Mean machine

[Ultimate_Haze]

Great.
So there is some kind of sampler there?
You get pretty good info about the target:size,depth,material!
I just cant wait winter to see this masterpiece busted.No matter that it will be hardly replicated.GP and all.

[ivconic]

I forgot to attach this draw. Maybe is not art, but it can illustrate what i ment in previous post...

[ivconic]

"...About silver plate mp3; you will hear strange behavior (much different) somewhere from the middle of mp3 file. That is because i turned it lateraly during swinging... Interesting change of behavior, that's why i recorded it in that manner.."

This is excellent example to understand better how eddy currents from item surface directly affects signal.

[ivconic]

Yes...;
most of the spitting you can hear at Fe key mp3. And most pleasant signal to me (subjective) is reaction on Silver plate..of course!
Possibly at other models too, but at Musketeer there is very significant difference between sound from speaker and sound from earphones.
Nothing can compare to sound from earphones. Sound from speaker is poor comparing to it. That's why is desirable to use earphones as often as
possible. Sound what you can hear in those mp3 files was recorded from speaker. But since mic was very close to Musketeer speaker i am noticing
very good simillarity to sound i used to hear using earphones....So..it is probably due enclosure acoustic and speaker features itself...
Use earphones whenever you can.

[ivconic]

Oh yes;
i forgot only...most important thing!

Item---------- Disc at 1st half of mp3----- Disc at 2nd half of mp3
************************************************** ******

-1e coin --------------- 4 -------------------------------- 4
-2cm coin ------------- 4 -------------------------------- 4
-fat brass washer --- 4 -------------------------------- 8
-Al disc --------------- 4 -------------------------------- 8
-Fe arrow (rusty) --- 4 -------------------------------- 8
-Al can ---------------- 4 ------------------------------- 8
-Cannon ball ---------- 4 ------------------------------- 8
-Fe key (rusty) ------- 4 ------------------------------- 8
-Silver plate ---------- 4 ------------------------------- 8

You will notice one item from photo is missing in this list. It is nail look like item. It was totally rejected in all cases.

About silver plate mp3; you will hear strange behavior (much different) somewhere from the middle of mp3 file. That is because i turned it lateraly during swinging... Interesting change of behavior, that's why i recorded it in that manner.

[ivconic]

Uhm... maybe is better, if you have time and an mp3 recorder, to capture that sounds (even better if on soil, during real search) and post here!

Cause I'm going crazy trying to understand the sound... adding spittings etc

So, the transitor issue was solved !? BC857C... fine! Very good!

Kind regards,
Max

Hey Max, it's been a while. Sorry i could'nt done it earlier.
Well...
Recording was done in my living room, right next to pc. Somehow i managed to put all togather and avoid much of interference.
Keep in mind that those recs were made under those conditions and so as i noticed md behavior is a bit different (not to much) than if it was done outdoor on soil.
I collected few items and made mp3 file upon each one. No need to explain more. I give here photos and mp3 files.
Oh...yes...need to explain a bit more. Coil was faced up and steady. I took item and by swinging on 30cm over , cm by cm closed to coil surface. So you will easilly notice differences. First few swings are slow and than goes faster as item reach coil surface.
When you listening cannon ball.mp3 dont be confused about sudden appearance of some background noise, it was damn car passed by my window!!!
Ok... that was all...ask if you have something else to ask...
Regards!

[Fred]

Even so...BC548 is NPN !?

good point!,

I alway see bc547/557 548/558 549/559 as equivalent pairs, so i didn´t even look at polarity
will be noce to compare in real world anyway...
Regards,
Fred.

[ivconic]

I agree.
Although...it would not be a problem to use 3g also. We can try 3g and later BC557c and see differences, if any (by observing signal on scope, by measuring drains...etc..etc)
Ok...TX doubts are solved, i guess.
Now...audio part is next. Relic Hawk has only earphones, Musketerer has earphone jack and speaker 8 ohms... Any difference in output stages? I dont think so, but i will check that also. But i am sure audio output transistor is BSR51, already checked and proved....so...BC517 will do the job also.

[Qiaozhi]

Very good point! That really could be right answer! Actually 3g is last in TX "chain" and i guess it was desirable to reduce power disipation as much as possible. Seems pretty logical.
So... what we gonna loose on performances if BC557c is used...in our handmades? I guess not much....yet!?
This need to be explored...

In a handmade clone I would think that the BC557 is a perfect replacement for the BC857, if you don't want to use SMDs.

[ivconic]

Very good point! That really could be right answer! Actually 3g is last in TX "chain" and i guess it was desirable to reduce power disipation as much as possible. Seems pretty logical.
So... what we gonna loose on performances if BC557c is used...in our handmades? I guess not much....yet!?
This need to be explored...

[Qiaozhi]

I also searched through several cross references....hmmm... According to what i saw; BC557c should be pretty good replacement???
But we already have one BC557c there on ocb?????
So....why oh why they put one conventional BC557c there and than put also BC857c ????? Why they dont used also BC557c if it can successfully replace BC857c????
Can anybody explain this? I do not understand this at all!
Maybe 3Gp (54) is not just ordinary BC857c....maybe have some speacial features?


Carl...Sean...you are having experiences in this. C'mon help here about this !

The BC857 is an SMD with a total power dissipation (Ptot) of 200mW, whereas the BC557 (TO-92F) has a Ptot of 500mW.

It looks like the designer was trying to use SMD components wherever possible, but a higher power device was required in this instance.

[ivconic]

I also searched through several cross references....hmmm... According to what i saw; BC557c should be pretty good replacement???
But we already have one BC557c there on ocb?????
So....why oh why they put one conventional BC557c there and than put also BC857c ????? Why they dont used also BC557c if it can successfully replace BC857c????
Can anybody explain this? I do not understand this at all!
Maybe 3Gp (54) is not just ordinary BC857c....maybe have some speacial features?


Carl...Sean...you are having experiences in this. C'mon help here about this !

[ivconic]

Even so...BC548 is NPN !?

[Fred]

* High current gain

* Low collector-emitter saturation voltage

* Low noise between 30 Hz and 15 kHz

Huh!!! It is not just "any" common transistor. Right now i am thinking about conventional (non smt) substitution.....for our future handmades...

BC548
Every manufacturer will claim they are selling the best component...actually the bc548 has more gain and more current , just less voltage:

http://www.philohome.com/sensors/gp2d12/gp2d12-datasheets/bc548.pdf

And about the collector-emitter saturation voltage, the´857 phillips datasheet shows variations that are so large, i think the ´548 is a good candidate for equivalent.
Maybe there is another important characteristic on the 857 ...

[ivconic]

Hi Ivconic
Great! a secret revealed !
I confirm this must be a BC857, very common one...
Here an excellent database for SMD´s :

http://tkb-4u.com/codes-and-markings/smd-codes-markings/database

And here the datasheet:

http://www.tkb-4u.com/SMDcode2/PDF_Data/BC856_BC857_BC858_Phi.pdf

Thanks!
Regards,
Fred.

* High current gain

* Low collector-emitter saturation voltage

* Low noise between 30 Hz and 15 kHz

Huh!!! It is not just "any" common transistor. Right now i am thinking about conventional (non smt) substitution.....for our future handmades...