O.K. Esteban let's talk about Zahori for a while...
some remarks...:
- from your post"But in 1988 publish for positive and negative ions, looks that the zahori.
Article in Spanish. You can replace the plate by antenna."
Looking at the schematic you posted at the time i am not sure that 3130 will survive direct
connection to BC547 which at the same time provide plate polarisation!? Is this correct?
It will need some buffering and signal limitation at that point....
But, o.k. ...let's switch to the improved version you posted after that.
First instead headphones you put a cap and audio transformer at the same time you omited
scale. I do not think that output signal would be far enough to drive output transformer
and provide at least some usable tone. What you can hear is some "clicking" hum generated
from the 7555 due to poor filtering. About detection ....well, what we have here is a
wide range "detection" of noises and "airborne" hum , chopped by 7555 stage under very
strange, previously choosen, frequency rate!?
I am absolutelly sure that this device will produce some noise but not sure at all that
you can detect anything with it on longer range than 3-4 inches, and only if some
powerfull source of "signal" is placed nearby. The very same problems occurs with ivconic's
negative ion detector, although it is quite better design than zahori, at least it can
detect strong ionic field if nothing else.
O.K. I might be wrong considering this since i rely my remarks only on plain theory. I
never built zahori so far.
You made Zahori and i guess you do have some field experiences with it. Can you post here
exact reports from it?
"Hard head, RObert! Always I show you the path... electric field around conductive metals!
And the electric field can be detecable by the Zahori, with the corrects modifications.."
Thank you very much for "showing me the path"! Anyway....there is not any special electric
field around conductive metals to detect! It is a fact! Esspecially no such field around
burried metal, at all! There is for real an electrostatic field on the gnd surface and it
has for real very frequent changes, minute after minute. Those changes i guess you can
"detect" with zahori, maybe....maybe not...who knows?
"electric field around conductive metals" can be obtained only if that metal is in the area
covered by electromagnetic field generated by some source, that's how PI detectors do the job!
So it is not logical at all that you can use zahori and do the job is claimed to do. But
as i said, i never checked that in practice, i might be wrong....
I read this part again:
"We will describe how to assemble several components to construct an instrument that is able
to detect the variations in the electrical field, and indicate the ionic potential in the
immediate environment."
I cab beleive in that. But never mentioned any "conductive metals" at all! Only "variations
in the electrical field". It means that you can realy use zahori to trace changes across
some power line and simillar, and nothing else....
Further considerations are not important, device could work better or not - never mind.
The point is that zahori is not usable in this subject of metal detecting at all.
Sorry, but it is a truth! Besides i used so much 3130 and 3140 in my designs and i never
noticed such big difference among them at all. So far as i am concerned, the 709 would do
much better job than 3130 and 3140 in this design. Also some of newer rail to rail op-amps
could be much better solutions here. But what is the point!? To check electric field
variations you can do with some cheap "made in China" probes, you do not need to bug your
self with zahori at all!?
That's why i am using "obsolete" term here very often. I would like to see here some more
interesting project on that subject. I would post it if i had, but i do not yet.
I am not proponent and promoter of LRL, i am quite novice in that matter that's why i
provoked you to post here some more....
But, after all, it seems that you too, do not have any usefull project to post here.
Everything posted here man can assemble and check, than to beleive or not to beleive in
some claims. Otherwise all ends with an empty retorics.....
regards

P.S.
i hope this post is not offending you to much like in the past.....
ha,ha,ha...