Max]

Hi,
some wire arrived ...so I've made a new TX coil with 0.56mm diameter (bare) wire... and 3.5ohm resistance... to try if works now, with mods on transistors... and it works, I mean, oscillator runs good BUT this just using BC337, BC327 there.

(btw also my old 0.50mm coil works now with them in oscillator)

Unfortunately frequency I've got is not as required but lower... but this is unimportant in thoughts about oscillator startup.

So, the problem at oscillator we can consided as solved. So I'm updating schematic with new labels for transistors as required.

Here revision 1.8.

Kind regards,
Max

[Max]

bulgarian RH schematic again

Hi,
I've spotted another difference between this (complete?) schematic and the bulgarian version called "relic hawk I", look at "f" point... that goes to pin1 of 4024...

don't you notice anything different ???

The 4024 gets its clock from geb/all-metal control signal, but in our RH schematic the "f" is at disc gate control signal...

So... someone could say... ok , it's always 5Khz there...

Sure... but I don't think is the same getting clock at 90° more or less ? Do you ?

In an extraordinary hi gain device...like THIS IS... that 90° could make lot of differences...

Kind regards,
Max

[Fred]

Hi,
I've spotted another difference between this (complete?) schematic and the bulgarian version called "relic hawk I", look at "f" point... that goes to pin1 of 4024...

don't you notice anything different ???

The 4024 gets its clock from geb/all-metal control signal, but in our RH schematic the "f" is at disc gate control signal...

So... someone could say... ok , it's always 5Khz there...

Sure... but I don't think is the same getting clock at 90° more or less ? Do you ?

In an extraordinary hi gain device...like THIS IS... that 90° could make lot of differences...

Kind regards,
Max

Well done Max,
This is an interesting difference,mostly with he discrimination problem .You just have to connect F to pin 6 instead of 5 of 4066.
BTW, the bulgarian version pin7 of 4066 is wrong, should be 8.
regards,
Fred.

[strujas]

I think that oscilator will be much stable if you use 2n4401 and 2n4403 instead bc237 and bc337
Regards

[Max]

I think that oscilator will be much stable if you use 2n4401 and 2n4403 instead bc237 and bc337
Regards

Hi,
thanks for the hints... I haven't them handy... but if could find some I will try.

Kind regards,
Max

[Max]

the "f" line...and detector behaviour

Hi,
this post to explain what I realized from getting the "f" from the geb control signal:

detector is more quiet...than before...

Also, before I made that change the movements on disc pot, even in all-metal mode, gave variations in random chatters and the like...

Now what I think:
have no sense to me using the disc path to get the "f" signal... cause the disc pot rotation change the phase of that signal respect to the transmit signal at TX coil, that's reference.
Have much more sense to me that the "f" is get from geb path, instead, cause once you tuned device on soil you'll not touch the knob anymore, unless you change soil (e.g. move far apart in the field, that require new geb fine tuning): this is expecially true when using disc mode... where you're expected to move the disc pot... thus resulting , as in schematic we follow, in a variation of the phase at every disc pot movement that could imbalance detector and cause erratic behaviour.

My conclusion is... people who made the bulgarian schematic on page1 know about the exact connection of the "f" line, so they followed that scheme. People who made the complete schematic probably don't know or mistaken about the "f" line connection... or intentionally faked schematic there. I don't belive ML could have made such a stupid mistake connecting the "f" at disc control signal.

What do you think ?

Kind regards,
Max

[KingJL]

My conclusion is... people who made the bulgarian schematic on page1 know about the exact connection of the "f" line, so they followed that scheme. People who made the complete schematic probably don't know or mistaken about the "f" line connection... or intentionally faked schematic there. I don't belive ML could have made such a stupid mistake connecting the "f" at disc control signal.

What do you think ?

I agree. But since you are going to move the souce of 'f', why not source it from U6 pin 1? That way no changes to GEB or DISC will have an affect.

Regards,
J. L. King

[Max]

I agree. But since you are going to move the souce of 'f', why not source it from U6 pin 1? That way no changes to GEB or DISC will have an affect.

Regards,
J. L. King

Hi,
yes, good observation... but you probably forget a thing... I think ML put the line there cause of a reason:
do not interfere much with true signal path and give compatible signals where required

Let me explain... I think that if you bind the "f" there... so connect the pin1 of 4024 with pin1 of U6 you'll get troubles...

Why ? Simple, the 4024 expect a CMOS input level there.

You actually don't know which voltage there is at pin1 of U6... cause depends on TX coil voltage... but it's really difficault you get there a CMOS compatible level of voltages... so it's like playing dice there... sometimes could work... but it's unreliable unless you pay attention on that voltage... if don't use a level shifter etc

So, the actually made the easy way: used a comparator that acts as level shifter and it's triggered at zero crossing. This is a truly safe way of doing it.

Kind regards,
Max

[nakky]

Hi Max,Ivconics RH LIGHT from 4024/1 to lm393/7 to 4066/13.Grt Nakky.

[KingJL]

You actually don't know which voltage there is at pin1 of U6... cause depends on TX coil voltage... but it's really difficault you get there a CMOS compatible level of voltages... so it's like playing dice there... sometimes could work... but it's unreliable unless you pay attention on that voltage... if don't use a level shifter etc

So, the actually made the easy way: used a comparator that acts as level shifter and it's triggered at zero crossing. This is a truly safe way of doing it.

However you want to do it, but the output at u6 pin 1 is at cmos compatible level, < +- 5.5V (actually it is about 5-6 vpp).

Regards,
J. L. King