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TGSL Tuning & troubleshooting
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Originally posted by Davor View PostYou must find points with low impedance to avoid loading your device with a long cable and low impedance.
Start with Tx, but make a 1:10 or so attenuator, just reverse the resistors as seen in http://www.ledametrix.com/oscope/
Next connect a scope (with 1:1 probe) to output of preamp, and re-do coil nulling.
The most important thing is to supply your device with batteries, as a PC PSUs are not famous for their isolation.
Working on battery power.
Špansko selo je kod mene - preamp output ? It's easy to say if you know
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Preamp, or preamplifier is a thing that follows after a RX coil. U101a, pin7 is the preamp output. The best point to stick your soundcard probe is at a resistor R27, as it is firmly on DC ground potential, and it's upper end has only AC component on it.
BTW, I might attend geokamp in mid June, see http://www.kresevski-citrin.com/inde...d/14-4-geokamp
Could be interesting
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Made new nulling and got RX coil to get 2.1mV from starting 150mV
BUT after that I can't stop detector from going beep beep ... 4x second
if I flex coil it stops little and starts in few seconds again... pots are not responsive
LF353 PIN7 soundcard probe capture
geocamp close to former gold mine... nice
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Originally posted by sdesic View PostMoved coils from that nulling point an it is working Ok again ... less depth but working
Don't fool yourself into thinking #1126 is OK. That looks like nothing but noise.
Fix your transmitter, and then you can worry about null.
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You are mostly interested in envelope of the signal, so you may increase a time base to 10ms, or even 100ms and it will give you a somewhat less confusing display. This is a nice display of a signal sampled near Nyquist frequency, and there is nothing you can do to make it better with the existing soundcard. It would improve if your sampling rate is 96k, but it is unlikely that your soundcard supports it.
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