RELIC HAWK

[Max]

doing tests...

Hi Qiaozhi,
I'm doing tests... still seems everything nice... I will draw a plot of results when finish them and post here to see if everything is like expected or not.

I think the plot kind is the best for giving such informations... but I'm a bit puzzled by target to use.

I'm using now a silver coin, an hammer head (soft iron) and a small gold ring but don't know if are good or consistent kind of targets ... I see amplitude variations there... will plot them soon.

Kind regards,
Max

[Max]

The small distortion you have indicated in the TX waveform is really insignificant, and will have no effect whatsoever on the discrimination. The cause is most likely some nonlinearity in the oscillator. Nothing to worry about.

It is very difficult to debug this problem remotely. Have you probed the signal along the DISC channel, as you wave ferrous and non-ferrous targets in front of the coil? If you first try to monitor the output of the DISC sample switch with both target types, then you don't even need to move the target, as this will be a non-motion response at this point. The differentiating circuitry is further along in the channel. Try plotting the amplitude versus distance for both ferrous and non-ferrous.
If this looks ok , then we can eliminate the problem being located in the sampling circuitry.

Hi,
ok...so we can exclude the small non-linearity at oscillator as cause of the problem with disc.

I'll do that way using scope on strategic points... then will report about results.

From what I see I will expect the signal will rise or fall with non-ferrous and ferrous metals there. I've checked before and seems it's ok... but I need look again at output of the sampling gate to report accurately.

Kind regards,
Max

[Qiaozhi]

Hi,
yes, it's what I think too... testing such kind of stuff is really easy for those who have it handy... just measure for dc voltage.

Now my puzzle of the day is about TX signal shape... cause I noticed a small... really small distortion at sine wave on tx signal... probably due to the oscillator itself or coil.

The distortion in a bit flattened part of sinus at top positive right end of signal... look at picture to have an idea of it... I didn't take a picture from scope but the distortion is similar to that from this bad simulation.

The question is: could this so small distortion cause such strange disc behaviour ?

Qiaozhi (and all) what do you think about ? Too distorted stuff can lead to disc fault ?

Kind regards,
Max

The small distortion you have indicated in the TX waveform is really insignificant, and will have no effect whatsoever on the discrimination. The cause is most likely some nonlinearity in the oscillator. Nothing to worry about.

It is very difficult to debug this problem remotely. Have you probed the signal along the DISC channel, as you wave ferrous and non-ferrous targets in front of the coil? If you first try to monitor the output of the DISC sample switch with both target types, then you don't even need to move the target, as this will be a non-motion response at this point. The differentiating circuitry is further along in the channel. Try plotting the amplitude versus distance for both ferrous and non-ferrous.
If this looks ok , then we can eliminate the problem being located in the sampling circuitry.

[Max]

MAX , I do not own a Relic Hawk . But it would be nice if someone could test what models of Minelab have a low voltage dc on the RX coil wires. This will tell us if the Relic Hawk needs the Preamp circuit in the search-coil for proper discrimination , or not ????? I thought I saw a photo on this forum of a 15 inch minelab coil that did not have a pre-amp ???Anyway , I am still looking for a "Relic Hawk" to buy where I live , and then many of my questions will be answered..........Again Just some ideas , ......thanks........Eugene

Hi,
yes, it's what I think too... testing such kind of stuff is really easy for those who have it handy... just measure for dc voltage.

Now my puzzle of the day is about TX signal shape... cause I noticed a small... really small distortion at sine wave on tx signal... probably due to the oscillator itself or coil.

The distortion in a bit flattened part of sinus at top positive right end of signal... look at picture to have an idea of it... I didn't take a picture from scope but the distortion is similar to that from this bad simulation.

The question is: could this so small distortion cause such strange disc behaviour ?

Qiaozhi (and all) what do you think about ? Too distorted stuff can lead to disc fault ?

Kind regards,
Max

[amtech2005]

RELIC HAWK

MAX , I do not own a Relic Hawk . But it would be nice if someone could test what models of Minelab have a low voltage dc on the RX coil wires. This will tell us if the Relic Hawk needs the Preamp circuit in the search-coil for proper discrimination , or not ????? I thought I saw a photo on this forum of a 15 inch minelab coil that did not have a pre-amp ???Anyway , I am still looking for a "Relic Hawk" to buy where I live , and then many of my questions will be answered..........Again Just some ideas , ......thanks........Eugene

[Max]

I don´t think there will be much inside the coil, we already have the oscillator and preamp on our schematic.
They could be on a separate board in the coil, but i doubt it will make much difference on discrimination.

Max, i asked before, but did you try to adjust you coil so there is a slight offset on null that will not give you a negative shift with iron far away?
regards,
Fred.

Hi,
tryed so many times...but no success... the coil you can position in many different offsets/nulls also higher than usually and detector still works good but I put phase in a way I can then ground balance using the trimpot ot external 10turns pot.

When GEB balanced it ignores ferrite at 5cm and even less but not as smooth as in TGS and BandidoII ... it's a wildcat I think... don't like you near ferrite too much!

Anyway, using disc then... it ignores big iron stuff at few cms but then it sounds at far distance!

I had similar problem at BandidoII but that time was a wrong capacitor value... so wrong phase shift at demodulator... BUT our schematic is right, right ? Or I must expect some capacitor value is wrong there ???

Kind regards,
Max

[Fred]

I don´t think there will be much inside the coil, we already have the oscillator and preamp on our schematic.
They could be on a separate board in the coil, but i doubt it will make much difference on discrimination.

Max, i asked before, but did you try to adjust you coil so there is a slight offset on null that will not give you a negative shift with iron far away?
regards,
Fred.

[Max]

Somebody can scan a coil in some hospital.. , and to post photo here and we will know if something is hidden

Hi,
yes, it's a good idea... I think could be something there that make this puzzle so difficault...

for example in the sov coil picture provided by Nakky there's a ne5534 smt + an lm394 supermatch pair...

Sure detectors are different but... who really knows what's inside the big RH coil ? Is just wire... or there's more... like some phase network + amplifier and the like ?

Real puzzle!

Kind regards,
Max

[strujas]

Somebody can scan a coil in some hospital.. , and to post photo here and we will know if something is hidden

[Max]

unsolved disc mess...

Hi,
I've made lot of tests these days... but found no solution.

The fact is that device responds in disc mode also to iron at far positions...and seems pretty few sensitive to attempts of correcting that behaviour.

I don't think original device could be sold that way... with such an explicit iron detection in disc mode: impossible.

I was thinking the mistake seems or could be related to response speed of disc channel enable/disable output signal... but so far... no results from changing caps etc, still problems there.

Also tryed to change op amps to see if slewrate modification could impact the effect or not in a positive way... but found very similar results with slew rates up to 50V/us... that's enough to me as test and seems lead to nothing useful there.

So it's still a mistery and I hope someone could post pictures or give informations to solve the puzzle according to original ML design.

I also started thinking that original coil could have something hidden (e.g. a small circuit + some additional coil) to prevent such ferrous signal to be amplified further... but I cannot be sure of this... I haven't RH or a RH coil... cannot do anything to confirm these suspects.

Kind regards,
Max

[Max]

BTW PayPal sux, no buyer protection or anykind of this sh**
I lost 420$ because of them, so guys just watchout from being screwed, don't expect any help or assistance from Paypal (Paypal and ebay are the same company!)

yes... I agree... they aren't safe at all!

But now better stop the off-topic and focus again on RH.

Kind regards,
Max

[Max]

Hi Max,
Not to extend too much this OT , i think all the Paypal refund issue could be ruled out if the seller have a proof of sending, or a tracking nº....
and this problem could happen in the same country the same way,to be abroad or not changes litlle i think.This is where feedback is important.
BTW, Italy has a very poor reputation about post office,i feel sorry for Italian ebayers that have to pay more than others ....
regards,
Fred.

Hi,
not just Italy has these troubles, also Nigeria and some middle east countries along with some e.g. central asian countries suffer from similar troubles...bad reputation about postal service there and not only...long delays at customs and other funny things... it's clear why some sellers prefer staying with domestic transactions... in these cases. But some are even more scared and wanna domestic always!

Sure I understand those "special" cases...

But I remember I was searching for a Tesoro 8'' donut-coil and I saw a true bargain price but seller was from Belgium and I cannot get the dang coil cause he wanna made domestic transaction only! absolutely crazy!
No way to convince him... nevermind.

Kind regards,
Max

[eclipse]

BTW PayPal sux, no buyer protection or anykind of this sh**
I lost 420$ because of them, so guys just watchout from being screwed, don't expect any help or assistance from Paypal (Paypal and ebay are the same company!)

[Fred]

Hi Max,
Not to extend too much this OT , i think all the Paypal refund issue could be ruled out if the seller have a proof of sending, or a tracking nº....
and this problem could happen in the same country the same way,to be abroad or not changes litlle i think.This is where feedback is important.
BTW, Italy has a very poor reputation about post office,i feel sorry for Italian ebayers that have to pay more than others ....
regards,
Fred.

[Max]

I never understood why some guys refuse to ship outside their country
The buyer pays shipping and takes responsability anyway, and the seller is loosing (a lot of) money that way.So what´s the point? Looks pretty stupid to me.
Fred.

Hi,
it seems so... but it isn't actually. The reason is fairly obvious: if the buyer takes responsibility for anything could happen during transport it will like you said, just stupidity.

But there's more: for example on ebay the customer that doesn't receive the stuff could start a procedure against the seller and it's kind of controversial action where ebay people try to put in communication seller and buyer... also recording all messages sent both ways, for any legal use they could have in future.

Now... the problem is that both ebay and paypal (that's common payment method on ebay) give that chance to the buyer to recover money if stuff doesn't arrive in a particular time interval (30days for paypal if I remember well and 45 for ebay... or the like). When the boundaries become near and buyer hasn't received stuff he could start the action by paypal and/or ebay and try to recover money that way.

The problem is that if the seller has actually shipped stuff with all cares required but stuff didn't arrive at destination cause of e.g. postal services problems of destination country or ...I don't know... customs etc the seller cannot actually do nothing, expecially if the shipment was without tracking number and the like... to demonstrate the shipment date etc but also if a shipment document exist... there's possibility that e.g. custom declaration was wrong: suppose you're shipping an MD and write "gift" on the custom declaration... and the value of MD is 5000$ but you wrote 50$ just to avoid other troubles to the buyer (like custom duties), but also from item return back to the source (in some country you cannot ship items like MDs), they could have troubles related to WTO rules violations also (though it's extremely rare case... cause WTO don't care much of individuals and their small business) and apply of a procedure by the originating customs in relationship with the fake custom declaration, if any...

All this could compromise feedback of seller if he refuse to refund money back in such odd situations... this sure will happen in the case of MD, not for other few expensive stuff, where seller would prefer refund buyer even without seller fault!

These odd situations make many people be scared of shipping abroad, even with an extensive, protective set of rules enstablished.

So they go with domestic only! And refuse anything abroad... even money from abroad!

Kind regards,
Max