Quote:
Originally Posted by FrancoItaly
Hi Dubulumach,
What you say is interesting but it is beyond my knowledge. But as I see it, it is not necessary to elaborate in this direction, I leave this task to others, certainly more competent than me. My lrl works in the range of 2.5Mhz to 10Mhz frequencies and with an input frequency in the 80Mhz - 120Mhz range. In this frequency range there is no particular that allows a greater sensitivity or some discrimination. The version with CD4046 was designed to achieve some discrimination and in the original (unpublished) version the phase changes were compared with the amplitude variations, but I did not get positive results and so I decided to post only the part related to the phase changes. I have always recommended the version with the quartz oscillator because it is easier to make and the sensitivity is practically the same. Finally I want to add that it is not practical to increase the sensitivity too much otherwise the compass effect appears and this makes the tool very difficult to use.
Best Regards.
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Thank you FrancoItaly for detailed explnation.
I think your idea is a very good but the hardware need some modifications,
There are many things which should be tried, for example IR pcb attached to your LRL, optical filters, new antenna design etc, etc.
I've made several LRLs from you, and i have also problems like SKY/GROUND effect, in fact influience of local vriations of earth magnetic field,but the main probem are false signals.
I havent made digging snapshoots but i am telling a truth i found a waste amounts of underground ferrite objects and what is very interesting all of them have bneen at last stage of corrosion.
To avoid this we need to modify input front end circuit, like puting in parallel with L1 small variable capacitor, lower overal gain of preamplifier stages, put ferrous-filter (100pF in series with 1Meg or bigger resistor, better same value potenciometer), try magnetic coupling stimulus instead electric couling like is yours, lowering stiimulus freq. with LF variable signal gnerator from couple of Hz to about 100KHz, use full metal case, with aluminium handle, work with both haand, use silver-mica capacitors for whole device etc. etc.
Last year i've got very storng signals frm the acient roman's site from about 80 meter distance with telescopic antenna lenght about 1,5m. Next grediometer measurement (gradient type) had shown something is at HotSpot but the depth was over 5 meter, and what is bigest problem for me and my partner, the site is only 50m from the international highway. So i was quit, because toio many risk.
In any way thank you for your ideas and your honesty help allof us.
ps: My new idea is, lowering gain of preamplifier and use diodes in combination with low-offset OP preamplifier to rise the "halo-signals" from the background noise. With diodes we coud demodulate, "Halo" modulated carrrier in hundreds of mV range, with small OP trick we can run demodulation in mV or even uV range, very close to noise floor of components. It is simple and effective, just use those diodes in feeback loop of some good CMOS OP, while grounding non-inverting input at common via some bigger capacitor. Anyone can draw schematic..
Best Regards
Dubulumach