[Esteban]

Regarding the ion detector for dual polarity, the both 4k7 resistence in base, one to negative load - reduces great the current, hope no motive for to think can burn the 3130.

Ok, in the Zahori, the 22 k controls the volume, note that in the original this is adjustable preset, no is fix in 22 k. So the volume is more high. Also you can up the 22 k, for example, to 47 k = more high volume. For to comprobe, you can ear the "hums" of the 4066 keys in the secondary (transformer) with earphones, but no connect yet any antenna, because in indoor is a "hell" (fluorescent lamps, cable, etc.). Adjusting the 10 k sens. pot. you can control the "hums" of the 4066 keys. The 10 k pot. put in the limit, in the start of the second stage audio circuit. This is a machine for indoor, far of electric lines and other interferences. So you put the most sensitive point with the 10 k of the Zahori. No synthetic clothes or plastic box for the instrument. I built in wood box (you can see in this same thread, page 2, the approximative model). Also Qiaozhi translate in English for all, in this same thread, the Zahori's text (0 views the both!) .


Of course, when you search with the 3 antennas instrument (indoor) you adjust with all the enviromental noise, internal ICs noise, 4066 "hums", etc. So over the level of the noise occurs the difference, this is the detection of the target. In some cases, noise is a reference wich put the "glitch" in delicate point, extremely sensitive. And the conductive buried target in the environment ups the microvolts in the antenna and sum. So, conductive items buried for long time has electrical field, no doubdt for me.


Don't try the 709 in this circuit, but the very high input impedance of the 3130 is the theme.

Also I redesign with 4047B as freq. generator and an only LM358. Works indoor, but I don't try in the field, yet.

Report? The only report I have of third part that found a gross heavy gold chain 1 m depth and 30 m far. Other person found antique woman comb carey and gold with gem stones, another found 4 gold coins, this same person found old wire for fences, entire roll! So, this mass of rolling wire has some thing... Is so impressive the signal, is difficult to center the objects.

The rest of the job is yours!

Here with the correct output:

http://www.mytempdir.com/707825