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#1
04-18-2011, 12:27 AM
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PD Discussions
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I remember Esteban told he found iron fragments from old fence when test his PD. He told to avoid this sensitivity to rusty iron need to increase the resonating frequency. This will make the PD less sensitive to iron,i supose you found the iron with your PD prototype. Regards 
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#2
04-18-2011, 05:36 AM
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Thanks for your attention . Yes, I remember what's Esteban said . But my real LRL wasn't Alonso PD clone . It is other PD……… About my Alonso clone PD , it is working ,detect 17 inch computer CRT screen from 1.5 Meter !!!!!. It is working very stable on the workbench , but problem when test on the ground , it is instability , must be re tune it And this is problem . also I think there are this instability in original Alonso PD what is your opinion?????? Best regards.
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#4
04-18-2011, 09:06 AM
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Hi Geo Please more explain……. For how long time duration stable on over ground???? My opinion is period of retune while search area. With your set null please say, what is detection range for 1.5 volt battery Short circuit ?, what is detection range from TV ? Best regards.
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#5
04-18-2011, 09:28 AM
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Probably you put device on OFF position?
__________________
Global capital is ruining your life? You have right to self-defence!
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#7
04-18-2011, 11:37 AM
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Hi aft. About stability over the ground......more than 15minutes without retuning. The short circuit test is not good for me. When PD works as double detector (omega + passive receiver) it detects the battery spark only from 20...30 cm. When it is at ferrite mode then it detects the battery spark from 90...95 cm and the TV-on from 5meters. But this is not a test that means anything...... Regards
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Geo
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#8
04-18-2011, 12:26 PM
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Other question , When MD with ferrite work , what is detection range for 1 euro coin? Best regards.
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#9
04-18-2011, 02:40 PM
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i sent to you a PM, please see that and reply to me. all the best mehdi
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#10
04-18-2011, 03:11 PM
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Regards
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Geo
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#11
04-18-2011, 03:45 PM
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Thank you Geo , yes, if we set TX/RX coils as un tune mode , We reach to extra stability , but big problem here ,lose high sensitivity. Therefore it didn't act as LRL !!!!!!! Best regards.
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#13
04-19-2011, 02:47 AM
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Stability and high sensitivity relation together is reverse, when more stable , lose sensitivity and if we need high sensitivity , also we having instability . Art is here " design high sensitivity with stability " I am sure also there is instability at original Alonso PD. I thinking solve problem in other way …….. Best regards.
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#14
04-19-2011, 05:23 AM
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Hi Aft. Oscilator is very stable. If you connect a frequency counter (first you must modify the oscilator a little so to give sine waveform) you will see that the drift is about 10Hz in 30 minutes. The main reason of instability is the bad power supply at some stages. I connected a 6 1/2 digits multimeter to understand the problem. Original Heathkit MD was very instability as Qiaozhi said. Regards
__________________
Geo
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#15
04-19-2011, 05:47 AM
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Yes, thank you for your guide , I know very well heatkit GD 348 problems I never see and never work with original heatkit GD 348 . all of my knowledge From my clone circuit . I did more practical work in laboratory with it . This is strange for me why designer ALONSO or ……. Use this type detector . What theory and philosophy behind.?????? Instability at GD348 not produced by frequency drift, not very Important oscillator frequency drift , This type detector base on amplitude changing .   Best regards.
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#16
04-19-2011, 07:29 AM
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__________________
Global capital is ruining your life? You have right to self-defence!
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#17
04-19-2011, 11:53 AM
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Hi aft. I don't know why Alonso prefered this schema. It is sure that the GD348 is more sensitive than every bfo and has a very very strong oscillator. Now about instability..... i had the same problems for long time. Now i solved them and it is very stable. Try to make it stable and after it you will see that it is a good detector. Regards 
__________________
Geo
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#18
04-21-2011, 03:40 AM
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Thanking  , I will try build it more stable .Best regards.
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#21
04-21-2011, 06:21 AM
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The philosopy of using a heathkit detector is common with Alonso and other builders of LRLs which are modified metal detectors. The reason to use this design is because it uses all transistors, with no IC in the circuit. The early transistor designs were simple and they did not have internal filters built into them like ICs do. They wanted pure transistors so none of the signal they receive will be lost in a filter or compensating circuit like they are in a design with op amps. They like the early circuits also because these detectors detect all of the signal. They hear very weak signals that modern detectors do not because modern detectors filtered out weak noise signals. But this same noise is the problem with old detectors, They are unstable partly because of the excessive noises they pick up from stray RF, EMI and ground capacitance or other sources. But this is the sensitivity that LRL experimenters are looking for to find thir treasure signal. This Heathkit detection design is more sensitive than modern VLF circuits, or even BFO designs. When you use 1970 electronic designs you do not have modern methods to keep the circuit stable. Take a look below, and you will see the most unstable part of the GD348 is the audio amplifier which must bring the weak detector signal to a usable signal. We see they put in a pair of diodes to act as temperature compensation, and a zener diode to keep the voltage constant. You may be aware there are better modern methods to keep the supply voltage for this transistor from drifting. This is one place where you can solve some instability at this critical part of the circuit. But keep in mind the Alonso PD made modifications to the GD348 detector, The speaker was replaced with a beeps generator, where some of the output signal is mixed with the ferrite signal. But more important, there were big changes made in the front end by the omega coil and the resistor network that sends part if the TX signal into the RX coil. You cannot expect the Alonso circuit to work the same as the GD348 because the beginning signals at the omega RX coil are different in level and in the amount of feedback. In any case, assuming you can get reasonably similar circuit performance as a GD348, the biggest problem I see in most PD designs is when builders mount their circuit boards too close to the coils. If you look closely at the Alonso design, he took measures to keep the coils separated from the control box, which prevented the circuit from being detected as treasure metal. But it is also important to keep the boards separated from the coils so the coils will not induce eddy currents in the early stages of the RX that can make the circuit impossible to work. (Remember the GD348 had the coil at the end of a shaft separated from the controls, and only a small board for coil-related parts at the omega coils). See diagram below. And also see in zip file for original GD348 schematic. You can compare this schematic to your PD and see how much it is different at the end by the coils. Best wishes, J_P
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#22
04-21-2011, 06:56 AM
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Hi J_Player
Thanking for your attention and thanking for your help , your are fine engineer , you pointed to points which also I thinking about it !!!!!! I must be use reference zener diode( instead ordinary zener diode) , other instability was Darlington transistors at output ( see PD circuit-not original heatkit circuit) . My built and modified MD vas very stable on workbench !!!!!!!!!!!! . it can detect 17 inch computer monitor from 1.5 meter easy in workstation . !!!! but problem will begin When begin moving PD in search aria!!!!!! ., may be must be Not tuned for very fine null ( null tuned very fine) but when a little out of fine null . sensitivity is fall down and didn’t act as LRL maybe this is sky ground effect but Coil far from ground !!!!! . crux is here, be stable in high sensitivity . I remember Qiaozhi ideas , super fine , super sensitive detector but point here with stability . Best regards.
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#23
04-21-2011, 07:27 AM
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Hi Qiaozhi
You are after Carl leader of this forum . excuse me , our dissection was long because as this is zahori thread, May be better will begin other thread about Alonso or ….X designer ofPD problems . But I cannot copy and paste all messages about heatkit GD 348 detectors Best regards.
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!!!!!!!!! ., I believe there are phenomenon and energy filed around long buried metals now . 
Linear Mode
