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Topics - woody

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61
General Discussion / Can a modded GPX beat the SDC2300 and GPZ7000?
« on: October 15, 2015, 06:53:41 pm »
Our latest testing with the Sunbury metal detecting club shows that a modded GPX4500 has greater detection depth than the GPZ7000,  that is not all, the GPZ7000 had a 14" coil but the modded GPX4500 had an 8"   yes only 8 inch mono coil.  The target tested was a natural 3 ounce gold nugget.  The GPX4500 in high frequency modded mode eats the SDC2300 on small gold at greater depth. The front end dual channel tracking variable gain mod and the variable frequency mods are opening up old detected ground and is producing nuggets missed by other detectors. 

62
General Discussion / About time , new patents granted
« on: October 15, 2015, 06:47:01 pm »
Been waiting for a long time to get this one done.

http://patents.justia.com/inventor/peter-robert-woodland

63
Well its been an interesting time, I've purchased a lot of new test equipment including low frequency FFT analysers, super fast 400 Mhz Oscilloscope, Frequency/function generators, Low frequency spectrum analyser, low frequency network analyser, differential noise analyser and 5 Msp digital oscilloscope. The most cutting edge circuitry is being worked on to improve all gp and gpx detector several orders of magnitude.    We have a hell of a lot of improvements coming for the next detecting season.  Input noise is now 6 decibels lower and this is a huge improvement on existing stock standard detectors.

64
All fixed,,,, Thanks Jason.

65
Lets look at a GPX5000 and see what some changes to the operating parameters does to the detector.
Same is applicable to SD2100 SD2200 GP Extreme GP 3000 GP 3500 GPX 4000 GPX 4500 GPX 4800 GPX 5000

https://www.youtube.com/watch?v=T0-fJyAOyIM

66
Technical / New GPX-4500 GPX-5000 Mods...
« on: February 15, 2015, 12:13:01 am »
Looks like we can get  40% plus on big targets with our newest mods... 40% also on small Gold.  Just need some field testing done...

This applicable to all GPX GP and SD2100 SD2200  detectors.

More information to be released via the news subsrciption on the home page.

67
Soon to be available is an upgrade that will allow GP and GPX series detectors to detect small gold similar to the capabilities of the SDC2300.

68
The Class D amplifier was a great idea but the problem was increased interference when using a large coil, Class A B amplifiers that use common amplifier topography generate high levels of hiss type background noise and this is particularly bad using metal detectors with low threshold volume.  We came up with a high quality class B design that has next to zero hiss and generates no extra noise. It only draws 5 milli amps with no input and thus has no noticeable effect on battery drain. This is a winner, to be released soon.

69
General Discussion / We have a Facebook page
« on: August 09, 2014, 03:16:01 pm »
We have a Facebook page/forum if you want to join, it's a closed group so if you want to post and stay hidden from the public gaze then come and join  http://www.facebook.com/groups/bestmetaldetecting  There are 2666 members..

70
New Detector accessories / Interference filter
« on: August 09, 2014, 07:55:27 am »
I just finished a video on the interference filter i have been developing over the last few months.
https://www.youtube.com/watch?v=oqnhEW7yWUk

71
Technical / Making the SD2000 SD2100 and SD2200 more quiet.
« on: August 06, 2014, 11:28:37 am »
These detectors are getting on on in years but they all are very good detectors, all can be modded up and detect in most cases as good as the newest detectors that are so very expensive.
The most simple fix is replacing the 150uh inductor in the switching power supply. Over the years the capacitors dry out and lose their electrolyte, this lack of capacitance causes circuit instability
and thus a noisy detector. Replacing the 150 uh inductor in the power supply with a physically  larger shielded type with less inductance of 100 uh does a number of things. First is raises the self resonant
switching frequency, this causes less noise as the internal power supply is more smooth in output. The higher the frequency the less ripple and those dried out caps can filter out the noise as the switching transitions
are less in amplitude. Also the detector starts faster, to me this because the existing inductor suffers ferromagnetic collapse at high start up inrush currents.  The supply actually runs cooler.

72
Watch this space, no one else can upgrade the F1A4 detectors to our new specifications... These are great for finding Quartz Reef Gold.

73
We have been busy. Have a series of 7 new upgrades coming out that will make these old detectors some of the deepest detectors available if not the deepest for large Gold and Treasure.

75
After testing the input stages on various detector I have found that many of the AD797 opamps with a spec sheet indication of 25mv DC offset is not the case when measured in some detectors.
Offset voltages in excess of 100mv are quite common.  Adding a potentiometer and trimming the Offset after 15 minutes run time to DC makes for a much more stable and quieter detector. As the first stages are DC coupled, reducing the Offset voltage makes for a much more behaved quieter detector. Frequency compensation can also be carried out to reduce Radio Frequency interference without degrading the low frequency slew rate or settling time of the opamp. 

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